Adaptive SRF-PLL with reconfigurable controller for Microgrid in grid-connected and stand-alone modes

Accurate detection of grid voltage phase angle under fault and distorted voltage conditions is essential for distributed generation (DG). Failure to detect supply voltage phase angle accurately will lead to frequency fluctuation, power oscillation and harmonic currents. For Microgrid applications, the synchronization mechanism should be able to detect the frequency drift during islanding mode and provide stable frequency reference for standalone operation. To realize this goal, an adaptive synchronous reference frame phase locked loop (ASRF-PLL) with islanding detection capability is proposed. A reconfigurable inverter controller that supports both gird connected and stand-alone operation modes is also proposed. This provides stable operation under various grid conditions and maintains stable frequency reference during islanding mode. Simulation results were carried out to validate the proposed PLL to synchronies the power converter link between the Microgrid with hybrid generation and the AC Grid. The proposed PLL was implemented using the dSPACE 1103. The experimental results confirm excellent performance of the proposed technique and agree with the simulation results moreover. The proposed PLL performance was compared with the conventional SRF-PLL. The results verify the validity of the proposed PLL showing its ability to maintain stable operation under various conditions.