Today Tim Slangen received his PhD at the Technical University of Eindhoven (TU/e) for his research done at ElaadNL on power quality and the charging of electric vehicles. Slangen studied the phenomenon known as supraharmonic disturbances, which can be caused by electric vehicle charging and can adversely affect the lifetime, operation and efficiency of electrical appliances. The research can be used to determine what disturbances can be expected in the future and to advise manufactures and standardization bodies on mitigating measures.
“Electric vehicles convert AC voltage from the electrical grid to DC voltage to charge the batteries of vehicles using a rectifier. However, this charging can lead to disturbances on the electricity grid, one of which is known as supraharmonics.” says Tim Slangen, PhD researcher at the Department of Electrical Engineering at the TU/e.
But what are supraharmonics? Slangen explains: “Supraharmonics are waveform distortions in voltage and current with a frequency between 2 and 150 kHz. “Supra” means above or beyond, and refers to the disturbances being at a higher frequencies than traditional harmonics. It’s a topic that has gained a lot of interest over the last decade due to the increase in unwanted interference effects on the electrical network, such as audible noise, failure of consumer electronics, failing of cable terminations, and problems with residual current protection devices. The phenomenon is not new, but in the recent years due to the increasing number of large devices, like electric vehicle chargers, the interference has become more prominent. ”
With all of these issues at play with supraharmonics, a standardization solution is required to prevent more interference in the future, particularly as more and more large devices like electrical vehicles are put on the road and connected to the electricity network.
Nowadays, rectifiers are commonplace in our daily lives such as in the charger for a mobile phone or in LED lamps. “Even these small devices create supraharmonic disturbances that should and need to be addressed,” says Slangen. While the charging of these small devices can lead to supraharmonic disturbances for the electricity network, they are incomparable to the disturbances that can be created by larger devices, such as electric vehicle chargers.
For his PhD research, Tim Slangen explored in detail the phenomenon of supraharmonic disturbances, with a particular focus on supraharmonic emissions, summation, and propagation using a combination of laboratory and field experiments. At different locations throughout the Netherlands with multiple electric vehicle chargers, measurements were performed. The gathered data was then used to obtain an insight into the disturbances in practice. In a laboratory set-up at KEMA and the Elaad Testlab, several chargers were put to the test and different conditions simulated. The chargers were exposed to disturbances, different network configurations and tested for all their operating conditions to obtain a “fingerprint” of their disturbances.
“This research contributes to understanding the behavior of supraharmonic emissions caused by electric vehicle charging. The findings can be used to in to determine what disturbances can be expected in the future and to advise manufactures and standardization bodies on mitigating measures. In this way, smart and sustainable charging of electric vehicles, can be guaranteed.”
Because of the high frequency of supraharmonic distortions, their effect on electrical appliances, for instance in terms of additional heating, is larger than that of traditional disturbances like harmonics. This can lead to a reduced lifetime and failure of components. The research has identified the parameters that influence the emission. Slangen explains: “It is found that the created disturbances are for instance dependent on the state-of-charge of the battery connected to the charger. This has to be taken into account in future testing and certification of chargers, for instance by the ElaadNL testlab. Here, these findings are used to test all chargers and electric vehicles, even for issues that are not standardized yet. Furthermore, the research has found that supraharmonics can propagate further than initially thought, affecting a larger area.”
ElaadNL worked in the project ‘Future-proof Energy Networks through Power quality improvement of Electric Transport’, in addition to TU/e, together with DNV GL, KEMA Labs, Heliox, Enexis and Stedin. The aim of this project, subsidized by Top Sector Energy, was to provide grid operators with insight into the effect of supraharmonics and to arrive at concrete recommendations in the field of supraharmonics for industry. These recommendations are summarized in a white paper. The ElaadNL Test Lab has now shown that almost half of the tested vehicles meet the proposed limit.
Title of PhD thesis: Supraharmonics and Electric Vehicle Charging: Study on Emission, Summation and Propagation of Conducted Disturbances in the Frequency Range 2-150 kHz. Supervisors: J.F.G. Cobben and V. Cuk.
See also: TEPQEV whitepaper: Standards for 2-150 kHz