1,721,045 research outputs found
Control hardware in the loop for IEC61850 GOOSE performance testing
No full textIn modern power systems, communication between multiple intelligent electronic devices share time critical information for fault detection and discrimination. This has opened up a number of issues related to protection, automation and control. IEC61850 is the prominent communication standard for protection in smart grids. This paper proposes a practical approach to evaluate the performance of IEC61850 GOOSE-messaging. Dynamic system testing is suggested to evaluate real life performance of a protection scheme. Communication is central in a permissive transfer tripping scheme and is taken as example for the performance test. A three-bus transmission system is simulated using a real-time digital simulator with the protection relays in the control loop. Different methods are discussed leading to the desired performance test. Practical simulations on different fault locations were performed to evaluate latencies in hardwired and IEC61850 Ethernet-based signals. The performance is evaluated with regards to speed and dependability.status: Publishe
Pole Voltage Balancing in HVDC Systems: Analysis and Technology Options
No full textsponsorship: This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 691714. The work of Jef Beerten is funded by a research grant of the Research Foundation-Flanders (FWO). (European Union|691714, Research Foundation-Flanders (FWO))status: Publishe
Protection and Pole Voltage Rebalancing for Pole-to-ground Faults in Symmetrical Monopolar HVDC Grids
No full textPole rebalancing in symmetrical monopolar HVDC grids is
necessary to remove pole imbalances resulting from pole-toground
faults. For selective protection employing DC circuit
breakers, pole rebalancing considering backup protection operation
in case of breaker failure has until now not been studied.
This paper proposes fault clearing and post-fault restoration sequences
including pole rebalancing to deal with DC-side faults,
considering both primary and backup protection operations.
The performance of the proposed sequences and the impact of
the key breaker parameters on pole rebalancing are investigated
in a four-terminal test system using PSCAD/EMTDC.status: Publishe
Multi-vendor beschermingssysteem voor gemaasde HVDC netwerken
No full textVoltage source converter based high voltage direct current (VSC HVDC) transmission is one of the key solutions to integrate a large amount of renewable energy and to provide the increased reliability and flexibility required to handle the variable nature of renewable sources. Protecting HVDC grids against DC-side faults is essential to achieve the required reliability, yet very challenging due to the nature of the DC fault behaviour. To tackle the challenges associated with HVDC grid protection, various protection philosophies and technologies have been proposed by academia and industry in recent years. As a result, different converter and circuit breaker technologies can be implemented in the application of various fault clearing strategies, ranging from fully selective fault clearing to non-selective fault clearing.
In the meantime, multi-vendor HVDC grid development has become vitally important to allow building large-scale HVDC grids, as it is necessary to ensure competition between manufacturers which can in turn drive innovation and cost reduction. To-date, HVDC technology has mainly been used in point-to-point connections, which are typically provided by a single vendor in turn-key projects. Consequently, HVDC control and protection systems and components are often vendor-specific. The necessity to implement a multi-vendor approach has driven several international standardisation bodies to work on guidelines and standards for HVDC systems. Furthermore, in China, national standards on protection equipment and DC circuit breakers have been established along with fast development in a meshed HVDC grid. However, many technical barriers still exist blocking the implementation of multi-vendor HVDC grid protection. Particularly there is a great gap in the literature to address interoperability of the large variety of possible solutions and technologies emerged in recent years.
This thesis aims at systematically addressing multi-vendor interoperability of HVDC grid protection focusing on key components and multi-vendor protection system design. First, an overview of interoperability aspects in various multi-vendor schemes is provided and unique challenges of multi-vendor interoperability of HVDC grid protection are identified. Second, an in-depth analysis on the travelling wave behaviour during a DC fault in a meshed HVDC grid is performed, which provides a deeper understanding on the influencing parameters to the fault behaviour so that robust protection algorithms can be designed, suitable for a multi-vendor environment. Third, this thesis investigates various DC circuit breaker (DCCB) functions and their applications to achieve multi-vendor interoperability. Auxiliary DCCB functions, such as fault current limiting, self-protection, breaker failure internal detection are analysed to understand how and when to use these functions in a coordinated and beneficial way. A breaker failure backup protection algorithm, generally applicable to all DCCB technologies, is developed to deal with realistic component failures. In addition, a coordinated backup protection scheme is proposed to incorporate DCCB- and system-level protection functions. Fourth, requirements on pole rebalancing devices and necessary control and protection sequences are developed for safe and fast pole rebalancing in coordination with fault clearing in high-impedance grounded systems using DCCBs. The interactions of pole rebalancing and DCCB operation are investigated to achieve fast voltage recovery and low energy dissipating requirements. Fifth, a high-level framework to design HVDC grid protection is proposed to support a step-by-step multi-vendor grid development. A detailed protection system design is elaborated on a three-terminal system and the performance of the protection system is tested using hardware intelligent electronic devices (IED) prototypes. As a result, this work assists in facilitating future standardisation of the HVDC grids and key components, including DCCBs, DC protection IEDs and pole rebalancing equipment.status: Publishe
Modeling and Control of DC Grids
No full textThe European Union's energy policy strives for a competitive, sustainable and secure energy supply. One of the most obvious results of this policy is the ongoing strong increase of renewable energy sources in the energy supply. The transmission grid updates required to accommodate this envisaged massive amount of renewable energy sources in the transmission system go well beyond standard system reinforcements used in the past: in the coming decades, a North-Sea grid interconnecting various offshore wind farms is expected to be built. This grid can gradually evolve into a European overlay supergrid connecting the offshore wind resources with the demand centers on the continent. Also solar energy, concentrated in the south of Europe, will require similar solutions. Voltage Source Converter High Voltage Direct Current (VSC HVDC) is the most suitable technological candidate to build such a grid.One of the challenges to use this technology relates to the control of the DC voltage in case of DC system contingencies, such as a converter outage. This thesis deals with the modeling and control of VSC HVDC in a meshed DC grid and multi-terminal DC systems in general. Models are developed to address both the interactions with the AC system and the control of the DC system. The main contributions of the work include a detailed comparison of different DC voltage control strategies for multi-terminal DC systems, the development of detailed dynamic and steady-state models as well as an open-source Matlab-based power flow software program, MatACDC, which enables the study of the influence of the DC voltage control on the power flows in the AC and DC systems. Furthermore, the impact of a distributed DC voltage control on the AC system transient stability is investigated, as well as the influence of the DC system layout on the DC voltage control after a contingency.status: Publishe
Modeling and Control of DC grids - KBVE/SRBE Robert Sinave Award 2013
No full textThis paper discusses the background and main contributions of my PhD thesis entitled “modeling and control of DC grids”. The expected advent of multi-terminal HVDC systems and meshed DC grids poses major challenges to the control and operation of our power system. The article describes these challenges and explains how the work has contributed in the field of the development of steady-state and dynamic models to study the future power grid. Furthermore, the article describes new fundamental insights in system interactions that have been analyzed in the thesis.status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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