Flexible Power-Sharing Control for Inverters-Based Microgrid Systems

This paper proposes a flexible method for power-sharing control of single-phase AC Microgrid or sub-system that operate inverters in parallel to supply the demand. The Photovoltaic (PV) system, coupled with batteries, energized each inverter. Solar power data from the equator city area were included in the PV system for simulation with its dynamics due to weather fluctuation. The proposed power-sharing control approach combined with integral action to improve the power quality and power-sharing accuracy. It conveys three considerations for flexible power-sharing: using virtual load voltage and the frequency at grid connection terminal (i.e., point of common coupling) in the controller without direct measurement to avoid using external communication, applying those virtual values to calculate the required parameters for an accurate power-sharing and proposing a concept of extended traditional droop control coefficient to be able to apply for various line impedances. The presented case study had two inverters supported by dynamics coupled sources from a PV system installed in an equatorial city used in the MATLAB experiment and batteries function block connected in parallel. Those inverters, located in different sub-systems, supplied two sub-systems (i.e., Microgrids) with different line impedance. The presented approach can also work for more than two or multiple sub-system scenarios by replicating the same control mechanism for the new sub-system.