Performance Analysis of Phase-Locked Loop Based on Third-Order Generalized Integrator under Inter-harmonic Perturbation

With the increasing capacity of renewable energy, the accurate extraction of grid phase is important to ensure the stable operation for power electronic devices with Phase-locked Loop (PLL). Given inter-harmonic perturbation imposed on grid voltage at the Point of Common Coupling (PCC), deviation will be induced into the PLL. This paper applies Third-Order General-Integrator (TOGI) as the pre-filter in PLL, which could extract the fundamental positive sequence component under the perturbation. To analyse the TOGI-PLL performance, firstly, the PLL linearized model is given and the small-signal model of PLL is derived by harmonic linearization. The expression of TOGI is presented in s domain and in time domain, also the practical transfer function based on the TOGI structure is proposed. With the consideration of PLL nature, the performance of TOGI-PLL is analyzed theoretically. Experiment based on RT-LAB platform confirmed the analysis.