| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩博士班 === 98 === The thesis focuses on design and implementation of a solar photovoltaic (PV) generation system. The system architecture is divided into a front-end boost converter and a back-end multilevel inverter. With source of PV modules, the front-end converter conducts maximal power point tracking (MPPT) control, as the back-end inverter feeds the DC power into the grid. Meanwhile, power factor correction (PFC) of the inverter output is employed to obtain near-unity power factor.
The front-end converter not only possesses the voltage doubling function as compared to the traditional Boost converter, but uses zero-voltage switching techniques to reduce the switching losses of main switch and turn off the diode at zero current. The overall system efficiency can thus be enhanced. In the proposed system, the output voltage of the back-end five-level inverter is obtained by switching the output voltages of the front-end converter. Once the output voltages of the front-end converter are not balanced, the five-level output voltage would be distorted. To avoid the disadvantages thus incurred, a self-balanced capacitive Boost converter is proposed to balance the voltages for the inverter input. Less harmonic contents in the inverter output can therefore be achieved.
To verify the effectiveness of the proposed system, with power rating of 600W, the system is practically tested for off-grid and on-grid operations. In the testing of off-grid operation, the total harmonic distortion (THD) of the proposed five-level full-bridge inverter output voltage is 2.67%, and the overall efficiency of the system is 87.2%. In the testing of on-grid operation, the power factor of the system output is 99.2%, and the THD is 5.7% due to higher THD of the grid voltage with the overall efficiency of 85.3%.
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