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Home>Products>Journal and Reviews>I.R.E.E.>Latest issue
International Review of Electrical Engineering October 2008 - Papers
International Review of Electrical Engineering - Papers
by M. Adam, A. Baraboi, C. Pancu, A. Plesca Vol. 3. n. 5, pp. 759-767
Abstract - The controlled switching of the circuit breakers is one of the modern techniques used for the adjustment of the transient stresses which appear at the switching processes. The paper, after a presentation of the principles for the controlled closing and opening of the circuit breakers, shows aspects regarding their controlled closing and the switching of shunt capacitor banks. The contributions regarding the controlled closing refers to the influences of: the rate of decrease of the dielectric strength (RDDS) of the space between contacts, the target instants of contacts touching and the mechanical dispersion of the operating time to the pre-arcing time, and of the pre-strike voltage at closing respectively. These are done specifications about the target moments of mechanical touching of the contacts depending on RDDS and admissible maximum mechanical dispersion in the case of controlled closing. The contributions regarding the switching capacitor banks refer to: the analysis of the optimum moments for the controlled closing in accordance with the ground connection type of the shunt capacitor; the choosing of the target points taking into consideration the dispersion of the operating time, and of the pre-arcing characteristic respectively; a case study which underlines the importance of a good choice of the optimum moments for the controlled closing. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: capacitor bank, circuit breaker, controlled switching, pre-arcing time, rate of decrease of dielectric strength (RDDS).
Vol. 3. n. 5, pp. 768-778
Abstract - Important issue for the Transmission System Operators is how to deal with older transmission assets. To ensure system reliability and security over a long time frame, Transmission System Operators should develop appropriate methodology and procedure for the power transmission assets revitalization or replacement. This paper describes one approach to prioritize transmission lines and transformers for revitalization according to the predefined criteria based on an asset condition and its importance within a power system. Example of the prioritization procedure is given in the paper. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: System reliability and security, Transmission assets, Revitalization, Prioritization.
Vol. 3. n. 5, pp. 779-787
Abstract - This paper presents the operation of a static compensator (StatCom) which is controlled by a time-optimal current controller. The control algorithm enables a fast and optimized transient response at the constant switching frequency of the device. The performance is limited only by its output voltage rating. The main idea behind the time-optimal current control is to find such control voltage that enables us to reach current reference values in minimum time. The algorithm is derived from the StatCom mathematical model in α-β coordinates and is tested by means of simulations using the StatCom mathematical model and a detailed model. The performance of the control algorithm is validated for reference current tracking and balanced and unbalanced network voltage sags. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Current Control, Flexible AC Transmission Systems, StatCom, Voltage Source Converter.
Vol. 3. n. 5, pp. 788-794
Abstract - Nowadays the power systems are often, connected together and supplied from multi points to increase the reliability of whole system. Therefore the flickers produced by different flicker sources propagate throw the whole system. Thus the measured flicker level at the point of a linear load is a result of contribution from a number of different flicker sources. In a mitigation process it is essential to know which one of the flicker sources is the dominant one. This paper proposes a method to determine the flicker propagations and trace the flicker sources in a multi-source power system and describes how flicker sources affect on a linear load and which one of them is dominant. To evaluate the proposed method, simulation results on a network are presented. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Flicker, flicker source, dominant flicker source, power quality.
Vol. 3. n. 5, pp. 795-802
Abstract - Distributed energy (DE) resources are power sources located near load centers and equipped with power electronics converters to interface with the grid, therefore it is feasible for DE to provide reactive power (along with active power) locally for dynamic voltage regulation. In this paper, a synchronous condenser and a DE source with an inverter interface are implemented in parallel in a distribution system to regulate the local voltage. Developed voltage control schemes for the inverter and the synchronous condenser are presented. Experimental results show that both the inverter and the synchronous condenser can regulate the local voltage instantaneously although the dynamic response of the inverter is much faster than the synchronous condenser. In a system with multiple DEs performing local voltage regulation, the interaction of multiple DE at different locations under different load levels may have an impact to the control parameter setting for each individual DE control system. Future research is needed to find out the interaction of DEs to identify the optimal control parameter settings with the consideration of many factors such as system configuration, load variation, and so on. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Distributed energy resources, instantaneous power theory, PI control, power electronic interface, voltage regulation.
Vol. 3. n. 5, pp. 803-810
Abstract - This paper presents a new algorithm for precise fault location in transmission lines based on the parallel process of a novel Complex Least Error Squares (CLES) and Adaptive Linear Neural Networks (ADALINE). The fault location is based on direct estimation of symmetrical components by a novel Complex Least Error Squares (CLES) filter, introduced in this paper. The function of ADALINE is to estimate the fault location directly from time domain positive sequence components of only one end of transmission lines. The proposed algorithm is evaluated by presenting a number of simulations in PSCAD/EMTDC and MATLAB software. The obtained results clearly show that this technique is highly robust and very accurate. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Artificial Neural Networks, Least Error Squares, One End Fault Location, Power Systems Protection.
Vol. 3. n. 5, pp. 811-819
Abstract - In this paper, we propose a universal control strategy of the advanced UPFC that joins shunt active filtering, flicker compensation and system balancing capabilities to real time power flow control into one device. To achieve optimal UPFC behavior in the different mode, the injected voltages and currents are determined on-line based on the local instantaneous measurements. The controller should monitor the system conditions and generate the appropriate injected voltages and currents for each phase and for each time step. The control algorithm compensates the oscillated part of the instantaneous active and reactive power components to achieve the harmonics and flicker compensations. This approach is based on the symmetrical components theory in instantaneous state. The implementation of the method is completely digital, thus, the number of acquired signals and the external analog circuitry are reduced to minimum. The UPFC and a typical unbalance and non-linear loads have been implemented in digital simulator to demonstrate the capabilities of the UPFC to compensate system disturbances. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power quality, Instantaneous power, UPFC, FACTS, harmonics, Flicker, active filter and real time control.
Vol. 3. n. 5, pp. 820-828
Abstract - In this paper a methodology for calculation of the optimum size of a stand-alone hybrid wind/photovoltaic (wind/PV) system is developed. The collection of six months of data of wind speed, solar irradiance and ambient temperature recorded for every hour of the day were used. These data and the manufacturer’s specifications of the wind turbines and the PV modules were used to calculate the average hourly power generated by the components of the hybrid system. The mathematical modeling of the principal elements of the hybrid wind/PV system is exposed showing the main sizing variables and a deterministic algorithm is used to minimize the life cycle cost of the system while guaranteeing the satisfaction of the load demand. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Renewable energy system, Power supply, Energy storage, Modeling, Optimization.
Vol. 3. n. 5, pp. 829-836
Abstract - In this paper, a new soft switching isolated buck-boost PWM converter with active clamp circuit is proposed. The active clamp circuit in this converter not only absorbs voltage spikes across the main switch but also provides soft switching conditions for both main and auxiliary switches. All switches are PWM controlled which simplifies the control implementation. One of the main advantages of this converter is the possibility of sharing the output power between the magnetic devices and operating at high power levels while soft switching conditions exist in both buck and boost modes of converter operation. Since this converter can operate over a wide input voltage range, it can be employed in power factor correction. The experimental results obtained from a 150W prototype circuit operating at 100 kHz are presented to confirm the integrity of proposed circuit. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Active Clamp, Soft switching, PWM, Buck-Boost, flyback current fed.
Vol. 3. n. 5, pp. 837-843
Abstract - In this paper, a novel approach for designing soft switching for synchronously rectified (SR) buck converters is presented, which contains one resonant MOSFET switch, one resonant inductor, one resonant capacitor, one diode. In such a circuit, the resonant MOSFET switch can be driven by one half-bridge driver, without the problem in float driving. Besides, the resonant inductor is not connected in series with the output input, and hence there is no problem in duty cycle loss. Also, the resonant capacitor is connected in parallel with the parasitic capacitance of the MOSFET switch and hence there is a slight effect of such parasitic capacitance on the resonant behavior. Eventually, the detailed illustration of the basic operation of the proposed resonant circuit, together with some simulated and experimental results, is provided to demonstrate its effectiveness. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: SR Buck Converter, Soft Switching, Duty Cycle Loss.
Vol. 3. n. 5, pp. 844-857
Abstract - Current harmonics caused by nonlinear loads yield major power quality related problems in the utility. Such harmonics are commonly reduced by employing static compensators known as Active Power Filters (APF). APF topologies are of various types, depending on technical and economical requirements; and their performance is intimately related to the applied control algorithm. In this paper, new constant-frequency control schemes are proposed for a shunt three-phase four-leg APF. The APF is used to compensate the current distortion and the reactive power created by a typical industrial load. The elaboration of the control law is based on a state-space averaged model of the converter, computed in the (d,q,0) synchronous frame. All control schemes consist of multi-loops controllers that ensure voltage regulation at the DC side of the filter, and current wave shaping at the AC side. The control systems are implemented numerically using the Matlab/Simulink tool. The performance of the proposed control approaches is finally discussed through the obtained simulation results. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Shunt active power filters, PWM control, harmonic reduction, reactive power compensation, average modeling.
Vol. 3. n. 5, pp. 858-863
Abstract - In this paper a new soft switching bridgeless PFC circuit is presented. The proposed circuit has the benefits of low conduction losses in PFC bridgeless circuit and soft switching. In addition this converter doesn't employ any extra switch to provide soft switching. A simple controller based on Hystersis control method is presented for the proposed circuit. The simulation results justify the theoretical analysis. A prototype of the proposed PFC circuit is implemented and the experimental results are shown. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Bridgeless, Boost converter, Hystersis control, Power Factor Correction (PFC), Soft switching.
Vol. 3. n. 5, pp. 864-873
Abstract - In more-electrical aircraft and embedded electrical networks, many front-stage converters are dedicated to supply actuators. The front stage of such applications is classically a low cost passive diode rectifier. To improve the features of this kind of rectifier, other topologies are proposed and compared. This paper compares four different AC/DC front-stage power converters to supply the voltage source inverter of an electrohydrostatic actuator (EHA) dedicated to on-board aircraft applications. One of proposed solutions is an original synchronous and self-commutated rectifier with a natural and rapid regenerative capability. All the proposed topologies are compared to a classical diode bridge on the basis of several criteria: improvement of performances, efficiency, optimization of electrical and thermal designs and minimization of size and mass. Simulation results and calculations put forward self-commutated rectifier' capabilities concerning the Si design factor, the integration index and the power losses. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: electrical network, front stage converters, AC/DC conversion, self-commutated conversion, rating comparison, efficiency comparison.
by M. S. A. Dahidah, V. G. Agelidis Vol. 3. n. 5, pp. 874-880
Abstract - Selective harmonic elimination pulse-width modulation (SHE-PWM) technique for three-level voltage source converter is presented in this paper. It is mathematically defined using Fourier-based equations to describe the output voltage waveform. An efficient minimization technique assisted with hybrid genetic algorithm is then applied to obtain the optimal switching angles. Different operating points including single- and three-phase systems are presented to demonstrate the effectiveness of the proposed method. Selected simulation and experimentally validated results are reported to show the effectiveness of the proposed method. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Hybrid Genetic Algorithm, Optimization, PWM, Selective Harmonic Elimination (SHE), Voltage Source Converter.
by Z.Ye, P. K. Jain, P. C. Sen Vol. 3. n. 5, pp. 881-891
Abstract - The full-bridge resonant converters use various modulation schemes for different control purpose. The circuit modeling and analysis are complicated for these converters because the state variables like inductor currents and capacitor voltages are ac dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonics of interest. Correspondingly, the resonant converter is decomposed into two dc sub-circuits, the state variables of which are the time-varying Fourier coefficients of the original ac variables. Small signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A general phasor dynamic model is presented for a family of high frequency DC/AC resonant inverter system with 5 energy storage components. The advantages of this model over the other models include: 1) The mathematical model closely relates to the power converter topology in time domain, and therefore keeps the physical meaning of the state variables. The active power, reactive power, etc, can be easily defined. 2) Also the model can be easily derived from the topology in time-domain. Therefore this model can be easily extended to more complicated resonant topologies, and to include more parasitical components for higher accuracy of modeling. 3) The model can be applied to a number of modulations including phase shift modulation, frequency modulation, pulse width modulation, and pulse width modulation with minor modifications. 4) It can be used for fast simulation, circuit analysis and controller design. A resonant inverter system with 5 energy storage elements is modeled and compared with switch simulation for both steady state and transients. The simulation results match the switch simulation in both steady state and transients, but takes much less time. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Resonant converter, Modeling, Phasor domain, Simulation.
by M. Morawiec, A. Lewicki, Z. Krzeminski Vol. 3. n. 5, pp. 892-899
Abstract - Novel control structure of induction motor is proposed in this paper. The structure of multiscalar control with conventional PI – controllers is well known in literature. The sliding mode multiscalar control (SMMC) conception is presented in this paper. The induction motor is fed by voltage source inverter. Comparison between two multiscalar control method is showed. The flux and the rotor speed is estimated in the Krzeminski’s Speed Observer. The research of proposed sensorless SMMC are showed in simulations and experimental results. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Sliding mode control, Control systems, Induction motors.
Vol. 3. n. 5, pp. 900-905
Abstract - The aim of this work is to propose the hybridisation of Boundary Element Method (BEM) with Permeances Network Method (PNM) for computing linkage fields in Outer Rotor Permanents Magnets synchronous machines (OR-PMSM). One of the employed techniques is the evaluation of air-gap permeances starting for Finite Element Method (FEM) software. This approach consumes a lot of times and this is limited for design processes. In this study, a new strategy using the BEM in the air-gap permeances evaluation is presented. So the high ratio fast of running/computing errors of the proposed methodology has been checked out. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Boundary Element Method (BEM), permeances network method, outer-rotor permanent magnetic machine.
Vol. 3. n. 5, pp. 906-911
Abstract - The
demands on bearingless drive configurations concerning performance as
well as costs are high. The proposed concept of bearingless motors
consists of concentrated coils in a symmetrical arrangement, which
generate radial forces and motor torque simultaneously in interaction
with a permanent magnet excited disc shaped rotor. Owing to the
nonlinearity of the plant, the use of linear control design methods
alone is not suitable for achieving a high operation performance. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: bearingless motors, magnetic levitation, PM synchronous motor, nonlinear control systems.
Vol. 3. n. 5, pp. 912-921
Abstract - The present development of power electronic encourages to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG) for wind power generation. Among those, operation and stability analyses (both dynamic and transient) of DFIG type of VSWT have already been reported in many literatures. On the other hand, operation and stability analyses of synchronous generator type of VSWT are not sufficient enough. This paper focuses on various operations of variable speed wind turbine driving a PMSG (VSWT-PMSG), developing suitable control strategies for the frequency converter in the system. Dynamic characteristic of VSWT-PMSG is analyzed using real wind speed data measured in Hokkaido Island of Japan. Transient characteristic of VSWT-PMSG during network fault condition is also analyzed in detail for both symmetrical and unsymmetrical faults. Moreover, permanent fault due to unsuccessful reclosing is considered, which is one of the salient features of this study. Extensive simulation results are presented which verifies the effectiveness of the control strategy of VSWT-PMSG at different operating regions. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Variable speed wind turbine (VSWT), permanent magnet synchronous generator (PMSG), transient stability, dynamic stability, permanent fault, unsuccessful reclosing, pitch controller, wind generator, voltage source converter (VSC), and frequency converter.
Vol. 3. n. 5, pp. 922-930
Abstract - This paper discusses the development and implementation of wavelet-based automated mixed signal ADC testing. LabView is used in the developments of the ADC testing algorithm. By using LabView’s (automation control software) as a choice of testing mixed signal systems, testing engineers can reduce testing time and cost associated with it. The results prove that LabView can be successfully used in the automation of mixed signal system testing. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Analog-to-Digital Converters, Virtual Instruments, Effective Number of Bits, Differential Non-Linearity, Integral Non-Linearity, Full-Scale Range, and Discrete Wavelet Transform.
Vol. 3. n. 5, pp. 931-937
Abstract - This paper presents the design of an ultra-wideband CMOS VCO with tuning range of 3.8~7.4GHz, using a modified tunable active inductor (TAI) in a 0.18um CMOS technology. The inductance of TAI, with nearly a quality factor of 90, can be tuned from 0.34 to 0.61nH. The power dissipation is about 29mW and phase noise is -92dBc/Hz. PLL-based and LC-based phase noise reduction techniques are examined, reducing the phase noise by 1dBc/Hz and 3dBc/Hz, respectively. Monte Carlo simulations illustrate the robustness of the oscillator performance under reduced bias voltage, temperature change, and process variations. Finally, the effect of packaging is investigated through simulations and modeling of pad and bonding wire, which show that only the upper frequency capability is degraded by 6% while the phase noise will experience slight improvement. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Ultra wideband, Active inductor, Tuning range, Voltage controlled oscillator.
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