Research On Control Strategy Of Hybrid Power System Based On The Analysis Of Battery Thermal Effect

Under the industrial wave of automobile enterprises to promote and research new energy vehicles vigorously,the plug-in hybrid electric vehicle(PHEV)equipped with dual-power sources can replenish energy from the grid to save energy and reduce emissions.It will be an important transitional vehicle in the electrification process.However,compared with pure EV,PHEV has a small pack capacity and is often in high-rate charging or discharging conditions,which causes serious battery heating,high temperature rise,battery heat loss and life reduction,also influence the mileage and output performance.Therefore,efficient battery thermal management methods and energy management strategies are crucial to the performance of the vehicle.So the paper relying on the NNSF project,takes a series-parallel PHEV as object,aiming at two major points of poor battery temperature adaptability and high energy consumption,to improve the economy and ensure a suitable battery temperature under all conditions.The project researches on technologies such as battery thermo-electric characteristics,thermal management system control and vehicle energy management.Firstly investigating the status of BMS and HEV from the core technology and molding products.After understanding the development situation and trend of the industry,the integrated liquid cooling heat management and instantaneous optimization strategy are adopted as the system programme and technical route.For the powertrain architecture,determine the key component model and performance parameters,and clarify its working modes.Based on the analysis of components' working characteristics a modular vehicle simulation platform is built by MATLAB/Simulink to provide model support.And by analyzing the heat generation of battery,the necessity of research on the battery thermal effect is proved.Taking a lithium-iron battery as the research object,from aspect of theoretical analysis and experimental verification,the heat generation mechanism,heat transfer mechanism and temperature characteristics of the output performance are deeply studied,and recognizing the heating characteristics qualitatively and quantitatively.Then building a battery thermal effect model and verify its accuracy.Based on the analysis of battery heat generation characteristics,combined with the vehicle model,a set of air-conditioning-assisted battery cooling system is designed.By calculating the heat load in extreme conditions,based on the operating characteristics,the key components are matched and selected.According to the matching results,the system mechanism model is built in AMEsim.Then analysing the influence of coolant flow rate and compressor speed on the cooling effect and energy consumption,which provided guidance for the selection of control parameters.Through the simulation analysis of the rule energy management and battery cooling system control strategy,it is found that the battery can only be ‘passively cooled' and the comprehensive energy consumption is high.Aiming at the limitation of rule control,an energy management strategy considering battery thermal effect is developed.Through simulation comparison,it is found that this strategy can slow down the battery temperature rise rate,reduce the battery thermal decay loss,improve the economy of the vehicle,which verifies the effectiveness of the strategy.The researching contents and results of this paper can provide guidance and reference for PHEV battery cooling system design and vehicle control strategy exploitation.