Analysis and prevention of prime-mover stalling in a mixed source microgrid

Natural gas powered inverter-based distributed energy resources (DERs) are becoming increasingly popular. In such DERs, the output frequency is decoupled from the prime-mover speed. This is advantageous in terms of improved efficiency and reduced emissions for the internal combustion engine. However, under large load conditions the prime-mover can stall leading to a voltage collapse. This paper presents an analysis of prime-mover stalling in inverter-based DERs. Detailed studies are conducted on a mixed source microgrid comprising both inverter- and synchronous generator-based DERs. A modified active power-frequency droop control technique is proposed for the inverter-based DER to prevent its prime-mover from stalling in the mixed source microgrid.