太陽能發電系統目前主要都以固定式為主，為了提升其發電效率，勢必要將太陽能模組隨時正對太陽來達到高功率輸出。追日系統主要分成主動式及被動式兩種追日方法，分別利用光感測器及太陽軌跡公式來進行追蹤，而都有其各自的優缺點。光感測器法雖然成本較低、安裝精度要求不高，但容易受環境及天氣影響追日效果；軌跡公式法雖不會受到天氣影響，但機構安裝誤差要小、定位必須精確，而機構長時間使用後會出現老化、變形，所以需要時常校準，造成成本較高。
　　本研究提出短路電流法，利用太陽能板本身的輸出電流當作追蹤訊號，經由dsPIC控制太陽能追蹤器，達到追日效果。此方法不受機構老化、變形及安裝誤差等影響，仍可找到最大輸出功率的位置，混合光感測器做初定位及粗調來增加追蹤精度。

　　The solar power systems are mainly fixed-based. In order to enhance the power generation efficiency, the PV module must be kept facing the sun directly at any time. The tracking systems are divided into two kinds of active and passive tracking methods, respectively, the use of photo-sensor and sun trajectory formula to track, and they also have advantages and disadvantages. The photo sensor although have lower cost and less set up precision, but easy to affect the tracking performance by environment and weather. The trajectory formula although doesn’t affect the tracking performance by weather, but the error of mechanism set up should be small and the orientation should be fixed accurately. The mechanism will be aging after using a long time, so the system should be calibrated and maintained usually, and resulting the higher cost.
　　This thesis proposes the short-circuit current method, it uses the output current of a solar cell as tracking signal, and through the dsPIC to control the sun tracker and achieve the effect of tracking. Thus, the error of mechanism set up and the orientation-fixing accuracy need not to be considered, and the tracking angle that the PV outputs maximum power will still be met. Mix the photo sensor to do the initial position and coarse adjustment to increase the tracking accuracy.

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