Robust controller design for parallel multi-inverter systems using µ-synthesis

In this paper an average current sharing mu-based robust controller for parallel multi-inverter systems is presented. There is one common output voltage controller to achieve low total harmonic distortion (THD) and good regulation. Each inverter module has also a robust current controller to track the averaged output current. This loop provides equal current distribution between inverters. The command for the output current loop is calculated in average current sharing center (ACSC). The controllers are designed based on mu-based robust control to guarantee robust stability and performance in presence of filter and load parameter variations. A novel method to model rectifier loads as a linear load with a disturbance has been proposed and the controller has been designed to compensate for this disturbance. Simulation results for a two-inverter system with linear and nonlinear loads have demonstrated the feasibility of the proposed control method in providing low THD, good regulation, equal current sharing and fast dynamic response.