Design of Parallel Inverters for Smooth Mode Transfer Microgrid Applications

In this paper, smooth mode transfers and accurate current sharing are performed in a multi-inverter-based microgrid system by the designed system level controls with control area network communication. Controllers of individual inverters within the microgrid in both grid-tie and islanding modes are also designed to ensure high-quality output waveforms. The mode transfer tests are conducted with an inverter-simulated grid to define the proper transfer procedures. Experimental results show that the inverters can provide stable outputs in different basic microgrid operation modes. With the designed current sharing scheme, the output current is equally shared among paralleled inverters without noticeable circulating current. Both the simulation and experimental results of mode transfer show that the multi-inverter-based microgrid system is able to smoothly switch between the grid-tie and islanding modes to guarantee an uninterrupted power supply to the critical loads within the microgrid.