Research On Battery Equalization Technology Based On Soft-switching Fly-Back Transformer

With the increasingly short of energy and serious pollution of the environment problems,energy conservation and emission reduction have become two major subjects for our future work,especially in terms of traffic and transportation field.New energy vehicles play an indispensable role in this process and become hot research topics in many countries.As the power source of electric vehicle,batteries must have inconsistencies inevitably,which will affect their service life and security.Battery active balancing technology can improve the service life cycle,efficiency and reliability of the battery by transferring the energy between batteries so as to reduce the differences between them.At present,there are many kinds of active balancing methods transformer-based battery equalization structure has been widely researched,because of its high balancing current and high efficiency.So this paper researches the balance of battery based on transformer.As this structure has the disadvantages of the switching loss and circuit loss,the LCD buffer circuit is added to realize the soft switching,so that reducing the switching loss.The mechanism of energy transfer is discussed with the control strategy,and the main research of this paper is listed as:First of all,on the baisis of traditional equalization topology with transformer,a new balancing topology based on a novel soft switching flyback transformer is proposed,inhibiting voltage spikes with LCD buffer circuit.Modal analysis of the equalization circuit is discussed,Quantitative capacitor voltage and inductive current in different LC resonant frequency,the energy release of fly-back transformer is studed in two cases of current continuous and discontinuous mode,step by step analysis of the equilibrium process is proposed.Second,the primary side equivalent circuit model of the main circuit in the time domain and frequency domain are given respectively in different working conditions,the calculation of energy transfer mechanism is given;the optimization of control strategy is put forward,SOC estimates is obtained directly through the battery management system,the equalization is realized by setting the equilibrium open and cut-off threshold and selective bubble method.Finally,the design of system hardware is given,the simulation model is established,the hardware parameters are designed,and the experimental platform is built to verify the theory analysis.The simulation and experiment results show that the switch tube on both ends of the voltage and current flow through the on off switch and conduction in an instant,from zero gradient,achieve soft switch technology.By comparing with the simulation and not with the simulation of charging data,the realization of the equilibrium effect is verified,and balanced efficiency can reach 89%.