Development of Photovoltaic System using PWM Power Inverter

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The final purpose of our research is a development of a photovoltaic system which has a simple construction, high efficiency and low cost. In this research, we have been planning to clear up the following problems :1. Development of a buck-boost PWM power inverter with high efficiency.2. Establishment of the design method of the photovoltaic system using the high efficiency buck-boost PWM power inverter as an interface of the commercial line and solar cells.First term (1995) : First, to obtain a high efficiency PWM power inverter, we developed a pushpull type PWM power inverter which was constructing with only one switching element and realized soft switching by a switch snubber. As a result the efficiency was improved 5 to 15% compared with the push-pull PWM power inverter with a conventional RCD snubber.Next, we have linked the push-pull PWM power inverter to the utility line and performed experiments on power flow and soft switching characteristics. As a results, this system has a good quality about the transfer characteristics of the power to the load and utility line from the solar cells. However, the realization of the soft switching was difficult in order to be affected by the modulation factor of the inverter and the input voltage of the solar cells.Final term (1996) : We have studied again about the soft switching and developed it which was constructed by only one capacitor. We are developing the PWM power inverter with this soft switching method, now.Furthermore, we examined the relations between the efficiency and materials and winding method of a reactor of the PWM power inverter.Ferrite, amorphous and air core were used as the materials. As a result, the efficiency of the inverter was not much affect by the difference of materials.The PWM power inverter with a no isolation reactor using air core was the best efficiency of 95% than that using other materials.