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Cited by 4Electric Vehicles and InfrastructureSmart Grid Energy ManagementOptimal Power Flow Distribution

Maximum Tolerated Number of Simultaneous BEV Charging Events in a Typical Low-Voltage Grid for Urban Residential Area

Open access
Fakhrooeian, Parnian, Hentrich, Rebecca, Pitz, Volker·2023·World Electric Vehicle Journal
DOI 10.3390/wevj14070165
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Abstract

In this paper, we determine the maximum number of battery electric vehicles (BEVs) that can be charged simultaneously at full power during peak load hour without overloading transformer and lines or causing an unacceptable voltage drop in the low-voltage (LV) grid. In order to predict the BEVs charging demand, an application that takes into account the random user’s arrival time and the initial battery state of charge (SOC) was developed using the C++ programming language and the Qt toolkit. The network analysis was then carried out using the Quasi-Dynamic Simulation (QDS) toolbox in DIgSILENT PowerFactory on a typical German LV grid for a metropolitan urban area. The simulation findings indicate that the value of simultaneity factor (SF) plays an important role in identifying the most robust and weakest grid’s bottlenecks. There is currently no immediate threat of electromobility pushing the parameters of the grid to their unacceptable limits; however, it is essential to examine the LV grid’s bottlenecks and gradually prepare them for the ramp-up of BEVs. In the short term, the bottlenecks can be removed using conservative planning and operating principles; however, employing novel approaches will be crucial in the longer term.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper determines how many battery electric vehicles (BEVs) can charge simultaneously at full power during the evening peak in a typical German urban low-voltage grid without violating transformer/line loading or voltage limits. It finds that the weakest bottleneck depends on the assumed simultaneity factor, and that the grid can tolerate limited simultaneous charging today but will need gradual reinforcement and new operating approaches for BEV ramp-up.

Key findings

  • In the base-load scenario, transformer loading peaked at 34.79% at 20:00; first-segment line loadings were 8.83% for the 150 mm² cable and 11.68% for the 240 mm² cable, with voltages at the final terminals of 0.987 p.u. and 0.988 p.u., respectively.
  • In the worst-case BEV scenario, the critical numbers of simultaneous charging events at peak hour were 7, 14, 20, and 47, corresponding to power demands of 0.077 MW, 0.154 MW, 0.22 MW, and 0.517 MW. Voltage fell to 0.948 p.u. in Feeder 1 from 7 simultaneous BEVs and 0.949 p.u. in Feeder 2 from 14; 14 simultaneous BEVs loaded the 150 mm² cable to 100.2%, while 20 simultaneous BEVs overloaded the 240 mm² cable to 102.6%; 47 simultaneous BEVs loaded the transformer to 121.58%.
  • The conclusions state that the LV grid with 270 residential units could support 46 simultaneous full-power charging events during peak hour, a 17% BEV penetration level, without transformer overloading. Feeders with 27 residential units each could handle 19 (70%) and 13 (48%) BEVs without line overloading for 240 mm² and 150 mm² cables, while voltage limits allowed 13 (48%) and 6 (22%) BEVs, respectively.
  • Using VDE FNN simultaneity factors, 77 kW total charging power corresponded to 22 charging points at SF = 0.32; with SF = 1, a 26% BEV penetration caused unacceptable voltage drop in Feeder 1, whereas with the realistic SF the same outcome occurred at 81% penetration.

Methods

  • A representative German metropolitan urban LV grid was developed from statistical analysis of grid data from Syna GmbH and RegioStaR, based on 4020 local substations; it uses a 630 kVA MV/LV transformer, 10 feeders with 9 house connections each (27 residential units per feeder), and 0.29 km feeder length.
  • BEV charging demand was modeled with a C++/Qt application: arrival time uniform between 16:00 and 18:00, initial SOC normal with mean 25% and standard deviation 10%, wallbox power 11 kW, battery capacity 64 kWh, charging to 80% SOC, and one charge per day.
  • Grid analysis used the Quasi-Dynamic Simulation toolbox in DIgSILENT PowerFactory Version 2019 on 1 July 2022, a typical summer day, with 5-minute resolution; two scenarios were simulated, and BEVs were added sequentially from the feeder end toward the substation until voltage, line-loading, or transformer-loading limits were reached.

Limitations

  • The paper states that only a typical summer day was analyzed because summer and winter generally have the highest electricity consumption, and that winter-day studies will be covered in expansion of the work.
  • The paper states that renewable energy sources were not included because worst-case scenarios were modeled and the residential peak load hour was at 20:00, making RES generation at that time not particularly useful for charging BEVs.
  • Evident from the text: the results depend on one representative urban grid, assumed stochastic arrival/SOC distributions, identical BEV profiles per feeder, one BEV per residential unit, and worst-case SF = 1 for the critical-number calculations, with realistic VDE FNN SF values applied only in the discussion.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/wevj14070165

Cites

17 of 17 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 10 cited sources checked · 1 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    Line/transformer loadings have not been covered in Spitzer et al. [18].

    “but line/transformer loadings have not been covered.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [18] Spitzer, M., Schlund, J., Apostolaki-Iosifidou, E., and Pruckner, M. (2019). Optimized integration of electric vehicles in low voltage distribution grids. Energies, 12. source

      Section 4.1 (Uncoordinated Charging) examines transformer apparent power against its rated limit in Figure 5, even though the authors exclude it as a formal analysis criterion. Section 4.2.1 (Cost Optimized Strategy) also discusses cable current-limit violations and a transformer constraint. Thus, the paper covers both line and transformer loading. (LLM, conf=0.90)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    Urban grids have not been considered in Held et al. [17].

    “however, urban grids have not been considered.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [17] Held, L., Märtz, A., Krohn, D., Wirth, J., Zimmerlin, M., Suriyah, M.R., Leibfried, T., Jochem, P., and Fichtner, W. (2019). The influence of electric vehicle charging on low voltage grids with characteristics typical for Germany. World Electr. Veh. J., 10. source
  • Findingown data

    A total of 14 simultaneous BEV charging events led to 100.2% loading in the first section of NAYY 4 × 150 mm2 cable.

    “A total of 14 sim ultaneous BEV charging events led to 100.2% loading in the first section of NAYY 4 × 150 mm 2 cable, as seen in Figure 5”
    Quote in the paperSubstantial claim
  • Findingown data

    The 240 mm2 cable was overloaded by 102.6% due to 20 simultaneous BEVs charging events.

    “The 240 mm 2 cable was overloaded by 102.6% due to 20 simultaneous BEVs charging events”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The maximum short-term overloads for the transformer and lines are 120% and 100%, respectively.
  • Findingown data

    The 150 mm2 cable was subject to an additional 39.2% overloading that could cause the cable to overheat.

    “whereas the 150 mm 2 cable was subject to an addi tional 39.2% overloading that could cause the cable to overheat.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The maximum short-term overloads for the transformer and lines are 120% and 100%, respectively.
  • May combine two claims. 18
  • Classified as probably not a substantial claim. 7

  • May combine two claims.

    Findingown data

    Each house connection in a metropolitan urban area consists of three residential units, with a total yearly consumption of 13,500 kWh.

    “The evaluation of the network data indicates that each house connection in a metropolitan urban area consists of three residential units, with a total yearly consumption of 13,500 kWh.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    Depending on the number of connected residential units, the cable types NAYY 4 × 35 mm2 or NAYY 4 × 50 mm2 were utilized for house connection cables.

    “On the other hand, depending on the number of connected residential units, the cable types NAYY 4 × 35 mm 2 or NAYY 4 × 50 mm 2 were utilized for house connection cables.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In Feeder 1 (150 mm2 cable) and Feeder 2 (240 mm2 cable), the minimum voltage fell to 0.948 p.u. and 0.949 p.u., respectively, thus exceeding the acceptable 0.95 p.u. limit; it resulted from 7 and 14 simultaneous BEV charging processes respectively.

    “In Feeder 1 (150 mm 2 cable) and Feeder 2 (240 mm 2 cable) the minimum voltage fell to 0.948 p.u. and 0.949 p.u., respectively, thus exceeding the acceptable 0.95 p.u. limit.; it resulted from 7 and 14 simultaneous BEV charging processes respectively.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The voltage deviation at the LV level is restricted to ±5% of the nominal voltage.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    A cross-section of 240 mm2 was used for lines that supply a high load.

    “A cross-section of 240 mm 2 was used for lines that supply a high load.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The maximum loadings for the first segment of cables with cross sections of 150 mm2 (Feeder 1) and 240 mm2 (Feeder 2) were 8.83% and 11.68%, respectively.

    “The maximum loadings for the first segment of cables with cross sections of 150 mm 2 (in Feeder 1) and 240 mm 2 (in Feeder 2) were 8.83% and 11.68%, respectively.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Typically, there are 8 ± 2 feeders at the 0.4 kV level; each feeder has a main line that is 0.25 ± 0.04 km long and serves 8 ± 1 house connections.

    “Typically, there are 8 ± 2 feeders at the 0.4 kV level; each feeder has a main line that is 0.25 ± 0.04 km long and serves 8 ± 1 house connections.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At 20:00, the voltage magnitude in Feeder 1 (150 mm2 cable) and Feeder 2 (240 mm2 cable) dropped to 0.987 p.u. and 0.988 p.u., respectively.

    “At 20:00, the voltage magnitude in Feeder 1 (150 mm 2 cable) and Feeder 2 (240 mm 2 cable) dropped to 0.987 p.u. and 0.988 p.u., respectively.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning

    In scenario #2 and the VDE FNN study, the most challenging parameters were transformer overloading (at 17% penetration) and under-voltage at Feeder 1's (150 mm2 cable) final house connection (at 81% penetration).

    “in scenario #2 and the VDE FNN study, the most challenging parameters were, the transformer overloading (at 17% penetration) and the under-voltage at Feeder 1's (150 mm 2 cable) final house connection (at 81% penetration).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites VDE FNN study

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingown data

    Feeders with 240 mm2 and 150 mm2 cables, each containing 27 residential units, could handle the penetration of 19 (70%) and 13 (48%) BEVs without line overloading.

    “With cable cross sections of 240 mm 2 and 150 mm 2 , respectively, the feeders-each of which contained 27 residential units-could handle the penetration of 19 (70%) and 13 (48%) BEVs without lines overloading”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The voltage at the last house connections of the 240 mm2 and 150 mm2 cables allowed for the penetration of 13 (48%) and 6 (22%) BEVs along the feeders, respectively.

    “the voltage at the last house connections of these cables allowed for the penetration of 13 (48%) and 6 (22%) BEVs along the feeders, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The 240 mm2 cable was overloaded by 102.6% due to 20 simultaneous BEV charging events, whereas the 150 mm2 cable was subject to an additional 39.2% overloading.

    “The 240 mm 2 cable was overloaded by 102.6% due to 20 simultaneous BEVs charging events, whereas the 150 mm 2 cable was subject to an additional 39.2% overloading that could cause the cable to overheat.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Assuming each residential unit had only one BEV, the overloading of the transformer and lines, as well as the under-voltage in Feeder 2 (240 mm2 cable), did not occur when calculating BEV penetration levels using the VDE FNN study data.

    “Since we assumed that each residential unit only had one BEV, the overloading of the transformer and lines, as well as the under-voltage in Feeder 2 (240 mm 2 cable), did not occur when calculating the BEV penetration levels using the data from the VDE FNN study.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites VDE FNN study

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • The authors state this as an assumption: Each residential unit only had one BEV.

  • May combine two claims.

    Findingown data

    A total of 14 simultaneous BEV charging events led to 100.2% loading in the first section of NAYY 4 × 150 mm2 cable, while for the same circumstance the loading of NAYY 4 × 240 mm2 cable was 74.06%.

    “A total of 14 simultaneous BEV charging events led to 100.2% loading in the first section of NAYY 4 × 150 mm 2 cable, as seen in Figure 5; however, for the same circumstance, the loading of NAYY 4 × 240 mm 2 cable was 74.06%.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    With 27 residential units in each feeder, a 26% BEV penetration level resulted in an unacceptable voltage drop in Feeder 1 (150 mm2 cable) when considering the SF of 1; with the realistic SF value, the same outcome would occur at a BEV penetration level of 81%.

    “With 27 residential units in each feeder, a 26% BEV penetration level resulted in an unacceptable voltage drop in Feeder 1 (150 mm 2 cable) when considering the SF of 1; nevertheless, by taking into account the realistic value of the SF, the identical outcome would occur at a BEV penetration level of 81%.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In Feeder 1 (150 mm2 cable) and Feeder 2 (240 mm2 cable), the minimum voltage fell to 0.948 p.u. and 0.949 p.u., respectively, exceeding the acceptable 0.95 p.u. limit; this resulted from 7 and 14 simultaneous BEV charging processes, respectively.

    “In Feeder 1 (150 mm 2 cable) and Feeder 2 (240 mm 2 cable), the minimum voltage fell to 0.948 p.u. and 0.949 p.u., respectively, thus exceeding the acceptable 0.95 p.u. limit.; it resulted from 7 and 14 simultaneous BEV charging processes, respectively.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given

    The electrical grid may experience a considerable increase in the load demand as a result of charging a large number of EVs; however, the stochastic behavior of the users prevents the charging operations from taking place simultaneously.

    “The electrical grid may experience a considerable increase in the load demand as a result of charging a large number of EVs; however, the stochastic behavior of the users prevents the charging operations from taking place simultaneously.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Transformer loading, random arrivals, and the random initial SOC of EVs have not been addressed in Held et al. [16].

    “However, transformer loading, random arrivals, and the random initial SOC of EVs have not been addressed.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [16] Held, L., Uhrig, M., Suriyah, M., Leibfried, T., Junge, E., Lossau, S., and Konermann, M. (2017, January 23–24). Impact of electric vehicle charging on low-voltage grids and the potential of battery storage as temporary equipment during grid reinforcement. Proceedings of the E-Mobility Integration Symposium, Berlin, Germany.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    15 million registered electric vehicles (EVs) are expected to be on the road by 2030, according to German policymakers.

    “15 million registered electric vehicles (EVs) are expected to be on the road by 2030, according to German policymakers [3].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [3] The German Federal Government (2023, June 07). Not Moving Less, but Moving Differently. Available online: https://www.bundesregierung.de/breg-de/themen/klimaschutz/eenergie-und-mobilitaet/nachhaltige-mobilitaet-2044132.

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Line overloading was the least problematic parameter among the bottlenecks in the urban LV grid, as it supported the most BEV charging events in a feeder.

    “By supporting the most BEV charging events in a feeder, line overloading was the least problematic parameter among the bottlenecks in the urban LV grid.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    According to the VDE FNN study, as the number of charging points in the grid rose, the probability that BEVs were charged simultaneously decreased, and at one point the SF value remained constant.

    “According to the VDE FNN study, as the number of charging points in the grid rose, the probability that the BEVs were charged simultaneously decreased, and, at one point, the SF value remained constant.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites VDE FNN study

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    To reflect the worst-case scenario, the longest main line length, as well as the greatest number of feeders and house connections resulting from the average values plus deviations, were utilized in this study.

    “To reflect the worst-case scenario, the longest main line length, as well as the greatest number of feeders and house connections resulting from the average values plus deviations, were utilized in this study.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    Identical BEV profiles were used in each feeder to provide the same condition so that the impact of BEVs on the voltage magnitude and the loading of cables with cross sections of 150 mm2 and 240 mm2 could be more effectively compared.

    “It should be noted that identical BEV profiles were used in each feeder to provide the same condition so that the impact of BEVs on the voltage magnitude and the loading of cables with cross sections of 150 mm 2 and 240 mm 2 could be more effectively compared.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductreasoning

    The study modeled worst-case scenarios for the LV grid and therefore did not include any generation from renewable energy sources (RESs) in its simulations.

    “It should be emphasized that, since we modeled the worst-case scenarios for the LV grid in this paper, we did not include any generation from renewable energy sources (RESs) in our simulations.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The paper only included findings for a typical summer day.

    “this paper only included the findings for a typical summer day”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Summer and winter are generally the seasons with the highest electricity consumption.
24 of 24

  • The authors state this as an assumption.

    The maximum short-term overloads for the transformer and lines are 120% and 100%, respectively.

    “The maximum short-term overloads for the transformer and lines were assumed to be 120% and 100%, respectively, based on empirical values of aging processes and typical planning and operating principles for urban distribution networks [26].”

  • The authors state this as an assumption.

    The voltage deviation at the LV level is restricted to ±5% of the nominal voltage.

    “The voltage deviation at the LV level was restricted to ±5% of the nominal voltage to ensure that the voltage band was maintained, even in the worst-case scenario, i.e., when a local substation uses a transformer with a fixed voltage ratio.”

  • The authors state this as an assumption.

    The peak hour for the residential area and the BEVs charging processes must coincide when modeling the BEV profiles.

    “In order to create the worst-case scenario for the grid's load, we assumed that the peak hour for the residential area and the BEVs charging processes must coincide when modeling the BEV profiles (Section 2.2).”

  • The authors state this as an assumption.

    The BEVs were connected sequentially to the residential units, starting at the end of the feeder and moving toward the local grid substation; there was only one BEV per residential unit.

    “To generate the worst-case scenario for the voltage drop, we assumed that the BEVs were connected sequentially to the residential units, starting at the end of the feeder and moving toward the local grid substation; there was only one BEV per residential unit.”

  • The authors state this as an assumption.

    The BEV is only charged once each day.

    “The assumption was made that the BEV is only charged once each day.”

  • The authors state this as an assumption.

    The charging procedure is completed once the BEV battery SOC level reaches 80%.

    “The charging procedure would be completed once the BEV battery SOC level reaches 80%.”

  • The paper relies on this without support.

    Users accept a lower SOC value due to the availability of wallbox charging stations at home and the awareness that BEV charging would undoubtedly be possible once they arrive.

    “In terms of SOC, users were expected to accept a lower SOC value due to the availability of wallbox charging stations at home and the awareness that BEV charging would undoubtedly be possible once they arrive.”

  • The authors state this as an assumption.

    Each wallbox provides 11 kW.

    “Assuming that each wall box provides 11 kW”

  • The authors state this as an assumption.

    Each residential unit only had one BEV.

    “Since we assumed that each residential unit only had one BEV”

  • The paper relies on this without support.

    Summer and winter are generally the seasons with the highest electricity consumption.

    “Due to the fact that summer and winter are generally the seasons with the highest electricity consumption”

  • The paper relies on this without support.

    Using SF=1 imposes a substantial cost for grid construction.

    “Although the SF of 1 assures that the specified number of charging processes can be carried out, even during peak hour, it imposes a substantial cost for grid construction.”
11 of 11

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Authors
Fakhrooeian, P., Hentrich, R., & Pitz, V.
Affiliations
  • RheinMain University of Applied Sciences (DE)
  • Syna GmbH, 65929 Frankfurt am Main, Germany
Corresponding author
Fakhrooeian, Parnian
ORCID
Venue
World Electric Vehicle Journal
Publisher
MDPI AG
Published
2023-06-24
Volume
14
Issue
7
Pages
165
ISSN
2032-6653 (ISSN-L)
DOI
10.3390/wevj14070165
OpenAlex
W4382135188
Cited by
4
References
17
Citations by year
2026: 1 · 2025: 2 · 2024: 1
FWCI
0.29
Type
journal article
Language
en
Open access
Licence
Locations
  • World Electric Vehicle Journal (publishedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Publication Server of Goethe University Frankfurt am Main (Goethe University Frankfurt) (cc-by)
Funders
  • German Federal Ministry for Economic Affairs (FKZ: 01MZ18008B)
  • Climate Action (FKZ: 01MZ18008B)
Topics
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Electric Vehicles and Infrastructure
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Smart Grid Energy Management
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Optimal Power Flow Distribution
Keywords
battery electric vehicles, low-voltage distribution networks, grid bottlenecks, voltage drop, transformer overload, charging demand prediction, state of charge, time of arrival, urban residential areas, electric mobility, power grid planning

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