Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 7 Articles
The Indian power system underwent two separate\r\nmassive blackouts on 30th and 31st of July 2012.\r\nThese blackouts exposed a series of inherent problems\r\nunderlying the power system of India, such as its generation\r\nplanning, transmission planning, grid infrastructure,\r\nmanagement systems, primary energy resources, environmental\r\nconstraints, electricity market, and information\r\ntechnology, which together aggravate the massive blackouts.\r\nThese factors which affect the adequacy and security\r\nof the power supply in a similar manner as the transmission\r\ncongestion of physical grids does, can be called by a\r\ngeneric term as generalized congestion. Competitive\r\nmanipulations and ââ?¬Ë?ââ?¬Ë?game-playingââ?¬â?¢Ã¢â?¬â?¢ between various\r\ninterested parties further intensifies these congestions.\r\nHere, from the perspective of generalized congestions, the\r\npaper reflects the inevitability of Indiaââ?¬â?¢s massive blackouts,\r\ndiscusses occasional effects of trigger events, inherent\r\nevolution law of blackouts and the enlightenment on power\r\nindustry in China, and explores risk control measures to\r\ndefend blackouts in China. The positive role of strong\r\nsmart grid in insuring energy and environment security is\r\nhighlighted....
Ice flashover, lightning flashover and bird\r\ndamage are the main reasons that cause transmission\r\nfacility failure. The impact of these environmental factors\r\non the operational risk levels of power systems should be\r\ntaken into account in power system maintenance scheduling\r\nand operation planning. This paper studies the midshort-\r\nterm risk assessment methodology considering the\r\nimpact of the external environment. The relationship model\r\nbetween natural disasters and transmission lines is presented.\r\nThe conditional outage rate model and the sampling\r\ntechnique are then proposed considering the correlated\r\noutage of multiple transmission lines when a disaster\r\nhappens. The framework of the mid-short-term risk\r\nassessment model is outlined. A test case of Jiangxi provincial\r\npower grid validates the proposed model. The\r\nresults show that the model can quantify the impact of\r\ndisasters on the forced outage rate of transmission component\r\nand their outage correlation, and thus effectively\r\nrevealing the mid-short-term risk of power systems. The\r\nmodel can facilitate a more strategic decision-making on\r\nmaintenance scheduling and operation planning of power\r\nsystems....
With the high penetration of renewable energy\r\nsources, the reliability of power systems becomes more\r\nvulnerable than ever because of the greater uncertainty and\r\nintermittence in power generation. Reactive power plays an\r\nimportant role in the power system reliability, because it is\r\nclosely related to the system voltage stability and voltage\r\ncollapse. However, reactive power-related reliability issues\r\nare seldom emphasized in conventional power reliability\r\nevaluations. This article investigates power system reliability\r\nof real and reactive power. Real and reactive power\r\nshortages and the associated voltage violations due to\r\nsystem failures are considered on reliability evaluation of\r\npower systems. A three-stage load-shedding technique for\r\npost contingencies is implemented to determine the contributions\r\nof real and reactive power on the system reliability\r\nand to find an optimal way to release network\r\nviolation. The results provide the detailed information on\r\npower system planning and operation for system planners\r\nand operators from real and reactive power aspects....
Based on a new perspective in coordinating with\r\nthe traditional ââ?¬Ë?ââ?¬Ë?N-1ââ?¬â?¢Ã¢â?¬â?¢ criteria and system risk, a real-time\r\nelectricity market model is presented, in which the system\r\nrisk is employed to model the systemââ?¬â?¢s overall security level.\r\nThis new model is called the risk-based security-constrained\r\neconomic dispatch (RB-SCED). Relative to the securityconstrained\r\neconomic dispatch (SCED) used in the power\r\nindustry today, the RB-SCED finds more secure and economic\r\noperating conditions. It does this by obtaining solutions\r\nthat achieve a better balance between post-contingency\r\nflows on individual branches and the overall system risk. The\r\nmethod exploits the fact that, in a SCED solution, some postcontingency\r\nbranch flows which exceed their limits impose\r\nlittle risk while other post-contingency branch flows which\r\nare within their limits impose significant risk. The RB-SCED\r\nsoftens constraints for the former and hardens constraints for\r\nthe latter, thus achieving simultaneous improvement in both\r\nsecurity and economy. In this work, the basic concept and the\r\nmathematical formulation of the RB-SCED model are systematically\r\ndescribed. Experimental results on a 9-bus system\r\nand the ISO New England actual system have\r\ndemonstrated the advantages of RB-SCED over SCED....
A short-term reliability evaluation is used for\r\npower stations, where each power generating unit is presented\r\nby a multi-state Markov model. The main obstacle\r\nfor reliability evaluation in such a case is a ââ?¬Ë?ââ?¬Ë?curse of\r\ndimensionalityââ?¬â?¢Ã¢â?¬â?¢Ã¢â?¬â?a great (huge) number of states of entire\r\npower station that should be analyzed. A modern approach\r\nis proposed based on using Lz-transform that drastically\r\nsimplifies computation. The proposed approach is useful\r\nfor power system security analysis and short-term operating\r\ndecisions. In order to illustrate the proposed approach,\r\nthe short-term reliability evaluation for a power station\r\nwith different coal fired generating units is presented....
Greenhouse gas emission regulation and\r\nrenewable energy promotion policies have been implemented\r\nin many countries. Yet these two kinds of regulation\r\npolicies have complex interactions between each\r\nother, and can either enhance or reduce the overall emission\r\nreduction efficiency. If not well tuned, these regulation\r\npolicies may deviate from their original intention and lead\r\nto unnecessary social cost. Hence, the policy effectiveness,\r\ncost effectiveness, and dynamic efficiency of different\r\npolicy mixtures between emission trading and renewable\r\nenergy subsidy are studied based on a novel dynamic\r\nsimulation platform of power economy and power system.\r\nSimulation results show that these two kinds of regulation\r\npolicy can coexist, but a good coordination between the\r\nemission trading and the renewable energy subsidy can\r\nachieve better emission reduction outcomes...
The modal analysis method is utilized to study\r\nthe influence of doubly-fed induction generator (DFIG) on\r\nelectromechanical oscillations. On this basis, the small\r\nsignal stability region (SSSR) of power systems with DFIG\r\nin injection space is evaluated and the corresponding\r\nrelationship between SSSR boundary and electromechanical\r\noscillations is analyzed. The effects of the locations of\r\nDFIG on SSSR are considered. It is found that the\r\nboundary of SSSR consists of several smooth surfaces,\r\nwhich can be approximated with hyper-planes in engineering\r\napplication. With the integration of DFIG, SSSR\r\nbecomes smaller, thus indicating the deterioration of the\r\nsmall signal stability of the system. The 11-bus system with\r\nfour generators is used to illustrate the proposed method...
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