Research On Wide-range High-Conversion-Ratio Electric Power Conversion In More-Electric Aircraft System

The more-electrical aircraft technology is to use electric energy as much as possible to replace the secondary energy in the form of non-electrical energy on the aircraft,and is the development direction of modern aircraft.Power electronic converters,as the core power conversion components in the system of more-electrical aircraft,play a pivotal role in the power supply system of the aircraft.Therefore,it is of great theoretical significance and practical value to study power electronic converters applicable to more-electrical aircrafts.In the first chapter,an introduction of more-electrical aircraft and its electrical system is given.After that,the research status of traditional PWM AC-AC converters,high-convertion-ratio DC-DC buck converters and coupled-inductor technology used in high-convertion-ratio converters is summarized.In the second chapter,a single-phase trans-z-source AC-AC converter is proposed.Firstly,the topology is introduced.Secondly,a control strategy that can realize safe-commutation without loss snubber circuit is given and the principle of safe commutation is analyzed.Thirdly,the working principle and safe commutation principle is analyzed.Fourthly,the theoretical analysis of its equivalent circuit was carried out and expressions of voltage convertion ratio,voltage and current stress of the components are given.Fifthly,the converter is compared with the traditional impedance-source AC-AC converter in detail.Finally,its theoretical waveform was analyzed.The converter can either step-up or step-down,the output voltage can be either in-phase with the input voltage or inverted.The proposed converter can realize safe commutation without additional loss snubber circuit,which improves the efficiency,reduces the complexity of the structure and volume,improves the reliability of operation,and avoids the occurrence of waveform distortion.The coupled-inductor significantly increase the voltage conversion ratio,which can greatly improve the buck-boost capability by adjusting the turns ratio of the coupled-inductor.In addition,the input and output of the proposed converter share the same ground,the input current is continuous and has a lower total harmonic distortion.In the third chapter,a high-convertion-ratio soft-switching DC-DC buck converter based on coupled-inductor and switched-capacitor is proposed.Firstly,the topology and control strategy are introduced.Then the working principle are analyzed in and and the realization of the soft-switching are explained.After that,the equivalent circuit is analyzed and expressions of voltage convertion ratio,voltage and current stress of the circuit components are given,meanwhile the boundary conditions of magnetizing inductance are analyzed.Afterwards,the efficiency is calculated and the efficiency formula is given.Finally,the converter is compared with several traditional Buck converters.Coupled-inductor and switched-capacitors greatly increase the voltage conversion ratio,and the step-down capability can be increased by adjusting the turns ratio of the coupled inductor.The use of extreme duty cycle is avoided,thereby reducing switching losses and conduction 'losses,improving efficiency,and reducing current ripple.In addition,the converter can also achieve soft-switching,further reducing the switching losses and improving the efficiency.In the fourth chapter,the design of the experimental prototype system was completed,including main circuit design,drive circuit design,sampling circuit design,and magnetic element design.In the fifth chapter,the simulation and experiment is completed.A Saber simulation was performed and the simulation results were given.An experimental prototype system based on TMS320F28335 DSP was built,and the theoretical analysis and simulation results were verified experimentally.Finally,the efficiency test of the converter was completed.