Enhanced Frequency-Locked Loop Based on a Third-Order Generalized Integrator

The second-order generalized integrator frequency-locked loop (SOGI-FLL) is widely used in distributed generation (DG) systems for synchronization. However, constrained by its inherent structure, there exists a conflict between the filtering ability and dynamic performance in the SOGI-FLL, which is not entirely satisfied. As a high-end version of the SOGI-FLL, the third-order generalized integrator frequency-locked loop (TOGI-FLL) is proposed in this paper, achieving better filtering ability and faster dynamic response. These advantages are validated with frequency domain analyses and small signal analyses. A comparison among the TOGI-FLL and other enhanced versions of the SOGI-FLL is also given. Experiment results presented at the last confirm that the TOGI-FLL has the best performance in both steady-state and dynamic process.