2,473 research outputs found
Using real-time simulation to assess the impact of a high penetration of LV connected microgeneration on the wider system performance during severe low frequency
In addition to other measures such as energy saving, the adoption of a large amount of microgeneration driven by renewable and low carbon energy resources is expected to have the potential to reduce losses associated with producing and delivering electricity, combat climate change and fuel poverty, and improve the overall system performance. However, incorporating a substantial volume of microgeneration within a system that is not designed for such a paradigm could lead to conflicts in the operating strategies of the new and existing centralized generation technologies. This paper investigates the impact of tripping substantial volumes of LV connected microgeneration on the dynamic performance of a large system during significant low frequency events. An initial dynamic model of the UK system based on a number of coherent areas as identified in the UK Transmission Seven Year Statement (SYS) has been developed within a real time digital simulator (RTDS) and this paper presents the early study results
Methodology for testing loss of mains detection algorithms for microgrids and distributed generation using real-time power hardware–in-the-loop based technique
The effective integration of distributed energy resources in distribution networks demands powerful simulation and test methods in order to determine both system and component behaviour, and understand their interaction. Unexpected disconnection of a significant volume of distributed generation (DG) could have potentially serious consequences for the entire system [1], this means DG sources can no longer be treated as purely negative load. This paper proposes a method of testing loss-of-mains (LOM) detection and protection schemes for distributed energy resources (DER) using real-time power hardware-in-the-loop (RT PHIL). The approach involves connecting the generator and interface under test (e.g. motor-generator set or inverter, controlled by an RTS – Real Time Station[3]) to a real-time simulator (an RTDS – Real Time Digital Simulator[2]) which simulates the local loads and upstream power system. This arrangement allows observation of the interaction with other controls in the network beyond the local microgrid area. These LOM schemes are of increasing importance because with growing penetration levels of distributed generation the network operator has less visibility and control of the connected generation. Furthermore when the generation and load in a particular network area are closely matched (e.g. a grid-connected microgrid), it becomes increasingly difficult to detect a loss of grid supply at the generator. This work builds upon the existing LOM testing methodology proposed in [4]. By utilising RT PHIL and a laboratory microgrid, the testing environment has been brought to a new level of functionality where system integrity can be more rigorously and realistically evaluated
Optimizing the roles of unit and non-unit protection methods within DC microgrids
The characteristic behavior of physically compact, multiterminal dc networks under electrical fault conditions can produce demanding protection requirements. This represents a significant barrier to more widespread adoption of dc power distribution for microgrid applications. Protection schemes have been proposed within literature for such networks based around the use of non-unit protection methods. This paper shows however that there are severe limitations to the effectiveness of such schemes when employed for more complex microgrid network architectures. Even current differential schemes, which offer a more effective, though costly, protection solution, must be carefully designed to meet the design requirements resulting from the unique fault characteristics of dc microgrids. This paper presents a detailed analysis of dc microgrid behavior under fault conditions, illustrating the challenging protection requirements and demonstrating the shortcomings of non-unit approaches for these applications. Whilst the performance requirements for the effective operation of differential schemes in dc microgrids are shown to be stringent, the authors show how these may be met using COTS technologies. The culmination of this work is the proposal of a flexible protection scheme design framework for dc microgrid applications which enables the required levels of fault discrimination to be achieved whilst minimizing the associated installation costs
Ariel - Volume 3 Number 5
Editors
Richard J. Bonanno
Robin A. Edwards
Associate Editors
Steven Ager
Tom Williams
Lay-out Editor
Eugenia Miller
Contributing Editors
Paul Bialas
Robert Breckenridge
Lynne Porter
David Jacoby
Terry Burt
Mark Pearlman
Michael Leo
Mike LeWitt
Editors Emeritus
Delvyn C. Case., Jr.
Paul M. Fernhof
Quantum Clock Synchronization: a Multi-Party Protocol
We present a multi-party quantum clock synchronization protocol that utilizes
shared prior entanglement and broadcast of classical information to synchronize
spatially separated clocks. Notably, it is necessary only for any one party to
publish classical information. Consequently, the efficacy of the method is
independent of the relative location of the parties. The suggested protocol is
robust and does not require precise sequencing of procedural steps.Comment: 3 page
Mutation in the guanine nucleotide-binding protein beta-3 causes retinal degeneration and embryonic mortality in chickens
PURPOSE. To identify the gene defect that causes blindness and the predisposition to embryonic death in the retinopathy globe enlarged (rge) chicken. METHODS. Linkage analysis, with previously uncharacterized microsatellite markers from chicken chromosome 1, was performed on 138 progeny of an rge/+ and an rge/rge cross, and candidate genes were sequenced. RESULTS. The rge locus was refined and the gene for guanine nucleotide-binding protein β-3 (GNB3), which encodes a cone transducin β subunit, was found to have a 3-bp deletion (D153del) that segregated with the rge phenotype. This mutation deleted a highly conserved aspartic acid residue in the third of seven WD domains in GNB3. In silico modeling suggested that this mutation destabilized the protein. Furthermore, a 70% reduction was found in immunoreactivity to anti-GNB3 in the rge-affected retina. CONCLUSIONS. These findings implicate the β-subunit of cone transducin as the defective protein underlying the rge phenotype. Furthermore, GNB3 is ubiquitously expressed, and the c.825C→T GNB3 splicing variant (MIM 139130) has been associated with hypertension, obesity, diabetes, low birth weight, coronary heart disease, and stroke in the human population. It therefore seems likely that the defect underlying these human diseases also causes reduced embryonic viability in the rge chicken, making it a powerful model for studying the pathology involved in these associations
Visible Branes with Negative Tension in Heterotic M-Theory
It is shown that there exist large classes of BPS vacua in heterotic M-theory
which have negative tension on the visible orbifold plane, positive tension on
the hidden plane and positive tension, physical five-branes in the bulk space.
Explicit examples of such vacua are presented. Furthermore, it is demonstrated
that the ratio, beta/|alpha|, of the bulk five-brane tension to the visible
plane tension can, for several large classes of such vacua, be made arbitrarily
small. Hence, it is straightforward to find vacua with the properties required
in the examples of the Ekpyrotic theory of cosmology - a visible brane with
negative tension and beta/|alpha| small. This contradicts recent claims in the
literature.Comment: 30 page
Evaluating the robustness of an active network management function in an operational environment
This paper presents the integration process of a distribution network Active Network Management (ANM) function within an operational environment in the form of a Micro-Grid Laboratory. This enables emulation of a real power network and enables investigation into the effects of data uncertainty on an online and automatic ANM algorithm's control decisions. The algorithm implemented within the operational environment is a Power Flow Management (PFM) approach based around the Constraint Satisfaction Problem (CSP). This paper show the impact of increasing uncertainty, in the input data available for an ANM scheme in terms of the variation in control actions. The inclusion of a State Estimator (SE), with known tolerances is shown to improve the ANM performance
Ariel - Volume 3 Number 2
Editors
Richard J. Bonanno
Robin A. Edwards
Associate Editors
Steven Ager
Stephen Flynn
Tom Williams
Lay-out Editor
Eugenia Miller
Contributing Editors
Paul Bialas
Milton Packer
Robert Breckenridge
Lynne Porter
Mark Pearlman
Terry Burt
Mike Leo
Editors Emeritus
Delvyn C. Case, Jr.
Paul M. Fernhof
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