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Publications (10 of 352) Show all publications
Herre, L., Matusevičius, T., Olauson, J. & Söder, L. (2019). Exploring Wind Power Prognosis Data on Nord Pool: The Case of Sweden and Denmark. IET Renewable Power Generation
Open this publication in new window or tab >>Exploring Wind Power Prognosis Data on Nord Pool: The Case of Sweden and Denmark
2019 (English)In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, ISSN 1752-1416Article in journal (Refereed) Published
Abstract [en]

A good understanding of forecast errors is imperative for greater penetration of wind power, as it can facilitate planning and operation tasks. Oftentimes, public data is used for system studies without questioning or verifying its origin. In this paper, we propose a methodology to verify public data with the example of wind power prognosis published by Nord Pool. We focus on Swedish data and identify a significant bias that increases over the forecast horizon. In order to explore the origin of this bias, we first compare against Danish forecast and then describe the underlying structure behind the submission processes of this data. Based on the balance settlement structure, we reveal that Swedish "wind power prognoses" on Nord Pool are in fact rather wind production plans than technical forecasts. We conclude with the recommendation for improved communication and transparency with respect to terminology of public data on Nord Pool. We stress the importance for the research community to check publicly available input data before further use. Furthermore, the root-mean-square error and the spatio-temporal correlation between the errors in the bidding areas at different horizons is presented. Even with this compromised data, a stronger correlation is identified in neighbouring areas.

Keywords
wind power forecasts, forecast anaylsis, vindkraftspognoser, analys av vindkraftsprognoser
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Energy Systems
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-241639 (URN)10.1049/iet-rpg.2018.5086 (DOI)000462942900006 ()2-s2.0-85063728250 (Scopus ID)
Note

QC 20190124

Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-04-29Bibliographically approved
Crosara, A., Tomasson, E. & Söder, L. (2019). Generation Adequacy in the Nordic and Baltic Region: Case Studies from 2020 to 2050: Flex4RES Project Report. Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Generation Adequacy in the Nordic and Baltic Region: Case Studies from 2020 to 2050: Flex4RES Project Report
2019 (English)Report (Other academic)
Abstract [en]

Generation adequacy is a concern in today's electricity market where intermittent renewable energy sources are rapidly becoming a greater share of the generation mix. This study focuses on the Nordic and Baltic power system that is comprised of the system areas of the Nord Pool spot market. Sequential Monte Carlo Simulation is applied to assess the generation adequacy of this multi-area system for several future case studies, based on scenarios defined within the Nordic Flex4RES project. The report gives insights into the characteristics of these adequacy problems that the system could face in a more sustainable future, quantifies their magnitude and presents their characteristics. Finally, a solution based on the demand flexibility of residential electric heating is discussed, as a way to counter capacity deficit problems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. p. 33
Keywords
Generation Adequacy, Reliability, Electricity Market, Monte Carlo Simulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-254940 (URN)
Projects
Flex4RES
Note

QC 20190724

Available from: 2019-07-09 Created: 2019-07-09 Last updated: 2019-07-26Bibliographically approved
Divshali, P. H. & Söder, L. (2019). Improving PV Dynamic Hosting Capacity Using Adaptive Controller for STATCOMs. IEEE transactions on energy conversion, 34(1), 415-425
Open this publication in new window or tab >>Improving PV Dynamic Hosting Capacity Using Adaptive Controller for STATCOMs
2019 (English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 34, no 1, p. 415-425Article in journal (Refereed) Published
Abstract [en]

High penetrations of renewable energy sources (RES) in distribution grids lead to new challenges in voltage regulation. These challenges are not just limited to the steady-state voltage rise, but they are extended to rapid voltage changes due to wind speed variations and moving clouds, casting shadows on photovoltaic panels. According to EN50160 in low-voltage (LV) grids, the steady-state voltage should not exceed 1.1 pu (static characteristic), and rapid voltage changes should be kept less than 0.05 pu (dynamic characteristic). These two characteristics may limit the maximum amount of RES that can be installed in LV grids, called, respectively, the static hosting capacity (SHC) and dynamic hosting capacity (DHC). Although existing research just evaluated SHC in distribution grids, high-penetrated RES grids can be faced with such large voltage changes, which cause a smaller DHC than the SHC. This paper studies both SHC and DHC in distribution grids and proposes an adaptive controller for static synchronous compensators to regulate the steady-state and dynamic voltage while avoiding the unnecessary increase in the reactive power. The simulation results in some German distribution grids show considerable effects of the proposed adaptive controller on improving both SHC and DHC.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019
Keywords
Distribution grids, dynamic voltage regulation, hosting capacity, reactive power, renewable energy sources (RESs)
National Category
Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-247822 (URN)10.1109/TEC.2018.2873057 (DOI)000460332600041 ()
Note

QC 20190327

Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-06-11Bibliographically approved
Nycander, E., Söder, L., Eriksson, R. & Hamon, C. (2019). Minimising wind power curtailments using OPF considering voltage stability. The Journal of Engineering (18), 5064-5068
Open this publication in new window or tab >>Minimising wind power curtailments using OPF considering voltage stability
2019 (English)In: The Journal of Engineering, ISSN 1872-3284, E-ISSN 2051-3305, no 18, p. 5064-5068Article in journal (Refereed) Published
Abstract [en]

As the amount of wind power in power systems has increased, it has become necessary to curtail wind power in some high-penetration situations. In order to assess the need for curtailment arising from voltage stability considerations the authors develop a security constrained optimal power flow (SCOPF) for minimising the expected curtailment. The authors find that with a very high wind penetration and wind farms operating at unity power factor curtailment becomes necessary to satisfy voltage limits. In this case, the optimal solution in the studied system is to curtail at a single bus rather than curtailing by a smaller amount at several buses. However, allowing for reactive power production from wind farms reduces the need for curtailments.

Place, publisher, year, edition, pages
INST ENGINEERING TECHNOLOGY-IET, 2019
Keywords
load flow, wind power plants, wind power, reactive power, power system security, power factor, minimising wind power curtailments, OPF considering voltage stability, power systems, high-penetration situations, voltage stability considerations, optimal power flow, expected curtailment, high wind penetration, wind farms, unity power factor curtailment, voltage limits, reactive power production
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-260206 (URN)10.1049/joe.2018.9371 (DOI)000482590000074 ()
Note

QC 20190930

Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-09-30Bibliographically approved
Söder, L. (2019). The Costs of Decarbonisation: System Costs with High Shares of Nuclear and Renewables -Impact from updated cost assumptions. Stockholm
Open this publication in new window or tab >>The Costs of Decarbonisation: System Costs with High Shares of Nuclear and Renewables -Impact from updated cost assumptions
2019 (English)Report (Other academic)
Abstract [en]

The aim of this study is to perform a sensitivity analysis concerning impact from assumed investment costs of the NEA/OECD report “The Costs of Decarbonisation: System Costs with High Shares of Nuclear and Renewables” from 2019. A study of this type, i.e. technical-economic analysis, has a set-up as: [input data] => [simulation method]  => [output results]. The output results then completely depend on used input data and simulation method. The question is then what happens with other types of data assumptions.

The aim is to study the changes from assumed investment and O&M costs, since the main ones used in the report are not reflective of neither actual, nor forecasted costs.

We will start the analysis by trying to duplicate the results of the original NEA/OECD report in order to ensure our methodology is consistent with theirs. This is a challenge as their data and methodology is semi-transparent and not clearly defined. However, the central data, as total cost, can be replicated. Here in Chapter 3 we summarize their data and results. In Chapter 4 we then try to duplicate their methodology and results and compare it to the NEA/OECD results, in particular the total costs for their different cases. The more up to date and forecasted investment and O&M costs data is presented in Chapter 5.  Chapter 6 gives the results of applying these data sets and compares and contrasts it with the NEA/OECD results. References are found in chapter 7. The summary of the findings is found in chapter 2.

All calculations are done within Excel, and the program can be downloaded.

Place, publisher, year, edition, pages
Stockholm: , 2019. p. 28
National Category
Engineering and Technology
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-251689 (URN)
Note

QC 20190520

Available from: 2019-05-19 Created: 2019-05-19 Last updated: 2019-05-20Bibliographically approved
Dabar, O. A., Awaleh, M. O., Kirk-Davidoff, D., Olauson, J., Söder, L. & Awaleh, S. I. (2019). Wind resource assessment and economic analysis for electricity generation in three locations of the Republic of Djibouti. Energy, 185, 884-894
Open this publication in new window or tab >>Wind resource assessment and economic analysis for electricity generation in three locations of the Republic of Djibouti
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2019 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 185, p. 884-894Article in journal (Refereed) Published
Abstract [en]

In the Republic of Djibouti, due to increasing electricity demands, the government has planned to increase power supply by using renewable resources such as geothermal, solar and wind energy. This work presents the first wind resource assessment in the Republic of Djibouti using measured wind speed data for the period of three years by meteorological stations at eight locations. The results confirmed that three of the eight locations (i.e. GaliMa-aba, Ghoubbet and Bada Wein) have the best resource, with mean annual wind speeds of more than 6.0 m/s. Wind simulations using NCEP-CFSR and ERA5 models reanalysis shows that the seasonal variations are stable between different years and are broadly consistent with the observed wind speed. The feasibility of three wind farms with total capacity of 275 MW at GaliMa-aba, Ghoubbet and Bada Wein is examined. Using the WindPRO program and two commercial wind turbines in according to IEC 61400-1 design criteria, the electricity generation were technically assessed. These wind farms can produce 1073 GWh of electricity per year, approximately equal to Djibouti's expected average annual electrical demand in 2030. The economic evaluation using the present value cost (PVC) method estimate that the generation cost per kWh at these locations varies from 7.03 US.$ cent/kWh to 9.67 US.$ cent/kWh. Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Djibouti, Wind energy, WindPRO, NCEP-CFSR, ERA5 reanalysis, Cost analysis
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-260994 (URN)10.1016/j.energy.2019.07.107 (DOI)000484869400072 ()2-s2.0-85069710284 (Scopus ID)
Note

QC 20191010

Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2019-10-10Bibliographically approved
Nilsson, M., Söder, L., Olauson, J., Eriksson, R., Nordström, L. & Ericsson, G. N. (2018). A Machine Learning Method Creating Network Models Based on Measurements. In: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC): . Paper presented at 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC). IEEE
Open this publication in new window or tab >>A Machine Learning Method Creating Network Models Based on Measurements
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2018 (English)In: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), IEEE , 2018Conference paper, Published paper (Refereed)
Abstract [en]

Network models are essential to perform power flow analyses. In this paper a supervised regression method creating simplified network models using measurements is presented. It is an iterative method creating a network model by minimizing the difference between measurements and obtained power flow using measured net-exchanges for each node. The method is tested in a case study for the Nordic Synchronous Area considering each bidding zone as a node. The simplified network model is created using a training set and is validated using various validation methods. The obtained reactances are not correct in absolute terms; however results indicate that the obtained power flows using the created network model are accurate enough for several different applications.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Machine learning, Nordic Power System, power flow analyses, simplified network model
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-238162 (URN)10.23919/PSCC.2018.8442822 (DOI)000447282400121 ()2-s2.0-85054003071 (Scopus ID)
Conference
2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC)
Note

QC 20181107

Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2018-11-07Bibliographically approved
Söder, L., Lund, P. D., Koduvere, H., Bolkesjø, T. F., Rossebø, G. H., Rosenlund-Soysal, E., . . . Blumberga, D. (2018). A review of demand side flexibility potential in Northern Europe. Renewable & sustainable energy reviews, 91, 654-664
Open this publication in new window or tab >>A review of demand side flexibility potential in Northern Europe
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2018 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 91, p. 654-664Article, review/survey (Refereed) Published
Abstract [en]

The number of regional and national power systems with a high share of wind and solar power in the world is quickly increasing. The background for this development is improved technology, decreasing costs, and increased concern regarding environmental problems of competing technologies such as fossil fuels. For the future there are large possibilities for increasing the renewable electricity share. However, variable renewable power production has to be balanced. Demand side flexibility offers an interesting approach to the balancing issues. The aim of this paper is to compare flexibility potentials and how they were estimated in seven Northern European countries in order to compare general challenges and results as well as the connection between used method and results. The total flexibility is estimated to 12–23 GW in a system with a total peak load of 77 GW.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Balancing, Demand side management, Flexibility, Solar power, Wind power
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-227514 (URN)10.1016/j.rser.2018.03.104 (DOI)000434919600045 ()2-s2.0-85045627732 (Scopus ID)
Note

QC 20180516

Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-07-02Bibliographically approved
Ren, G., Wan, J., Liu, J., Yu, D. & Söder, L. (2018). Analysis of wind power intermittency based on historical wind power data. Energy, 150, 482-492
Open this publication in new window or tab >>Analysis of wind power intermittency based on historical wind power data
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2018 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 150, p. 482-492Article in journal (Refereed) Published
Abstract [en]

As wind power provides an increasingly larger share of electricity supply, the challenges caused by wind power intermittency have become more and more prominent. A better understanding of wind power intermittency would contribute to mitigate it effectively. In the present study, the definition of wind power intermittency is given firstly. Based on the definition, wind power intermittency is quantified by duty ratio of wind power ramp (DRWPR). This index provides system operators quantitative insights into wind power intermittency. Furthermore, some characteristics of wind power intermittency can be extracted by the index, such as the differences between wind speed intermittency and wind power intermittency, the differences of wind power intermittency between different scales and so on. The wind power intermittency of a Chinese wind farm is studied in detail based on the proposed index and historical data.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Characteristics, Duty ratio, Forecasting, Intermittency, Ramp event, wind power
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-227592 (URN)10.1016/j.energy.2018.02.142 (DOI)000431748400038 ()2-s2.0-85042848108 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-05-31Bibliographically approved
Stankovic, S. & Söder, L. (2018). Analytical Estimation of Reactive Power Capability of a Radial Distribution System. IEEE Transactions on Power Systems
Open this publication in new window or tab >>Analytical Estimation of Reactive Power Capability of a Radial Distribution System
2018 (English)In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679Article in journal (Refereed) Published
Abstract [en]

The control of reactive power exchange between grids of different voltage levels has always been a concern for system operators. With production moving from the transmission to the distribution level, its importance increases. This paper proposes a novel approach to estimate reactive power capability of the grid as a whole. A linearized analytical model for an estimation of available reactive power exchange at the interface between two grids has been developed. The maximum estimation error for the scenarios we tested was only 2%. The model gives the relation between important grid parameters and the supported reactive power. The conclusions drawn from the model are confirmed on typical Swedish distribution network with scattered wind power and small industry consumers. Common scenarios in development of distribution grids are applied to show relevant parameters influence. One studied scenario is replacement of overhead lines with cables. It is shown that this particular change enhances the reactive power capability of the grid which is directly seen from the analytical analysis without running any optimal power flow. The analytical model proposed in this paper gives fundamental understanding of the reactive power capability of radial distribution grids.

Keywords
distribution grid, reactive power capability, reactive power management, voltage control, wind power
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-231395 (URN)
Projects
Volatile
Note

QC 20180627

Available from: 2018-06-27 Created: 2018-06-27 Last updated: 2018-10-19Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8189-2420

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