Collaborative Voltage Unbalance Elimination in Grid-Connected AC Microgrids With Grid-Feeding Inverters

The control flexibility of the power inverters that interface distributed generation can be exploited to incorporate power quality enhancement features in addition to the usual power management control. This article presents a novel control scheme that achieves voltage balance at any node of an ac microgrid regardless of the impedance value of the power network. The collaborative strategy is devoted to set a specific sharing of the balancing currents, thus avoiding the adverse effects of the unbalance compensation by a single inverter. The control scheme uses a complex form of a proportional resonant controller and a communication link. The article presents the stability and sensitivity analysis and the design guidelines for the control parameters. The performance of the control proposal has been tested successfully in a laboratory microgrid setup. Selected experimental results are presented.