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    A novel flexible control strategy for unified power quality conditioner

    , Article Iranian Journal of Electrical and Computer Engineering ; Volume 12, Issue 1-2 , 2013 , Pages 13-22 ; 16820053 (ISSN) Mohammadi, H. R ; Varjani, A. Y ; Mokhtari, H ; Sharif University of Technology
    Iranian Research Institute for Electrical Engineering  2013
    This paper presents a novel flexible control strategy for Unified Power Quality Conditioner (UPQC), which achieves more flexibility in compensation of power quality disturbances as compared to the existing methods. The proposed control strategy provides priority-based compensation as well as full and standard-based compensation considering the rating of series and shunt parts of a UPQC. The priority-based compensation is done based on the compensation priority among different power quality disturbances. In this control strategy, an on-line estimation of different voltage and current disturbances is required. For this purpose, a Unified Adaptive Power Quality Estimator (UAPQE) has been... 

    A new active method in damping possible resonances in active filters

    , Article Iranian Journal of Electrical and Computer Engineering ; Volume 7, Issue 1 , 2008 , Pages 61-67 ; 16820053 (ISSN) Rahimi, M ; Mokhtari, H ; Zafarabadi, Gh ; Sharif University of Technology
    This paper investigates resonance phenomenon in active filters. The paper studies the effect of system/filter parameters on resonance conditions. It also proposes an active technique for damping such resonances. The study is based on modal analysis in which unstable modes or modes with slow damping are first extracted. Then, using a new technique, such modes are considerably damped. PSCAD/EMTDC software is also employed to verify the performance of the proposed technique. © 2008 ACECR  

    A new wavelet-based method for detection of high impedance faults

    , Article 2005 International Conference on Future Power Systems, Amsterdam, 16 November 2005 through 18 November 2005 ; Volume 2005 , 2005 ; 9078205024 (ISBN); 9789078205029 (ISBN) Mokhtari, H ; Aghatehrani, R ; Sharif University of Technology
    IEEE Computer Society  2005
    Detecting high impedance faults is one of the challenging issues for electrical engineers. Over-current relays can only detect some of the high impedance faults. Distance relays are unable to detect faults with impedance over 100Ω. In this paper, by using an accurate model for high impedance faults, a new wavelet-based method is presented. The proposed method, which employs a 3 level neural network system, can successfully differentiate high impedance faults from other transients. The paper also thoroughly analyzes the effect of choice of mother wavelet on the detection performance. Simulation results which are carried out using PSCAD/EMTDC software are summarized  

    Multiconverter unified power-quality conditioning system: MC-UPQC

    , Article IEEE Transactions on Power Delivery ; Volume 24, Issue 3 , 2009 , Pages 1679-1686 ; 08858977 (ISSN) Mohammadi, H. R ; Yazdian Varjani, A ; Mokhtari, H ; Sharif University of Technology
    This paper presents a new unified power-quality conditioning system (MC-UPQC), capable of simultaneous compensation for voltage and current in multibus/multifeeder systems. In this configuration, one shunt voltage-source converter (shunt VSC) and two or more series VSCs exist. The system can be applied to adjacent feeders to compensate for supply-voltage and load current imperfections on the main feeder and full compensation of supply-voltage imperfections on the other feeders. In the proposed configuration, all converters are connected back to back on the dc side and share a common dc-link capacitor. Therefore, power can be transferred from one feeder to adjacent feeders to compensate for... 

    Performance evaluation of custom power devices in process of motor bus transfer

    , Article 2009 4th IEEE Conference on Industrial Electronics and Applications, ICIEA 2009, Xi'an, 25 May 2009 through 27 May 2009 ; 2009 , Pages 2279-2284 ; 9781424428007 (ISBN) Janaghaei, M ; Abedi, M ; Darabi, F ; Sharif University of Technology
    Quality and continuity of electrical power to sensitive loads especially in power plants and industrial sectors is of great importance. For this reason, bus transfer is used. During the bus transfer interval, sensitive loads especially motors will be interrupted, and may encounter difficulties. So, it is used reactive power compensator and custom power devices to mitigate stress in motors and improve power quality indices. This paper presents the effect of reactive power compensator and custom power devices paralleling with motor in process of bus transfer which is done in two methods: EMTS and STS. Also, it is investigated dynamic performance of induction motor and spin-down curves in... 

    Active power management of multihybrid fuel cell/supercapacitor power conversion system in a medium voltage microgrid

    , Article IEEE Transactions on Smart Grid ; Volume 3, Issue 4 , 2012 , Pages 1903-1910 ; 19493053 (ISSN) Ghazanfari, A ; Hamzeh, M ; Mokhtari, H ; Karimi, H ; Sharif University of Technology
    This paper proposes a hierarchical active power management strategy for a medium voltage (MV) islanded microgrid including a multihybrid power conversion system (MHPCS). To guarantee excellent power management, a modular power conversion system is realized by parallel connection of small MHPCS units. The hybrid system includes fuel cells (FC) as main and supercapacitors (SC) as complementary power sources. The SC energy storage compensates the slow transient response of the FC stack and supports the FC to meet the grid power demand. The proposed control strategy of the MHPCS comprises three control loops; dc-link voltage controller, power management controller, and load current sharing... 

    A new control strategy for a multi-bus MV microgrid under unbalanced conditions

    , Article IEEE Transactions on Power Systems ; Volume 27, Issue 4 , 2012 , Pages 2225-2232 ; 08858950 (ISSN) Hamzeh, M ; Karimi, H ; Mokhtari, H ; Sharif University of Technology
    This paper proposes a new control strategy for the islanded operation of a multi-bus medium voltage (MV) microgrid. The microgrid consists of several dispatchable electronically-coupled distributed generation (DG) units. Each DG unit supplies a local load which can be unbalanced due to the inclusion of single-phase loads. The proposed control strategy of each DG comprises a proportional resonance (PR) controller with an adjustable resonance frequency, a droop control strategy, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and share the average power components among the DG units. The NSIC is used to... 

    Extraction of harmonics and reactive current for power quality enhancement

    , Article International Symposium on Industrial Electronics 2006, ISIE 2006, Montreal, QC, 9 July 2006 through 13 July 2006 ; Volume 3 , 2006 , Pages 1673-1678 ; 1424404975 (ISBN); 9781424404971 (ISBN) Karimi Ghartemani, M ; Mokhtari, H ; Sharif University of Technology
    A detection technique for extraction of total harmonics, individual harmonics, and reactive current components is introduced and its performance is evaluated. The detection algorithm is then adopted as part of the control system of a single-phase active power filter (APF) to provide the required signals for harmonic filtering and reactive power compensation. Performance of the overall system is evaluated based on digital time-domain simulation studies. The APF control system including the signal processing algorithms are implemented in Matlab/Simulink Fixed-Point Blockset to accommodate bit-length limitation which is a crucial factor in digital implementation. The power system including the...