一种改进型两相静止坐标系增强型锁相环

An improved two-phase stationary frame EPLL

电网电压中的谐波、不平衡以及直流偏移会在传统两相静止坐标系增强型锁相环(αβ-EPLL)所检测的电网基波电压幅值、频率和相角中产生周期波动,尤其是直流偏移会产生基波频率的周期波动,难以使用低通滤波器直接滤除。提出一种改进的αβ-EPLL结构,在两相信号输入侧引入直流偏移积分器以消除输入直流偏移,在幅值检测环和频率检测环中分别引入延时信号滤波器以消除输入谐波和不平衡的影响。详细的理论分析和实验结果验证了所提出的改进αβ-EPLL的正确性和可行性。

The harmonics, unbalance and DC offsets in grid voltage may cause the periodic ripples in the amplitude, frequency and phase angle estimated by the standard αβ-EPLL（ two-phase stationary frame Enhanced Phase Locked Loop）. Especially, the DC offsets may generate the periodic ripples at the fundamental frequency, which is hard to be filtered by the low-pass filter. An improved αβ-EPLL is proposed, in which two DC offsets detection integrators are introduced in the two-phase inputs side to eliminate the DC offsets and the cascaded delay signal cancellation filters are respectively introduced in the amplitude estimation loop and frequency estimation loop to eliminate the effect of input harmonics and unbalance. The detailed theoretical analysis and experimental results validate the validity and feasibility of the proposed improved αβ-EPLL.