A method for microgrid connected fuel cell inverters seamless transitions between voltage source and current source modes

This paper proposes a novel seamless transfer method for microgrid connected fuel cell inverters (FCIs) between voltage source and current source modes. In order to protect the fuel cell, the FCI output power should be restricted when the microgrid frequency is greatly disturbed. In this sense, the FCI is transfered from voltage source mode to constant current source mode. Meanwhile, the FCI is transfered from constant current source mode to voltage source mode until service can be restored. The proposed method can cooperatively work with well developed virtual synchronous generator (VSG) control algorithm so that these FCIs are able to share load among them as well as subsist under transient events of the system. Theoretical analysis and experimental results validate effectiveness of the proposed method.