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    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... 

    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, 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... 

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

    , Article IEEE Transactions on Control Systems Technology ; November , 2020 , Pages: 1-8 Mashreghi, A ; Namvar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    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. IEEE  

    Extending protection selectivity in low voltage DC microgrids using compensation gain and artificial line inductance

    , Article Electric Power Systems Research ; Volume 188 , 2020 Shamsoddini, M ; Vahidi, B ; Razani, R ; Nafisi, H ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Vulnerability of power electronic converters in DC microgrids in case of fault occurrence in DC cables necessitates using a fast fault detection and isolation scheme. In this paper, a modified, fast and selective protection scheme has been presented, which provides the required tripping of low voltage DC (LVDC) microgrids. This protection scheme has been developed based on the natural characteristics of the fault current, in which the first and second derivatives of the fault current have been employed to define thresholds for discriminating between faulted and non-faulted situations. To enhance fault detection capability of the protection scheme, definition of thresholds have been improved... 

    A series stacked IGBT switch to be used as a fault current limiter in HV high-power supplies

    , Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; Volume 9, Issue 5 , 2021 , Pages 6300-6314 ; 21686777 (ISSN) Mohsenzade, S ; Zarghani, M ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    The safe operating condition for the vacuum tubes is very important and critical since they are very expensive and delicate. Providing limited short circuit energy for the vacuum tube and fast transferring from the short circuit to the nominal operation state are absolutely necessary. Extant protection strategies threat the availability of the vacuum tubes. In addition, they cannot completely protect the tube due to the delay of the fault detection system. This article proposes a high voltage (HV) short circuit fault current limiter which can limit the short circuit energy of the system inherently. The proposed structure activates automatically when the current exceeds the predetermined... 

    Fast detection of open-switch faults with reduced sensor count for a fault-tolerant three-phase converter

    , Article 2011 2nd Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2011 ; 2011 , Pages 546-550 ; 9781612844213 (ISBN) Shahbazi, M ; Zolghadri, M ; Poure, P ; Saadate, S ; Sharif University of Technology
    Abstract
    Fast fault detection and reconfiguration is necessary in power electronic converters in lots of applications to prevent further damage and to make possible the continuity of service. In this paper a very fast fault detection scheme is presented that minimizes the use of voltage sensors. A fault tolerant topology is studied. Control and fault detection system are implemented on a single FPGA and hardware in the loop experiments are performed to evaluate the detection scheme, the digital controller and the structure  

    FPGA-based fault tolerant scheme with reduced extra-sensor number for WECS with DFIG

    , Article Proceedings - ISIE 2011: 2011 IEEE International Symposium on Industrial Electronics, 27 June 2011 through 30 June 2011 ; 2011 , Pages 1595-1601 ; 9781424493128 (ISBN) Shahbazi, M ; Gaillard, A ; Poure, P ; Zolghadri, M. R ; Sharif University of Technology
    2011
    Abstract
    Fast fault detection and converter reconfiguration is necessary for fault tolerant doubly fed induction generator (DFIG) in wind energy conversion systems (WECS) to prevent further damage and to make possible the continuity of service. Extra sensors are needed in order to detect the faults rapidly. In this paper, a very fast FPGA-based fault detection scheme is presented that minimizes the number of additional voltage sensors. A fault tolerant converter topology for this application is studied. Control and fault detection system are implemented on a single FPGA and Hardware in the Loop experiments are performed to evaluate the proposed detection scheme, the digital controller and the fault... 

    PMU Based Fault Location on Transmission Lines

    , M.Sc. Thesis Sharif University of Technology Salimi, Saeed (Author) ; Ranjbar, Alimohammad (Supervisor)
    Abstract
    One of the most essential part of power system are transmission lines. Transmission of power from production centers to consumption centers is duty of these lines. Any disturbance in this duty make great losses to producers and consumers. One of the most disturbance in transmission lines are short circuits that occurred because of various causes. Most faults on transmission lines occurred in stormy weather that make more troubles for fault search. So we need a tool that can find location of fault precisely and quickly. This tool named fault locator. There are many algorithms for fault location and detection on power system transmission lines. These algorithms usually are dependent on very... 

    Criteria for Evaluating Bogie Performance For Sustaining Ride Quality

    , Ph.D. Dissertation Sharif University of Technology Shokouhi Dolat Abadi, Nader (Author) ; Sayyadi, Hassan (Supervisor)
    Abstract
    This thesis proposes a dynamic model for studding influences of suspension components behavior on rail vehicle dynamics. As the air springs are very important isolating component in rail vehicles, a new complete nonlinear air spring model, with taking into consideration of thermo–dynamical effects, is developed. The model coefficients are tuned based on the real test data and it can be easily used in dynamic modeling of air springs. The new proposed vehicle model is a complete track–vehicle model with 70 degree of freedoms which is addressed as a modular type. Experimental results from complete rail–vehicle field test, showed remarkable agreement between proposed model and test results.... 

    Reducing the Energy Overhead of Replication Mechanisms in Distributed Embedded Systems

    , M.Sc. Thesis Sharif University of Technology Salehi Khanghahbar, Mohammad (Author) ; Ejlali, Alireza (Supervisor)
    Abstract
    Distributed embedded systems are widely used in safety-critical applications, such as avionics platform and flight control system. Faults in such applications may cause catastrophic effect. Therefore, these systems must be fault-tolerant and must be designed not only to detect faults but also to recover from faults. Fault tolerance is normally realized on multi-processor system via temporal duplication (time-redundancy) or spatial duplication (hardware-redundancy) depending on the availability of the slack time. Slack time is defined as the difference between the deadline and execution time. Duplication is a common technique to achieve fault tolerance in safety-critical applications, but may... 

    Data Mining Approach for Fault Diagnosis of Power Systemby Wide Area Measurement

    , M.Sc. Thesis Sharif University of Technology Zamani Dehkordi, Payam (Author) ; Ranjbar, AliMohammad (Supervisor)
    Abstract
    Fast and accurate fault diagnosis has a significant role in the power system operation. For a power system to come back to the normal state, the precise fault diagnosis is necessary. The current practice in power system fault diagnosis needs operators in the control center to use data of PR and CB in order to infer the faulted section based on their experiences. Expert systems and artificial intelligence have been suggested as alternatives to the human expert experience and inference. Other model- and optimization-based methods have also been reported for fault diagnosis, provided that similar data is available from the SCADA system.Nevertheless, in large disturbances resulting in partial or... 

    Development a Numerical Algorithm for Differential Relay for Transformer Protection

    , M.Sc. Thesis Sharif University of Technology Gholami, Mohammad (Author) ; Vakilian, Mehdi (Supervisor)
    Abstract
    The goal of this master thesis is to develop a new accurate numerical algorithm for digital differential relay to protect a power transformer. This work employs specially developed software to simplify its input signal processing task which helps to quickly and accurately detect and clear the transformer internal faults. The available commercial transformer digital differential relays lack the required sensitivity to detect turn to turn faults when a few numbers of turns (less than 10% of the winding) are involved. This work presents a new equivalent circuit for transformer when a turn to turn fault occurs on either winding. This equivalent circuit helped to develop an accurate algorithm for... 

    Disturbance Diagnosis In Plant-wide Processes

    , M.Sc. Thesis Sharif University of Technology Juyandeh, Sepideh (Author) ; Nobakhti, Amin (Supervisor)
    Abstract
    In continous chemical process, disturbances usually propagate along the process. This project describes a data-driven method for identifying the direction of propagation of disturbances using historical process data. The concept is the application of Transfer Entropy, a method based on the conditional probability density functions that measures directionality of variation. For demonstration purposes the transfer entropy method is used to isolate the root-cause of the disturbance in the Tennassee Eastman benchmark process  

    Identification and Attractiveness Assessment of Technologies Used in Aging Aircraft Life Extension

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Morteza (Author) ; Abedian, Ali (Supervisor)
    Abstract
    Lifetime extension would be a necessary preventive action to halt micro cracks expansion on the airplane external surface. To decide about whether to perform this operation, one should examine technological maturity, costs and technical parameters. Technical status in lifetime extension is one of the major drivers of this decision which should be considered in the first step of technology management process which is known as the technology attractiveness step. In this research, major technologies of rejuvenation is examined and categorized by the technology mapping. Also, key processes of rejuvenation and technological fields ranking has been determined by the procedural view tools of the... 

    Design and Development of the Automated Irrigation Channel Pilot

    , M.Sc. Thesis Sharif University of Technology Bakhshi, Mahsa (Author) ; Farhadi, Alireza (Supervisor)
    Abstract
    The present thesis is concerned with design and development of automated irrigation system pilot. This system is obtained by equipping each regulating gate of irrigation network with a controlling hardware. This hardware is designed and developed in this project for Iran’s regulating gate, which are either slide gate or radial gate. This hardware consists of a) Ultrasonic sensor for measure gate upstream water level, b) Wireless modem for exchanging measurements between automated gates, c) controller, d) Electric motor and driver, e) shaft encoder and f) adaptor. The satisfactory performance of this hardware is shown via several experiments on the pilot  

    A New Robust Fault Detection Approach to Nonlinear Dynamical Systems

    , M.Sc. Thesis Sharif University of Technology Jabbari, Biyouk (Author) ; Sadati, Nasser (Supervisor)
    Abstract
    In this thesis the problem of optimal robust fault detection has been studied. Optimal Fault Detection Filter (FDF) design, by using a Linear Matrix Inequality (LMI) structure for both linear systems with polytopic uncertainties and nonlinear Lipschitz systems has been considered. In this regard, a novel LMI is introduced which is capable of calculating the maximum lower bound of H− index with great accuracy.Then, based on the parameter-dependent Lyapunov function and the property of having convexity in combination of certain state space equations, the result is extended to polytopic uncertain systems. Afterward the design of an optimal observer-based residual generator, in the sense of... 

    Fault Detection and Identification in Robotic Systems

    , M.Sc. Thesis Sharif University of Technology Baghbahari, Masoud (Author) ; Namvar, Mehrzad (Supervisor)
    Abstract
    Fault detection and identification is one of the major issues and challenges in the field of engineering and currently is considered as an active field of research. As the replacement of human in dangerous or inaccessible environments, robotic mechanical systems can be used which exposes to a variety of stresses and actions that causes faults in the actuators or sensors. Accordingly, detection of fault at the earliest possible time after the fault accurence and its identification such that real flaw waveform is being extracted, can prevent more damage to the system without any need to human immediate interference. Model based approach in recent decades has shown their ability to detection... 

    Fault Detection in Robotic Swarm

    , M.Sc. Thesis Sharif University of Technology Mollahossein, Mojtaba (Author) ; Alasti, Aria (Supervisor) ; Salarieh, Hassan (Co-Supervisor)
    Abstract
    Fault detection in swarm robots is one of the most important issues that has drawn a lot of scientists’ attention. Previous studies have shown a lot of problems regarding this issue, such as dependency of data-based methods to mission and high complexity of model-based methods on the condition that nonlinear models are used. Extended information filter is an applicable method for fault detection because it could turn the inverse of a big matrix to a simple summation of information that is so desired in terms of calculations. The goal of this study is to identify the agents with fault in swarm robots online by modifying the extended information filter. In this study, it has been attempted to... 

    Crack Detection in a Rotor using Traditional Mode Shape Based Modal Analysis Methods and Experimental Evaluation

    , M.Sc. Thesis Sharif University of Technology Ashtiani, Mohammad Reza (Author) ; Mohammad Navazi, Hossein (Supervisor)
    Abstract
    Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have... 

    Turn-to-Turn Fault Detection in Power Transformers in the Presence of Inrush Current

    , M.Sc. Thesis Sharif University of Technology Fallah Mollamahmod, Mahdi (Author) ; Hajipour, Ehsan (Supervisor)
    Abstract
    One of the most critical equipments in power grids are power transformers, which are vulnerable to damage due to the possibility of faults in its various components. A very common category of such faults is turn-to-turn fault in its winding. This fault initiates by the aging of the winding insulation with a short circuit of several adjacent loops to each other and if it is not detected quickly by the transformer protection, it will spread rapidly and can lead to irreparable failure in the transformer. Traditionally, turn-to-turn fault should be detected by mechanical pressure relays, however, due to the poor performance of these relays in the rapid detection of this type of fault, in the...