Abstract: This paper presents a study on dc capacitor voltage balance control method for cascade multilevel static synchronous compensator (STATCOM) and a general analytical method for balance control strategy. Imbalance of dc capacitor voltage is considered, which is caused by the inconsistency of active power absorbed and consumed by chain, a balance control strategy is discussed, based on Phase shift angle regulation. A general analytical method based on vector analysis is also presented, by which the performance of balance control strategy can be analysed, including regulation capacity. To find out the importance of balance control strategy, a comparison still based on vector analysis between balance control strategy and without using any balance control strategy is provided, from which importance of balance control strategy, based on Phase shift angle regulation, can be known which has the advantage of strong regulation capacity, and simulations are performed to prove it.

Keywords: Cascade multilevel, dc capacitor voltage balance, static synchronous compensator (STATCOM), vector analysis