Analysis And Improvement Study On Full Wave Voltage Multiplier Cell Equalization Circuit

The proposal of "3060" carbon peak carbon neutral target has driven the new energy electric vehicles to a new stage of development,and the closely related power battery energy storage technology is also becoming increasingly mature.As the voltage of energy storage battery is low,it cannot reach the voltage level of electric vehicles,so it usually needs to be used in series groups.However,due to the differences between the battery cells,such as capacity,impedance,self-discharge rate and working environment,it can lead to overcharge or overdischarge in the process of charging and discharging,thus weakening the performance of the battery pack,shortening the cycle life and increasing the safety risks.Therefore,the introduction of equalization circuit in the battery pack to reduce the voltage difference between battery cells becomes an important means to improve the efficiency of the battery pack.In this paper,we analyze the full-wave voltage rectification equalization circuit in depth,and propose an improvement scheme to solve the problem that the equalization circuit works in open loop and the battery consumes a lot of energy during long time operation,and design and build an experimental platform to verify the equalization control system.Firstly,we introduce the structure and equalization principle of full-wave voltage rectifier equalization circuit,analyze the circuit operation mode under the equalization and unbalanced condition of series-connected battery pack voltage,study the influence of key parameters on the equalization current,including control frequency,duty cycle,equalization inductor and isolation capacitor,and build a simulation model to verify the correctness of the theoretical analysis.Then,to address the problem that the full-wave rectifier equalization circuit works in open-loop state without feedback circuit,which cannot automatically realize equalization start-stop control and has large energy consumption for equalization under long-time operation,an improved full-wave rectifier equalization circuit is proposed,and the improved circuit is analyzed in detail to give the control scheme and build a simulation model to verify the correctness of the theoretical analysis.The simulation results show that the improved equalization circuit,on the basis of retaining the original operating characteristics of the equalization circuit,solves the problems of the full-wave multiplier rectifier equalization circuit which cannot automatically start and stop and consumes a lot of energy,and also ensures the characteristics of simple circuit structure and easy control.Then,based on the theoretical analysis of the improved full-wave multiplier rectifier equalization circuit,the software and hardware design is carried out to develop a full set of equalization control system for power batteries.The hardware circuit design mainly includes the main control circuit,the battery data acquisition circuit,and the improved equalization circuit.Based on the hardware,we designed and wrote the software programs for battery data acquisition,battery equalization and start-stop control.Finally,the experimental platform of the equalization control system is built and the system is debugged to verify the reliability of the designed battery acquisition system and the correctness of the designed equalization control strategy and equalization start-stop circuit.The experimental results show that the designed battery acquisition system has good acquisition accuracy,the equalization start-stop circuit and control strategy can realize the equalization start-stop control independently,the circuit structure is simple and easy to control,and the energy consumption of the battery in the equalization process is reduced.