Battery Charger with Parallel-Loaded Resonant Converterfor Photovoltaic Arrays
| Autor: | Jia-Wei Yang, 楊嘉瑋 |
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| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Because of the issue of environmental protection resumes and the price of petroleum rises crazily, the attempt to seek for alternative energy source is a goal that would take universal efforts throughout the world. Among them, the solar energy is abundant, continuous supplying and pollution-free, hence, gathers many attentions on its research. As for Taiwan, located in subtropical area, there is sufficient sunshine; lots of sunlight and long sunny days, solar energy should be the most prominent candidate for green energy. In order to reserve the electrical power transformed from solar energy, a battery charger with high performance, low switching losses, low cost and high efficiency should be designed. This paper proposes a battery charger with soft-switching parallel-loaded resonant converter which is characterized with simple structure, less component count, small volume, light weight, low cost, high efficiency and high power density, etc. The high-frequency ac output produced by the parallel-loaded resonant converter should be rectified into a dc current to charge the battery. In order to remove the high-frequency ripples and to have a steady dc charging current, the rectified dc current should be fed into a low-pass filter which is designed based on the features of the circuit. The two active switches of the load resonant converter are controlled by pulse-width-modulation (PWM) controller. The converter is operated under continuous-conduction mode (CCM) by appropriate parameters design. Besides, the two power switches are turned on with the satisfactory features of zero voltage and zero current. Therefore, high efficiency can be achieved. The circuit parameters are decided according to the intrinsic impedance of the resonant tank. As the duty ratios of the active switches are fixed, the charging current should be programmed via tuning the circuit operation frequency and therefore the circuit impedance. The optimum operating point is sieved by the frequency response diagram to operate the charger at high efficiency. In addition, an over-voltage detector is equipped in series with the battery to keep the battery from being over-charged in order to prolong its cycle life. According to the switching operation and the configuration of the filter circuit, the operation modes and characteristic equations of the circuit are established and analyzed. To simplify the circuit analysis, fundamental wave approximation and the simplified equivalent circuit of battery are applied to build the equivalent circuit of the battery charger. According to this equivalent circuit, the circuit parameter design equation and design procedure are deduced. Via computer simulation and completed circuit experiments, satisfactory results are received. Efficiency of this novel battery charger with parallel-loaded resonant converter for photovoltaic arrays is up to more than 80%. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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