Parallel-connected legs in a grid-tied inverter system for distributed generation

Grid-connected high-power inverters are often used in distributed generation and power quality systems. Those inverters have to handle high currents in order to achieve high power values without resorting to higher voltages. Connecting inverter legs in parallel is a proper way to achieve such high currents. Such parallel connection is made by means of inductors and achieving balanced currents among the legs becomes a critical issue. Circulating currents may produce additional losses and stress to the converter’s power devices. Therefore, they should be controlled and minimized. An efficient technique to achieve such balance is presented in this paper. The proposed strategy has been developed on a grid-connected three-phase system. Each phase of the inverter is made up of three legs in parallel. Besides, the control implemented in this work allows full regulation of the power factor. This way, any desired power factor value can be achieved in order to meet grid-connection requirements. Simulation and experimental results are shown in this paper.