Research On The Key Techniques Of High-Frequency Buck Power Electronic Converters

For the consideration of the serious environmental problem,the renewable source generation and the electric vehicle(EV)technologies encounter an unprecedented developing opportunity.Aiming at satisfying the requirements for advanced power electronic devices of high efficiency,small size and light weight,this paper focuses on the distributed renewable source generation and EV applications.Accordingly,the researches on novel topologies,application of new semi-conductor switches and control methods are conducted in this paper.In particular,key issues of several Buck-structurebased high frequency converters are discussed and analyzed in detail,and the main works are summarized as followings:(1)A grid-tie high-frequency dual-buck inverter for renewable source generation is proposed in order to meet the demand of miniaturization and light weight.The adoption of the SiC power devices contributes to the high-frequency operation as well as the high-efficiency conversion.In order to address the accuracy fading of the traditional loss calculation issue under the high-frequency situation,a systematic lossestimation approach for the high-frequency inverters is presented,which has been proved to be more precise for the high frequency loss calculation through contrastive experiments.(2)A parallel structure algorithm is proposed for the purpose of mitigating the limited calculation capability under the background of high-frequency inverting.The algorithm is implemented based on a dual-core microcontroller unit(MCU).A 400 kHz high-frequency one-cycle digital control is achieved.In the end of this section,the high frequency inverter successfully accomplishs the design objectives of high efficiency,small size and light weight.(3)A novel zero current switching(ZCS)Buck converter for the electric-excitation synchronous motor is proposed.Through the quasi-resonant procedure between the coupled inductor and the capacitor,the pulses of the excitation current,caused by the charge and discharge of the parasite capacitor during the high-frequency process,are eliminated.This converter meets the design goals of high-frequency,small-size and high-efficiency operation eventually through the promotion of the operating frequency,since the ZCS is realized and the equivalent series-connected rotor inductor is taken utilization.(4)Furthermore,a three-phase interleaved multi-resonant ZCS Buck topology is proposed in order to solve the existing problems of the current EV on-board charger(OBC),including low charge rate,restricted conversion efficiency and large volume.Through the multi-resonant architecture,the OBC converter not only attains the power factor correction(PFC)and improves the PF of the input current,but confines the total harmonic distortion(THD)of the input current as well.Besides,the soft-switching characteristics are also achieved by the multi-resonance so that the IGBT switches are able to operate under high frequency of 40 kHz.As a result,this OBC converter also harvests the required miniaturization and light weight.