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reactivity
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Equilibrium approach to reactive distillation calculations with identification of phases
, Article 19th International Congress of Chemical and Process Engineering, CHISA 2010 and 7th European Congress of Chemical Engineering, ECCE-7, 28 August 2010 through 1 September 2010, Prague ; 2010 ; Avami, A ; Sharif University of Technology
2010
Abstract
A method for simultaneous phase identification and equilibrium calculations is put forward and applied on the highly nonlinear multiphase reactive distillation calculations. The method is based on modifying mole fraction summation equations. In the proposed methodology phase identification, phase equilibrium, and chemical reaction equilibrium calculations can be performed simultaneously and effectively. Simulation and optimization of equilibrium reactive distillation can be done efficiently using this approach. The methodology has been verified with the help of case studies. The method provides phases actually present at equilibrium, their quantities and compositions in each stage of the...
Valuation of dynamic reactive power support in multitransaction power systems
, Article European Transactions on Electrical Power ; Volume 17, Issue 1 , 2007 , Pages 61-79 ; 1430144X (ISSN) ; Vakilian, M ; Feuillet, R ; Hadj Said, N ; Sharif University of Technology
2007
Abstract
This paper presents a reactive power valuation method with regard to its effect on realization of MW transactions. The security constraint optimization model in which the objective function is maximization of transactions is solved by the genetic algorithm approach. The proposed scheme allocates a specific amount of MW transactions to each dynamic reactive power source. An index is introduced to derive VAr value from the calculated optimal parameters of power network. This index represents the system-wide effect of MVAr sources on MW transactions implementations. Application of proposed method has been illustrated using IEEE 30 and 14 bus test systems. Results are discussed and compared in...
Short term voltage-based risk assessment by incorporating reactive power adequacy
, Article Ain Shams Engineering Journal ; Volume 7, Issue 1 , 2016 , Pages 131-141 ; 20904479 (ISSN) ; Fotuhi Firuzabad, M ; Karimi, A ; Sharif University of Technology
Ain Shams University
2016
Abstract
A risk-based approach for short term security assessment with voltage stability constraint is presented in this paper. This approach includes voltage-stability considerations in reactive power adequacy assessment of a composite power system. The proposed method is based on probabilistic criteria because deterministic risk criteria do not define consistently the true risk in the system. For risk calculation, in this paper, load and parametric uncertainties and system contingencies are considered. Then the effects of uncertainties and contingencies on bus voltage violation are calculated. The required reactive power is determined based on the calculated voltage violation in order to maintain...
Predictive method for improving SVC speed in electric arc furnace compensation
, Article IEEE Transactions on Power Delivery ; Volume 22, Issue 1 , 2007 , Pages 732-734 ; 08858977 (ISSN) ; Parniani, M ; Sharif University of Technology
2007
Abstract
The ability of static VAr compensators (SVC) to reduce the flicker caused by electric arc furnaces and other variable VAr loads depends on their speed, which is limited by delays in reactive power measurement and thyristor ignition. In this paper, a predictive method is proposed to compensate the delay time and, hence, to improve the SVC performance. Previous samples of the load reactive power are used to predict its future values. Predicted VAr is then applied as a reference for reactive power compensation. © 2006 IEEE
Investigating the effects of reactive power on islanding detection
, Article 2004 International Conference on Power System Technology, POWERCON 2004, 21 November 2004 through 24 November 2004 ; Volume 2 , 2004 , Pages 1067-1071 ; 0780386108 (ISBN) ; Parniani, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
2004
Abstract
Distributed generation (DG) portion of power production is increasing more and more. DG poses different benefits and difficulties in a power system. Inadvertent islanding is a problem with DG which may cause health danger to line crew and can damage both DG and power system equipments. This paper investigates the effect of reactive power on ROCOF islanding detection method. Impacts of load power factor and load combination are studied using a sample test system. The paper offers a corrective method to cope with impacts of load reactive power. A way is suggested to locate DG such that the role of reactive power becomes a positive factor in islanding detection. © 2004 IEEE
A simultaneous method for phase identification and equilibrium calculations in reactive mixtures
, Article Chemical Engineering Research and Design ; Volume 89, Issue 10 , 2011 , Pages 1901-1908 ; 02638762 (ISSN) ; Saboohi, Y ; Sharif University of Technology
Abstract
Phase identification is an important aspect of flash calculations which can affect the phase and chemical equilibria. A new simultaneous approach for reactive mixtures, based on τ-method which relies on modification equation for mole fraction summation, is introduced in this paper. In the proposed methodology, phase identification and solution of governing equations can be performed simultaneously and effectively. In addition, prior knowledge of the number of phases in advance is not required. Present methodology has been verified with the help of case studies and results are discussed in the present paper. The results indicate that the present method gives us information about presence of...
A conceptual structure for value based assessment of dynamic reactive power support in power markets
, Article Electric Power Systems Research ; Volume 77, Issue 7 , 2007 , Pages 761-770 ; 03787796 (ISSN) ; Vakilian, M ; Feuillet, R ; Hadj Said, N ; Sharif University of Technology
2007
Abstract
This paper presents a practical reactive power valuation method, for the purpose of the reactive power pricing, in which the VAr value is decomposed into two components. These components are basically different from those already employed in the literature. Using a security constrained optimization model, the proposed scheme allocates two specific amounts of MW transactions to each generator as a dynamic reactive power source. One of these allocated amounts represents the contribution of the VAr resource to the shipment of active power, while the other one represents the contribution to the protection of the system against voltage instability. The final VAr value is derived using the...
Methods of Clearing Reactive Power Market and Cost Allocation in Pool Structure
, M.Sc. Thesis Sharif University of Technology ; Ehsan, Mehdi (Supervisor)
Abstract
Restructuring and privatization in power system such as any industry leads to better market operation and more social welfare. Since two decade the power system in many countries have changed from monopoly to free market. In a restructured network the technical and economical aspects should be considered together. Ancillary services are needed for any power system to be operated in an optimal and secure manner. Reactive power and voltage regulation is one of the most important ancillary services in the network. this service should be supplied by its providers through a competitive market and system operator determines the optimal dispatch among different bids. The cost of purchasing reactive...
Active and reactive power control of a DFIG using a combination of VSC with PSO
, Article World Applied Sciences Journal ; Volume 13, Issue 2 , 2011 , Pages 316-323 ; 18184952 (ISSN) ; Hashemnia, N ; Kashiha, A ; Sharif University of Technology
Abstract
Nowadays, application of renewable energies has taken a rapid trend. Wind energy is among those mostly used for this purpose. Doubly Fed Induction Generators (DFIG) are widely used in wind power plants due to several advantages such as partial rating converter, capability of decoupled active and reactive power control, etc. Application of a suitable control strategy is of great importance in wind power plants. In this paper, the parameters of a hybrid controller are calculated using Particle Swarm Optimization (PSO) subjected to satisfying the required criteria in output active and reactive powers of a DFIG. In the proposed system Direct Power Controller (DPC), Variable Structure Controller...
Effects of microsilica percentage amount on structure and compressive strength of reactive powder concrete (RPC)
, Article Journal of Engineering and Applied Sciences ; Volume 11, Issue 7 , 2016 , Pages 1502-1507 ; 1816949X (ISSN) ; Azizi, K ; Sharif University of Technology
Medwell Journals
Abstract
Reactive powder concrete is a new kind of powerful concrete which is called so because of tiny powder and pozzolanic materials as well as a lot of hydraulically active materials used in it and it has been presented by two French scientists in 1994. The aim of this study is to measure the possibility of producing powder concretes using local materials used in Asaluyeh Region. By calculating cement amount, water ratio to cement and optimal percentage of super plasticizer in this article, we start constructing six mix plans with different percentages of microsilica (0, 10, 15, 20, 30 and 40). Results show that 15% mix plan has the highest bending and compressive strength in three conditions of...
A numerical investigation of reactive air pollutant dispersion in urban street canyons with tree planting
, Article Atmospheric Pollution Research ; Volume 8, Issue 2 , 2017 , Pages 253-266 ; 13091042 (ISSN) ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Vegetation acts as a momentum and thermal sink, affecting the mixing of species and temperature-dependent constants of reaction rates. Numerical simulations were performed to investigate the effects of vegetation on the dispersion of reactive pollutants using a computational fluid dynamic (CFD) model coupled with NO-NO2-O3 photochemistry. Moreover, characteristics of temperature and flow fields were analyzed for different aspect ratios and leaf area densities. The results showed that flow is reversed in the presence of trees, and it enhances as leaf area density (LAD) increases; additionally, vegetation creates downward and vortex flows. The results also revealed that the dispersion of...
MVAR management using generator participation factors for improving voltage stability margin
, Article Journal of Applied Sciences ; Volume 9, Issue 11 , 2009 , Pages 2123-2129 ; 18125654 (ISSN) ; Sharif University of Technology
2009
Abstract
This study assesses the management of reactive power generation to improve the voltage stability margin using modal analysis technique. The simulation results show that after the optimal reactive power re-scheduling, the voltage stability margin of the system is improved and the active/reactive power losses are decreased. Improving the voltage stability margin of power system without adding new VAR (Volt Ampere Reactive) sources and changing the active power dispatch, is the most important advantage of proposed method. © 2009 Asian Network for Scientific Information
Enhanced decolorization of Reactive Blue 19 dye from synthetic textile wastewater through UV photolysis in alkaline conditions
, Article Environmental Engineering and Management Journal ; Volume 7, Issue 2 , 2008 , Pages 119-123 ; 15829596 (ISSN) ; Ghaneian, M ; Hashemian, S. J ; Mosavi, G ; Hajizadeh, E ; Sharif University of Technology
Gh. Asachi Technical University of Iasi
2008
Abstract
Laboratory scale experiments were conducted in order to investigate the photolysis of Reactive Blue 19 (RB 19) dye using UV as the irradiation source in alkaline solution. The effects of operating parameters such as, pH, initial dye concentration, UV dosage, hydrogen peroxide and oxygen have been evaluated. The results indicate that the UV photolysis process in alkaline solution is ideal for decolorizing of RB 19 and it can be taken as a starting step to establish the economical feasibility of the method for the decolorization of wastewater from textile industries
An approach to optimal dispatch of bilateral electricity contracts regarding voltage stability
, Article Power Plants and Power Systems Control 2006 ; Volume 39, Issue 7 , 2007 , Pages 65-70 ; 9780080466200 (ISBN) ; Ranjbar, A. M ; Mozafari, A ; Amraee, T ; Sharif University of Technology
Elsevier Ltd
2007
Abstract
This chapter proposes a methodology for optimal dispatch of bilateral electricity contracts, which may endanger the system voltage stability in light of short-term operational planning of a deregulated power system. In this framework the value that each owner of a transaction is willing to pay reflects how much the electricity contract is important to be implemented physically. The proposed model dispatches optimally the bilateral transactions regarding the prices offered by owners of bilateral contracts for reactive power and transmission capacity utilization in one hand and, the total operational costs of reactive power resources in the other hand. The model also includes the limits...
Modular verification of a component-based actor language
, Article Journal of Universal Computer Science ; Volume 11, Issue 10 , 2005 , Pages 1695-1717 ; 0958695X (ISSN) ; De Boer, F. S ; Movaghar, A ; Sharif University of Technology
2005
Abstract
Rebeca is an actor-based language for modeling concurrent and distributed systems as a set of reactive objects which communicate via asynchronous message passing. Rebeca is extended to support synchronous communication, and at the same time components are introduced to encapsulate the tightly coupled reactive objects which may communicate by synchronous messages. This provide us a language for modeling globally asynchronous and locally synchronous systems. Components interact only by asynchronous messages. This feature and also the eventdriven nature of the computation are exploited to introduce a modular verification approach in order to overcome the state explosion problem in model...
Model checking, automated abstraction, and compositional verification of Rebeca models
, Article Journal of Universal Computer Science ; Volume 11, Issue 6 , 2005 , Pages 1054-1082 ; 0958695X (ISSN) ; Movaghar, A ; Shali, A ; De Boer, F. S ; Sharif University of Technology
2005
Abstract
Actor-based modeling, with encapsulated active objects which communicate asynchronously, is generally recognized to be well-suited for representing concurrent and distributed systems. In this paper we discuss the actor-based language Rebeca which is based on a formal operational interpretation of the actor model. Its Java-like syntax and object-based style of modeling makes it easy to use for software engineers, and its independent objects as units of concurrency leads to natural abstraction techniques necessary for model checking. We present a front-end tool for translating Rebeca to the languages of existing model checkers in order to model check Rebeca models. Automated modular...
Graphene nanopores in broadband wide-angle optical cavity resonance absorbers
, Article Surfaces and Interfaces ; Volume 30 , 2022 ; 24680230 (ISSN) ; Akhavan, O ; Sharif University of Technology
Elsevier B.V
2022
Abstract
A cavity resonator containing graphene nanopores (GNPs), along with a metallic layer (Ag, as a reflector) and a dielectric layer (SiO2, as a spacer), has been proposed for broadband wide-angle absorption of light. The GNP/SiO2/Ag multilayers showed high significant increase in the absorption efficiency (with respect to the G/SiO2/Ag multilayer) in a broad spectral range (from ultra-violet (UV) and visible range to near-infrared (NIR)), due to the cavity resonance and absorptions induced by the oxygen-containing functional groups formed around the nanopores of graphene. The dependences of the cavity resonance absorption on the quality of the GNP layer, dimension of the cavity and the incident...
Experimental study and correlation for mass transfer coefficient in the pilot plant multistage column with the presence of molybdenum
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 41, Issue 2 , 2022 , Pages 544-554 ; 10219986 (ISSN) ; Torab Mostaedi, M ; Outokesh, M ; Torkaman, R ; Asadollahzadeh, M ; Sharif University of Technology
Iranian Institute of Research and Development in Chemical Industries
2022
Abstract
In the present work, multistage extraction column performance for reactive separation of molybdenum from the leach aqueous phase by using D2EHPA and TBP in kerosene was investigated by using the axial diffusion model. The variation of volumetric overall mass transfer coefficients based on continuous phases at various operating conditions was obtained. By considering the chemical reaction conditions, the experimental data indicate that the volumetric overall mass transfer coefficients increase with an enhancement in rotor speed and continuous and dispersed phase flow rates. According to the sensitivity analysis, the rotor speed and flow rate of the dispersed phase have more influence on...
Optimal reactive power dispatch for improving voltage stability margin using a local voltage stability index
, Article Energy Conversion and Management ; Volume 59 , 2012 , Pages 66-73 ; 01968904 (ISSN) ; Vanouni, M ; Parniani, M ; Sharif University of Technology
2012
Abstract
Management of reactive power resources is vital for stable and secure operation of power systems in the view point of voltage stability. This paper deals with the management of on-load tap changers (OLTCs) and dynamic VAR sources (including synchronous generators, synchronous condensers, and shunt reactive power compensators) to improve voltage stability margin (VSM) of power systems. This problem is usually called optimal reactive power dispatch (ORD) in the literature. The main contribution of the paper is to introduce a new objective function for the ORD problem. The proposed objective function is derived based on a local voltage stability index, called DSY, and has a strong correlation...
Optimal reactive power dispatch in a joint active / reactive market model
, Article 2006 IEEE PES Transmission and Distribution Conference and Exposition: Latin America, TDC'06, Caracas, 15 August 2006 through 18 August 2006 ; 2006 ; 1424402883 (ISBN); 9781424402885 (ISBN) ; Amraee, T ; Ranjbar, A. M ; Mirjafari, M ; Shirani, A. R ; Sharif University of Technology
2006
Abstract
The participants in auction-based electricity markets need to take part in a competition way, which operates, based on the concept of supply and demand theory to buy or sell the electricity. However, to have a feasible market solution, reactive power services are necessary to support the transmission of power from generation to end-users. This paper presents a methodology for optimal reactive power procurement, consistent with the auction-based electricity market mechanism. The proposed reactive power market is run in subsequence of the primary electricity market, allowing active power modification in light of available transmission capacity and reactive power resources. The IEEE 30-bus test...