Study On Preheating Control Strategy Of Power Battery Pack For Range-extended Electric Vehicle

The Car has changed the human life while bringing energy shortage and environmental pollution, so new energy vehicles become the development direction of the automotive industry. At this stage, due to the high cost and low specific energy density limit the development of power battery pack, range-extended electric vehicle becomes an important direction of new energy vehicle development at the present stage. Range-extended electric vehicles still exists the disadvantage of power battery pack’s poor performance in low temperature which seriously affects its pure electric driving range and indirectly increases the cost of vehicles.In order to solve the problem, combined with the research group range-extended electric vehicle structural features, we designed a battery pack preheating system, and developed preheated vehicle control strategies while considering the battery low temperature to achieve the battery preheating in low-temperature environment during driving. The main contents are as follows:(1) Thermal characteristics analysis of power battery at low temperature.Reading a lot of literature, researched on the components 、reaction mechanism and heat generation mechanism of the lithium battery. Researched the correspondence of lithium battery internal resistance 、 capacity and open-circuit voltage in different temperatures by the test methods. Define the critical parameters of battery pack model which reached in the paper.(2) Range-extended electric vehicle modeling and simulation. Analysis research group range-extended electric vehicle power structure, according to the parameters matching results established vehicle power system model based on AMESim;Determined the vehicle working models and the control system architecture, based on the thermostat control method developed the vehicle CD(Charge Depleting) + CS(Charge Sustaining) control strategy and determined the engine operating pointaccording to the driving conditions in CS mode;Compared battery pack temperature,energy efficiency in vehicle CD mode and the total energy consumption in the overall condition in different ambient temperatures, obtain that the internal resistance of power battery pack consumed more energy in low temperature, resulting in pure electric vehicle mileage shortened and the total energy consumption of the vehicle increased, so the battery pack need to warm up.(3) Battery pack preheating system designed and control strategy developed.First, based on vehicle power system design utilizing the waste heat of the engine cooling system battery pack preheating system structure; secondly modeled power battery pack preheating system and integrated into the extended range electric vehicle system model in AMESim; finally based on the original vehicle CD + CS control strategy developed a preheated vehicle control strategies for the low temperature, and increased the preheating extended-range CS mode.(4) Utilize battery pack built preheating system vehicle model and the battery pack preheating control strategy verified the feasibility low temperature preheating control strategy, and compared the total energy consumption of vehicle on working conditions in different control strategy, especially at ambient temperature of-20℃,the vehicle energy consumption in the entire conditions can be reduced by 20% with the battery-preheating conditions. Improved the brake strategy and optimized the low temperature battery pack preheating control strategy while consider low battery pack charge limitation conditions. The simulation results show the feasibility of strategy.