| 1. |
- Bird, Lori, et al.
(författare)
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Wind and solar energy curtailment : A review of international experience
- 2016
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Ingår i: Renewable & sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 65, s. 577-586
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Forskningsöversikt (refereegranskat)abstract
- Greater penetrations of variable renewable generation on some electric grids have resulted in increased levels of curtailment in recent years. Studies of renewable energy grid integration have found that curtailment levels may grow as the penetration of wind and solar energy generation increases. This paper reviews international experience with curtailment of wind and solar energy on bulk power systems in recent years, with a focus on eleven countries in Europe, North America, and Asia. It examines levels of curtailment, the causes of curtailment, curtailment methods and use of market based dispatch, as well as operational, institutional, and other changes that are being made to reduce renewable energy curtailment.
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| 2. |
- Hodge, Bri-Mathias, et al.
(författare)
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Wind Power Forecasting Error Distributions : An International Comparison
- 2012
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Konferensbidrag (refereegranskat)abstract
- Wind power forecasting is essential for greater penetration of wind power into electricity systems. Because no wind forecasting system is perfect, a thorough understanding of the errors that may occur is a critical factor for system operation functions, such as the setting of operating reserve levels. This paper provides an international comparison of the distribution of wind power forecasting errors from operational systems, based on real forecast data. The paper concludes with an assessment of similarities and differences between the errors observed in different locations.
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| 3. |
- Nordström, Henrik, et al.
(författare)
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Strategies for Continuous Balancing in Future Power Systems with High Wind and Solar Shares
- 2023
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 16:14
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Forskningsöversikt (refereegranskat)abstract
- The use of wind power has grown strongly in recent years and is expected to continue to increase in the coming decades. Solar power is also expected to increase significantly. In a power system, a continuous balance is maintained between total production and demand. This balancing is currently mainly managed with conventional power plants, but with larger amounts of wind and solar power, other sources will also be needed. Interesting possibilities include continuous control of wind and solar power, battery storage, electric vehicles, hydrogen production, and other demand resources with flexibility potential. The aim of this article is to describe and compare the different challenges and future possibilities in six systems concerning how to keep a continuous balance in the future with significantly larger amounts of variable renewable power production. A realistic understanding of how these systems plan to handle continuous balancing is central to effectively develop a carbon-dioxide-free electricity system of the future. The systems included in the overview are the Nordic synchronous area, the island of Ireland, the Iberian Peninsula, Texas (ERCOT), the central European system, and Great Britain.
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| 4. |
- Obradovic, Danilo
(författare)
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Coordinated Frequency Control Using DC Interconnections Between AC Systems : Utilizing Fast Frequency Support through HVDC Links and Evaluating the Newly Uncovered Dynamics in Low-Inertia Power Systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transmission system operators are increasingly adopting renewable energy sources in response to the escalating need to reduce environmental pollution. However, renewable energy sources, like wind and solar power, connect to the grid through power electronics, offering no inherent inertia. This reduction in inertia substantially deteriorates the frequency responses during large power disturbances. Frequency Containment Reserves (FCR) are designed to counteract these disturbances and stabilize frequency within a few seconds after an imbalance has occurred. However, in scenarios with low inertia and large power disturbances, relying solely on FCR may prove insufficient to maintain frequency within acceptable limits, risking power system blackouts and severe disruptions. This thesis, therefore, conducts a comprehensive evaluation of fast frequency support in the form of Emergency Power Control (EPC) from High Voltage Direct Current (HVDC) links as a complement to FCR.Unlike prior research, which overlooked the consideration of technical requirements of FCR responses and their significance for EPC evaluation, this thesis fills these gaps. Additionally, previous literature examining EPC has not confirmed a reliable solution for a system of various HVDC links.Various EPC designs are evaluated to reduce frequency deviations and avoid negative interactions. This thesis employs dynamic simulations and, where appropriate, various linear control theories. A spectrum of system models is used, from simplified single-machine equivalents to detailed multi-machine models, aiming to highlight common findings, explain disparities, and capture relevant stability interactions. Particular attention is given to voltage-dependent dynamics, which are often overlooked in frequency control assessments. Moreover, considering EPC's ability to apply large gains, the thesis explores its impact on small-signal stability.The droop frequency-based EPC using local inputs emerges as a key and safe solution for controlling the frequency in the Nordic power system for present and future operations. It is shown that the proposed EPC reduces the frequency deviations when appropriate droop values are chosen. Even more, the research demonstrates stability and cost benefits when efficiently distributing EPC among different HVDC links and coordinating it with the FCR. The simple EPC design allowed for analyzing various dynamic interactions and derivations of strategies for avoiding the ones of a negative nature. Finally, the thesis confirms the overall positive and sustainable role of the proposed EPC.
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| 5. |
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| 6. |
- Söder, Lennart, 1956-, et al.
(författare)
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Comparison of Integration Studies of 30-40 percent Energy Share from Variable Renewable Sources
- 2017
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Ingår i: 16th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Power Plants, Berlin, 2017, article id WIW17-049.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The amount of wind and solar power in the world is quickly increasing. The background for this development is improved technology, decreased costs for the units, and increased concern regarding environmental problems of competing technologies such as fossil fuels. For the future there are large possibilities for increasing shares. However there have been questions raised concerning the challenges of integrating larger shares of variable renewable power such as wind and solar power. Because of this many studies have been performed concerning larger amounts of variable generation for different regions in the world. The aim of this paper is to compare seven of these ones in order to identify general challenges and results as well as the connection between used method and results.
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| 7. |
- Söder, Lennart, 1956-, et al.
(författare)
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Wind Generation in Adequacy Calculations and Capacity Markets in Different Power System Control Zones
- 2018
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Ingår i: 17th International Wind Integration Workshop, Stockholm, 17-19 October 2018.
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Konferensbidrag (refereegranskat)abstract
- Generation capacity adequacy is a major issue in most power systems, but there are many approaches which canbe assessed. Power system planners often define target values for the capacity adequacy, which may be achieved through capacity markets/auctions, capacity reserves, or capacity purchases. Wind power contributes to the generation capacity adequacy of the power system since there is a possibility that wind power will generate in high load situations and thereby decreases the risk of generation capacity deficit compared tothe system without this source. The contribution is probabilistic– as it is with any other source, since nothing is 100% reliable - but the capacity value of wind power is significantly smaller compared to the capacity value of conventional fossil-fueled plants.In this article, an overview of the fundamental challenges inthe regulation of capacity adequacy as well as how wind poweris treated in some selected existing jurisdictions is presented.The jurisdictions that are included are Sweden, Great Britain,France, Ireland, United States (PJM), Finland, Portugal, SpainNorway and Denmark.
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