Proportional power sharing control for parallel-connected inverters

Parallel-connected inverters are important parts of a microgrid. Each inverter operates with a load in proportion to its capacity is necessary. This paper proposes a control strategy for paralleled three-phase inverters of different capacities based on droop control method. The system impedance of an inverter is kept inductive by setting a virtual reactance, and proportional power sharing is achieved through proper design of the different virtual reactance values. The control strategy can also eliminate circulating reactive power in the inverters in steady state and suppress over-current of inverters in dynamic process, which are the drawbacks of the conventional control strategy. The experiments on two inverters in parallel prove the validity of the proposed approach.