基于地基云图的云跟踪与太阳辐照度超短期预报方法研究

STUDY ON CLOUD TRACKING AND SOLAR IRRADIANCE ULTRA-SHORT-TERM FORECASTING BASED ON TSI IMAGES

太阳辐照度是影响光伏发电的最直接气象因素。云量对太阳辐照度有重要影响。全天空成像仪(total sky imager,TSI)可客观、自动地对其进行观测。基于甘肃省金昌地区TSI-880地基云图进行云跟踪预报与太阳辐照度预报方法研究。首先进行云识别与云量反演;计算云运动的速度矢量、使用平流输送法预报云图。使用最小二乘法拟合晴空太阳辐照度数据,建立金昌地区晴空太阳辐照度模型;基于观测范围内的云透射率和云量构建线性回归关系,根据回归系数和预报云量进行辐射预报。选择晴间多云的天气进行云量反演与太阳辐照度预报,晴间多云时的云量和云透射率呈显著的负相关关系,相关系数为-0.81(显著性水平α=0.01),可实现5 min太阳辐照度预报。研究结果表明,结合地基云图能够有效预报云移动变化造成的辐射跳变过程。

Global solar radiation is the key factor to PV power generation. Cloud fraction is of importance to global solar radiation. Total Sky Imager(TSI)can get cloud fraction objectively and automatically. Based on the TSI-880 images in Jinchang area of Gansu province in China,the study of the method on cloud tracking and global solar radiation forecast on the order of minutes has been carried out. The images were pre-processed for constructing Red-Blue Ratio database for clear sky,and the cloud detection was realized and the retrieved cloud fraction can be obtained. The cloud velocity vector was applied to forecast the future cloud map by using advection method. The clear sky global solar radiation model was established from observed data and theoretical method. The radiation was forecasted by constructing the linear regression relationship between the cloud transmissivity and the cloud fraction. The solar radiation forecast was carried out for different sky conditions. Under the condition of partly cloudy,the cloud fraction is significantly negative related with cloud transmissivity,the correlation coefficient is -0.81( α = 0.01). The result shows that the 5-minute-ahead forecast method for solar radiation in this paper is reliable to avoid the jump-like variation of solar radiation produced by cloud movement.