The impact of electric vehicles on the power quality in low-voltage grids

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Samenvatting

The increasing penetration of Battery or full Electric Vehicles (BEVs) in the Electricity Grid, has a significant impact on low-voltage distribution networks. On the one hand, BEVs have a significant impact on the distribution networks due to their high charging loads. The high power ratings compared to average household equipment will increase peak demand significantly, resulting in reduced reserve margins and possible overloading of grid assets. This can cause reliability problems and degraded performance of the power system.

On the other hand, BEVs have a significant impact on the Power Quality of the grid. BEVs use direct currents (DC) to charge their batteries, needing a high-power rectifier to convert the alternating current (AC) from the grid into a direct current. This conversion either takes place in the vehicle itself using an on-board charger (OBC), or inside a (DC-)charging station. In both cases this conversion will have influence on the Power Quality in the grid.

This work aims to give insight in the possible Power Quality effects caused by OBCs, by assessing the behaviour of 9 different popular BEVs, covering 92% of all BEVs in The Netherlands based on data from the of end 2018. During controlled charging sessions at different charge speeds, the voltage and current are measured with a sample-rate of 500 kHz. Then, by analyzing the waveforms using Matlab, the different Power Quality parameters could be assessed. Of main interest were both classical- (up to 2 kHz) and supraharmonic (2 - 150 kHz) disturbances. Especially supraharmonics are interesting because emission in this range is still only partly standardized, potentially leading to problems with customer equipment, power line communication and interaction with other equipment. Furthermore, BEVs are a potential source of supraharmonic disturbances. The amount of reactive power (fundamental and harmonic), voltage unbalance and inrush current behaviour are also taken into account.

Main conclusion is that, expect one, all BEVs are a source of supraharmonic currents. This can have an effect on the grid due to the large share the tested BEVs have in The Netherlands and due to the fact that no limits exist yet for supraharmonic currents. Furthermore, when reducing the charge speed, the amount of reactive power increases while the harmonic distortions remains more or less constant. This leads to the recommendation to avoid reducing charge speed in order to ensure more efficient use of the grid and the converters, but it raises the question if this outweighs the potential extra losses due to the higher current. Voltage unbalance is caused by one-phase BEVs depending on the grid conditions and inrush currents are observed but inside the existing limits.

The main contributions of this paper are:
*An overview of the Power Quality effects on the LV-grid, caused by 9 popular BEVs at different charge speeds.
*Insight in Supraharmonic disturbances caused by BEV charging, and comparison of different emission profiles.
*Assessment of the mentioned effects and (where possible) comparison with limits.
Originele taal-2Engels
Titel2020 International Conference on Smart Energy Systems and Technologies (SEST)
StatusIngediend - apr 2020
Evenement3rd International Conference on Smart Energy Systems and Technologies (SEST) - Istanbul, Turkije
Duur: 7 sep 20209 sep 2020

Congres

Congres3rd International Conference on Smart Energy Systems and Technologies (SEST)
LandTurkije
StadIstanbul
Periode7/09/209/09/20

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Citeer dit

Slangen, T., van Wijk, T., Cuk, V., & Cobben, J. F. G. S. (2020). The impact of electric vehicles on the power quality in low-voltage grids. Manuscript ingediend voor publicatie. In 2020 International Conference on Smart Energy Systems and Technologies (SEST)