Research On Three Phase Grid-Connected/Stand-Alone Inverter Transfer Between The Two Modes

With environmental pollution and excessive consumption of resources, wind energy, solar energy and other new energy sources are attracted more and more attention. The purpose of alleviating the situation of resources shortage and meeting human demand for electricity makes new energy technologies and distributed generation (DG) technology developed rapidly, which can ease the pressure of the large grid. As an unit of the system of DG—the three-phase grid-connected inverter not only can work in stand-alone mode, but also can work in grid-connected mode, which will become an inevitable trend. So, there is a far-reaching significant to research the smooth transfer between stand-alone mode and grid-connected mode.In this paper, the mode of three-phase grid-connected inverter was analyzed, and the control parameters under the different modes was designed and proved by simulation. Then the different parameters, different control modes, and different operating conditions were thought which could affect the output voltage of inverter and the current of grid, when the two modes transfer each other. And the same time the phase lock loop was also designed. Finally, this paper proposing the control strategy—the inverter was in current control mode from stand-alone to grid-connected, on the other transfer, the inverter was in voltage control mode.The experimental platform was built and the theory involved in this paper was verified by the result of experiment which was studied and compared.