A novel seamless transfer control strategy based on voltage amplitude regulation for utility-interconnected fuel cell inverters with an LCL-filter

Fuel cell inverters can operate in both grid-tied and off-grid modes and a continuous AC power is required for sensitive and critical loads. This paper proposes a novel control strategy for the transition between grid-tied mode and off-grid mode of the utility-interconnected fuel cell inverters. By the means of output voltage amplitude regulation in the proposed new control strategy, the inverter is operated in voltage-controlled mode before the static transfer switch having been turned off, result in quickly grid current decrease and minimum voltage fluctuation on load. The algorithm is described and discussed in detail, along with the transition performances. Simulations and experiments on a 5kW inverter prototype are provided to validate the algorithm.