| Photovoltaic generation industry develops rapidly in modern times. Solar energy is transformed into electricity by photovoltaic arrays. nevertheless, the electricity can only be utilized with a high efficiency by being converted and connected into power grid. In the conversion system, DC-DC converter and inverter are the two vital modules. DC-DC converter is for the match between DC voltage output of photovoltaic and DC voltage input of inverter; the inverter is for DC to AC transform, the output of which is connected to the power grid. The performance of the whole conversion system is the most important factor for economical electricity transmission. DC-DC converter of the conversion system is the link between photovoltaic arrays and inverter, and therefore its performance is the key factor for conversion system.In the DC-DC converter, switching devices would dissipates energy during the switching procedure, which lowers the power transmission efficiency and generates more heat to shorten the lifetime of the system. To reduce the energy dissipation caused by the switch devices, various soft-switch technologies are developed. Using the ZVT soft-switch technology can reduce the switching loss of the power electronic devices in high power conversion system significantly, and the energy efficiency can be promoted.In this thesis, Si C power MOSFET and Si C Schottky diode were applied in the converter,which yielded significant advantages. Firstly, the conduction loss of power device can be reduced under big current; secondly, because Si C devices have small thermal loss, rapid heat dissipation and high temperature tolerance, the heatsink volume of power device was decreased and the power density is increased.The main work in this thesis includes the followings. Si C based high power ZVT PWM Boost converter was designed on the basis of the theoretical analysis of Si C power MOSFET. The structure of main circuit was effectively improved, circuit elements were selected and the elements' parameters were optimized. The driven circuit module was designed corresponding to main circuit structure and its application request. The function of circuit was realized through computer simulation on designed main circuit and driven circuit by the simulation software Cadence Or CAD. The efficiency performance of both SiC power device based converter and Si power device based converter were analyzed by computer simulation method, indicating the efficiency of Si C power device based converter was 98.15% under the converter power of 2k W and load current of 4.7A, which is 3.15% higher than the efficiency of Si power device based converter. In order to reduce the overshoot voltage, a compact efficient soft start control circuit was validated in the control daughter board, which led to zero overshoot voltage and a short start time of 15 ms under high voltage high step-up ratio ranging from 100 V to 400 V, and therefore the safety of high voltage equipment was improved. Moreover, the heatsink volume of Si C power device based converter was reduced to only 1/5 of that of Si power device based converter,which is contributed to converter volume reduction and the power density promotion. The prototype was fabricated and the control circuit board function was tested. The measured control signal of prototype is stable and functional correct, which verified the simulation results and proved the feasibility of the design,in addition,subject to experiment equipments' condition,the convert effeciency of the converter was examined under the converter power of 2k W and load current of 4.7A,the experiment results showed that the convert effeciency reached up to 97.4%,greatly invreased compared to that of Si based power device,it is confirmed that the advantages of Si C based power device in enhanceing the convert effeciency of converter. |
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