Phase-locked loop for AC systems: Analyses and comparisons

As the number of distributed power generation systems (DPGSs) connected to the utility grid is increasing, the issue of synchronization between the DPGSs and the grid is attracting more attention. The phase-locked loop (PLL) technique is considered as the state of art in providing phase and frequency information for DPGSs. This paper presents quantified analyses and comparisons of the main PLL techniques based on different structures for both single phase and 3-phase systems. The fundamentals of different phase locking principles are explained. Performance of different PLLs when subjected to various distortions is compared based on quantified PSCAD simulation results. The performance of the PLL module of the PSCAD software package has also been investigated.