| In the market,battery balancing often adopts passive balancing,and the energy utilization rate is low.In response to this problem,this paper designs a set of offline single cell active balancing equipment to improve the balancing speed and energy utilization,which is suitable for common electric vehicles lithium battery.The balancing equipment can perform constant current charge and discharge balancing on the single battery,and the balancing current can reach 10 A to improve the balancing speed.The current can be adjusted in real time during the equalization process to achieve a wide-range adjustment of the equalized current.This article first introduces the overall design of the equalization device.The equalization device consists of three parts: the touch screen,the main control board and the equalization module,and each part is designed separately.The key of the equalization equipment is the design of the equalization module,which is based on a bidirectional flyback converter and a microprocessor.The bidirectional flyback converter is the main circuit of the equalization module.In this paper,a detailed principle analysis of the RCD clamping and active clamping topology is carried out,and the bidirectional active clamp flyback converter is applied by the switching network averaging method.Modeling is performed to find each average DC component and small signal transfer function.Aiming at the two clamping methods of the bidirectional flyback converter,the parameter calculation of the main circuit and the device selection are completed respectively.On the other hand,the peripheral hardware control circuit is built with STM32 as the core,including voltage and current acquisition,PWM drive,overvoltage and overcurrent protection and CAN communication.Together with the hardware of the main circuit and the control circuit,a software program is designed to achieve closed-loop control of balanced current.In addition,the touch screen and main control board mainly realize display,communication,data calculation and storage functions.Type selection and configuration of the touch screen;hardware design and program design of the main control board.Finally,the lithium battery model under simulink is verified by charge and discharge simulation,the bidirectional RCD flyback converter and the bidirectional active clamped flyback converter circuit are built to perform charge and discharge simulation of the battery.Firstly,the open-loop simulation of the two clamp-mode flyback converters is performed,and the batteries are charged and discharged with different balanced currents respectively.The simulation waveform is observed to verify the correctness of the theoretical analysis and the design of the main circuit parameters.Then perform PI compensation on the small-signal model of the bidirectional active clamp flyback converter,and perform closed-loop simulation to observe the waveform and dynamic response waveform during steady-state operation during charging and discharging.Each operating point can work stably and the dynamic response is rapid To verify the correctness of the model analysis,the closed-loop control meets the requirements of the constant current charge and discharge of the lithium battery and the wide range of current adjustment in the balancing process. |
