Study On Dynamic Modeling And Coordination Control For The Auxiliary Power Unit Of Extended-range Electric Vehicle

With the gradual improvement of living standards, private cars have become the mainstream of transportation tools. Even though they bring people convenience and comfort, they also cause series of social problems, such as tough traffic management, serious urban pollution, climate change and even worrying national energy security. So in recent years, our country and local government have introduced many effective policies constantly to encourage and promote the development of new energy vehicles and public charging infrastructure. Pure electric vehicles, a great promise, have entered a bottleneck period of difficult charging and short continued driving mileage. Luckily, the extended-range electric vehicle with an auxiliary power unit (APU) added to the pure electric vehicle power-train, appears rightly and develops rapidly. It combines advantages of traditional vehicle and pure electric vehicle and becomes the focus in the field of new energy vehicles.The APU studied in this paper is made of an gasoline engine, an ISG motor and its control systems, which has three working points:idle speed point, economic power working point and rated power working point. Based on an extended-range electric vehicle research project, we found that during the process of APU starting and working points switch from low power point to high power with traditional control strategy, serious torque impact and harsh mechanical noise caused by high speed overshoot appeared, which directly affected the vehicle ride comfort and fuel economy.This paper studies APU starting and working points switch process and analyzes the dynamic speed and torque output characteristics of the engine and ISG motor. By coordinated control of them, new control strategies are developed to improve the APU dynamic response performance. The main content are as follows:(1) Analysis and study of APU control methods. Firstly, elaborate APU control methods on the level of vehicle and APU system respectively. Secondly, make the APU dynamic control be focus in the paper and analyze the technical problems of traditional APU starting control and working point switch control. Lastly, analyze current technologies of control-oriented dynamic modeling for gasoline engine and ISG motor system. All of them lay a solid foundation for the whole paper.(2) APU dynamic modeling process. With help of Matlab/Simulink, I build the mean value engine model and ISG motor system model. According to the Newton’s second law, I establish APU motion equations under different working condition and complete APU dynamic model successfully. Dynamic response performance is verified with step-input in the end.(3) Development of APU starting control strategy and simulation validation. I develop new APU starting control strategy and study carefully the effect of key factors during simulation and prove its advantages by comparative analysis.(4) Development of APU working points switch control strategy and simulation validation. I classify APU working points switch process into two types and develop new switch control strategy according to different types. Then study carefully the effect of key factors during switching and prove its advantages by comparative analysis.In this paper, I complete a kind of APU control-oriented dynamic model and develop new APU starting and working points switch control strategy, which provide some help for research and development of APU product.