Harmonic Modeling of Electric Vehicle Chargers in Frequency Domain

Abstract

Fully electric cars will be increasingly used in the near future in many countries. They are commonly known as electric vehicles (EVs) and use power electronic-based rectifiers for charging their batteries, which may significantly impact power quality in LV and MV distribution grids. Of particular importance are harmonic emissions of EV chargers, which are strongly influenced by the distortion of the supply voltage. This paper presents the results of testing and analyzing harmonic current emission of eight different single-phase EV chargers, with respect to supply voltage distortion. The analysis is based on extensive measurements performed at a test stand, capable of accurately reproducing supply voltage waveforms with desired distortion. The harmonic model consists of a constant part and a part that depends on the level of harmonics in the supply voltage. In order to characterize each EV charger in a general model, some characteristic indices are introduced, which quantify the sensitivity and linearity of harmonic currents of EV chargers to harmonics present in the supply voltage. The paper presents and discusses results for each individual EV charger, as well as a comparison of them.