Adaptive Droop Control for Parallel Inverters Power Sharing Based on On-line Identification of Line Impedance

Abstract

A microgrid is mainly composed of renewable energy, energy storage devices and power electronic equipment. The inverter is a power electronic interface that can be connected to the microgrid and plays an important role in the operation and control of the microgrid. In order to reduce or eliminate the circulating current and realize the average output power of each inverter, this paper presents a control method of adaptive adjusting the droop coefficient based on line impedance on-line identification. The realization of this method requires line impedance parameters. Considering that the accuracy of line impedance detection in grid-connected mode is affected by the equivalent impedance of the power grid, therefore, a multi-DG line impedance on-line detection method considering the equivalent impedance of the grid under the grid connected mode is proposed. Simulation and experimental results verify the accuracy and feasibility of the theoretical analysis.