The Study Of Power Battery Equalizer Based On The Multi-winding Transformer

The extensive fuel consumption of conventional vehicles is one of the major reasons for environmental pollution and energy shortage problems.Compared to the conventional vehicles,electric vehicles(EVs)use electric energy to drive electrical motors.Electric energy can be obtained from wind,solar and other renewable energy,so it can alleviate the above problems to some extent.With the advantages of environment-friendly and power saving,EVs have become the most promising vehicles in the automotive markets.In order to meet the requirements of driving power and driving distance,it is required to construct battery packs with hundreds or thousands of single cells connected in parallel or in series.Because that the cells cannot completely have the same parameters,several problems occur.One of these problems is the cell mismatch problem which can reduce the available battery capacity and service life.To solve this problem,this thesis focuses on the study of Lithium-ion battery equalizer and control strategy.The main works of this thesis are listed as follows:(1)The principles and the characteristics of various domestic and abroad battery equalization circuits are analyzed and compared.The development trend of equalization circuit is pointed out in the thesis.(2)A novel Lithium-ion battery equalizer is proposed.This equalizer uses multiple two-secondary windings which can prevent short-circuiting problems and achieve modularization and energy balancing.By using this equalizer,the dynamic performance and the life of the battery pack can be promoted.To make the proposed equalizer work,a battery equalization system is set up.In this equalization system,DSP TMS28335 is used in the Electronic Control Unit(ECU)and LTC6802 is applied as the battery voltage monitor.By using the CAN bus,the data transmission,is realized.(3)The design of the softwar part of the equalization system is proposed,including the software design of ECU,voltage monitor and CAN bus.At the same time,a double-fuzzy logic control(DFLC)method is proposed to achieve a better balance performance of the equalizer.(4)To verify the validity of the equalizer,a series of equalization experiments are conducted under the static,charging and discharging conditions respectively.After these experiments,the analyses of the experimental results are given.The results show that the proposed equalizer has good equalization ability and can reduce the cell mismatch problem.In this paper,a battery equalizer is designed which can be widely used in the electric vehicle battery management system.By the multi-winding transformer,modularization and energy balancing are realized.The equalizer has an important significance for extending the service life of power battery and improving the driving performance of EVs.