Assessment of Harmonic Emissions from Small-Scale PV Inverters when Connected to a Distorted Supply

This paper presents the results of laboratory measurements of harmonic current emissions of several low voltage, small-scale, solar photovoltaic inverters when operating under non-distorted and distorted supply voltage conditions. For the distorted supply, measurements for the supply containing both typical low order harmonics and harmonics closely associated with ripple injection signals were obtained. Measurements were taken at half and full rated output of the inverters. Results show that the levels of current total harmonic distortion are low for non-distorted supply conditions but increase significantly for distorted supply conditions. Compliance assessment using the relevant emission standards were also undertaken. The outcomes of the analysis suggest there is a need to account for existing levels of harmonic distortion when modelling to establish harmonic voltage distortion due to emissions from solar photovoltaic inverters within low voltage distribution networks.