| Summary: | 碩士 === 清雲科技大學 === 電機工程系所 === 97 === This paper presents a digital single-stage power converter for photovoltaic energy conversion application. The presented power converter consists of a boost type resonant circuit from which both DC and AC outputs are provided. The DC output is used to charge batteries and the AC output is applied for lighting purpose. With the conditions of continuous conduction and inductive load, the switches in the boost resonant converter can be turned on with ZVS. The advantages of the proposed boost resonant converter include simple structure, multiple outputs, and high energy efficiency.
The system uses the PIC18F452 microcontroller as the core control unit. The maximum power point tracking control and battery charge-discharge controls are all implemented in the single unit. The system utilizes the duty cycle modulation in the day time to control the maximum power point tracking and battery charge, and the frequency modulation in the night time to control the battery discharge for lighting fluorescent lamps. All the control algorithms finished in the same microcontroller result in simple control mechanism and circuit cost reduction.
Apart from theoretical analysis, design and computer simulation, an experimental prototype converter with power output 90W is constructed. The performance of the system loaded with battery (12V/3Ah x 3 lead acid) and fluorescent lamps (T5/35W x 2) are measured. The experimental outcomes from different operation modes are found in good agreement with theoretical analysis and design. The energy efficiency of the converter when operating in charge mode is 86.63%, and operating in discharge mode is 90.26%.
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