Research On Phase Shift Push-pull Bi-directional DC/DC Conversion Based On Magnetic Integration

Since the beginning of the 21 st century,with the development of new renewable clean energy,bidirectional converters are widely used in power management,aerospace,uninterruptible power supplies and new energy vehicles due to their advantages of energy bidirectional transmission through a single topology.in.However,as a kind of high-frequency switching power supply,the bidirectional converter has new requirements for the volume and efficiency of the converter,including high frequency,high efficiency and high power density,along with the development of technology and the demand for energy saving and environmental protection.In this regard,this thesis is optimized from the following aspects:(1)soft switching technology;(2)magnetic integration technology;(3)synchronous rectification technology.According to the above system requirements,this thesis firstly determines the research scheme,namely phase-shifted full-bridge/push-pull bidirectional converter,and analyzes the mechanism of the voltage spike problem inherent in the push-pull side of this converter,and respectively on the high-voltage side.The topology was modified with the low side to suppress voltage spikes.The suppression of voltage spikes increases the efficiency of the system,reduces the voltage stress on the switching transistor and makes it easier for the converter to implement soft switching.In this case,the bidirectional converter used in the buck mode often introduces a large-volume resonant inductor for the convenience of parameter design.To improve the power density of the system,a magnetic integration method is adopted to integrate the additional resonant inductor with the main transformer,which effectively improves the system.The converter power density also reduces the losses caused by the magnetic components.In order to reduce the leakage inductance of the main transformer,the rotator capacitance model is used to optimize the design of the winding structure.The effects of differ ent winding structures on the transformer winding are compared.The optimal winding structure is obtained by finite element simulation analysis.The magnetic loss caused by the skin effect and the proximity effect.In this thesis,there are many topological switching tubes and there are resonant modes.In order to obtain the small signal model of the converter,the small signal modeling method of the simplified circuit is adopted,and the circuit is equivalented by the converter in the step-up and step-down modes.Simplify and get its small signal model.According to the obtained transfer function and Bode diagram,a Type II compensation network is designed,and a peak current loop is added in the buck mode to effectively improve the dynamic characteristics of the system.In order to achieve full load range efficiency improvement,dynamic dead zone and synchronous rectification control strategies are adopted to further improve system efficiency and reduce electromagnetic interference caused by traditional rectification methods in the full load range.Finally,an experimental prototype with a rated output of 500 W was built.When the input voltage is 400 V and the operating frequency is 100 kHz,the output voltage is stable at 48 V,and the peak efficiency of the converter is 95.2%.The predetermined index is realized and the theoretical analysis is validated.