面向大容量直流闭锁的暂态稳定紧急切机控制策略研究

Strategy of emergency generator tripping control for transient stability after a large capacity HVDC blocking fault

在交直流混合系统中,大容量高压直流线路闭锁造成的永久性功率冲击将引起送端交流系统机组不同程度的加速运动,可能造成送端机组失步运行。主要对大容量直流输电线路闭锁后的切机策略展开研究。首先分析比较了直流闭锁故障与短时功率冲击对送端系统稳定性的不同影响,提出了三角形近似法求取切机总量,改善了控制总量预估的保守性。然后从减速能量角度定义切机灵敏度指标,基于此形成切机比例上限约束下的切机量分配方案。在搭建的典型两区域交直流混合电网进行了仿真分析,验证了所提方法的有效性。该方法能够充分发挥领先机群中高灵敏度机组对于暂态稳定恢复的影响,可有效减少切机量,降低暂态稳定控制代价。

In an AC/DC hybrid power system,after the long-term power impact caused by large capacity High-Voltage Direct Current(HVDC)line blocking,the generators in the sending-end system will have different degrees of acceleration movement,and finally the generators at the sending-end may be out of step.This paper examines the generator tripping strategy after the HVDC line blocking fault.First,we analyze and compare the different effects on the stability of the sending-end system between the HVDC blocking fault and the short-term power impact,and then a triangle approximation method is proposed to estimate the generation capacity to be tripped.This establishes the conservative of calculated control variable.Then,the sensitivity of generator tripping is defined from the perspective of deceleration energy.Finally,considering the generator tripping ratio limitation,a scheme to allocate the generator tripping capacity is formed.Simulation and analysis of a typical two-area AC/DC hybrid power system are carried out to verify effectiveness of the proposed method.Using this method,the generators that have better capacity to enhance the need for transient stability to be considered as a priority.In this way the tripping amount and the control cost are effectively reduced.