Power-Sharing in Microgrids by Adaptive Virtual Impedance and Fuzzy Logic

Abstract

Microgrid is a new paradigm for current and future energy distribution systems that enable renewable energy integration. The microgrid generally consists of multiple distributed generators interfacing with the grid through power inverters. When the islanded microgrids are concerned, it is essential to maintain the system stability and achieve load power sharing among the multiple parallel-connected distributed generation units. However, poor active and reactive power-sharing is expected due to the influence of impedance mismatch of the distributed generation feeders. The key objective of this work is to estimate the virtual impedance value to nullify the power-sharing errors without the need for communication links. A fuzzy logic controller is proposed to estimate the value for virtual impedance based on the instantaneous real and reactive power demands. The virtual impedance dynamically changes depending on the load demand to compensate for the feeder impedance mismatch, hence called adaptive virtual impedance. The proposed power-sharing control strategies are validated using Matlab/Simulink simulation under four operational scenarios. The proposed fuzzy controller provides precise reactive power sharing and helps to eliminate the need for communication links. In addition, it provides superior dynamic performance.