| 1. |
- Xu, Qianwen, 1992-, et al.
(author)
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A Distributed and Robust Energy Management System for Networked Hybrid AC/DC Microgrids
- 2020
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In: 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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Journal article (peer-reviewed)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.
(author)
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A Hierarchically Coordinated Operation and Control Scheme for DC Microgrid Clusters Under Uncertainty
- 2021
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In: 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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Journal article (peer-reviewed)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. |
- Xu, Qianwen, 1992-, et al.
(author)
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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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In: 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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Journal article (peer-reviewed)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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| 5. |
- Xu, Qianwen, 1992-, et al.
(author)
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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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In: 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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Journal article (peer-reviewed)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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| 6. |
- Agredano Torres, Manuel, et al.
(author)
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Decentralized Dynamic Power Sharing Control for Frequency Regulation Using Hybrid Hydrogen Electrolyzer Systems
- 2024
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In: 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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Journal article (peer-reviewed)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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| 7. |
- Agredano Torres, Manuel, et al.
(author)
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Dynamic power allocation control for frequency regulation using hybrid electrolyzer systems
- 2023
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In: 2023 IEEE Applied Power Electronics Conference And Exposition, APEC. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 2991-2998
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Conference paper (peer-reviewed)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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| 8. |
- Bhadoria, Shubhangi, et al.
(author)
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Enablers for Overcurrent Capability of Silicon-Carbide-Based Power Converters : An Overview
- 2023
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In: 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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Journal article (peer-reviewed)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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| 9. |
- Cui, Chenggang, et al.
(author)
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Implementation of Transferring Reinforcement Learning for DC-DC Buck Converter Control via Duty Ratio Mapping
- 2023
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In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 70:6, s. 6141-6150
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Journal article (peer-reviewed)abstract
- The reinforcement learning (RL) control approach with application to power electronics systems has become an emerging topic, while the sim-to-real issue remains a challenging problem as very few results can be referred to in the literature. Indeed, due to the inevitable mismatch between simulation models and real-life systems, offline-trained RL control strategies may sustain unexpected hurdles in practical implementation during the transfer procedure. In this article, a transfer methodology via a delicately designed duty ratio mapping is proposed for a dc-dc buck converter. Then, a detailed sim-to-real process is presented to enable the implementation of a model-free deep reinforcement learning controller. As the main contribution of this article, the proposed methodology is able to endow the control system to achieve: 1) voltage regulation and 2) adaptability and optimization abilities in the presence of uncertain circuit parameters and various working conditions. The feasibility and efficacy of the proposed methodology are demonstrated by comparative experimental studies.
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| 10. |
- Fu, Zuhang, et al.
(author)
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Fuel cell and hydrogen in maritime application : A review on aspects of technology, cost and regulations
- 2023
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In: Sustainable Energy Technologies and Assessments. - : Elsevier BV. - 2213-1388 .- 2213-1396. ; 57
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Journal article (peer-reviewed)abstract
- Currently, fuel cell and hydrogen technology are attracting more and more attention as a kind of green and clean energy technology in the context of the increasingly stringent carbon emission requirements of the shipping industry. However, there are still many obstacles to their maritime application due to high costs and a lack of infrastructure. This paper conducts a literature survey of fuel cell maritime applications from four aspects: key technologies of fuel cell and hydrogen maritime applications, cost and standards. It can be concluded that ships powered by hydrogen fuel cells will have a broad application prospect with the maturity of the hydrogen industry chain and the improvement of standards and regulations. Two main contributions of this paper are to fully understand a whole-process perspective of hydrogen and fuel cell maritime application, and to provide the problems and future direction in this field, which can help relevant research institutions and scholars evaluate the development status of the industrial chain and find new valuable research topics.
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