| 1. |
- Xu, Qianwen, 1992-, et al.
(författare)
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A Distributed and Robust Energy Management System for Networked Hybrid AC/DC Microgrids
- 2020
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Ingår i: IEEE Transactions on Smart Grid. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3053 .- 1949-3061. ; 11:4, s. 3496-3508
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid AC/DC microgrids (MGs) provide efficient integration of renewable sources into grids and the interconnection of multiple MGs can improve system reliability, efficiency and economy by energy sharing. In this paper, a distributed and robust energy management system is proposed for networked hybrid AC/DC MGs. For each individual MG, an adjustable robust optimization model is proposed to optimize its individual operational cost considering the uncertainty of the renewable generation and load demand. For the networked-MGs system, the energy sharing information of each MG is coordinated by the DC network to minimize the power transmission loss with network constraints. The overall optimization model is formulated, exactly convexified and solved in a distributed manner by the alternating direction method of multipliers (ADMM), where only limited information is required from each MG entity (i.e., the power injection to the network) and thus information privacy is guaranteed. Simulations of the networked hybrid AC/DC MGs are conducted to demonstrate the effectiveness of the proposed energy management system.
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| 2. |
- Xu, Qianwen, 1992-, et al.
(författare)
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A Hierarchically Coordinated Operation and Control Scheme for DC Microgrid Clusters Under Uncertainty
- 2021
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Ingår i: IEEE Transactions on Sustainable Energy. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3029 .- 1949-3037. ; 12:1, s. 273-283
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Tidskriftsartikel (refereegranskat)abstract
- In the existing works of microgrid clusters, operation and real-time control are normally designed separately in a hierarchical architecture, with the real-time control in the primary and secondary levels, and operation in the tertiary level. This article proposes a hierarchically coordinated control scheme for DC MG clusters under uncertainty. In each MG, the tertiary level controller optimizes the operating cost in the MG by taking into account the real-time uncertainties of renewable generations and loads deviated from the forecasting data; and the primary controller responds to the real-time power fluctuations through an optimised droop curve. The hierarchically coordinated optimization problem is formulated to optimize the power set points and droop curve coefficients simultaneously under uncertainties using an adjustable robust optimization model. For the MG cluster, the energy sharing of each MG in the cluster is optimized to minimize the total operating cost and the transmission loss. The overall optimization problem is solved in a distributed manner by alternating direction method of multipliers (ADMM) where each MG entity only exchanges boundary information (i.e. the power exchange of MG entity with the MG cluster), thus information privacy and plug-and-play feature of each MG are guaranteed. The proposed approach optimally coordinates the operation and real-time control layers of a DC MG cluster with uncertainties; it achieves decentralized power sharing at the real-time control layer and distributed optimization at the operation layer, featuring high scalability, reliability and economy. Case studies of a DC MG cluster are conducted in Matlab/Simulink in order to demonstrate the effectiveness of the proposed approach.
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| 3. |
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| 4. |
- Cao, Haozhi, et al.
(författare)
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Self-Supervised Video Representation Learning by Video Incoherence Detection
- 2023
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Ingår i: IEEE Transactions on Cybernetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2168-2267 .- 2168-2275.
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Tidskriftsartikel (refereegranskat)abstract
- This article introduces a novel self-supervised method that leverages incoherence detection for video representation learning. It stems from the observation that the visual system of human beings can easily identify video incoherence based on their comprehensive understanding of videos. Specifically, we construct the incoherent clip by multiple subclips hierarchically sampled from the same raw video with various lengths of incoherence. The network is trained to learn the high-level representation by predicting the location and length of incoherence given the incoherent clip as input. Additionally, we introduce intravideo contrastive learning to maximize the mutual information between incoherent clips from the same raw video. We evaluate our proposed method through extensive experiments on action recognition and video retrieval using various backbone networks. Experiments show that our proposed method achieves remarkable performance across different backbone networks and different datasets compared to previous coherence-based methods.
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| 5. |
- Xu, Qianwen, 1992-, et al.
(författare)
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A Composite Finite-Time Controller for Decentralized Power Sharing and Stabilization of Hybrid Fuel Cell/Supercapacitor System With Constant Power Load
- 2021
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Ingår i: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 68:2, s. 1388-1400
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Tidskriftsartikel (refereegranskat)abstract
- The hybrid fuel cell/supercapacitor (FC/SC) system is a promising onboard power supply system for more electric aircraft (MEA), where system stability is a critical issue due to the high penetration of constant power loads (CPLs) in MEA. This article proposes a composite finite-time controller for decentralized power sharing and stabilization of the hybrid FC/SC system with CPLs. It consists of an integral droop (ID) + finite-time controller for the SC converter and a proportional droop (PD) + finite-time controller for the FC converter. First, the coordination of PD and ID achieves decentralized power sharing between FC and SC such that SC only compensates fast fluctuations and FC provides smooth power at the steady state. Then, a finite-time observer is designed to provide feedforward compensation for the disturbances and enables accurate tracking with fast dynamics. Finally, a composite finite-time controller is constructed following a nonrecursive synthesis procedure with a rigorous large signal stability analysis. The proposed controller guarantees finite-time convergence even under large signal variations and can be easily implemented with a practical gain tuning procedure. Simulations and experiments are conducted to verify the proposed technique.
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| 6. |
- Xu, Qianwen, 1992-, et al.
(författare)
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A Robust Droop-Based Autonomous Controller for Decentralized Power Sharing in DC Microgrid Considering Large-Signal Stability
- 2020
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Ingår i: IEEE Transactions on Industrial Informatics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1551-3203 .- 1941-0050. ; 16:3, s. 1483-1494
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Tidskriftsartikel (refereegranskat)abstract
- The high penetration of power electronic converter loads in dc microgrid causes system stability issue, or also known as constant power load issue, due to their negative impedance characteristics. The stability concern will be more complicated for a self-disciplined microgrid that allows plug and play of various distributed generations (DGs). This article proposes a robust droop-based controller for decentralized power sharing in a dc microgrid considering large-signal stability. For each DG interface converter subsystem, the interactions with other DG interface converters and loads are estimated by a nonlinear disturbance observer (NDO) utilizing the subsystem's own information to achieve decentralized power sharing and fast voltage regulation. With the uncertainties of circuit parameters modeled as a lumped disturbance term and compensated by an NDO, the proposed controller can significantly enhance the robustness against the uncertainties of circuit parameters. The large-signal stability of the whole interconnected system is proved by the backstepping algorithm and Lyapunov theorem. The efficacy and large-signal stability of the proposed approach are verified by both simulations and experiments.
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| 7. |
- Agredano Torres, Manuel, et al.
(författare)
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Decentralized Dynamic Power Sharing Control for Frequency Regulation Using Hybrid Hydrogen Electrolyzer Systems
- 2024
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Ingår i: IEEE Transactions on Sustainable Energy. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3029 .- 1949-3037. ; 15:3, s. 1847-1858
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen electrolyzers are promising tools for frequency regulation of future power systems with high penetration of renewable energies and low inertia. This is due to both the increasing demand for hydrogen and their flexibility as controllable load. The two main electrolyzer technologies are Alkaline Electrolyzers (AELs) and Proton Exchange Membrane Electrolyzers (PEMELs). However, they have trade-offs: dynamic response speed for AELs, and cost for PEMELs. This paper proposes the combination of both technologies into a Hybrid Hydrogen Electrolyzer System (HHES) to obtain a fast response for frequency regulation with reduced costs. A decentralized dynamic power sharing control strategy is proposed where PEMELs respond to the fast component of the frequency deviation, and AELs respond to the slow component, without the requirement of communication. The proposed decentralized approach facilitates a high reliability and scalability of the system, what is essential for expansion of hydrogen production. The effectiveness of the proposed strategy is validated in simulations and experimental results.
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| 8. |
- Agredano Torres, Manuel, et al.
(författare)
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Dynamic power allocation control for frequency regulation using hybrid electrolyzer systems
- 2023
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Ingår i: 2023 IEEE Applied Power Electronics Conference And Exposition, APEC. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 2991-2998
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Konferensbidrag (refereegranskat)abstract
- The increase in hydrogen production to support the energy transition in different sectors, such as the steel industry, leads to the utilization of large scale electrolyzers. These electrolyzers have the ability to become a fundamental tool for grid stability providing grid services, especially frequency regulation, for power grids with a high share of renewable energy sources. Alkaline electrolyzers (AELs) have low cost and long lifetime, but their slow dynamics make them unsuitable for fast frequency regulation, especially in case of contingencies. Proton Exchange Membrane electrolyzers (PEMELs) have fast dynamic response to provide grid services, but they have higher costs. This paper proposes a dynamic power allocation control strategy for hybrid electrolyzer systems to provide frequency regulation with reduced cost, making use of advantages of AELs and PEMELs. Simulations and experiments are conducted to verify the proposed control strategy.
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| 9. |
- Berg, Petra, et al.
(författare)
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Towards a Model for Assessing the Effects of Social-Cyber-Physical Threats on the Future Power Grid - Review and Workshop Results
- 2024
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Ingår i: 2024 International Workshop on Artificial Intelligence and Machine Learning for Energy Transformation, AIE 2024. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- The energy system, including the electrical power system, is currently undergoing major changes to meet increased demands and climate target plans, and to stand against potential malicious activities and all sorts of disruptions. Specifically, the electrical power system is drastically changing with regards to consumption, production, transmission, control, monitoring, markets, and digitalization. Such a change, however, makes the power system an attractive and vulnerable target to all kinds of disruptive events and social-cyber-physical attacks since the system is crucial for the functioning of the society and economy. In this work, to act against such events and to study the future power system's susceptibility and resilience towards social-cyber-physical attacks, the Resilient Digital Sustainable Energy Transition (REDISET) project has shown the need for a new model that is able to describe the future electrical power system in a way that reflects the future reality. In this paper, existing power system models, the changing landscape of power systems, the drivers for a new model, the suggested model that comprises 7 building blocks instead of today's 3, and finally a direction of future related work are presented.
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| 10. |
- Bhadoria, Shubhangi, et al.
(författare)
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Enablers for Overcurrent Capability of Silicon-Carbide-Based Power Converters : An Overview
- 2023
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Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers Inc.. - 0885-8993 .- 1941-0107. ; 38:3, s. 3569-3589
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Tidskriftsartikel (refereegranskat)abstract
- With the increase in penetration of power electronic converters in the power systems, a demand for overcurrent/ overloading capability has risen for the fault clearance duration. This article gives an overview of the limiting factors and the recent technologies for the overcurrent performance of SiC power modules in power electronics converters. It presents the limitations produced at the power module level by packaging materials, which include semiconductor chips, substrates, metallization, bonding techniques, die attach, and encapsulation materials. Specifically, technologies for overcurrent related temperatures in excess of 200°C are discussed. This article also discusses potential technologies, which have been proven or may be potential candidates for improving the safe operating area. The discussed technologies are use of phase-change materials below the semiconductor chip, Peltier elements, new layouts of the power modules, control and modulation techniques for converters. Special attention has been given to an overview of various potential phase-change materials, which can be considered for high-temperature operations.
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