Contingency table

In statistics, a contingency table (also known as a cross tabulation or crosstab) is a type of table in a matrix format that displays the (multivariate) frequency distribution of the variables. They are heavily used in survey research, business intelligence, engineering, and scientific research. They provide a basic picture of the interrelation between two variables and can help find interactions between them. The term contingency table was first used by Karl Pearson in "On the Theory of Contingency and Its Relation to Association and Normal Correlation", part of the Drapers' Company Research Memoirs Biometric Series I published in 1904. A crucial problem of multivariate statistics is finding the (direct-)dependence structure underlying the variables contained in high-dimensional contingency tables. If some of the conditional independences are revealed, then even the storage of the data can be done in a smarter way (see Lauritzen (2002)). In order to do this one can use information

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Centralized and Decentralized Electricity Markets: Assessment of Operational and Economic Aspects

Farzaneh Abbaspourtorbati, Anneta Matenli

This paper presents the comparison of decentralized and centralized market settings in terms of economic efficiencies, particularly price signals, and operating aspects. The decentralized dispatch consists of an energy auction separated from a contingency analysis. The centralized setting is the conventional economic dispatch. This comparison includes deterministic and stochastic formulations (source of uncertainty is wind generation) applied on the Swiss power system.

Ieee2016

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The paper describes a local under-frequency load shedding and load restoration scheme, that exploits frequency and Rate-of-Change-of-Frequency (ROCOF) measurements produced by Phasor Measurement Units (PMUs) as detectors of a large contingency. The paper further discusses the appropriateness of using the synchrophasor model for estimating ROCOF during fast transients following a severe generation-load imbalance. The performance of the proposed relaying scheme is compared with a frequency-only based strategy, by means of a real-time digital simulator implementing the time-domain full-replica model of the IEEE 39 bus system.

IEEE2018

Investigation of P-V and V-Q based optimization methods for voltage and reactive power analysis

Omid Alizadeh Mousavi

The management of voltage and reactive power control sources considering the voltage stability is a challenging issue for secure operation of power systems. Generally the analysis of the stability margin is performed using P V and V Q based approaches. This paper initially investigates the main characteristics of these two stability analysis methods. Regarding these two approaches, two formulations for the maximization of loading factor and the maximization of effective reactive power reserve are studied. Both of them can be considered as preventive actions. Other formulations are presented for contingency analysis and evaluation of required corrective actions. The proposed formulations benefit from: (i) the detailed modeling of generators reactive power limits, (ii) the generators mode switch between constant terminal voltage and constant reactive power output with complementarity constraints and (iii) the distributed slack bus model for the compensation of active power imbalances. The effectiveness of the proposed formulations as well as the advantages and drawbacks of these two stability analysis approaches are discussed more in depth using three test systems. (C) 2014 Elsevier Ltd. All rights reserved.

Elsevier2014

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