Research On Ring Equalizer For Lithium Battery Of Electric Vehicle Based On Hybrid Topology

With the intensification of environmental degradation and energy depletion,the development and utilization of clean energy has received extensive attention from the public,and lithium batteries are widely used as energy storage components in applications such as electric vehicles and new energy power generation.Many applications require high supply voltages and require battery cells to be connected in series to form a battery pack.When multiple cycles of charging and discharging,the inconsistency between the battery cells is further improved,if not controlled,it will seriously reduce the effective capacity of the battery,reduce its service life,and even cause explosion and other safety accidents.Therefore,the series lithium battery pack needs to be equipped with a battery equalizer to ensure the safe and stable operation of the lithium battery.This paper adopts a method combining a directed graph and a weighted matrix to model the commonly used equalization circuit structure graphically and analyze the influence of the circuit structure on the equalization path and equalization efficiency.The analysis results show that the ring equalization circuit based on Buck-Boost and switched capacitor can realize the bi-directional ring flow of energy,which can effectively solve the problem of poor equalization of the first and last cells.The use of graph theory provides a new way of thinking for analyzing circuits with complex structures and gives a great impetus to the formulation of equalization strategies and the proposal of new circuit structures.The proposed double-layer ring equalization circuit can effectively optimize the circuit equalization performance.The operating principles of Buck-Boost equalization circuit and switched-capacitor equalization circuit and the influence of circuit parameters on the equalization efficiency are analyzed separately and verified by simulation to provide a theoretical basis for optimizing the structure of the loop equalization circuit.Taking 12 battery cells as an example,this paper establishes a two-layer ring equalization structure for lithium batteries in electric vehicles based on hybrid topology.The bottom module uses the hybrid equalization structure of Buck-Boost circuit and switchedcapacitor circuit,and the top module also uses the hybrid equalization structure of BuckBoost circuit and switched-capacitor circuit.The working principle of Buck-Boost equalization circuit and switched-capacitor equalization circuit and the influence of circuit parameters on the equalization efficiency are analyzed respectively.The simulation results provide theoretical basis for optimizing the structure of the ring equalization circuit Finally,an experimental prototype based on STM32F103C8T6 single chip microcomputer is designed.Taking four battery cells as an example,the main circuit,voltage acquisition circuit and drive circuit are constructed.The experimental results of the prototype verify the correctness of the theoretical analysis.The ring equalization circuit has good voltage equalizing performance.