Design of a Complex-Variable-Based Droop Control Strategy for Island Microgrid

In islanded microgrids, frequency acts as a global variable to regulate active power sharing among distributed generation (DG). Nevertheless, stochastic load fluctuations may induce frequency deviations and oscillations, undermining the system's stability. Furthermore, when multiple DG units are paralleled to feed the Point of Common Coupling (PCC), the inherent line impedance introduces power coupling. This coupling phenomenon deteriorates the dynamic response and reduces the stability of the microgrid. This paper proposes a complex-coefficient droop control strategy to address frequency instability and power coupling in islanded microgrids. By establishing a fixed-frequency microgrid, the strategy eliminates frequency deviations caused by load fluctuations. It further uses line impedance to design complex-coefficient droop equations applied to the voltage dq-axis components, achieving active-reactive power decoupling. Simulation results demonstrate the strategy’s effectiveness in enhancing stability and feasibility.