A new control strategy of uninterrupted distributed generation system

In order to improve power reliability of emergency loads, seamless transfer between grid-connected and stand-alone modes is the first issue to be concerned. This paper puts forward a new topology of grid inverter. By the use of two switches, the distributed generation (DG) system can support emergency loads in both grid-connected and stand-alone mode. When the main grid is out of electric power, we control the grid-connected switch by adding an active voltage amplitude disturbance. Since it uses voltage control methods in two modes, it won´t have the change of modes. So, it can truly realize seamless transfer to supply stable and continuous electric power.