順滑控制應用於風能轉換系統之能量最佳化

Abstract

本論文主要是利用順滑模態控制來達到風能轉換系統之能量最佳化的目標，由於風力發電機的輸出功率會受風速的影響，因此要得到最大轉換效能，必須使風力發電機操作在最大功率點，以提高發電效率。此最大功率點是透過追蹤最佳翼端速度比，以取得相對應之最佳轉速值，做為發電機實際轉速之比較，再將兩者之誤差當作控制器調整之參考。設計順滑模態控制時，首先選定穩定之順滑模態，並使系統達到控制目的，其次設計控制法則讓系統軌跡得以在有限時間內進入順滑模態，並利用順滑層取代順滑平面，以避免高頻之切跳現象。此外，在控制法則之中的微分運算，本論文採用高通濾波器予以近似，以避免高頻雜訊。最後，利用MATLAB/SIMULINK之數值模擬，來驗證在不同風速下順滑模態控制的穩健性，以及估測器與控制法則中係數變動對控制準確度的影響，由所獲得的模擬結果，可知本論文所設計之順滑模態控制確能達到最佳化之風能轉換。

This thesis proposes a novel sliding-mode control for the wind energy conversion systems to reach the energy optimization. Since the output power of wind electrical generators tends to interact with wind speed, it is required to operate at the maximum power point so as to enhance the efficiency of wind electrical generators. By tracing the optimal tip speed ratio, the optimal output power and the optimal rotational speed are obtained. After comparing to such optimal speed, the bias of the generator rotational speed is determined and used as the reference to adjust the controller. To design the sliding-mode control, first choose a stable sliding-mode require for the control purpose. Then, construct the control algorithm to drive the system trajectory into the sliding mode in a finite time. As for the chattering phenomenon, it is eliminated by substituing the sliding surface with a sliding layer. In addition, a first-order high pass filter is employed to approximate the undersirable differential operation in the control rule, not to excite high frequence noise. Finially, the simulation of MATLAB/SIMULINK is adopted to demonstrate the robustness of the sliding-mode control at various speed, and the effects on the control accuracy caused by the use of different coefficients in the estimator and control rules. From the numeric results, the proposed sliding-mode control indeed completes the optimal wind energy conversion successfully.