Improving Reactive Power Sharing in Islanded Microgrid with Transient Reactive Current Injection

Accurate load power sharing and voltage regulation are two critical control objectives to ensure power quality and reliable operation of islanded microgrids. Although voltage regulation can be achieved using a secondary control loop, the inaccuracy of reactive power sharing is a prominent issue due to the varying impedance of lines connected to distributed generation sources. One of the techniques for accurate sharing of reactive power is to modify the production reference voltage by the droop control method. In this paper, a control strategy is proposed to improve the accuracy of reactive power sharing among distributed generation units of islanded microgrids. The proposed control method was based on transient reactive current injection to modify the production reference voltage of the droop control method. The reactive power-sharing error was reduced by changing the reference voltage. In addition, the proposed controller did not require a communication link between distributed generation sources for implementation. The effect of the proposed controller on the stability of the system was demonstrated using the reduced-order small-signal model. To evaluate the performance and effectiveness of the proposed control strategy, it was implemented on an islanded microgrid consisting of three distributed generation units. The simulation results showed the proper performance and efficiency of the proposed method.