Research On Key Technology Of Battery Management System In Pure Electric Vehicle

With the growing number of vehicles,environmental and energy issues are increasingly becoming prominent,and the electric vehicles will undoubtedly become the solution of those problems. As one of the three core technologies of the electric vehicles, the electric vehicle battery management system completes the functions of the real-time detection and the whole battery pack management.This thesis mainly focuses on the battery management system of the pure electric vehicles and deeply studies the key technologies of the management system. First, based on the pure electric vehicle, the detailed functions of the battery management system are described, and the whole structure and the hardware and software structure are designed according to the functions analysis. And the the battery cell voltage detection technology, the cell equalization technology and the insulation detection technology are deeply reached. Moreover, the local control unit and the battery management unit test environment are respectively set up for testing and validating the key technologies.Considering the cell voltage detect technology and equalization technology of the local electric control unit, a kind of cell voltage detect circuit is introduced based on the currently available cell voltage detection methods. A kind of equalization circuit is designed for the battery equalization, combining the fly-back transformer technology, constant current control and switch circuit. The equalization circuit decreases the voltage spike generated by the transformer and the circuit size. Based on the analysis of the battery character and the equalization circuit, a kind of current equalization closed-loop control method is proposed based on and modified to apply on the practical system.The battery management unit technology includes isolate detect technology, the whole voltage and discharging and charging detect technology. The advantages and disadvantages of several typical insulation detection circuits are analyzed, according to results of the analysis; the insulation detection circuit design is introduced. At last, the thole voltage detection circuit and the overall charge and discharge current detection circuit is proposed.To verify the effectiveness of the equalization control algorithm, cell voltage detect circuit, equalization circuit and insulation detection circuit, the test environments of local electric control unit and battery management unit are set up. The cell voltage detect circuit experimental result proves that the high-precision detection result is archieved by the circuit when the state of batteries are statics or discharge; in addition, equalization control experimental results show that the battery is equalized the equalization circuit which effectively reduces the voltage spike generated by the transformer and circuit size, at the same time equalization control algorithm effectively achieve the equalization of the battery; the insulation detection experimental results show that the insulation detection circuit realize high-precision detection of insulation resistance.