Energy Management Strategy Optimization For The Plug-in Serial Hybrid Bus And The HCU Hardware-in-the-loop Tests

Alternative vehicles make active response to the call of energy conservation and emission reduction.As a kind of alternative vehicles,plug-in hybrid electric vehicle(PHEV)can not only ensure the range,but also to maximize the use of electric drive as far as possible so that it can play an important role in energy conservation and emission reduction.This paper focuses on the research of vehicle energy management strategy optimization for a plug-in serial hybrid bus.Firstly,the structure of the powertrain of the plug-in serial hybrid bus is analyzed.Based on Matlab/Simulink platform,the engine model,the ISG motor model and the drive motor model are built using the experimental data.The power battery model is built using the equivalent circuit model with uncertain parameters.The driver model is built based on PID control.The vehicle longitudinal dynamics model is built using vehicle running equation and the fuel consumption calculation model is added to the simulation model.These parts are connected with the vehicle hybrid control unit(HCU)to form a closed loop simulation system.It provides a basic simulation test platform for optimal energy management research later.Secondly,the vehicle control strategies are designed and the energy management strategies are optimized.Rules are formulated to realize the automatic switching between two modes: pure electric drive mode and serial drive mode.Based on the optimization of fuel economy,the equivalent consumption minimum strategy(ECMS)is used to realize the optimal power split between the engine and the battery.Real-time lookup tables are calculated offline and then introduced into the ECMS controller model.In addition,since the too lower or higher temperature may have bad effects on the battery capacity and charge/discharge performance,the ECMS objective function is optimized with consideration to both the battery SoC and the battery temperature,using fuzzy logic to punish battery equivalent fuel consumption.It helps in avoiding high error and high complexity in the SoC estimation process as far as possible.The health management of the power battery is realized directly from the power distribution.Model-in-the-loop simulation tests are run in Matlab/Simulink platform.The results show that the ECMS with mode switching control can not only ensure the stability of the powertrain components,but also maximize the fuel economy.To consider the battery temperature,although the penalty coefficient will sacrifice the fuel economy when the temperature is high,it can protect the battery reasonably according to its actual characteristics,especially when the vehicle has to run for a long time.Finally,according to the "V" model of automotive software development process,the vehicle HCU is developed based on the rapid prototyping.The hardware resources are configured,the CAN matrix is defined and the software is compiled.Then,the HCU to be tested is connected to the NI real-time simulator to build the hardware-in-the-loop(HiL)test platform.The HiL tests results verify the accuracy of the energy management strategy optimization in a real-time environment.