Comparative performance evaluation of phase-locked loop (PLL) algorithms for single-phase grid-connected converters

The phase-locked loop (PLL) algorithms are of crucial significance for the stable operation and effective grid-integration of power converters and renewable energy systems. In this paper, a comprehensive analysis and performance comparison is presented on the detection performance for three PLLs (NTD-PLL, DCOC-PLL and TPFA-PLL) under grid voltage disturbances, such as phase jump, frequency step change, voltage sag, harmonics, dc offset scenarios and noise. Through theoretical analysis and digital simulations, it is found that the NTD-PLL has the best performance under frequency step change scenario, and under dc offset scenario, the DCOC-PLL would be a good choice. For the TPFA-PLL, a strong harmonic immunity is realized due to the application of the moving average filter (MAF). Besides, the small-signal models of the three PLLs are proposed in this paper. The stability analysis, PI parameters design guidelines of the PLLs are presented as well. Finally, the simulation results are presented to validate the effectiveness of the theoretical analysis.