A novel DC voltage balancing method for cascaded STATCOM

The superiority of cascaded multilevel inverter (CMI) is unparalleled in high power and high voltage STATCOM. However, the parameters and operating modes of each individual power unit composing of the cascaded STATCOM are various, causing DC capacitor voltage disequilibrium. This phenomenon seriously impairs the performance of STATCOM. This paper combines the operation characteristics of the cascaded STATCOM and proposes a new control scheme for DC voltage balance. This new control method uses software to achieve the total active power control and uses bidirectional switches to make the imbalance power flow among the capacitors in order to keep DC capacitor voltages balance. The simulation results reveal that the proposed control scheme has satisfactorily achieved the control goals.