386 / 2021-11-10 22:19:53

An Improved Linear Phase-Locked Loop (PLL) with notch Pre-filter

linear PLL,weak grid,phase angle recognition,notch filter

Power system and automation > Modeling, control and stability analysis in power system

Phase/frequency jumps, and harmonic pollution are important factors that affect accuracy of phase-locked loop (PLL) in weak grids. The synchronous reference frame PLL(SRF-PLL) is nonlinear and cannot balance dynamic response and harmonic filtering performance, which is difficult to meet the requirements in weak grids. To solve this problem, a pre-filter Feedforward Linear PLL (PFL-PLL) is proposed in this paper, which eliminates the nonlinearity and the effect of the voltage amplitude by direct phase recognition. The linear property of PLL makes it possible that take a feedforward path to improve the dynamic response. Meanwhile, a notch prefilter and corresponding phase compensation module is designed to improve the dynamic response and accuracy of phase jump. In experiment, the proposed PLL could track the phase jump in half cycle and frequency jump in one cycle. The experiment results demonstrate that the proposed PFL-PLL is ，which is a valuable phase-locked method in weak grid.