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Total 94 records

    Hybrid Modeling and Control of Series Resonant Converters

    , M.Sc. Thesis Sharif University of Technology Jafari, Mohammad Hossein (Author) ; Tahami, Farzad (Supervisor)
    Abstract
    Nowadays, despite the special position of power electronic converters in the world, and the fact that they become an integral part of human life, still in the wake of a serious necessity the development process has not stopped and the increasingly fast pace, it opens up new horizons. This important necessity emerges from the environmental concerns regarding consumption of fossil fuels and their limited and imbalanced distribution which can be effectively addressed with the use renewable energy systems. By improving the quality of the semiconductor switches and offering new topologies in different functions as well as using new control methods, scholars try to develop enhanced converters in... 

    A new t-type direct AC/AC converter

    , Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 247-252 ; 9781479976539 (ISBN) Khodabandeh, M ; Zolghadri, M. R ; Noroozi, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    In this paper a novel T type scheme for 1-phase direct ac/ac converters is proposed. In this topology, frequency changing takes place directly (without common DC voltage bus) through three converters that are connected in a T structure. Unity power factor and precise output voltage regulation is achieved through appropriate control of these three converters. H-bridge converters are implemented, as the basic unit, in each branches of T to make the proposed converter. The converter is controlled such that the average active power of each H-bridges remains zero. So capacitors are implemented in DC links of H-bridges. In comparison to conventional back-to-back converters, life time of each... 

    High-efficiency low-cost AC/AC buck converter with stability analysis

    , Article IET Power Electronics ; Volume 10, Issue 7 , 2017 , Pages 802-807 ; 17554535 (ISSN) Hajimoradi, M ; Mokhtari, H ; Sharif University of Technology
    Abstract
    The commutation issue is the most important limiting factor of expanding AC chopper applications, which in most cases are solved by employing snubber circuits, implementing sensor-based selective switching patterns and utilising resonant circuits. To overcome the commutation problem, this study proposes a novel non-resonant AC/AC buck converter with no snubber circuits and no sensor-based switching patterns. The introduced hardware configuration and the proposed control strategy provide a path for an inductive load current in all switching states. This converter offers higher reliability and efficiency as well as lower cost compared to the AC choppers with snubber circuits or voltage and... 

    Application of neural networks and state-space averaging to DC/DC PWM converters in sliding-mode operation

    , Article IEEE/ASME Transactions on Mechatronics ; Volume 10, Issue 1 , 2005 , Pages 60-67 ; 10834435 (ISSN) Mahdavi, J ; Nasiri, M. R ; Agah, A ; Emadi, A ; Sharif University of Technology
    2005
    Abstract
    A novel output feedback neural controller is presented in this paper for the implementation of sliding-mode control of dc/dc converters. The controller, which consists of a multilayer perceptron, has been trained in order to be robust for large variations of system parameters and state variables. Fast dynamic behavior is the other main advantage of the proposed controller, which allows realization of all beneficial features of the sliding-mode control technique. Other advantages of the controller are simplicity and low cost. Computer simulations have been carried out to investigate the effectiveness of the controller in voltage regulation for a relatively complex dc/dc converter topology of... 

    Temperature integrated load sharing of paralleled modules

    , Article 2006 1st IEEE Conference on Industrial Electronics and Applications, ICIEA 2006, Singapore, 24 May 2006 through 26 May 2006 ; 2006 ; 078039514X (ISBN); 9780780395145 (ISBN) Barnette, J. L ; Zolghadri, M. R ; Walters, M ; Homaifar, A ; Sharif University of Technology
    2006
    Abstract
    Paralleling power modules is designed to share system loads (stresses) equally to improve system reliability. Due to variations in the parameters in the power converter system, temperature mismatches may occur. These mismatches may lead to unequal life expectancy of individual converters in the total system. It is believed that equalizing the operating temperature of the semiconductor devices may improve total system reliability. In this paper a new thermal-based load-sharing scheme for parallel converters is proposed. In this scheme, the load current is redistributed among parallel converters based on the temperature of the converters. The main goal is to minimize the relative temperature... 

    An isolated bidirectional integrated plug-in hybrid electric vehicle battery charger with resonant converters

    , Article Electric Power Components and Systems ; Volume 44, Issue 12 , 2016 , Pages 1371-1383 ; 15325008 (ISSN) Ebrahimi, S ; Akbari, R ; Tahami, F ; Oraee, H ; Sharif University of Technology
    Taylor and Francis Inc  2016
    Abstract
    Plug-in hybrid electric vehicles draw electricity from the electrical grid and store energy in their batteries. To increase charge availability for plug-in hybrid electric vehicles, on-board chargers can be used, which should be small in size and lightweight. In this article, an on-board bidirectional soft-switched battery charger is proposed that utilizes a phase-shift-controlled dual-bridge series resonant converter with isolation. The bidirectional characteristic of proposed charger makes it suitable for vehicle-to-grid operation (i.e., injecting power from the vehicle to the grid) in smart grids. A switching control scheme is also proposed to provide soft-switching operation for all... 

    Output voltage quality intensification of diode clamped multilevel inverters using FM PWM technique

    , Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 98-102 ; 9781467301114 (ISBN) Najmi, V ; Ebrahimi, S ; Oraee, H ; Sharif University of Technology
    2012
    Abstract
    Improvement in switching techniques is one of the effective methods for increasing the voltage quality in Multilevel Inverters. In this paper, a novel switching technique using frequency modulation is proposed to achieve high quality output voltage of multilevel inverters. This method is employed to different configurations of multilevel inverters consist of Diode Clamped (or Neutral Point Clamped), Flying Capacitor and Cascaded H-bridge. Each multilevel inverter which utilizes this technique is modeled and simulated to investigate the performance of this method by the help of MATLAB/Simulink software. The Results show that this innovative method considerably reduces total harmonic... 

    Fast fault detection method for modular multilevel converter semiconductor power switches

    , Article IET Power Electronics ; Volume 9, Issue 2 , 2016 , Pages 165-174 ; 17554535 (ISSN) Haghnazari, S ; Khodabandeh, M ; Zolghadri, M. R ; Sharif University of Technology
    Institution of Engineering and Technology  2016
    Abstract
    This study proposes a new fault detection method for modular multilevel converter (MMC) semiconductor power switches. While in common MMCs, the cells capacitor voltages are measured directly for control purposes, in this study voltage measurement point changes to the cell output terminal improving fault diagnosis ability. Based on this measurement reconfiguration, a novel fault detection algorithm is designed for MMCs semiconductor power switches. The open circuit and short circuit faults are detected based on unconformity between modules output voltage and switching signals. Simulation and experimental results confirm accurate and fast operation of the proposed method in faulty cell... 

    Synchronverter-enabled DC power sharing approach for LVDC microgrids

    , Article IEEE Transactions on Power Electronics ; Volume 32, Issue 10 , 2017 , Pages 8089-8099 ; 08858993 (ISSN) Peyghami, S ; Davari, P ; Mokhtari, H ; Loh, P. C ; Blaabjerg, F ; Sharif University of Technology
    Abstract
    In a classical ac microgrid (MG), a common frequency exists for coordinating active power sharing among droop-controlled sources. Like the frequency-droop method, a voltage-based droop approach has been employed to control the converters in low voltage direct current (LVDC) MGs. However, voltage variation due to the droop gains and line resistances causes poor power sharing and voltage regulation in dc MG, which in most cases are solved by a secondary controller by using a communication network. To avoid such an infrastructure and its accompanied complications, this paper proposes a new droop scheme to control dc sources by introducing a small ac voltage superimposed onto the output dc... 

    RCD snubber design based on reliability consideration: A case study for thermal balancing in power electronic converters

    , Article Microelectronics Reliability ; Volume 88-90 , 2018 , Pages 1311-1315 ; 00262714 (ISSN) Parvari, R ; Zarghani, M ; Kaboli, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    In a turn-off RCD snubber, the capacitor value is usually optimized in order to minimize the power dissipated in the switch and snubber circuit. However, it may not be the best value of the snubber capacitor from the reliability point of view. In this paper, the capacitor value is optimized based on reliability considerations. Proposed method presents a new design to achieve the maximum reliability for the set of switch and its snubber. Mathematical analysis of the proposed method is conducted in MATLAB environment. Also, the experimental results are presented for validity of the theoretical analysis. © 2018 Elsevier Ltd  

    Composite system reliability assessment incorporating an interline power-flow controller

    , Article IEEE Transactions on Power Delivery ; Volume 23, Issue 2 , 2008 , Pages 1191-1199 ; 08858977 (ISSN) Moghadasi, S. M ; Kazemi, A ; Fotuhi Firuzabad, M ; Edris, A. A ; Sharif University of Technology
    2008
    Abstract
    The impact of an interline power-flow controller (IPFC) on composite system delivery point and overall system reliability indices is examined in this paper. In this application, the IPFC with dc transmission lines is employed in a system for coordinated control of line impedances of two, distance away, transmission lines with the objective of managing power flows on the two lines. It is also used to balance the real power being transferred between the compensated lines. For this purpose, the reliability model associated with a converter station has been developed and incorporated in an IPFC reliability model. A number of reliability indices are calculated at both the loadpoint and system... 

    Application of random PWM technique for reducing the conducted electromagnetic emissions in active filters

    , Article IEEE Transactions on Industrial Electronics ; Volume 54, Issue 4 , 2007 , Pages 2333-2343 ; 02780046 (ISSN) Kaboli, S ; Mahdavi, J ; Agah, A ; Sharif University of Technology
    2007
    Abstract
    A pulsewidth modulation (PWM)-controlled active filter generates harmonics at the switching frequency and its multiples in the RF range, and the concentrated power spectrum may produce electromagnetic interference (EMI) problems. In this paper, the random PWM (RPWM) technique is applied in order to spread the noise spectrum over a wide range, thus, considerably reducing the amplitudes of these harmonics and the consequent EMI problems. To study the operation of active filters, the case of an ac/dc converter along with a power-factor corrector is considered as a nonlinear load and a series active filter, respectively. A line impedance stabilization network is used to study the RF noise... 

    Power flow control of a matrix converter based micro-turbine distributed generation system

    , Article 2006 IEEE Power Engineering Society General Meeting, PES, Montreal, QC, 18 June 2006 through 22 June 2006 ; 2006 ; 1424404932 (ISBN); 9781424404933 (ISBN) Nikkhajoei, H ; Karimi Ghartemani, M ; Sharif University of Technology
    IEEE Computer Society  2006
    Abstract
    This paper presents a power flow controller for a matrix converter as the power electronic interface between a high-speed micro-turbine generator and a utility distribution system. The matrix converter converts the high-frequency of a micro-turbine generator to a conventional frequency of the utility system, based on a novel switching strategy. The controller regulates magnitude and phase-angle of the converter output voltage to accommodate real and reactive power flow requirements of the utility system. Performance of the matrix converter based microturbine generation system including the power flow controller is evaluated based on digital time-domain simulation studies in the PSCAD/EMTDC... 

    On the suitability of modeling approaches for power electronic converters

    , Article International Symposium on Industrial Electronics 2006, ISIE 2006, Montreal, QC, 9 July 2006 through 13 July 2006 ; Volume 2 , 2006 , Pages 1486-1491 ; 1424404975 (ISBN); 9781424404971 (ISBN) Poshtan, M ; Kaboli, S ; Mahdavi, J ; Sharif University of Technology
    2006
    Abstract
    This paper is a summary and in-depth evaluation of some popular models for power electronic converters. Proper examples are given to support the evaluation with a complete comparison between the actual and simulated results. The paper presents the effort behind the design and analysis of DC-DC Converters and discuses their features. Some advantages and disadvantages of the studied models and the complicities of the nonlinear structure of the switching function of the converters are explained here. The paper offers some useful criteria for future selection and development on different DC-DC Converters. © 2006 IEEE  

    A hybrid control approach for LLC resonant converter

    , Article 12th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2021, 2 February 2021 through 4 February 2021 ; 2021 ; 9780738111971 (ISBN) Barzkar, A ; Tahami, F ; Barzkar, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    In this paper, a novel hybrid control approach is proposed to control the LLC resonant converter. Since the converter consists of both continuous variables and logical variables, it is intrinsically hybrid. Apart from that, because of fast dynamics of the converter and the fact that there is no closed form solution for discontinuous conduction modes (DCM), modeling and control of the LLC resonant converter is still a challenge. In the authors' previous work, a systematic model was proposed for the converter, the direct piecewise affine model. In this paper, an appropriate controller based on the proposed model is represented and the design procedure is discussed in details; the block diagram... 

    Extended dynamic matrix control design for a DC-DC power converter

    , Article 37th Southeastern Symposium on System Theory, SST05, Tuskegee, AL, 20 March 2004 through 22 March 2004 ; Volume 37 , 2005 , Pages 191-195 Amirifar, R ; Sharif University of Technology
    2005
    Abstract
    EDMC is an extended version of the dynamic matrix control (DMC) approach to control nonlinear processes. In this method, control input is determined based on linear model approximation of the process in each control/optimization interval. The difference between linear and nonlinear models of the process is considered as the known part of the feedback signal in DMC control formulation. Usually the fixed point or the secant method is applied to reduce the difference between two models. In this paper, an EDMC controller is designed for a DC-DC power converter of the boost type. The behavior of the scheme is discussed with the transient and steady state response to step and sinusoidal... 

    Application of packet control method for a high power high voltage flyback converter to reduce noise influence

    , Article 2005 European Conference on Power Electronics and Applications, Dresden, 11 September 2005 through 14 September 2005 ; Volume 2005 , 2005 , Pages 10-19 ; 9075815085 (ISBN); 9789075815085 (ISBN) Kaboli, S ; Sadriyeh, S. M. R ; Mohammadi, A ; Zolghadri, M. R ; Emadi, A ; Sharif University of Technology
    IEEE Computer Society  2005
    Abstract
    In the regulated switching power supplies, the output voltage is usually sampled across a resistive voltage divider. In high voltage applications, the resistance of the voltage divider is very high in order to reduce its power loss. Therefore, these resistors are very good receivers of environment noise. This paper introduces a new control method for a high power, high voltage Flyback converter insensitive to the noise caused by ringing due to the leakage reactance of a high voltage Flyback converter. In this method, output voltage is sampled in an intentionally extended cycle to be sure that all the oscillations are damped. Therefore there is no need to additional damping circuits and... 

    Application of neural networks and state space averaging to a DC/DC PWM converter in sliding mode operation

    , Article IECON Proceedings (Industrial Electronics Conference) ; Volume 1 , 2000 , Pages 172-177 Mahdavi, J ; Nasiri, M. R ; Agah, A ; Sharif University of Technology
    IEEE Computer Society  2000
    Abstract
    A novel output feedback neural controller is presented for the implementation of sliding mode control of DC/DC converters. The controller, which consists of a multilayer perceptron, has been trained so as to be robust for large variations of system parameters and state variables. Fast dynamic behavior is the other main advantage of the proposed controller, which allows realization of all the beneficial features of sliding mode control technique. Other advantages of the controller are simplicity and low cost. Computer simulations are carried out to investigate the effectiveness of the controller in voltage regulation for a relatively complex topology such as a Cuk converter. Simulation... 

    Integrated bidirectional isolated soft-switched battery charger for vehicle-to-grid technology using 4-Switch 3Φ-rectifier

    , Article IECON Proceedings (Industrial Electronics Conference) ; November , 2013 , Pages 906-911 ; 9781479902248 (ISBN) Ebrahimi, S ; Taghavi, M ; Tahami, F ; Oraee, H ; Sharif University of Technology
    2013
    Abstract
    Battery and plug-in hybrid vehicles equipped with bidirectional battery chargers are capable of supplying power to the electric grid according to power system demand. This technology is called 'vehicle to grid' or V2G. A bidirectional on-board charger can be used to improve the charge availability. An on-board charger should have small size and light weight. On the other hand, the charger must minimize power quality impact, draw current at high power factor to maximize power from an outlet. In this paper, a new three-phase integrated bidirectional isolated soft-switched battery charger is proposed which is appropriate for vehicle to grid technology. The charger utilizes a 4-switch... 

    Open-and short-circuit switch fault diagnosis for nonisolated DC-DC converters using field programmable gate array

    , Article IEEE Transactions on Industrial Electronics ; Volume 60, Issue 9 , October , 2013 , Pages 4136-4146 ; 02780046 (ISSN) Shahbazi, M ; Jamshidpour, E ; Poure, P ; Saadate, S ; Zolghadri, M. R ; Sharif University of Technology
    2013
    Abstract
    Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc-dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For...