Study On Energy Management Control Strategy For Extended-Range Electric Bus

Extended-range electric vehicle can overcome the short driving range of a pure electric vehicle. Compared to conventional hybrid electric vehicle, it has larger capacity of battery, lower dependence on fossil fuels, and relatively simple powertrain structure which gets rid of complex dynamic coupling device. All the above make extended-range electric vehicle become the research direction of new energy vehicles, and it’s also the best model for the transition from the traditional internal combustion engine vehicles to the electric vehicles. Therefore, this is important significance to research the key technologies of extended-range electric vehicle for promoting the market process of new energy vehicle.In this paper, an extended-range electric bus is taken as the research object. The research on parameter matching of powertrain, system modeling and energy management control strategy is carried out. The article focused on the application of energy management control strategy based on dynamic programming algorithm. The main research contents and conclusions are as follows:According to the powertrain structure and working principle of the extended-range electric bus, combined with the performance parameter index, a parameter matching method for key components of the powertrain is presented. And the main parameters matching of the power system is achieved. The forward simulator model of extended-range electric bus is built by combining experimental modeling and theoretical modeling approach, which lays the foundation for the simulation of energy management control strategy.For the operating characteristics of extended-range electric bus, the vehicle operating mode is proposed according to the different driving range and the change rate of the battery charge state. And the control target of energy management control strategy under different operating modes is analyzed. Based on the CDCS control strategy of the traditional hybrid electric vehicle, three kinds of energy management control strategy of extended-range electric bus are proposed. Taking power-following multi-point thermostat control strategy as an example, using NSGA- II optimization algorithm to optimize the APU start-stop logic and key parameters in order to avoid the frequent start and stop of engine and achieve good fuel economy and emission performance.Based on the global optimization theory and the characteristics of the city bus, the energy management control strategy of the extended-range electric bus with dynamic programming algorithm is proposed. The backward simulation mathematical model is built, and the proposed control strategy is verified by simulation. The simulation results of one cycle are directly applied to the continuous 45 cycles to reduce the calculation time. The mix control strategy that combined pure electric mode with fixed SOC-change-rate extended-range mode is proposed to meet the demand of different driving range. Finally, the control rules are extracted from the dynamic programming off-line optimization results. The energy management control strategy based on the control rules is obtained. The simulation results show that, the application of dynamic programming algorithm to energy management control strategy of extended-range electric bus can achieve the global optimal control in the guarantee of the power and driving range demand.Based on hardware in the loop simulation technology, the dSPACE hardware in loop test platform of extended-range electric bus is built. The control effect of the control strategy based on the extracted control rules is verified. The test results show that the proposed control strategy can meet the requirements of real time operation, and the control effect is the basically same as the optimal control which is obtained by off-line optimization of dynamic programming. Then, the test bench for the powertrain of extended-range electric bus is built. And the speed control test of auxiliary power unit(APU) is carried out, including the setting of the PID control parameters and the step test of the rotation speed. The test results show that the control effect is good and the speed control of APU is basically satisfactory, which is the basis for the verification of the energy management control strategy.