LCC与VSC级联的特高压混合直流输电系统控制策略

Control strategy of a hybrid UHVDC transmission system cascaded by LCC and VSC

受端为电网换相换流器(Line Commutated Converter,LCC)与电压源换流器(Voltage Source Converters,VSC)级联的特高压混合直流输电系统能够抑制受端LCC换相失败导致的功率传输中断,系统接线方式和控制方式变得灵活和多样化。针对受端交流系统故障穿越,提出了基于直流电压与受端交流电压的低压限流控制策略和LCC限压恢复策略。针对多换流器的稳定运行,提出了多换流器功率协调控制策略和VSC在线投退策略。针对直流线路故障穿越,提出了基于直流电压偏差控制的穿越策略。基于电磁暂态程序(PSCAD/EMTDC)搭建了LCC与VSC级联的特高压混合直流输电系统仿真模型。仿真结果验证了所述控制策略的有效性。

A hybrid UHVDC transmission system cascaded by a Line Commutated Converter(LCC)and Voltage Source Converters(VSC)at the receiving station can prevent power interruption caused by commutation failure of the LCC at receiving station.The connection control modes become more flexible and diversified.Current which depends on a low voltage control strategy based on the DC and AC voltages of the receiving terminal and an LCC for the limiting voltage control strategy are proposed for AC fault crossing at the receiving station.To obtain stable operation of multi-converters,a power coordination control strategy of multi-converters and a VSC online inputting/quitting strategy are proposed.A crossing strategy based on DC voltage deviation control is proposed for DC line fault crossing.A simulation model is constructed for the hybrid UHVDC system cascaded by LCC and VSC using an electromagnetic transient program(PSCAD/EMTDC).The simulation results show the validity of proposed control strategies.