Impact of Solar Intensity on Photovoltaic-Generated Current Harmonics and Transformer Life: A Mathematical Model With Experimental Validation

Abstract

Abstract With the rising penetration of photovoltaic (PV) plants on low voltage distribution systems, the generation of current harmonics as well as its impact on transformer operation is a current concern. The present research work develops a mathematical relationship of solar intensity (I(t)) with PV-inverter-generated total harmonic distortion of current (THDi,inv.), and then uses IEEE recommendations to present the impact of THDi,inv. on the life of a three-phase distribution transformer (TPDT). The validation of the presented model is done by real-time data monitoring from a 100-kWp solar roof-top photovoltaic (SRTPV) system, integrated with an 11-kV grid supply through a 63-kVA TPDT in the composite environment of north India. According to the results, decreasing I(t) values from 857 W/m2 to 35 W/m2 raise THDi,inv. from 3.57% to 63.43%. It is also observed that the production of poor THDi,inv. is high in the winter season (daily average = 27.44%) in comparison to their values in the summer season (daily average = 15.21%). For I(t) values less than 315 W/m2, the generation of large THDi,inv. (above 15%) takes place and it increases the loss of life of TPDT by a factor of 6.0.