The cascaded STATCOM with star configuration is used widely in power quality control at high voltage and high power applications. In fact

the three phase load cannot be fully balanced. The STATCOM shall

while in the course of controlling reactive power

shall try is capability to compensate three-phaseload unbalance simultaneously. The instruction current for compensating reactive power and three-phase un-balance is calculated simultaneously in accordance with the load current. The equivalent circuit of theSTATCOM and grid connection is given. The neutral point voltage of the STATCOM is calculated based onthe principle that the active power absorbed by each cluster should be zero. The current tracking and DC volt-age stabilization and balance control strategies are designed. The capability for the STATCOM to compensate three phase unbalance is analyzed in case of over-modulation. A 1.5 Mvar

2kV

seven-level STATCOM sim-ulation model is built in Matlab/Simulink. The maximum load unbalance to be compensated by the STATCOM and the correctness of the control strategy of the STATCOM are verified through different load conditions.