| With the increasing demand for energy in the world and the rapid development of new energy vehicle industry,more and more attention has been paid to the application and research of electrochemical energy storage system at home and abroad.Electrochemical energy storage system has become an indispensable part of modern power system,among which lithium battery energy storage system is the most promising research hotspot.In this paper,the bi-directional DC/DC converter in lithium battery energy storage system is the main research object.The specific work includes the following aspects:First of all,considering the battery cost and the group structure will limit the large-scale application of battery energy storage systems,with the introduction of national standards such as vehicle power battery recycling,this article selects a stepped lithium battery as the basic energy storage unit of the system.The factors that affect the battery pack performance are analyzed,and the battery pack structure of "single parallel pack in series and output in series through converter" is designed for it.Through the simulation of SOC(state of charge)equalization of multiple battery modules,the advantages of this battery group structure in solving the differences of battery consistency are verified.Secondly,in the research process of the energy storage lithium battery charge and discharge module,in order to improve the capacity of the power electronic converter and improve its output characteristics,this paper improves on the basis of the synchronous bidirectional Buck-Boost DC converter and proposes a Phase shift control multiple bi-directional Buck-Boost DC converter.In this converter,six synchronous bi-directional buck boost circuits are connected in staggered parallel with PWM(pulse width modulation)and phase-shift control,so that the output current is the superposition of six currents.Because the current pulsation of each circuit is cancelled each other,the total output current ripple is reduced.In order to realize the parallel current sharing and stable output of each circuit,the converter adopts the double closed-loop control strategy of voltage and current,uses the current feedback of each heavy inductance as the current inner loop and the total output voltage feedback as the voltage outer loop,so that the system can obtain better dynamic response.Finally,the H18650CIL-2.4 Ah stepped lithium battery of Shenzhen BAK was selected as the experimental object,and the experimental prototype of the bidirectional Buck-Boost DC converter based on the TMS320F28335 DSP chip control circuit was built.The results of simulation and experiment show that: Compared with singlesynchronous bidirectional Buck-Boost DC converter,multiple bidirectional Buck-Boost DC converter can effectively reduce output current ripple,reduce device loss,improve circuit transmission efficiency,help reduce device size and improve space utilization of energy storage modules. |
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