一种用于多端直流输电系统交流故障穿越的新型控制策略

A Novel Control Strategy for AC Fault Ride Through in Multi-terminal DC System

针对传统的电压下垂控制用于多端直流输电系统中时直流电压和有功功率分配方面的不足,提出了一种新型的直流电压协调控制策略。该控制策略不仅可以保持直流电压恒定,而且能够依据不同的原则,精确调节传输到各个换流站的有功功率分配比例,而不依赖线路阻抗,从而有效提高多端直流输电系统的交流故障穿越能力。在交流故障期间,将这种新的控制策略对有功功率分配比例的快速调节,与一系列无需通信的交流故障穿越方法(如降压法、升频法和直流斩波器法)相结合,可以更加充分地利用有功功率,同时避免直流线路出现功率失衡的问题。基于PSCAD/EMTDC建立了一个五端柔性直流输电系统仿真模型,验证了不同程度交流故障下所提出控制策略的有效性。

This paper proposed a novel control strategycoordinated DC voltage control(DCVC)-to enhance the AC fault ride through capability of multi-terminal high voltage direct current(HVDC) system. This control strategy is independent on exact line impedance parameters, and has a better performance than the conventional voltage droop control on keeping DC voltage constant and distributing power fast and flexibly. During the AC fault period, this novel control strategy is able to avoid the overvoltage of HVDC lines and make full use of active power by combing power distribution ratio adjustment and a series of AC fault ride through some methods, including voltage reduction,frequency increase and DC chopper methods. The control effect was validated by a five-terminal HVDC system based on PSCAD/EMTDC under different degrees of AC fault.