FIVE YEARS OF UTILITY SCALE PV POWER PLANT MONITORING MODULE DEGRADATION – WHERE HAVE MY WATTS GONE?

摘要

To minimize yield losses, utility scale PV powerplants are usually equipped with string monitoring systems.These allow fi ne control of the plant’s correct operation andmonitoring of its availability. While the identifi cation of total string failures is easy, detecting the cumulative effect of smallperformance variations or degradation at a string or substringlevel turns out to be challenging. A method for calculating themodule degradation is proposed. It is based on high accurate string current and voltage measurements, together with stringpower simulations under measured weather conditions, andtakes into account the aging of the irradiance sensor. Thismethod distinguishes between persistent degradation and temporary effects of shading or other aberrations, so that thefi nal results can be compared with the module manufacturer’spower warranty statement, or used to determine the plant’speak power or to predict its energy yield more accurately.