由於風力渦輪發電機存在著非線性的特性,其最大功率點運轉位置將隨著風力狀況的改變而有所不同。為了使風力發電系統在任何風速下皆可操作在最大功率點,本論文提出比較斜率法與功率差量乘積法兩種最大功率追蹤控制理論應用於風力發電系統。 本文先建立各不同風速下風力發電系統之負載特性曲線模型,便於設計控制程式與探討所提最大功率追蹤之可行性。除實作完成傳統電流型擾動觀察法與三點權位比較法外,並與本文所提比較斜率法及功率差量乘積法相互比較。系統實作上應用最大功率追蹤技術搭配數位信號處理器(TMS320C240)調整升降壓式轉換器之責任週期,使風力渦輪發電機運轉在最大功率輸出。 為比較驗證上述四種控制方法,本論文以一部三相、12極、100瓦的風力渦輪發電機作為實際測試對象。風力渦輪發電機包括三片直徑1.17公尺之小型風力渦輪機與一台永磁式同步發電機。從實驗結果得知,本論文所提出之最大功率追蹤控制器,在不同的風速下,皆可準確地及有效地追蹤至系統之最大功率點,其中以功率差量乘積法具有最佳之追蹤效果與穩定性。
The wind-turbine generation system (WTGS) exhibits a nonlinear characteristic and thus its maximum power point varies with changing atmospheric conditions. In order to have the WTGS operate at maximum power points under different wind speeds, the thesis proposes two maximum-power-point-tracking (MPPT) control methods of the slope-comparing (SC) and the power-difference-product (PDP) algorithms to be used in the WTGS. In the thesis, load models of the WTGS under different wind speeds are first built up for design of control rules and feasibility studies of the proposed MPPT methods. Based on the traditional current-type perturbation & observation (P&O) as well as the three-point-weighting comparison (TPWC) algorithms, comparisons are made for the proposed SC and PDP methods. In the practical system implementations, the MPPT methods are integrated in the TMS320C240 digital signal processor (DSP) to adjust the duty ratios of the buck-boost converter to control the WTGS working with maximum power output. To compare and verify the effectiveness of the four MPPT control methods mentioned above, a practical WTGS has been used. The WTGS includes a small wind turbine with three 1.17m diameter blades and a three-phase, 12-pole, 100W, small permanent-magnet synchronous generator. The experimental results show that the proposed PDP controller achieves the best performance in terms of maximum power tracking capabilities among the four MPPT algorithms, though all the four MPPT algorithms can reach maximum power points in different wind-speed conditions.