DSP implementation of direct power control with constant switching frequency for three-phase PWM rectifiers

This paper proposes a novel and simple direct power control scheme for three-phase PWM rectifiers operated at constant switching frequency using space vector modulation (DPC-SVM). The active and reactive power is used as the pulse width modulated (PWM) control variables instead of the three-phase line currents usually used. Moreover, a line voltage sensors are replaced by virtual flux (VF) estimator. Theoretical principle of this method is discussed. The steady state and dynamic results of DPC-SVM scheme that illustrates the operation and performance of the proposed system are presented. It is shown that DPC-SVM exhibits several features as: simple algorithm, good dynamic response, constant switching frequency and particularly provide low THD sinusoidal line current when supply voltage is no ideal. Simulated and experimental results have proven excellent performances and verify the validity of the proposed system.

I. Introduction

Most of three-phase rectifiers use a diode bridge circuit and a bulk storage capacitor. It has advantage of being simple, robust and low cost. However, diodes rectifier offers only unidirectional power flow, low power factor and high level of harmonic input currents. Therefore, a three-phase PWM rectifier (Fig. 1) is more interesting solution for industrial application thanks to viable advantages as: •

b i-directional power flow.

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low harmonic distortion of line current.

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regulation of input power factor to unity.

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adjustment and stabilization of DC-link voltage.

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reduced size of DC filter capacitor.

Fig. 1

Representation of three-phase PWM boost rectifier.