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Ollas, P., Thiringer, T., Persson, M. & Markusson, C. (2023). Battery loss prediction using various loss models: A case study for a residential building. Journal of Energy Storage, 70, Article ID 108048.
Open this publication in new window or tab >>Battery loss prediction using various loss models: A case study for a residential building
2023 (English)In: Journal of Energy Storage, ISSN 2352-152X, E-ISSN 2352-1538, Vol. 70, article id 108048Article in journal (Refereed) Published
Abstract [en]

This work compares and quantifies the annual losses for three battery system loss representations in a case study for a residential building with solar photovoltaic (PV). Two loss representations consider the varying operating conditions and use the measured performance of battery power electronic converters (PECs) but differ in using either a constant or current-dependent internal battery cell resistance. The third representation is load-independent and uses a (fixed) round trip efficiency. The work uses sub-hourly measurements of the load and PV profiles and includes the results from varying PV and battery size combinations. The results reveal an inadequacy of using a constant battery internal resistance and quantify the annual loss discrepancy to −38.6%, compared to a case with current-dependent internal resistance. The results also show the flaw of modelling the battery system’s efficiency with a fixed round trip efficiency, with loss discrepancy variation between −5 to 17% depending on the scenario. Furthermore, the necessity of accounting for the cell’s loss is highlighted, and its dependence on converter loading is quantified.

Keywords
Battery energy storage system, Lithium-ion batteries, Solar photovoltaic system, Battery performance, Applied research
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:ri:diva-65662 (URN)10.1016/j.est.2023.108048 (DOI)
Funder
Swedish Energy Agency, 43276-1Swedish Energy Agency, 47273-1Swedish Energy Agency
Note

Funded by the Swedish Energy Agency (’’Energimyndigheten’’) through grant numbers: 43276-1 and 47273-1.

Available from: 2023-07-12 Created: 2023-07-12 Last updated: 2023-08-28Bibliographically approved
Ollas, P., Thiringer, T., Persson, M. & Markusson, C. (2023). Energy Loss Savings Using Direct Current Distribution in a Residential Building with Solar Photovoltaic and Battery Storage. Energies, 16(3), Article ID 1131.
Open this publication in new window or tab >>Energy Loss Savings Using Direct Current Distribution in a Residential Building with Solar Photovoltaic and Battery Storage
2023 (English)In: Energies, E-ISSN 1996-1073, Vol. 16, no 3, article id 1131Article in journal (Refereed) Published
Abstract [en]

This work presents a comparison of alternating current (AC) and direct current (DC) distribution systems for a residential building equipped with solar photovoltaic (PV) generation and battery storage. Using measured PV and load data from a residential building in Sweden, the study evaluated the annual losses, PV utilization, and energy savings of the two topologies. The analysis considered the load-dependent efficiency characteristics of power electronic converters (PECs) and battery storage to account for variations in operating conditions. The results show that DC distribution, coupled with PV generation and battery storage, offered significant loss savings due to lower conversion losses than the AC case. Assuming fixed efficiency for conversion gave a 34% yearly loss discrepancy compared with the case of implementing load-dependent losses. The results also highlight the effect on annual system losses of adding PV and battery storage of varying sizes. A yearly loss reduction of 15.8% was achieved with DC operation for the studied residential building when adding PV and battery storage. Additionally, the analysis of daily and seasonal variations in performance revealed under what circumstances DC could outperform AC and how the magnitude of the savings could vary with time. © 2023 by the authors.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
battery storage, building energy system, direct current, energy savings, power electronic converter, solar photovoltaic, Digital storage, Electric batteries, Electric impedance measurement, Electric power distribution, Energy dissipation, Housing, Power converters, Power electronics, Solar concentrators, Solar power generation, Alternating current, Building energy systems, Direct current distributions, Direct-current, Energy-savings, Power electronics converters, Residential building, Solar photovoltaics, Energy conservation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-64102 (URN)10.3390/en16031131 (DOI)2-s2.0-85147846467 (Scopus ID)
Note

 Correspondence Address: Ollas P, RISE, Sweden; email: patrik.ollas@ri.se; Funding details: Energimyndigheten, 43276–1, 50986–1; Funding text 1: The Swedish Energy Agency funded this research through the national project “From photovoltaic generation to end-users with minimum losses—a full-scale demonstration” (2018–2020, grant number 43276–1) and the national project “Flexibility and energy efficiency in buildings with PV and EV charging” (2020–2023, grant number 50986–1).

Available from: 2023-02-28 Created: 2023-02-28 Last updated: 2023-08-28Bibliographically approved
Björnsson, L.-H., Edvall, M., Persson, M., Strandberg, T., Emmanouilidis, D., Envik, C., . . . Svedlund, J. (2023). Laddinfrastruktur och frekvensreglering: en fallstudie.
Open this publication in new window or tab >>Laddinfrastruktur och frekvensreglering: en fallstudie
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2023 (Swedish)Report (Other academic)
Abstract [sv]

För att elnätet ska fungera måste frekvensen hållas inom snäva gränser och därför handlar Svenska Kraftnät upp olika typer av stödtjänster för frekvensreglering. De senaste åren har kostnaderna för dessa tjänster ökat kraftigt, bland annat till följd av en allt högre andel intermittent elproduktion. Behoven är prognostiserade att öka ytterligare under de kommande åren. Detta har skapat ett ökat intresse för batterier och deras möjligheter att stödja elnätet. Men batterier och tillhörande kraftelektronik är kostsamt. Samtidigt finns en stor och alltjämt växande batterikapacitet i landets elbilar och med hjälp av dubbelriktad laddning, så kallad vehicle-to-grid öppnas nya möjligheter att komma åt denna potential för att på ett mer resurseffektivt sätt balansera elnätet. Projektets övergripande mål har varit att utreda hur standardisering kan användas för att påskynda och öka användandet av elbilar som resurs för flexibilitetstjänster till elnätet. Bland annat har en fallstudie genomförts av Axess Logistics anläggning i Malmö hamn och möjligheterna för att deras långtidsparkerade elbilar ska kunna leverera frekvensreglering till elnätet har studerats. Resultaten visar på att studerade standarder i stort inte utgör ett direkt hinder för användandet av elbilar för frekvensreglering men att förändringar av exempelvis ISO15118 skulle kunna öka möjligheterna att använda elbilar för att leverera frekvensreglering. Till exempel genom införande av krav på mätnoggrannhet på aktiv effekt, förkortning av tillåtna svarstider, krav på lokal frekvensmätning med god noggrannhet. För långtidsparkerade bilar vore det framförallt värdefullt att arbeta fram, och i standard beskriva, en funktion där elbilens BMS kan uppmanas av EVSE att hålla batteriet i ett tillstånd där det kan användas för att snabbt svara på en begäran om i-/urladdning. Detta så att elbilen kan vara förberedd för frekvensreglering även om den för stunden inte aktivt laddar eller matar effekt till elnätet. Detta en åtgärd som skulle kunna ha stor positiv påverkan på möjligheterna för långtidsparkerade elbilar att leverera frekvensreglering. Exemplifierande användarcykler för långtidsparkerade bilar har studerats för FCR-N och FCR-D. Resultaten visar att den förväntade cyklingen skiljer stort mellan dessa olika frekvensregleringstjänster och antyder att valet av frekvensregleringstjänst behöver studeras utifrån både förväntad ekonomi och eventuellt batterislitage. Överslagsräkningar på eventuella intäkter från deltagande i frekvensreglering har genomförts och de preliminära resultaten visar att investering av dyrare laddinfrastruktur som klarar Vehicle-to-Grid skulle kunna återbetalas inom ett år med 2022 års nivåer av ersättning för frekvensreglering. I en framtid där nya elbilar antas ha stöd för Vehicle-to-Grid har potentialen för att använda långtidsparkerade elbilar på logistikanläggningar till frekvensreglering preliminärt bedömts ligga mellan 110 och 165 MW för svenska förhållanden. Detta motsvarar ca 5-8% av den nordiska FCR-marknaden. På sikt kan också långtidsparkerade bilar hos återförsäljare, flygplatser med mera att utgöra en betydande potential.

Publisher
p. 37
Series
RISE Rapport ; 2023:23
National Category
Energy Engineering
Identifiers
urn:nbn:se:ri:diva-64116 (URN)978-91-89757-68-4 (ISBN)
Available from: 2023-03-01 Created: 2023-03-01 Last updated: 2024-05-21Bibliographically approved
Hamon, C. & Persson, M. (2023). Wind power participation in frequency regulation: a profitability assessment for Sweden.
Open this publication in new window or tab >>Wind power participation in frequency regulation: a profitability assessment for Sweden
2023 (English)Report (Other academic)
Abstract [en]

In this report, a framework was developed to assess the profits from participating in the different ancillary services for frequency regulation in Sweden. The framework considers forecasting errors on both production and prices, market clearing times and technical requirements of the difference ancillary services. The framework was applied to evaluate potential profits for a real wind power plant of 2 MW in SE3 in 2020 and 2021. The economic analysis points out to aFRR down as the most profitable market today with additional revenue of as much as 35% compared to day-ahead only in case of perfect production forecasts, and as much as 22 % with consideration of standard production forecast errors. It is also shown that developing bidding strategies based on price forecasting to act on several ancillary service market may increase the revenues by up to 70% compared to day-ahead only. Future work in the topic includes evaluating the profits in other price areas and evaluating different production and price forecast methodologies and their impact on the profits.

Series
RISE Rapport ; 2022:42
Keywords
Wind power, frequency regulation, ancillary services markets, FFR, FCRN, FCR-D, mFRR, aFRR, profitability assessment
National Category
Energy Systems
Identifiers
urn:nbn:se:ri:diva-64365 (URN)978-91-89561-80-9 (ISBN)
Available from: 2023-04-19 Created: 2023-04-19 Last updated: 2023-05-25Bibliographically approved
Chamorro, H. R., Orjuela-Cañón, A. D., Ganger, D., Persson, M., Gonzalez-Longatt, F., Alvarado-Barrios, L., . . . Martinez, W. (2021). Data-driven trajectory prediction of grid power frequency based on neural models. Electronics, 10(2), Article ID 151.
Open this publication in new window or tab >>Data-driven trajectory prediction of grid power frequency based on neural models
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2021 (English)In: Electronics, E-ISSN 2079-9292, Vol. 10, no 2, article id 151Article in journal (Refereed) Published
Abstract [en]

Frequency in power systems is a real-time information that shows the balance between generation and demand. Good system frequency observation is vital for system security and pro-tection. This paper analyses the system frequency response following disturbances and proposes a data-driven approach for predicting it by using machine learning techniques like Nonlinear Autoregressive (NAR) Neural Networks (NN) and Long Short Term Memory (LSTM) networks from simulated and measured Phasor Measurement Unit (PMU) data. The proposed method uses a horizon-window that reconstructs the frequency input time-series data in order to predict the frequency features such as Nadir. Simulated scenarios are based on the gradual inertia reduction by including non-synchronous generation into the Nordic 32 test system, whereas the PMU collected data is taken from different locations in the Nordic Power System (NPS). Several horizon-windows are experimented in order to observe an adequate margin of prediction. Scenarios considering noisy signals are also evaluated in order to provide a robustness index of predictability. Results show the proper performance of the method and the adequate level of prediction based on the Root Mean Squared Error (RMSE) index. © 2021 by the authors.

Place, publisher, year, edition, pages
MDPI AG, 2021
Keywords
Deep learning, Frequency response, Low-inertia power systems, Machine learning, Nadir estimation, Non-synchronous generation, Primary frequency control, Wind power
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-52020 (URN)10.3390/electronics10020151 (DOI)2-s2.0-85099418991 (Scopus ID)
Note

Funding details: 350202; Funding text 1: Funding: This work was supported by by the Laboratorio de Simulación Hardware-in-the-loop para Sistemas Ciberfísicos (LaSSiC). Código: 350202.

Available from: 2021-01-26 Created: 2021-01-26 Last updated: 2023-05-25Bibliographically approved
Hillberg, E., Pihl, H., Persson, M., Weihs, E., Csőre, M., Tóth, Á., . . . Samuelsson, O. (2020). D1.1 Overview of need-owners and their needs: ANM4L, Januari 2020.
Open this publication in new window or tab >>D1.1 Overview of need-owners and their needs: ANM4L, Januari 2020
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2020 (English)Report (Other academic)
Publisher
p. 15
National Category
Business Administration
Identifiers
urn:nbn:se:ri:diva-58767 (URN)
Note

This project has received funding in the framework of the joint programming initiative ERA-Net Smart Energy Systems, with support from the European Union’s Horizon 2020 research and innovation programme. 

Available from: 2022-03-02 Created: 2022-03-02 Last updated: 2023-05-25Bibliographically approved
Weihs, E., Persson, M. & Chen, P. (2020). Frequency quality in the nordic system 2040. In: 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe): . Paper presented at 10th IEEE PES Innovative Smart Grid Technologies Europe, ISGT-Europe 2020, 26 October 2020 through 28 October 2020 (pp. 809-813). IEEE Computer Society
Open this publication in new window or tab >>Frequency quality in the nordic system 2040
2020 (English)In: 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe), IEEE Computer Society , 2020, p. 809-813Conference paper, Published paper (Refereed)
Abstract [en]

This paper proposes a method to estimate the total system kinetic energy and the corresponding frequency quality in the Nordic power system in 2040, based on different scenarios from the TSO utilizing estimated production data. The inertia estimation showed a lowered kinetic energy from an average of 223 GWs in 2019 to 175 GWs for 2040. In this paper an improved grid inverse is proposed to model the frequency control dynamics, where the frequency variation outside the normal band 50±0.1 Hz for 2040 was estimated. The number of events for the hour evaluated increased from 0.4% in 2019 to 1.1-5.0% in 2040 depending on distinct weather years, with an average of 2.8%. This indicates that the events outside the normal frequency band increase considerably for lower inertia conditions, suggesting a worsened frequency quality for 2040. 

Place, publisher, year, edition, pages
IEEE Computer Society, 2020
Keywords
Frequency quality, Low inertia power system, Electric power transmission networks, Kinetics, Smart power grids, Frequency variation, Nordic Systems, Normal band, Production data, Kinetic energy
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-51204 (URN)10.1109/ISGT-Europe47291.2020.9248961 (DOI)2-s2.0-85097330279 (Scopus ID)9781728171005 (ISBN)
Conference
10th IEEE PES Innovative Smart Grid Technologies Europe, ISGT-Europe 2020, 26 October 2020 through 28 October 2020
Available from: 2021-01-11 Created: 2021-01-11 Last updated: 2023-05-25Bibliographically approved
Chamorro, H., Orjuela-Canon, A., Ganger, D., Persson, M., Gonzalez-Longatt, F., Sood, V. & Martinez, W. (2020). Nadir Frequency Estimation in Low-Inertia Power Systems. In: IEEE International Symposium on Industrial Electronics: . Paper presented at 29th IEEE International Symposium on Industrial Electronics, ISIE 2020, 17 June 2020 through 19 June 2020 (pp. 918-922). Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>Nadir Frequency Estimation in Low-Inertia Power Systems
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2020 (English)In: IEEE International Symposium on Industrial Electronics, Institute of Electrical and Electronics Engineers Inc. , 2020, p. 918-922Conference paper, Published paper (Refereed)
Abstract [en]

Increasing amounts of non-synchronous generation in power grids are bringing reductions in system inertia. In a grid with extremely low inertia, the estimation of frequency indicators such as the frequency nadir can be used to feed into predictive system controls that would avoid nuisances such as triggering system protection systems, avoiding needless blackouts. In this paper, the timing of a frequency nadir is predicted using a Nonlinear Auto-Regressive (NAR) model based on an Artificial Neural Network (ANN). The estimation method is tested under a gradual inertia reduction in order to observe the adaptability of the method, under various prediction horizons. 

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2020
Keywords
Artificial Neural Networks, Frequency Response, Low-Inertia Power Systems, Nadir Estimation, Non-synchronous Generation, Primary Frequency Control, Wind Power, Electric power transmission networks, Industrial electronics, Auto-regressive, Estimation methods, Frequency nadirs, Model-based OPC, Prediction horizon, Predictive systems, System inertia, Triggering systems, Frequency estimation
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-47688 (URN)10.1109/ISIE45063.2020.9152296 (DOI)2-s2.0-85089520512 (Scopus ID)9781728156354 (ISBN)
Conference
29th IEEE International Symposium on Industrial Electronics, ISIE 2020, 17 June 2020 through 19 June 2020
Available from: 2020-09-01 Created: 2020-09-01 Last updated: 2023-05-25Bibliographically approved
Persson, M. & Lindskog, A. (2019). Detection and localization of non-technical losses in distribution systems with future smart meters. In: 2019 IEEE Milan PowerTech, PowerTech 2019: . Paper presented at 2019 IEEE Milan PowerTech, PowerTech 2019, 23 June 2019 through 27 June 2019. Institute of Electrical and Electronics Engineers Inc.
Open this publication in new window or tab >>Detection and localization of non-technical losses in distribution systems with future smart meters
2019 (English)In: 2019 IEEE Milan PowerTech, PowerTech 2019, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper, Published paper (Refereed)
Abstract [en]

In terms of efficiency, 54 out of 159 Swedish DSOs have higher distribution losses than 4% on an annual basis. If these 54 had made improvements in their power grids and reached an energy loss of 4%, this would mean a reduction of 143 GWh/year overall. Assuming a cost of 5 cent/ kWh this would equivalent to approximately 7.2 million EUR/year. This paper evaluates two different distribution systems, a method for detection of non-technical losses(NTL) and the impact of the detection method on time delays and resolution issues. Furthermore, three different methods for localization is evaluated and their usability discussed, evaluated and tools presented. All three methods prove able to localize NTL at the bus of connection in the cases presented in the paper. 

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2019
Keywords
Power distribution, Power system analysis computing, Smart grids, Electric power transmission networks, Energy dissipation, Detection and localization, Detection methods, Different distributions, Distribution systems, Non-technical loss, Power distributions, Power system analysis, Smart grid, Smart power grids
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-39978 (URN)10.1109/PTC.2019.8810893 (DOI)2-s2.0-85072310852 (Scopus ID)9781538647226 (ISBN)
Conference
2019 IEEE Milan PowerTech, PowerTech 2019, 23 June 2019 through 27 June 2019
Note

Funding details: Swedish Insitute, SI; Funding details: RISE; Funding text 1: ACKNOWLEDGMENT The funding from EnergiForsk through the program of Smart Grids (Smarta Elnät) is greatly acknowledged. This article was partly taken from a report in Swedish (see [8]) for EnergiForsk co-written by the first author, Dr. Claes Sandels and Senior Engineer Andreas Nilsson at Research Institutes of Sweden (RISE). In this report where added values of DSO feedback and AI-methods are presented.

Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2023-05-25Bibliographically approved
Hillberg, E., Zegers, A., Herndler, B., Wong, S., Pompee, J., Bourmaud, J.-Y., . . . Beccuti, G. (2019). Flexibility needs in the future power system.
Open this publication in new window or tab >>Flexibility needs in the future power system
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2019 (English)Report (Other academic)
Abstract [en]

Power system flexibility relates to the ability of the power system to manage changes. Solutions providing advances in flexibility are of utmost importance for the future power system. Development and deployment of innovative technologies, communication and monitoring possibilities, as well as increased interaction and information exchange, are enablers to provide holistic flexibility solutions. Furthermore, development of new methods for market design and analysis, as well as methods and procedures related to system planning and operation, will be required to utilise available flexibility to provide most value to society. However, flexibility is not a unified term and is lacking a commonly accepted definition. Several definitions of flexibility have been suggested, some of which restrict the definition of flexibility to relate to changes in supply and demand while others do not put this limitation. The flexibility term is used as an umbrella covering various needs and aspects in the power system. This situation makes it highly complex to discuss flexibility in the power system and craves for differentiation to enhance clarity. In this report, the solution has been to differentiate the flexibility term on needs, and to categorise flexibility needs in four categories:

 Flexibility for Power: - Need Description: Short term equilibrium between power supply and power demand, a system wide requirement for maintaining the frequency stability. - Main Rationale: Increased amount of intermittent, weather dependent, power supply in the generation mix. - Activation Timescale: Fractions of a second up to an hour.

 Flexibility for Energy: - Need Description: Medium to long term equilibrium between energy supply and energy demand, a system wide requirement for demand scenarios over time. - Main Rationale: Decreased amount of fuel storage-based energy supply in the generation mix.  - Activation Timescale: Hours to several years.

 Flexibility for Transfer Capacity: - Need Description: Short to medium term ability to transfer power between supply and demand, where local or regional limitations may cause bottlenecks resulting in congestion costs. - Main Rationale: Increased utilisation levels, with increased peak demands and increased peak supply. - Activation Timescale: Minutes to several hours.

 Flexibility for Voltage: - Need Description: Short term ability to keep the bus voltages within predefined limits, a local and regional requirement. - Main Rationale: Increased amount of distributed power generation in the distribution systems, resulting in bi-directional power flows and increased variance of operating scenarios. - Activation Timescale: Seconds to tens of minutes.

Here, flexibility needs are considered from over-all system perspectives (stability, frequency and energy supply) and from more local perspectives (transfer capacities, voltage and power quality). With flexibility support considered for both operation and planning of the power system, it is required in a timescale from fractions of a second (e.g. stability and frequency support) to minutes and hours (e.g. thermal loadings and generation dispatch) to months and years (e.g. planning for seasonal adequacy and planning of new investments).

Publisher
p. 47
National Category
Engineering and Technology
Identifiers
urn:nbn:se:ri:diva-42449 (URN)
Note

ISGAN Disscussion paper

Available from: 2020-01-07 Created: 2020-01-07 Last updated: 2023-05-25
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3608-5264

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