基于虚拟电容的直流输电系统连续换相失败抑制研究

为解决高压直流输电系统中连续换相失败对直流系统运行影响严重的问题,分析了直流输电系统换相失败产生的机理,引入虚拟电容的概念,以虚拟电容作为直流电压变化率检测的载体,反应故障期间及其恢复过程中的直流电压的动态特性,通过降低故障期间电流指令值及补偿直流电压来实现对直流输电系统连续换相失败的抑制作用。通过建立的直流输电系统电磁暂态模型验证了所提方法可有效抑制单相故障及三相故障情况下高压直流输电系统连续换相失败,加速故障后系统的恢复。

Research on Suppressing Continuous Commutation Failure of HVDC System Based on Virtual Capacitor

: In order to solve the problem that continuous commutation failure in HVDC transmission system has a serious impact on the operation of HVDC system, the mechanism of commutation failure of HVDC system is analyzed, and the concept of virtual capacitor is introduced. The virtual capacitor is used as the carrier of DC voltage change rate, and by reducing the current command value and compensating the DC voltage during the fault, the continuous commutation failure of HVDC transmission system can be restrained. The method of introducing virtual capacitor can reflect the dynamic characteristics of DC voltage during fault and recovery process. Through the electromagnetic transient model of HVDC system, it is verified that the proposed method can effectively suppress the continuous commutation failure of HVDC system under single-phase fault and three-phase fault, and accelerate the recovery of the system after fault.Keywords: HVDC transmission; continuous commutation failure; virtual capacitor; voltage compensation; fault recovery