考虑频率变化的基于DFT单相数字锁相环的椭圆拟合方法

针对传统的DFT单相锁相环在电网频率发生变化时存在锁相性能变差问题,提出了一种考虑频率变化的基于DFT单相数字锁相环的椭圆拟合方法。采用带遗忘因子的递推最小二乘法进行椭圆拟合辨识出椭圆参数,再由锁相环产生正、余弦输出,实现了基于虚拟两相正交电压矢量的单相数字锁相环控制。通过Matlab对电网电压的频率波动、相位突变以及谐波注入等参数变化的影响进行了仿真。最后,通过实验结果验证了该方法的有效性,具有较好的稳态性能和动态特性。

A novel single-phase digital phase-locked loop based on DFT considering frequency variation

When the grid frequency is varied, the traditional single-phase Phase-locked Loop (PLL) using DFT becomes dissatisfactory. To solve the problems an approach is proposed where ellipse fitting algorithm is incorporated a single-phase Digital Phase-locked Loop (DPLL) based on DFT considering frequency variation. Recursive least square method with forgetting factor is adopted to fit and identify the ellipse parameters, and sine and cosine signals are generated and output by phase-locked loop, then a DPLL on the basis of two-phase orthogonal voltage vector for single-phase digital phase-locked loop is implemented. The influence of parameter variations of the grid voltage including frequency fluctuation, phase mutation and harmonic injection is simulated by MATLAB. Finally, the experimental results verify that the approach is feasible and has better steady-state performance and dynamic characteristics.