Grid-voltage synchronization algorithm for grid tied renewable energy sources during adverse grid fault condition

Grid-voltage synchronization algorithm performs the main role during unbalanced and distorted grid fault condition to measure the positive- and negative-sequence values of grid voltage at the point of common coupling for grid-tied renewable energy sources. Power control during severe grid conditions mostly depends on these measured values. Three-phase synchronous reference frame phase-locked loop (SRF-PLL) is the most conversant methods for grid-voltage synchronization. Decoupled Double Synchronous Reference Frame PLL (DDSRF-PLL) is one of the most advanced synchronization algorithm. In this paper, calculation for power control during unbalanced grid condition are given for active and reactive power and performance of DDSRF-PLL is evaluated under adverse grid fault conditions.