A Half Controlled Current Source Actively Commuted Converter with the Low Switching Frequency Modulation Strategy

A half controlled actively commuted converter (ACC) is proposed in this paper to reduce the number of controlled semiconductor devices. For the proposed half-controlled ACC, it contains only half controlled devices than the fully controlled ACC. Moreover, a lower switching frequency modulation strategy is also proposed with which each device is only turned on and off once during each grid cycle. Although the switching frequency is reduced, a multi-winding phase-shifted transformer can effectively eliminate the low order and even harmonics of the modulated output current. Simulations on a 1000MW/ 500kV ac/ ±350kV dc half-controlled ACC validate the effectiveness of the topology and modulation strategy.