Search for: distributed-generation
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    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) Rajabi Ghahnavie, A ; Parniani, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    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  

    Impact of distributed generation resources on customer interruption cost

    , Article 2004 International Conference on Power System Technology, POWERCON 2004, 21 November 2004 through 24 November 2004 ; Volume 1 , 2004 , Pages 856-861 ; 0780386108 (ISBN) Rajabi Ghahnavie, A ; Fotuhi Firuzabad, M ; Parniani, M ; Sharif University of Technology
    The electric power industry around the world is presently undergoing considerable changes with respect to structure, operation and regulation. Distributed generation is expected to play a major role in this new environment One the main benefits of DG is to enhance system reliability as it can restore power to the separated or bottle-necked part of distribution system in case of a contingency occurs. This paper presents an approach to examine and evaluates the applicability and customer interruption cost analysis in DG-connected distribution system in a specified planning horizon. The impacts on customer interruption cost reduction of different load growth rate, DG location and different... 

    Voltnar control in distribution networks with distributed generation

    , Article 5th IFAC Symposium on Power Plants and Power Systems Control 2003, 15 September 2003 through 19 September 2003 ; Volume 36, Issue 20 , 2003 , Pages 547-552 ; 14746670 (ISSN) Niknam, T ; Ranjbar, A. M ; Shirane, A. R ; Sharif University of Technology
    IFAC Secretariat  2003
    Due to the deregulation and restructuring in many countries, it is expected that amount of small-scale generations connected to the distribution networks increase. So it is necessary that impact of these kinds ofgenerators on VoltNar control would be investigated. This paper presents a new approach for VoltNar control in distribution system with Distributed Generation (DG) and it has shown that DG can improve the entire performance of network, by means of better controlling of the system and decreasing losses in network. In this approach Genetic Algorithm (GA) has been used as the optimization method where the amount of Dispersed Generation and its controlling parameters, Voltage regulators... 

    A combination of genetic algorithm and simulated annealing for optimal DG allocation in distribution networks

    , Article Canadian Conference on Electrical and Computer Engineering 2005, Saskatoon, SK, 1 May 2005 through 4 May 2005 ; Volume 2005 , 2005 , Pages 645-648 ; 08407789 (ISSN) Gandomkar, M ; Vakilian, M ; Ehsan, M ; Sharif University of Technology
    This paper presents a new algorithm based on integrating the use of genetic algorithms and simulated annealing methods to optimal allocation of distributed generation resources in distribution networks. Through this algorithm a significant improvement in the optimization goal is achieved. With a numerical example the superiority of the proposed algorithm is demonstrated in comparison with the simple genetic algorithm. © 2005 IEEE  

    An Milp model for switch, DG, and tie line placement to improve distribution grid reliability

    , Article IEEE Systems Journal ; 2022 , Pages 1-12 ; 19328184 (ISSN) Zare Bahramabadi, M ; Ehsan, M ; Farzin, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2022
    Remote controlled switches (RCSs) have the ability to isolate the faulted area from other parts of the distribution system. On the other hand, the dispatchable distributed generators (DDGs) and tie lines can supply the interrupted loads after fault occurrence trough microgrids and reduce the outage time. In this regard, this article proposes a planning model for simultaneous placement of RCSs, DDGs, and tie lines to improve distribution system reliability. The presence of renewable distributed generations (RDGs) and energy storage systems, which have an increasing penetration in today's distribution networks are also considered. Moreover, two different practical load shedding methods are... 

    Nondetection zone assessment of an active islanding detection method and its experimental evaluation

    , Article IEEE Transactions on Power Delivery ; Volume 26, Issue 2 , 2011 , Pages 517-525 ; 08858977 (ISSN) Bahrani, B ; Karimi, H ; Iravani, R ; Sharif University of Technology
    This paper analytically determines the nondetection zone (NDZ) of an active islanding detection method, and proposes a solution to obviate the NDZ. The method actively injects a negative-sequence current through the interface voltage-sourced converter (VSC) of a distributed generation (DG) unit, as a disturbance signal for islanding detection. The estimated magnitude of the corresponding negative-sequence voltage at the PCC is used as the islanding detection signal. In this paper, based on a laboratory test system, the performance of the islanding detection method under UL1741 anti-islanding test conditions is evaluated. Then, determining the NDZ of the method and proposing the... 

    Effect of customer demand type on optimization of distributed generation for minimization of energy loss

    , Article International Review of Electrical Engineering ; Volume 7, Issue 2 , Oct , 2012 , Pages 4113-4122 ; 18276660 (ISSN) Ebrahimi, R ; Ehsan, M ; Nouri, H ; Sharif University of Technology
    Praise Worthy Prize  2012
    The problem of distributed generation (DG) optimization in distribution systems has normally been assessed by assuming a constant power (real and reactive) load model. Such assumptions may lead to inconsistent and misleading results about loss reduction, DG optimization and other subsequent calculations. In this paper, the effect of different types of demand, e.g. industrial, residential and commercial, and its time varying effects on distribution networks is investigated. Customer demand type is defined by the load model that is voltage dependent and the load patterns from real life hourly demand data. The study shows that by defining the energy loss minimization as the objective function,... 

    Automatic image annotation using semi-supervised generative modeling

    , Article Pattern Recognition ; Volume 48, Issue 1 , January , 2015 , Pages 174-188 ; 00313203 (ISSN) Amiri, S. H ; Jamzad, M ; Sharif University of Technology
    Elsevier Ltd  2015
    Image annotation approaches need an annotated dataset to learn a model for the relation between images and words. Unfortunately, preparing a labeled dataset is highly time consuming and expensive. In this work, we describe the development of an annotation system in semi-supervised learning framework which by incorporating unlabeled images into training phase reduces the system demand to labeled images. Our approach constructs a generative model for each semantic class in two main steps. First, based on Gamma distribution, a generative model is constructed for each semantic class using labeled images in that class. The second step incorporates the unlabeled images by using a modified EM... 

    Distributed generation planning for losses, voltage profile, line congestion and total system cost improvement

    , Article International Review of Electrical Engineering ; Volume 4, Issue 3 , 2009 , Pages 434-440 ; 18276660 (ISSN) Porkar, S ; Poure, P ; Abbaspour Tehrani fard, A ; Saadate, S ; Sharif University of Technology
    The main goal of this paper is to obtain the optimal Distributed Generation (DG) investments as well as purchase additional power from Transmission Companies (TRANSCOs). To do this, a new mathematical modeling and a new software package interfacing between the two powerful softwares MATLAB and GAMS are used. The proposed model optimizes total system planning costs and consequently costumers' bills, reduces total system losses, guaranties system voltage profiles and prevents feeders' congestion. This new model and software package have been executed in two different cases depending if system voltage profiles are in their permissible margin or not; in each case, three different scenarios are... 

    Micro-Grid Protection in Presence of Inverter Based Distributed Generation

    , M.Sc. Thesis Sharif University of Technology Zarei, Fariborz (Author) ; Parniani, Mostafa (Supervisor)
    In this study, control and protection of low voltage microgrids have been analyzed. Studied microgrid takes the advantages of inverter based distributed generation. One of the most important issues in inverter based microgrids is the control of its distributed generation. Since, the low voltage networks have single phase loads and many imbalances, these imbalances can affect the control of IBDGs (inverter based distributed generations). This issue in the islanded mode of operation is the most important, because in this mode of operation, IBDGs control the network voltage and frequency.
    In this thesis, the different control strategies of IBDGs are reviewed, and then modified to address... 

    Developing an Framework for Efficient Usage of Distributed Generation Expansion Plans in Distribution Network Considering the Effects of Reward-Penalty Mechanism

    , M.Sc. Thesis Sharif University of Technology Mirkhaef, Farzan (Author) ; Abbaspour Tehrani Fard, Ali (Supervisor)
    Based on codification and implementation of regulations of supporting from development of distributed generation sources, it is expected that in future years, investment in distributed generation scheme will be welcomed by private investors impressively. Under this circumstances, distribution Company will be faced with new chances for improving quality level of their services and optimal management of penalty-reward schemes. Penalty-reward schemes is set by legislator for distribution Company in order to improve their network. One of the pioneer ways is using distributed generators. So first, distribution Companies have to find optimum places for using these generators and in the second step... 

    Control of a microgrid with unbalanced loads using virtual negative-sequence impedance loop

    , Article PEDSTC 2014 - 5th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2014 , p. 78-83 Hamzeh, M ; Karimi, H ; Mokhtari, H ; Mahseredjian, J ; Sharif University of Technology
    This paper presents an effective control strategy for autonomous operation of a multi-bus medium voltage (MV) microgrid (MG) consisting of several dispatchable distributed generation (DG) units. Each electronically-coupled DG unit supplies the loads which can be unbalanced due to the inclusion of single-phase loads. The proportional resonance (PR) and droop controllers are, respectively, used to regulate the load voltage and share the average powers among the DG units. The virtual negative-sequence impedance controller (VNSIC) is proposed to effectively compensate the negative-sequence currents of the unbalanced loads. Moreover, the VNSIC minimizes the negative-sequence currents in the MV... 

    A stochastic framework for short-term operation of a distribution company

    , Article IEEE Transactions on Power Systems ; Volume 28, Issue 4 , 2013 , Pages 4712-4721 ; 08858950 (ISSN) Safdarian, A ; Fotuhi Firuzabad, M ; Lehtonen, M ; Sharif University of Technology
    This paper presents a stochastic framework for short-term operation of a distribution company (disco). The proposed framework optimizes disco's operational decisions in two hierarchical stages. The first stage, called day-ahead operation stage (DAOS), deals with the operational decisions on purchases from the day-ahead market and commitment of distributed generation (DG) units. The objective of this stage is to minimize the expected operating cost while the financial risk exposed by uncertain real-time prices and loads is restricted to a given level. The model associated with this stage is based on the mixed-integer programming (MIP) format. The second stage, named real-time operation stage... 

    A new decentralized voltage control scheme of an autonomous microgrid under unbalanced and nonlinear load conditions

    , Article Proceedings of the IEEE International Conference on Industrial Technology ; February , 2013 , Pages 1812-1817 ; 9781467345699 (ISBN) Paridari, K ; Hamzeh, M ; Emamian, S ; Karimi, H ; Bakhshai, A ; Sharif University of Technology
    This paper presents an effective voltage control strategy for the autonomous operation of a medium voltage (MV) microgrid under nonlinear and unbalanced load conditions. The main objectives of this strategy are to effectively compensate the harmonic and negative-sequence currents of nonlinear and unbalanced loads using distributed generation (DG) units. The proposed control strategy consists of a multi-proportional resonant controller (MPRC) whose parameters are assigned with particle swarm optimization (PSO) algorithm. The optimization function is defined to minimize the tracking error at the specific harmonics considering the stability limitations. In this paper the performance of the... 

    IGDT based robust decision making tool for DNOs in load procurement under severe uncertainty

    , Article IEEE Transactions on Smart Grid ; Volume 4, Issue 2 , 2013 , Pages 886-895 ; 19493053 (ISSN) Soroudi, A ; Ehsan, M ; Sharif University of Technology
    This paper presents the application of information gap decision theory (IGDT) to help the distribution network operators (DNOs) in choosing the supplying resources for meeting the demand of their customers. The three main energy resources are pool market, distributed generations (DGs), and the bilateral contracts. In deregulated environment, the DNO is faced with many uncertainties associated to the mentioned resources which may not have enough information about their nature and behaviors. In such cases, the classical methods like probabilistic methods or fuzzy methods are not applicable for uncertainty modeling because they need some information about the uncertainty behaviors like... 

    Optimal allocation of distributed generation using a two-stage multi-objective mixed-integer-nonlinear programming

    , Article European Transactions on Electrical Power ; Volume 21, Issue 1 , 2011 , Pages 1072-1087 ; 1430144X (ISSN) Porkar, S ; Poure, P ; Abbaspour Tehrani Fard, A ; Saadate, S ; Sharif University of Technology
    Cost is one of the most essential factors that influence many decisions taken in the distribution system planning. In general, cost can be defined as everything that should be sacrificed to gain the desired results. This paper proposes a new two-stage methodology for distributed generation (DG) placement as an attractive option for distribution system planner. This method aims to minimize cost and maximize total system benefit (TSB). Optimal placement and size are obtained from total cost minimization mathematical problem which is solved in the first stage. For each DG cost characteristics and for each investment payback time, there is an optimal location and size. Then the optimal DG... 

    Day-ahead resource scheduling in distribution networks with presence of electric vehicles and distributed generation units

    , Article Electric Power Components and Systems ; Volume 47, Issue 16-17 , 2019 , Pages 1450-1463 ; 15325008 (ISSN) Shafiee, M ; Ghazi, R ; Moeini Aghtaie, M ; Sharif University of Technology
    Taylor and Francis Inc  2019
    In this paper a new framework for scheduling of available resources in the distribution networks is developed. In this respect attempts are focused on interactions between charging/discharging profiles of electric vehicles (EVs) and output power of distributed generation units. To reach this goal, the proposed framework is designed as a two-stage optimization procedure. In the first stage, the charging/discharging schedules of EVs are extracted running a linear programing optimization problem taking into account the EV users' constraints and requirements. The usage profiles of the DG units, strategy of buying electricity from the market and also the final charging/discharging patterns of the... 

    Improvement of Control of Hybrid AC-DC Microgrid in Islanded Mode

    , Ph.D. Dissertation Sharif University of Technology Khorsandi, Amir (Author) ; Mokhtari, Hossein (Supervisor)
    A microgrid is a collection of loads, sources, and power storage units that operates as a single controllable system and can operate in grid-connected or islanded mode. From the generating side, renewable energy resources such as photovoltaic system, fuel cell and power storage units are inherently DC. From the load side, electronic loads such as computers, data centers and most of the variable speed motor drives require a DC supply. Therefore, DC Microgrids have gained widespread attention in recent years. On the other hand, since existing distribution systems are mostly AC, a hybrid microgrid is more likely. The hybrid microgrid is composed of two AC and DC subgrids interlinked by power... 

    Load Shedding in Microgrids to preserve System Stability In The Islanded Operation Mode

    , M.Sc. Thesis Sharif University of Technology Jamshidi, Mohammad Hossein (Author) ; Parniani, Mustafa (Supervisor)
    In the near future, it is expected that the microgrids become widespreed due to issues such as reliability, increased penetration of renewable energy sources and distributed generation, environmental concerns and shortage of fossil fuels. Different control methods have been suggested to regulate the frequency and voltage of the system so that these quantities remain in their permissible range upon islanding and in the islanded operation mode. However, in emergency conditions, such as shortage of generated power compared to the load of microgrid, frequency or voltage reduction occures due to imbalance. In this situation, it is invitable to shed extra load to maintain the stability and... 

    Hybrid AC/DC Microgrid Planning

    , M.Sc. Thesis Sharif University of Technology Shariat, Maryam (Author) ; Fotouhi Firuzabad, Mahmoud (Supervisor) ; Rajabi Ghahnavie, Abbas (Co-Advisor)
    Nowadays, due to the increasing importance and penetration of microgrids, solving the microgrid optimal sizing problem has become more important. The current utility grid and conventional energy sources are mainly ac, however, increasing rate of the replacement of the ac load with dc load lead to a more efficient dc system. So choosing the optimal type of microgrid as a way to increase efficiency of these systems would be a serious issue. This thesis establishes a planning model which finds the optimal size and type of a microgrid to minimize total cost. Total cost includes investment, operation and reliability cost of the microgrid. Sizes of DGs, converters and transformer linking the...