动态电压恢复器软件锁相技术

Soft PLL technique of dynamic voltage restorer

对动态电压恢复器中常用的软件锁相环进行了研究,针对三相不平衡情况下负序分量对锁相环检测精度的影响,提出了基于数学形态滤波器的软件锁相环。通过选取适当的结构元素,结合形态学的基本运算,设计出低通形态滤波器来抑制由负序分量转换而来的2次谐波,提高锁相环的抗干扰能力和检测精度。理论分析和仿真实验都验证了其可行性,结果表明该方法能够大幅衰减负序分量的干扰,形态滤波器运算简单、速度快,能够很好地满足锁相环检测的要求。

The soft PLL（Phase Locked Loop） widely used in the dynamic voltage restorer is studied.To avoid the impact of the negative sequence component on the accuracy of PLL under three-phase unbalance condition,a soft PLL based on the mathematical morphology filter is presented,which selects the appropriate morphologic structure elements and combines with the proper morphologic operators to design a low-pass morphological filter for restraining the second harmonic produced by the negative sequence component and improving the detection accuracy and anti-interference ability of PLL.Theoretical analysis and experimental results prove that,the interference is substantially attenuated and the operation of morphological filter is simple and fast,meeting the requirements of PLL detection.