基于定关断面积的分层接入UHVDC系统换流器协调控制策略

基于分层接入特高压直流输电（UHVDC）系统逆变侧高低端的耦合特性,分析叠弧面积增加引发换流器换相失败的机理,提出一种抑制分层接入UHVDC系统非故障层换流器换相失败的协调控制策略。该策略通过补偿交流故障后非故障层换流器所需的叠弧面积,使晶闸管具有足够的关断面积完成去游离过程,从而防止换相失败的发生。最后基于PSCAD/EMTDC搭建实际系统模型并进行了仿真验证,结果表明所提协调控制策略能有效抑制不同故障程度下受端电网对称和不对称故障下非故障层换流器的换相失败,可提升系统的稳定性。

COORDINATED CONTROL STRATEGY OF CONVERTER FOR UHVDC SYSTEM UNDER HIERARCHICAL CONNECTION BASED ON CONSTANT EXTINCTION AREA

The research on commutation failure suppression strategy of UHVDC system converter has important engineering significance. Based on the coupling characteristics of the high and low side of the inverter side in the UHVDC system under hierarchical connection, this paper analyzes the mechanism of commutation failure caused by the increase of the overlap area, and proposes a coordinated control strategy to suppress the commutation failure of the non-fault layer converter in the UHVDC system under hierarchical connection. The strategy compensates the overlap area required by the non-fault layer converter after AC fault, so that the thyristor has enough extinction area to complete the de dissociation process, so as to prevent commutation failure. Finally, an actual system model is built based on PSCAD/EMTDC, and the simulation results show that the proposed coordinated control strategy can effectively suppress the commutation failure of the non-fault layer converter under symmetrical and asymmetric faults of the receiving end grid under different fault degrees, and improve the stability of the system.