Nowcasting the Output Power of PV Systems

Unlike the power generated by traditional power plants based on fossil or nuclear fuels, the output power of the photovoltaic (PV) plants is highly variable to erratic. This is due to passing clouds which may cause a fast... [ view full abstract ]

Unlike the power generated by traditional power plants based on fossil or nuclear fuels, the output power of the photovoltaic (PV) plants is highly variable to erratic. This is due to passing clouds which may cause a fast variation of the solar irradiance, further inducing a massive shift in the output power of a PV plant. In this context, forecasting the power generated by PV plants becomes a critical task in the smart management of the grid. Accurate forecasts will enable the computers to take control actions aiming to balance the power grid in real-time. Since there are circumstances when the fluctuations of the solar irradiance are on a time scale of minutes or less, nowcasting the output power of PV plants becomes a timely research area.

This paper presents an innovative procedure for nowcasting the output power of a PV plant. The procedure involves two interrelated issues: (1) realistic modeling of the PV converter response and (2) forecasting the solar resource availability. The basic concept of the proposed procedure is based on several innovative results obtained by our team: (1) a new procedure of solving the five-parameter model of a solar cell (Mares et al. Energ Convers Manage 105 (2015) 139); (2) accurate modeling of the PV module operation in real environmental conditions (Paulescu et al. Energy 70 (2014) 49) and (3) the innovative two-state model for short-term forecasting solar irradiance (Paulescu et al. Energ Convers Manage 79 (2014) 690) based on sunshine number, a binary quantity stating whether the Sun is shining or not. The study was conducted with data recorded on the Solar Platform of the West University of Timisoara, Romania (http://solar.physics.uvt.ro/srms). The built database contains radiometric, meteorological and electrical data from an experimental PV setup, all measured simultaneously at high resolution (15 seconds).