DC voltage balancing technique using multi-pulse optimal PWM for cascade H-bridge inverters based STATCOM

A novel multi-pulse optimal PWIM technique for STATCOM based on cascade H-bridge inverters is proposed. The harmonics are suppressed using optimization techniques. Furthermore the fundamental output voltages of all the inverter cells are controlled to be equal to make all the inverter cells equally share the exchanged power with power system, which is to maintain the dc voltages as balance as possible. At the same time the switching-pattern swapping technique is used, and the dc voltages can be fairly balanced. The validity of the proposed method is verified using the experimental results of a laboratory prototype of 30 kVAr STATCOM based on a 17-level cascaded H-bridges inverter.