Harmonic and supraharmonic emission of on-board electric vehicle chargers

The number of fully electric cars is expected to increase significantly 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. These circuits may significantly impact power quality in LV and MV distribution grids, in particular the distortion at frequencies below 2 kHz (harmonics) and above 2 kHz up to 150 kHz (supraharmonics). While harmonic emission of EVs strongly depends on the supply voltage distortion, emission of supraharmonics at switching frequency and its multiples is mostly determined by the design of the EV's filter circuits. This paper presents the results of testing and analyzing the harmonic and supraharmonic current distortion of 19 different on-board EV chargers, representing a significant portion of EVs currently available on the German and European markets. The analysis is based on extensive measurements performed at a test stand that is capable of reproducing almost any supply voltage waveform with a desired distortion. The paper finishes with selected results from a field test with almost 100% EV penetration connected to a feeder in an urban LV grid.