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Bertling Tjernberg, Lina, ProfessorORCID iD iconorcid.org/0000-0003-4763-9429
Alternative names
Biography [eng]

Her research and teaching are focused on applying mathematics (e.g. statistics, optimization, life cycle assessment) for predicting and modelling reliability, impact of maintenance efforts for various electric power system applications. The research interests include future technologies (e.g. micro grids, battery storage, wind/solar), designs and operation of the power grid including electrified transportations.

Biography [swe]

Forskning och undervisning är inriktad på att tillämpa matematik (t.ex. statistik, optimering, livscykelbedömning) för att förutsäga och modellera tillförlitlighet, påverkan av underhållsinsatser för olika tillämpningar för elkraftsystem. Forskningsintressen inkluderar framtida tekniker (t.ex. mikronät, batterilagring, vind / sol), konstruktion och drift av elnätet inklusive elektrifierade transporter. 

Publications (10 of 134) Show all publications
Rajora, G. L., Sanz-Bobi, M. A., Bertling Tjernberg, L. & Calvo-Bascones, P. (2026). Refining Open-Source Asset Management Tools: AI-Driven Innovations for Enhanced Reliability and Resilience of Power Systems. Technologies, 14(1), Article ID 57.
Open this publication in new window or tab >>Refining Open-Source Asset Management Tools: AI-Driven Innovations for Enhanced Reliability and Resilience of Power Systems
2026 (English)In: Technologies, E-ISSN 2227-7080, Vol. 14, no 1, article id 57Article in journal (Refereed) Published
Abstract [en]

Traditional methods of asset management in electric power systems rely upon fixed schedules and reactive measurements, leading to challenges in the transparent prioritization of maintenance under evolving operating conditions and incomplete data. In this paper, we introduce a new, fully integrated artificial intelligence (AI)-driven approach for enhancing the resilience and reliability of open-source asset management tools to support improved performance and decisions in electric power system operations. This methodology addresses and overcomes several significant challenges, including data heterogeneity, algorithmic limitations, and inflexible decision-making, through a three-module workflow. The data fidelity module provides a domain-aware pipeline for identifying structural (missing) values from explicit missingness using sophisticated imputation methods, including Multiple Imputation Chain Equations (MICE) and Generative Adversarial Network (GAN)-based hybrids. The characterization module employs seven complementary weighting strategies, including PCA, Autoencoder, GA-based optimization, SHAP, Decision-Tree Importance, and Entropy Weighting, to achieve objective feature weight assignment, thereby eliminating the need for subjective manual rules. The optimization module enhanced the action space through multi-objective optimization, balancing reliability maximization and cost minimization. A synthetic dataset of 100 power transformers was used to validate that the MICE achieved better imputation than other methods. The optimized weighting framework successfully categorizes Health Index values into five condition levels, while the multi-objective maintenance policy optimization generates decisions that align with real-world asset management practices. The proposed framework provides the Transmission and Distribution System Operators (TSOs/DSOs) with an adaptable, industry-oriented decision-support workflow system for enhancing reliability, optimizing maintenance expenses, and improving asset management policies for critical power infrastructure.

Place, publisher, year, edition, pages
MDPI AG, 2026
Keywords
asset health assessment, condition monitoring, data-driven insights, machine learning, multi-objective optimization, power system asset management, predictive maintenance
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-376988 (URN)10.3390/technologies14010057 (DOI)001670242700001 ()2-s2.0-105029075523 (Scopus ID)
Note

QC 20260223

Available from: 2026-02-23 Created: 2026-02-23 Last updated: 2026-02-23Bibliographically approved
Cox, D. M., Damasceno, D. R., Hagsten, J., Hellesen, C., Hjelmeland, M., Jurasz, J., . . . Bertling Tjernberg, L. (2026). Strategic capacity expansion planning in hydro-dominated power systems: Insights from the Nordics. Energy, 344, Article ID 139771.
Open this publication in new window or tab >>Strategic capacity expansion planning in hydro-dominated power systems: Insights from the Nordics
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2026 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 344, article id 139771Article in journal (Refereed) Published
Abstract [en]

Conventional capacity expansion planning (CEP) relies on a perfect-foresight planning horizon and linear investment optimisation, which fail to capture the non-linear dynamics of electricity markets. In the Nordics, hydro-related weather variability plays a critical role in maintaining the robustness of the power system. This paper addresses the intra-year perfect-foresight limitation in current CEP models, focusing on hydro-dominated power systems with substantial hydro reservoir capacity, using Sweden's decarbonisation pathway toward 2050 as a case study. Our approach provides a robust long-term CEP framework by leveraging short-term price forecasts to guide storage dispatch decisions. The proposed CEP model has been historically validated and captures the dynamics of seasonal storage hydro reservoirs, achieving deviations of less than €1/MWh in annual average prices across all Swedish bidding zones. A comparative analysis between the proposed and conventional CEP models (cGrid and GenX), together with the Ten-Year Network Development Plan (TYNDP 2024), reveals a broad alignment in capacity expansion and dispatch under an average weather year. However, in a problematic weather year, with correlated low wind output and reduced hydro inflows, significant divergences emerge, with half-year price averages differing by up to ±€40/MWh. These discrepancies are mainly driven by contrasting approaches to hydro reservoir modelling. Notably, the proposed CEP model recommends a 37.5 % increase in firm nuclear capacity to mitigate supply shortages, whereas the conventional CEP suggests a 4.4 % reduction, thereby increasing reliance on weather-dependent resources. These findings underscore the limitations of perfect-foresight CEP in power systems with substantial seasonal storage resources.

Place, publisher, year, edition, pages
Elsevier BV, 2026
Keywords
Extreme weather years, Long-term power system planning, Multiple weather years, Perfect-foresight, Power market modelling, Seasonal storage
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Energy Systems
Identifiers
urn:nbn:se:kth:diva-375469 (URN)10.1016/j.energy.2025.139771 (DOI)2-s2.0-105025784544 (Scopus ID)
Note

QC 20260116

Available from: 2026-01-16 Created: 2026-01-16 Last updated: 2026-01-16Bibliographically approved
Bertling Tjernberg, L. (2026). The EI2525 Electric Power Engineering Project 2025. Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>The EI2525 Electric Power Engineering Project 2025
2026 (English)Report (Other (popular science, discussion, etc.))
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2026. p. 299
Series
TRITA-EECS-RP ; 2026:1
Keywords
electric power engineering, EI2525, project course
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-377070 (URN)
Note

QC 20260223

Available from: 2026-02-20 Created: 2026-02-20 Last updated: 2026-02-23Bibliographically approved
Beyene, Y. B., Worku, G. B. & Bertling Tjernberg, L. (2025). Adaptive Hybrid PSO-Embedded GA for neuroevolutionary training of multilayer perceptron controllers in VSC-based islanded microgrids. Energy and AI, 21, Article ID 100551.
Open this publication in new window or tab >>Adaptive Hybrid PSO-Embedded GA for neuroevolutionary training of multilayer perceptron controllers in VSC-based islanded microgrids
2025 (English)In: Energy and AI, E-ISSN 2666-5468, Vol. 21, article id 100551Article in journal (Refereed) Published
Abstract [en]

This paper introduces a novel hybrid optimization algorithm, Adaptive Hybrid PSO-Embedded GA (AHPEGA), which dynamically adapts to optimization performance by integrating Particle Swarm Optimization (PSO) and Genetic Algorithms (GA). The primary objective is to enhance the neuroevolutionary training of multilayer perceptron-based controllers (MLPCs) through the joint optimization of model parameters and structural hyperparameters. Traditional training methods frequently encounter issues such as premature convergence and limited generalization. AHPEGA addresses these limitations through an adaptive training strategy that dynamically adjusts parameters during the evolutionary process, thereby improving convergence speed and solution quality. By effectively reducing entrapment in local minima and balancing exploration and exploitation, AHPEGA improves the quality of neural controller design. The algorithm's performance is evaluated against conventional optimization methods, demonstrating significant improvements in accuracy, convergence speed, and consistency across multiple runs. The practical applicability of the proposed method is demonstrated through simulation in the context of a VSC-based islanded microgrid (MG), where ensuring reliable and effective control under variable operating conditions is critical. This highlights AHPEGA's capability to optimize intelligent control strategies in MG systems, particularly under dynamic and uncertain conditions, reinforcing its practical value in real-world energy environments.

Place, publisher, year, edition, pages
Elsevier BV, 2025
Keywords
Deep learning model design, Hybrid optimization, Islanded microgrids, Multilayer Perceptron Controllers (MLPCs), Neuroevolutionary training, PSO-embedded GA, Power grid
National Category
Control Engineering
Identifiers
urn:nbn:se:kth:diva-377707 (URN)10.1016/j.egyai.2025.100551 (DOI)001548059600002 ()2-s2.0-105010698170 (Scopus ID)
Note

QC 20260312

Available from: 2026-03-12 Created: 2026-03-12 Last updated: 2026-03-12Bibliographically approved
Rajora, G. L., Sanz-Bobi, M. A., Domingo, C. M. & Bertling Tjernberg, L. (2025). An Open-Source Tool-Box for Asset Management Based on the Asset Condition for the Power System. IEEE Access, 13, 49174-49186
Open this publication in new window or tab >>An Open-Source Tool-Box for Asset Management Based on the Asset Condition for the Power System
2025 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 13, p. 49174-49186Article in journal (Refereed) Published
Abstract [en]

This Study introduces an open-source toolbox for asset management in power systems developed under the European ATTEST project. This paper focuses on presenting an open-source toolbox for Transmission and Distribution System Operators (TSOs and DSOs) to improve the reliability and efficiency of power networks, including a solution to the difficulties faced by the power industry, such as the aging infrastructure and the growing need for renewable energy integration. The toolbox uses predictive analytics and machine learning to evaluate the health of assets, enhance maintenance plans, and guarantee efficient resource distribution. It evaluates the condition of power grid assets through clustering (K-means, SOM) and reinforcement learning (Q-learning), providing actionable insights for improving asset management. This approach allows TSOs and DSOs to adopt proactive maintenance strategies, reducing the risk of failures, minimizing downtime, and extending the lifespan of critical infrastructure. The toolbox provides actionable insights for planning maintenance strategies and optimizing resource allocation. Scalability tests were conducted using a synthetic power grid of 600 transformers alongside real-world data from five European electrical companies. Due to space constraints, only the results from 92 transformers. This research contributes to achieving sustainable power systems and supporting the energy transition by focusing on intelligent asset management.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2025
Keywords
Maintenance, Power systems, Asset management, Power grids, Power transformers, Machine learning, Power system reliability, Europe, Companies, Sustainable development, ATTEST, asset health assessment, condition monitoring, power system asset management, predictive maintenance, reinforcement learning, data-driven insights
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-362789 (URN)10.1109/ACCESS.2025.3551663 (DOI)001449680800012 ()2-s2.0-105001086211 (Scopus ID)
Note

QC 20250428

Available from: 2025-04-28 Created: 2025-04-28 Last updated: 2025-04-28Bibliographically approved
Beyene, Y. B., Worku, G. B. & Bertling Tjernberg, L. (2025). Developing a novel approach for passive damped LCL filter and controller parameter design using PSO algorithm in VSC-based islanded microgrids. Array, 26, Article ID 100414.
Open this publication in new window or tab >>Developing a novel approach for passive damped LCL filter and controller parameter design using PSO algorithm in VSC-based islanded microgrids
2025 (English)In: Array, E-ISSN 2590-0056, Vol. 26, article id 100414Article in journal (Refereed) Published
Abstract [en]

In this research, a new approach called Particle Swarm Optimization–Proportional–Integral (PSO-PI) is proposed for optimizing the gains of current and voltage controllers as well as the LCL filter parameters in voltage source converter (VSC)-based islanded microgrids. The control problem is framed as an optimization task, where PSO optimally tunes parameters. Unlike conventional offline methods, this study employs a simulation-based online optimization framework, integrating PSO within SIMULINK environment for dynamic, iterative adjustments, enhancing adaptability and efficiency. Well-founded mathematical models define parameter bounds, ensuring a unity ratio between converter-side and coupling inductances, and setting the switching-to-resonance frequency ratio by considering converter-side and output ripple currents. The objective function is formulated to improve the tracking performance of the outer voltage and inner current control loops with respect to their reference signals while minimizing total harmonic distortion (THD) and maintaining an optimal balance between filtering effectiveness and system performance. The PSO-PI approach achieves a more compact LCL filter while complying with IEEE-519 standards and outperforms the conventional method (CM). Simulations validate its effectiveness under various disturbances, including load changes, faults, and parameter variations, demonstrating improved damping and robustness in VSC-based islanded microgrids. Notably, improved transient response is achieved, with a 61.80% reduction in settling time and a 51.34% decrease in overshoot. Integrating PSO within the SIMULINK framework enables dynamic fine-tuning of VSC parameters through simulation-driven optimization, highlighting its potential as a robust microgrid control strategy.

Place, publisher, year, edition, pages
Elsevier BV, 2025
Keywords
Computational Intelligence, DERs, Droop control, LCL-filter, Microgrid, Parallel passive damping, Power grid, PSO-PI, VSC
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Control Engineering
Identifiers
urn:nbn:se:kth:diva-364459 (URN)10.1016/j.array.2025.100414 (DOI)001504022700002 ()2-s2.0-105006990205 (Scopus ID)
Note

QC 20250617

Available from: 2025-06-12 Created: 2025-06-12 Last updated: 2025-06-17Bibliographically approved
Nøland, J. K., Hjelmeland, M. N., Hartmann, C., Bertling Tjernberg, L. & Korpås, M. (2025). Overview of Small Modular and Advanced Nuclear Reactors and Their Role in the Energy Transition. IEEE transactions on energy conversion, 40(3), 1933-1945
Open this publication in new window or tab >>Overview of Small Modular and Advanced Nuclear Reactors and Their Role in the Energy Transition
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2025 (English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 40, no 3, p. 1933-1945Article in journal (Refereed) Published
Abstract [en]

There is an unprecedented need to expand thetoolbox of solutions to boost the scalability of clean powerand energy systems. Amidst this challenge, nuclear energy isincreasingly recognized as an important player in the pathtoward deep decarbonization of the global energy mix. Thispaper presents a technology review of small modular reactor(SMR) concepts currently under development and deployment.Both conventional and next-generation reactor technologies areevaluated with a focus on potential power system integrationbenefits, added system values, and provision of system-bearingservices. Nevertheless, there are currently some uncertainties inthe techno-economic competitiveness of SMRs, whether they canleverage economics of mass production over their inherent lack ofeconomics of scale. To address this challenge, our paper providessome basic cost analysis of SMRs, taking into account theirexpected learning curves to evaluate the cost of future deploymentsand give insights into their economic competitiveness andpotential role as a disruptive solution in the energy transition.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2025
Keywords
Nuclear reactors, Small Modular Reactors, Power Grids, Energy Transition
National Category
Engineering and Technology Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering; Applied and Computational Mathematics
Identifiers
urn:nbn:se:kth:diva-361236 (URN)10.1109/tec.2025.3529616 (DOI)001563971900038 ()2-s2.0-85215402062 (Scopus ID)
Note

QC 20260127

Available from: 2025-03-13 Created: 2025-03-13 Last updated: 2026-01-27Bibliographically approved
Bertling Tjernberg, L. (2025). The EI2525 Electric Power Engineering Project 2024. KTH Royal Institute of Technology
Open this publication in new window or tab >>The EI2525 Electric Power Engineering Project 2024
2025 (English)Report (Other (popular science, discussion, etc.))
Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2025. p. 216
Series
TRITA-EECS-RP ; 2025:1
Keywords
electric power engineering, EI2525, project course
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-358854 (URN)
Note

QC 20240204

Available from: 2025-01-22 Created: 2025-01-22 Last updated: 2025-02-04Bibliographically approved
Simancas, C. E. i., Develder, C., Bertling Tjernberg, L. & Driesen, J. (2024). A Dynamic Price Policy Method for Electricity Grids with Flexible Thermal Loads using Grey Box Model and Differential Evolution Optimization. In: IEEE PES Innovative Smart Grid Technologies Europe, ISGT EUROPE 2024: . Paper presented at 2024 IEEE PES Innovative Smart Grid Technologies Europe Conference, ISGT EUROPE 2024, Dubrovnik, Croatia, Oct 14 2024 - Oct 17 2024. Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>A Dynamic Price Policy Method for Electricity Grids with Flexible Thermal Loads using Grey Box Model and Differential Evolution Optimization
2024 (English)In: IEEE PES Innovative Smart Grid Technologies Europe, ISGT EUROPE 2024, Institute of Electrical and Electronics Engineers (IEEE) , 2024Conference paper, Published paper (Refereed)
Abstract [en]

Power grids have become a key component in the energy transition and decarbonization of industries due to the increasing electrification of different loads, such as heating. This paper presents the overview and validation of a new method for electricity retailers or Virtual Power Plant operators to match their production portfolio dominated by Renewable Energy Resources (RES) with electrical demand of thermal loads (heat pumps) via a price control mechanism. We propose a novel three-step framework to exploit the flexibility of Thermostatically controlled loads (TCLs) by (1) simulating a pool of households, (2) estimating the governing physical parameters of the aggregated households, and (3) controlling the heat pump electric power via a dynamic price policy; for parameter estimation and price policy a Differential Evolution (DE) optimization algorithm is used. The proposed method performs well for a large number of parameters and reduced training data (errors around 0.4% and 0.55% on the average load power and standard deviation) and effectively controls the loads through a dynamic price policy that reduces the total price for the household owner or customer compared to a tariff without demand response (DR) (reduction of up to 53.63% on average per house), respecting the technical constraints of the grid.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2024
Keywords
Differential Evolution, Electricity Grids, Flexibility Services, Heat pumps, Heterogeneous loads, Implicit Demand Response, Optimization
National Category
Energy Engineering Energy Systems
Identifiers
urn:nbn:se:kth:diva-361439 (URN)10.1109/ISGTEUROPE62998.2024.10863592 (DOI)001451133800307 ()2-s2.0-86000030697 (Scopus ID)
Conference
2024 IEEE PES Innovative Smart Grid Technologies Europe Conference, ISGT EUROPE 2024, Dubrovnik, Croatia, Oct 14 2024 - Oct 17 2024
Note

Part of ISBN 9789531842976

QC 20250319

Available from: 2025-03-19 Created: 2025-03-19 Last updated: 2025-08-15Bibliographically approved
Chen, F., Yan, J., Liu, Y., Yan, Y. & Bertling Tjernberg, L. (2024). A novel meta-learning approach for few-shot short-term wind power forecasting. Applied Energy, 362, Article ID 122838.
Open this publication in new window or tab >>A novel meta-learning approach for few-shot short-term wind power forecasting
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2024 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 362, article id 122838Article in journal (Refereed) Published
Abstract [en]

Few-Shot Short-Term Wind Power Forecasting (FS-STWPF) is designed to develop accurate short-term wind power forecasting models with limited training data, reducing the losses suffered by wind farms and power systems due to the data scarcity. Based on the idea of extracting valuable knowledge from the source wind farms and then applying it to the target wind farm, a novel Meta-Learning approach (WG-Reptile) has been proposed in this paper. Building on the existing Reptile algorithm, two specific designs have been made in WG-Reptile for FS-STWPF: (1) Within-Task Samples Assignment method based on Operational Scenario (WTSAOS) has been proposed to improve the adaptability of the models to changing conditions. (2) Gradients Conflict Attenuation method based on Cosine Similarity (GCACS) has been proposed to enhance the effect of knowledge fusion from different source wind farms. Two open wind power forecasting datasets and three deep learning models have been used to implement 24-h-ahead FS-STWPF experiments with different amounts of training data. The results illustrate that the proposed WG-Reptile is able to outperform the other few-shot learning approaches. Intuitively, with only 30-day training data, the accuracy of the proposed WG-Reptile can be equivalent to the conventional supervised learning approaches trained on 6-month.

Place, publisher, year, edition, pages
Elsevier BV, 2024
Keywords
Deep learning, Few-shot learning, Few-shot short-term wind power forecasting, Meta-learning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-366886 (URN)10.1016/j.apenergy.2024.122838 (DOI)001216387100001 ()2-s2.0-85187801563 (Scopus ID)
Note

QC 20250711

Available from: 2025-07-11 Created: 2025-07-11 Last updated: 2025-07-11Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4763-9429