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Electric Power Applications, IEE Proceedings -

Issue 4 • Date Jul 1996

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Displaying Results 1 - 8 of 8
  • Novel topologies of AC choppers

    Publication Year: 1996 , Page(s): 323 - 330
    Cited by:  Papers (27)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    Novel topologies of pulse-width modulated (PWM) AC choppers for single-phase and three-phase systems are proposed for buck, boost and buck-boost types. A PWM AC chopper has important advantages compared with the phase-controlled AC controller using thyristors. The AC chopper has sinusoidal current waveforms, better power factor, faster dynamics, and smaller input/output filter. In an improved topology for AC choppers, an RC bypass snubber is used for minimising high-voltage spikes during the dead time in the gating signals of complementary switches. In the proposed topologies the commutation problem causing high-voltage spikes is resolved by intelligent gate-switching patterns using information from the input/output voltage. These switching patterns provide a current path for all operation modes without any RC bypass snubbers. Since RC bypass snubbers causing power loss are eliminated, the efficiency of the chopper is increased. Thus, advantages of the proposed topologies include increased power factor, low harmonic input current, fast dynamics, high efficiency, high reliability, high power capacity, and small size of the passive filter. The paper describes the operational principle and analysis of the proposed topologies. Experimental results show that the proposed topologies give good performance for AC choppers View full abstract»

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  • Predicting performance of three-phase induction motors connected to single-phase supplies

    Publication Year: 1996 , Page(s): 339 - 344
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The paper presents an algorithmic method to give an optimum run-up characteristic of operating a three-phase induction motor from a single-phase supply. Based on the accepted level of unbalance factor, the author predicts optimum speed for the change over from the starting to loading part of characteristic View full abstract»

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  • Representation of hysteresis in three-phase transformer models for electromagnetic transients

    Publication Year: 1996 , Page(s): 331 - 338
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    An efficient algorithm for the implementation of hysteresis effect in three phase transformer models for electromagnetic transient studies is presented. It is based on a simplification of the well-known Preisach model requiring few data, easily available, while it provides results close to the experimental ones. The model is validated by comparing measured and calculated results obtained from tests on a magnetic material used for the construction of transformer cores and a laboratory three-phase transformer View full abstract»

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  • Practical evaluation of different modulation techniques for current-controlled voltage source inverters

    Publication Year: 1996 , Page(s): 301 - 306
    Cited by:  Papers (18)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The quality of the current waveform generated by a current-controlled, voltage source inverter, depends basically on three factors: (a) the switching frequency of the PWM modulator; (b) the type of current waveform being generated; and (c) the modulation method used. In the paper, three modulation methods, whose characteristics are their simplicity, are analysed: periodical sampling control, hysteresis band control, and triangular carrier control. These three methods have been tested with three different waveform templates: sinusoidal, quasisquare and rectifier compensation current. They are compared in terms of the harmonic content and distortion at the same switching frequency. The paper shows that for sinusoidal current generation, the best method is the triangular carrier, followed by the hysteresis band and the periodical sampling. However, for the other two types of reference templates, the analysis showed that, depending on external factors such as inverter inductance, type of load, or delays in the PWM switching signals, one strategy may be better than the others. The paper shows that each control method is affected in a different way by the switching time delays present in the driving circuitry and in the power semiconductors. The results are analysed and compared, with the help of computer simulations and experimental results View full abstract»

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  • Simulation of three-phase loaded matrix converter

    Publication Year: 1996 , Page(s): 294 - 300
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The theory of the three-phase to three-phase matrix converter is dealt with and its switching angles equations are presented. Matrix converter operation is based on the calculated switching angles. Modelling and numerical simulations of a converter loaded with passive (R, L) and active (induction motor) loads are performed. Simulation results are presented View full abstract»

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  • Investigation into optimising high switching frequency regular sampled PWM control for drives and static power converters

    Publication Year: 1996 , Page(s): 281 - 293
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2152 KB)  

    A new high switching frequency regular sampled PWM control technique is presented, which significantly reduces the number of calculations required to generate PWM control in real-time. It is shown that this new PWM technique greatly simplifies the microprocessor software implementation, thereby considerably reducing the on-line computing requirements, and thus allows significantly higher switching frequency PWM to be generated using microprocessor techniques. Moreover, it is confirmed using both simulation and experimental results that this reduction in the computational burden does not significantly increase the harmonic distortion. Finally, it is shown that the new regular sampled PWM technique can he described and generated using both the conventional `per-phase' and `space-vector' techniques View full abstract»

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  • Operation control of paralleled three-phase battery energy storage system

    Publication Year: 1996 , Page(s): 317 - 322
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    Parallel operation for capacity enlargement of a three-phase battery energy storage system (3φ BESS) is presented. The proposed paralleled system consists of some inner-loop parallel-connected current-regulated pulse width modulated (CRPWM) converters, a current command distributor and an outer-loop common controller. Every single-module CRPWM 3φ converter possesses good current tracking control characteristics, so is easy to parallel connect. The proposed current command distributor receives current commands from the common controller and generates suitable current commands for each paralleled converter module according to the proposed current sharing control strategy. The sophisticated system arrangement of the common controller gives the BESS many power processing functions. When it is connected to the utility grid, it can be arranged to give peak load shaving, active power filtering, power factor and battery charging. In the event of utility failure the BESS can supply uninterrupted power with low distortion sinusoidal voltage waveform to critical loads. Performance of the proposed paralleled BESS at various operating conditions is demonstrated experimentally View full abstract»

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  • Online rescheduling of mass rapid transit systems: fuzzy expert system approach

    Publication Year: 1996 , Page(s): 307 - 316
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    The paper is concerned with the online rescheduling of mass rapid transit (MRT) trains after sudden increases of passenger flow. In particular, the use of predictive fuzzy control for carrying out the train dwell-time control in an event-driven framework is considered. Two fuzzy expert systems for improving the performance of MRT systems and for enhancing functions of the typical automatic train control (ATC) systems are proposed. Using the event-driven approach, the only decisions to be made in each of the two fuzzy expert systems will be whether or not to dispatch the train at a proposed reschedule time. Due to its simplicity, the proposed methodology is fast enough for online implementation. An object-oriented environment has been developed for implementing the control and simulation algorithms that reduces the efforts required for understanding the interactive operation of railway subsystems and for preparing study data. Therefore, the efforts for future development will be reduced. The proposed approach is used for adjusting the train dwell time and for studying the effects on the MRT performance. Results show that the train dwell time adjustment is an effective means of maintaining the quality of train service after sudden load disturbances. Several simulated case studies are included to illustrate the effectiveness of the proposed approach View full abstract»

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