Simulation study on the operating characteristics of FPEG based on variable load control

To stabilize the operation of free-piston engine generators (FPEGs), a variable load control strategy is proposed to regulate piston motion. By dynamically adjusting the equivalent load to control the system’s total resistance, the strategy alters the system circuit current, thereby modifying the electromagnetic resistance on the generator rotor and effectively constraining piston movement. However, this control method also impacts the operating characteristics of the FPEG. To investigate these impacts, simulations were conducted by varying key parameters, including piston mass, heat release, ignition position, and valve overlap length. Results indicate that these factors significantly influence the relationship between compression ratio and peak cylinder pressure. In single closed-loop control, controlling one parameter cannot determine another; instead, control objectives must be prioritized based on specific requirements. This study provides theoretical insights for developing closed-loop control strategies to ensure stable FPEG operation.