Mode transition control strategy for multiple inverter based distributed generators operating in grid-connected and stand-alone mode

This paper proposes a novel automatic mode transition control strategy for multiple inverters to operate in grid-connected and islanded modes without communication. When grid is available, all the inverters operate in grid-tied current control mode and transfer available power to the grid. On grid failure, they automatically shift to conventional droop control mode and shift back to grid-tied current control mode when the grid becomes available. The control signals for mode transition are generated by state machines specific to each inverter. The state machine has appropriate delays to facilitate smooth mode transition. Feasibility of the proposed control strategy is substantiated using MATLAB/SIMULINK simulation results.