Study on Ultra-short-time Power Forecast of Photovoltaic System based on Ground-based Cloud Image Recognition and Key Impact FactorsRunjie Shen, Yiying Wang, Ruimin Xing, Danqiong Hua and Ming MaE3S Web Conf., 185 (2020) 02028DOI: https://doi.org/10.1051/e3sconf/202018502028