Research On Control Strategy Of Starting And Steady State Generation Of Free Piston Linear Generator

Since the new century,the rapid development has brought a great test to the carrying capacity of environment and the sustainable development of energy.People are gradually aware of the current rather severe fossil energy crisis and environmental pollution.Therefore,the research of new energy technology and development of emission reduction technology has aroused widespread concern.Free piston linear generator has many advantages,such as wide range of fuel application,low mechanical friction loss and adjustable compression ratio.So it has huge development prospect.In this paper,the mathematical model of the free piston linear generator is established.It includes the combustion chamber dynamic model and gas spring model based on the theory of energy conservation and ideal gas state equation,the linear motor model in three coordinate systems according to the motor voltage equation and coordinate transformation theory.This paper introduces the topology and operation characteristics of PWM rectifier,analyzes the energy flow matching relationship among the components of the system,and based on this,carries out the matching design and configuration optimization of the system,and develops a set of small power modular free piston linear generator.At the control strategy level: In the start-up stage,an oscillation start-up control strategy based on state identification is proposed.By monitoring the movement,the current phase is adjusted to maintain the optimal power output of the motor.Compared with the traditional constant electromagnetic force starting strategy and constant displacement starting strategy,it overcomes the problem of current overload in the starting process of small power system.In the power generation stage,a high efficiency control strategy based on prediction algorithm is proposed.By establishing the reference index of predicted power corresponding to time domain,accurate switch signal is generated.On the one hand,it overcomes the efficiency loss caused by the delay of PWM switching signal,on the other hand,it reduces the noise and loss caused by the unfixed switching frequency.Finally,combined with the project indicators,the mechanism scheme is designed,the three-dimensional modeling,processing and assembly of the prototype are completed,and the hardware platform is built.The software program of the control strategy and the operation interface of the host computer are written,the system function and parameters are tested and adjusted,the system motion characteristic curve is obtained,and the mathematical model of the system is further improved and at last the control strategy in this paper is verified.