Baoju Wu, Nanmu Hui, and Xiaowei Han
Second-order all-pass filter (SOAPF), harmonic, phase-locked loop (PLL), comb filter (CF)
Due to the voltage imbalance in the grid, a significant number of harmonic components are present, often resulting in the failure of conventional phase-locked loop (PLL) systems to accurately track the fundamental phase. To address this challenging issue, a dual second- order all-pass filter (DSOAPF) is designed based on the second-order all-pass filter (SOAPF), enabling the accurate extraction of the fundamental positive sequence component (FPSC) from the three- phase power grid. Building upon this, a combined filter, comprising a DSOAPF and a comb filter (CF), is proposed and integrated into the PLL structure. Through Simulink simulations and analysis under voltage imbalance and harmonic conditions, the results demonstrate that this approach outperforms traditional PLL methods in terms of fundamental voltage phase tracking. Furthermore, it effectively extracts both positive and negative sequence amplitudes, thereby enhancing the rapidity, stability, anti-interference capability, and overall effectiveness of grid-connected power systems.
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