Two-Layer Current Sharing Control of Parallel Connected Grid Inverters with Specified Line Impedance Uncertainties

Abstract

Parallel operation of grid inverters for AC nanogrids requires robust power sharing as well as fast dynamic responses. This paper proposes a two-layer current sharing control scheme for parallel connected inverters with specified uncertainties of line impedances. The inner layer controller is designed to achieve a desired output impedance with specified voltage THD under nonlinear rectifier load. The outer layer controller is designed to provide robust current sharing control by using virtual impedance control with specified line impedance uncertainties. Simulation and experimental verifications have been carried out to illustrate the performance of the proposed two-layer current sharing control scheme.