Research On Topology And Control Strategy Of Current-Fed DC Electric Spring

With the depletion of fossil energy and the increasingly serious environmental problems,new energy vehicles have developed rapidly in recent years because of their renewable and clean energy,and relevant technologies have also been widely studied by scholars in relevant industries.Among them,the DC / DC converter in new energy vehicles puts forward corresponding requirements for its own performance due to the particularity of its working environment.For this application scenario,this paper proposes a current-fed DC electric spring(CF-DCES)topology that can be applied to the above scenarios.CF-DCES divides the loads in the system into two categories: one is the critical load(CL)that can only withstand small voltage fluctuations;The other is non critical load(NCL)that can withstand large voltage fluctuations.CF-DCES transfers the power fluctuation on the input side to NCL to ensure the stability of CL power,and when the power fluctuation is large,the battery will bear the corresponding part of the power fluctuation,so as to maintain the power supply reliability of the system.This paper studies the topology and control method of CF-DCES.CF-DCES topology consists of three port converter(TPC),bidirectional Buck-Boost converter(BBC)and battery pack.Based on this topology,this paper first gives its basic equivalent circuit model;Then,the modal analysis of the current-fed three port converter with inductor on the input side is carried out,and the corresponding small signal model is solved;Finally,the mathematical model of bidirectional Buck-Boost circuit is analyzed and deduced.Based on the above,two different control strategies of CF-DCES are proposed,the correctness of the control strategy is verified by simulation,and the advantages and disadvantages of the two control strategies are compared.At the same time,for the bidirectional Buck-Boost circuit,the current voltage double closedloop control is adopted,and the correctness and feasibility of the proposed strategy are verified by simulation,so that the circuit works in the constant current Boost state.Based on the battery energy storage structure in CF-DCES,an energy management system(EMS)applied to CF-DCES topology is proposed.The system changes the charge and discharge state of the battery in the bidirectional Buck-Boost circuit through the detection of CL voltage level and battery state of charge(SOC),so as to make the CF-DCES device operate safely and reliably.Finally,the hardware experimental device of CF-DCES is designed and built.Firstly,the design flow of the corresponding hardware system,such as three port transformer and control circuit,is introduced in detail.Then it introduces the software system design,such as the overall software flow and the design principle of the software under the corresponding module.Finally,the correctness and effectiveness of the proposed CFDCES topology and control strategy are verified by experiments.