Robust Droop Control of AC Microgrid Against Nonlinear Characteristic of Inductor

This paper investigates the effect of nonlinear characteristic of filter inductor on power sharing performance of droop-controlled microgrid, and presents a robust droop control strategy to implement proportional reactive power sharing with immunity to nonlinear characteristic of filter inductor. Considering current-dependent soft-saturation natures of filter inductor, time-variant average model of inductor is first established to reveal the nonlinear inductance characteristic. Then, output impedance model of inverters with consideration of nonlinear inductor is derived to analyze the effect of nonlinear inductor on reactive power sharing characteristic. Furthermore, a robust droop control strategy is proposed to mitigate the effect of nonlinear inductor on reactive power sharing and implement proportional reactive power sharing under different load profiles. Simulation and experimental results show that the proposed droop control strategy is able to perform desirable power sharing with a good capability to reject nonlinear characteristic of filter inductor.