Science Academy Publisher International Journal of Research and Reviews in Computing Engineering Vol. 1, No. 1, March 2011 Copyright © Science Academy Publisher, United Kingdom www.sciacademypublisher.com A New Fuzzy Direct Torque Control Strategy for Induction Machine Based on Indirect Matrix Converter Brahim Metidji, Farid Tazrart, Ahmed Azib, Nabil Taib, Toufik Rekioua Department of Electrical Engineering, Bejaia University, Bejaia, Algeria Correspondence should be addressed to Brahim Metidji, metidji77@yahoo.fr Abstract – In this paper, a new fuzzy space vector modulation direct torque control strategy for induction machine based on indirect matrix converter is proposed. In the rectifier stage a space vector modulation strategy is employed. In the inverter stage two fuzzy logic regulators used to replace the classical PI regulators in PWM direct torque control method. In this method, the input current is nearly sinusoidal and the input displacement angle is adjustable. Using this control strategy, the advantages of indirect matrix converter and direct torque control method are combined. The performance of the proposed drive system is evaluated through digital simulation using MATLAB-SIMULINK package and simulation results are used to verify the effectiveness of the proposed strategy and support the analytical results. 1. Introduction Direct torque control (DTC) is a high performance electric machine closed-loop control technique, which implementation is based on torque and stator flux hysteresis comparators [1]. It is widely known to produce a quick and fast response in AC drives. A variety of techniques, different in concept, are described in literatures. Such as Switching-table-based hysteresis DTC[1], direct self-control[2], and constant switching frequency DTC[3][4],space vector modulation DTC(DTC-SVM)[5].Some of the different solutions proposed include DTC with SVM [6][7]; different power converter topologies, such as the multi-level inverter [8][9],Matrix converter[10][11]; sensorless methods [12][13]; optimum stator flux estimator for high speed operation [14][15], and artificial intelligence techniques, such as fuzzy and neuro- controllers[16]-[29]. The Direct torque control strategy is commonly used with a voltage source inverter (VSI), where a large electrolytic capacitor is used on the dc link. This capacitor is considered a disadvantage due to his short lifetime compared with power switches, and contributing considerably to the size and weight of the converter. It is therefore beneficial eliminate this capacitor, reduce converter volume and maximize efficiency. This may be done with the matrix converter (MC). These converters are direct three-phase, AC/AC, switching power converters capable of providing simultaneous amplitude and frequency transformation of three-phase voltages [30]. With different topologies of main circuit, MC can be generally classified into two categories: direct matrix converter (DMC) and indirect matrix converter (IMC). In recent years, research on direct matrix converter (DMC), has led to great advances in its control and applications [31][32]. However, this AC/AC converter topology has potential commutation problems requiring a complex control circuit and an additional protection circuit, which increases the complexity of the matrix converter. Recently, researchers have focused on the indirect matrix converter (IMC) topology [33]. IMC is an AC/DC/AC converter without the DC-link capacitor, which offers a same high performance as the conventional direct matrix converter, including four-quadrant operation, adjustable input power factor, nearly-sinusoidal waveforms with only high-order harmonics in both input current and output voltage, and no need for large energy storage components. The Direct Torque Control (DTC) scheme for direct matrix converter drives was initially presented in [10]. A new controls methods for DMC has been proposed by the authors [11][34], which allows generation of the voltage vectors required for DTC at unity input power factor. Other papers, investigates the DTC strategy for AC motors based on IMC [35][36] when the classical DTC method is employed In the inverter stage. In this paper, a new fuzzy logic DTC-SVM strategy for induction machine based on IMC is introduced and investigated. In the rectifier stage a classical SVM strategy is employed; nearly sinusoidal input current with adjustable displacement angle can be achieved in this way. In the inverter stage, the classical DTC-SVM Flux and Torque regulators are replaced by new fuzzy logic regulators, the outputs of flux and torque fuzzy logic regulators are used to produce the control signals for the SPWM voltage inverter. Using this control strategy, the advantages of IMC and DTC are combined.