| Recently there is a high demand for better power quality. Regulations such as IEC 555-2 and IEC61000-3-2 have been carried out to encourage companies to use or develop "clean" power appliances. It is estimated three phase power fact corrector (PFC) will be widely used in the next generation of distributed power system. Most three phase PFCs are based on Boost converter, so the output voltage should be high in order to minimize the harmonics in the input current. Therefore a DC-DC converter which can handle high input voltage is needed. Put the two double forward converters in series and a three level DC-DC converter is formed. It inherits the merit of no shoot-through from the double forward converter, besides the voltage on the input capacitors can be self-balanced.In the thesis, first a converter of two double forward converters paralleling at the input is discussed. The principle of circulating current between the primary windings of high frequency transformer is analyzed and the way to restrain it is introduced. Secondly, a three level Zero-Voltage-Switching (ZVS) DC-DC converter based on double forward converter is put forward. The principle and parameter selection is discussed and verified on a 3.2kW/220V prototype. Another 2.5kW/48V prototype is also built on which the comparison between SiC schottky diode and Si PiN diode and the effect on the overall efficiency are made. |
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