Tertiary Control Strategy for Optimal Voltage Unbalance Compensation in Island Microgrid

In the multi-bus islanded microgrids, the power quality requirements for different areas and buses can be different. This paper proposes a hierarchical control to realize optimal unbalance compensation for satisfying the power quality requirements in different areas. Primary and secondary controllers are applied to realize unbalance compensation for the critical bus(CB). In the secondary control, the voltage amplitude and frequency deviations of system are restored to realize voltage unbalance control and share the power equally. Tertiary control, using the artificial bee colony(ABC) optimization method to adjust the compensating effort of each DG considering the voltage unbalance limits in local buses and DG terminals. This method realizes accurate voltage unbalance control, and at the same time, to make distributed generators (DGs) equally share the compensation efforts. Finally, the simulation and experiment results demonstrate the validity and feasibility of the proposed method.