以指向誤差修正技術應用在追日精度改進; Improvement of the Sun Tracking Accuracy With the Pointing-Error Correction Method

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题名:	以指向誤差修正技術應用在追日精度改進;Improvement of the Sun Tracking Accuracy With the Pointing-Error Correction Method
作者:	劉智維;Jhih-wei Liou
贡献者:	能源工程研究所
关键词:	追日偏差角度;追蹤器誤差;指向誤差模型;追日控制;聚光型太陽光發電系統;Concentration photovoltaic (CPV);Sun-tracking control;Pointing-error model;Tracker errors;Tracking offset-angle
日期:	2010-07-19
上传时间:	2010-12-08 13:40:34 (UTC+8)
出版者:	國立中央大學
摘要:	太陽追蹤器為聚光型太陽光發電系統中不可或缺的部件，其可使架設於上的聚光模組正對太陽，讓陽光聚焦於太陽電池上發電，當聚光模組集光率越高，追日精度也必須隨之提升，否則將因追日偏差造成系統發電功率遽降。通常追日偏差角要求小於0.5o。本文以開迴路追日方法為基礎，開發一指向誤差修正方法調整追日指令，在不需光感應器與手動校正追蹤器的情況下，可維持追蹤器的高精度指向。研究方法為先以MATLAB建立追蹤器誤差模擬程式，模擬追蹤器在不同形式的誤差時的追蹤偏差情形；隨後參考原應用於天文望遠鏡校正的指向誤差模型，建立一適用追日的指向修正模型，模擬發現此誤差模型除了在夏季外其餘季節修正效果佳。故本文提出一新誤差模型，將原追蹤偏差參數做座標轉換，再進行擬合計算找出誤差模型係數（即是偏差角修正量）來修正追蹤指向，解決夏季時追蹤器指向修正不佳的問題。為驗證新誤差模型的功效，以實驗型雙軸太陽追蹤器進行指向修正實驗，追蹤器上安裝PSD儀器，量測追蹤器的追蹤偏差角特性。將處理後的PSD量測數據，輸入至新誤差模型程式分析，找出代表追蹤器誤差的誤差模型係數，再輸入至追蹤指向控制程式中進行指向修正。藉由此方法可將平均追日偏差角度由0.443°降至0.045°，系統的發電量因此提升36%。 The solar tracker is an indispensable component in concentration photovoltaic (CPV) system. It allows CPV module point precisely to the sun and generate electricity by focusing sunlight onto the solar cell. The higher concentration ratio of module, the more demand of tracking accuracy. Otherwise the output power of module would drop sharply due to tracking error. Usually, a value of 0.1-0.5o offset-angle is required. This study developed a pointing-error correction method based on the open loop sun-tracking. It can maintain high accuracy and stably tracks sun without light sensor and manual adjustment of tracker. To simulate the behavior of various tracking errors, this study develop a MATLAB program to emulate errors of the tracker. Next adopting the pointing-error model which was originally developed for pointing-correction in the astronomical telescope, a pointing-error correction model was developed for sun-tracking. Simulation showed that the pointing-error model perform well except in summer. Thus a new pointing-error model was developed in which parameters of the model were processed via coordinate transformations. Then the model was analyzed using the curve-fitting calculation to find the coefficients (which are offset-angle corrections) of the pointing-error model for tracking correction. This new model successfully solved poor-pointing of the tracker in summer. Validation of the new point model was performed on an experimental dual-axis solar tracker. A Position Sensitive Detector (PSD) was mounted on the tracker to measure the characteristics of tracking offset-angle. PSD measurements were processed and input into the new pointing-error model for analyzing and coefficients of the model were obtained from analyzing these PSD data. With this correction approach, the average tracking offset-angle was reduced from 0.443° to 0.045°, and the system power generation increases upto 36%.
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