對於太陽能(PV)發電系統而言，如何藉由最大功率追蹤(MPPT)演算法獲得太陽能電池最大功率輸出與最佳性能是非常重要的。在文獻中已提出許多最大功率追蹤技術並加以實現。其中，擾動觀察法(P&O)是最常見的，因為它具備設計簡單且易於實現的優點。然而，擾動觀察法在控制步階大小上會有權衡的問題產生：較小的步階值在穩態時振盪損失較低，但暫態響應較慢；若步階值較大，則會使穩態振盪的情形加大，造成損失增加。
為解決此一問題，本文提出一種新型變動步階式擾動觀察法。本文所提系統使用升壓式轉換器作為功率級電路，並搭配Microchip公司所推出的數位訊號處理器dsPIC33FJ16GS502來實現。本文所提出之方法於開始追蹤時，使用一個較大且合理的步階值進行追蹤。當工作點越過最大功率點時，則會更改追蹤方向並將原步階乘上一個縮小倍率α (α<1)以降低步階大小。由於擾動觀察法的精神為工作點會持續在最大功率點附近擾動，因此步階大小會逐漸縮小至系統允許的最小值。模擬與實驗結果驗證了本文所提出方法之可行性。從實驗結果可知本文所提出之方法在穩態追蹤精確度部分可到達99.91 %，而追蹤時間與傳統的變動步階式擾動觀察法比較可減少9%。

For photovoltaic (PV) generation systems, the maximum power point tracking (MPPT) algorithm is very important in obtaining the maximal PV power and facilitating optimal PV cell performance. Numerous MPPT techniques have been proposed and implemented in the literatures. Among them, the perturbation and observation (P&O) method is the most common due to its simplicity and ease of implementation. However, P&O algorithms suffer a tradeoff in choosing the perturbation step size of the control variable: small values decrease the losses in steady state with slower transient response, while large values improve the dynamic behavior at the cost of higher oscillations in steady state.
In this thesis, a novel variable step-size P&O method is implemented to deal with this problem. A boost converter is used as the power stage and the MPPT controller is realized using digital signal controller dsPIC33FJ16GS502 from Microchip corp. Initially, the proposed method uses the maximum possible perturbation step. When the operating points (OP) passes the MPP, the proposed method reverses the tracking direction and multiplies the perturbation step by a constant α (α<1) to reduce the step size. Since the OP will continuously perturbs around the maximum power point (MPP), the perturbation step will gradually decrease to the minimum step allowed by the system. Simulation and experimental results are also provided to validate the effectiveness of the proposed method. From the experimental results, the MPPT accuracy of the proposed system is 99.91 %, and the tracking time can be improved by 9 % comparing to conventional variable step-size P&O method.

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