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Enhancing Network OperationalFlexibility for Wind Energy Integration: A Coordinated Optimization Approach Across Generation, Transmission, Storage, and Demands
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.ORCID iD: 0000-0001-5591-7287
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing penetration of wind energy in electricity networks introduces significant variability that challenges operational flexibility.Traditional siloed strategies that address generation, transmission,storage and demand independently often result in local optimal wind energy integration. This issue highlights the need for a holistic and flexible operational framework to maximize wind energy utilization inthe existing networks without major new infrastructure investments.To meet this need, this dissertation proposes a coordinated optimization approach, integrating wind resource assessment, dynamic thermal rating (DTR), energy storage systems (ESS) and demand side management strategies. The approach employs optimization techniques, including two-stage stochastic programming with chance constraints and copula-based correlation modeling, to account for uncertainties in wind availability and energy demand. By optimizing across multiple energy domains (electricity, thermal energy and hydrogen) and leveraging flexibility resources, the proposed framework enhances the grid’s ability to accommodate wind variability while maintaining reliability.The contributions of this work include: first, a planning model for wind farm expansion alongside DTR-based transmission systemis introduced, which minimizes wind curtailment while balances generation investments with grid reliability; second, a dynamic dispatch strategy combining DTR with battery storage is developed to increase wind energy integration while accounting for battery degradation; third, an integrated multi-energy coordination framework ispresented to diverts excess wind power to other energy carriers and engages flexible loads; and finally, a chance-constrained stochastic optimization model is formulated to consider the uncertainties under varying weather and loading conditions.Case studies demonstrate that the coordinated strategy significantly increases wind power utilization and reduces operational costs compared to conventional siloed approaches. These improvements underscore the value of integrated planning and operation in future power systems with high shares of renewables.Overall, this work advances the state of the art in wind energy integration by validating the effectiveness of the holistic approach.It also provides a practical blueprint for system operators and planners to develop more flexible and resilient power grids under high renewable penetration.

Abstract [sv]

Ökad integration av vindkraft i elnäten medför betydande variationer som utmanar nätets operativa flexibilitet. Traditionella isolerade strategier, där produktion, överföring, lagring och efterfrågan hanteras separat, leder ofta till lokalt optimal integration av vindenergi.

Detta understryker behovet av en Holistisk och flexibel operativram för att maximera användningen av vindkraft i befintliga nät utan betydande investeringar i ny infrastruktur.

För att möta detta behov föreslås i denna avhandling en samordnad optimeringsmetod som integrerar vindresursbedömning, dynamic thermal rating (DTR), energilagringssystem (ESS) och strategier förefterfrågestyrning. Metoden använder optimeringstekniker, inklusive tvåstegs stokastisk programmering med sannolikhetsbegränsningar och copula-baserad korrelationsmodellering, för att hantera osäkerheter i vindkraftstillgång och energiefterfrågan. Genom optimering över flera energidomäner (el, värmeenergi och väte) och genom att utnyttja flexibilitetsresurser förbättrar kan det föreslagna ramverket nätets förmåga att hantera vindkraftens variation samtidigt som driftsäkerheten bibehålls. Avhandlingens bidrag inkluderar: För det första introduceras en planeringsmodell för vindkraftsutbyggnad tillsammans med DTR baserade transmissionssystem som minimerar vindkraftens begränsningar samtidigt som balans uppnås mellan investeringskostnader och nätreliabilitet. För det andra utvecklas en dynamisk driftsstrategi som kombinerar DTR med batterilagring för att öka vindenergiintegrationen med hänsyn till batteriers degradering. För det tredje presenteras ett integrerat koordinationsramverk för flera energislag, där överskottsenergi från vindkraft används i andra energiformer och flexibla laster aktiveras. Slutligen formuleras en stokastisk optimeringsmodell med sannolikhetsbegränsningar som beaktar osäkerheter under varierande väder- och belastningsförhållanden. Fallstudier visar att den samordnade strategin avsevärt ökar utnyttjandet av vindkraft och minskar driftkostnaderna jämfört med traditionella isolerade metoder. Dessa förbättringar understryker värdet av integrerad planering och drift för framtida elsystem med hög andel förnybar energi. Sammanfattningsvis bidrar denna forskning till forskningsfronten inom integration av vindkraft genom att validera effektiviteten hos en holistisk strategi. Den ger också praktisk vägledning för systemoperatörer och planerare för att utveckla mer flexibla och resilienta kraftsystem med hög andel förnybar energi.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2025. , p. 110
Series
TRITA-EECS-AVL ; 2025:69
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-363816ISBN: 978-91-8106-314-1 (print)OAI: oai:DiVA.org:kth-363816DiVA, id: diva2:1960078
Public defence
2025-06-12, D2, Lindstedtsvägen 9, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

QC 20250522

Available from: 2025-05-22 Created: 2025-05-22 Last updated: 2025-05-22Bibliographically approved
List of papers
1. A novel integrated optimization method of micrositing and cable routing for offshore wind farms
Open this publication in new window or tab >>A novel integrated optimization method of micrositing and cable routing for offshore wind farms
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2024 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 306, article id 132443Article in journal (Refereed) Published
Abstract [en]

In traditional wind farm planning, the design of wind turbine locations and cable layouts is usually undertaken sequentially. However, this approach may potentially result in suboptimal solutions. While the increased spacing between wind turbines enhances power output by reducing wake losses, it also imposes a negative impact by raising cable costs. Addressing this challenge, we propose a novel multi-objective optimization model that simultaneously considers the micrositing of wind turbines and cable routing. A joint framework of the Non-dominated Sorting Genetic Algorithm II (NSGA-II) and the Mixed-Integer Linear Programming (MILP) is established to optimize the layout of wind turbine locations, points of connection, and cable paths. The results indicate that, compared to the traditional sequential optimization, our integrated optimization exhibits significant economic advantages since improved the balance between micro siting and cable routing. By strategically sacrificing a portion of power generation to reduce cable costs, the overall investment profitability can be remarkably improved, with a maximum gain equivalent to 10.02 % of the cable costs.

Place, publisher, year, edition, pages
Elsevier BV, 2024
Keywords
Cable routing, Micrositing, MILP, Multi-objective, NSGA-II, Power output
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Energy Engineering
Identifiers
urn:nbn:se:kth:diva-351789 (URN)10.1016/j.energy.2024.132443 (DOI)001279343000001 ()2-s2.0-85199310204 (Scopus ID)
Note

QC 20240823

Available from: 2024-08-13 Created: 2024-08-13 Last updated: 2025-05-22Bibliographically approved
2. Sizing Transformer Considering Transformer Thermal Limits and Wind Farm Wake Effect
Open this publication in new window or tab >>Sizing Transformer Considering Transformer Thermal Limits and Wind Farm Wake Effect
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2021 (English)In: 2021 IEEE PES Innovative Smart Grid Technologies - Asia, ISGT Asia 2021, Institute of Electrical and Electronics Engineers (IEEE) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

Compared to the wind farm itself, wind farm transformers are often oversized with regard to their capacity and lifetime. One of the reasons is that power transformers are normally sized at planning stage according to their rated power limits instead of their thermal limits. The thermal limits are usually considered only in operation. In this paper, a new method is proposed to take thermal limits into account and size the wind farm transformer at planning stage based on the expected life of the transformer insulation. An analytical model of wind turbine wakes loss is combined with the transformer thermal model to calculate the expected lifetime of the transformer insulation more accurately. Different from the previous approaches, the proposed method considers both the wake effect and the time-varying ambient temperature. Results show that compared to using the constant temperature and predicted power output without wake loss consideration, the expected lifetime of transformer insulation evaluated after involving these two factors is closer to the result evaluated based on the measured wind power.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2021
Keywords
ambient temperature, transformer size, wake effect, wind power, Electric power system interconnection, Electric utilities, Power transformers, Temperature, Thermal insulation, Wakes, Expected lifetime, Planning stages, Power limit, Thermal limits, Thermal winds, Transformer insulation, Wake loss, Wind farm
National Category
Software Engineering
Identifiers
urn:nbn:se:kth:diva-316264 (URN)10.1109/ISGTASIA49270.2021.9715702 (DOI)000812323700155 ()2-s2.0-85126996864 (Scopus ID)
Conference
2021 IEEE PES Innovative Smart Grid Technologies - Asia (ISGT Asia), Brisbane, Australia, December 5-8, 2021
Note

Part of proceedings: 978-1-6654-3339-6

QC 20220819

Available from: 2022-08-19 Created: 2022-08-19 Last updated: 2025-05-22Bibliographically approved
3. Impact of Turbine Availability and Wake Effect on Transformer Life Expectancy
Open this publication in new window or tab >>Impact of Turbine Availability and Wake Effect on Transformer Life Expectancy
(English)Manuscript (preprint) (Other academic)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-325771 (URN)
Note

QC 20230414

Available from: 2023-04-14 Created: 2023-04-14 Last updated: 2025-05-22Bibliographically approved
4. Maximizing Power Dispatch of Wind-Storage System with Dynamic Thermal Rating Considering Battery Degradation Costs
Open this publication in new window or tab >>Maximizing Power Dispatch of Wind-Storage System with Dynamic Thermal Rating Considering Battery Degradation Costs
2023 (English)In: Proceedings of 2023 IEEE PES Innovative Smart Grid Technologies Europe, ISGT EUROPE 2023, Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper, Published paper (Refereed)
Abstract [en]

In the wind farm expansion stage, installing battery energy storage systems (BESSs) assists in mitigating the time of overloading the connected transmission systems by peak shaving. Applying dynamic thermal rating (DTR) improves the utilization of the transmission systems based on monitoring real-time environmental conditions. DTR and BESS are combined in this paper to maximize power dispatch of an expanded wind farm without expanding the transmission system. The novelty of this paper lies in considering DTR of transformer and degradation cost of the batteries in the proposed optimization framework. Results show that the utilization of DTR and BESS mitigates wind power curtailment and applying DTR reduces degradation costs of the batteries. The findings also indicate the importance of carefully planning the size and control strategy of BESSs in order to minimize operational costs, especially for expanded wind farms and the connected transmission systems applying DTR.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023
Keywords
battery degradation, battery storage, dynamic thermal rating, transformer, wind farm expansion
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-344030 (URN)10.1109/ISGTEUROPE56780.2023.10407543 (DOI)2-s2.0-85185228534 (Scopus ID)
Conference
2023 IEEE PES Innovative Smart Grid Technologies Europe, ISGT EUROPE 2023, Grenoble, France, Oct 23 2023 - Oct 26 2023
Note

QC 20240229

Part of ISBN 979-8-3503-9678-2

Available from: 2024-02-28 Created: 2024-02-28 Last updated: 2025-05-22Bibliographically approved
5. Risk-Averse Coordinated Distribution of Multiple Energy with Dynamic Thermal Rating and Flow via Chance-Constrained Stochastic Programming
Open this publication in new window or tab >>Risk-Averse Coordinated Distribution of Multiple Energy with Dynamic Thermal Rating and Flow via Chance-Constrained Stochastic Programming
(English)In: IEEE Transactions on Sustainable Energy, ISSN 1949-3029, E-ISSN 1949-3037Article in journal (Refereed) Submitted
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-363820 (URN)
Note

QC 20250522

Available from: 2025-05-22 Created: 2025-05-22 Last updated: 2025-05-22Bibliographically approved
6. Temporally Coordinated Operation of Green Multi-Energy Airport Microgrids with Climatic Correlations and Flexible Loads via Decomposed Stochastic Programming
Open this publication in new window or tab >>Temporally Coordinated Operation of Green Multi-Energy Airport Microgrids with Climatic Correlations and Flexible Loads via Decomposed Stochastic Programming
(English)In: IEEE Transactions on Sustainable Energy, ISSN 1949-3029, E-ISSN 1949-3037Article in journal (Refereed) Submitted
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-363821 (URN)
Available from: 2025-05-22 Created: 2025-05-22 Last updated: 2025-05-22Bibliographically approved

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Li, Zhongtian

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