A Control Strategy for Parallel Operation of Multi-inverters in Microgrid

For multi-inverters parallel operation in microgrid,the output impedance of inverters and the line impedance between the inverters and point of common coupling are always different,which can result in big circulating current and lower precision of power sharing among inverters.The traditional droop control strategy and the influence of output impedance of the inverters were analyzed,and a droop control strategy based on voltage and current double-loop for multi-inverters parallel operation in microgrid was proposed by introduction of inductive virtual impedance.The introduced virtual impedance made it possible that the output impedance is only depended on the filtering inductor.The effect of the output resistance of parallel inverters was reduced.Considering the effect of line impedance,an novel improved droop control strategy was proposed.By modifying the droop coefficients,the effect of line impedance on paralleling current sharing was reduced and the system performance of parallel inverters was improved.Both the simulation and experimental results demonstrate that the control strategy is correct and effective.