Gas engine generators have been recognized as a set of beneficial generating units for producing electric power owing to their high efficiency, low emissions and appropriate fuel price. However, the major drawback of gas engine generators is the weak transient performance during sudden load change. The reason is that the engine's mechanical system cannot quickly respond to the demanded torque. Therefore, a change in load causes a large engine speed deviation, especially in stand-alone mode. If the engine speed deviation exceeds the allowable limits, the system operation will be shut down. To fix this drawback, this paper introduces the virtual synchronous generator control method combined with an additional energy storage system to the stand-alone gas engine generator. In this paper, the applied virtual synchronous generator control scheme is presented. Compared to the constant-voltage constant-frequency control method, the benefit of virtual synchronous generator control method for the gas engine generator is evaluated by simulation study in PSCAD software. The energy-variables-based feedback control structure is adopted for the control of energy storage system. The required capacity of energy storage system is estimated. To verify the effectiveness of proposed control structure, simulation is conducted under load connection and load removal cases. Finally, an experimental study is carried out for the same configuration of simulation model using a real gas-engine generator set up.
