The Quantitative Control Strategy Research For Battery Equalization Circuits

Wind storage power generation system is currently widely used in new energy power generation system.Battery energy storage system can inhibit the fluctuation of grid voltage,maintain the balance of energy to ensure the safe and stable operation of the system.However,the battery pack is expensive,we should extend its life as much as possible.At the same time,in order to avoid the difference of battery capacity caused the battery is overcharge or over discharge,we should add the fast equalization circuit for the series battery.In this paper,lithium iron phosphate battery pack is taken as the object of study.A balanced topology is selected for this problem,and an equalization control strategy is proposed to meet the reliability and fastness.The main contents are as follows:Firstly,the paper describes in detail the charge and discharge principle and working parameters of lithium iron phosphate battery.Then,it describes the causes and hazards of the differences in battery packs.Further emphasizing the importance of balanced control of the battery,reducing its individual differences.In the next step,this paper analyzes the equilibrium topology of the present stage,and finally selects the improved Buck-boost type equalization circuit.The circuit is a non-dissipative topology,the application of inductance as a conductive medium.Through the control switch to achieve the transfer of energy between the battery and achieve the balance of battery energy.Because of the existing control method which matches the circuit can not control the equalizing current,the improved PI double closed loop parallel control strategy is introduced.The voltage control module is used to compare and analyze the SOC of the battery and select the equalization direction of the battery.The current control module sets the equalization speed requirement,and the maximum error of the actual current value and the specification value is taken as the input amount of PI.The output is a PWM signal that meets the speed requirements,which is used to drive the switch to turn on.In order to verify whether the control scheme is valid,on the one hand,the simulation platform is established with MATLAB,which proves its feasibility under the ideal condition.On the other hand,the hardware platform is built,which mainly includes the equalization circuit,the data acquisition circuit and the protection circuit.The experimental results further show that the control strategy can control the equilibrium direction accurately and control the equalization speed in the corresponding threshold range.Under the premise of safe operation,the battery is balanced with the maximum current as much as possible,to achieve the purpose of rapid balance of the series battery pack.