Fast and Robust Phase Estimation Algorithm for Heavily Distorted Grid Conditions

This paper proposes a fast and robust phase estimation algorithm (PEA), a counterpart of the phase-locked loop (PLL), for heavily distorted grid conditions. The PEA, named as the WLSE-PEA, consists of the moving average filter (MAF), the weighted least squares estimation (WLSE), the frequency-locked loop (FLL), and the zero crossing detection (ZCD). The MAF can eliminate all the odd-order harmonics in the distorted grid voltages. The WLSE is employed to estimate the fundamental positive-sequence component. The combination of the ZCD and the FLL enables the WLSE-PEA to be adaptive to frequency deviations. Compared with some advanced phase-locked loops, the proposed WLSE-PEA has a faster response. Also, it is robust to common grid disturbances including three-phase unbalances, dc offsets, harmonics, phase jumps, and voltage sags. Simulation and experimental results have verified the effectiveness and advantages of the WLSE-PEA.