Performance evaluation and benchmarking of PLL algorithms for grid-connected RES applications

The phase-locked loop (PLL) is the main controller element for the fast and accurate synchronisation and operation of grid-connected renewable energy systems (RESs). It is used to extract the grid voltage information such as the phase angle, the frequency and amplitude. Subsequently, this information is used in the control system of the grid-side converter of the RES. The performance of the PLL is critical under abnormal grid conditions such as in the event of balanced and/or unbalanced faults, frequency and phase variations, the presence of harmonics, interharmonics and DC offset. This study sets out with a benchmarking study of the four latest state-of-the-art PLLs. The PLLs compared are the decoupled dual synchronous reference frame PLL, the decoupling network designed in αβ-frame PLL, the enhanced pre-filtering moving average filter type-2 PLL and the harmonic-interharmonic DC-offset PLL. The PLLs are analysed and compared based on their performance, their dynamic response and their computational complexity. The benchmarking concludes with a PLL selection guide depending on the application and other system constraints. Experiments and simulation results are presented to compare and analyse the performance of the selected PLLs.