中文摘要：

结合±1 100kV特高压直流分层接入方式下受端连接多个交流系统的特点,建立了逆变侧各换流器的附加功率—电压控制,通过独立控制各换流器触发角实现对其输送功率的独立调节。同时,为了减少在紧急功率控制过程中各换流器发生换相失败的可能,提出最优功率比的概念,将整流侧阶梯式功率提升指令按最优功率比进行预估,并分配给逆变侧各换流器的附加功率—电压控制,实现对逆变侧各换流器提升功率的协调控制。基于PSCAD仿真平台,采用±1 100kV特高压直流系统逆变侧分层接入500kV/1 000kV交流系统的仿真系统进行验证。结果表明,附加功率—电压控制器能够实现对换流器输送功率的独立控制,有利于发挥分层接入方式下潮流分布可控的优势。功率协调控制策略在紧急功率控制时能够将直流功率合理分配给各换流器,有利于充分利用各换流器输送功率的能力,并减小换流器发生换相失败的可能。

英文摘要：

Hierarchical connection mode is a new and attractive mode for ± 1 100 kV ultra-high voltage direct current (UHVDC) system connected to different voltage level AC systems to reduce the scale of the converter transformer.An additional power-voltage controller is designed to enhance the advantages of hierarchical connection mode.The proposed additional power-voltage controller controls the transmitting power between the different AC systems by controlling the firing angle of the series converters on the inverter side.The optimal power ratio is defined,based on which,a power coordinated control strategy is proposed which is capable of reducing the possibility of commutation failure.A ±1 100 kV UHVDC system hierarchically connected to the 500 kV/1 000 kV AC system is built in PSCAD/EMTDC.The simulation results show that the additional power-voltage controller is valid and the power coordination controller is effective in making full use of the transmitting capacity of converters and reducing the possibility of commutation failure. This work is supported by National Natural Science Foundation of China (No.5 1277068),Program for New Century Excellent Talents in University(No.NCET-12-0846)and Program of Introducing Talents of Discipline to Universities(“1 1 1"Program)(No.B08013).