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Total 72 records

    Design of an optimised 2.5 GHz CMOS differential LC oscillator

    , Article IEE Proceedings: Microwaves, Antennas and Propagation ; Volume 151, Issue 2 , 2004 , Pages 167-172 ; 13502417 (ISSN) Dehghani, R ; Atarodi, S. M ; Sharif University of Technology
    2004
    Abstract
    An analytic method to predict the oscillation amplitude and supply current values of a differential CMOS oscillator is presented. A simplified model to predict the phase noise performance for this type of oscillator is developed. Using this method, it becomes possible to design an optimised oscillator in terms of a minimum phase noise and low power consumption. The validity of the method has been verified by designing a LC CMOS oscillator using 0.25 μm CMOS technology. The predictions are in good agreement with simulation results over a wide range of the supply voltage  

    Effect of motor speed on the optimum operating point of direct torque controlled induction motor

    , Article 6th International Conference on Electrical Machines and Systems, ICEMS 2003, 9 November 2003 through 11 November 2003 ; Volume 2 , 2003 , Pages 619-622 ; 750626210X (ISBN); 9787506262101 (ISBN) Kaboli, S ; Zolghadri, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2003
    Abstract
    The flux and torque hysteresis bands are the only gains to be adjusted in direct torque control (DTC). The torque ripple and harmonic loss of motor and switching loss of inverter are greatly influenced by them. In this paper the effects of flux and torque hysteresis bands on inverter switching loss, harmonic loss and torque ripple of induction motor are investigated through a cost function. Minimizing this cost function leads to the optimum value of the hysteresis bands of torque and flux controllers. The effect of motor speed on cost function is also investigated. © 2003 International Academic Publishers/World Publishing Corporation  

    Analyzing and modeling of a new resonance inverter for low power vehicular application

    , Article PECon 2012 - 2012 IEEE International Conference on Power and Energy ; 2012 , Pages 576-581 ; 9781467350198 (ISBN) Mohagheghi, E ; Keipour, A ; Sudi, Z ; Moallemi, M ; Hajihosseinlu, A ; Sharif University of Technology
    2012
    Abstract
    In this paper we proposed a novel inverter to convert a DC voltage to a desired AC voltage. This inverter is designed for variable inductive loads and low output power applications. We proposed a novel simple PWM method which enables the inverter to keep the output current at six times more than the rated output current, without reducing output voltage value. In addition, based on a simple use of resonance in the circuit, the new inverter can raise the output voltage to extremely high amplitude for a relatively short time. These characteristics make the proposed inverter is useful for some industrial applications such as electrical vehicle. The new configuration of the circuit consists of a... 

    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
    Abstract
    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  

    A diversity based reconfigurable method for fault tolerant control of induction motors

    , Article International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 2006. SPEEDAM 2006, Taormina, 23 May 2006 through 26 May 2006 ; Volume 2006 , 2006 , Pages 66-71 ; 1424401941 (ISBN); 9781424401949 (ISBN) Tahami, F ; Shojaei, A ; Ahmadi Khatir, D ; Sharif University of Technology
    2006
    Abstract
    AC motor drive systems are sensitive to faults occurring at the power inverter, or at the control system. A novel fault tolerant Field Oriented Control system for induction motors is introduced. The system maintains speed control in the event of sensors malfunction and adverse signal conditions, providing enhanced reliability. The system comprises four different flux estimators which are fused by a Fuzzy aggregation system in order to give a reliable estimate of motor flux. The proposed control system is an effective and easy to implement method giving a potential for motor drive reliability enhancement. © 2006 IEEE  

    A geometric approach to fault detection and isolation in a grid-connected inverter

    , Article IEEE Transactions on Control Systems Technology ; Volume 29, Issue 6 , 2021 , Pages 2622-2629 ; 10636536 (ISSN) Mashreghi, A ; Namvar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    We present a nonlinear geometric approach to fault detection and isolation (FDI) in a grid-connected inverter system. Open-switch faults in inverter power transistors together with faults in grid voltages and source current sensors are detected and isolated in the presence of disturbance. The detection process is based on dynamic model of an inverter, including a dc-bus capacitor and an output $RL$ filter. The proposed FDI system does not rely on balanced or zero-sum conditions in the grid point and is functional under nonsinusoidal voltages and currents. © 1993-2012 IEEE  

    Optimal selection of voltage sag mitigation solution based on event tree method

    , Article PQ 2012: 8th International Conference - 2012 Electric Power Quality and Supply Reliability, Conference Proceedings ; 2012 , p. 119-124 ; ISBN: 9781470000000 Yasir, M ; Kazemi, S ; Lehtonen, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
    Abstract
    Modern commercial operations consist of critical equipments that are more susceptible to voltage sag events. The consistent and smooth running of these operations is often disrupted by voltage sags. Diverse range of solutions exist which can enhance the ride through capability of sensitive devices. This paper presents various voltage dip mitigation solutions and a methodology for analyzing the effectiveness and practical viability of these solutions. The proposed approach is based on event tree method which gives an indication about the extent of process interruption in the event of voltage sags. A case study is conducted in the paper with different combinations of practical mitigation... 

    Stable operation of grid connected Cascaded H-Bridge inverter under unbalanced insolation conditions

    , Article 2013 3rd International Conference on Electric Power and Energy Conversion Systems, EPECS 2013 2013 ; 2013 ; 9781479906888 (ISBN) Eskandari, A ; Javadian, V ; Iman Eini, H ; Yadollahi, M ; Sharif University of Technology
    2013
    Abstract
    This paper presents a single-phase Cascaded H-Bridge (CHB) inverter for photovoltaic applications. The proposed control strategy permits the optimum control of each string of PV panels in different insolation conditions. Based on the presented mathematical analysis, an analytic constraint is derived to check the stable operation of the inverter. A modified MPPT control strategy is also proposed based on this new condition. This strategy enhances the stability margins of the system by changing the operating point of some PV arrays. In this approach, the extracted power from high power cell is reduced to prevent instability issue and to avoid injection of highly distorted current into the... 

    Optimal selection of voltage sag mitigation solution based on event tree method

    , Article PQ 2012: 8th International Conference - 2012 Electric Power Quality and Supply Reliability, Conference Proceedings ; 2012 , Pages 119-124 ; 9781467319775 (ISBN) Yasir, M ; Kazemi, S ; Lehtonen, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
    2012
    Abstract
    Modern commercial operations consist of critical equipments that are more susceptible to voltage sag events. The consistent and smooth running of these operations is often disrupted by voltage sags. Diverse range of solutions exist which can enhance the ride through capability of sensitive devices. This paper presents various voltage dip mitigation solutions and a methodology for analyzing the effectiveness and practical viability of these solutions. The proposed approach is based on event tree method which gives an indication about the extent of process interruption in the event of voltage sags. A case study is conducted in the paper with different combinations of practical mitigation... 

    Optimal LQR-based multi-loop linear control strategy for UPS inverter applications using resonant controller

    , Article Proceedings of the IEEE Conference on Decision and Control, 12 December 2011 through 15 December 2011, Orlando, FL ; 2011 , Pages 3080-3085 ; 01912216 (ISSN) ; 9781612848006 (ISBN) Hasanzadeh, A ; Edrington, C. S ; Maghsoudlou, B ; Mokhtari, H ; Sharif University of Technology
    2011
    Abstract
    This paper presents an optimal multi-loop control structure for uninterruptible power supply (UPS) applications which use voltage source inverter (VSI) coupled with LC filter. A resonant controller ensures tracking of sinusoidal voltage reference and rejection of sinusoidal current disturbance with no steady-state error if the loop remains stable. The challenges are reduction of output total harmonic distortion (THD), improving damping of the LC resonance frequency and preventing generation of fast closed-loop modes which go beyond the frequency range of inverter with limited switching frequency. An extension of the classic linear quadratic regulator (LQR) is proposed which addresses the... 

    Short-circuit analysis in three-phase quasi-Z-source inverter

    , Article 17th IEEE International Conference on Environment and Electrical Engineering and 2017 1st IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2017, 6 June 2017 through 9 June 2017 ; 2017 ; 9781538639160 (ISBN) Yaghoubi, M ; Moghani, J. S ; Noroozi, N ; Zolghadri, M. R ; IEEE EMC Society; IEEE Industry Applications Society (IAS); IEEE Power and Energy Society (PES) ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    In this paper, the short-circuit fault in three-phase quasi-Z-source inverter (q-ZSI) is analyzed and a linear model is proposed for the short-circuit analysis. The proposed model is based on the state space equations of the system. By using this model, the most critical situation during short-circuit fault is recognized; the maximum reaction time for the protection system could be estimated and elements that are prone to failure are identified as well. The analysis is categorized into two groups, leg fault and switch fault. The linear model is confirmed by simulation of 1kw three-phase q-ZSI. © 2017 IEEE  

    Reducing output voltage THD of a three-phase inverter with non-linear load using disturbance observer

    , Article 8th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2017, 14 February 2017 through 16 February 2017 ; 2017 , Pages 431-436 ; 9781509057665 (ISBN) Valizade Alavi, S ; Tahami, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    Non-linear loads such as rectifiers are growing in industry. Three phase inverter with non-linear load can lead to highly distorted output voltage. This paper proposes a method for reducing voltage THD in three phase inverters with non-linear load. The proposed method considers the load current as a disturbance and provide a control strategy to reject it using the disturbance observer method. This method doesn't need any additional sensors or hardware and is implemented digitally in controller. Simulation results show that the presented method will reduce the total harmonic distortion of the output voltage. © 2017 IEEE  

    Improvement of post-fault performance of a cascaded h-bridge multilevel inverter

    , Article IEEE Transactions on Industrial Electronics ; Volume 64, Issue 4 , 2017 , Pages 2779-2788 ; 02780046 (ISSN) Ouni, S ; Zolghadri, M. R ; Khodabandeh, M ; Shahbazi, M ; Rodríguez, J ; Oraee, H ; Lezana, P ; Schmeisser, A. U ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    This paper is focused on improving the post-fault performance of cascaded H-bridge multilevel inverters by decreasing the common-mode voltage. First, an algorithm is proposed to determine the optimal post-fault state among all possible states, which have the same maximum available voltage. Furthermore, a modified technique is proposed to calculate the references of inverter phase voltages under faulty conditions. This technique leads to a decrease in the common-mode voltage when the required output voltage is less than its maximum value. These solutions are mutually employed in the post-fault control system. Simulation and experimental results confirm the effectiveness of the proposed... 

    Voltage control of three phase inverters by using active disturbance rejection control

    , Article 30th Power System Conference, PSC 2015, 23 November 2015 through 25 November 2015 ; 2017 , Pages 169-176 ; 9781509027057 (ISBN) Mehrabankhomartash, M ; Toulabi, M. R ; Ranjbar, A. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    Control of three phase inverters is of paramount importance in the realm of control applications. In this regard, this paper proposes active disturbance rejection control (ADRC) scheme as a new method for voltage control of three phase inverters in UPS applications. The main advantage of ADRC refers to the fact that it is model independent. In this paper, the controller is composed of a double loop structure including an inner current loop and outer voltage loop. This structure is used in a three phase inverter in order for implementation of voltage control. To draw a comparison between ADRC and PI as the common control method, a case study has been simulated in SIMULINK. Simulation results... 

    Robust tuning of transient droop gains based on kharitonov's stability theorem in droopcontrolled microgrids

    , Article IET Generation, Transmission and Distribution ; Volume 12, Issue 14 , 2018 , Pages 3495-3501 ; 17518687 (ISSN) Mahdian Dehkordi, N ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
    Abstract
    This study addresses the robust stability analysis for an islanded microgrid with droop-controlled inverter-based distributed generators (DGs). Owing to large load changes, microgrid structure reconfiguration, and higher-power demands, the low-frequency (LF) dominant modes of a microgrid stir toward unstable zone and make the system more oscillatory or even unstable. In this study, a robust two-degree-of-freedom (2DOF) decentralised droop controller, which is the combination of the conventional droop with a robust transient droop function, is utilised for each inverter-based DG unit. Unlike conventional tuning of 2DOF droop controllers, a new design procedure is proposed to robustly... 

    Comparison of common-mode voltage in three-phase quasi-Z-source inverters using different shoot-through implementation methods

    , Article Proceedings - 2018 IEEE 12th International Conference on Compatibility, Power Electronics and Power Engineering, CPE-POWERENG 2018 ; 4 June , 2018 , Pages 1-6 ; 9781538625088 (ISBN) Noroozi, N ; Zolghadri, M. R ; Yaghoubi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    In Z-source family inverters, shoot-through (ST) states are applied as a part of passive state in each switching cycle. The distribution of ST intervals along a switching period affects the system parameters as total harmonic distortion (THD), switching loss and common-mode voltage (CMV). In this paper, ST methods in a three-phase quasi-Z-source inverter (q-ZSI) are compared due to the CMV level. High-frequency harmonics of CMV cause leakage current flow in a transformerless grid-connected photovoltaic (PV) system. Through the comparison of the ST methods, the method with minimum CMV is identified. The experimental results are Prasented for a low voltage q-ZSI prototype. © 2018 IEEE  

    Non isolated ZCT DC-DC converter for high step-up, high efficiency applications using resonant PWM technique

    , Article 9th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2018, 13 February 2018 through 15 February 2018 ; Volume 2018-January , April , 2018 , Pages 398-403 ; 9781538646977 (ISBN) Sadeghpoor, D ; Habibagahi, I ; Zolghadri, M. R ; Atarodi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    This paper presents a new topology for DC/DC converter which satisfies the need for high gain, high efficiency, low weight and low cost for renewables application. This topology is a novel approach of Resonant PWM converters which produces high output voltage with soft switching method (ZVS). The converter can be controlled both by PWM and frequency variation method. The main characteristics of this structure are illustrated using simulation results and compared with other well-known structures. © 2018 IEEE  

    Energy regeneration technique for electric vehicles driven by a brushless DC motor

    , Article IET Power Electronics ; Volume 12, Issue 13 , 2019 , Pages 3397-3402 ; 17554535 (ISSN) Bahrami, M ; Mokhtari, H ; Dindar, A ; Sharif University of Technology
    Institution of Engineering and Technology  2019
    Abstract
    The development of energy regeneration capability in electric vehicles can extend their driving range making them a competent alternative for conventional internal combustion engine vehicles. In this study, a novel energy regeneration technique, called a two-boost method, for electric vehicles driven by a brushless DC (BLDC) motor, a widely used motor in vehicular technology, is proposed. Based on this technique, the BLDC motor driver, which is selected to be a three-phase inverter, is converted into two simultaneous boost converters during energy regeneration periods in order to transfer energy from the BLDC motor into the battery and provide the braking force. Also, this method is compared... 

    A switched-capacitor inverter with optimized switch-count considering load power factor

    , Article 45th Annual Conference of the IEEE Industrial Electronics Society, IECON 2019, 14 October 2019 through 17 October 2019 ; Volume 2019-October , 2019 , Pages 4959-4964 ; 9781728148786 (ISBN) Jahan, H. K ; Tarzamni, H ; Kolahian, P ; Hosseini, S. H ; Tahami, F ; Blaabjerg, F ; Sharif University of Technology
    IEEE Computer Society  2019
    Abstract
    In this paper, an optimized topology for switched-capacitor (SC) multilevel inverter is proposed. The proposed topology, which is referred to as Optimized Switched-Capacitor Multilevel Inverter (OSC-MI), offers a boosted staircase voltage by using only one dc source and fewer switches count. Since each industrial load requires a specific power factor (PF), an optimal converter can be designated in a way that it both satisfies the required PF and employs fewer switches and gate drivers. Therefore, the main strategy of reducing switches count in the proposed topology is to design the converter according to the required PF value. In this paper, the theoretical analytics and comparison results... 

    Fault detection and protection strategy for islanded inverter-based microgrids

    , Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; 2019 ; 21686777 (ISSN) Zarei, S. F ; Mokhtari, H ; Blaabjerg, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    This paper proposes a fault detection and protection strategy for islanded inverter-based microgrids (IBMGs). Reliable and accurate protection is one of the main challenges in the proliferation of modern microgrids (MGs). Considering the limited fault current of the voltage-frequency controlled inverter-based distributed energy resources (VF-IBDERs), the protection is more challenging in islanded IBMGs. In this regard, the control scheme of VF-IBDER with a current limiting strategy plays an important role. Due to the limited fault currents close to the converter nominal current, the conventional fault detection methods do not work properly. In addition, bi-directional fault currents worsen...