A novel control method for DC voltage of cascaded STATCOM

The superiority of cascade STATCOM is unparalleled in power quality controller under high power and high voltage conditions. However, the parameters and working modes of each unit consisting of the cascaded STATCOM differ from unit to unit, causing unit voltage disequilibrium in DC side, impairing the operation performance of STATCOM. Thus maintaining the DC voltage balance and stable becomes critical for cascaded STATCOM. This paper combines the operation characteristics of the cascaded STATCOM, and proposes a new control scheme which uses software to reach total active power control and makes the unbalance power flow among the capacitors by using chopper-controllers. The operating principle of the chopper-controllers is analyzed and the implementation is presented. The simulation reveals that the proposed control scheme achieved the control task with satisfaction.