Muiti-Module Isolated Half-Bridge Converter For Battery Pack Voltage Equalization

The differences between single cells of series battery pack will lead to overcharge or overdischarge of single cells,which not only affect the capacity and service life of the battery pack,but also affect the safety of the battery pack.In order to meet the requirements of equalizing voltage for series battery pack,this paper proposes a multi-module half-bridge isolated voltage-sharing circuit and carries out related research.Firstly,this paper analyzes the circuit topology and working principle of multi-module half-bridge isolated voltage equalizing circuit.According to the operating characteristics of the circuit,the basic equalization control strategy is proposed.The simulation of the series battery pack in the static state,the charged state and the discharged state is completed,and the voltage equalizing circuit can achieve a good voltage equalizing effect.Then,for the 24-cell battery pack,the main circuit,power supply circuit,transformer,data acquisition circuit,control circuit and digital control system of a multi-module half-bridge isolated voltage-sharing circuit based on Ga N device was designed,and low power experiment platform was built.In addition,the theoretical analysis,simulation,programming and experiment of the control strategy based on the average voltage,the minimum voltage and the predicted voltage was completed.Experiment results show that these three control strategies can achieve voltage equalization basically,but they all have deficiencies.The average voltage control strategy has the problem that the voltage of the low-voltage battery rises slowly in the late stage of voltage equalization;the minimum voltage control strategy causes unnecessary energy loss;the voltage equalization effect of the predicted voltage control strategy is greatly affected by the calculation accuracy of the predicted mean value.Finally,a voltage equalization strategy based on the highest and lowest voltage boundary is proposed.The voltage equalization experiments of the series battery pack in the modes of standing,constant current charging and constant current discharging were completed.The experimental results show that compared with other voltage equalizing circuits,the circuit proposed in this paper can better improve the consistency of the series battery pack.