Distributed Cooperative Control for Voltage Unbalance Compensation in an Islanded Microgrid

In this paper, a new distributed cooperative control for voltage unbalance compensation in an islanded microgrid is proposed. In order to decrease the negative impacts of impedance of distributed lines upon conventional negative-sequence reactive power-conductance droop control, a cooperative control component is added to accomplish the trade-off between the accuracy of negative-sequence reactive power sharing and voltage unbalance compensation. The proposed controller is applied in the multi-agent architecture in which each DG uses localized information and nearest-neighbor communication to collectively perform control actions. Moreover, a complete negative-sequence small-signal model of a microgrid, including droop-controlled DGs, distribution lines and loads is established to analyze the stability. Finally, experiment results of a test microgrid at a real-time measurement are shown to verify the effectiveness of the proposed strategy.