An unsupervised method for estimating the global horizontal irradiance from photovoltaic power measurements

Abstract

The precise calculation of solar irradiance is pivotal for forecasting the electric power generated by PV plants. However, on-ground measurements are expensive and are generally not performed for small and medium-sized PV plants. Satellite-based services represent a valid alternative to on-site measurements, but their space-time resolution is limited. In this paper we present a method for estimating the global horizontal irradiance (GHI) from the power measurements of one or more photovoltaic (PV) systems located in the same neighborhood. The method is completely unsupervised and is based on a physical model of a PV plant. It can estimate the nominal power and orientation of multiple PV fields, using only the aggregated power signal from their PV power plant. Moreover, if more than one PV power plant is available, the different signals are reconciled using outliers detection and assessing shading patterns for each PV plant. Results from two case studies located in Switzerland are presented here. The performance of the proposed method at estimating GHI is compared with that of free and commercial satellite services. Our results show that the method presented here is generally better than satellite-based services, especially at high temporal resolutions.

Experimental Application of Methods to Compute Solar Irradiance and Cell Temperature of Photovoltaic Modules

“…In some applications, such as automotive ones, several solar measuring devices must be used simultaneously [4], increasing the cost problem. In the case of small-scale PV arrays, such as rooftop PV systems, the much higher costs of pyranometers leads to use of other devices for monitoring solar irradiance [5,6]. The solar irradiance that a crop receives is measured because it affects its biological processes and several measurement devices are necessary, thus, using cheap but reliable irradiance sensors decreases the cost of the experiment [7].…”

“…An iterative method allows the estimation of the global horizontal irradiance using Perez transposition models and power measurements; an nRMSE of 15.1% was obtained in the best case [29]; another iterative method coupling two combined algorithms has been also used [6]; it was underlined that such iterative approaches can have some convergence problems [30].…”

Solar irradiance estimations for modeling the variability of photovoltaic generation and assessing violations of grid constraints: A comparison between satellite and pyranometers measurements with load flow simulations

“…We model PV generation with the empirical model [18][19][20] that accounts for the temperature effect by scaling the value of the POA irradiance. Let b denote the index of the electrical nodes, t the time interval, I…”

Solar Irradiance Estimation Using Kalman Filter

“…The state of the art of irradiance estimation are satellitederived methods (Bright et al 2018;Miller et al 2018;Rosiek et al 2018;Wang et al 2019). However, these kinds of estimations have spatial and temporal limitations (Nespoli and Medici 2017;Scolari et al 2018) that do not allow real-time and local (on the surface of a single PV panel or set of panels) estimates, needed to better management of solar power plants. In addition, the accuracy of satellite-based methods depends on the availability of satellites, which is uneven in both quantitative and qualitative terms around the world (Scolari et al 2018).…”