Establishment And Research Of Photovoltaic Power Engineering Forecasting Model

The core component of photovoltaic(PV) system is the solar cell. PV power will be influenced by the external conditions, including ambient temperature, solar radiation intensity, object occlusion and other factors.The fluctuation of PV power threatens the security of grid and increases the difficulty of debugging of PV power station. Therefore, the study on prediction of the PV power generation has important significance. In this paper, the author researches the engineering mathematical model of PV cells, PV power forecasting model and physical model under partial shading.Firstly, this paper analyzes absolute error and root-mean-square error between single-diode equation and eight kinds of engineering mathematical models of the PV cells based on literature data. The results show the eight engineering mathematical models can accurately reproduce performance of the PV cells. However, the absolute error value increases with the bias voltage. Although eight kinds of engineering mathematical model can’t apllied to all kinds of PV cells under the same precision, the model error of polynomial form under padé approximation is minimum.Secondly, based on three assumptions that the photocurrent is much larger than the diode reverse saturation current, shunt resistance is infinite and diode reverse saturation current is independent of light intensity, the paper proposes two kinds of forecast model of PV power. According to the short circuit current, open circuit voltage, maximum power point current and voltage values and the temperature coefficient of the short circuit current, open circuit voltage, the maximum power point current and voltage, the first performance prediction model of PV module under different operating conditions is proposed and a simulation system is built by using Matlab/Simulink programs. Through the comparison between computer simulations and experimental data, it shows that the proposed model can accurately predicts the PV modules output characteristics at different light intensities and temperatures, and the relative prediction error precisions are all below 6%.The second forecast model of PV power is proposed by using cell’s short circuit current, open circuit voltage and maximum power point current and voltage under two different temperatures. Through comparison between prediction results and experimental data of mono(poly) crystalline silicon cell and PV modules, it is found that the crystalline silicon cell’s mean absolute error(MAE) of current-voltage globally fitting are less than 0.0018 A. And PV modules’ MAE of current-voltage globally fitting are less than 0.3017 A. As a result, the model can correctly predict the output characteristics of PV cell and meets the need of engineering forecast precision.Thirdly, the model of PV modules is is proposed under non-uniform insolation and a simulation system is built by using Matlab/Simulink programs. In this paper, the performance parameters of the solar cell are studied under the same area shadowed conditions, different shadowed locations and shapes by experiment. The study of PV power forecasting model under partial occlusion is of great significance.