1,721,167 research outputs found
Automated and scalable optimal control of three-Phase embedded power grids including PLL
No full textEmbedded grids have been increasingly adopted into applications such as More Electric Aircraft where different power converters are interconnected to each other. Interactions between the grid components poses the risk of instability to the system, more so when in the presence of reduced passive filters. An approach of automated and scalable tuning of such embedded grids with consideration for the dynamics introduced by a PLL is presented in this paper. A structured state feedback optimal control approach is proposed which enables a controller to be synthesised is such a way that maximum performance of the grid can be achieved, whilst guaranteeing power converter synchronisation to the grid, and avoiding instability due to converter interaction, and PLL dynamics. © 2017 IEEE
Controller Design of an Active Front-End Converter Keeping in Consideration Grid Dynamic Interaction
No full textThis article presents a systematic control
design procedure for an active front-end (AFE) converter
connected to a power electronics embedded grid. A parametric model of the grid is first identified using the AFE
itself to excite the system. This model is then integrated
with the AFE one in order to obtain a global system representation. Subsequently, a globally optimized local controller is synthesized for the AFE keeping in consideration
the interaction between the converter and the grid. The
proposed method is finally tested experimentally, and its
performance is compared with a traditional proportional–
integral controller in a dq synchronous reference fram
Grid impedance identification and structured-h2 optimization based controller design of active front-end in embedded AC networks
No full textThe increasing use of power electronics systems and distributed generation in modern power networks has raised important issues regarding the effects that inter-connected converters systems can have on the performance and stability of the whole grid. Interactions between locally optimized converters, designed not taking into account the external influence of the system in which they are operating, may lead to performance degradation or even system instability and failure. This paper will deal with the problem of active-front end control design taking into account of system interactions with other power converters in the grid. A globally optimized local converter control tuning method, which is based on a state space model identification of the unknown grid system seen from the converter at its point of common coupling (PCC), is here proposed. The plant for the control design will then be not only represented by the local converter dynamics, but will also include the identified system at the PCC. In order to describe and validate the concept, a simplified notional system, comprising of two interconnected converter systems coupled on the same AC bus is analyzed. The effectiveness and advantages of the proposed method is validated by experiments with a traditionally designed PI controller for comparison. © 2019 IEEE
Performance Analysis of H- 2 Optimally Controlled Three-Phase Grids
No full textEmbedded electrical grids are comprised of multiple interconnected power converters, and have been recently adopted widely into applications such as micro-grids, electrical ships and More Electric Aircraft (MEA). Key aims of MEA research include reducing the overall size and weight of the electrical system without compromise to performance. H2 control optimization have been gaining large attention in the development of controllers for such systems. In this paper, a comparative review between decentralised optimal H2 controllers, and more traditional PI control method for a three-phase embedded grid in MEA shall be undertaken. The comparison involves investigating the tuning process, the implementation, the performance and the capability of reducing the overall size and weight of the system. H2 controls are being designed with full knowledge of the system dynamics and interactions, and is expected in theory to deliver greater capability to meet MEA core research objectives, in contrast to traditional PI methods. © 2018 IEEE
Optimized control design for power converters in power electronics embedded networks integrating grid model identification
No full textThe proliferation of power electronics systems and distributed generation in modern power networks has raised important issues regarding the effects that interconnected converters systems can have on the performance and stability of the whole grid. Interactions between locally optimized converters, designed not taking into account the external influence of the system in which they are operating, may lead to performance degradation or even system instability and failure. This paper will deal with the problem of power converters control design taking into account system interactions with other power converters in the grid. A globally optimized control tuning approach along with a state space grid identification method is here presented. Simulation and experimental results clearly show that the dynamic behaviour of the proposed method outperforms standard tuning techniques. A prototype embedded network composed by two power converters is built and the experimental results validate the effectiveness of proposed optimized control method. © 2018 IEE
Fast Self-Tuning Decentralized Variable Frequency Optimal Controller Design for Three-Phase Embedded Grids
No full textIn this paper, a novel approach to variable frequency optimal controller design for the application of aircraft embedded grids is presented. Aircraft power grids by industrial standards need to be able to operate across a range of frequencies. Often, these systems are controlled by active power-based controls, which are well known for being rather slow in response time. A novel method of variable frequency optimal control using H2 optimization is presented. It is shown that designing the control as such not only guarantees the optimal performance across the full range of frequencies being designed for, but fast responses to frequency and step load changes can be achieved. © 2019 IEEE
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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