System control and DC voltage control method for stacom based on hybrid multilevel H-bridge converter

This paper presents an improved structure for static synchronous compensator (STATCOM) system based on hybrid multilevel H-bridge converter. In the new structure, the chosen of dc capacitor capacitance is considered for every module, which will reduce the dc capacitor capacitance and reduce the cost of the system. A novel system control and dc capacitor voltage balance control strategy is presented for the new system. The control includes two levels. Upper level use direct current control realize inactive current control, and lower level use a PLL of compensating current realize the dc voltage control. Simulation results show that the new control method can not only compensate reactive power but also can maintain dc voltage at a given value.