Research On Layered Equalization Control Strategy Of Energy Storage Battery

The new energy power generation has intermittent and fluctuation,which has certain influence on the security and stability of power grid.The battery energy storage system can solve the problems brought by the new energy power generation,so it has high application value.At present,the rated voltage of the single cell is only a few volts,so,the batteries are connected in series to meet the requirement of the voltage level of the battery energy storage system.Because of the inconsistency of the battery pack,with the increase of charging and discharging times,the battery life and capacity will decrease rapidly.It is of great significance to improve the overall life of the battery pack and the utilization of the overall capacity.However,the storage battery system has a lot of batteries,so it is difficult to balance the energy storage battery with a simple equalization circuit.Therefore,the battery pack was divided into the top module and the bottom module,and then balanced the top module and the bottom module.A bottom module equalization circuit of the storage battery is designed based on the bidirectional Cuk converter,based on this circuit,a new equalization control strategy is proposed,and the uniform of the SOC(State of Charge)of the battery strings is used as the equalization goal in this strategy.The strategy uses the estimation of the average balanced SOC as a reference,and controls the switch states and the energy transfer direction of each equalizer,according to the energy distribution of the bottom battery module.With this strategy the unnecessary energy loss during energy transfer is reduced and the equalization speed is speeded up.The equalization control strategy effectively solves the problem of low energy transfer efficiency of the adjacent cells comparing equalization control strategy,as well as the slow equalization speed of the MAX/MIN value equalization control strategy.To solve the problem of low energy transfer efficiency in the long distance transmission of energy,a equalization control strategy based on bidirectional fly-back converter is proposed,and the uniform of the SOC of the battery strings is used as the equalization goal in this strategy.This equalization control strategy used the bidirectional fly-back converter equalization circuit as a top equalization module.And by transferred the lower energy module's energy to the battery pack,and the battery pack's energy to the lower energy module,combined with the bottom equalization control module,this equalization control strategy effectively improved the energy conversion efficiency.The simulation model is built with MATLAB,and the simulation analysis of the equalization control strategy of the bottom and the whole battery pack is carried out to verify the feasibility and effectiveness of the proposed equalization control strategy.