Novel seamless transfer strategies for fuel cell inverters from grid-tied mode to off-grid mode

This paper proposes two novel control methods for the transition of the fuel cell inverter from grid-tied mode to off-grid mode. By means of inverter output voltage amplitude regulation or phase regulation, the current through the static transfer switch is forced to decrease to zero. Since the inverter is changed from current control mode to voltage control mode before the static transfer switch is turned off, there is no voltage overshoot on the load on the instant when the static transfer switch is turned off, therefore smooth transfer is obtained. Simulations based on PSpice model are provided to verify the theory