Research On High Voltage Input Large Current Ouput DC-DC Converter

With the development of power electronic technology and appearance of new high performance,high voltage and high frequency power electronic devices, high voltage power supply begin to widelyused in military, industry, agriculture and medical treatment. This paper focuses on high input voltageand high power DC-DC conversions, gives the research on the input1600VDC and output40V/400Atwo-stage DC-DC converter with modular structure.In order to reduce the loss of long distance transmission line and make sure system worknormally, Firstly, the bus voltage of three-phase rectifier is properly designed in order to thelong-distance transmission and easy to choose power electronic device for the converter. Based on theresearch of the topology and control method used in high input voltage and high power DC-DCconversions, intermediate bus architecture is used in this paper. That is a isolation type anduncontrolled high voltage bus converter is applied in preceding stage, for electrical isolation andvoltage transformation. A closed-loop control PWM converter is used in backward stage, whichachieves limiting output voltage, output current and ouput power. Furthermore, the related issues offorced start of LLC resonant converter are analyzed and discussed. Invalidation analysis of powerMOSFET is also given. In order to prevent partial discrete device affected by temperature andslowdowns in performance, to ensure system safe and reliable work, considering the heat emissionproblem, internal mechanical structure is designed rationally.According to the output of the system characteristics, gives the requirements of limiting voltage,limiting current and limiting power and analyzes the problems of current-sharing which may becaused by regulator parallel mechanism, and solutions in detail. The performances of modes switchingis simulated by saber. On that basis, considering the non-linear of Power stage and PWM controller,Large Signal analysis method is used. A solution is provided in the paper to analyze the influence ofsystem in open-loop, closed-loop and load changes significantly by mathcad. Finally, a16kWprototype is developed. The experimental results verify the validity of the above theoretical analysis.