A seamless transfer algorithm based on frequency detection and feedforward control method in distributed generation system

This paper proposes a control strategy for grid interactive Power Conditioning System (PCS) which has a feedforward voltage control based on grid frequency detection. The PCS should supply the power to the critical load, regardless of the grid condition. In order to provide the power to the critical load continuously, the PCS should operate two modes. One is Grid-Connected mode and the other is Stand-Alone mode. It is important to know the grid condition to decide operation modes. This paper proposes a control method based on the grid frequency to detect the grid condition and consists of a current controller and a feedforward voltage controller. The grid frequency detection is able to reduce the grid fault detection time and a feedforward voltage controller helps voltage regulation fast. This proposed control strategy is verified by the simulation and experimental results.