Characterization of Supraharmonic Emission from Three Different Electric Vehicle Charging Infrastructures in Time and Frequency Domain

Abstract

With the recent proliferation of electric vehicles (EVs), maintaining power quality within acceptable limits in future distribution grids will become a challenging task. A specific concern is the spread of Supraharmonics in the range from 2 to 150 kHz, generated by modern power electronic devices. In this paper, the long term Supraharmonic distortion from three differently sized electric vehicle charging infrastructures is analyzed in frequency and time domain. At the monitored sites several interruptions of EV charging processes were observed due to poor power quality. It was found that vehicles disconnect when exposed to high levels of harmonic distortion. Moreover, the impact of the charging EVs on the Supraharmonic distortion and the interaction with the background distortion for the individual sites is discussed. Results show that a general increase in Supraharmonics emission can be expected due to the rising number of EVs. However, measurements also indicate that damping effects can occur for certain load configurations.

Harmonic and Supraharmonic Emissions of Plug-In Electric Vehicle Chargers

“…Such values of supraharmonic emissions are confirmed in [36], where the results of three parking lots are reported with low mean values (profiles of about 80 to 50 dBµA for 2 to 150 kHz) and a maximum profile (less than 5% probability) 20 dB above, with sporadic peaks for a few switching components above 0.1 Arms. Similarly, the spectra up to 50 kHz reported in [21] show a couple of vehicles with clear emissions at 10 kHz and 27 kHz with peaks in amplitude of about 0.1 and 1 A rms, but also two profiles of emissions that do not have clear peaks of the fundamental switching frequency, thus cleverly achieving a reduction of supraharmonic emissions, limited to 10 mA rms.…”

“…A particular case is mentioned in [59] with broadband emissions between 2 and 6 kHz, that are probably of the same kind as those observed in [37] and result from the main pulse of the PFC stage. This impulsive nature is confirmed by [36] providing high-pass filtered time-domain traces, rather than a frequencydomain analysis; in particular, its Figure 9c provides a waveform quite close to those analyzed in [37].…”

“…References in found articles were then added, until relevant hits happened to be already found. As observed in [36] (almost at the same time of this work), long-term datasets providing EV charging measurements extended to the harmonic and supraharmonic range are not yet available.…”

“…With the extensive use of PFC, low-frequency harmonic distortion problems have been largely mitigated, shifting distortion to higher frequency, as a byproduct of waveform manipulation to achieve PFC and mixing with the distortion of the DC-DC converter downstream for DC bus regulation. The impact of PFC on the AC grid materializes as typical pulse width modulation bands for active rectifier implementations, or oscillating pulses, named zero-crossing oscillations in [36]: such pulses have frequency occupation in approximately the 2-10 kHz range [37,38] and can cause excessive stress and interference in equipment and components, with consequential malfunction and damage [36].…”

Waveform and Spectral Characteristics of Supraharmonic Unsymmetrical Conducted EMI of Switched-Mode Power Supplies

“…An anti-aliasing low-pass filter R 1 C 1 , which was designed starting from a maximum frequency of 1 MHz (positioning its cutoff frequency one octave above at 2 MHz, which was very compatible with the said sampling frequency of 10 MHz) and exploiting the input capacitance of the DSO channel (found to be quite accurate and stable at 15 pF), thus resulting in a resistive value R 1 = 1.5 kΩ (negligible in terms of the voltage drop in series to the 1 MΩ input resistance of the DSO); • A high-pass filter C 2 R 2 that further attenuated the 50 Hz mains fundamental and its harmonics and designed around a resistive value large enough not to disturb the impedance matching and to remarkably influence the low-pass filter (set to 5 kΩ) and a resulting series capacitance C 2 with a negligible reactance over the desired frequency interval. The use of a high-pass filter is supported by the suggested increase of the decoupling factor in [26] and confirmed by [27] for similar measurements.…”