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Total 36 records

    Modeling, control and islanding detection of microgrids with passive loads

    , Article Proceedings of EPE-PEMC 2010 - 14th International Power Electronics and Motion Control Conference, 6 September 2010 through 8 September 2010 ; September , 2010 , Pages T11107-T11112 ; 9781424478545 (ISBN) Popov, M ; Karimi, H ; Nikkhajoei, H ; Terzija, V ; Sharif University of Technology
    2010
    Abstract
    This paper presents a control scheme for microgrids with passive loads. The existing control techniques for distributed generation systems are designed to operate either in the grid-connected or in the islanded mode. In the grid-connected mode of operation, a currentcontrolled scheme based on d-q variables is used for the regulation of real and reactive powers of the converter. In the islanded mode of operation, the converter is controlled in the voltage-controlled mode. This paper deals with the modeling of both control schemes. Furthermore, reconnection from the islanded mode to the grid-connected mode based on the use of adequate Phase-Locked Loops (PLLs) has been demonstrated  

    An analytical framework for operational reliability studies of highly wind integrated power systems

    , Article 2016 International Conference on Probabilistic Methods Applied to Power Systems, PMAPS 2016 - Proceedings, 16 October 2016 through 20 October 2016 ; 2016 ; 9781509019700 (ISBN) Parvini, Z ; Abbaspour, A ; Fotuhi Firuzabad, M ; Moeini Aghtaie, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    This paper presents a new framework for evaluating contribution of wind farms in operational reliability level of power systems. In this regard, at first, it provides a short-term analytical model well designed to represent intermittent and uncertain nature of wind power. Combining the attained multi-state model of wind farms with the other committed generating units, operational risk of the system is evaluated. The concept of Pennsylvania-New Jersey-Maryland (PJM), previously developed to assess the short-term/mid-term reliability of conventional generating units, is revisited in this paper to more practically incorporate wind farms in reliability studies of the power system. The proposed... 

    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
    Abstract
    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... 

    Identification of external power system linear dynamic equivalents as MIMO feedback blocks for the study system

    , Article International Journal of Emerging Electric Power Systems ; Volume 8, Issue 5 , 21 Nov. 2007 , 2007 ; 1553779X (ISSN) Hamed Shakouri, G ; Ranjbar, A. M ; Lesani, H ; Radmanesh, H ; Sharif University of Technology
    2007
    Abstract
    The necessity of dynamic equivalents for power system analysis has been well known since the expansion of large interconnected power networks, and has been discussed during the last decades. The present paper proposes a new method for constructing dynamic equivalents of power systems. In this method, at the first step the "study system" is modeled completely via a single machineinfinite bus modeling procedure. Then the "external system" is identified as a MIMO feedback block of this model in such a manner that can include dynamic effects of the latter on the behavior of the former. The method is successfully experimented on a part of the Iranian southern network. Copyright © 2007 The... 

    Reliability study of HV substations equipped with the fault current limiter

    , Article IEEE Transactions on Power Delivery ; Vol. 27, issue. 2 , 2012 , p. 610-617 ; ISSN: 8858977 Fotuhi-Firuzabad, M ; Aminifar, F ; Rahmati, I ; Sharif University of Technology
    Abstract
    Of particular interest to restrict the short-circuit level of interconnected power systems is to exploit fault current limiter (FCL) technologies. FCLs let the system planners devise new reliable and rather economical substation configurations and provide the possibility of proposing a promising cost-effective and prompt solution to the fault current over duty problem in the existing substations. This paper attempts to assess reliability of substation architectures accommodating the FCL operation and, besides, numerically investigates the FCL's impacts on the substation reliability indices. In order to clarify the proposed approach, two case studies with and without FCL are analyzed and... 

    Optimal integration of phasor measurement units in power systems considering conventional measurements

    , Article IEEE Transactions on Smart Grid ; Volume 4, Issue 2 , June , 2013 , Pages 1113-1121 ; 19493053 (ISSN) Azizi, S ; Gharehpetian, G. B ; Dobakhshari, A. S ; Sharif University of Technology
    2013
    Abstract
    This paper presents an integer linear programming (ILP) framework for the optimal placement of phasor measurement units (PMUs), in the presence of conventional measurements. Furthermore, by the proposed method, the power system remains completely observable during all possible single contingencies for lines and measurement devices. In doing so, the potential of circuit equations associated with both PMUs and conventional measurements as well as the network topology are fully utilized by a system of equations to reach the minimum possible numbers of required PMUs. The limitation of communication channels is also taken into account in the proposed ILP-based framework. The method is implemented... 

    Hierarchical optimal robust load-frequency control for power systems

    , Article IET Generation, Transmission and Distribution ; Volume 6, Issue 4 , 2012 , Pages 303-312 ; 17518687 (ISSN) Rahmani, M ; Sadati, N ; Sharif University of Technology
    Abstract
    In this study, a hierarchical optimal robust controller is presented for the power system load-frequency control problem. In this approach, the multi-area power system is first decomposed into several sub-systems (areas). Then by using a two-level control strategy, the overall optimal solution is obtained. At the first level, the optimal control of each area is obtained with respect to local information and also considering interactions coming from other areas. At the second level, by using a coordination strategy, the local controllers will converge to global solution and optimal robust controller is achieved. This approach is applicable to both single-area and multi-area interconnected... 

    Reliability study of HV substations equipped with the fault current limiter

    , Article IEEE Transactions on Power Delivery ; Volume 27, Issue 2 , 2012 , Pages 610-617 ; 08858977 (ISSN) Fotuhi Firuzabad, M ; Aminifar, F ; Rahmati, I ; Sharif University of Technology
    2012
    Abstract
    Of particular interest to restrict the short-circuit level of interconnected power systems is to exploit fault current limiter (FCL) technologies. FCLs let the system planners devise new reliable and rather economical substation configurations and provide the possibility of proposing a promising cost-effective and prompt solution to the fault current over duty problem in the existing substations. This paper attempts to assess reliability of substation architectures accommodating the FCL operation and, besides, numerically investigates the FCL's impacts on the substation reliability indices. In order to clarify the proposed approach, two case studies with and without FCL are analyzed and... 

    Optimal unified power flow controller application to enhance total transfer capability

    , Article IET Generation, Transmission and Distribution ; Volume 9, Issue 4 , 2015 , Pages 358-368 ; 17518687 (ISSN) Rajabi Ghahnavieh, A ; Fotuhi Firuzabad, M ; Othman, M ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    Abstract
    For a power transfer path, total transfer capability (TTC) represents maximum power that can be transferred over the transmission system. Unified power flow controller (UPFC) is a device that can be used to increase in TTC. This study presents a new method for optimal UPFC application to minimise power loss while enhancing TTC. Based on UPFC injection model, the solution region of UPFC parameters is first found using the proposed method to maximise TTC. It then searches the solution region to find optimal UPFC control mode and setting to minimise system power loss. The proposed method is applied to the IEEE-Reliability Test System and the UPFC application impact are evaluated. Comparative... 

    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
    Abstract
    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... 

    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
    2005
    Abstract
    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 multistage PMU placement in electric power systems

    , Article IEEE Transactions on Power Delivery ; Vol. 26, issue. 2 , 2011 , p. 841-849 ; ISSN: 08858977 Aminifar, F ; Fotuhi-Firuzabad, M ; Shahidehpour, M ; Khodaei, A ; Sharif University of Technology
    Abstract
    This paper presents an optimization model for the calculation of the minimum number of phasor measurement units (PMUs) in electrical power networks. The problem constraint is a predefined probability of observability associated with each bus. The mixed-integer programming is used for the proposed optimization and an efficient linearization technique is proposed to convert the nonlinear function representing the probability of observability into a set of linear expressions. The PMU placement is staged in a multi-year planning horizon due to financial and physical constraints. The average probability of observability is maximized at the intermediate planning stages, subject to a limited number... 

    Observability enhancement by optimal PMU placement considering random power system outages

    , Article Energy Systems ; Vol. 2, issue. 1 , 2011 , p. 45-65 ; ISSN: 18683967 Aminifar, F ; Fotuhi-Firuzabad, M ; Shahidehpour, M ; Khodaei, A ; Sharif University of Technology
    Abstract
    This paper enhances the observability of power networks by taking into consideration random component outages. The architecture of wide-area measurement system (WAMS) is analyzed in order to identify components that would affect the network observability. An iterative framework is devised to calculate a bus index in power networks equipped with phasor measurement units (PMUs) and conventional measurements. The average of bus indices represents a system index which provides an overall insight on the power network observability. The system index is utilized as a criterion to distinguish among multiple optimal PMU placements. Conventional bus injection and line flow measurements and the effect... 

    Reliability modeling of PMUs using fuzzy sets

    , Article IEEE Transactions on Power Delivery ; Vol. 25, issue. 4 , 2010 , p. 2384-2391 ; ISSN: 8858977 Aminifar, F ; 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... 

    Two-level optimal load-frequency control for multi-area power systems

    , Article International Journal of Electrical Power and Energy Systems ; Volume 53, Issue 1 , December , 2013 , Pages 540-547 ; 01420615 (ISSN) Rahmani, M ; Sadati, N ; Sharif University of Technology
    2013
    Abstract
    In large-scale power systems, classical centralized control approaches may fail due to geographically distribution of information and decentralized controllers result in sub-optimal solution for load-frequency control (LFC) problems. In this paper, a two-level structure is presented to obtain optimal solution for LFC problems and also reduce the computational complexity of centralized controllers. In this approach, an interconnected multi-area power system is decomposed into several sub-systems (areas) at the first-level. Then an optimization problem in each area is solved separately, with respect to its local information and interaction signals coming from other areas. At the second-level,... 

    Load-frequency control of interconnected power system using emotional learning-based intelligent controller

    , Article International Journal of Electrical Power and Energy Systems ; Volume 36, Issue 1 , March , 2012 , Pages 76-83 ; 01420615 (ISSN) Farhangi, R ; Boroushaki, M ; Hosseini, S. H ; Sharif University of Technology
    2012
    Abstract
    In this paper a novel approach based on the emotional learning is proposed for improving the load-frequency control (LFC) system of a two-area interconnected power system with the consideration of generation rate constraint (GRC). The controller includes a neuro-fuzzy system with power error and its derivative as inputs. A fuzzy critic evaluates the present situation, and provides the emotional signal (stress). The controller modifies its characteristics so that the critic's stress is reduced. The convergence and performance of the proposed controller, both in presence and absence of GRC, are compared with those of proportional integral (PI), fuzzy logic (FL), and hybrid neuro-fuzzy (HNF)... 

    Application of intelligence-based predictive scheme to load-frequency control in a two-area interconnected power system

    , Article Applied Intelligence ; Volume 35, Issue 3 , 2011 , Pages 457-468 ; 0924669X (ISSN) Mazinan, A. H ; Hosseini, A. H ; Sharif University of Technology
    2011
    Abstract
    This paper describes an application of intelligence- based predictive scheme to load-frequency control (LFC) in a two-area interconnected power system. In this investigation, at first, a dynamic model of the present system has to be considered and subsequently an efficient control scheme which is organized based on Takagi-Sugeno-Kang (TSK) fuzzy-based scheme and linear generalized predictive control (LGPC) scheme needs to be developed. In the control scheme proposed, frequency deviation versus load electrical power variation could efficiently be dealt with, at each instant of time. In conclusion, in order to validate the effectiveness of the proposed control scheme, the whole of outcomes are... 

    Probabilistic multistage PMU placement in electric power systems

    , Article IEEE Transactions on Power Delivery ; Volume 26, Issue 2 , December , 2011 , Pages 841-849 ; 08858977 (ISSN) Aminifar, F ; Fotuhi Firuzabad, M ; Shahidehpour, M ; Khodaei, A ; Sharif University of Technology
    2011
    Abstract
    This paper presents an optimization model for the calculation of the minimum number of phasor measurement units (PMUs) in electrical power networks. The problem constraint is a predefined probability of observability associated with each bus. The mixed-integer programming is used for the proposed optimization and an efficient linearization technique is proposed to convert the nonlinear function representing the probability of observability into a set of linear expressions. The PMU placement is staged in a multi-year planning horizon due to financial and physical constraints. The average probability of observability is maximized at the intermediate planning stages, subject to a limited number... 

    Observability enhancement by optimal PMU placement considering random power system outages

    , Article Energy Systems ; Volume 2, Issue 1 , 2011 , Pages 45-65 ; 18683967 (ISSN) Aminifar, F ; Fotuhi Firuzabad, M ; Shahidehpour, M ; Khodaei, A ; Sharif University of Technology
    Abstract
    This paper enhances the observability of power networks by taking into consideration random component outages. The architecture of wide-area measurement system (WAMS) is analyzed in order to identify components that would affect the network observability. An iterative framework is devised to calculate a bus index in power networks equipped with phasor measurement units (PMUs) and conventional measurements. The average of bus indices represents a system index which provides an overall insight on the power network observability. The system index is utilized as a criterion to distinguish among multiple optimal PMU placements. Conventional bus injection and line flow measurements and the effect... 

    Performance improvement of steady-state and transient operation of offshore wind farm HVDC power transmission

    , Article 2015 IEEE 16th Workshop on Control and Modeling for Power Electronics, COMPEL 2015, 12 July 2015 through 15 July 2015 ; July , 2015 , Page(s): 1 - 7 ; 9781467368476 (ISBN) Safaeian, R ; Ebrahimi, S ; Parniani, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Wind power generation is increasing fast as a clean renewable energy resource. Offshore wind farms are popular due to advantages such as higher and smoother wind speeds, less farm site limitations, etc. High capacitive currents and need to expensive compensations, make use of high-voltage-direct-current (HVDC) power transmission indispensable for longdistance wind farm power generations. Steady-state and transient performance improvements of HVDC systems have always been an interesting industrial and academic research area. In this paper, a novel control method is proposed to improve the steady-state operation of HVDC system. Moreover, a new fault detection scheme is proposed to improve the...