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Home>Products>Journal and Reviews>I.R.E.E.>Latest issue
International Review of Electrical Engineering - December 2008 - Papers
International Review of Electrical Engineering - Papers
by J. Y. Madouh, T. H. Abdelhamid Vol. 3. n. 6, pp. 938-944
Abstract - Multilevel inverters supplied from equal and constant dc sources are almost don’t exist in the practical applications, even if sources are nominally equal. This paper proposes an advanced configuration of multilevel inverters having the least number of switching devices, and operating from non-equal dc voltage sources. The new configuration can be adapted to any required number of levels. The paper focuses on a three-phase five-level inverter. Output voltage control is achieved through controlling the switching angles of the inverter while eliminating the dominant line harmonics. The switching angles of the inverter are obtained by solving the relevant equations using the theory of resultant which produces all possible solutions. These sets of solutions are examined for its corresponding THD in order to select the set which generate the lowest harmonic distortion. Both computational and simulation work are carried out and experimentally validated. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Multilevel inverters, Pulse-width Modulation, Harmonic Elimination, Power Quality.
Vol. 3. n. 6, pp. 945-954
Abstract - In this paper, a simple method to design the current sharing loop, together with the feedback loop, is presented for two DC-DC converter modules paralleled. First of all, the proposed current sharing loop is described in details. Next, in order to design the parameters of the voltage controller based on the given crossover frequency and phase margin, the corresponding small-signal model is introduced. According to the proposed current sharing loop, such a small-signal model can be easily figured out. Finally, some experimental results, together with some simulated results, are provided to verify the effectiveness of the proposed method. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Current sharing loop, modules paralleled, crossover frequency, phase margin, small-signal model.
Vol. 3. n. 6, pp. 955-961
Abstract - The paper presents a simple design modification for any conventional SRM to considerably minimize its copper and iron losses without sacrificing any of its advantages. The paper applies this modification on a 6/8 three phase conventional SRM. The stator teeth of each phase are brought closer together in order to increase the flux density via minimization of the flux path length. The reduction in the copper losses occur due to a reduction in the volume of the copper required to yield the same amount of the output torque, in comparison to the conventional 6/8 SRM. The reduction in the iron losses occur because each phase winding becomes incorporated in only one magnetic circuit thus eliminating the reversal of the current, reducing the flux path length, and reducing the frequency. Utilizing this design approach, introduces an efficient switched reluctance motor that has a substantially improved performance in terms of copper and iron losses, electromagnetic torque production, and efficiency. The analysis and comparison of the SRM before and after the design modification are presented in the following. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Finite element, MATLAB/Simulink, maximizing output torque, minimizing losses, near stator teeth, switched reluctance motor, short flux path.
Vol. 3. n. 6, pp. 962-974
Abstract - The speed control at large range for wound-rotor induction machines can be implemented by using different vector based methods from either or both the stator and the rotor side. One of these is to apply voltage with slip frequency on rotor windings through the rings. But, throughout the application, dangerous effects on the machine dynamics occur when effective value of the voltage applied on rotor windings is not adjusted by any intelligent control system especially at the application moment. In this study, firstly, the effects on the instantaneous rotor current and induced torque waveforms throughout the voltage injecting in the rotor windings are examined by simulations and experiments. Afterwards, the determined transient and harmful effects on the mentioned dynamics are tried to reduce by the fuzzy logic based control system using DSP. For the experimental studies, an IGBT inverter fed by DC link converter in rotor side is designed and employed. Thus, power converter rating is reduced. In the control system, TMS320F2812 DSP is used together with fuzzy logic based space vector pulse width modulated (SVPWM) inverter in order to control of amplitude and frequency of the injected voltage with same phase in accordance with the voltage induced in rotor circuit. The power flow between rotor windings and system in which stator side is directly connected to the grid is analyzed at different operation mode. A large range speed controller system with power recovery drive is implemented not only braking in regenerative region but holding the speed at the reference under unexpected load condition changing suddenly as well. For simulation studies, a C/C++ algorithm is developed in order to predict the performance of proposed model and results supported by experimental studies are presented and discussed. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Voltage Injection, Fuzzy Logic, Speed Control with Power Recovery, F2812 DSP.
Vol. 3. n. 6, pp. 975-981
Abstract - The present work introduces a new filtering technique of electrical signals in indirect vector control drive. The filter is of resonating type and centre frequency is locked to the dominant frequency of the signals under consideration to create zero phase shift at that frequency. The filters are able to mitigate unwanted noise due to inverter switching and discrete computation. The filtered signals are utilized to estimate online the rotor resistance directly without using any observer and the response time of estimation is within order of second. The method is verified by simulation and experiment. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Synchronous filters, indirect vector control, online estimation, rotor resistance, SVPWM.
Vol. 3. n. 6, pp. 982-988
Abstract - This paper presents field reliability analysis to estimate the failure rate and remaining life of old DC traction motors for electric railcars. The analysis includes life data collection, distribution analysis to select a life distribution to use for modeling the life data, and estimation of the failure rate and remaining life. The life data are collected from field maintenance records, which consist of the time-to-end data of rotors and stators ranging in age from 18 to 30 years. A distribution analysis makes it clear that three-parameter Weibull distributions fit the life data, and Weibull shape parameters are greater than 1.0, showing an increasing failure rate caused by wear with age. The remaining life of the units reaching a specific age is estimated by the remaining life distributions, which are derived in the form of a conditional three-parameter Weibull distribution. Calculation methods are provided for reliability criteria to evaluate the remaining life: the failure rate, the expected remaining life, and the chance of failure before the next overhaul. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: DC Traction Motor, Field Life Data, Failure Rate, Remaining Life.
Vol. 3. n. 6, pp. 989-998
Abstract - It is generally accepted that reactive power (or Var) compensation will bring benefits for utilities and industrial customers by providing local voltage and power factor support. However, there is a lack of a systematic approach to quantitatively identify the economic benefit. In addition, with deregulation and restructuring, it is important to indicate the amount of benefit that each market participant may potentially receive given the right price signals. If such information can be easily obtained and presented, it will be more convenient for decision-markers to determine the cost benefit sharing of installing a Var compensator. The vision of this paper is to lay out a possible method for quantitatively evaluating the benefits from local reactive power compensation. The approach is to quantify the benefits into several categories such as reduced losses, shifting reactive power flow to real power flow, and increased transfer. The calculation of these benefits are illustrated with a simple two-bus power system model and then presented with a more complicated model using Optimal Power Flow to calculate the benefits. Simulation on the more complex system is conducted with seven buses in two areas. The simulation results show that the possible economic benefits can be significant, if compared with capacity payments to central generators or payment of power factor penalties applied by utilities. The potential economic value of local Var compensation may give various parties in electricity supply, delivery and end-use consumption a better understanding of the Var benefits to assist their cost-benefit analysis for Var compensation installation. Sensitivity analysis is also provided to illustrate that the benefits may not be monotonically increasing. Also, this paper suggests that the future reactive power market should consider local Var providers or other way to encourage load Var capability, since local Var benefit is significant. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: reactive power, Var compensation, economic benefits, transfer capability.
Vol. 3. n. 6, pp. 999-1003
Abstract - Current harmonic distortion is quite usual in industrial mains. Electromagnetic compatibility of circuit breakers must comply with these conditions. Current releases of circuit breakers were adjusted to sinusoidal current waveform in past. Modern circuit breakers have to disconnect current with high harmonic content and their current releases have to dispatch the releasing impulse with respect to the usual current distortion, too. Therefore the release testing procedure is performed with a test current waveform that is defined by standards. In the paper new current generator for testing of releases and circuit breaker for both low and very high current is described. The circuit breaker disconnects usually a current, the waveform of which is not sinusoidal. Therefore the test current waveform, at which the release must disconnect the circuit breaker or must not disconnect it, is given by standards. The described current generator fulfils these by standard given demands. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Circuit Breaker, Breaker Testing, Current Release, Current Distortion.
Vol. 3. n. 6, pp. 1004-1014
Abstract - This paper introduces the power flow control strategy of a hybrid distributed generation system includes solid oxide fuel cell and battery energy storage during the voltage disturbances in distribution systems. The proposed control strategy allows the hybrid distributed generation system operate properly during the occurring the voltage sags in distribution systems. Because it becomes unacceptable to disconnect generating units every time a disturbance occurs, as was common practice in the past. Hence, control structure design, and simulation study of a hybrid distributed generation system are investigated. Simulation results are given to show the overall system performance including active power control and voltage sag ride-through capability of the hybrid distributed generation system. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Battery Energy Storage, Control, Hybrid Distributed Generation, Power Flow, Solid Oxide Fuel Cell, Voltage Sag.
Vol. 3. n. 6, pp. 1015-1023
Abstract - Improving power systems transfer capability, voltage level control, damping electromechanical power oscillations and reducing transient swings becomes a great concern for national and/or private energy companies. Around the word, in particular in emerging countries, energy demand is in very fast growth. Developments of conventional and renewable energy production sources follow closely such fast increase in energy absorption. But, in general, developments in transmission lines and in hard and software control equipments are well delayed which implies a dangerous gap between the demand and the transmission capacity. Failures can give rise to power oscillation, voltage drop and high frequency deviations; resulting in system integrity rapid collapse by transient stability mechanism. New technology alternatives as FACTS can positively support conventional control systems as PSSs, AVRs and TGs .The paper deals with this problem and aims to show that UPFC is a suitable device in particular to reinforce variable wind energy penetration in the power system. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power systems, Transfer capability, Voltage control, Wind energy, Unified power flow controller, Injection model.
Vol. 3. n. 6, pp. 1024-1031
Abstract - This paper presents an approach to relieve the transient stability constraint in deregulated power systems. Depending on different market policies adopted, in a power system congested with the transient stability limits, the method relieves the constraint of transient stability while maximizing the realizable bilateral contracts or minimizing the rescheduling in pool market. Transient Energy Function (TEF) method is used to calculate the sensitivity of energy margin to the generations and loads. The effectiveness of the method is illustrated by case studies on Western System Coordinating Council (WSCC) 3-machine 9-bus power system and the results are verified by time domain simulations. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Dynamic Security Assessment, Transient Energy Function, Electricity Market, Power System Deregulation, Preventive Action.
Vol. 3. n. 6, pp. 1032-1038
Abstract - TAccurate models are not routinely available and most industrial plant engineers have no idea as to the statistical nature of the external disturbances impinging on their plant. In this paper, a finite time controller is proposed for double integrator system when a disturbance impinges on the system. In the other hand, due to an increasing demand for electrical power in recent years, there is a huge interest in operating the power system near the edge of its stability boundary. When a periodic load perturbation occurs, complicated chaotic oscillations will be observed. In these conditions, power system comes into transient state and may lead to instability. The proposed control law is utilized to control chaotic oscillations in a simple interconnected power system. Simulation results are implemented to verify the proposed control strategy. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Finite time stabilization, Disturbance rejection, Swing system, Chaotic oscillations.
Vol. 3. n. 6, pp. 1039-1047
Abstract - It
presents the essential aspects regarding the modelling and EMTP
simulating of the characteristics of the orthogonal magnetising
controlled reactor (CROMAG) and of the multiple non-linear and
parametric resonance phenomena in oscillating circuits with a CROMAG.
The base states of these electromagnetic devices are then simulated on
the computer. The paper contains the obtained results through the
numerical simulation in the EMTP software. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: non-linear reactor, orthogonal magnetising controlled reactor, multiple non-linear resonance phenomena.
Vol. 3. n. 6, pp. 1048-1053
Abstract - Silicon integrated circuit spiral inductors and transformers are finding wide ranging applications in RF circuits. This paper presents implementation and characterization of spiral inductor using MEMS technology on silicon substrate for use in design of voltage controlled oscillator (VCO). MEMS inductors have been realized from the CMOS-compatible MEMS process. Suspended inductor has been employed in design to avoid substrate coupling. The dimensions of the inductor have been obtained using the Greenhouse formula. The inductors have been simulated using CoventorWare software. The Yue’s model has been applied to compute lumped equivalent parameters and Q factor of the inductors. The resultant value of inductance and Q factor are 2.87nH and 27 respectively at 2.4 GHz, which are in good agreement with the results of Greenhouse formula. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Spiral Inductor, inductor model, quality factor, CMOS compatible inductor, Microelectromechanical systems (MEMS).
Vol. 3. n. 6, pp. 1054-1062
Abstract - In this paper, two hybrid multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) transceiver schemes are introduced by combining the vertical Bell-labs layered space-time (V-BLAST) with Alamouti’s space-time block codes (STBC) and V-BLAST with space-frequency codes (SF), denoted V-BLAST/STBC and V-BLAST/SF respectively. The MIMO-OFDM system consists of four transmit and four receive antennas is modeled over Monte-Carlo time-variant channel model in the delay spread of 200ns and different maximum Doppler frequency. Special training sequences are used in the least square (LS) channel estimation method to obtain a desirable crest-factor of the transmitted training signal and eliminate the influence of inter-symbol interference (ISI) on the channel estimation performance. The symbol error rate (SER) performance of V-BLAST/STBC OFDM and V-BLAST/SF OFDM is analyzed. Simulation results show that the SER performance of V-BLAST/SF OFDM outperforms V-BLAST/STBC OFDM in MIMO channel model with high Doppler frequency. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Space-time block codes, Space-frequency, Inter-symbol interference, V-BLAST.
by K. E. Mohamed, B. M. Ali, S. S. Jamuar, K. Sabira, A. Ismail Vol. 3. n. 6, pp. 1063-1069
Abstract - In this paper, SDR Digital Control System (SDR-DCS) has been developed to perform the multi standard protocol for the handset transceiver using GSM and CDMA systems for beyond 3G. This system has been designed for SDR base band digital transceiver for the handset such that it could roam between different wireless systems. The SDR-DCS controls the download of the specific air interface environment, to the unique hardware accordingly. In order to implement the whole design in software, the design had to go through three stages. The first stage was to do all the design steps in the software using generic computing resources such as Hardware Description Language (HDL), with the top-level design for each protocol. The second stage was to define a logic circuit to perform the signal processing for each protocol; this step was applied after the simulation and synthesis, and eventually programming that circuit into the FPGA board. The third stage was to use the FPGA to implement the functions required for each protocol, which constitutes the multi-standard protocol. The Synopsys™ software has been used with combination of VHDL and Verilog languages. The simulation tools used are Model Sim and System Studio. Xilinx ISE 9.2i has been used as synthesis tool. The results of the simulated and synthesized top-level design files were downloaded into the Xilinx XSA-3S1000 FPGA board. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: SDR Digital Control System (SDR-DCS), Hardware Description Language (HDL), GSM, CDMA, FPGA.
by E. Banovac, D. Kozak Vol. 3. n. 6, pp. 1070-1076
Abstract - Lot Acceptance Sampling Plan (LASP) is an important technique in the field of statistical quality control that still remained important function in many cases - where sampling process is needful because lot sizes are large and inspection is expensive, or because inspection is destructive with high error rate and time-inspection. Theoretical characteristics of the LASP that could be used successfully for acceptance of large lots of different components purchased and installed in the electric-power industry during maintenance or overhaul are shown in this paper. Those plans are Philips, Dodge-Romig and MIL-STD 105E. Existing differences between certain Acceptance Sampling Plans are explained. Implementation of those plans for accepting the large lots of components during the Acceptance Control procedure in the electric-power industry is proposed. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Acceptable Quality Level, Lot Acceptance Sampling Plan, Quality.
Vol. 3. n. 6, pp. 1077-1086
Abstract - Vowel
recognition has been commonly used in speech recognition system for
large vocabulary continuous speech and isolated word recognition. Vowel
recognition system uses a parametric form of the vowel to get the most
important features in the signal. Thus, the main stage of vowel
recognition can be feature extraction form the vowel. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: feature extraction, Mellin transform, Modified cepstrum, Vowel recognition.
Vol. 3. n. 6, pp. 1087-1096
Abstract - The paper proposes accomplishing a new informatics system architecture, under the form of high-speed speed remote laboratory with a multitask type access on laboratory work, to remove users’ waiting lists and allow reconfiguration of electric assembling in real time. The accomplished project was preceded by a thoroughly analysis of didactic requests according to economic problems, so that, the following aspects would be solved: Students will access from the distance real instruments and will accomplish online test workbench, in the idea of understanding all the aspects of a real experiment (including possible flaws). Detected errors in prescribing the commands towards the machine will not be corrected automatically, but the student will be warned. The results of the tests will be supplied by the user in the same way the real instrument does. Copyright © 2008 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: E-Learning System, Virtual Instrumentation.
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