太陽能是一種取之不盡，用之不竭的綠色能源，但是由於太陽能電池的功率輸出，會隨著日照強度、溫度、負載變化等各種外在因素而產生改變，並非能夠自行保持在最大功率輸出，因而會造成能量的損失，所以需要透過一些能夠追蹤最大功率輸出的控制法則，與配合適當的硬體電路，使太陽能電池能隨時因應各種外在環境的變化，而調整維持在最大功率輸出的狀態。
本論文提出一種基於負載電流控制與結合改良型滯環比較法之太陽能電池最大功率追蹤法則，以直流轉換器之輸出電流作為追蹤最大功率的控制依據，不需檢測電壓與計算功率，藉此簡化電路結構來降低成本，另經由改良傳統滯環比較法原有特性，加入自動調整擾動方向的功能來提高追蹤性能，以及利用時間控制來降低工作於最大功率點時的震盪損失，並以Matlab/simulink作為電腦模擬工具，分別對於太陽能電池與直流轉換器與最大功率追蹤進行各項模擬測試，觀察本文提出之最大功率追蹤法則及傳統滯環比較法與擾動觀察法，在固定日照和變化日照情況下之各種輸出特性，以及自動追蹤最大功率時之差異比較，最後再採用內建類比轉數位之轉換器與具有PWM訊號產生器功能之微控制器單晶片PIC18F4520實作最大功率追蹤之硬體電路，搭配小功率單晶2 W太陽能電池，與利用60 W鎢絲燈作為太陽光源，實驗在不同照度下之輸出情形，並確認能夠達到最大功率追蹤之效果。

Solar energy is an inexhaustible supply of green energy, but power output of the solar cell can not keep at the maximum power output due to various factors such as sunlight intensity, temperature and load changes, causing energy loss. It is necessary to track the maximum power output with the appropriate hardware circuit and software control techniques so that the solar cells can be responsible to external environment changes at any time, and adjusted to maintain maximum power outputthe state.
The thesis presents a maximum power point tracking method of solar cell based on combining load current control and improved hysteresis comparison technique to track the maximum power output. Without detecting voltage and calculating the power, we monitor the output current of DC/DC converter only to simplify the control circuitry and reduce costs. The traditional hysteresis comparison method was revised by adjusting the disturbance direction automatically to improve the tracking performance, meanwhile the time control aogorithm reduced the oscillation loss during working at the maximum power point. The commercial software of Matlab/simulink were used to simulate performances of solar cells, DC/DC converter and the maximum power point tracking technique, to test and compare the power output differences among proposed method and various conventional methods for fixed and variable sunlight. Finally, the microcontroller PIC18F4520, built-in A/D converter and PWM signal generator, was used to construct hardware circuitry, 2W single crystalline silicon solar cell and a 60W tungsten lamp as the sunlight, to simulate power output for different illuminance and verify the effectiveness of the maximum power point tracking proposed.

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