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Online ISSN 1751-8679 Print ISSN 1751-8660

IET Electric Power Applications

Volume 5, Issue 3, March 2011

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Volume 5, Issue 3

March 2011

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Editorial

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    • Capacitor energising transient limiter for mitigating capacitor switch-on transients
      • Author(s): S.-T. Tseng  and  J.-F. Chen
      • Source: IET Electric Power Applications, Volume 5, Issue 3, p. 260 –266
      • DOI:  10.1049/iet-epa.2010.0131
      • Type: Article
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      • p. 260 –266 (7)
        Capacitors are prone to two major types of energising transient phenomenon: transient overvoltage and inrush current (charging current). Energising transients will shorten the lifetime of the capacitor, and furthermore they will damage the contacts of the switching device. This study proposes a rectifier type capacitor energising transient limiter (CETL) for mitigating the isolated capacitor and back-to-back capacitor switch-on transients. The operating condition of the proposed circuit can be divided into two states: the charging suppressive mode and the steady state with its initial transient. During the charging suppressive mode, a pair of diode strings conducts automatically and then the DC reactor provides high impedance at the instant of switching on in order to suppress the capacitor energising transients. During the steady state with its initial transient, all diodes of the bridge rectifier conduct simultaneously and the limiter freewheels; therefore the limiter acts as a short circuit and has no effect. Thus, it is not necessary to increase the capacitor-rated voltage when the CETL is used. In this study, experiments and simulations are carried out to demonstrate the feasibility of the proposed limiter circuit.
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      Measurement method for online battery early faults precaution in uninterrupted power supply system
      • Author(s): J.-C. Hwang ; J.-C. Chen ; J.-S. Pan ; Y.-C. Huang
      • Source: IET Electric Power Applications, Volume 5, Issue 3, p. 267 –274
      • DOI:  10.1049/iet-epa.2010.0043
      • Type: Article
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      • p. 267 –274 (8)
        There have been many studies written about the methods used to determine the health of batteries in offline application. This study intends to apply the voltage tracing method to produce a simple method in determining the early faults of online battery. The results showed that by using the voltage tracing method, it is possible to find the early faults of batteries, which in turn can prevent power supply interruption and help the telecommunication industry in providing reliable communication services.
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      Improved predictive current control for unbalanced stand-alone doubly-fed induction generator-based wind power systems
      • Author(s): V.-T. Phan  and  H.-H. Lee
      • Source: IET Electric Power Applications, Volume 5, Issue 3, p. 275 –287
      • DOI:  10.1049/iet-epa.2010.0107
      • Type: Article
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      • p. 275 –287 (13)
        This study proposes an improved predictive current control (PCC) strategy for unbalanced stand-alone doubly-fed induction generator (DFIG)-based wind power systems. The proposed control scheme predicts an appropriate average rotor voltage vector in next switching period to eliminate the rotor current errors in the following control period. The identified voltage vector sequence is then applied to the rotor-side converter (RSC) by using space-vector modulation with constant switching frequency. To increase the control accuracy, a proposed compensation method for the control time delay inherent in the digital implementation, mainly due to the sampling and calculation processes, is adopted. The whole control algorithm is performed in the RSC to achieve the desired control output, that is, compensation for the stator voltage imbalance. In addition, the effect of parameter variation on the performance of the control scheme is also considered. The proposed PCC method was tested by both simulations and experiments with 2.2 kW DFIG feeding an unbalanced load to demonstrate the excellent steady-state performance as well as the extremely fast dynamic response of the proposed current controller.
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      Mono inverter multi-parallel permanent magnet synchronous motor: structure and control strategy
      • Author(s): D. Bidart ; M. Pietrzak-David ; P. Maussion ; M. Fadel
      • Source: IET Electric Power Applications, Volume 5, Issue 3, p. 288 –294
      • DOI:  10.1049/iet-epa.2010.0180
      • Type: Article
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      • p. 288 –294 (7)
        This study presents a new and original Mono inverter multi-parallel permanent magnet synchronous motor (PMSM) system. To obtain the stability of such a system, each of the motor synchronisms should always be respected regardless of their load torque. In this case, only one motor, called ‘master motor’, will be self-piloted. If the chosen master motor is the one with the highest applied load torque, synchronism is respected for each of the motors. To find this machine, a solution that compares the rotor positions is thus developed. Experimental results are given for a system with two PMSM plugged in parallel. The proposed solution can, however, be applied to systems whatever the motor numbers; therefore additional simulations are provided for a four-PMSM system.
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      Adaptive supervisory Gaussian-cerebellar model articulation controller for direct torque control induction motor drive
      • Author(s): S.-Y. Wang ; C.-L. Tseng ; C.-C. Yeh
      • Source: IET Electric Power Applications, Volume 5, Issue 3, p. 295 –306
      • DOI:  10.1049/iet-epa.2010.0038
      • Type: Article
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      • p. 295 –306 (12)
        This study develops an adaptive supervisory Gaussian-cerebellar model articulation controller (ASGCMAC) and implements it in a sensor-less direct torque control (DTC) system for controlling induction motor speed. The inherent uncertainties of a DTC system, including parametric uncertainties and the uncertainties in external load torque, make control tasks difficult. A model-free approach, ASGCMAC, is adopted to build a high-performance DTC induction motor drive. The proposed method comprises two parts – a supervisory controller and a Gaussian-CMAC (GCMAC) subsystem. The supervisory controller monitors the control process to maintain the tracking error within a pre-defined range; the GCMAC sub-system learns and approximates system dynamics. The parameters of ASGCMAC are adjusted online according to adaptive rules, which are derived from Lyapunov stability theory, guarantee system stability. Four control schemes, ASGCMAC, supervisory controller, proportional-integral (PI) control and conventional CMAC, are experimentally investigated and the performance index, root-mean-square error (RMSE), is evaluated in each scheme. The results reveal that ASGCMAC outperforms the other comparison schemes. In addition, the robustness of the proposed scheme to the parameter variation and external load torque disturbance has been verified via simulation and experiments.
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      Operating points estimation of three-phase induction machines using a torque–speed tracking technique
      • Author(s): A. Jaramillo-Matta ; L. Guasch-Pesquer ; L. Martínez-Salamero ; J.A. Barrado-Rodrigo
      • Source: IET Electric Power Applications, Volume 5, Issue 3, p. 307 –316
      • DOI:  10.1049/iet-epa.2010.0091
      • Type: Article
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      • p. 307 –316 (10)
        An algorithm implementing a behavioural modelling technique for estimating the parameters of induction machine models is proposed. This technique, called torque–speed tracking, starts from manufacturer data and solves the identified problems which are caused by the lack of operating points and by the method used to minimise the torque error. The proposed technique is implemented for both single- and double-cage models, and the obtained behaviour is compared with that one obtained with other techniques used for estimating model parameters. The proposed technique is validated both with the catalogue data of 64 induction machines, and with experimental data of a 75 kW induction machine. All torque errors obtained with the proposed technique were significantly smaller than those ones obtained with the referenced techniques, for both analysed models. This technique can be easily implemented in parameter estimation algorithms which are based solely on manufacturer data.
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      Design of high-torque-density double-stator permanent magnet brushless motors

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