Negative Sequence Current Regulation Based Power Control Strategy for Vienna Rectifier Under Unbalanced Grid Voltage Dips

When Vienna rectifier operates at unbalanced grid voltage dips, the conventional power control strategy suffers from the active power reduction and the input current distortion. To solve these problems, a novel negative sequence current regulation based power control strategy is proposed. On the basis of analyzing maximum input current and maximum phase difference between the gird voltage and the input current, the maximum active power and the available operation region of the conventional strategy are obtained. The proposed strategy introduces the current harmonic coefficient and the active power coefficient. The current harmonic coefficient can change the phase angle characteristic of the grid voltage and the input current. The active power coefficient can reduce the effect of the negative sequence grid voltage on active power and realize the maximum input current limitation. According to the synthesis of the active power and the coefficients information, the negative sequence current regulation is realized, which can reduce the input current harmonics and increase the active power by injecting a small amount of input power ripple. In addition, the coefficients of the negative sequence current regulation are selected according to the unbalance degree of the grid voltage and the DC-link voltage. Finally, the effectiveness of the proposed strategy is verified on a Vienna rectifier platform.