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- Nakhodchi, Naser, et al.
(författare)
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Impact of modelling of MV network and remote loads on estimated harmonic hosting capacity for an EV fast charging station
- 2023
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Ingår i: International Journal of Electrical Power & Energy Systems. - : Elsevier. - 0142-0615 .- 1879-3517. ; 147
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Tidskriftsartikel (refereegranskat)abstract
- The ability of the distribution network to host electric vehicle (EV) charging might be limited by the harmonic voltages due to their harmonic emission. Network harmonic impedance seen from the point of connection of the charging station plays an important role in harmonic voltage calculation. In this paper, the hosting capacity is estimated for a fast charging station close to a distribution transformer considering different scenarios in terms of network modelling. Data from a typical Swedish distribution network is used, together with a one-month measurement of the emission from state-of-the-art EV charging. The hosting capacity using harmonic voltage limits is compared with the hosting capacity using the transformer rating. A stochastic approach is used for both. This paper shows that harmonic hosting capacity studies are needed; it shows that details of the distribution network must be included to get an accurate estimation of the harmonic hosting capacity; it also shows that a stochastic approach is needed for estimating the harmonic hosting capacity.
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| 3. |
- Nakhodchi, Naser, et al.
(författare)
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Including uncertainties in harmonic hosting capacity calculation of a fast EV charging station utilizing Bayesian statistics and harmonic correlation
- 2023
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Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 214
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Tidskriftsartikel (refereegranskat)abstract
- The harmonic emission from an electric vehicle fast charger depends on factors like charger topology, EV type, initial state of charge of EV battery, as well as supply voltage and background distortion. This paper presents the results from harmonic current measurement of a fast charger for a period of one month in Sweden that has charged a variety of EVs from different brands under different state of charge and background distortion. Besides the common harmonic emission pattern, a high level of variation in emission is observed that can affect the aggregation of the emission from multiple chargers. To include such uncertainties, the harmonic hosting capacity is obtained for a fast EV charging station in a stochastic way. A new method, based on Bayesian statistics and the correlation between harmonic magnitude and fundamental magnitude, is proposed for the generation of stochastic samples. It is shown that the proposed method, to a high extent, can model the stochastic behavior of harmonic emission from a fast charger. Furthermore, the results show that neglecting the correlation between harmonic magnitude and fundamental magnitude can underestimate the harmonic hosting capacity.
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| 4. |
- Nakhodchi, Naser, 1981-
(författare)
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On Harmonics in Low-voltage Networks
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- On the road to reducing global warming, the use of renewable energy sources and efficient use of electricity are among the key aspects. The increasing number of energy efficient appliances such as LED lamps, booming demand for electric vehicles (EVs), and growing penetration of distributed energy resources such as photovoltaic (PV) systems in low-voltage (LV) networks are expected to affect the power quality in the entire electric power system and specifically in the LV network, where such new devices are connected. Waveform distortion, mainly expressed by the harmonic components, is one of the topics within power quality that is highly affected by the introduction of such new devices. However, there is a lack of publications discussing the existing level of voltage harmonics in LV networks or addressing the origin and transfer of harmonics in LV and MV distribution networks. This highlights the need for more research in this field.To evaluate the ability of the network to host new sources of harmonics, the existing harmonic voltage and current levels as well as the impact of these new sources on those levels should be investigated. Harmonic levels are determined by emission from harmonic sources, the propagation from other harmonic sources, and the aggregation between the contributions from different sources. Studies on harmonic emission from a variety of different individual devices under different conditions have already been carried out. However, limited knowledge is available about the harmonic aggregation and propagation in LV networks. This study aims to improve the understanding about the behaviour of harmonics in LV networks covering both aggregation and propagation.In the first part of this work, the impact of the MV network and remote LV loads on the harmonic voltage in the LV network are examined. Simulation results have revealed that for frequencies below the resonant frequency of the local LV network the harmonic voltage levels mainly are determined by aggregated emission of the whole distribution network (both LV and MV) rather than by the emission from local LV loads. Furthermore, a graphical method is introduced for harmonic propagation studies, using measurements but without the need for accurate synchronized measurements.In the second part of this work, the aggregated emission from a group of EV fast chargers is examined. A stochastic method, based on Bayesian statistics and harmonic correlation, was used to include uncertainties in harmonic hosting capacity calculation for an EV charging station equipped with fast chargers. The impact of MV network and remote LV loads on harmonic hosting capacity is investigated. It is also shown that harmonic hosting capacity studies are needed; and details of the distribution network must be included to get an accurate estimation of the harmonic hosting capacity.Finally, an alternative method for time aggregation of harmonic phase angle is proposed in this work.In general, this work contributes to reducing the research gaps recognized in harmonic analysis in the LV networks considering propagation and aggregation utilizing both simulation and measurement.
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| 5. |
- Sudha Letha, Shimi, et al.
(författare)
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Power Quality Issues of Electro-Mobility on Distribution Network—An Overview
- 2023
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 16:13
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Forskningsöversikt (refereegranskat)abstract
- The journey towards sustainable transportation has significantly increased the grid penetration of electric vehicles (EV) around the world. The connection of EVs to the power grid poses a series of new challenges for network operators, such as network loading, voltage profile perturbation, voltage unbalance, and other power quality issues. This paper presents a coalescence of knowledge on the impact that electro-mobility can impose on the grid, and identifies gaps for further research. Further, the study investigates the impact of electric vehicle charging on the medium-voltage network and low-voltage distribution network, keeping in mind the role of network operators, utilities, and customers. From this, the impacts, challenges, and recommendations are summarized. This paper will be a valuable resource to research entities, industry professionals, and network operators, as a ready reference of all possible power quality challenges posed by electro-mobility on the distribution network.
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