A Novel Method to Evaluate Irradiance in PV Field without Irradiance Sensors

In order to develop scientific research on the performance analysis and faults detection for monitoring status in photovoltaic (PV) array, an accurate and reliable irradiance evaluation are required. The mathematical expressions for irradiance evaluation at module level and array level are presented by the measured current and voltage of the PV module and PV array. The proposed method is verified with three typical weathers and a big dataset of one year. The results of module level show that the proposed method has performed good R2 errors of 0.9957 on a sunny day, 0.9978 on a cloudy day and 0.9898 on a day with low irradiance. The average percentage errors are 4.9%., 7.4% and 8.3% respectively. At the array level, the average error for one year is achieved by 6.51%., and 50% of average irradiance ranges are from 200 W/m2 to 600 W/m2 during the whole year. It is proved to be rarely affected by uncertainties from weather changes. The proposed method is suitable to calculate irradiance and obtain input energy of PV array in engineering application.