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International Review of Electrical Engineering  Vol. 7 N. 4-- Part A

International Review of Electrical Engineering  Vol. 7 N. 4-- Part B


go to top     International Review of Electrical Engineering - August 2012 (Vol. 7 N. 4) - Papers Part A



go to top      International Review of Electrical Engineering - August 2012 (Vol. 7 N. 4) - Papers Part B







International Review of Electrical Engineering - Papers- Part A



go to top  Single-Stage Grid Connected PV Inverter with Active and Reactive Power Flow Control via PSO-PR Based Current Controlled SVPWM
         by A. Damiano, G. Gatto, I. Marongiu, S. Meo, A. Perfetto, A. Serpi

        Vol. 7. n. 4, pp. 4647-4654


Abstract - The paper deals with a high performance single-stage three phase inverter for grid connected PV systems. In the paper a current control algorithm is developed so that the proposed configuration can convert the solar dc power into high quality ac power while tracking the maximum power from the PV array, ensuring active and reactive power flow control, higher efficiency, low cost and compact size. Moreover total harmonic distortion of the current fed into the grid is very low with respect to the IEEE standard. In the paper a full analysis of the proposed system is presented and numerical results for different reference values of active and reactive power have been shown and discussed.

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Keywords: Grid-Connected PV Inverter, MPPT, Power Flow Control, Current Regulator.



go to top  The Identification of AC-DC Power System Parameters Using an Adaptive Tabu Search Technique
         by T. Sopapirm, K-N. Areerak, K-L. Areerak

        Vol. 7. n. 4, pp. 4655-4662


Abstract - Power electronic converters are widely used in many applications, especially AC-DC power systems. The DC-link filters are normally included in such power systems. For some applications, accurate DC-link filter parameters are very important for the system analysis and design. According to the measurement errors and a large variation in a capacitor value, the parameter identification is needed to provide the usable parameter. Therefore, the paper presents the identification of DC-link filter parameters using the adaptive tabu search technique. The experimental results from the testing rig and the averaging model of the system are used in the searching process. The identification results show that the accurate DC-link filter parameters including line parameters on the AC side can be easily obtained via the proposed method. Moreover, the resulting parameters are very useful for a stability analysis of the power electronic systems due to a constant power load.

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Keywords: System Identification, DC-Link Filter, Adaptive Tabu Search, Three-Phase Rectifier, Averaging Model, DQ Method.


go to top  Simple Three-Level Neutral Point Potential Balance Control Scheme Based on SPWM
         by Bo Gong, Shanmei Cheng, Kai Cai, Yi Qin

        Vol. 7. n. 4, pp. 4663-4671


Abstract - To address the neutral point potential balance problem of the diode clamped three-level inverter, this paper analyzes the causes of unbalanced neutral point potential and studies the impact of the carrier's amplitude on the neutral point potential. A simple neutral point potential control scheme using carrier amplitude-scaled sinusoidal pulse width modulation (CAS-SPWM), which only requires detection of the neutral point voltage, is proposed. A closed-loop controller with CAS-SPWM is used to regulate the neutral point potential, which is controlled by scaling the amplitude of the carriers. The same effect can also be achieved by an equivalent transformation of the modulation wave. The proposed modulation wave control mode does not change the carriers, thereby allowing the scheme to be applied easily using the digital control system. The modulation wave control mode is another way of realizing the CAS-SPWM method. It can maintain the neutral point potential balance by changing the modulation waves. The validity of the modulation scheme is verified on a digital signal processor (DSP) -based diode clamped three-level inverter platform using a CPLD to realize the PWM extension interface.

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Keywords: Three-Level Inverter, Neutral Point Potential, Amplitude-Scaled Carrier, SPWM.



go to top  Design of Energy Recovery Power Battery Pack Testing System
         by Bo Long, Zang Xian, Shin Teak Lim, Kil To Chong
        Vol. 7. n. 4, pp. 4672-4683


Abstract - This paper proposes a special power circuit topology and its corresponding control strategy for an energy recovery power battery pack testing system (PBPTS) for electric vehicles. Firstly, the working principle and the related parameter design for the proposed scheme are defined. Secondly, the control strategy of the composite power converter for the PBPTS is described in detail. The improved control includes a highly accurate current closed loop with a non-linear current controller, and an active power reference for the inverter is provided by the result of multiplication between the voltage and current on the dc-bus. Simulations and experimental results demonstrate that the proposed scheme satisfies the requirement for power battery pack testing with large, wide-range currents which could recover the discharging energy to the power grid with high efficiency. The proposed scheme could be used in evaluating the performance of power battery packs for electric vehicles.

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Keywords: Active Power, Composite Power Converter, Energy Recovery.


go to top  A Novel Reference Current Estimation Schema for Active Power Filters without Synchronization Signal
         by M. Cakir

        Vol. 7. n. 4, pp. 4684-4696


Abstract - In this paper a novel synchronization method is proposed to obtain a reference signal for active power filters (APF), which is used to determine the fundamental component of the load current in-phase with the mains voltage, without any signal measurement for synchronization. The principle idea of this paper is based on the proposition that “the required minimum value of the mains current is the value at which the reactive power becomes zero”. Therefore, the proposed reference signal extraction algorithm uses only the mains current. It is based on artificial neural networks (ANN) and when compared to the alternative methods, the proposed method comes forward with its simplicity in terms of hardware and software. In harmonic component extraction stage, an adaptive filter structure is used. Instead of common least mean squares (LMS) method, averaged least mean squares (A-LMS) method, which is generated by adding a moving average filter (MAF) block to the LMS algorithm, is preferred because it allows faster and more accurate determination of the fundamental harmonic component. A prototype APF with 3-KVA rated power is built to verify the proposed method. It uses only mains current and dc link voltage measurements. The results verified the successful performance of the proposed method in APF operation.

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Keywords: Active Filters, Adaptive Filters, Power Quality, Synchronization.


go to top  Voltage Balance Modeling in Single-Leg Flying Capacitor Multicell Converters Employing a Balance Booster Circuit
         by Saeedeh Dargahi, Mostafa Abarzadeh, Arash Khoshkbar Sadigh, Vahid Dargahi

        Vol. 7. n. 4, pp. 4697-4704


Abstract - This paper provides a mathematical model for voltage natural balancing process in single-leg flying capacitor multicell converters by taking into account the balance booster circuit effect. The analysis leads to state-space model of the converter. This analytic model of the flying capacitor multicell converters can be utilized to investigate the start-up and steady states of flying capacitor voltages. To provide verification, numeric results pertaining to a single-leg capacitor-clamped multicell converter’s analytic model are presented in different cases and compared against simulation results. Moreover experimental results taken from a laboratory prototype are also presented. An excellent match between experimental and numeric results confirms the validity of the proposed analytic model for the single-leg flying capacitor multicell converters.

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Keywords: Single-leg Flying Capacitor Multicell Converter, Self-Balancing, Voltage Balance Booster Circuit, Numeric Approach.


go to top Rigorous Choice of Optimal Isolated DC-DC Converter Architectures Using Response Surface Method
         by C. Versèle, O. Deblecker, J. Lobry

        Vol. 7. n. 4, pp. 4705-4713


Abstract - This paper proposes a methodology to help the designers to choose the best-suited isolated dc-dc converter topology for given specifications. To do so, a response surface method (RSM) approach is used in combination with a multiobjective optimal design tool dedicated to such power converters and using genetic algorithms. So the response surfaces are computed based on optimized power converters. Two factors are studied, viz. the converter input voltage and output power, whereas two response variables are considered, viz. the power loss and the weight of the converter. Moreover, the ranges of these factors are, respectively, chosen between 100 V to 2 kV as well as 1 kW to 250 kW. It should also be noticed that the experimental domain defined by the two factors is divided into three zones to perform the experiments and that five isolated dc-dc converter topologies are considered, viz. the flyback, forward, push-pull, half-bridge (HB) and full-bridge (FB) converters. The results show that the best-suited converter depends on the specifications and, also, that the HB and FB converters appear as well-suited topologies, whatever the zone of interest.

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Keywords: Response Surface Method, Switch-Mode Power Supply, Genetic Algorithm.


go to top  A New ZVS Nonisolated Bidirectional DC-DC Converter
         by N. Asadi Madiseh, M. Delshad

        Vol. 7. n. 4, pp. 4714-4723


Abstract - In this paper, a new nonisolated bidirectional buck–boost dc–dc converter is introduced. In the proposed converter a simple auxiliary circuit consisting of an auxiliary inductor and a coupled winding to main inductor without any extra switch is used. This circuit provides zero voltage switching (ZVS) condition for switches and eliminates the reverse recovery problem of the body diodes. Moreover, this converter is controlled by pulse width modulation (PWM) which its implementation is simple. On the other hand, the switches of proposed converter are switched complementary together and thereby separate derive circuit is not necessary. The experimental and simulation results of the proposed bidirectional converter are given to confirm the theoretical analysis.

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Keywords: Bidirectional Dc–Dc Converter (BDC), Pulse Width Modulation (PWM), Zero- Voltage Switching (ZVS), Buck-Boost, Nonisolated.


go to top  Interleaved Resonant Flyback Converter with ZVZCS Operation
         by Hyun-Lark Do

        Vol. 7. n. 4, pp. 4724-4730


Abstract - An interleaved resonant flyback converter with zero-voltage-zero-current-switching (ZVZCS) operation is proposed. The proposed converter consists of two identical resonant flyback converters. It features zero-voltage-switching (ZVS) operation of active switches and zero-current-switching (ZCS) operation of output rectifying diodes. Consequently, the reverse-recovery loss on the output rectifying diodes is significantly reduced. Moreover, ZVZCS characteristic of the proposed converter reduces the switching losses and raises the overall efficiency. Experimental results based on a 90 W (120V / 0.75A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.

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Keywords: Interleaved Converter, Flyback Converter, Zero Voltage Switching, Zero Current Switching.



go to top   Interleaved Zero-voltage-switching Boost Converter with a Coupled Inductor
         by Hyun-Lark Do

        Vol. 7. n. 4, pp. 4731-4738


Abstract - This paper proposes an interleaved zero-voltage-switching (ZVS) boost converter with a coupled inductor. A coupled inductor and the interleaving technique are utilized to reduce the ripple component of the input current.
An auxiliary inductor and a dc blocking capacitor between two boost converter cells provide a zero-voltage-switching condition for two power switches. Due to the soft-switching characteristic of the proposed converter, the switching loss is reduced and the overall efficiency is improved. Experimental results obtained on a 100W prototype are discussed.

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Keywords: Boost Converter, Soft-Switching, Interleaving, Zero-Voltage-Switching, Coupled Inductor.



go to top Comparison of Updated Soft Switched Full Bridge Converter Using Voltage – Doubler – Type Rectifier with Existing Techniques
         by V. Delbin Jelaja, Dr. M. Rajaram, B.E, M.E.
        Vol. 7. n. 4, pp. 4739-4745


Abstract - An updated soft switched full bridge converter with voltage doubler type rectifier is proposed to reduce the circulating loss in primary and the voltage stress in secondary. The conventional converter is having the drawbacks such as circulating loss in the primary, voltage spike across the rectifier diode. Also the conventional system is using large output inductor in the secondary side; because of this core loss occurs. In this paper we introduce a new technique to overcome the above said drawbacks. Without an auxiliary circuit, zero – voltage switching (for leading - leg switches) and zero – current switching (for lagging – leg switches) are achieved in the entire operating range, which reduces the circulating loss in the primary side. To implement the converter without an additional inductor, the leakage inductance of the transformer is utilized as the resonant inductor. The resonance between the leakage inductance of the transformer and the rectifier capacitor can reduce the current stresses of the rectifier diodes and the conduction losses. The clamp diode is used to clamp the voltage spike across the rectifier diode which reduces the voltage stress of the rectifier diode. Due to its many advantages this converter is attractive for high voltage and high power applications. The analysis and design considerations of the proposed converter are presented. The simulation results confirm efficiency above 98% which is 3% to 5% more than the conventional converters.

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Keywords: Phase Shift Full Bridge (PSFB) Converter, Voltage – Doubler – Type Rectifier, Zero – Voltage and Zero – Current Switching (ZVZCS).


go to top   Active Motor Terminal Overvoltage Suppression Method for Parallel Inverters with Output Inductors
         by Juhamatti Korhonen, Toni Itkonen, Juha-Pekka Ström, Juho Tyster, Pertti Silventoinen

        Vol. 7. n. 4, pp. 4746-4753


Abstract - Premature motor insulation failures have been reported to occur as a result of switching operation transients in inverter-fed motor drives. A parallel two-level voltage source inverter topology with output inductors and a new modulation approach are introduced to reduce the harmful overvoltage. The output inductors are usually used to suppress the circulating currents between the inverters, but now they are also used to provide a third output voltage level for each phase. The inductor size can be determined by the desired voltage rise time. A modulation method that mitigates the motor terminal overvoltage and balances the load currents between the parallel inverters is developed. The method is verified by experimental results with industrial frequency converters.

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Keywords: AC Motor Protection, Industrial Power System Transients, AC Motor Drives.



go to top  Walsh Function Based PWM AC Chopper Voltage Controller
         by M. Kale

        Vol. 7. n. 4, pp. 4754-4760


Abstract - This paper presents a selective harmonic elimination PWM AC chopper technique based on the Walsh function. Selective harmonic elimination technique calculated by the Fourier series involves solution of nonlinear transcendental equations. The switching angles of PWM AC chopper are calculated by solving linear algebraic equations obtained by the Walsh function approach in order to accurately cancel selected harmonic components of load voltage. Employing the proposed method, the selected harmonics of output voltage are eliminated and hence harmonic contents together with magnitude of output voltage can be adjusted in a wide range. In the experimental implementation, a capacitor-run single phase induction motor is driven by the proposed the Walsh function based PWM AC chopper. Numerical simulations and experimental results demonstrate the performance and feasibility of the proposed method.

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Keywords: PWM AC Chopper, Selective Harmonic Elimination (SHE), Walsh Function.


go to top   Asymmetrical Multilevel Inverter Topology with Reduced Number of Switches
         by Rokan Ali Ahmed, Saad Mekhilef, Hew Wooi Ping

        Vol. 7. n. 4, pp. 4761-4767


Abstract - A new asymmetrical multilevel inverter topology with reduced number of power switches is introduced in this paper. The installation area, voltage standing on each switch, converter cost and losses are also taken into consideration in this design. Further, operating principles and switching functions are analyzed. A comparative study between the new design and conventional inverters is also conducted to highlight the advantages of the proposed topology. Simulation results are provided for seven level of the asymmetrical multilevel inverter. A prototype of the designed inverter is manufactured and experimental results are realized.

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Keywords: Symmetrical Multilevel Inverter, Peak Inverse Voltage (PIV), Total Harmonic Distortion (THD), Voltage Drop.



go to topgo to top  Minimum Error Switching Strategy for Matrix Converter with Input Current Control
         by M. Senthil Kumaran, R.Siddharth, Ranganath Muthu

        Vol. 7. n. 4, pp. 4768-4775


Abstract - This paper introduces a new switching strategy for Matrix Converter (MC), the Minimum Error Switching Strategy (MESS) that implements a modified hysteresis based control technique. The technique limits the switching time to produce switching pulses of constant width. The decoupled indirect-space vectors of the MC are used for input current control and output voltage control. Switching vectors are selected based on the minimum computed voltage error and minimum computed current error over every sampling period. Important features of the technique are the constant pulse width switching leading to simplified modulation, uniformly distributed switching stresses over an output cycle and inherent mitigating effects of unbalance at the input. The technique proves to be more efficient in offering superior input and output current spectrums for higher switching frequency. In this paper, under distorted input voltage conditions, behavior of the MC controlled by MESS is analyzed. The proposed PWM algorithm is verified by MATLAB simulation and hardware experimentation on a laboratory prototype and results obtained are satisfactory.

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Keywords: Matrix Converter, Unbalanced Input, Over-Modulation Index, Error Compensation.


go to topgo to top  Performance Analysis of Three-phase Parallel AC/DC Converters
         by Siti Rohani S. Raihan, Nasrudin Abd. Rahim

        Vol. 7. n. 4, pp. 4776-4784


Abstract - Three-phase buck rectifiers are connected as parallel systems to improve the output power, efficiency, and total harmonic distortion (THD). A simple digital PI-control has been implemented to minimize the circulating current due to the unbalanced DC-bus currents generated by each rectifier. In addition, the parallel systems are connected with boost-SEPIC (Single-Ended Primary Inductor Converter) at the output stage for comparison with the performance of single converter system. The proposed converter yielded near-unity power factor, and higher efficiency compared to single converter system. Selected results are validated by simulation and experiment.

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Keywords: Rectifier, Parallel Converters, Pulse-Width Modulation, Boost, SEPIC.


go to topgo to top  Switching Frequency Modulation for EMI Reduction in Flyback Converter Using FPGA Implementation
         by K. R. Aravind Britto, K. Baskaran, R. Vimala

        Vol. 7. n. 4, pp. 4785-4792


Abstract - This paper provides a modeling approach for conducted Electro-Magnetic Interference (EMI) in Switching Power Converters (SPC). Among the variety of switched-mode power converters, the flyback converter is the favorite choice for low power application. Switching power converters are the sources of noise for sensitive circuits. Converters should comply with Electro-Magnetic Compatibility (EMC) rules so that the EMI caused by switching cannot interfere with the normal operation of adjacent circuits and also the converter itself. The produced interference can be in the form of conduction or radiation. In this paper, some techniques are used in switching converters to suppress EMI with an emphasis on the conduction form. EMI analysis and evaluation of a conventional flyback converter is achieved by simulation and experimental results. In addition to evaluating some EMI suppression techniques, the main objective of this paper is to improve EMC in the design stage. The increasing performance and cost reduction of Field-Programmable Gate Array (FPGA) technology have made the application of these schemes possible in this field. Then, the proposed schemes are designed and implemented using an FPGA-based controller.

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Keywords: Electro-Magnetic Interference, Electro-Magnetic Compatibility, Switching Power Converter, Field Programmable Gate Arrays.



go to top   An EMI Modelling of Heat Sinks for SMPS Applications
         by A. Damiano, G. Gatto, I. Marongiu, S. Meo, A. Perfetto, A. Serpi

        Vol. 7. n. 4, pp. 4793-4799


Abstract - An EMI modelling of heat sinks employed in Switching Mode Power Supplies (SMPSs) is presented in this paper. In fact, the capacitive coupling between electronic power devices and their heat sinks generally lead to impulsive current circulation in the latter, making them able to generate conducted electromagnetic noise and/or to emit as antennas. Such electromagnetic noise may give rise to the incorrect electronic circuits and control system operations. Hence, the proposed heat sinks model is developed in order to evaluate these effects, aiming to be an useful tool in order to avoid system faults and to guarantee the compliance to EMC standards. In particular, the proposed model allows the achievement of the resonance frequency of a heat sink in a closed analytical form. The results obtained by employing the proposed modelling procedure is properly compared with those achieved by means of finite element investigations, highlighting the effectiveness of the proposed method. This is also corroborated by the experimental studies carried out in an EMC laboratory.

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Keywords: Heat Sink, Electromagnetic Capacitive Coupling, Switching Mode Power Supplies.



go to top Stator Winding Fault Detection in Induction Motors Using Wiener Filter
         by R. Abbasi, M. Ghazal, M. G. Kazemi

        Vol. 7. n. 4, pp. 4800-4807


Abstract - Stator winding fault is the most important electrical failure in induction motors that commonly happens in all fields of industries. The major problem is to extract stator winding fault signature from stator currents in current-based monitoring approaches. Usually, there is a primary unbalancing in stator circuit of induction motors and source voltages that must be distinguished from stator winding fault signatures. Hence, in this paper, a Wiener Filter method has been proposed for estimating and removing useless components from stator currents in order to detect stator winding fault with high reliability. Since the Park’s vector modulus is sensitive to abnormality in three-phase stator currents, it will be used for detection purposes. Finally, the validation of proposed method will be verified by experimental data from a 5-horespower induction motor.

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Keywords: Induction Motors, Wiener Filter, Stator Winding Fault Detection, Park’s Vector Modulus.


go to top  A New Method for Parameters Identification of Permanent Magnet Synchronous Machines
         by Mohsen Hosseini, Nima F. Ershad, Javad S. Moghani

        Vol. 7. n. 4, pp. 4808-4813


Abstract - This paper presents a new method for obtaining equivalent circuit parameters of a permanent magnet synchronous machine. The new method needs four tests; one of them is no-load test and the others are loading tests. Test results are gathered in a set of three non-linear equations. By solving this set of three equations, equivalent circuit parameters of the permanent magnet synchronous machine are found. A typical solid rotor permanent magnet machine is chosen as a case study to examine the new method. Four tests are done by finite element transient analysis as well as by experiment on the prototyped machine. Theoretical results are in good agreement with test results. It is shown that the new method is easy to implement and is accurate.
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Keywords: Equivalent Circuit Parameters, Finite Element Method, Permanent Magnet Machine, Transient.



go to top   A Step-Up Converter Based on Charge Pump and Dual Boost
         by K. I. Hwu, W. C. Tu, C. F. Chuang

        Vol. 7. n. 4, pp. 4814-4821


Abstract - In this paper, a novel step-up converter is presented, whose operating principles are mainly based on charge pump capacitors and dual boost inductors. Furthermore, although three switches are used, no isolated gate driver is needed instead of one half-bridge gate driver and one low-side gate driver. Accordingly, the proposed converter is easy in analysis and simple in implementation. In addition, some experimental results are provided to verify the effectiveness of the proposed converter.

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Keywords: Step-Up Converter, Charge Pump, Boost Converter.



go to top On the Monitoring of Rotor Fault in Induction Machine by the Use of the TSA Method Applied to Stator Current
         by N. Ngote, S. Guedira, M. Ouassaid, M. Cherkaoui, M. Maaroufi

        Vol. 7. n. 4, pp. 4822-4828


Abstract - Rotor fault in induction motors are of significant importance since they usually lead to more severe failures. But, sometimes, particularly when the motor is unattainable (such as the engines immersed in the motor-driven pump groups), the accelerometer signal measurement is quasi impossible because of the inaccessibility in mounting transducers. An efficient and new method to detect the rotor fault may be the application of the Time Synchronous Averaging (TSA) to the stator current. This paper focuses on the detection of a rotor defect in a three-phase wound rotor induction motor. By exploiting the cyclostationarity characteristics of electrical signals, the TSA method is applied to the stator current signal which is conditioned in order to obtain a sensitive indicator, allowing the monitoring of the induction motor operation. Simulation and experimental results are presented in order to show the effectiveness of the proposed approach.

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Keywords: Cyclostationarity, Time Synchronous Averaging (TSA), Monitoring, Induction Motor, Rotor Fault, Simulation.


go to top Improved SVM with GA for Power Transformer Fault Diagnosis
         by Siyang Zhang, Fangjun Kuang, Weihong Xu

        Vol. 7. n. 4, pp. 4829-4836


Abstract - Diagnosis of potential faults concealed inside power transformers is the key of ensuring stable electrical power supply to consumers. The paper presents a transformer fault diagnosis based on improved support vector machines (SVM) with genetic algorithm (GA), in which a new kernel function M-RBF based on kernel function Gauss kernel function is developed to shorten the training time and improve its performance, and GA is used to select suitable parameters of SVM, it avoids over-fitting or under fitting of the SVM model occurring because of the improper determination of these parameters. Compared with other diagnosis approaches, experimental results demonstrated that the proposed method shows more excellent diagnostic performance on training speed and reliability.

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Keywords: Power Transformer, Fault Diagnosis, Support Vector Machines, Kernel Function, Genetic Algorithm.


go to top A Predictive Direct Torque Control of Induction Machines
         by A. Damiano, G. Gatto, I. Marongiu, S. Meo, A. Perfetto, A. Serpi

        Vol. 7. n. 4, pp. 4837-4844


Abstract - In this paper, a predictive Direct Torque Control (DTC) of an Induction Motor (IM) drive is presented. Although the control uses stator flux and current vectors as state variables, a novel set of variables have been introduced in order to directly manage torque, stator flux and current magnitude variations in each sampling time interval. Then, the existence domain of the above mentioned variables in each sampling time interval is determined and depicted graphically, together with the inverter voltage saturation and current limitation constraints. As a result, the proposed predictive control algorithm allows a better tracking of the IM reference torque profile than that achievable by means of the traditional DTC technique, especially in terms of current and torque ripple. The effectiveness of the proposed predictive DTC algorithm is verified by simulating an IM drive by means of the Matlab Simulink tool. The simulation results, which also refer to the case of the traditional constant switching frequency DTC, highlight the good performance of the drive, especially referring to torque ripple and to low speed operation.

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Keywords: Induction Motors, Predictive Control, Torque Control.


go to top A Direct-Drive Wind Turbine Control for a Wind Power Plant with an Internal DC Distribution System
         by A. Damiano, G. Gatto, I. Marongiu, S. Meo, A. Perfetto, A. Serpi

        Vol. 7. n. 4, pp. 4845-4856


Abstract - In this paper, a torque control algorithm of a Permanent Magnet Synchronous Generator (PMSG) for Direct Drive Wind Turbines (DDWTs) is proposed. In particular, a twelve-phase PMSG with four independent three-phase output subsystems has been considered with the aim of improving the DDWT torque management, energy efficiency, power generation and reliability; these goals are achieved by means of the decoupled control of each three-phase subsystem which the generator is split in. Hence, a novel coordinate transformation and the synthesis of the proposed master control algorithm are introduced: this last one allows the independent management of the reference currents of each subsystem and, thus, permits the development of an efficient variable speed wind turbine control. In addition, using the proposed DDWT, a novel topology of Continuous Medium Voltage Distribution system (CMVD) for a wind power plant is presented. In particular, the DC subsystems power outputs are connected by means the proposed CMVD to a centralized cascaded H-Bridge inverter structure, which is the only interface between the electric power transmission network and the wind power plant. The goodness of the proposed control algorithm is verified by means of a simulation study carried out in the Matlab Simulink environment, whose results are presented in the paper.

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Keywords: Multi-Phase Electrical Machines Control, Permanent Magnet Generators, Renewable Energy, Wind Power Generation, Direct Drive Wind Turbine.


go to top Recurrent Wavelet Network Control of PMSM Based on Wind-Turbine Emulator and PM Synchronous Generator System
         by Chih-Hong Lin

        Vol. 7. n. 4, pp. 4857-4866


Abstract - Recurrent wavelet neural network (RWNN) control is proposed for control of permanent magnet synchronous motor (PMSM) based on wind-turbine emulator (WTE) and a permanent magnet synchronous generator (PMSG) system. First, the field-oriented mechanism is designed for the control of the PMSG system. Then, a controlled rectifier (AC/DC power converter) and an inverter (DC/AC power converter) are developed to convert the electric power generated by a three phase PMSG system. Since the PMSG system is a nonlinear and time-varying dynamic system, two online trained RWNNs using backpropagation learning algorithm are introduced as the regulating controllers for both the DC-link voltage of the controlled rectifier and the AC line voltage of the inverter. Moreover, a closed loop PMSM based on wind-turbine emulator, also using the RWNN, is designed to produce the maximum power for the PMSG system at various wind speeds to confront the parameter dependency of the PMSM based on wind-turbine emulator. Furthermore, some experimental results are provided to show the effectiveness of the proposed PMSM based on WTE and PMSG system using the RWNN controller. Finally, to show the effectiveness of the proposed controller, comparative studies with proportional-integral (PI) controller are demonstrated by experimental results.

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Keywords: Permanent Magnet Synchronous Generator, Rectifier, Inverter, Recurrent Wavelet Neural Network, Proportional-Integral Controller.



go to top Adaptive Recurrent Wavelet Network Uncertainty Observer Based on Integral Backstepping Control for a SynRM Drive System
         by Chih-Hong Lin

        Vol. 7. n. 4, pp. 4867-4878


Abstract - The synchronous reluctance motor (SynRM) received much attention for many applications due to its simple construction. The control performance of a SynRM drive system is highly affected by nonlinear uncertainties, such as parameter variations, external load disturbance, magnetic saturation, high iron losses and friction force etc. The accurate mathematic models are difficult to be established for time-varying and nonlinear uncertainties of the actual SynRM drive system. In this paper an adaptive recurrent wavelet neural network (ARWNN) uncertainty observer based on integral backstepping control system is proposed to achieve the required high-control performance and robust to the uncertainties. Firstly, the field-oriented mechanism is applied to formulate the dynamic equation of the SynRM drive system. Secondly, an integral backstepping approach is proposed to control the motion of SynRM drive system. With proposed integral backstepping control system, the rotor position of the SynRM drive possesses the advantages of good control performance and robustness to uncertainties for the tracking of periodic reference trajectories. Moreover, to further increase the robustness of the SynRM drive system for nonlinear uncertainties, an adaptive RWNN uncertainty observer is proposed to estimate the required lumped uncertainty. The on-line adaptive rule of the RWNN is derived in accordance with Lyapunov function. The updated parameters of the RWNN are used by the gradient descent method and the backpropagation algorithm. Finally, the effectiveness of the proposed control scheme is verified by some experimental results.

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Keywords: Synchronous Reluctance Motor, Recurrent Wavelet Neural Network, Integral Backstepping, Lyapunov Function.



go to top Implementation of Speed Sensorless Drives for IPMSM Based on Simplified Stator Flux Observer
         by N. A. Rahim, M. A. Rahman, M. F. M. Elias, H. W. Ping

        Vol. 7. n. 4, pp. 4879-4884


Abstract - This paper presents an implementation of simplified Stator Flux Observer (SFO) for speed sensorless Field Oriented Control (FOC) drive of an Interior Permanent Magnet Synchronous Motor (IPMSM). The proposed SFO eliminates the use of the extended rotor flux in order to estimate the rotor position. The observer needs voltage and current measurement of the motor. The voltage measurement is obtained from a voltage reconstruction algorithm while the current measurement is obtained from two hall-effect current sensors. TMS320F2812 EzDSP board is used as motor controller. The overall motor drive system was verified and experimentally tested on a 600W, 4 poles, IPMSM.

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Keywords: Stator Flux Observer, IPMSM, Sensorless Drives, Vector Control.




go to top High-Precision Control for a Surface-Mounted Permanent Magnet Synchronous Motor Based on Inverse System Approach
         by Gang Liu, Cong Zhang

        Vol. 7. n. 4, pp. 4885-4896


Abstract - This paper addressed the problem of coupling in a surface-mounted permanent magnet synchronous motor (PMSM), and presented a decoupling control approach based on inverse system. Cascading the inversion with original system, the highly nonlinear, multivariable and strongly coupled system was decoupled into two independent pseudolinear subsystems, or an angular speed subsystem and a d-axis stator current subsystem. Then, a hybrid control scheme that combined the sliding-mode control approach and the internal-model principle was proposed with space vector modulation (SVM) technique. With this novel configuration, a time-varying sliding mode controller (SMC) with an integral term, and a classical 2-degree-of-freedom internal-model controller (2-DOF IMC) were adopted in the decoupled angular speed subsystem and the d-axis stator current subsystem, respectively. Ultimately, the proposed scheme was implemented by an established experimental system with low computational demand and high accuracy. Comparative experiments were presented to demonstrate the validity and effectiveness of the proposed control scheme.

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Keywords: Surface-Mounted Permanent Magnet Synchronous Motor (PMSM), Inverse System, Pseudolinear Subsystem, Time-Varying Sliding-Mode Controller (SMC), 2-Degree-of-Freedom Internal-Model Controller (2-DOF IMC), Space Vector Modulation (SVM).


go to top Development and Implementation of a Speed Sensorless Induction Motor Drives using an Adaptive Neuro - Fuzzy Flux Observer
         by S. Chekroun, M. Zerikat, A. Mechernene, N. Benharir

        Vol. 7. n. 4, pp. 4897-4904


Abstract - In this paper, we propose an adaptive neuro-fuzzy inference system for high performance induction motor drive. The simultaneous observation of rotor speed and stator resistance in induction drive is obtained through a neuro-fuzzy observer trained with a backpropagation algorithm. The dynamic performance and robustness of the proposed neuro-fuzzy adaptive observer are evaluated under a variety of operation conditions. The suggested approach is designed and implemented in the laboratory and its effectiveness in tracking application is verified. Experimental results have shown excellent tracking performance of the proposed speed sensorless control system and have convincingly demonstrated the usefulness of the hybrid neuro-fuzzy flux observer in high performance drives with uncertainties.

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Keywords: Induction Motor, Sensorless Control, Adaptive Flux Observer, ANFIS, Estimation.



go to top Investigation of New Hysteresis Current Controller Performance for Induction Motor Drive
         by E. E. El-Kholy, M. El-Shahat Dessouki, A. Alwadie

        Vol. 7. n. 4, pp. 4905-4914


Abstract - This paper presents a new variable band hysteresis current controller for controlling the switching frequency variation in the two-level PWM inverter fed induction motor drives for various operating speeds. A novel concept of online variation of the band based on both the instantaneous load current and current change for each sampling period is presented to determine the hysteresis band. A performance comparison of the proposed controller with conventional hysteresis current controller for IM drive is provided in simulation. The proposed drive system is also implemented in real-time using DSP board for a laboratory 1.5 hp motor. Comparative simulation and real-time results verify the feasibility of the proposed scheme and demonstrate that the proposed method has ensured constant switching frequency and improved the performance of the drive system.

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Keywords: Switching Frequency, Hysteresis Current Controller (HCC), Induction Motor (IM).


go to top A Comparative Study of Battery Models Parameter Estimation
         by Mohamed Daowd, Noshin Omar, Peter Van Den Bossche, Joeri Van Mierlo

        Vol. 7. n. 4, pp. 4915-4924


Abstract - Battery system as a vital part in the Electrical Vehicles (EVs) needs accurate and efficient battery model to predict and optimize battery performance especially under different runtime operations. An accurate method for estimating the battery model parameters is necessary before constructing a reliable battery model. This paper gives a review on the different battery model parameters estimation methods. As well as, propose a modified methodology for battery models parameters estimation based on MATLAB/Simulink® using parameter estimation tool under Simulink environment. Four of the famous battery models; Thevenin, the Partnership for a New Generation of Vehicles (PNGV), Second-order and Randles battery models are used for battery model parameters estimation and validation. Hence, Lithium polymer batteries have been tested by specific standard tests at different state of charge (SoC), temperature, current rate (C-rates) and cycle number. Afterward, the four battery models parameters are estimated according to these conditions.

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Keywords: Matlab/Simulink Parameters Estimation, Thevenin, PNGV, Freedomcar, Randles Battery Model.



International Review of Electrical Engineering - Papers- Part B



go to top Transient Stability Assessment Based Upon Differential Transform Method
         by D. Lauria, C. Pisani

        Vol. 7. n. 4, pp. 4925-4935


Abstract - The paper aim is to develop a novel fast procedure able to assess the transient stability of electrical power systems. The proposed approach is based upon the Differential Transform Method (DTM). The problem of determining the transient stability power limits is formalized as a boundary value problem. A proper approximation based on Legendre polynomials for the electric output power term of the swing equations is previously performed in order to apply in efficient way the canonical DTM's rules. In this manner the boundary problem of determining the transient stability limits has been converted in terms of algebraic equations system. The great advantage of this formulation relies into a very low computational burden that makes it much suitable in all the contexts where the calculation time covers a crucial role. Moreover, it has an intrinsic robustness to the characteristic ill-conditionality of the boundary value problems. The developed methodology has been numerically tested with respect to an One Machine Infinite Bus System (OMIB), characterizing the main problem randomness in proper probabilistic terms. Although this makes the problem further complex, surely it represents a more faithful representation of what happens in realistic context.

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Keywords: Differential Transform Method, Transient Stability.



go to top A Two-Step Procedure for On-Line Detection of Power Oscillations
         by D. Lauria, C. Pisani

        Vol. 7. n. 4, pp. 4936-4947


Abstract - The paper develops a novel two-step procedure for on-line detection of power oscillations. It consists of a preliminary estimation of the electromechanical mode number by using Hankel Singular Value Decomposition (HSVD) and a successive application of the Variable Projection Algorithm (VarPro) to determine the characteristics of the electromechanical mode. Indeed, such a procedure represents the novelty element of a generalized WACS architecture, specifically designed in the paper for addressing the problem of the noise corruption and the data packets dropouts of the working signals. Several case studies are presented in order to test the effectiveness of the proposed methodology, comparing moreover its performances with those of other methods suitable for this kind of application.

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Keywords: Detection, Inter-area oscillations, Smart Power Grids, WACS, WAMS.



go to top Mitigation of Voltage Sag and Swell Using Dynamic Voltage Restorer without Energy Storage Devices
         by S. Abdul Rahman, P. Somasundaram

        Vol. 7. n. 4, pp. 4948-4953


Abstract - Utilization of Dynamic Voltage Restorer (DVR) to protect sensitive loads against short-term voltage disturbances has been proven to be an aggressive solution in medium- and high-power applications. For low-power applications further cost reductions are required to make the technology even more competitive. Though many works have been proposed for various topologies of DVR almost all the works utilized energy storage devices. Thus the conventional DVR will be more bulky with less power density and need to be maintained in time. The compensation time is also proportional to the rating of the energy storage devices. As the compensation duration increases the size the conventional DVR also increases. The DVR model is replacing the conventional AC-DC-AC converter by a Matrix Converter thus avoiding bulky energy storage devices and able to compensate for indefinite time with very high power density. The DVR is connected between the source and the load. The matrix converter based DVR circuit requires only four bi-directional IGBTs. Pulse Width Modulation (PWM) technique is adapted for the synthesis of switching pulses to control the switches. The circuit model for matrix converter based DVR system is developed using matlab simulink to perform simulation studies. From the simulation results it is observed that the DVR is able to compensate voltage sag of 50% and swell of 100% with the THD less than 5%. Experimental results of a 1500 VA, 230 V, and 50 Hz laboratory prototype is presented.

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Keywords: Dynamic Voltage Restorer, Energy Storage Devices, Matrix Converter, Power Quality, Pulse Width Modulation, Voltage Sag, Voltage Swell.



go to top Application of Multi-Objective Gravitational Search Algorithm (GSA) For Power System Stability Enhancement by Means of STATCOM
         by Ali Ajami, Mehdi Armaghan

        Vol. 7. n. 4, pp. 4954-4962


Abstract - In this paper, on the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using its modified linearized Phil¬lips-Heffron model installed with STATCOM, the potential of the STATCOM supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned to simultaneously shift the undamped electromechanical modes to a prescribed zone in the s-plane. The problem of robus¬tly STATCOM based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective func¬tion comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm (GSA) that has a strong ability to find the most optimistic results. To ensure the robustness of the proposed damping control¬ler, the design process takes into account a wide range of operating conditions. The effectiveness of the proposed controller is demon¬strated through controllability measure, eigenvalue analysis and some performance indices studies. The different loading conditions are simulated on a single-machine infinite-bus system and the rotor speed deviation, internal voltage devia¬tion, DC voltage deviation and electrical power devia¬tion responses are studied with the effect of this FACTS controller. The re¬sults analysis reveals that the tuned GSA based STATCOM controller using the proposed multi-objective function has an excellent capabil¬ity in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: STATCOM, Gravitational Search Algorithm, Power System Stability.




go to top Security Enhanced Optimal Power Flow with Transmission Cost Solution
         by Bastin Solai Nazaran.J, Selvi.K

        Vol. 7. n. 4, pp. 4963-4970


Abstract - Power system security involves taking remedial action against possible network overloads due to contingencies. Security can be enhanced by redispatching generating units and by changing phase shifter settings. This paper presents a CMAES (Covariance Matrix Adapted Evolutionary Strategy) based OPF (Optimal Power Flow) algorithm for identifying optimal control variables to minimize operating cost while ensuring security. Operating cost includes generation cost and transmission cost under pre and post contingency cases. Overloading is alleviated by redispatching of generation alone. Severity index is added as constraint to the objective function to ensure overload alleviation. Transmission cost is calculated using power flow tracing method. Matrix based power flow tracing method is used to allocate transmission charges. IEEE 30 bus and IEEE 118 bus systems are used for simulation.

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Keywords: CMAES, Power Flow Tracing, Power System Security, Severity Index, Transmission Cost. 


go to top Analysis and Assessment of Power System Including Wind Farm by Using SVC and STATCOM
         by Saeid Jalilzadeh, Ahad Kazemi, Peyman Farhang

        Vol. 7. n. 4, pp. 4971-4979


Abstract - This paper presents operation and control strategies of a wind farm which is connected to the grid in presence of SVC and STATCOM. The proposed wind farm is 50MW, includes of 5 induction generators based 10MW Fixed speed wind turbines driving squirrel cage induction generators while each of the wind turbines are equipped with blade angle controller. To assess the effectiveness and robustness of the proposed controllers, simulation studies are carried out for three operating conditions. Firstly, normal operation of the system with consideration of wind speed variations is surveyed. Next, analysis of an unsymmetrical single-phase fault is performed on the system operation. Moreover, a symmetrical three-phase fault is analyzed, extensively. Moreover, the effectiveness of the proposed controllers is explained through some performance indices studies. The performance of proposed controllers for the stabilization of the power system is evaluated by computer simulation studies in PSCAD/EMTDC environment. The simulation results show that the system composed with the proposed controllers can improve the transient and normal operations of the wind farm. Simulation results under different operating conditions and performance indices show fine operation of the Wind farm with contribution of mentioned FACTS devices even when the severe fault has been applied.

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Keywords: Wind Farm, Induction Generator, Blade Angle Controller, STATCOM, SVC.


go to top Effects of Catenary, Compaction and Phase Conductor Arrangement of Double Circuit Lines on ROW Width Using Calculations and FEM
         by T. Jahangiri, M. Zavvari, V. Masouminia

        Vol. 7. n. 4, pp. 4980-4991


Abstract - In this paper, the effects of optimum phase conductor arrangement and compaction of tower for electric and magnetic fields minimization of 400 KV double circuit lines are investigated by using of Finite Element Analysis Software ANSYS. Two typical types of compact and conventional transmission lines are modeled by FEM with symmetrical and optimum phase conductor arrangement. The electric and magnetic fields produced by both lines are calculated by analytical and 2D finite element method at the mid-span. To consider the catenary effect along the whole span, 2D finite element analysis is developed by APDL programming in order to achieve 3D distribution of electric and magnetic fields between adjacent towers. Finally, some aspects concerning the necessary ROW (Right of Way) are pointed and the necessary ROW width of the compact and conventional overhead lines with the symmetrical and the optimum phase conductor arrangement are determined based on finite element results and the ICNIRP standard.

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Keywords: Electric and Magnetic Field, Finite Element Method, Catenary Effect, Compact Overhead Lines, Optimum Conductor Arrangement, Right of Way.


go to top A Fuzzy Based Under-Frequency Load Shedding Scheme for Islanded Distribution Network Connected With DG
         by H. Mokhlis, J. A. Laghari, A. H. A. Bakar, M. Karimi

        Vol. 7. n. 4, pp. 4992-5000


Abstract - The frequency of power system is very sensitive to load changing when operating in islanded mode. This may causes overloading or loss of generation cases. Under-Frequency Load Shedding (UFLS) Scheme is commonly applied to stabilize the frequency during these cases. Conventional UFLS scheme operates successfully in interconnected grid system and may not work well when applied to DG based system operating in islanded mode. This paper presents a new fuzzy logic based under- frequency load shedding scheme implemented on mini hydro type-DG operating in islanded mode. The proposed strategy is based on frequency, rate of change of frequency and load prioritization. In proposed UFLS scheme, a fuzzy logic load shedding controller (FLLSC) with Load Shed Controller Module (LSCM) is modelled. FLLSC measures amount of load to be shed and LSCM shed the respective load to stabilize frequency. The proposed scheme is validated on different event-based and response-based cases. Simulation results show that proposed scheme is effective in shedding optimal number of loads while stabilizing the frequency.

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Keywords: Distributed Generation (DG), Fuzzy Logic Load Shedding Controller (FLLSC), Load Shed Controller Module (LSCM), Islanded Distribution Network.



go to top A Power Flow Algorithm for Composite Meshed and Radial Systems Based on Topological Division
         by Yiming Li, Wenyuan Li, Wei Yan, Xiaofeng Jia, Xia Zhao

        Vol. 7. n. 4, pp. 5001-5009


Abstract - A new power flow algorithm for composite meshed and radial systems is presented using the topological division of system structure. An automatic topology searching process is developed to identify the coupling mesh, non-coupling mesh and radial sub-networks. A compensation-based method is proposed to model the non-coupling mesh sub-networks whereas the existing Newton Raphson (NR) and the back/forward sweep methods are used to model the coupling mesh and radial sub-networks. The resolution is a unified and sequentially iterative procedure. The applications of the proposed method to the IEEE 300-bus system and three actual utility systems demonstrate the better performance of the proposed method in computing speed and convergence than the conventional NR and PQ decoupled methods.

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Keywords: Mesh Network, Power Flow, Power Systems, Radial Network, Topology Analysis.




go to top On the Subtransmission Systems Reliability Analysis Based on Optimal Load-Shedding Correlated between Load-Points
         by P. J. Martínez, A. de la Villa, J. L. Martínez

        Vol. 7. n. 4, pp. 5010-5021


Abstract - The technique proposed in this paper is based on a combined analysis of the reliability assessment of the branch-node model of the subtransmission system and on “one by one” reliability assessment of the substations of the subtransmission system. In the combined analysis, first, a classical state enumeration reliability analysis is performed for the branch-node model of the subtransmission system, second, by considering “one by one” the substations of the subtransmission system, a state enumeration process is applied to each one to obtain the correlated load-shedding between the substations of the subtransmission system, and finally, the reliability indices calculated in the first and second stages are combined to obtain accurate reliability indices from the viewpoint of the overall system and the load-node.Test results show that the proposed methodology is suitable both for planning studies and for 24 hours-ahead preventive reinforcement and security assessment.

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Keywords: State Enumeration, Power System Reliability, Subtransmission/Distribution Systems, Substation Configurations.


go to top Improving the p-q Compensation Method in the Presence of Low-Order Harmonics by LWT: Theory and Implementation
         by J. Modarresi, M. Tavakoli Bina, M. A. Golkar

        Vol. 7. n. 4, pp. 5022-5028


Abstract - Increase of harmonics causes power quality issues in power systems. To lower harmonics in power systems, various algorithms have been proposed such as the p-q method, employing a conventional low-pass filter (LPF) in these algorithms. In particular, the time response of algorithms increases under the presence of low-order harmonics. This paper examines three types of wavelet-based algorithms instead of the conventional LPF in order to improve the time response of the p-q method. The performed study results in selecting the LWT as the lowest time-response compared to the conventional LPF in the presence of low-order harmonics. To confirm the validity of proposed LPF replacement, first all three wavelet-based methods were simulated with SIMULINK. Then, the selected LWT among other methods were implemented on the DSP TMS320F28335 to verify the overall performance. Both simulations and experiments show the resultant LWT as a suitable replacement for the conventional LPF in power system compensating algorithms.

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Keywords: LWT, p-q Method, LPF, Wavelet Transform, DSP.


go to top Fuzzy Based Unified Power Flow Controller to Control Reactive Power for a Practical Thermal Power Station
         by C. Ramesh, M. Rajaram, S. Chenthur Pandian

        Vol. 7. n. 4, pp. 5029-5035


Abstract - Unified Power Flow Controller (UPFC) is a power electronic based device that has capability of controlling the power flow through the line by controlling appropriate its series and shunt parameter. It has been reported that UPFC can improve transient stability of a simple system. The UPFC consists of two solid-state voltage source inverters (VSIs) connected by a common DC link that includes a storage capacitor. The first one is a static synchronous compensator (STATCOM) the second one is a static synchronous series compensator (SSSC). The proposed fuzzy logic controller is used to arrange the controls of the STATCOM and SSSC, in order to take into account, by approximated reasoning, the system nonlinearity and devices interaction. UPFC is a well-known Flexible AC Transmission System (FACTS) device that can control power-system parameters such as terminal voltage, line impedance and phase angle. The objective in this paper is to maintain a constant voltage profile irrespective of changes in the load. This is achieved either by injecting or absorbing the reactive power. In this paper for implementing fuzzy logic approach two inputs (error voltage and capacitor value) are taken and the “Inverter Pulse” which is used for UPFC power electronic device to control the voltage is taken as an output. Case studies have been performed for National Thermal Power System of a practical system. Three generating stations each of 210 MW have been considered in this work. These three generators (Unit 1, 2, 3) are connected to a common load bus bar of 230 KV system. This practical system is considered as a conventional method without UPFC. Simulation work in MAT lab has been carried our with fuzzy controller and UPFC. It is observed that with Fuzzy and UPFC the reactive power requirement is less and a constant voltage of 230 KV has been achieved.

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Keywords: Power System, UPFC, FACTS, Fuzzy Controller, Reactive Power Control.


go to top Fuzzy Logic Implementation for Reactive Power Control in Utility System
         by C. Ramesha,  M. Rajaramb, S. Chenthur Pandian

        Vol. 7. n. 4, pp. 5036-5042


Abstract - The objective of reactive power control in a power station is to minimize the real power loss which will reduce the operating cost and improve the voltage profile. To maintain the voltage level at various buses either the reactive power is injected or absorbed. Fuzzy logic approach will be a better intelligent technique for the application to control the reactive power. The ‘load’, and the ‘voltage level’ are considered as two inputs and the ‘reactive power’ is taken as an output. The input variable ‘load’ has been divided into five triangular membership functions. Another input variable ‘voltage’ has been divided into three triangular membership functions. The required ‘reactive power’ value as an output has been divided into five triangular membership functions. Case studies have been performed for a practical national thermal power station in India with seven generators. Practical calculation and results are taken for simulation which has been performed by using the developed software in MATLAB package. It is observed that the reactive power requirements calculated by implementing fuzzy logic approach is much lower than the conventional method which is more economical and requires less number of capacitor or reactive power compensating devices.

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Keywords: Fuzzy Logic, Reactive Power, Unified Power Flow Controller (UPFC), Membership Functions, Control Centre. 


go to top SIPS Planning for Power System Security
         by Andres F. Leal, Mario A. Ríos

        Vol. 7. n. 4, pp. 5043-5050


Abstract - The special integrated protection systems (SIPS) are alternative tools in order to improve the security of power systems that have been developed or formulated to mitigate the impact of particular problems when a disturbance occurs in the power system. This paper proposes a methodology of planning focused in the selection of sets of SIPS in a joint analysis of angular stability, voltage stability and frequency stability using Fuzzy Analysis to take decisions. The methodology has been tested on the 68 nodes NEPS-NYPS system.

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Keywords: Fuzzy Logic, Power System Stability, Power System Security, Special Integrated Protection Systems (SIPS).



go to top New Method for Optimal Location and Parameters Setting of UPFC Devices Using Multi-Criteria Optimization
         by Aleksandar S. Savić, Predrag Č. Stefanov

        Vol. 7. n. 4, pp. 5051-5060


Abstract - This paper is proposing a new procedure for a simultaneous optimization of all the criteria that may influence the decision, while it is not necessary to compare the criteria, and therefore provides that no single criterion is favored over the others. Therefore, this procedure represents an unbiased basis for decision making in planning development of today's modern power transmission networks. The procedure is based on application of a genetic algorithm, where all the criteria are unique, and set of feasible solutions is defined by possible modes of operation of each individual component of the power transmission system, and of the power transmission system as a whole. The procedure presented in this paper is limited to the case of power transmission network development by adding the UPFC control devices. Such devices include technical capabilities of all modern control devices based on application of power electronics. The goal of the proposed procedure is to select the location and parameters of the UPFC devices to meet all requirements of the power transmission network development in a deregulated environment.

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Keywords: Multi-Criteria Optimization, UPFC Devices, Genetic Algorithm.



go to top Multi Input Stabilizer Design Based on UPFC Using Particle Swarm Optimization
         by M. Shirvani, B. Keyvani, A. Memaripour, A. Salimi

        Vol. 7. n. 4, pp. 5061-5067


Abstract - In this paper a new multi input stabilizer design based on Unified Power Flow Controller (UPFC) is presented. Where, UPFC is used to enhance damping of Low Frequency Oscillations (LFO) at a multi area power system. The proposed stabilizer utilizes two signals as input signals and therefore it is a multi input stabilizer (MI-S). The parameters of the proposed stabilizer are tuned by minimizing a time domain performance index. The proposed stabilizer is evaluated against the conventional stabilizer (CS) at two multi area power systems considering system parametric uncertainties. Particle Swarm Optimization (PSO) is used to adjustment the proposed UPFC supplementary stabilizer. Several time-domain simulation tests visibly show the validity of proposed method in damping of power system oscillations. Also Simulation results emphasis on the better performance of MI-S in comparison with CS.

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Keywords: Flexible AC Transmission Systems, Unified Power Flow Controller, Low Frequency Oscillations, Multi Input Stabilizer, Particle Swarm Optimization.



go to top Autotuning Power System Stabilizer based on Fuzzy Plant Model
         by Zlatka Tecec Ribaric, Jadranko Matusko, Ivan Petrovic

        Vol. 7. n. 4, pp. 5068-5079


Abstract - The paper presents a newly proposed autotuning power system stabilizer (PSS) based on a Takagi-Sugeno (TS) fuzzy model. The main advantage of the proposed PSS is in a stable regulation structure without the critical parts such as on-line identification and feedback gain calculations in real-time. Additionally, the proposed algorithm can be implemented both in floating-point and in fixed-point microprocessor platforms. The simulation results presented in the paper show that the proposed PSS effectively damps active power oscillations and that the commissioning process can be performed with no need for expert knowledge from the commissioning staff.

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Keywords: Power System Stabilizer, Synchronous Machine, Fuzzy Model, Takagi-Sugeno.



go to top Optimal Over-Current Relay Coordination Using Improved Harmony Search Method
         by Dusit Uthitsunthorn, Thanatchai Kulworawanichpong

        Vol. 7. n. 4, pp. 5080-5090


Abstract - This paper presents optimal coordination of over-current relays by using improved harmony search method (IHS). The objective function of the relay coordination problem is to minimize the operation time of associated relays for given fault conditions in the protection system. The control variables used in this paper are the pickup current and the time dial setting of the relays. The proposed method was tested with 5-bus, WSCC 9-bus and standard IEEE 14-bus test systems. For benchmarking, sequential quadratic programming (SQP) and genetic algorithm (GA) were employed to solve this optimal relay coordination problem. The results showed that the IHS is capable to minimize the operation time of relays in the entire system. As a result, all search algorithms can solve optimal coordination relay which the improved harmony search method gives the best solutions for optimal coordination relay setting.

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Keywords: Optimal Coordination, Time Dial Setting, Time Grading Margin.



go to top Transient Stability Enhancement of the Power System Interconnected with Wind Farm Using Generalized Unified Power Flow Controller with Simplex Optimized Self-tuning Fuzzy Damping Scheme
         by A. M. Vural, K. C. Bayindir

        Vol. 7. n. 4, pp. 5091-5107


Abstract - Due to increasing penetration of wind power into traditional grid, co-working of synchronous generators with wind turbines is gaining attention in terms of system stability. This paper deals with the transient stability enhancement of such systems by generalized unified power flow controller (GUPFC) having grid frequency switching quasi multi-pulse converters. Besides independent real and reactive power flow control capability of the two series converters, one series converter is commissioned to damp synchronous/induction generator speed fluctuations by a self-tuning fuzzy damping scheme in which output scaling factor is adjusted on-line according to a second fuzzy rule-base defined on error and error-integral of the synchronous generator speed. Damping function is further enhanced via simplex optimized gains cascaded to fuzzy inference system. AC bus voltage and DC link voltage of GUPFC are effectively controlled by the shunt converter without disturbing other control loops. The comparative simulation studies are carried out on a hybrid simulation platform in which power network and converters with their control blocks are modeled in PSCAD, while only the fuzzy arrangement of the control blocks is executed in MATLAB by interfacing these two programs on-line. Different disturbance scenarios have shown that the proposed approach exhibits superior damping performance than standard fuzzy logic control or PI regulator.

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Keywords: Wind Power, Self-Excited Double Cage Induction Generator, Transient Stability, Oscillation Damping, Self-Tuning Fuzzy Control, Flexible AC Transmission Systems (FACTS), Generalized Unified Power Flow Controller (GUPFC), Quasi Multi-Pulse Voltage Source Converter, Simplex Method.


go to top Reconfiguration Distribution Network with Multiple Distributed Generation Operation Types Using Simplified Artificial Bees Colony
         by J. J. Jamian, Z. J. Lim, W. M. Dahalan, H. Mokhlis, M. W. Mustafa, M.N. Abdullah

        Vol. 7. n. 4, pp. 5108-5118


Abstract - The power losses in the distribution network are the critical issues that most researchers are trying to solve nowadays. From the passive distribution network in the last decades, the existing of Distributed Generation (DG) in the system will now allow the network to contribute in supplying some of the power to the load. However, selecting the optimal size of DG plays important role to avoid any drawback to the network. The connection of high capacity and excess number of DG units to electrical power system will lead to very high power losses. This factor makes the optimal size of DG become an important issue for the network to have lower power losses value. Furthermore, the use of reconfiguration method in cooperating with the DG units can help the system to have much lower power loss for the distribution system. Since the reconfiguration only required small investment in controlling method, it is very suitable to be used in improving the voltage profile and the power losses after the optimal DG is achievable. Three types of DG modes are used in the study which is constant voltage mode (PV), constant voltage with reactive power mode (PV with VAR constraint) and constant power mode (PQ mode).The Rank Evolutionary Particle Swarm Optimization (REPSO) and a Novel Simplified Artificial Bee Colony (SABC) are used in finding the optimal size of DG and the best configuration of the network respectively. The results show that the use of reconfiguration technique has improved the power losses as well as the voltage profile for the network even after optimal DG sizing has been achieved.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Distributed Generation, Optimization Techniques, Power Loss Reduction, Reconfiguration.


go to top A Novel Approach to Forecast Day-Ahead Electricity Prices by Means of Neural Networks Using Groups of Similar Hours
         by Daniele Menniti, Nadia Scordino, Nicola Sorrentino

        Vol. 7. n. 4, pp. 5119-5133


Abstract - Forecasting short-term electricity market prices has been the focus of several studies in recent years. Although various approaches have been examined, achieving sufficiently low forecasting errors has not always been possible. However, certain applications, such as demand-side management, do not require exact values for future prices, but utilize average values as the basis for making short-term scheduling decisions. With the aim of enhancing the accuracy of the day-ahead electricity price forecasting, field records of the Italian electricity market have been correlated so as to identify a number of blocks of hours, characterized by similarity of price. This paper thus proposes an approach to forecast the day-ahead electricity prices by means of a number of Neural Networks (NNs), with such a number being equal to the number of groups of hours with similarity of price, and with each NN forecasting the mean price over the hours belonging to the related group, as previously determined. Simulation results show that the fundamental and novel contribution of identifying, firstly, the membership of an hour to a particular group of hours, clustered according to their similarity of price, and then forecasting day-ahead prices for the resulting number of groups of hours performs fairly well if compared with other forecasting techniques, either on an hourly or on an average basis, in terms of mean absolute and absolute percentage errors, as well as of variance.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Back Propagation, Electricity Market Prices, Forecasting, Neural Network, Time Series.


go to top A Hybrid Evolutionary Programming – Tabu Search Method for Hydro-Thermal Scheduling With Cooling – Banking Constraints
         by Nimain Charan Nayak, C. Christober Asir Rajan

        Vol. 7. n. 4, pp. 5134-5143


Abstract - This Paper proposes a new hybrid algorithm for solving the Unit Commitment problem in Hydrothermal Power System using a hybrid Evolutionary Programming – Tabu Search method with cooling-banking constraints. The main objective of this project is to find the generation scheduling by committing the generating units such that the total operating cost can be minimized by satisfying both the forecasted load demand and various operating constraints of the generating units. It is a Global Optimization technique for solving Unit Commitment Problem, operates on a system, which is designed to encode each unit’s operating schedule with regard to its minimum up/down time. In this method, the unit commitment schedule is coded as a string of symbols. An initial population of parent solutions is generated at random. Here the parents are obtained from a pre-defined set of solutions i.e. each and every solution is adjusted to meet the requirements. Then, random recommitment is carried out with respect to the unit’s minimum down times. Tabu search (TS) is a powerful optimization procedure that has been successfully applied to a number of combinatorial optimization problems. It avoids entrapment at local optimum by maintaining a short term memory of recently obtained solutions. The memory structure assists in forbidding certain moves that deteriorates the quality of the solution by assigning Tabu status to the forbidden solutions. The Tabu status of a solution can be overruled if certain conditions are satisfied expressed in the form of Aspiration Level. Aspiration Level (AL) adds flexibility in Tabu Search by directing the search towards attractive moves. The best population is selected by Evolutionary Strategy. Numerical results are shown comparing the cost solutions and computation time obtained by using the proposed hybrid method than conventional methods like Dynamic Programming, Lagrangian Relaxation.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Evolutionary Programming, Tabu Search, Unit Commitment, Dynamic Programming, Lagrangian Relaxation.



go to top An Artificial Bee Colony Algorithm to Solve Nonlinear and Nonconvex Economic Dispatch Problem in Power Systems
         by M. S. Payam, E. Bijami

        Vol. 7. n. 4, pp. 5144-5154


Abstract - This paper presents the application of an evolutionary algorithm namely as Artificial Bee Colony (ABC) algorithm to solve Economic Dispatch (ED) problem that is known as a highly constrained non-linear optimization problem with non-convex space. The Artificial Bee Colony algorithm is a population-based optimization algorithm and one of the most recent swarm intelligence based algorithms which is inspired from the particular intelligent behavior of honey bee swarms when searching for food source. The ABC algorithm is proven its superior capabilities, such as faster convergence and better global minimum achievement. Practical ED problem in power system has non-smooth cost functions subject to various equality and inequality constraints that make the ED problem be a nonlinear and non-convex optimization problem. To show the efficiency of the proposed ABC algorithm in solving ED problem, it is applied to four test systems having non-convex solution spaces. Also, the results obtained by the ABC algorithm are compared with the recently previous approaches reported in the literature. Simulation studies show the superiority and advantages of the ABC over the other methods.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Economic Dispatch Problem, Artificial Bee Colony Algorithm, Non-Convex Function.



go to top A Hybrid Artificial Bee Colony Approach for Security Constrained Unit Commitment
         by C Christopher Columbus, Sishaj P Simon

        Vol. 7. n. 4, pp. 5155-5166


Abstract - In the deregulated electricity market secure operation is an enduring concern of the independent system operator (ISO). For a secure and economical hourly generation schedule of the day ahead market, ISO executes the security constrained unit commitment (SCUC) problem. The objective of the paper is to develop scheduling algorithm using hybrid artificial bee colony algorithm for electric generation that account directly for system security requirements. Utilities can obtain significantly better results if they use optimal scheduling algorithms, which comply directly with security requirements. The proposed SCUC formulation includes constraints such as hourly power demand, system reserves, ramp up/down limits and minimum ON/OFF duration limits. The innovation of our approach is to capture the system security requirements within a network flow sub-problem that is solved in conjunction with the unit commitment problem. To solve such SCUC model a binary coded artificial bee colony (BABC) is used for unit commitment master problem and real coded artificial bee colony algorithm (RABC) is used for the security constrained economic dispatch sub-problem. The effectiveness of the proposed method to solve the SCUC problem is shown on different test systems.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Security Constraints, Security Constrained Unit Commitment. Artificial Bee Colony, Security Constrained Economic Dispatch, Transmission Constraints.


go to top Application of Bacteria Foraging Strategy with Constraint Satisfaction Technique for Emission and Economic Dispatch Problems
         by E.Mariappane, K.Thyagarajah

        Vol. 7. n. 4, pp. 5167-5173


Abstract - The emission of pollutants from coal based thermal generating stations into the atmosphere such as oxides of carbon (COx), oxides of Nitrogen (NOx) and oxides of sulphur (SOx) causes green house effect and leads to the global warming. Since coal based thermal power generation is the major source of electricity in all the developing countries, it is the challenge for the power engineers to solve the multi objective optimization problems such as emission and economic dispatch problems. This paper presents an efficient Bacteria Foraging Algorithm for the economic and emission dispatch problems. The approach utilizes the natural selection of global optimum bacterium having successful foraging strategies as the cost function. The proposed algorithm is applied for solving economic dispatch, emission dispatch, combined economic and emission dispatch and emission constrained economic dispatch of IEEE-30 bus system with six thermal generators. The performance of the proposed algorithm is compared with the conventional method, real coded GA, hybrid GA and PSO methods and it is observed that this method is reliable and may replace effectively the conventional practices presently performed in different central load dispatch centers. The comparison of results shows that the proposed method was indeed capable of obtaining higher quality solutions efficiently for the above problems.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Bacteria Foraging Algorithm, CEED, Dispersal, ECED, Elimination, Emission Dispatch, Genetic Algorithms, Particle Swarm Optimization, Reproduction, Swarming.


go to top Diversity Preserved Multiobjective Evolutionary Programming Algorithm for Environmental/Economic Dispatch Problem
         by D. Nelson Jayakumar, P. Venkatesh

        Vol. 7. n. 4, pp. 5174-5185


Abstract - This paper proposes a Diversity Preserved Multiobjective Evolutionary Programming (DPMOEP) algorithm to solve Environmental/Economic Dispatch (EED) Problem. The EED problem is a well-known multiobjective nonlinear optimization problem. In the proposed DPMOEP, non dominated solution ranking is implanted as selection mechanism and clustering algorithm is employed to keep the diversity among the Pareto optimal solutions. In order to improve the algorithm efficiency a time varying scaling factor is incorporated. The proposed DPMOEP technique is tested on the three units, six unit and IEEE 30 bus test systems. To prove the effectiveness of the proposed approach, results are compared with multiobjective particle swarm optimization algorithm and non-dominated sorting genetic algorithm-II. Several optimization runs have been made for each test cases and performance measures such as spread, maximum spread; number of Pareto optimal solution output and the percentage of participation in elite set are also compared. The obtained well-distributed Pareto front solutions and the statistical results confirm the potential of the proposed approach to solve the multiobjective EED problem.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Multiobjective Optimization, Evolutionary Programming, Particle Swarm Optimization, Environmental Economic Dispatch, Pareto Optimal Solution.


go to top STNEP Considering Voltage Level and Uncertainty in Demand Using IABPSO
         by Saeid Jalilzadeh, Ali Kimiyaghalam, Meisam Mahdavi, Ahmad Ashouri

        Vol. 7. n. 4, pp. 5186-5195


Abstract - Up till now, different approaches have been proposed for solution of static transmission network expansion planning (STNEP) problem. But, in all of them, STNEP considering the voltage level and uncertainty in demand has not been solved by improved advanced binary particle swarm optimization (IABPSO) algorithm. BPSO is a new population-based intelligence algorithm that has some disadvantages like premature convergence phenomenon when solving a complex optimization problem like STNEP. To resolve this problem and considering voltage level and uncertainty in demand, IABPSO approach is presented. The simulation results show that precision of the proposed algorithm for the solution of the STNEP problem is more than BPSO and IBPSO methods.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Improved Advanced BPSO, Complex Optimization, Uncertainty in Demand.


go to top Transmission Loss Cost Allocation Using Game Theory in Multilateral Framework
         by M. Murali, P. Sridivya M. Sailaja Kumari, M. Sydulu

        Vol. 7. n. 4, pp. 5196-5203


Abstract - The present deregulated electricity industry has evolved into a distributed and competitive industry in which market forces drive the price of electricity and reduce the net cost of electricity. However the competitions in these markets require identification of the use of transmission networks, mainly the participation of utilities in losses caused in the transmission lines. This is because the consumers pay for their actual consumption where as generators are paid for their generation plus losses. Hence the loss cost allocation is of great importance as it should be allocated efficiently to both consumers and producers (both network users). Thus loss cost allocation in competitive electricity market requires a fair and efficient method with right economic signals. In this paper, loss cost allocation methodologies are presented in multilateral transaction frame work. Methodologies in cooperative game theory such as nucleolus, shapely and proportional nucleolus are presented. These are compared with conventional methods for loss allocation. Among all the methods presented, the proportional nucleolus is proved to be the efficient method with right economic signals. All the methods are implemented and results are compared for IEEE 14 bus, New England 39 bus and 75 bus Indian Power System.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Cooperative Game Theory, Deregulated Electricity Market, Loss Cost, Multilateral Transaction, Nucleolus, Proportional Nucleolus, Shapely.


go to top Real Coded Genetic Algorithm Based Method for Dynamic Available Transfer Capability Evaluation
         by A. Srinivasan, B. Dineshkumar, P. Venkatesh

        Vol. 7. n. 4, pp. 5204-5212


Abstract - This paper presents the application of real coded genetic algorithm (RGA) in determining dynamic available transfer capability (D-ATC) for the bilateral and multilateral transactions carried out in an electricity market of open transmission access. In the deregulated electricity environment of open transmission access, the transmission system may reach the oscillatory stability limit due to the increased transaction; hence it is important to consider the oscillatory stability limit related to the occurrence of Hopf bifurcation while determining the available transfer capability. In general, Hopf bifurcation produces limit cycles leading to oscillatory problems and possible instabilities to the system. In this paper, ATC is computed by finding the optimal loading very close to the occurrence of Hopf bifurcation using real coded genetic algorithm for the bilateral and multilateral transactions taken in the WSCC 3-machine 9-bus system and New England 10-machine 39-bus system.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Available Transfer Capability, Deregulation, Eigenvalue, Hopf Bifurcation, Real Coded Genetic Algorithm.



go to top Application of Fuzzy C-Means Clustering Approach and Genetic Algorithm to Partial Discharge Pattern Recognition
         by Wen-Yeau Chang

        Vol. 7. n. 4, pp. 5213-5220


Abstract - The applications of fuzzy c-means (FCM) clustering approach and genetic algorithm (GA) to recognize partial discharge (PD) patterns of high-voltage electrical apparatus are proposed in this paper. The PD patterns are collected by a PD detecting system in the laboratory. Several statistical methods are used on the phase-related distributions in this paper to extract the features for clustering. After the feature extraction procedure, we employ GA for selection of optimal feature combination. Based on the optimal features selected by GA, the PD pattern represented by feature vectors are clustered through the FCM scheme with reasonable discrimination. To verify the proposed approach, experiments were conducted to demonstrate the field-test PD pattern recognition of two kinds of models with artificial defects are purposely created to produce the common PD activities of insulators by using feature vectors of field-test PD patterns. It has been shown that through the features extraction and optimal vector selection procedure, the extracted statistical featuring vectors can significantly reduce the size of the PD pattern database. Also, the FCM based PD pattern recognition scheme is very effective for recognizing the defects of high-voltage electrical apparatus.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Fuzzy C-Means Clustering Approach, Genetic Algorithm, Partial Discharge, Pattern Recognition, High-Voltage Electrical Apparatus.


go to top Three Measuring Points for Partial Discharge Location in Energized Covered-Conductor Overhead Distribution Lines: Algorithm and Experimental Evaluation
         by Muzamir Isa, Nagy I. Elkalashy, Ghulam M. Hashmi, M. Shafiq, Matti Lehtonen

        Vol. 7. n. 4, pp. 5221-5229


Abstract - The experimental evaluation of Rogowski coil performance for locating partial discharge (PD) in energized covered-conductor (CC) overhead lines is performed. A multi-end measuring point is introduced, where the Rogowski coils looped around the CC line at three different locations and connected to the oscilloscope for measurements. The tests are carried out concerning different measurement conditions such as off-line and on-line PD measuring systems. For off-line measurements, the calibrator pulse is used to inject PD source to the CC overhead lines. Meanwhile for on-line measurement, CC line is energized by a 110/20 kV power transformer and the concept of twisted-coil around the CC is introduced in order to produce a pulse similar to the PD source. The performance of Rogowski coil is tested in noisy environment. Chirp detector is used as a signal processing tool to extract the high frequency signals in order to determine the time of arrival (TOA) signals at each measuring sensors. The locator function algorithm for multi-end measurement is developed. The results obtained from this work confirm the capability of the Rogowski coil to measure and locate the high frequency PD source on the CC line in consistent with energizing AC source. Meanwhile, using the locator function algorithm developed, the localization of PD source point on CC overhead lines is found out without the need to know the propagation velocity of the signals.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Partial Discharge, Rogowski Coil, Overhead Covered-Conductor, Distribution Network, PD Sensors.


go to top Surface Streamer Characteristics in Air Based on Plasmochemical Model
         by Jian Shi, Qing Yang, Wenxia Sima, Tao Yuan, Qingjun Peng

        Vol. 7. n. 4, pp. 5230-5239


Abstract - Surface streamer is divided into two phases in this paper, i.e., propagation in air and along insulator surface. The microscopic essence of a streamer discharge is revealed and investigated with a detailed self-consistent plasmochemical model based on particles chemical reactions and hydrodynamics. The continuity equations of electron, positive ions, and negative ions are coupled with Poisson’s equation and chemical reactions describe the impact ionization, charge transportation, electron-ion recombination, ion-ion recombination, electron attachment, neutral particles evolvement. The decisive effect of electron mean energy distribution on local characteristics of streamer discharge, such as the effect on the rate of particle collision by electrons, is investigated. The results turn out that the ionization mainly takes place at streamer head where a relative big electron mean energy exists. Electric field distribution and streamer velocities are calculated and analyzed. The effect of O2 on streamer discharge is much bigger than that of N2, due to the first ionization energy of oxygen is much smaller than that of nitrogen. The number densities and production/destruction rates of electrons and O2+, which respectively constitute the main proportion of negative and positive charges, almost have the same distribution and are both one order of magnitude bigger than those of N2+.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Surface Streamer, Plasmochemical Model, Hydrodynamics, Continuity Equation, Electron Mean Energy Distribution.


go to top Multiple SVM-RFE for Feature Subset Selection in Partial Discharge Pattern Recognition
         by Ju Tang, Jiagui Tao, Xiaoxing Zhang, Fan Liu

        Vol. 7. n. 4, pp. 5240-5246


Abstract - On study of the PRPD spectrum samples produced by typical insulation defects in Gas Insulated Switchgear (GIS), a group of fifteen statistical features are calculated to describe the PD characteristics. All the input features are reordered through the support vector machine recursive feature elimination (SVM-RFE) method, and the optimal feature subset is selected, with cross-validation and grid search introduced to improve SVM adaptive and classification accuracy. The results indicate the validity on majority types of defects recognition except for a little mistake on viod in spacer. In addition, we also find that the SVM classifier input with only nine optimum features can obtain a better diagnosis performance than choosing all the calculated features as the input vectors.

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Keywords: PD, Feature Extraction, Ultra High Frequency, SVM-RFE, Recognition.


go to top Anticipative Control Strategy for Load Commutation of On-Board Electrical Networks
         by Pedro Kvieska, Guy Lebret, Mourad Aït-Ahmed

        Vol. 7. n. 4, pp. 5247-5256


Abstract - This paper deals with the control of the output voltage of ship on-board electrical networks when a load is connected to or disconnected from the network. In some cases this kind of disturbances can create high deviations from the nominal behavior. This includes high oscillations which can damage the network and that a classical controller cannot efficiently attenuate. The idea is to take advantage of the knowledge that an electrical device is switched on, to anticipate the disturbance. An anticipative adaptive optimal control law is tuned to create better conditions to attenuate the disturbance.

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Electrical Embedded Network, Optimal Control, Anticipative Control, Load Commutation.



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