The Control Strategy And Traction Battery System Of Hybrid Electric Vehicle

Energy shortage and environment pollution are two serious problems that can prevent the world from developing forward rapidly. In this case, HEV's(hybrid electric vehicle) are the key to solve the problems. It has advantages in many fields, such as technology, economy and environment. To improve on the control strategy design of HEV is an important way to enhance fuel efficiency and reduce pollution emission. The traction battery performance testing and management system are two important parts of HEV's.In this thesis, According to the driver's requirements and the distributed control system based on parallel structure for XL2000 HEV, five operation modes are defined and mode changing figure of the HEV is built. In the system, based on control requirement for the vehicle, the torque management strategy on the engine and motor is proposed according to the characteristic parameter and the three principles which include vehicle drive first, traction battery energy keeping, regenerative brake energy reuse. Based on the HEV, the control system model is built and the control strategy is simulatedIn the control of HEV, traditional tracking speed technology is used. According to the torque management strategy, the target torque is distributed to the engine and the motor, and the inverse torque control is implemented on engine and motor based on MAP to resolve the issue of the combination drive of the motor and the internal combustion engine. Thus the speed tracking control is achieved.For the requirements of the practical application, C8051F020 and MC68HC908GZ16 form the test and control system as control core in major- server structure. At the same time, the related hardware, software for the battery management system and CAN bus are designed. Moreover, on the basis of the analyzing the charging and discharging process of traction battery in running electric vehicles, a equivalent electric circuit of Ni-MH battery and its parameter model are proposed in detail. And a method to estimate SOC dynamically based on stable open voltage and state space is also proposed.The distributed traction battery performance test system is designed which include temperature tester including measure point, voltage tester including many batteries, charging device and discharging device based on industrial computers and RS485.Thealgorithms of constant current discharging, constant resistance discharging and constant power discharging are designed. Traction battery discharging control is realized by controlling power MOSFET connect or break which connect to the traction battery. Using PWM impulse modulation theory to adjust the discharging current enlarge the current regulation range. All this work built the experiment environment to simulate the traction battery working in the running hybrid electric vehicles.