VSCs based HVDC and its control strategy

Voltage source converter (VSC) based HVDC (VSC-HVDC) is a new power transmission technology preferable in small or medium power transmission. Using turn-off power semiconductors and combined with pulse width modulation (PWM), this technology has more flexible control strategy and simple work mode as the comparison of the conventional HVDC. Firstly, this paper presents the elements of VSC-HVDC, and then a feed-forward-decoupled current-control strategy is proposed. By using this control strategy, not only the active and reactive power of VSC-HVDC can be controlled independently, but also the dynamic responded time can be shortened. In order to improve the performance of DC voltage control, AC active current is used to compensate the DC voltage. With the help of PSCAD/EMTDC, several VSC-HVDC basis running and control mode are analyzed and the simulation results got after AC single phase fault verify that the control strategy has fast response and strong stability