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Cited by 1Electric Vehicles and InfrastructureSmart Grid Energy ManagementOptimal Power Flow Distribution

Optimal Operation of Electric Vehicles to Enhance the Flexibility Provision in Active Distribution Grids

Panagi, Savvas, Therapontos, Phivos, Spanias, Chrysovalantis, Aristidou, Petros·2025·2025 IEEE Kiel PowerTech
DOI 10.1109/powertech59965.2025.11180664
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Abstract

The continuously increasing integration of electric vehicles (EVs) introduced significant challenges to modern power systems, while at the same time offering big opportunities for more optimal and effective operation. This study presents an operational day-ahead scheduling optimization framework to mitigate the negative impacts of EV charging while maximizing flexibility services in active distribution networks. The presented framework employs a non-linear optimal power flow model that ensures compliance with network constraints and accommodates EV user preferences. The proposed methodology is validated through realistic test case scenarios to illustrate its operational feasibility. The results reveal that in suburban areas, flexibility during working hours is limited, while flexibility during return-home hours is significantly higher. In general, the increasing adoption of electric vehicles offers substantial potential for effectively managing distribution networks.

AI snapshot

Written from the paper’s full text.

TL;DR

This paper proposes a nonlinear OPF-based day-ahead scheduling framework to maximize EV flexibility services in active distribution grids while respecting network constraints and EV user preferences. In a realistic Cyprus suburban LV network, upward flexibility exceeds downward flexibility because discharging is disabled, and flexibility is limited during working hours but high during return-home hours.

Key findings

  • Upward flexibility was much greater than downward flexibility since discharging was disabled; downward flexibility represented postponed charging (reduced charging power).
  • At peak load around 18:00, the maximum voltage deviation between maximum downward and upward flexibility activation was about 0.02 p.u.; upward flexibility during 18:00–05:00 could increase transformer loading until limits.
  • During the first stress period around 12:00–14:00, when overvoltages can occur, maximum upward/downward flexibility activation produced no significant voltage variation, so flexibility activation cannot provide an important improvement in the voltage profile. During the second stress period around 18:00–21:00, when undervoltage and overload problems occur, flexibility capabilities peaked due to high EV connectivity.
  • Aggregate EV charging power did not exceed 21 kW despite most chargers having an 11 kW maximum, because charging was performed uniformly over time to maximize flexibility; the average computational time was approximately 13 minutes.

Methods

  • Day-ahead nonlinear OPF maximizing EV flexibility, with constraints for power balance, network limits, DER operation, EV user preferences, and flexibility for full upward/downward activation (s = 0 for full downward, s = 1 for full upward). Solved with IPOPT; average computational time approximately 13 minutes.
  • Case study on a realistic symmetric LV distribution network from the Cyprus DSO in a suburban area: an 11/0.4 kV, 315 kVA transformer, three radial feeders, 61 nodes, each feeder serving approximately 30–50 residential customers. EV driving patterns came from a Cyprus survey for weekdays; the 10 most popular 2024 European EVs were considered; 20% of customers were assumed to have EVs; 80% of residential buildings were detached three-phase houses using 11 kW charging, and the remaining 20% were one-phase using 3.7 kW.
  • Basic load used the average consumption of 68 residential houses for May; rooftop PV had maximum 4.16 kWp one-phase and 10.4 kWp three-phase, with the same profile scaled by installed capacity and VDE4105 power-factor control. Analysis compared voltage and transformer loading under maximum flexibility activations and aggregate charging/flexibility.

Limitations

  • Stated: unidirectional charging only is considered due to EV converter limitations and battery degradation from discharging. A real-time methodology is needed because flexibility changes with user preferences and DSO actions. Future work includes solving approximations to reduce computational costs, developing a real-time algorithm, and enhancing the framework to control DERs and flexible loads.
  • Stated: in peak PV generation periods, flexibility was much lower and may not be enough to avoid overvoltages in suburban networks.
  • Evident: results are based on one Cyprus suburban LV network, a May load/PV profile, and a local driving survey, so generalization to other networks, seasons, or locations is not established; the approximately 13-minute solve time may also limit repeated day-ahead use, which the paper acknowledges as future work to reduce computational costs.

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

Integrity signals

Registry

Crossref · 10.1109/powertech59965.2025.11180664

Cites

0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 14 cited sources checked · 0 supported · 1 flagged · accuracy not yet measured

  • Findingreasoning
    § A. Flexibility · p. 5

    During the second stress period around 18:00-21:00, when operators observed undervoltage and overload problems, flexibility capabilities were at peak due to high connectivity.

    “In addition, during the second stress period (around 18:00-21:00), when operators observed undervoltage and overload problems, flexibility capabilities was at peak due to high connectivity.”
    Quote in the paperSubstantial claim
  • Findingnone given
    § VI. CONCLUSIONS · p. 6

    In peak photovoltaic generation periods, there was much lower flexibility available, which may not be enough to avoid overvoltages in suburban networks.

    “However, in peak PV generation periods, there was much lower flexibility available, which may not be enough to avoid overvoltages in suburban networks.”
    Quote in the paperSubstantial claim
  • Findingown data
    § A. Flexibility · p. 5

    In peak load demand hours around 18:00, there was a maximum voltage deviation around 0.02 p.u. between maximum downward and upward flexibility activation.

    “In peak load demand hours (around 18:00) there was a maximum voltage deviation around 0.02 p.u. between maximum downward and upward flexibility activation.”
    Quote in the paperNot a substantial claim
  • Findingown data
    § A. Flexibility · p. 5

    During the first stress period around 12:00-14:00, where overvoltages can occur in the distribution network, the voltage operation range after maximum activation of upward and downward flexibility did not present any significant variations.

    “Taking into consideration the above, the results show that during the first stress period (around 12:00-14:00), where overvoltages can occur in DN, the voltage operation range after a maximum activation of the upward and downward flexibility did not present any significant variations.”
    Quote in the paperSubstantial claim
  • Premisecitation
    § I. INTRODUCTION · p. 1

    The increasing integration of renewable energy sources and the extensive use of electric vehicles introduce new levels of uncertainty and variability to modern power systems.

    “The increasing integration of Renewable Energy Sources (RES) and the extensive use of Electric Vehicles (EVs) are introducing new levels of uncertainty and variability to modern power systems.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [1] [1] C. Diaz-Londono, P. Maffezzoni, L. Daniel, and G. Gruosso, 'Flexibility of electric vehicle chargers in residential, workplace, and public locations based on real-world data,' in IEEE EUROCON 2023 - 20th International Conference on Smart Technologies , 2023, pp. 354-359. - source
  • May combine two claims. 15
  • Classified as probably not a substantial claim. 12
  • The quote only partly states this claim. 1

  • May combine two claims.

    Premisecitation
    § I. INTRODUCTION · p. 2

    The approach in [13] focused on real-time operations, relying solely on current conditions and ignoring network constraints.

    “Although, this approach focused on real-time operations, relying solely on current conditions and ignoring network constraints.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [13] [13] C. Diaz-Londono, L. Colangelo, F. Ruiz, D. Patino, C. Novara, and G. Chicco, 'Optimal strategy to exploit the flexibility of an electric vehicle charging station,' Energies , vol. 12, no. 20, p. 3834, 2019. - source

      Section 3 (Solution Strategies; page not provided) says the proposed strategies use forecast values together with new information. Section 3.2 says the controller plans over a future interval while accounting for current and future constraints, then updates the plan at each time slot. This contradicts the claim that it relies solely on current conditions; the cited passages do not establish whether distribution-network constraints are included. (LLM, conf=0.88)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation
    § I. INTRODUCTION · p. 1

    Electric vehicles are parked and available to provide grid services for 90% of the time, making them a highly reliable resource for grid support.

    “Studies reveal that EVs are parked and available to provide grid services for 90% of the time, making them a highly reliable resource for grid support [3], [4].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [3] [3] C. Gouveia, C. L. Moreira, J. A. P. Lopes, D. Varajao, and R. E. Araujo, 'Microgrid service restoration: The role of plugged-in electric vehicles,' IEEE Industrial Electronics Magazine , vol. 7, no. 4, pp. 26-41, 2013. - source

      The Introduction (page not provided) says EVs parked and connected for charging can provide storage capacity, and Section 3 describes how they can support microgrid restoration. The paper does not give a 90% parking or availability figure, so it does not establish the claimed level of reliability. Searches for “90% of the time” and parking availability found no such figure. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [4] [4] W. Kempton and J. Tomi´ c, 'Vehicle-to-grid power implementation: From stabilizing the grid to supporting large-scale renewable energy,' Journal of Power Sources , vol. 144, no. 1, pp. 280-294, 2005. - source

  • May combine two claims.

    Findingown data
    § Optimal Operation of Electric Vehicles to Enhance the Flexibility Provision in Active Distribution Grids · p. 1

    In suburban areas, flexibility during working hours is limited, while flexibility during return-home hours is significantly higher.

    “The results reveal that in suburban areas, flexibility during working hours is limited, while flexibility during returnhome hours is significantly higher.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given
    § A. Flexibility · p. 5

    Flexibility was impacted by the cost parameter C_s,t and was also affected by the connectivity of electric vehicles.

    “Although flexibility was impacted by the cost parameter C s,t , it was also affected by the connectivity of electric vehicles.”
    Quote in the paperSubstantial claim

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

    Findingown data
    § V. RESULTS AND DISCUSSIONS · p. 5

    The average computational time for solving the day-ahead scheduling problem was approximately 13 minutes.

    “the average computational time for solving the day-ahead scheduling problem was approximately 13 minutes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning
    § B. Charging Power · p. 6

    Although most chargers have a maximum power of 11 kW, the charging power of all electric vehicles does not exceed 21 kW, since the charging process was performed uniformly over time to maximize flexibility.

    “It was obvious that although most chargers have a maximum power of 11kW, the charging power of all electric vehicles does not exceed 21 kW, since the charging process was performed uniformly over time to maximize flexibility.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning
    § A. Flexibility · p. 5

    Upward flexibility was much more than downward flexibility because the discharging function was disabled.

    “It was obvious that the upward flexibility was much more than the downward flexibility since the discharging function was disabled.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § A. Flexibility · p. 5

    The upward flexibility during 18:00-05:00 can increase transformer loading until it reaches the limits, validating the high-power capabilities of electric vehicle chargers.

    “The upward flexibility during 18:0005:00 can increase the transformer loading until it reaches the limits, validating the high-power capabilities of EV chargers.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given
    § A. Flexibility · p. 5

    Each distribution network faces different problems based on its location, type of customers, and design structure.

    “Each distribution network faces different problems based on their location, type of customers, and design structure.”
    Quote in the paperNot a substantial claim

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

    Interpretationreasoning
    § C. Real-time flexibility activations · p. 6

    If the distribution system operator decides to take an upward action in a certain period, then the state of charge will be affected; this change will reduce the upward flexibility and at the same time increase the downward flexibility for the next periods.

    “For example, if DSO decides to take some upward action in a certain period, then SoC will be affected; this change will reduce the upward flexibility and, at the same time, increase the downward flexibility for the next periods.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Study design and conductnone given
    § III. OPF MODELING FRAMEWORK · p. 3

    The constraints ensure power balance, compliance with network limits, operation of distributed energy resources, user preferences, and flexibility capabilities of electric vehicles for both full activation of upward or downward flexibility.

    “The constraints ensure power balance, compliance with network limits, operation of the DERs, user preferences, and flexibility capabilities of the EV for both full activation of upward or downward flexibility.”
    Quote in the paperNot a substantial claim

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

    Study design and conductnone given
    § V. RESULTS AND DISCUSSIONS · p. 5

    The solver successfully converged to a feasible solution in all scenarios tested.

    “The solver successfully converged to a feasible solution in all scenarios tested”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisenone given
    § A. Flexibility · p. 5

    The network under study was a suburban network with mainly residential three-phase power supply customers.

    “The network under study was a suburban network with mainly residential three-phase power supply customers.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationnone given
    § A. Flexibility · p. 5

    Suburban networks with mainly residential three-phase power supply customers face problems during high generation time periods because of high reverse power flow and during the early evening when residents return home and a sharp increase in the load profile is observed.

    “Those kinds of networks face problems during high generation time periods because of the high reverse power flow and during the early evening when residents return to home, and a sharp increase in the load profile is observed.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premiseown data
    § A. EV Modeling and Data · p. 4

    In Cyprus suburban areas, 80% of residential buildings are detached houses equipped with a three-phase power system and use 11 kW charging systems, while the remaining 20% are considered to have a one-phase power system and use 3.7 kW charging systems.

    “Based on data provided by the DSO, in Cyprus suburban areas 80% of residential buildings are detached houses equipped with a three-phase power system; therefore, 11 kW charging systems are used for those customers. The remaining (20%) are considered to have a one-phase power system and for those 3.7 kW (one-phase) charging system are considered.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationnone given
    § Optimal Operation of Electric Vehicles to Enhance the Flexibility Provision in Active Distribution Grids · p. 1

    The increasing adoption of electric vehicles offers substantial potential for effectively managing distribution networks.

    “In general, the increasing adoption of electric vehicles offers substantial potential for effectively managing distribution networks.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given
    § C. PV Generation Profile · p. 4

    The maximum power of the one-phase and three-phase photovoltaic installations is 4.16 kWp and 10.4 kWp respectively, based on limits set by the distribution system operator.

    “The maximum power of the one-phase and three-phase is 4.16 kWp and 10.4 kWp respectively, based on the limits set by the DSO.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisenone given
    § B. Basic Household Load Profiles · p. 4

    May was selected as the month that exhibits the highest difference between the peak generation of distributed energy resources and the peak load consumption.

    “For this case study, May was selected as the month that exhibits the highest difference between the peak generation of DER and the peak load consumption.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § I. INTRODUCTION · p. 1

    These developments impose significant challenges to system operators in maintaining power balance in real time and dealing with fluctuating renewable energy source production and unpredictable electric vehicle charging patterns.

    “These developments impose significant challenges to the system operators in maintaining power balance in real time and dealing with the fluctuating nature of RES production and the unpredictable charging patterns of EVs [1].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [1] [1] C. Diaz-Londono, P. Maffezzoni, L. Daniel, and G. Gruosso, 'Flexibility of electric vehicle chargers in residential, workplace, and public locations based on real-world data,' in IEEE EUROCON 2023 - 20th International Conference on Smart Technologies , 2023, pp. 354-359. - source

  • May combine two claims.

    Premisereasoning
    § I. INTRODUCTION · p. 2

    Existing electric vehicle operation scheduling approaches that optimize a specific objective do not consider the flexibility that electric vehicles can provide to the network, overlooking suboptimal or near-optimal solutions that could enhance flexibility services.

    “Although these approaches optimize a specific objective and improve the operation of the EV, they do not consider the flexibility that EVs can provide to the network. Consequently, suboptimal or near-optimal solutions that could enhance flexibility services are overlooked.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Interpretationown data
    § A. Flexibility · p. 5

    Flexibility activation cannot provide an important improvement in the voltage profile during the first stress period.

    “Therefore, flexibility activation cannot provide an important improvement in the voltage profile.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationreasoning
    § C. Real-time flexibility activations · p. 6

    The active power flexibility that the system operator can manage in real-time strongly depends on user preferences and distribution system operator actions.

    “As described in the Introduction, the active power flexibility that the system operator can manage in real-time strongly depends on user preferences and DSO actions.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisecitation
    § I. INTRODUCTION · p. 1

    Flexibility and operational scheduling in power systems require innovative approaches to address temporal and spatial power flow imbalances.

    “As a result, flexibility and operational scheduling in power systems require innovative approaches to address temporal and spatial power flow imbalances [2].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [2] [2] F. Gonzalez Venegas, M. Petit, and Y. Perez, 'Active integration of electric vehicles into distribution grids: Barriers and frameworks for flexibility services,' Renewable and Sustainable Energy Reviews , 2021. - source

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given
    § II. FLEXIBILITY IN EV CHARGING · p. 2

    The time-dependent energy availability parameter, initially provided during day-ahead planning, is dynamically altered by the operator's actions in real-time.

    “This time-dependent parameter, initially provided during day-ahead planning, is dynamically altered by the operator's actions in real-time.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductnone given
    § Optimal Operation of Electric Vehicles to Enhance the Flexibility Provision in Active Distribution Grids · p. 1

    The presented framework employs a non-linear optimal power flow model that ensures compliance with network constraints and accommodates electric vehicle user preferences.

    “The presented framework employs a non-linear optimal power flow model that ensures compliance with network constraints and accommodates EV user preferences.”
    Quote in the paperSubstantial claim

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

    Premisecitation
    § II. FLEXIBILITY IN EV CHARGING · p. 2

    Contracts granting distribution system operators control over the electric vehicle charging procedure can hinder electric vehicle mobility needs, potentially meeting lower and higher user acceptance limits.

    “Such contracts grant DSOs control over the EV charging procedure, which can hinder EV mobility needs, potentially meeting lower and higher user acceptance limits [2].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [2] [2] F. Gonzalez Venegas, M. Petit, and Y. Perez, 'Active integration of electric vehicles into distribution grids: Barriers and frameworks for flexibility services,' Renewable and Sustainable Energy Reviews , 2021. - source
26 of 26

  • The authors state this as an assumption.

    The photovoltaic generation profile is the same across the households due to their geographic proximity, but scaled according to the installed photovoltaic capacity.

    “Due to the geographic proximity of the households, we assume that the PV generation profile is the same (shown in Fig. 4) but scaled according to the installed PV capacity.”

  • The authors state this as an assumption.

    Electric vehicle charging is unidirectional, with discharging prohibited, in this study.

    “In this work, a unidirectional (charging) scheme is considered due to the limitations of EV converters to operate in bidirectional power flow and the degradation effect of discharging in the battery system.”

  • The paper relies on this without support.

    In spring, the Cyprus system has the lowest inertia, thus requiring large amounts of flexibility.

    “Moreover, in spring, the Cyprus system has the lowest inertia, thus requiring large amounts of flexibility.”
3 of 3

Cites

The publisher hasn’t deposited this paper’s reference list.

Research works printed but not linked: 1

  1. [15][15] P. Sokrati and P. Charalampou, 'The impacts of evs in cyprus distribution system,' CUT Thesis , September 2021. -

Cited by

Sorted by citations

Authors
Panagi, S., Therapontos, P., Spanias, C., & Aristidou, P.
Affiliations
  • Electricity Authority of Cyprus (Cyprus) (CY)
  • Cyprus University of Technology (CY)
ORCID
Venue
2025 IEEE Kiel PowerTech
Publisher
IEEE
Published
2025-06-29
Pages
1-6
DOI
10.1109/powertech59965.2025.11180664
OpenAlex
W4414940953
Semantic Scholar
fad2f231e3cd92d64f3ea539f9a1687683fc5e8c
Cited by
0
References
0
FWCI
0.00
Type
conference paper
Language
en
Open access
closed
Licence
Funders
Horizon Europe
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
electric vehicles, electric vehicle charging, active distribution networks, flexibility services, day-ahead scheduling, optimal power flow, distribution network operation

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