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This paper addresses the study of the existing dynamic interaction phenomena between control devices of variable speed wind generators and conventional generators embedded in power systems. A direct-drive wind generation system with a permanent magnet synchronous generator has been chosen to make the study because of the relative complexity of the back-to-back converters used to make the grid connection...
In this paper we introduce the Collapse Index, a new measure of the relevance of individual formal concepts in a concept lattice, the application of which improves the performance of concept pruning and reduces the bias against "outlier" concepts. The measure determines the relevance of a formal concept in the lattice by calculating the minimum number of objects which need to be removed...
This paper presents the reliability evaluation of microgrids with distributed generation based on renewable energy sources and storage systems. A hybrid model that combines the analytical approach with state sampling is used in order to consider the intermittence of renewable sources, like wind, solar and small hydro power plants. Batteries are used to reduce the supply intermittence of both the solar...
Maximum Power Point Tracking (MPPT) is an essential element of a PV system. Bench power supplies provide a reasonable approximation of solar panel behavior and can be used for initial testing. However, detailed testing with actual solar panels is required to accurately establish the performance of MPPTs. This could be a difficult and time consuming task, especially for medium and high power ratings,...
We quantify carbon emissions and savings in Demand Side Response (DSR) programmes, such as Short Term Operating Reserve (STOR) and Triad, substituting grid energy in the UK power networks. We model each of the DSR programmes with configurations and assumptions appropriate for the UK energy industry. This enables us to compare carbon emissions between the business-as-usual (BAU) and the smart intervention...
Most of current diagnosis methods of hydroelectric generator unit (HGU) performed not well when lacking domain expert knowledge, in order to address this problem, we propose a novel residual diagnosis model based on wavelet neural network (RDM-WNN) and weighed fuzzy set theory for quantitative diagnosis of HGU in this paper. First, the main working condition parameters (MWCP) are extracted according...
Various big data management systems have emerged to handle different types of applications, which cast very different demands on storage, indexing and retrieval of large amount of data on distributed file system. Such diversity on demands has raised huge challenges to the design of new generation of data access service for big data. In this paper, we present PABIRS, a unified data access middleware...
In [3], we laid out the vision of a novel graph query processing paradigm, where visual subgraph query formulation is interleaved (or “blended”) with query processing by exploiting the latency offered by the gui. Our recent attempts at implementing this vision [6], [7] do not provide any robust framework to systematically investigate the performance of this novel paradigm. This is because it is prohibitively...
Model Predictive Control (MPC) is a popular advanced control strategy that is implemented by determining an optimal control sequence at each time step. One of the major contributors to MPC's computational complexity is the length of the control sequence or, equivalently, the number of optimisation parameters. This paper analyses the null controllable sets, and their related finite horizon approximation,...
As electric power systems become larger and more complex, they become increasingly difficult to control. The problem of transient stability has, accordingly, attracted much recent attention owing to the concerns over the possibility of multiswings occurring in longitudinal power systems such as the Japanese power grid. Although multiswings are becoming an important issue, it remains difficult to develop...
With the increase of wind power penetration, the impact of wind power ramp event on power system becomes more and more serious. To assess the impact of it on power system, the characteristic and development process of wind power ramp event is analyzed, and a time-dependent outage model of conventional generators which is appropriate to wind power ramp event is constructed base on Monte-Carlo method...
Computer system designers need a deep understanding of end users’ workload in order to arrive at an optimum design. Unfortunately, many end users will not share their software to designers due to the proprietary or confidential nature of their software. Researchers have proposed workload cloning, which is a process of extracting statistics that summarize the behavior of users’ workloads through profiling,...
The goal of the U.S. Department of Energy (DOE) roadmap [1] is a 20% penetration of wind energy into the generation mix by 2030. Attaining this objective will help protect the environment and reduce fossil fuel dependency, thus improving energy security and independence. This paper discusses how the technology used in large scale offshore wind farms impacts voltage regulation in distribution feeders...
Two new static indexes that use time series from power system dynamic simulations are presented on this paper. The proposed indexes are used to check whether the time series from dynamic simulations will converge to a safe and stable equilibrium point and to measure the quality of the stability. They can also be used to classify simulations according to the severity of the contingency applied. The...
This paper presents a Fast Fourier Transform (FFT) processor optimized for both ‘area’ and ‘frequency’. The processor architecture is deeply pipelined Radix-2 butterfly unit, 1024 point, 64bit Fixed Point input with 32bit real and 32bit imaginary, Decimation In Time (DIT) FFT processor on Field Programmable Gate Array (FPGA). The proposed architecture is based on Dual RAM Ping-Pong Burst I/O with...
This paper presents a two-layered framework for managing multi-interval economic dispatch with both transmission and ramping constraints in electric energy systems with a large penetration of variable resources. The proposed model is aimed at ensuring that there is sufficient flexibility in the dispatch to manage large net load ramp events while observing the transmission constraints in the power...
Distribution Generation Networks connected to low voltage distribution networks are nowadays becoming popular due to advantages over the other resources and environmental benefits. In spite of these benefits DG also impacts on the power system. Problems arising due to connection of Distribution Generation (DG) to the Distribution Network (DN) are such as power system stability issues, voltage regulation...
This paper analyses the impact of grid-connected photovoltaic (PV) system on static voltage stability using IEEE 30-bus test system. The impact of integrating PV generator into power system was determined. Various penetration PV level and PV generator locations are thoroughly studied using P-V curve and improved voltage stability index (IVSI-index). P-V curve results show that the presence of PV generator...
Row based relational database management systems (R-RDBMS) are the most common choice for data warehouse implementations. Row based storage is useful in online transaction processing (OLTP) to insert and update data while column oriented RDBMS (C-RDBMS) in online analytical processing (OLAP) to access data from data warehouse. This paper analyses the best suited mode of storage (row or column based...
In this paper, we propose to solve the max-min multiple knapsack problem by using an exact solution search. An instance of the problem is defined by a set of n items to be packed into m knapsacks as to maximize the minimum of the knapsacks' profits. The proposed method uses a series of interval searches, where each interval is bounded with a target value (considered as a lower bound) and an estimated...
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