Research On Bi-directional Modular Power Supply Based On Current-Fed Half-Bridge DC-DC Converter

Battery is widely used for energy storage because of its high power density and low price.The power converters are usually used to achieve the charging or discharging control of batteries.A high efficiency and high power density bidirectional dc-dc modular power supply which is suitable for this occasion is studied in this thesis.Firstly,the circuit topology,working principle and transmission power relationship of the bidirectional DC-DC converter based on current-fed half-bridge are analyzed in detail.A control strategy that can realize the current of battery and the output voltage in variableness control is proposed.A unified small signal model of the converter is established based on the state space method,and the closed-loop control parameter design method is studied.Then,in view of that design goal of high efficiency and high power density modular power supply,the key technologies of the bi-directional DC-DC converter based on current-fed half-bridge are studied.To ensure the converter always working in soft switch state,the range of soft switching of power devices is investigated through theoretical calculation.After comparing the total current ripple in different coupling modes,the coupling strategy of coupled inductive has been selected,and the application of coupled inductors and planar transformers using planar cores have been discussed.In addition,the digital realization method of high frequency PWM signals is introduced.Whatmore,a soft-start strategy is introduced to stabilize the current impact.Finally,on the basis of theoretical analysis and research of the key technologies on the bidirectional DC-DC modular power supply based on current-fed half-bridge,a bi-directional dc-dc modular power supply prototype based on GaN transistors with 400 kHz switching frequency,24V/400 V voltage and 400 W was developed.After completing the parameters design,the simulation model was built in saber environment to verify the correctness of the design.The key exprienment waveforms under diffierent work conditions demonstrate the validity of the theroial analysis and prototype design.The corresponding results of the dynamic experiment verify the effectiveness of the control strategy.