Synchronisation of weak microgrid with bulk power system

A microgrid including distributed generation sources (DGSs) is generally connected to a bulk power system to provide power to its local loads. The point of common coupling between the bulk power system and microgrid should meet relevant standards. The microgrid becomes a weak system with unbalanced and distorted voltages after it is disconnected from the bulk power system. A synchronisation controller for the DGS considering imbalanced three-phase voltages and harmonic voltages is presented. The proposed method can be implemented without altering the traditional phase-locked loop circuit. No filters and compensators are needed in the proposed method. Simulation results reveal that the proposed method is applicable.