Research On 10kw Digital Control Full-bridge Three-Level LLC Resonant Converter Of Variable Frequency

With the economic and social development,the improvement of people's living standards,as well as environmental pollution and excessive threat of renewable energy consumption,more and more attention to green energy conservation.High-power power supply in the field of high-speed rail cars,aerospace and electric vehicles and other fields more and more widely,however,the traditional high-power full-bridge converter there is a high voltage and high current stress switch,limiting its application in high-power applications.Therefore,it is of great practical significance and engineering value to study the research of soft switching technology in high power power supply.In this dissertation,the full-bridge three-level LLC resonant converter can solve the above problems,the main switch tube voltage stress is only half of the input voltage.Through the frequency control,full-bridge rectifier circuit diode voltage stress is equal to the output voltage.Zero voltage switch(ZVS)capable of realizing the main switch in the full load range.Zero current switch(ZCS)of the output rectifier diode can be realized when the converter is below resonant frequency,The converter can meet the requirements of high efficiency and high power density.The main work of dissertation is as follows:Firstly,this dissertation briefly introduces the background and significance of this topic,introduces the characteristics of LLC resonant converter and the development of control strategy,and determines the variable frequency control strategy of full-bridge three-level LLC resonant converter.Secondly,the working principle of the full-bridge three-level LLC resonant converter under different chopping duty ratio in the frequency conversion control strategy is analyzed,and the chopping duty ratio and the converter gain are obtained according to its working principle Relationship.In the determination of the chopping duty cycle,the relationship between the gain and the frequency of the three-level converter under different loads is obtained by using the fundamental analysis method.At the same time,the conditions of the soft switch of the converter and the working range are given.Then,the converter based on the relationship by chopping duty cycle and the inverter gain of gain versus frequency under different loads,the main circuit of the full-bridge three-level LLC resonant converter and the control circuit with TMS320F28-035 as the control core are designed,and prepared the relevant control procedures.Finally,a 10 kw full bridge three-level LLC resonant converter prototype was built,and the converter was tested at full load,half load and light load,the voltage and the efficiency of the switch were tested and the switch,the soft switch of the tube is compared with the theoretical value of the converter gain at different operating frequencies at full load.The results show the feasibility of applying the full-bridge three-level LLC resonant converter in variable frequency control.