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    Enhanced frequency droop method for decentralized power sharing control in DC microgrids

    , Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; Volume 9, Issue 2 , 2021 , Pages 1290-1301 ; 21686777 (ISSN) Jafari, M ; Peyghami, S ; Mokhtari, H ; Blaabjerg, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    This article proposes two novel approaches to improve the superimposed frequency droop scheme for the control of dc microgrids (MGs). Conventional voltage-based control strategies suffer from issues such as undesirable voltage regulations, poor power sharing among the sources, and negative effects of line resistances on the equivalent droop characteristics. To overcome these challenges, a superimposed frequency droop scheme has been introduced. However, this method suffers from three major issues: 1) instability in terms of load variation, which is due to the location of system dominant poles; 2) limitation in system loading due to the limitation in the transferred reactive power; and 3)... 

    Geometric-based fault diagnosis in a grid-connected inverter

    , Article Proceedings of the IEEE Conference on Decision and Control, 17 December 2018 through 19 December 2018 ; Volume 2018-December , 2019 , Pages 3421-3426 ; 07431546 (ISSN); 9781538613955 (ISBN) Mashreghi, A ; Namvar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    This paper presents a nonlinear geometric approach to fault detection and isolation (FDI) in grid-connected inverters. Faults are considered in inverter switches as well as in grid voltage and source current sensors. The FDI system is not sensitive to load variations or grid transients. No assumptions on balanced, zero-sum or sinusoidal form of voltages or currents are made. The resulting residual converges to zero in no-fault condition such that no threshold adjustment is needed. Simulations demonstrate performance of the proposed FDI system in presence of unknown disturbance. © 2018 IEEE  

    Finding assignable cause in medium voltage network by statistical process control

    , Article IET Conference Publications ; Volume 2013, Issue 615 CP , 2013 ; 9781849197328 (ISBN) Eini, B. J ; Mirzavand, M ; Mahdloo, F ; Sharif University of Technology
    The current of outgoing feeders are very important data transmitted over SCADA system. Monitoring of these currents can help dispatching engineers to detect abnormality in energy consumption trend and minor faults in distribution network. Statistical process control (SPC) is one of the capable approaches which can be used for this purpose. Statistical process control is based on categorizing variations into assignable causes and random causes. In current paper we described the methods which were used for finding assignable causes in load trend and short time load variation in Alborz province power distribution company pilot project. Although this approach is not developed completely and some... 

    Control of series resonant converter with robust performance against load and power circuit components uncertainties

    , Article PEDSTC 2010 - 1st Power Electronics and Drive Systems and Technologies Conference, 17 February 2010 through 18 February 2010, Tehran ; 2010 , Pages 122-128 ; 9781424459728 (ISBN) Mohammadpour, A ; Mokhtari, H ; Zolghadri, M. R ; Sharif University of Technology
    Robust performance controller design for duty-cycle controlled series resonant converter is proposed in this paper. The uncertainties of the converter are analyzed with load variation and power circuit components tolerances are taken into consideration. Additionally, a nominal performance H ∞ controller is designed. Closed-loop system is simulated and simulation results of robust controller are compared with H∞ nominal performance controller  

    Application of edge theorem for robust stability analysis of a power system with participating wind power plants in automatic generation control task

    , Article IET Renewable Power Generation ; Volume 11, Issue 7 , 2017 , Pages 1049-1057 ; 17521416 (ISSN) Toulabi, M ; Bahrami, S ; Ranjbar, A. M ; Sharif University of Technology
    Institution of Engineering and Technology  2017
    This study investigates the dynamic participation of wind power plants (WPPs) in the automatic generation control (AGC) task. The pre-specified model of wind farm in the AGC studies has been used. It is shown that operating of WPPs at the command mode results in a significant improvement in the frequency behaviour of power system due to their faster response. However, the WPPs may change their operation mode from the command mode to the maximum power point mode according to the wind speed conditions and load variations. This reduces the improvement in the frequency response. In this condition, the shortage in the wind power should be compensated by the conventional units. Thus, the share of... 

    Efficiency map of a switched reluctance motor using finite element method in vehicular applications

    , Article 7th Internatonal Conference on Power Electronics, ICPE'07, Daegu, 22 October 2007 through 26 October 2007 ; 2007 , Pages 644-649 ; 9781424418725 (ISBN) Mokhtari, H ; Tara, E ; Sharif University of Technology
    IEEE Computer Society  2007
    Switched Reluctance Motors (SRMs), which are simple and reliable motors, have attracted interest for electric vehicle propulsion systems. It is shown that an SRM offers a good performance at high acceleration and low speed driving conditions. Efficiency map of an electric motor is a very important characteristic specially when the motor is to be used in a wide range of speed and load variations, which is the case in electric propulsion systems. In this research, the efficiency map of an SRM is derived using a combination of the Finite Element Method (FEM) and a mathematical model. This efficiency map has been used for different driving cycles to test the SRM performance as a vehicle... 

    Small-signal modeling and fast response control strategy for DCVM Cúk converters in PFC applications.انجام شد

    , Article Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC ; 2011 , Pages 1795-1802 ; 9781424480845 (ISBN) Nasirian, V. R ; Karimi, Y ; Zolghadri, M. R ; Ahmadian, M ; Moayedi, A ; Davoudi, A ; Sharif University of Technology
    Cúk Converter operating in discontinuous capacitor voltage mode is an inherent PFC converter in which, unity power factor can be achieved using constant duty cycle and switching frequency. In this paper, a reduced-order switch network modeling technique is applied to Cúk converter operating in DCVM in order to derive small-signal model of the converter assuming a dc voltage source as the input source of the converter. This model is extended to derive the small-signal behavior of the converter while operating as a PFC converter. The validity of the proposed model is confirmed by both simulation and experimental results. Afterwards, a new control strategy is proposed in which switching... 

    Semi-exact elastic solutions for thermo-mechanical analysis of functionally graded rotating disks

    , Article Composite Structures ; Volume 93, Issue 12 , 2011 , Pages 3239-3251 ; 02638223 (ISSN) Hassani, A ; Hojjati, M. H ; Farrahi, G ; Alashti, R. A ; Sharif University of Technology
    In this paper, distributions of stress and strain components of rotating disks with non-uniform thickness and material properties subjected to thermo-elastic loading under different boundary conditions are obtained by semi-exact methods of Liao's homotopy analysis method (HAM), Adomian's decomposition method and He's variational iteration method (VIM). The materials are assumed to be perfectly elastic and isotropic. A two dimensional plane stress analysis is used. The distribution of temperature over the disk radius is assumed to have power forms with the higher temperature at the outer surface. The results of the three methods are compared with those obtained by Runge-Kutta's numerical...