Distributed Charging System With Equalization Function

As a common energy storage body,batteries are usually used in series to improve the voltage and capacity of the whole group.Realizing the balanced charge and discharge of the battery pack is of great significance to improve the effective capacity and prolong the service life of the battery pack,give full play to the performance of the battery pack and guarantee the safety performance of the system.In order to realize the balanced charging of the series battery pack,the centralized charging usually needs to cooperate with the equalizing circuit,and when the number of cells in the battery pack increases,the voltage level mismatch between the centralized charger and the battery pack will be caused.By configuring a charger for each battery unit,the distributed charging system can not only solve the problem of voltage mismatch,but also effectively realize balanced charging of battery packs in series,but often fail to realize its discharge balancing function.In order to solve the above problems,a distributed charging system with balanced function is proposed.The system integrates the discharge equalization function into the distributed charging system by transforming the filter inductance of the distributed charger into coupling inductance and adding an appropriate amount of switching tube.Compared with the distributed charging system,the whole system can realize the balanced charging and discharging of the series battery pack only by adding a small amount of circuit cost,and also solve the voltage level mismatch problem caused by the increase of the number of cells in the battery pack.This paper analyzes in detail the basic working principle of the distributed charging circuit with equalization function and the interaction between the two basic working modes of the circuit.Under the condition of critical continuous current,for the common device coupling inductance of charge equilibrium mode and discharge equilibrium mode,the effects of the original side inductance,peak current,coupling coefficient,turn ratio,battery voltage and circuit resistance on the equalization current and the equalization efficiency are studied.On this basis,the optimal design method of coupled inductance is presented.An equalization strategy based on load current and equalization cut-off capacity is proposed for discharge equalization.According to the load current,this strategy can accurately calculate the balancing current and the time required for each unbalanced unit to reach the cut-off capacity at the same time,and achieve a better balancing effect even under the condition of changing load current.The influence of the value range of equalization cut-off capacity on equalization velocity and equalization current is studied.The equalization capability under discharge equalization condition is studied and extended to the series cases of different capacity batteries.Taking three 100 Ah series lead-acid batteries as an example,the simulation experiment of series battery balanced charging is completed.The discharge equalization simulation and experimental verification are completed by using the developed discharge equalization strategy,which verifies the feasibility of the system's charge-discharge equalization function and the correctness of relevant theoretical analysis.