The Design And Development Of Vehicle Control Unit For Pure Electric Vehicle With Composite Power Of Battery-Ultracapacitor

In recent years, in pace with the problems of environmental pollution and resource shortage becoming more and more serious, new energy vehicle especially pure electric vehicle receives more and more attentions of people, developing pure electric vehicle is regarded as a new trend to alleviate development issues of automotive industry. Since single power electric vehicle is faced with problems such as short power battery life and poor dynamic performance, the study on composite power which is introduced high power density auxiliary energies such as ultracapacitor has become one of hotspots in the field of electric vehicle power system. As the highest level of vehicle control system, vehicle control unit(VCU) can prolong power battery life, enhance vehicle dynamic performance and ensure high voltage safety of vehicle by managing energy system, power system and high-voltage system effectively. This paper analyzed the current development situations of pure electric vehicle, composite power and VCU, then the VCU was designed and developed based on pure electric vehicle with composite power.Firstly, the structure of composite power was selected to be "ultracapacitor and bi-directional DC/DC in series and parallel with power battery" by analyzing and comparing with other structures, and composite power system parameters were confirmed according to the parameters of sample vehicle; The multivariable fuzzy control strategy of power system was set out in order to give full play to ultracapacitor’s advantages including high power density, fast charge and discharge, and the model of power system key components were built with MATLAB/Simulink.Then offline simulation experiment was carried out. The result showed that the control strategy realized control purpose well, and the advantages of the composite power were exerted.Secondly, the function and structure of VCU were analyzed and confirmed, then the VCU hardware including circuit schematic and PCB were designed; At the same time, wrote the driver layer code manually and used automatic code generation tools to generate the upper main program. Then on this basis, developed the software of VCU.Thirdly, in order to verify VCU hardware’s rationality and reliability, electrical integrity experiment, structure reliability experiment and electromagnetic interference detection experiment were carried out; Then, set up the test platform, and executed hardware-in-the-loop(HIL) simulation experiment for VCU, and its performance was validated.Finally, in view of high voltage and large current characteristics of electric vehicle power system, the high voltage safety strategy was formulated in aspects of high voltage electrify, high voltage dynamic monitoring and passive safety based on composite power electric vehicle high voltage structure characteristics; Then the high voltage safety system of electric vehicle was designed based on VCU.