Search for: electric-load-flow
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    Value-based reserve market settlement

    , Article IET Generation, Transmission and Distribution ; Volume 10, Issue 9 , 2016 , Pages 2216-2224 ; 17518687 (ISSN) Nouri, A ; Hosseini, S. H ; Sharif University of Technology
    Institution of Engineering and Technology  2016
    The main focus of this study is on reserve market settlement in an electricity market with marginal pricing scheme as the pricing mechanism. Following a day-ahead market clearing, the marginal prices are found using the appropriate Lagrange multipliers as the bi-products of the optimisation process. The payments to energy and reserve providers can then be found based on these prices. However, it is hard to find an appropriate settlement scheme that provides the fair and justifiable consumer payments based on marginal pricing scheme considering the actual reserve functions in power systems. In this study, a reserve marginal pricing that is based on a proper reserve marginal price definition... 

    Autonomous operation of a hybrid AC/DC microgrid with multiple interlinking converters

    , Article IEEE Transactions on Smart Grid ; Volume 9, Issue 6 , 2018 , Pages 6480-6488 ; 19493053 (ISSN) Peyghami, S ; Mokhtari, H ; Blaabjerg, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Applying conventional dc-voltage-based droop approaches for hybrid ac/dc microgrids interconnected by a single interlinking converter (IC) can properly manage the power flow among ac and dc subgrids. However, due to the effect of line resistances, these approaches may create a circulating power as well as overstressing the ICs in the case of employing multiple ICs for interconnecting the ac and dc subgrids. This paper proposes an autonomous power sharing approach for hybrid microgrids interconnected through multiple ICs by introducing a superimposed frequency in the dc subgrid. Hence, a suitable droop approach is presented to manage the power among the dc and ac sources as well as ICs. The... 

    A linear AC power flow model for unbalanced multi-phase distribution networks based on current injection equations

    , Article IEEE Transactions on Power Systems ; Volume 36, Issue 4 , 2021 , Pages 3806-3809 ; 08858950 (ISSN) Heidari-Akhijahani, A ; Safdarian, A ; Vrakopoulou, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    A realistic and practicable modeling of unbalanced distribution networks (DNs) is the missing link in most studies undertaken in these networks, e.g., optimal power flow (OPF), energy markets, etc. To address the issue, this letter proposes an unbalanced linear three-phase four-wire power flow (PF) model based on current injection equations at nodes. Also, the ZIP representation is considered for loads. The model can be easily generalized for unbalanced three-wire networks with minor changes and assumptions. Hence, the scope of the proposed method can be extended to cover both low-voltage and medium-voltage DNs. The performance of the proposed model is verified through simulations on two... 

    A decomposed solution to multiple-energy carriers optimal power flow

    , Article IEEE Transactions on Power Systems ; Vol. 29, issue. 2 , March , 2014 , p. 707-716 ; ISSN: 8858950 Moeini-Aghtaie, M ; Abbaspour, A ; Fotuhi-Firuzabad, M ; Hajipour, E ; Sharif University of Technology
    Presence of energy hubs in the future vision of energy networks creates a great opportunity for system planners and operators to move towards more efficient systems. The role of energy hubs as the intermediate in multi-carrier energy (MCE) systems calls for a generic framework to study the new upcoming technical as well as economical effects on the system performance. In response, this paper attempts to develop a general optimization and modeling framework for coupled power flow studies on different energy infrastructures. This, as a large-scale nonlinear problem, is approached through a robust optimization technique, i.e., multi-agent genetic algorithm (MAGA). The proposed procedure... 

    Security constrained unit commitment with flexibility in natural gas transmission delivery

    , Article Journal of Natural Gas Science and Engineering ; Volume 27, Part 2 , November 2015 , 2015 , Pages 632–640 ; 18755100 (ISSN) Badakhshan, S ; Kazemi, M ; Ehsan, M ; Sharif University of Technology
    Elsevier  2015
    This paper presents a formulation of fuzzy optimization for uncertainties in natural gas in fuel constraints for hourly individual unit and total unit fuel consumptions. Security Constrained Unit Commitment (SCUC) is usually a mixed integer programming and gas load flow has a non-linear equation a genetic algorithm is proposed to solve natural gas transmission network. A fuzzy mixed integer programming optimization is briefly discussed and adapted to deal with security constrained unit commitment schedule. Finally, two case studies are investigated (IEEE 6-bus system with 7-node natural gas transmission grid and the IEEE 118-bus power system linked with 14-node gas transmission test system)... 

    Smart power management of DC microgrids in future milligrids

    , Article 2016 18th European Conference on Power Electronics and Applications, EPE 2016 ECCE Europe, 5 September 2016 through 9 September 2016 ; 2016 ; 9789075815245 (ISBN) Peyghami Akhuleh, S ; Mokhtari, H ; Davari, P ; Loh, P. C ; Blaabjerg, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    In this paper a novel droop approach for power management in low voltage dc MicroGrids (MGs) based on a master-slave concept is presented. A virtual frequency is injected by a master unit, which is proportional to its output power. Other slave units determine their output power according to the corresponding frequency based droop characteristics. Unlike the dc voltage-droop methods, the proposed virtual frequency-droop approach can be smartly applied for proportional power management among the energy units and loads as well as adding zero net energy capability to the MG. Both power flow and energy flow can be performed without utilizing an extra communication system. Simulation results... 

    Application of bat optimization algorithm in optimal power flow

    , Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 793-798 ; 9781467387897 (ISBN) Delkhosh Abatari, H ; Seyf Abad, M. S ; Seifi, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    In this paper, Bat Algorithm is proposed to solve the Optimal Power Flow (OPF) problem. The approach employs a Meta heuristic optimization algorithm called bat optimization algorithm to determine the optimal settings of control variables of OPF problem. The performance of proposed method examined on the IEEE 9, 14, 30 and 57-buses test systems with fuel cost minimization as the objective function. The numerical results are compared to those of Particle Swarm Optimization (PSO), Harmony Search (HS) and Cuckoo algorithms. Simulation results obtained from the proposed approach demonstrate that this method provide effective and robust high-quality answer for the OPF problem. © 2016 IEEE  

    Multi-body simulation of a flapping-wing robot using an efficient dynamical model

    , Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 38, Issue 1 , 2016 , Pages 133-149 ; 16785878 (ISSN) Jahanbin, Z ; Selk Ghafari, A ; Ebrahimi, A ; Meghdari, A ; Sharif University of Technology
    Springer Verlag 
    The aim of this article is to present an efficient dynamical model for simulating flapping robot performance employing the bond graph approach. For this purpose, the complete constitutive elements of the system under investigation, including the main body and accessories, flapping mechanism, flexible wings and propulsion system consisting of a battery, DC motors and gear boxes, are considered. A complete model of the system was developed appending bond graph models of the subsystems together utilizing appropriate junctions. The wings were also modeled using ANSYS only for an initial evaluation. Moreover, a computer model was developed employing the block-oriented structure of Simulink in... 

    A linear model for AC power flow analysis in distribution networks

    , Article IEEE Systems Journal ; Volume 13, Issue 4 , 2019 , Pages 4303-4312 ; 19328184 (ISSN) Gharebaghi, S ; Safdarian, A ; Lehtonen, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    The standard power flow (PF) equations are nonlinear, and their integration in the optimal PF (OPF) problem leads to a nonconvex hard-to-solve model. To attack the issue, this paper presents a linear PF model wherein real and imaginary parts of nodal voltages are variables. In the model, loads are interpreted via ZIP model including constant impedance, constant current, and constant power components. To preserve linearity of the model, the complex power is represented via a quadratic function of the hosting node voltage. The function coefficients are derived via curve fitting approaches. Since the model is linear, its solution does not need repetition and can be effectively integrated in the... 

    Sensitivity-based generators redispatch to improve electromechanical mode damping considering transmission lines resistance

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 491-496 ; 9781728115085 (ISBN) Setareh, M ; Parniani, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    This paper proposes a novel formula to calculate sensitivities of electromechanical modes to generators active power changes. Quadratic eigenvalue problem is applied to construct the framework of the proposed formula. Sensitivity factors are calculated using power system model parameters and power flow variables, which can be either obtained via state estimation or measured directly by phasor measurement units. The 39-bus New England power system is used to verify performance of the proposed method  

    Intelligent topology-oriented load shedding scheme in power systems

    , Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 652-656 ; 9781728115085 (ISBN) Zare, F ; Ranjbar, A ; Faghihi, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Load shedding is a prevalent emergency control designed to prevent system blackouts. The higher complexity and lower predictability of modern power systems makes it difficult to rely on conventional load shedding schemes which shed loads in pre-defined steps without sufficient consideration of the actual system characteristics and the disturbance situations. In case of large disturbances, the power system stability can be improved by optimal load shedding in more effective load buses. Proposed scheme utilizes improved Power Flow Tracing method to determine the amount and location of load drops considering power system constraints. Numerical simulations conducted on IEEE 39 bus standard test... 

    The impact of demand response programs on UPFC placement

    , Article Turkish Journal of Electrical Engineering and Computer Sciences ; Volume 27, Issue 6 , 2019 , Pages 4624-4639 ; 13000632 (ISSN) Sharifi Nasab Anari, A ; Ehsan, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    Turkiye Klinikleri  2019
    Demand response (DR) and flexible AC transmission system (FACTS) devices can be effectively used for congestion management in power transmission systems. However, demand response program (DRP) implementation can itself affect the optimum location of FACTS devices, which is one of the main issues in power system planning. This paper investigates the impact of DRPs on unified power flow controller (UPFC) placement. The harmony search algorithm is employed to determine the optimum locations and parameter setting of UPFC in a long-term framework. The optimization problem is solved with different objectives including generation and congestion cost reduction, as well as loss reduction. In this... 

    Robust linear model for multi-period AC optimal power flow

    , Article IET Generation, Transmission and Distribution ; Volume 14, Issue 13 , 2020 , Pages 2535-2548 Heidarabadi, H ; Pourahmadi, F ; Hossieni, S. H ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    In the near future power systems, efficient management of uncertainties with considering the system constraints without any simplification will be a challenge for system operators. Considering AC constraints leads to providing more accurate schedule of generating units, which can have a significant impact on the reduction of operating costs. Although numerous studies have been done to convexify AC optimal power flow constraints, most of the models are non-linear, which can be intractable for large-scale systems. In this study, a novel linear robust AC model is introduced using a combination of the quadratic convex relaxation (QCR) and the Frank-Wolfe algorithm for linearising the AC... 

    Intelligent topology-oriented LS scheme in power systems integrated with high wind power penetration

    , Article IET Generation, Transmission and Distribution ; Volume 14, Issue 9 , 2020 , Pages 1684-1693 Zare, F ; Ranjbar, A ; Faghihi, F ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Load shedding (LS) is one of the most important protection schemes to prevent system blackout. In the case of largedisturbances, optimal LS in appropriate buses can effectively maintain the system stability. The higher complexity and lowerpredictability of modern power systems with high wind power penetration make it difficult to rely on conventional LS schemes,which shed a fixed, predetermined amount of load regardless of disturbance location. This study presents an intelligent LSscheme based on synchrophasor measurements that are adapted to both disturbance size and power system inertia. Theproposed scheme utilises improved power flow tracing method to determine the amount and location of... 

    Optimal power flow solution by a modified particle swarm optimization algorithm

    , Article Proceedings of the Universities Power Engineering Conference, 1 September 2008 through 4 September 2008, Padova ; 2008 ; 9788889884096 (ISBN) Hajian Hoseinabadi, H ; Hosseini, H ; Hajian, M ; Sharif University of Technology
    This paper presents a modified particle swarm optimization (MPSO) algorithm for solving the optimal power flow (OPF) problems. The main distinction of this approach is in using particle's worth experience in stead of the best previous experience. The proposed approach is evaluated on the IEEE 30-bus test system which minimizes the total fuel cost considering operational constraints such as power flow equations, transmission flow limits, bus voltages and reactive power of generators. The results obtained using the proposed approach are compared with results of other optimization methods  

    An approach to optimal dispatch of bilateral electricity contracts regarding voltage stability

    , Article IFAC Proceedings Volumes (IFAC-PapersOnline) ; Volume 5, Issue PART 1 , 2006 , Pages 65-70 ; 14746670 (ISSN); 9783902661081 (ISBN) Mozafari, B ; Ranjbar, A. M ; Mozafari, A ; Amraee, T ; Sharif University of Technology
    IFAC Secretariat  2006
    This paper 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 will reflect 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... 

    A comprehensive framework for optimal planning of competing energy hubs based on the game theory

    , Article Sustainable Energy, Grids and Networks ; Volume 27 , 2021 ; 23524677 (ISSN) Farshidian, B ; Rajabi Ghahnavieh, A ; Sharif University of Technology
    Elsevier Ltd  2021
    The concept of energy hub has been used recently to study multi-carrier energy systems. A model has been proposed in this paper for planning multi-hub energy system considering the competition between the hubs. The energy hubs are interconnected by a power grid. Hubs supply the demands for heat and electricity using various technologies and access to several energy carriers. To this aim, load zones were used to incorporate demand profiles for both heat and electricity in the different seasons of the year. Supplying the demand most cost-effectively is the objective function of each hub. These hubs select the optimum strategy separately in a competitive space. The power grid is owned by... 

    Smart transmission expansion planning based on unconventional high surge impedance loading line designs

    , Article 2021 IEEE Power and Energy Society Innovative Smart Grid Technologies Conference, ISGT 2021, 16 February 2021 through 18 February 2021 ; 2021 ; 9781728188973 (ISBN) Lotfi, A ; Ghassemi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    This paper introduces a new concept that we call smart transmission expansion planning (TEP) based on unconventional high surge impedance Loading (HSIL) line designs that will revolutionize power delivery. To date, these two areas (TEP and transmission line design) have been conducted separately. For TEP, planners use the electrical parameters of a few standard conventional line designs to study planning scenarios, and then, the final candidate line is constructed. In such a sequence, cost-effective scenarios often do not meet the technical criteria of load flow. This paper will demonstrate that this sequence can be overturned; namely, a transmission expansion planner can get optimal line... 

    Method of combined static and dynamic analysis of voltage collapse in voltage stability assessment

    , Article 2005 IEEE/PES Transmission and DistributionConference and Exhibition - Asia and Pacific, Dalian, 15 August 2005 through 18 August 2005 ; Volume 2005 , 2005 , Pages 1-6 ; 0780391144 (ISBN); 9780780391147 (ISBN) Hasani, M ; Parniani, M ; Sharif University of Technology
    Different analysis methods have been used for voltage stability assessment. In comparison with static analysis methods, little work has been done on dynamic analysis of large interconnected power systems. Voltage instability can be studied effectively with a combination of static approaches and time simulations. This paper discusses voltage stability assessment using mixed static and dynamic techniques. Using static methods, a voltage stability based ranking is carried out to specify faint buses, generators and links in power system. The system is analyzed for most severe conditions. Then, time domain simulation is performed for the conditions determined by voltage instability ranking. The... 

    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 Aien, M ; Fotuhi-Firuzabad, M ; Aminifar, F ; Sharif University of Technology
    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...