風力發電機塔架之可靠度分析

Abstract

為提高能源密度來滿足用電需求，風力發電機有不斷朝大型化發展的趨勢，這不僅提高風力發電機之開發與維修成本，也影響其運轉壽命。本研究建構一風力發電機之塔架模型，透過風速與塔架負載關係式求得塔架負載情形後，利用有限元素分析軟體探討塔架結構受負載下之應力分佈情形，並比較各不同負載分量之影響程度。本論文特別針對澎湖地區風速歷史觀測資料進行統計分析，求得該地區之風速機率分佈函數，最後結合前述塔架負載分析結果以及風速機率分佈函數，對塔架結構進行疲勞分析，並導入量化可靠度概念，求得塔架之平均失效時間。研究結果發現，塔架之主要負載為風作用於葉片掃掠面上的氣動負載以及因風速分佈不均而產生的俯仰力矩，與其他風力機設計軟體負載結果比較後發現，利用風速與塔架負載關係式計算所得負載對塔架進行結構分析是保守、可行的估算方法。而澎湖地區風速分佈情形，包括逐時平均風速與逐時極大風速皆可以二參數韋伯機率分佈表示。最後，由疲勞分析結果可知，當塔架模型座落於澎湖地區風場中且承受反覆之風力負載時，其失效時間高於331,416週次的可能性高達99.8%，顯示此塔架結構座落澎湖地區風場中具有適當的疲勞耐久度，為一安全之設計。

To increase the energy density in order to meet the demand of electricity use, wind turbines have been developed toward large-scale designs. The gigantic size of wind turbine towers can generate more electricity, but it will also create higher cost of development and maintenance, and impact the operation life. The present research sets up a wind turbine tower model, and the loads of towers are calculated by its relation to wind speed. Finite element method is used to analyze the stress distribution of towers under the loads. Impacts from different loads are compared as well. The wind speed distribution is derived from data collected in Penghu, Taiwan using statistical method. Fatigue analysis of towers is then conducted with fatigue loads and wind speed distribution, and the mean time to failure (MTTF) of towers is calculated with quantitative reliability theory. The result shows that the main loads of towers are the wind force acting on the rotation area of wind turbine blades and the moment caused by non-uniformed wind speed. After comparing this research results with loads calculated by a wind turbine design software, it is concluded that it’s a feasible and conservative method to analyze wind turbine tower structure with the loads calculated by its relation to wind speed. In addition, it is shown that the average and maximum hourly wind speed in Penghu can both be fitted into Weibull distribution. In conclusion, the fatigue analysis shows that the probability is greater than 99.8% for the tower model’s failure time to be above 331,416 cycles, and it shows that the tower model in this research possesses appropriate fatigue durability and is considered a safe tower design for Penghu.