一种基于椭圆拟合的三相电压不平衡条件下的锁相环

针对传统的三相电网相角检测方法在电网频率波动及故障情况下存在的不足,提出了一种新型数字锁相环设计方法。所提出的锁相环通过递推最小二乘法椭圆拟合辨识出椭圆参数,利用锁相环产生不对称的正弦余弦输出,消除了电网不平衡状态下的鉴相二倍频分量;在此基础上对锁相环输出信号进行移相和正序分量的提取,从而实现90°移相与电网频率无关;推导了不对称幅值和相位与椭圆参数的关系,设计了递推最小二乘法,最后给出了仿真和实验结果。仿真和实验结果验证了本方案的有效性。

A Novel Digital Phase-locked Loop Under Three-phase Unbalance Voltages Based on Ellipse Fitting Method

When the grid voltage is distorted and unbalanced, the dynamic behavior of classical phase-locked loop system becomes dissatisfactory, a novel digital phase-locked loop(DPLL) is put forward. In the new DPLL presented, ellipse parameters are identified by recursive least square method and asymmetric output of DPLL produced by identified parameters by which the second harmonic is eliminated in unbalanced voltage condition, and then 90 degree phase shift and positive sequence are produced from DPLL output signals which are not influenced by grid frequency variation. The relationship between ellipse parameters and unbalanced voltage is derived and RLS method is designed in the paper, simulation and experiment results validate the theoretical analysis.