Research on unbalance load compensation by cascaded STATCOM with star configuration

Control methods for cascaded STATCOM with star configuration to compensate unbalance load are proposed in this paper, both in transformerless way and transformer-used way. According to the analysis results, when the STATCOM is directly connected to the power grid without transformer, a zero-sequence voltage is injected into its output reference voltage, the amplitude of which is about twice as the system voltage amplitude. When it is integrated into the grid through a DY1 transformer, a zero-sequence current should be injected into in its output current reference, the range of which reaches about twice as the original current needed to be compensated. PSCAD/EMTDC is used to simulate these two conditions and the simulation results show that both methods can compensate the unbalance load effectively.