Demonstration of an Advanced Rectification Strategy on a Linear Generator for Better Electricity Quality

This paper focuses on the challenges of the free-piston internal combustion linear power generation system, which is characterized by a wide frequency and amplitude variation range of output electric power and difficulties in rectification. The study delves into the power generation characteristics during the system’s stable operation and explores strategies for rectifying three-phase electric power. A mathematical model of the power generation system has been established. The model of the linear motor has been verified, and an in-depth analysis of the electric power output characteristics has been carried out. On this basis, this paper proposes several rectification schemes, including uncontrolled rectification, PWM rectification based on a PI control strategy, and compound control based on model predictive sliding mode control. In terms of control strategy, a model predictive sliding mode compound control algorithm is introduced to optimize traditional PWM rectification. By comparing and analyzing the electric power output effects under different rectification schemes, this paper aims to explore the rectification strategy most suitable for the system. Simulation results indicate that while uncontrolled rectification can achieve power conversion, it leads to further phase current distortion on the linear motor side. This paper examines the last two types of rectification strategies in terms of robustness, accuracy, and responsiveness. It is found that model predictive sliding mode compound control performs better than PI control. It can stably regulate the output voltage, and the phase current on the linear motor side will not be distorted. It is more suitable for power processing in this system.