Improving Reactive Power Sharing in Microgrids by Adaptive Virtual Impedance Approach

As a new emerging approach, Virtual Synchronous Generator (VSG) control for interfacing inverters in renewable energy-based microgrids has attracted significant research interest. However, VSG control cannot ensure proportional reactive power sharing among distributed generation (DG) units when unequal transmission line impedances are involved, although active power sharing remains proportional among DGs. In this paper, an adaptive virtual impedance approach is proposed, which can be incorporated in a VSG control to alleviate impedance difference at the inverter output and improve reactive power sharing among DGs. It is applicable to any VSG control, either conventional or modified types. The proposed approach is implemented on a modified VSG control scheme, known as Fuzzy secondary controller (FSC)-based VSG control, in this paper. Its performance is demonstrated through several case and sensitivity studies using MATLAB/Simulink simulation; and is further validated by comparing with an existing method.