| Summary: | 碩士 === 明新科技大學 === 電機工程研究所 === 101 === Photovoltaic (PV) power system becomes an important alternative due to its merits such as freely available, environment friendly, and less maintenance cost. Hence, the demand of PV power system has increased. Tracking of the maximum power point （MPP） is an important and essential function of most of the PV power system. Every maximum power point tracking (MPPT) technique has its own merits and demerits, but the perturbation and observation （P&O）method is widely used because of its low cost and easy implementation. The P&O method may fail to track the exact MPP when atmospheric conditions change rapidly or the P&O method is not correctly implemented. Many improved P&O methods have been published, but most of these published techniques focus on the adjustment of the perturbation magnitude. The discussions to the effect of sampling time are seldom to be found in the corresponding literatures.
Basically, the contributions of the thesis can be summarized as follows. First, a new voltage-boost dc-dc converter for PV power system is proposed, and the corresponding improved P&O method is also proposed to enhance the performance of MPPT when the solar cell module is locally operated on short circuit or open circuit. Secondly, to speed up the convergent time of the P&O method, an index is adopted to judge the steady-state operation mode. Third, a DSP-based PV power system prototype is constructed. And some experimental results are given to demonstrate the performance of the proposed improved P&O method. Finally, a LCL filter-tied grid connected PV system is simulated, and the simulated results can verify the validity.
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