Robust All-Band-Pass Filter Configuration as Orthogonal Signal Generator in Three-Phase Prefilter-Based PLL

Abstract

A three-phase phase-locked loop (PLL) applicable for synchronizing inverter-based energy resources into weak grids is proposed. A new method is proposed in this paper, whereby an all-band-pass filter (ABPF) configuration is utilized in realizing a dual second-order generalized integrator (DSOGI) as a prefilter in a three-phase PLL. Offsets in magnitude and phase and processing delays that may emanate from the filters are actively compensated. Usually, a proportional plus integral (PI) controller is selected as loop filter (LF) in a conventional PLL. Herein, a proportional integral plus resonant (PIR) controller is proposed as the LF, because it yields more promising results than the conventional PI controller in damping oscillations by further reducing steady-state errors. Consequently, a PLL with the ABPF-DSOGI is applied in synchronizing a STATCOM to a weak grid to verify its effectiveness and robustness. Simulation shows that the frequency overshoot in response to frequency step change by the ABPF-DSOGI based PLL on the STATCOM was insignificant. Other simulation results and experimental results are presented to validate the efficacy of the ABPF-DSOGI.