Direct power control of PWM rectifier under unbalanced network using extended power theory

Abstract

The control of PWM rectifiers under unbalanced network has become an important issue in recent years, especially in the applications with weak grid. Conventional methods is based on voltage oriented control (VOC), which requires several PI controllers in dual reference frame and the sequence extraction of grid/rectifier voltages and currents. To reduce the control complexity, recently direct power control (DPC) based solutions were proposed, which only requires to add appropriate power compensations to the original power reference. However, the calculation of power compensation is usually complicated. This paper proposes a space vector modulation (SVM) based DPC for PWM rectifier under unbalanced network, which uses extended power theory rather than conventional instantaneous power theory to obtain much simpler power compensations. Furthermore, not only sinusoidal grid current is obtained, but also the oscillations in the dc bus voltage is also significantly reduced. The effectiveness of the proposed method is confirmed by the presented experimental results.