Simple current control method for three‐phase VSC under unbalanced grid condition

Abstract

Injection of both positive and negative sequence currents is desired for three-phase voltage source converters (VSC) under unbalanced grid fault condition. However, the second-order oscillation exists in the positive and negative sequence synchronous reference frame. Several approaches have been reported to cope with this second-order oscillation. Here, a simple direct proportional plus integral current control method in double synchronous reference frame is proposed. The proposed method does not require the additional filter or decoupling circuit, and does not require signal reconstruction for the current reference. Theoretical analysis and experimental study show that the proposed current control not only achieves zero steady-state error, but also exhibits good transient response.