柔性直流输电受端交流侧故障下的控制策略

为了柔性直流输电受端交流侧故障下的电网电压尽快恢复，在详细分析了传统电压裕度控制的切换过程后提出了一种改进的电压裕度控制策略，通过在跌落瞬间的积分清零及给定值调整，缩短了切换的动态过程，减小了直流电压的冲击。同时设计了故障期间的有功和无功协调控制，根据电网跌落深度发出相应的无功电流，剩余的电流容量用于维持故障前的有功水平。最后在PSCAD/EMTDC中搭建了柔性直流输电系统的仿真模型，验证了本文所设计控制策略的有效性。

Control Strategy for VSC-HVDC Under AC System Fault of Receiving End

In order to obtain quick recovery of power grid voltage during AC system faults of receiving end of VSC-HVDC system, an improved voltage margin control strategy is proposed after analyzing the switching process of the traditional voltage margin control.In this strategy,the switching process is shorten by resetting integral term and adjusting set point.Meanwhile,the coordination control of reactive and active power during fault is also designed.The reactive current is injected to AC system according to the sag depth,and the rest of current capacity is used to maintain active power level.Simulation results of VSC-HVDC model developed in PSCAD/EMTDC prove the validity of the proposed control strategy.