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RISS 인기검색어
- 검색키워드
- 저자 : E. Kontos (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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A Fast Steady-State Loss Model of a Modular Multilevel Converter for Optimization Purposes
A. Papadopoulos,S. Rodrigues,E. Kontos,T. Todorcevic,P. Bauer 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Lesnicar and Marquardt introduced a Modular Multilevel Converter (MMC) topology back in 2003. Although this topology has received a great deal of attention in recent years by both the research community and industry, hitherto no steadystate model has been developed which accurately captured all the relevant power losses while being computationally light. Hence, the aim of this paper is to introduce a fast MMC loss model which captures the key sources of power losses in steady-state operation. The model only requires information which is known a priori, e.g. datasheet information of the components. The proposed model was compared to a loss model developed by Marquardt. Both models presented similar results under the same assumptions. However, the proposed model captures the switching losses more realistically and considers the temperature of operation of the electronics, as well as the losses of the inductors and cooling system in the overall efficiency of the MMC. To validate these new additions, the proposed steady-state model was compared to a dynamic model. Once again the proposed model was able to capture the different sources of power losses. Nonetheless, results demonstrated that the balancing strategy greatly influences the efficiency of the MMC. Therefore, information regarding the envisioned control strategy is necessary to accurately calculate the efficiency curve of the MMC.
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Providing dc fault ride-through capability to H-bridge MMC-based HVDC Networks
E. Kontos,R. Teixeira Pinto,P. Bauer 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a framework to achieve dc fault ride-through capability in multi-terminal dc networks (MTdc), when H-bridge multilevel modular converters (MMC) are used. The studied network consists of four voltage-source converters (VSC) for high voltage direct current (HVdc) transmission. Two of these VSC converters connect two offshore wind farms (OWF) to the main HVdc link between two asynchronous onshore grids, in a radial configuration. In case of a dc fault, H-bridge MMCs are able to block the fast developing currents and drive them to zero, allowing for fast mechanical disconnectors to isolate the faulty cable segment and reconfigure the grid layout. In this paper, the effect of the dc fault location to the grid behavior is analysed both at the fault isolation phase, as well as at the grid restoration phase. Moreover, the worst-case dc fault scenario for the studied network is identified. Finally, the total fault recovery time of the MTdc network is estimated. The study showed that Hbridge MMCs are unable to isolate the faulty part of the network without de-energizing the MTdc grid. However, the proposed framework allows for fast grid restoration within 3.6 s without the need for expensive dc breakers.
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AC fault clearing within an MMC-based DC hub
M. Poikilidis,E. Kontos,P. Bauer 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
As the number of high voltage (HVDC) installations is increasing, there is a growing need for interconnection to create more efficient grids. To tackle the main challenges in HVDC grids, a multiport DC-DC converter, often referred to as DC hub, is considered a solution. This paper provides a methodology for the clearing of AC faults within the DC hub and the protection of the system during a fault. A methodology is also presented for the safe connection or disconnection of additional ports from the DC hub without affecting the operation of the other ports. A design based on modular multilevel converters (MMC) is chosen due to their inherent advantages and its control operation is described. A DC hub was modelled in Matlab/Simulink and was tested in a case study including the interconnection of three DC lines in symmetric monopolar configuration, operating at different voltage levels.
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Observation of the frozen charge of a Kondo resonance
Desjardins, M. M.,Viennot, J. J.,Dartiailh, M. C.,Bruhat, L. E.,Delbecq, M. R.,Lee, M.,Choi, M.-S.,Cottet, A.,Kontos, T. Macmillan Publishers Limited, part of Springer Nat 2017 Nature Vol.545 No.7652
<P>The ability to control electronic states at the nanoscale has contributed to our modern understanding of condensed matter. In particular, quantum dot circuits represent model systems for the study of strong electronic correlations, epitomized by the Kondo effect(1-3). We use circuit quantum electrodynamics architectures to study the internal degrees of freedom of this many-body phenomenon. Specifically, we couple a quantum dot to a highquality- factor microwave cavity to measure with exceptional sensitivity the dot's electronic compressibility, that is, its ability to accommodate charges. Because electronic compressibility corresponds solely to the charge response of the electronic system, it is not equivalent to the conductance, which generally involves other degrees of freedom such as spin. Here, by performing dual conductance and compressibility measurements in the Kondo regime, we uncover directly the charge dynamics of this peculiar mechanism of electron transfer. The Kondo resonance, visible in transport measurements, is found to be ` transparent' to microwave photons trapped in the high-quality cavity, thereby revealing that (in such a many-body resonance) finite conduction is achieved from a charge frozen by Coulomb interaction. This freezing of charge dynamics(4-6) is in contrast to the physics of a free electron gas. We anticipate that the tools of cavity quantum electrodynamics could be used in other types of mesoscopic circuits with many-body correlations7,8, providing a model system in which to perform quantum simulation of fermion-boson problems.</P>
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