Virtual Impedance‒Based Adaptive Droop Control to Improve Reactive Power Sharing for Inverter-Based Microgrids

With recent advances in power-electronics, inverter-based microgrids are gaining great attention. Droop control is one of the main methods to share the real and reactive power among distributed energy resources (DERs) in an islanded microgrids. Due to different characteristics of microgrid feeders, reactive power sharing is not fully accurate and consequently, some DERs may face overload. To address this problem, this paper presents a droop-based method using virtual impedance concept in the DER control system. The resultant voltage drop on the virtual impedance increases reactive power sharing accuracy. To adjust this virtual impedance, the local controllers of DERs exchange the required data with the microgrid management center using the low bandwidth communication links. Then, a virtual impedance‒reactive power droop characteristic is proposed to calculate the value of virtual impedance. The slope of this characteristic is adaptively adjusted based on the microgrid load. To verify the effectiveness of the proposed method, various scenarios are tested on the benchmark low voltage microgrid network.