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Cited by 51Power Quality and HarmonicsOptimal Power Flow DistributionSmart Grid Energy Management

A Comprehensive Analysis of the Voltage Unbalance Factor in PV and EV Rich Non-Synthetic Low Voltage Distribution Networks

Open access
Antić, Tomislav, Capuder, Tomislav, Bolfek, Martin·2020·Energies
DOI 10.3390/en14010117
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Abstract

With the development of technology and the decrease in prices, power systems are facing a strong growth in the number of end-users with photovoltaics (PVs), battery storages and electric vehicles (EVs). A penetration of low carbon (LC) technologies has an impact not only on the financial aspect, but also on parameters of the power quality (PQ) in the power system. Since most of end-users with renewable energy sources (RES) are connected to a low-voltage (LV) distribution network, there is a high number of single-phase loads and distributed generators (DG) that can cause unwanted effects in LV networks. According to standards, electric energy must be of a certain quality in order to avoid harmful effects on the power system, being both the network or the end-users equipment. One of the PQ parameters is the voltage unbalance. Voltage unbalance occurs in networks with the high share of single-phase loads and generators. Since most loads in households are connected to the only one phase, the voltage unbalance is constantly present in the network, even without LC technologies. Single-phase connected PVs, residential battery storages and EV charging stations can increase voltage unbalance in the system. This paper systematically analyzes a real-world LV network and different stages and shares of connected PVs, residential battery storages and EVs to different phases. The value of the voltage unbalance factor (VUF) is observed for one week in January and August in 10-min intervals. It is shown that connected systems can significantly increase the VUF and potentially cause negative impact on the equipment and the power system as a whole. In turn we analyze a three-phase connection of these new LC technologies and demonstrate how in all analyzed cases PQ values remain within boundaries defined by the EN 50160 and the IEC 61000-3-13.

AI snapshot

Written from the paper’s full text.

TL;DR

This paper analyzes voltage unbalance factor (VUF) in a real Croatian low-voltage distribution network with increasing shares of single-phase PVs, residential batteries, and EV chargers. It finds that single-phase connections can push VUF above the 2% limit for large portions of the week, while balanced three-phase connection keeps VUF within EN 50160 and IEC 61000-3-13 boundaries.

Key findings

  • In Case 1 (PV only), unallowed VUF >2% occurs in more than 20% of 10-min intervals in January and just under 40% in August at the lowest PV penetration, rising above 40% at higher penetration under Scenario 1 (all PVs on phase L1). Initial and three-phase Scenario 3 cases show no problem, with VUF <2% in more than 95% of 10-min intervals.
  • In Case 2 (PV + EV), VUF >2% can occur in more than 60% of 10-min intervals (Scenario 1, Share 4, August), and even in Scenario 2 (random phase) unallowed VUF can occur in almost 50% of the observed week (Share 3 and Share 4, August); extreme VUF values go beyond 80%.
  • In Case 3 (PV + battery Method 1 + EV), maximum VUF does not exceed 60%, compared with almost 80% in Case 2, but the frequency of VUF >2% is higher than in Case 2; August, Scenario 1, Share 4 shows unallowed VUF in more than 80% of weekly 10-min intervals.
  • In Case 4 (PV + market-driven battery Method 2 + EV), the paper calls this the worst analyzed case: VUF >2% occurs in more than 80% of 10-min intervals in August for Scenario 1, Shares 2–4, and around 85% in the worst case. Scenario 1 VUF values are more than twice those in Scenario 2; maximum VUF is just under 25% for Share 1 and passes 70% for Share 4, while Scenario 2 VUF does not exceed 10%.

Methods

  • The study models a real Croatian LV network using GIS data: an MV feeder, MV node, 10/0.4 kV 630 kVA MV/LV transformer, 120 LV nodes, and 118 LV overhead lines and underground cables with total length 5.86 km and average length 0.05 km. Load profiles are generated with Load Profile Generator, PV profiles come from rooftop measurements, and simulations cover 13–19 January 2020 and 1–7 August 2020 in 10-min intervals.
  • Four connection scenarios are tested: all LC technologies on phase L1, random phase per node, and balanced three-phase connection. Four cases are tested: PV only; PV + EV; PV + battery (Method 1, self-sufficiency) + EV; and PV + battery (Method 2, day-ahead market optimization) + EV. Each case is run at 20%, 40%, 60%, and 80% LC penetration, totaling 128 weekly 10-min simulations.
  • Asymmetrical load flow calculations use NEPLAN V558. VUF is calculated as the ratio of negative-sequence to positive-sequence voltage, and the General Summation Law from IEC 61000-3-13 is applied with α = 1.4. Battery optimization either minimizes deviation between consumption and production (Method 1) or minimizes day-ahead market cost (Method 2); EVs are modeled as Nissan Leaf vehicles charging between 17:00 and 06:00 at up to 3.6 kW.

Limitations

  • The paper states that real-time measurements were not publicly available, so the load profile was created with Load Profile Generator; PV profiles came from rooftop measurements. It also states that results can be observed as a worst-case scenario and that further analyses on voltage magnitude are not in the paper’s focus.
  • The paper assumes all end-users have the same Nissan Leaf EV and the same charging behavior, with battery state of charge set to zero at the first and last time periods. These modeling assumptions, evident from the text, may limit generalization to other EV types, driving patterns, or battery operating strategies.
  • The analysis is based on one real Croatian LV network and does not report measurement validation or uncertainty/sensitivity analysis; the text makes evident that conclusions may depend on the specific network, load profiles, and scenario definitions.

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

Integrity signals

Registry

Crossref · 10.3390/en14010117

Cites

36 of 36 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

9 of 27 cited sources checked · 1 supported · 2 flagged · accuracy not yet measured

  • Premisecitation

    In case of a 15% voltage unbalance, the network losses increase by 15%.

    “In case of a 15% unbalance, the network losses increase by 15%.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [37] Ochoa, L.F., Ciric, R.M., Padilha-Feltrin, A., and Harrison, G.P. (2005, January 22–26). Evaluation of distribution system losses due to load unbalance. Proceedings of the 15th Power Systems Computation Conference 2005, Liege, Belgium.

      Section 4.1 reports that, for the LV-29 network, a 15% load unbalance increased losses by 4.1% compared with balanced loads—not 15%. The paper evaluates load unbalance, not a specified 15% voltage unbalance. (LLM, conf=0.90)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    A high share of PVs in the MV or LV network can cause voltages with magnitude higher than boundaries set by the grid code or standards.

    “A high share of PVs in the MV or LV network can cause voltages with the magnitude that is higher than boundaries set by the grid code or the standards.”
    Quote in the paperSubstantial claim3 of 3 sources checked
    • cites [6] Ochoa, 2019, OPF-Based CVR Operation in PV-Rich MV-LV Distribution Networks, IEEE Trans. Power Syst. source

      The supplied passages and additional passages retrieved from the indexed copy contain bibliographic information and keywords, but no discussion of PV penetration causing voltages to exceed grid-code or standards limits. Searches for overvoltage, voltage rise, and statutory limits did not find a passage addressing the claim. (LLM, conf=0.72)

      Experimental — accuracy not yet measured
    • cites [7] Hashemi, 2017, Methods and strategies for overvoltage prevention in low voltage distribution systems with PV, IET Renew. Power Gener. source

      The indexed copy provides a title and bibliographic material (section “1 Finished,” no page), but no paper-body passage addressing the claim. Searches for high PV penetration, MV networks, and grid-code or standards-based voltage limits returned no eligible passage; the available abstract cannot be used as evidence under the stated rules. (LLM, conf=0.70)

      Experimental — accuracy not yet measured
    • cites [8] Watson, 2016, Impact of solar photovoltaics on the low-voltage distribution network in New Zealand, IET Gener. Transm. Distrib. source

      Section 3.2 reports that overvoltage in urban LV networks increases sharply above 10–15% solar PV penetration, with some voltages exceeding the statutory 1.06 p.u. limit. The study models LV networks; the cited passages do not establish the same effect for PV penetration in MV networks. Page numbers are unavailable in our copy. (LLM, conf=0.84)

      Experimental — accuracy not yet measured
  • Premisecitation

    Analysis of the LV distribution network in [37] shows that despite demand being maintained, total losses increased by 4.1% for a 15% unbalance compared to a fully balanced system.

    “Analysis of the LV distribution network made in [37] shows that despite demand being maintained, total losses calculated by the explicit four-wire approach increased by 4.1% for a 15% unbalance compared to a fully balanced system.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [37] Ochoa, L.F., Ciric, R.M., Padilha-Feltrin, A., and Harrison, G.P. (2005, January 22–26). Evaluation of distribution system losses due to load unbalance. Proceedings of the 15th Power Systems Computation Conference 2005, Liege, Belgium.
  • Premisecitation

    Three-phase connection of the PV system helps reducing voltage unbalance.

    “It is shown that three-phase connection of the PV system helps reducing voltage unbalance.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [29] Rezvani, F., Mozafari, B., and Faghihi, F. (2015). Power quality analysis for Photovoltaic system considering unbalanced voltage. Indian J. Sci. Technol., 8. source

      The Abstract says the simulated three-phase PV system reduces voltage imbalance at a nearby bus in an unbalanced network. It does not establish that a three-phase connection alone produces that reduction: the studied system includes MPPT and a DVR, and the Abstract says its compensating effect depends on proximity to the load. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Premisecitation

    The existing literature analyzes EV charging only from the perspective of relieving voltage and congestion problems, not because of the impact single-phase charging stations have on voltage unbalance.

    “The existing literature is analyzing the EV charging only from the perspective of relieving voltage and congestion problems [11,12] and not because of the impact that single-phase charging stations have on the voltage unbalance.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [11] Ochoa, 2018, How electric vehicles and the grid work together: Lessons learned from one of the largest electric vehicle trials in the world, IEEE Power Energy Mag. source
    • cites [12] Srivastava, A., Steen, D., Tuan, L.A., and Carlson, O. (2019, January 23–27). A congestion forecast framework for distribution systems with high penetration of PVs and PEVs. Proceedings of the IEEE Milan PowerTech, Milan, Italy. source

      The Introduction and Conclusions (page not available in our copy) show that this paper examines EV charging in relation to voltage deviation and network congestion. It forecasts those problems rather than studying how charging relieves them, and it does not establish that the existing literature *only* takes this perspective or address the impact of single-phase charging stations on voltage unbalance. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • Classified as probably not a substantial claim. 8
  • May combine two claims. 27
  • The quote only partly states this claim. 2

  • Classified as probably not a substantial claim.

    Premisecitation

    The impact of PVs on VUF in the LV urban distribution reference network does not present a problem, since VUF does not exceed the 2-3% boundaries.

    “The impact of PVs on the VUF in the LV urban distribution reference network does not present the problem, since the VUF does not exceed the 2-3% boundaries [30].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [30] Lucas, A. (2018). Single-phase PV power injection limit due to voltage unbalances applied to an urban reference network using real-time simulation. Appl. Sci., 8. source

      In Results and Discussion (page unavailable), the paper reports that voltage-unbalance limits of 2% and 3% are reached at PV injections of 3.5 kW and 4.6 kW, respectively, and adopts the conservative 2% limit for further analysis. It therefore treats PV-induced unbalance as a constraint, contrary to the unqualified claim that it presents no problem. Section 2.2 also says the study uses a magnitude-based measure rather than VUF. (LLM, conf=0.82)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured

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

    Findingreasoning

    In the worst-case scenario, maximum power of the entire LV network is 671 kW.

    “in the worst-case scenario maximum power of the entire LV network is 671 kW.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In Case 3, using battery storage (Method 1) can decrease maximum VUF values in the LV network compared to Case 2; maximum VUF in Case 3 does not exceed 60%, while values as high as almost 80% occur in Case 2.

    “Comparing values to those in Case 2, when end-user did not have the battery, shows that using the battery storage could decrease maximum values of the VUF in the LV network, e.g., maximum values of the VUF in Case 3 do not exceed 60%, while values as high as almost 80% occur in Case 2.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • The quote only partly states this claim.

    Findingnone given

    In Case 4, with growth of LC share, maximum VUF values in scenarios with LC connected to the same phase grow faster.

    “Also, with the growth of the share of LC technologies, maximum values of the VUF in scenarios when LC technologies are connected to the same phase in each node grow faster.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    In Case 2, Share 4, Scenario 1, most VUF values are not larger than 40%, but extreme values go beyond 80% in January and August.

    “For example, results of Case 2, Share 4 in January and August show that for Scenario 1 most of the VUF values are not larger than 40%, but extreme values go even beyond 80%.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In Case 4, the most time in which VUF is higher than 2% occurs in August, when in Scenario 1, Share 2-Share 4, VUF exceeds the limit in more than 80% of 10-min intervals during the observed week.

    “The analysis show that the most time in which the VUF is higher than the 2% limitations occurs in August, when in Scenario 1, Share 2-Share 4, VUF thresholds the limit in more than 80% of 10 min intervals during the observed week.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingnone given

    In Case 3, despite battery storage not significantly impacting or even decreasing VUF values compared to Case 2, the frequency of unallowed VUF occurrence is higher in Case 3 than in Case 2.

    “Despite the fact that the addition of the battery storage does not significantly impact on the VUF value or even decreases them (compared to Case 2), frequency of the unallowed VUF occurrence is higher in Case 3 than in above mentioned Case 2.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    In Case 4, maximum VUF for Share 1 is little less than 25%, and for Share 4 it passes 70%.

    “Maximum value for Share 1 is little less than 25% and for Share 4, maximum value passes 70%.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    Three-phase connection of LC technologies reduces the value of VUF and the frequency of VUF exceeding the limit.

    “A three-phase connection of LC technologies does not only reduce the value of the VUF and the frequency of the occurrence of the VUF thresholding the limit”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    In Case 4, a three-phase connection does not produce thresholding VUF values in alarming frequency.

    “Results of Scenario 3 shows that a three-phase connection does not produce thresholding VUF values in alarming frequency.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    In the Initial scenario and Scenario 3, VUF is less than 2% in more than 95% of 10-min intervals, satisfying IEC 61000-3-13.

    “In Initial scenario and Scenario 3 there is no problem with the voltage unbalance, i.e., the value of the VUF is less than 2% in more than 95% of 10 min intervals, which satisfies the standard IEC 61000-3-13 [28].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] International Electrotechnical Commission (IEC) IEC 61000-3-13 2015.

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

  • May combine two claims.

    Findingown data

    In Case 2, changing the phase on which PVs are connected (Scenario 2) benefits the system, i.e., VUF above the threshold occurs less often than when PVs are connected to the same phase in each node.

    “Results of Scenario 2 show that changing the phase on which PVs are connected benefits the system, i.e., the occurrence of VUF above the threshold value is not as often as in scenarios when PVs are connected to the same phase in each node.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    As the percentage of installed PVs, batteries, and EVs grows, the VUF value and the frequency of VUF exceeding limitations increase.

    “As the percentage of installed PVs grows (but also that of other technologies such as batteries and EVs), the value of VUF and the frequency of VUF overstepping the limitations is further increasing.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Scenario 1, in which all LC technologies are connected to the same phase at each node, presents the worst-case scenario, with almost all observed parameters worse than in other scenarios.

    “Even though it is highly unlikely that all end-users are connected to the same phase, it presents the worst-case scenario when almost all observed parameters are worse than in other scenarios.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    In Case 1, Scenario 3 results are similar to the Initial scenario, and problematic VUF values occur less often than in other scenarios.

    “In that scenario results are similar as ones in the Initial, and the occurrence of problematic values of the voltage unbalance is not as often as in other scenarios.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In Case 4, with 80% LC technologies connected, undervoltage occurs when consumption is highest and there is no PV production, while overvoltage occurs when consumption is lower, PV production is high, and battery storage is discharging.

    “It can be noticed that in certain instances and scenarios the undervoltage occurs in time periods when the consumption is the highest, and there is no production from the PVs, while in certain instances and scenarios the overvoltage occurs in time periods when the consumption is lower, the PVs' production is high, and the battery storage is discharging.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    In Scenario 1, unallowed voltage unbalance occurs in more than 20% in January and in little less than 40% in August when the penetration of PVs is lowest.

    “In Scenario 1 unallowed voltage unbalance occurs in more than 20% in January and in little less than 40% in August when the penetration of PVs is lowest and larger than”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In Case 2, for Share 4, the interquartile range in January and August is similar, but there are more outlier values in August.

    “Even though the interquartile range in January and August for share of 80% (Share 4) is similar for both months, there is a lot more outlier values in August.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Findingown data

    In Scenario 1, unallowed voltage unbalance occurs in more than 20% of intervals in January and in little less than 40% in August when PV penetration is lowest, and larger than 40% when penetration is higher.

    “In Scenario 1 unallowed voltage unbalance occurs in more than 20% in January and in little less than 40% in August when the penetration of PVs is lowest and larger than 40% when penetration is higher.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In the Initial scenario and Scenario 3, the VUF is less than 2% in more than 95% of 10-min intervals, satisfying IEC 61000-3-13.

    “In Initial scenario and Scenario 3 there is no problem with the voltage unbalance, i.e., the value of the VUF is less than 2% in more than 95% of 10 min intervals, which satisfies the standard IEC 61000-3-13 [28].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] International Electrotechnical Commission (IEC) IEC 61000-3-13 2015.

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

  • May combine two claims.

    Findingown data

    In Case 4, changing the method that determines charging and discharging cycles (from Method 1 to Method 2) does not significantly impact the occurrence of VUF values exceeding the limit; in Scenario 1, the occurrence is almost as frequent as in Case 3.

    “The comparison with Case 3 shows that changing the method which determines charging and discharging cycles does not significantly impact on the occasions related to the voltage unbalance, i.e., the occurrence of the VUF values thresholding the limit is almost as frequent as in Case 4 in Scenario 1.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.

  • May combine two claims.

    Interpretationreasoning

    The method proposed in this paper does not affect the profit and comfort of the end-user because they are not asked to participate in voltage unbalance reduction.

    “The method proposed in this paper does not affect the profit and the comfort of the end-user, since they are not asked to participate in the voltage unbalance reduction.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    When the phase of connection is adequately selected, the hybrid system of PVs and ESS could possibly help reduce VUF and avoid voltage unbalance.

    “When the phase of the connection is adequately selected, the hybrid system of PVs and ESS could possibly help the reduction of the VUF and the avoidance of the voltage unbalance [32].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [32] Chua, 2012, Voltage Unbalance Mitigation in Low Voltage Distribution Networks with Photovoltaic Systems, J. Electron. Sci. Technol.

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

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

    Interpretationnone given

    The worst-case scenario (all three phases maximum loaded in single-phase end-user nodes and all three-phase connected end-users consuming maximum power) is not realistic.

    “It needs to be noted that this is not a realistic case.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The negative sequence component voltage causes negative sequence current, which does not convey energy but contributes to energy loss and reduces capacity of distribution lines.

    “The negative sequence component voltage causes the negative sequence current occurrence which does not convey the energy, but it contributes to energy loss and reduces the capacity of distribution lines [31].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [31] Plummer, I. (2011). Asymmetry in Distribution Systems: Causes, Harmful Effects and Remedies. [Master’s Thesis, Louisiana State University]. source

  • May combine two claims.

    Study design and conductnone given

    Both conditions for using the General summation law are satisfied in the tested network.

    “Since both conditions are satisfied in the tested network, General summation law was used to determine if the VUF in the LV network exceeds boundaries.”
    Quote in the paperSubstantial claim

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

    Premisenone given

    The elements of the LV distribution network that cause voltage unbalance are loads, PVs, battery storages and EV charging stations.

    “The elements of the LV distribution network that are causing the voltage unbalance are loads, PVs, battery storages and EV charging stations.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    A three-phase connection of PVs has a lower probability of negative impacts compared to a single-phase connection, where VUF values are significantly higher.

    “A three-phase connection of PVs is the possibility that should be encouraged by DSOs because the probability of negative impacts is seldom compared to a single-phase connection, when values are significantly higher, which leads to an unsatisfying performance of some of the equipment and of the distribution network as a whole.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Voltage unbalance has a negative impact on equipment and the LV network.

  • May combine two claims.

    Interpretationreasoning

    In Case 3, VUF values that exceed limitations do not occur often, reducing negative impact.

    “Values of the VUF that are thresholding limitations do not occur often and therefore reduce the negative impact.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: All end-users have the same Nissan Leaf Battery Electric Vehicle.
    • The authors state this as an assumption: End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.
    • The authors state this as an assumption: EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.
    • The authors state this as an assumption: The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.
    • Rests on an assumption: The EV charging curve is price-based determined and is the same for all end-users.
    • Rests on an assumption: The logic of EV charging is the same for January and for August.
    • Rests on an assumption: Voltage unbalance has a negative impact on equipment and the LV network.

  • May combine two claims.

    Interpretationown data

    The results, although showing a concerning trend from the DSO perspective, could be observed as the worst-case scenario.

    “Even though results show the concerning trend from the perspective of the DSO, they could be observed as the worst-case scenario.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    General summation law is adopted for distribution networks with a large number of unbalanced installations (e.g., greater than 10) or when unbalance changes randomly with time.

    “General summation law is adopted for the distribution network with a large number of unbalanced installations (e.g., a number greater than 10 is considered), or when the unbalance changes randomly with time [28].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] International Electrotechnical Commission (IEC) IEC 61000-3-13 2015.

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

  • May combine two claims.

    Interpretationreasoning

    With the trend shown in the paper, the performance of heat pumps will be reduced and losses will be significantly higher.

    “With trend shown in this paper, the performance of heat pumps will be reduced, and losses will be significantly higher.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Voltage unbalance has an impact on the performance of end-user equipment, mostly on asynchronous machines.
    • Rests on an assumption: The electrification of heating will lead to growth in the number of heat pumps, which are basically asynchronous machines.

  • Classified as probably not a substantial claim.

    Interpretationown data

    The results in the paper support the recommendation to have all new LC devices connected as balanced three-phase ones.

    “The results in the paper support such a recommendation”
    Quote in the paperSubstantial claim

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

    Interpretationreasoning

    The method proposed in this paper enables system operators to reduce costs without complex operations and investment in the equipment.

    “The method proposed in this paper enables system operators to reduce costs without complex operations and investment in the equipment.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The annual financial value of 1% network losses in Croatia is around 6,000,000 €.
    • Rests on an assumption: The majority of operational actions proposed in the available literature to reduce network voltage unbalances require complex models and control algorithms on the side of both end-users and the distribution system operator.
34 of 34

  • The authors state this as an assumption.

    The installed power of each phase at a node is the same.

    “It is implied that the installed power of each phase at the node is same, e.g., node LV54 presents a three-phase house and the maximum power of each phase is 2 kW.”

  • The authors state this as an assumption.

    At each node, one phase is loaded with 100%, one with 85% and one with 70% of the load profile curve.

    “Therefore, it is assumed that at each node one phase is loaded with 100%, one with 85% and one with 70% of the load profile curve shown in Figures A1 and A2 in Appendix A.”

  • The paper relies on this without support.

    Loads in nodes with big consumers such as hospitals are symmetrically three-phase connected, i.e., the value of the load in each phase is the same.

    “Loads in those nodes are symmetrically, three-phase connected to the network, i.e., the value of the load in each phase is the same.”

  • The authors state this as an assumption.

    The average price of electricity is 50 €/MWh.

    “If we assume that the average price of electricity is 50 €/MWh, the increase of 1% means that annual financial losses are increased for around 6,000,000 €.”

  • The paper relies on this without support.

    The existing literature does not analyze different operational nodes and their impact on voltage unbalance.

    “Further, the existing literature body does not analyze different operational nodes and their impact on the voltage unbalance.”

  • The paper relies on this without support.

    The increase of total losses of 1% in Croatian networks is equal to around 120 GWh.

    “The increase of total losses of 1% in Croatian networks is equal to around 120 GWh.”

  • The paper relies on this without support.

    The situation in the non-synthetic LV network could be different from reference networks.

    “However, the situation in the non-synthetic LV network could be different and there is need to analyze the impact of more LC technologies than only PV systems in cases that could potentially appear.”

  • The authors state this as an assumption.

    All end-users have the same Nissan Leaf Battery Electric Vehicle.

    “It is supposed that all end-users have the same Nissan Leaf Battery Electric Vehicle [48].”

  • The authors state this as an assumption.

    End-users are at home between 5:00 P.M. and 6:00 A.M. and can charge their EVs during these hours.

    “It is supposed that in these hours, end-users are at home, and it is possible for them to charge their EVs.”

  • The authors state this as an assumption.

    EVs are only charged in the afternoon hours after the end-user arrives at their households, i.e., during the night.

    “The assumption made in the model is that EVs are only charged in the afternoon hours after the end-user arrive at their households, i.e., during the night.”

  • The authors state this as an assumption.

    The behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.

    “It is assumed that the behavior of all end-users is the same, meaning that the constraints defining charging periods are the same for every end-user with the EV.”

  • The paper relies on this without support.

    The EV charging curve is price-based determined and is the same for all end-users.

    “The EV charging curve is price-based determined and it is same for all end-users.”

  • The paper relies on this without support.

    The logic of EV charging is the same for January and for August.

    “The logic of EV charging is the same for January and for August.”

  • The paper relies on this without support.

    Voltage unbalance has a negative impact on equipment and the LV network.

    “Knowing the negative impact that the unbalance can have on the equipment and the LV network, end-users should be encouraged to symmetrically distribute PVs and EV charging stations to all three phases, i.e., to install PVs and charging stations three-phase.”

  • The paper relies on this without support.

    All end-users with installed PVs and residential battery storages could potentially have EV charging stations.

    “All end-users with installed PVs and residential battery storages, could potentially have EV charging stations.”

  • The paper relies on this without support.

    The DSO will definitely change its operational practices in case of large LC integration, either by reinforcing the network or by incorporating provision of flexibility services.

    “Since the DSO will definitely change it operational practices in case of large LC integration, either by reinforcing the network or by incorporating provision of flexibility services, further analyses on voltage magnitude are not in the focus of the paper.”

  • The paper relies on this without support.

    Voltage unbalance has an impact on the performance of end-user equipment, mostly on asynchronous machines.

    “The voltage unbalance has an impact on the performance of the end-user's equipment, mostly on asynchronous machines”

  • The paper relies on this without support.

    The number of asynchronous machines in the LV network is not so large.

    “the number of asynchronous machines in the LV network is not so large”

  • The paper relies on this without support.

    The electrification of heating will lead to growth in the number of heat pumps, which are basically asynchronous machines.

    “with the process of the electrification of the heating, there will be growth in a number of heat pumps, which are basically asynchronous machines.”

  • The paper relies on this without support.

    The annual financial value of 1% network losses in Croatia is around 6,000,000 €.

    “Since the annual financial value of 1% network losses in Croatia is around 6,000,000 €”

  • The paper relies on this without support.

    The majority of operational actions proposed in the available literature to reduce network voltage unbalances require complex models and control algorithms on the side of both end-users and the distribution system operator.

    “The available literature proposed a number of operational actions that can be suggested in order to reduce the network voltage unbalances, however majority of them requires complex models and control algorithms on the side of both end-users and the distribution system operator.”

  • The paper relies on this without support.

    Many end-users in the Croatian LV distribution network are three-phase, meaning they have access to all three phases.

    “a lot of end-users in the Croatian LV distribution network are three-phase, meaning that they have access to all three-phases.”

  • The paper relies on this without support.

    It is highly unlikely that all end-users are connected to the same phase.

    “Even though it is highly unlikely that all end-users are connected to the same phase”

  • The paper relies on this without support.

    The system operator would like to reduce network losses and not increase them.

    “the system operator would like to reduce network losses and not increase them.”
24 of 24

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Reference [28] is called IEC 61000-3-13 but lists a different work

    Minor

    The paper attributes its VUF limit to IEC 61000-3-13 as reference [28], whereas entry 28 in its own reference list is an article on photovoltaic power quality.

  • Loss increase for 15% unbalance changes from 4.1% to 15%

    Minor

    The earlier account gives a 4.1% loss increase for 15% unbalance relative to a balanced system; the conclusion gives 15% for the same unbalance. The latter value supports the paper's financial-loss discussion.

  • Case 4 is mislabeled as the self-sufficient case

    Minor

    The Figure 8 discussion calls Case 4 the self-sufficient comparator to market-driven operation. Elsewhere, the paper identifies Case 3 as self-sufficient and Case 4 as market-driven.

  • Reported simulation total does not match the defined combinations

    Minor

    The three defined connection scenarios, four cases, four penetration shares and two weeks yield 96 weekly simulations, not 128. Counting the initial scenario once for each week would yield 98.

    Reported 128 · recomputed 96

4 of 4

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Schlabbach, J., and Gross, A. (2016, January 4–8). Harmonic current emission of photovoltaic inverters. Proceedings of the 5th International Conference on European Electricity Market, Leuven, Belgium.
  2. Petrou, K., Liu, M.Z., Procopiou, A.T., Ochoa, L.F., Theunissen, J., and Harding, J. (2020, January 22–23). Managing residential prosumers using operating envelopes: An Australian case study. Proceedings of the CIRED Workshop, Berlin, Germany.

Cited by

Sorted by citations

Related

Authors
Antić, T., Capuder, T., & Bolfek, M.
Affiliations
  • University of Zagreb (HR)
  • HEP DSO Ltd. Elektra Koprivnica, 48000 Koprivnica, Croatia
Corresponding author
Antić, Tomislav
ORCID
Venue
Energies
Publisher
MDPI AG
Published
2020-12-28
Volume
14
Issue
1
Pages
117
ISSN
1996-1073 (ISSN-L)
DOI
10.3390/en14010117
OpenAlex
W3114739922
Cited by
51
References
34
Citations by year
2026: 6 · 2025: 9 · 2024: 10 · 2023: 10 · 2022: 12 · 2021: 4
FWCI
2.19
Type
journal article
Language
en
Open access
Licence
Locations
  • Energies (publishedVersion, cc-by)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Topics
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Power Quality and Harmonics
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Optimal Power Flow Distribution
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Smart Grid Energy Management
Keywords
voltage unbalance factor, low-voltage distribution networks, photovoltaics, electric vehicles, residential battery storage, power quality, single-phase loads, distributed generation, electric vehicle charging stations, EN 50160, low-carbon technologies

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-28.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-28.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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