Optimization strategy of DSOGI-PLL precision under harmonic interference conditions

Grid inverters can extract accurate fundamental signal with dual second-order generalized integrator phase-locked loop (DSOGI-PLL) under generalized harmonic grid voltage. The oriented voltage extracted by DSOGI will fluctuate when there are a large amount of low order harmonics in the power grid, which declines the performance of DSOGI. The complex vector model for DSOGI is established, and the mechanism that output voltage of the traditional DSOGI-PLL contains harmonic can be analyzed. According to the orthogonal characteristics of SOGI, the orthogonal harmonic elimination method (OHEM) is derived to achieve a better elimination on harmonics with successive differential of harmonic grid voltage. MATLAB simulation shows that the fundamental positive and negative sequence voltage and phase angle can be obtained effectively with proposed method under distorted grid voltage.