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uncertainty-analysis
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A new Optimization Approach for Solving Well Placement Problem under Uncertainty Assessment
, M.Sc. Thesis Sharif University of Technology ; Massihi, Mohsen (Supervisor) ; Roosta Azad, Reza (Supervisor)
Abstract
Determining the best location for new wells is a complex problem that depends on reservoir and fluid properties, well and surface equipment specifications, and economic criteria. Various approaches have been proposed for this problem. Among those, direct optimization using the simulator as the evaluation function, although accurate, is in most cases infeasible due to the number of simulations required. This study proposes a hybrid optimization technique (HGA) based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. Hybridization of the GA with these helper methods introduces hill-climbing into the stochastic search and also makes use...
A Real Option Model to Evaluate Investments in Combined Heat and Power (CHP)Projects
, M.Sc. Thesis Sharif University of Technology ; Haj Kazem Kashani, Hamed (Supervisor)
Abstract
Cogeneration technologies such as Combined Heat and Power (CHP) have promising features for providing the electrical energy that various industries require while reducing the emissions and other environmental impacts of these industries. Investments in CHP systems require substantial implementation costs followed by a relatively long period of recovering the invested capital through savings in utilities bills. Appropriate timing of CHP system investments can reduce capital expenses and enhance returns on investments. An appropriate investment valuation method is needed to identify the appropriate time to implement a given CHP system and to find the values of properly scheduled investments....
Uncertainty Analysis and Inverse Modeling of Seawater Intrusion in Coastal Aquifers
, Ph.D. Dissertation Sharif University of Technology ; Ataei Ashtiani, Behzad (Supervisor)
Abstract
Groundwater is the primary source of freshwater in many coastal areas and small islands around the world. The most important hazard to groundwater quality in coastal aquifers is seawater intrusion (SWI) resulting from over pumping, prolonged drought conditions and sea level rise due to climate change impacts. Numerical models of SWI are an important tool in the management of coastal aquifers. However, numerical modeling of SWI is one of the most challenging problems in groundwater hydrology. One of the reasons for the challenging nature of SWI numerical modeling is the relatively large level of uncertainty associated with the estimation of the model input parameters. This study focused on...
Drought Uncertainty Analysis under Climate Change Using Copula
, M.Sc. Thesis Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
The classical approaches of drought analysis are performed using historical records and univariate statistical methods. In the use of historical records it is assumed that statistical characteristics of droughts will be exactly repeated in the future (the assumption of stationarity) and in the use of univariate methods it is assumed that drought variables (e.g. duration and severity) are independent; while on the contrary, global warming changes long-term climate patterns, which is called climate change, and also drought variables have significant correlation. Thus, results of classical approaches of drought analysis have uncertainties.The primary objective of this thesis is to propose an...
Safety Assessment for H2S Releasing in Arak Heavy Water Factory (GS(03) Plant) Using Probabilistic Safety Assessment Method (PSA)
, M.Sc. Thesis Sharif University of Technology ; Ghofrani, Mohammad Bagher (Supervisor)
Abstract
In general, release of hazardous gas in chemical process plants could be due to two reasons. First is failures due to degradation of components that have inventory of hazardous gas in standard process conditions, and the second is deviation of system from standard process conditions because of different failure modes of related components, e.g. controller equipments. The purpose of this study is, calculating the probability of H2S releasing in GS(03) plant of Arak Heavy Water factory, using PSA methods and its risk assessment. At First, fifteen groups of initiating events were identified with Hazop study for desired system. Then, for calculating the frequency of each event, the combination...
Planning for Groundwater Sustainable Management Case Study: Nishapur Plain
, Ph.D. Dissertation Sharif University of Technology ; Abrishamchi, Ahmad (Supervisor)
Abstract
In recent years, an increasing demand of water on one hand and over-exploitation of groundwater resources on the other hand lead to the unsustainability of these resources worldwide. Due to arid and semi-arid climate in Iran, groundwater resources play an essential role in food production, as well as domestic and industrial water supply. Increasing population, scarcity of surface water resources, and effects of worldwide and regional climate change have resulted in over-exploitation of groundwater resources in the country and threatens the water security of the nation. The present study aims to estimate groundwater sustainable yield, examine effects of spatial and temporal scale, water...
Power system dynamic state estimation with synchronized phasor measurements
, Article IEEE Transactions on Instrumentation and Measurement ; Vol. 63, issue. 2 , 2014 , p. 352-363 ; ISSN: 189456 ; Shahidehpour, M ; Fotuhi-Firuzabad, M ; Kamalinia, S ; Sharif University of Technology
Abstract
The dynamic state estimation (DSE) applied to power systems with synchrophasor measurements would estimate the system's true state based on measurements and predictions. In this application, as phasor measurement units (PMUs) are not deployed at all power system buses, state predictions would enhance the redundancy of DSE input data. The significance of predicted and measured data in DSE is affected by their confidence levels, which are inversely proportional to the corresponding variances. In practice, power system states may undergo drastic changes during hourly load fluctuations, component outages, or network switchings. In such conditions, the inclusion of predicted values could degrade...
Probabilistic optimal power flow in correlated hybrid wind-photovoltaic power systems
, Article IEEE Transactions on Smart Grid ; Vol. 5, issue. 1 , 2014 , p. 130-138 ; ISSN: 19493053 ; Fotuhi-Firuzabad, M ; Rashidinejad, M ; Sharif University of Technology
Abstract
As a matter of course, the unprecedented ascending penetration of distributed energy resources (DERs), mainly harvesting renewable energies (REs), is concomitant with environmentally friendly concerns. This type of energy resources are innately uncertain and bring about more uncertainties in the power system, consequently, necessitates probabilistic analyses of the system performance. Moreover, the uncertain parameters may have a considerable level of correlation to each other, in addition to their uncertainties. The two point estimation method (2PEM) is recognized as an appropriate probabilistic method in small scale or even medium scale problems. This paper develops a new methodology for...
Probabilistic power flow of correlated hybrid wind-photovoltaic power systems
, Article IET Renewable Power Generation ; Vol. 8, issue. 6 , 2014 , p. 649-658 ; ISSN: 17521416 ; Khajeh, M. G ; Rashidinejad, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
Abstract
As a matter of course, the unprecedented ascending penetration of distributed energy resources, mainly harvesting renewable energies such as wind and solar, is concomitant with environmentally friendly concerns. This type of energy resources are innately uncertain and bring about more uncertainties in the power system context, consequently, necessitates probabilistic analysis of the system performance. Moreover, the uncertain parameters may have a considerable level of correlation to each other, in addition to their uncertainties. The two point estimation method (2PEM) is recognised as an appropriate probabilistic method. This study proposes a new methodology for probabilistic power flow...
Real time probabilistic power system state estimation
, Article International Journal of Electrical Power and Energy Systems ; Vol. 62, issue , 2014 , p. 383-390 ; ISSN: 1420615 ; Rashidinejad, M ; Kouhi, S ; Fotuhi-Firuzabad, M ; Ravadanegh, S.N ; Sharif University of Technology
Abstract
Smartening of contemporaneous power delivery systems in conjunction with the increased penetration of renewable energies (REs), change the way to energize consumers who are willing to maximize their utility from energy consumption. However, there is a high degree of uncertainty in the electricity markets of such systems. Moreover, the unprecedented ascending penetration of distributed energy resources (DERs) mainly harvesting REs is a direct consequence of environmentally friendly concerns. This type of energy resources brings about more uncertainties into power system operation resulting in, necessitates probabilistic analysis of the system performance. In the smarter power markets,...
On possibilistic and probabilistic uncertainty assessment of power flow problem: A review and a new approach
, Article Renewable and Sustainable Energy Reviews ; Vol. 37 , 2014 , p. 883-895 ; ISSN: 13640321 ; Rashidinejad, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
Abstract
As energy resource planning associated with environmental consideration are getting more and more challenging all around the world, the penetration of distributed energy resources (DERs) mainly those harvesting renewable energies (REs) ascend with an unprecedented rate. This fact causes new uncertainties to the power system context; ergo, the uncertainty analysis of the system performance seems necessary. In general, uncertainties in any engineering system study can be represented probabilistically or possibilistically. When sufficient historical data of the system variables is not available, a probability density function (PDF) might not be defined, while they must be represented in another...
Unscented transformation-based probabilistic optimal power flow for modeling the effect of wind power generation
, Article Turkish Journal of Electrical Engineering and Computer Sciences ; Vol. 21, issue. 5 , 2013 , p. 1284-1301 ; ISSN: 13000632 ; Fotuhi-Firuzabad, M ; Aminifar, F ; Sharif University of Technology
Abstract
The unprecedented increasing penetration of distributed energy resources, mainly harvesting renewable energies, is a direct result of environmental concerns. These types of energy resources bring about more uncertainties in the power system and, consequently, necessitate probabilistic analyses of the system performance. This paper develops a new approach for probabilistic optimal power flow (P-OPF) by adapting the unscented transformation (UT) method. The heart of the proposed method lies in how to produce the sampling points. Appropriate sample points are chosen to perform the P-OPF with a high degree of accuracy and less computational burden in comparison with the features of other...
Probabilistic load flow in correlated uncertain environment using unscented transformation
, Article IEEE Transactions on Power Systems ; Vol. 27, issue. 4 , 2012 , p. 2233-2241 ; ISSN: 08858950 ; Fotuhi-Firuzabad, M ; Aminifar, F ; Sharif University of Technology
Abstract
As a matter of course, the unprecedented ascending penetration of distributed energy resources, mainly harvesting renewable energies, is a direct consequence of environmental concerns. This type of energy resource brings about more uncertainties in power system operation and planning; consequently, it necessitates probabilistic analyses of the system performance. This paper develops a new approach for probabilistic load flow (PLF) evaluation using the unscented transformation (UT) method. The UT method is recognized as a powerful approach in assessing stochastic problems with/without correlated uncertain variables. The capability of the UT method in modeling correlated uncertain variables is...
Reliability modeling of PMUs using fuzzy sets
, Article IEEE Transactions on Power Delivery ; Vol. 25, issue. 4 , 2010 , p. 2384-2391 ; ISSN: 8858977 ; Bagheri-Shouraki, S ; Fotuhi-Firuzabad, M ; Shahidehpour, M ; Sharif University of Technology
Abstract
Probabilistic analyses of a wide-area measurement system (WAMS) would require equivalent reliability models for its components which include phasor measurement units (PMUs). In this paper, the reliability modeling of PMU is proposed and the proposed model is extended to consider options for the PMU hardware. The Markov process is employed to analyze the proposed model and to present an equivalent two-state model of PMUs. Reliability parameters of PMU are estimated with major difficulties associated with limited and uncertain data. In this paper, uncertainties are taken into account to achieve more realistic estimates of PMU characteristics. Fuzzy sets along with reliability analyses and...
A comparison between the minimum-order & full-order observers in robust control of the air handling units in the presence of uncertainty
, Article Energy and Buildings ; Volume 91 , 15 March , 2015 , Pages 115-130 ; ISSN: 3787788 ; Moradi, H ; Alasty, A ; Sharif University of Technology
Abstract
Control of the air-handling units (AHU) is required to maintain satisfactory comfort conditions with low energy consumption. In the case of failure in sensor fusion systems of AHUs, full-order observers can be used as the supportive tool to provide an acceptable estimation of state variables. In this paper, a multivariable nonlinear model of the AHU is considered in the presence of uncertainties. The indoor temperature and relative humidity are controlled via manipulation of valve positions of air and cold water flow rates. In proposed hybrid control system, full and minimum-order observers are designed for the estimation of indoor temperature and relative humidity. Also, a regulator for...
Using sliding mode control to adjust drum level of a boiler unit with time varying parameters
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis ; Vol. 5 , 2010 , pp. 29-33 ; ISBN: 9780791849194 ; Bakhtiari-Nejad, F ; Saffar-Avval, M ; Alasty, A ; Sharif University of Technology
Abstract
Stable control of water level of drum is of great importance for economic operation of power plant steam generator systems. In this paper, a linear model of the boiler unit with time varying parameters is used for simulation. Two transfer functions between drum water level (output variable) and feed-water and steam mass rates (input variables) are considered. Variation of model parameters may be arisen from disturbances affecting water level of drum, model uncertainties and parameter mismatch due to the variant operating conditions. To achieve a perfect tracking of the desired drum water level, two sliding mode controllers are designed separately. Results show that the designed controllers...
History matching of naturally fractured reservoirs based on the recovery curve method
, Article Journal of Petroleum Science and Engineering ; Vol. 126, issue , February , 2015 , p. 211-221 ; ISSN: 09204105 ; Masihi, M ; Heinemann, Z. E ; Ghazanfari, M. H ; Sharif University of Technology
Abstract
The discrete fracture network (DFN) and Multiple-Continua concept are among the most widely used methods to model naturally fractured reservoirs. Each faces specific limitations. The recently introduced recovery curve method (RCM) is believed to be a compromise between these two current methods. In this method the recovery curves are used to determine the amount of mass exchanges between the matrix and fracture mediums. Two recovery curves are assigned for each simulation cell, one curve for gas displacement in the presence of the gravity drainage mechanism, and another for water displacement in the case of the occurrence of the imbibition mechanism. These curves describe matrix-fracture...
Random walk-percolation-based modeling of two-phase flow in porous media: Breakthrough time and net to gross ratio estimation
, Article Physica A: Statistical Mechanics and its Applications ; Vol. 406, issue , July , 2014 , p. 214-221 ; ISSN: 03784371 ; Masihi, M ; Ghaedi, M ; Sharif University of Technology
Abstract
Fluid flow modeling in porous media has many applications in waste treatment, hydrology and petroleum engineering. In any geological model, flow behavior is controlled by multiple properties. These properties must be known in advance of common flow simulations. When uncertainties are present, deterministic modeling often produces poor results. Percolation and Random Walk (RW) methods have recently been used in flow modeling. Their stochastic basis is useful in dealing with uncertainty problems. They are also useful in finding the relationship between porous media descriptions and flow behavior. This paper employs a simple methodology based on random walk and percolation techniques. The...
Utilization of percolation approach to evaluate reservoir connectivity and effective permeability: A case study on North Pars gas field
, Article Scientia Iranica ; Vol. 18, issue. 6 , December , 2011 , p. 1391-1396 ; ISSN: 10263098 ; Masihi, M ; Pishvaie, M ; Shojaei, A ; King, P. R ; Sharif University of Technology
Abstract
Reservoir characterization, especially during early stages of reservoir life, is very uncertain, due to the scarcity of data. Reservoir connectivity and permeability evaluation is of great importance in reservoir characterization. The conventional approach to addressing this is computationally very expensive and time consuming. Therefore, there is a great incentive to produce much simpler alternative methods. In this paper, we use a statistical approach called the percolation theory, which considers a hypothesis wherein the reservoir can be split into either permeable (i.e. sand/fracture) or impermeable flow units (i.e. shale/matrix), and assumes that the connectivity of permeability...
State-of-the-art least square support vector machine application for accurate determination of natural gas viscosity
, Article Industrial and Engineering Chemistry Research ; Vol. 53, issue. 2 , 2014 , pp. 945-958 ; ISSN: 08885885 ; Arabloo, M ; Shokrollahi, A ; Zargari, M. H ; Ghazanfari, M. H ; Sharif University of Technology
Abstract
Estimation of the viscosity of naturally occurring petroleum gases is essential to provide more accurate analysis of gas reservoir engineering problems. In this study, a new soft computing approach, namely, least square support vector machine (LSSVM) modeling, optimized with a coupled simulated annealing technique was applied for estimation of the natural gas viscosities at different temperature and pressure conditions. This model was developed based on 2485 viscosity data sets of 22 gas mixtures. The model predictions showed an average absolute relative error of 0.26% and a correlation coefficient of 0.99. The results of the proposed model were also compared with the well-known predictive...