A Multilevel Current Source Actively Commutated Converter With the Control Strategy

In order to improve power quality and reduce the difficulty of power semiconductor devices in series, a multilevel current source actively commutated converter (ACC) is proposed in this paper. It mainly consists of several power modules with series connection on dc current (DC) side and parallel connection on alternating current (AC) side. Each module output three-level square wave current with different phases. Then, the multilevel current is generated on high voltage grid side. Because of high power quality, it requires smaller size of filters to obtain sinusoidal alternating grid current. Moreover, it is easy to achieve unity power factor owing to the adjustable phase difference. The matched unity power factor control strategy is also proposed. Simulations on a 30MW 7 kV ac/ 100 kV dc ACC verifies feasibility of the topology and control strategy.