锁相环对HVDC系统后续换相失败的影响研究

Study on the Influence of Phase-locked Loop on Follow-up Commutation Failure of HVDC System

触发相位控制是高压直流控制系统的基础,锁相环提供的参考相位对于触发相位控制的精度具有重要影响。针对目前等间隔控制普遍采用的同步参考坐标系锁相环动态响应速度缓慢的缺点,提出采用一种改进锁相环的方法来提高触发控制的精度。该锁相环在具有较快动态响应速度的同时,利用级联延迟信号消除法和数学运算滤波串联构成前置滤波环节,保证其具有较强的抗干扰能力。在CIGRE HVDC标准测试模型中分别采用原锁相环和改进锁相环进行触发,对交流故障下逆变器发生换相失败的情况进行仿真测试,结果表明,采用改进锁相环能够有效降低故障持续期间发生换相失败的几率。

Trigger phase control is the basis for the HVDC control system,and the reference phase provided by phase-locked loop has an important influence on the accuracy of trigger phase control.Aiming at the shortcomings of the slow dynamic response speed of synchronous reference frame phase-locked loop,which is commonly used in equidistant firing control,an improved phase-locked loop was proposed to improve the accuracy of trigger phase control.The improved phase-locked loop has a relatively fast dynamic response speed.At the same time,the cascaded delayed signal cancellation method and the mathematical operation filter were used in series to form a pre-filtering link to ensure a strong anti-interference capability.Finally,in the CIGRE benchmark model of HVDC,the original phase-locked loop and the improved phase-locked loop were used for triggering respectively.The simulation test of the commutation failure under AC fault was carried out.The results show that the improved phase-locked loop can effectively reduce the probability of commutation failure during the duration of the fault.