光伏系统中地基云图的预处理

用于地面天空监测和辐射预测的地基云图,由于其拍摄仪器全天空成像仪(TSI)自身的缺陷,使得拍摄的天空图像中存在较大面积的遮挡和一定程度的畸变,从而导致基于地基云图的云识别、分类和辐射预测等不准确。针对该问题,提出了一种镜像渐变修复方法来还原真实天空云分布情况。首先通过计算太阳在图像中的位置,自动确定遮挡区域;然后根据云的颜色特性,采用镜像渐变算法进行修复;接着,对太阳周围的白色像素点,根据太阳辐射衰减程度将其分割为云或晴空,并对识别为晴空的过度曝光像素点进行修正。实验表明,所提出的预处理方法可快速还原真实天空的云分布信息,且修复效果优于现有光伏系统上使用的方法,为后续气象变化研究和辐射预测等提供了条件。

Pre-processing of Ground-based Cloud Images in Photovoltaic System

Due to the disadvantages of the total sky imager(TSI), there are a large area of occlusions and a certain extent of distortion in the ground-based cloud image applied into monitoring the sky conditions and predicting solar radiation, which would result in the inaccuracy of cloud detection, cloud classification and solar radiation forecast based on ground-based cloud image. Therefore, a mirror gradients algorithm is proposed to restore the distribution of cloud in the image. The position of the sun in the image is firstly calculated to mark the occlusions automatically. Then the ground-based cloud image is filled and inpainted with mirror gradients algorithm based on the color feature of cloud. Next, the white pixels around the sun are classified into cloud or cloudless sky according to the attenuation of solar radiation, and the grey values of the over-exposure cloudless pixels are adjusted. The experiment results show that the proposed pre-processing method could restore the cloud distribution condition of the sky quickly and it is better than some other published methods used in photovoltaic system. It gives the strong support for the following research such as the change of climate and solar irradiance forecast.