An Adaptive Virtual Impedance Control Strategy for Reactive Power Sharing in Microgrids Considering Distributed Secondary Control

In islanded microgrids, droop control is extensively employed for the control of parallel distributed generators (DGs). However, the disparities in line impedance affect the distribution of reactive power and give rise to the emergence of circulating currents. Besides, droop control exhibits differential regulation characteristics, which can cause frequency offset and voltage drop. This paper presents an enhanced droop control incorporating adaptive virtual impedance to achieve precise power sharing. Furthermore, a voltage recovery compensation control strategy is utilized to offset the voltage drops that occur due to the differential regulation and the integration of virtual impedance. Next, the secondary frequency recovery control strategy is adopted to compensate for frequency offset. Besides, the distributed control structure is adopted, which only requires data transmission between the adjacent DGs. Finally, the effectiveness is verified via simulations of an isolated microgrid scenario with four DGs.