Compensation of offset for SRF-PLL in grid-connected inverters

Abstract

The grid-connected inverters that use synchronous reference frame based phase-locked loop SRF-PLL are applied very popular. The function of SRF-PLLs is fast and accurate estimation of frequency, phase angle, and magnitude of grid voltage. The power quality of the current injected into the grid depends on these estimated parameters. The measurements or processes of data conversion can typically introduce the dc offset in the measured grid voltage. The dc offset is one of the reasons for causing errors for the estimated parameters of the grid voltage and causes injected current with harmonic distortions. This paper proposes a technique of dc offset compensation for SRF-PLL based on the Second Order Generalized Integrator (SOGI). The simulation results validated the performance and robustness of the proposed technique.