Search for: active-and-reactive-power
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    A new approach for AC state estimation based on a linear network model

    , Article ELECO 2013 - 8th International Conference on Electrical and Electronics Engineering ; 2013 , Pages 117-121 ; 9786050105049 (ISBN) Safdarian, A ; Fotuhi Firuzabad, M ; Aminifar, F ; Lehtonen, M ; Ozdemir, A ; Sharif University of Technology
    This paper presents a new and efficient formulation for the state estimation (SE) which can be solved in one single shot of computation. The proposed approach adopts line flows and the square of voltage magnitudes as the problem state variable and considers both active and reactive power quantities. The objective function is to minimize the weighted sum of the least square values of measurement residuals. The nonlinearity associated with line losses is left by assuming these values as slack variables. Numerical studies are conducted through two standard networks. In order to compare the performance of the proposed method, the conventional weighted least square (WLS) state estimation with... 

    A new formulation for power system reliability assessment with AC constraints

    , Article International Journal of Electrical Power and Energy Systems ; Vol. 56, issue , March , 2014 , p. 298-306 ; ISSN: 1420615 Safdarian, A ; Fotuhi-Firuzabad, M ; Aminifar, F ; Lehtonen, M ; Sharif University of Technology
    Recent investigations have revealed the significant role of reactive power in blackout events. The associated disturbances frequently emerge in the form of voltage instability and collapse. Due to the computational complexity of modeling and analysis of enormous contingencies, DC approximation of the power flow, without accounting the role of reactive power, is usually used to evaluate the contingencies and to mitigate the associated probable violations. This paper, at first, presents a linear power flow model based on an approximated version of AC power flow formulation. The proposed model is then used to develop an efficient reliability assessment approach which is capable of taking both... 

    Distribution loss allocation for radial systems including dgs

    , Article IEEE Transactions on Power Delivery ; Vol. 29, issue. 1 , 2014 , pp. 72-80 ; ISSN: 08858977 Ghofrani-Jahromi, Z ; Mahmoodzadeh, Z ; Ehsan, M ; Sharif University of Technology
    Due to the liberalization of the electricity market and the introduction of distributed generation (DG), the importance of distribution loss allocation (LA) has increased. This paper presents a new method for distribution power LA in radial systems. The proposed method, which is based on the results of power flow and considers active and reactive power flows of lines for LA, is composed of three steps. In the first step, starting from the source nodes (i.e., the nodes whose generation is more than their load), the power loss allocated to all nodes is calculated and then the power loss allocated to the loads connected to each node is obtained. In the next step, the total power loss is... 

    Phase identification of singlephase customers and PV panels via smart Meter data

    , Article IEEE Transactions on Smart Grid ; Volume 12, Issue 5 , 2021 , Pages 4543-4552 ; 19493053 (ISSN) Heidari-Akhijahani, A ; Safdarian, A ; Aminifar, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    With proliferation of single-phase rooftop photovoltaic (PV) panels, phase balancing in low voltage (LV) distribution feeders becomes the point of concern. In this way, identification of the hosting phase of connected single-phase customers and PV panels is a prerequisite. This paper proposes an optimization model for the phase identification problem. The objective is to minimize the summation of the absolute error between estimated and measured variables. Smart meters (SMs) data including active and reactive power absorptions/injections, nodal voltage magnitudes, and network configuration data form the input of the model. Potential errors in the input data are captured in the model while... 

    Prevention of distribution network overvoltage by adaptive droop-based active and reactive power control of PV systems

    , Article Electric Power Systems Research ; Volume 133 , 2016 , Pages 313-327 ; 03787796 (ISSN) Ghasemi, M. A ; Parniani, M ; Sharif University of Technology
    Elsevier Ltd 
    Proliferation of grid-connected photovoltaic systems (PVSs) causes technical problems due to their variable and non-dispatchable generated power. High penetration of PVS in distribution networks can result in overvoltage in some operating conditions. Although this situation occurs rarely, it limits the installed capacity of PVS. In this paper, adaptive droop-based control algorithms are presented to regulate active and reactive power of PVS, with the objectives of loss minimization and increasing the PVS capacity installation without unallowable overvoltage. Operating voltage range of the PVS is divided into several intervals, and a specific control algorithm is presented for each of them.... 

    Planning in microgrids with conservation of voltage reduction

    , Article IEEE Systems Journal ; Volume 12, Issue 3 , 2018 , Pages 2782-2790 ; 19328184 (ISSN) Gheydi, M ; Nouri, A ; Ghadimi, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    The main focus of this paper is to find an upgrade plan for a microgrid. This plan includes system lines' upgrades, the place, and size of the new capacitors and DERs. As usual, the planning process is begun with the load forecasting. The main objectives include minimization of system upgrade cost, loss cost, loss cost in peak load, and finally demand cost. The last objective is realized here using the tap changer of the main station transformer and reactive power support of the sources available or planned for the future of the grid. This is always referred to as the conservation of voltage reduction. In order to consider the effects of bus voltages on the system demand, the ZIP model for... 

    A novel islanding detection scheme for synchronous distributed generation using rate of change of exciter voltage over reactive power at DG-side

    , Article 2017 Australasian Universities Power Engineering Conference, AUPEC 2017 ; Volume 2017-November , 5 February , 2018 , Pages 1-5 ; 9781538626474 (ISBN) Rostami, A ; Bagheri, M ; Naderi, S. B ; Negnevitsky, M ; Jalilian, A ; Blaabjerg, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Penetration of distributed generation (DG) in distribution networks is rapidly increasing. DGs' application enhances system's reliability and power quality. However, along their benefits, there are some issues. One of the most important issues of DGs' application is the islanding. This paper presents a novel passive islanding detection scheme for synchronous DG based. In the proposed scheme, rate of change of exciter voltage over rate of change of reactive power at the DG-side (dE/dQDG) is taken into account. In reality, the voltage and reactive power of load depend on the exciter of the synchronous generator. Therefore, due to lack of inertia, response of these parameters to small changes... 

    Application of state feedback controller to ensure robust d-stable operation of virtual synchronous generators

    , Article IEEE Transactions on Energy Conversion ; Volume 36, Issue 2 , 2021 , Pages 602-610 ; 08858969 (ISSN) Pourmohammad, M ; Toulabi, M ; Ranjbar, A. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    This article presents a comprehensive small signal model for a virtual synchronous generator (VSG) integrated into a microgrid. In the developed state-space, active and reactive power control loops of the VSG as well as resistances, and reactances of the lines are considered. Based on this model, the robust D-stable region in terms of different values of inertia constant $(M)$, and damping coefficient $(D)$ values of the VSG is obtained. To enhance both transient performance as well as guarantee the robust D-stable operation of VSG, an optimization problem is also proposed. Moreover, a new control method is suggested to damp frequency oscillations of the microgrid. The proposed controller is... 

    Doubly fed induction generators to enhance inter-area damping based on a Robust controller: H2/ H∞ Control

    , Article SN Applied Sciences ; Volume 3, Issue 1 , 2021 ; 25233971 (ISSN) Goodarzi, A ; Ranjbar, A. M ; Dehghani, M ; Ghasemi Garpachi, M ; Ghiasi, M ; Sharif University of Technology
    Springer Nature  2021
    In this study, an auxiliary damping controller based on a robust controller considering the active and reactive power control loops for a doubly-fed induction generator for wind farms is proposed. The presented controller is able to improve the inter-area oscillation damping. In addition, the proposed controller applies only one accessible local signal as the input; however, it can improve the inter-area oscillation damping and, consequently the system stability for the various working conditions and uncertainties. The oscillatory modes of the system are appointed using the linear analysis. Then, the controller’s parameters are determined using the robust control approaches (H∞/ H2) with the... 

    Five-leg converter topology for wind energy conversion system with doubly fed induction generator

    , Article Renewable Energy ; Volume 36, Issue 11 , 2011 , Pages 3187-3194 ; 09601481 (ISSN) Shahbazi, M ; Poure, P ; Saadate, S ; Zolghadri, M. R ; Sharif University of Technology
    In this paper, application of a five-leg converter in Doubly Fed Induction Generator (DFIG) for Wind Energy Conversion Systems (WECS) is investigated. The five-leg structure and its PWM control are studied and performances are compared with the classical six-leg topology. The main drawback of five-leg converter with respect to the six-leg back-to-back converter is the need to increase the dc-link voltage for the same operation point, i.e. the same powers in case of WECS. So, different methods for the reduction of the required dc-link voltage in the five-leg case are studied. The five-leg converter is used to replace the conventional six-leg one, with the same ability. For the performance... 

    A novel management scheme to reduce emission produced by power plants and plug-in hybrid electric vehicles in a smart microgrid

    , Article International Journal of Environmental Science and Technology ; Volume 17, Issue 5 , 2020 , Pages 2529-2544 Ashrafi, R ; Soleymani, S ; Mehdi, E ; Sharif University of Technology
    Springer  2020
    Recently, with the growth and development of distributed generation (DGs) and energy storage systems (ESSs), as well as smart control equipment, microgrids (MGs) have been developed. Microgrids are comprised of a limited number of constitutive parts, including loads, DGs, ESSs, and electric vehicles (EVs). This paper presents a novel scheme to manage active and reactive powers, based on DGs, ESSs, and EVs to reduce the total operation cost including power generation and emission costs. Simultaneous management of active and reactive power makes it possible to consider grid operation constraints together. In the proposed schedule, the vehicles are assumed to be plug-in hybrid electric...