A Load Control Strategy for Stable Operation of Free-Piston Electromechanical Hybrid Power System

Abstract

Abstract The free-piston electromechanical hybrid power system (FEHS) affords the advantages of a simple construction and high thermal efficiency due to the removal of the crankshaft. However, the unrestricted trajectory of the piston linkage assembly (PLA) also gives rise to challenges for stable operation during the process of startup or operation. In order to realize the stable operation of free-piston electromechanical hybrid power system, this paper proposed a load control strategy. First, a dynamic model is established through thermodynamic and electromagnetic theory, and its effectiveness is verified by experiment and simulation. On this basis, a coupling load control model based on linear active disturbance rejection control (ADRC) is developed. The reliability of the proposed load control strategy is validated under different interference fluctuations. The simulation results demonstrate that no matter whether the interference occurs during the startup process or the operation process, the proposed control strategy exerts effective limiting function over the piston linkage assembly and maintain its stable operation. Moreover, compared with the proportion integral differential (PID) control strategy, the proposed strategy exhibits faster response times and a smoother startup process. The compression ratio fluctuation range was reduced from 0.1 to 0.001, and the control accuracy has been greatly improved.