Three Level Push Pull Forward Converter

The deficient of global energy is getting more and more serious. As a superpower, The energy problem in China is the top priority. The development and utilization of new energy has been imminent. Photovoltaic cell is a new and reliable energy. The central government of China has determined the photovoltaic industry to strategic emerging industries, it’s the sunrise industry of the new century. The distributed generation system has becoming more and more widely used in photovoltaic cells. It has the characteristics of no pollution, high performance, flexibility etc.Because the output of photovoltaic cells is a DC power supply, so the output characteristics is soft. The power supply system usually use the cascade organization of DC/DC and DC/AC. The function of DC/DC converter is boost the voltage of low voltage and wide range to a certain value and voltage regulator. From here we see that it’s very important to design a reasonable DC DC converter.This paper first introduces the development of the power supply system of photovoltaic cells, then enumerates some DC/DC converters that have already been used. Analysis their advantages and disadvantages. Combined with the characteristics of PV cell output, at last choose to use the three level push-pull forward converter as a power system DC/DC converter. The converter has the advantages including low voltage stress on the switches, low voltage stress on the rectifier diodes, small size of filter. This paper also analyzes the characteristics and working principle of three level push-pull forward converter, designs a 300 W principle prototype, calculates the losses of the the main circuit and gives some proposals to improve the efficiency. This paper also compares the work principle and characteristics of two level DC converter and the three level DC converter. By combining with the practical application analysis and comparison of results, we selected three level DC converter as the research object. At last, uses saber to simulate and gives the simulation waveforms of the expected of the three level push-pull 300 W power forward DC converter. The correctness of theoretical analysis were verified.