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fault-detection
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An Accurate Algorithm for Power Transformer Turn to Turn Fault Detection to Enhance the Performance of Differential Relay
, Ph.D. Dissertation Sharif University of Technology ; Vakilian, Mehdi (Supervisor) ; Hajipour, Ehsan (Co-Supervisor)
Abstract
Power transformer is one of the most important equipment in the power system which plays a key role in the reliability and quality of power delivery. Among numerous failure modes of a typical power transformer, the turn-to-turn fault (TTF) is one of the most prominent reasons for its unplanned outage. A turn-to-turn fault quite often begins with the degradation of the winding insulation between two adjacent turns, then in a short time, this low-level fault can progress to a large number of turns and results in the transformer costly damages. Therefore, it is vital to detect TTF at an early stage and prevent its progression to a catastrophic disaster. The conventional percentage differential...
Improvement of Inverter-based AC Microgrids Protection Against Short Circuit
, Ph.D. Dissertation Sharif University of Technology ; Mokhtari, Hossein (Supervisor) ; Blaabjerg, Frede (Co-Supervisor)
Abstract
Inverter-based distributed generations (IBDGs) have gained special interest in the electricity supply chain due to the advancements in power electronics technology. Power electronic inverters provide high-efficiency energy conversion with full controllability over a wide operating range, and ancillary services such as reactive power support and active filtering. Considering the voltage and frequency control capability of power inverters, supplying inverter-based micro-grid (IBMG) loads is now pissible. Despite the significant opportunities associated with such sources, they introduce new challenges that should be addressed properly. Reliable and accurate protection against short circuit...
Fault-Tolerant Operation of Three-Phase Dual Active Bridge Converter Against Semiconductor Power Switches Fault
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
The three-phase Dual Active Bridge DC-DC converter, by virtue of its various advantages, has been widely used in numerous industrial and sensitive applications. However, this converter includes a large number of power switching devices, which are the most fragile components in Power Electronics, and therefore, can pose a threat to appropriateness of the converter for such applications. Accordingly, introducing a fault-tolerant scheme for this converter is necessary, in order to meet the demands of high reliability and service continuity in aforementioned applications. In this thesis, firstly, the converter is studied during normal operation as well as under switch open-circuit fault, and the...
Applying of Data Fusion Method for Improving the Protection System of the High Voltage DC Power Supply
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Short-circuit fault detection is mandatory in a high voltage DC power supply to prevent fatal damage. The majority of converters employ a single sensor to detect the short-circuit fault. This attribute increases the interference vulnerability of the fault detection system in the presence of noise. Therefore, miss detections and false alarms are possible to occur. Miss detections and false alarms are harmful catastrophes in most applications. A commonly used method to suppress the noise impacts is using a low-bandwidth low-pass filter. However, the use of the low-bandwidth low-pass filter reduces the speed of fault detection due to the filter delay. This paper proposes a fast fault detection...
Performance Improvement of Cascaded H-bridge Multilevel Inverter under Faulty Conditions
, Ph.D. Dissertation Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor) ; Oraee Mirzamani, Hashem (Supervisor) ; Rodriguez, Jose (Co-Advisor)
Abstract
Fault-tolerant ability is more subjected in Cascaded H-Bridge Multilevel Inverter due to its high-power medium-voltage applications and large number of semiconductors switches used in its structure. In this thesis, the goal is performance improvement of Cascaded H-bridge Multilevel Inverter under faulty conditions. Since to achieve the post-fault ability two steps; fault detection and post-fault control are required, both steps are considered in the improving process. In this dissertation, first operation of Cascaded H-Bridge Multilevel Inverter in normal and faulty condition is surveyed. Then, the conventional fault detection methods are mentioned and post-fault control methods are...
Leak Detection and Location in Oil Transmission Lines by Closed Form Solution and Linear Observer
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
In this paper, an approach is proposed to estimate the location of the leaks in oil pipelines. The pipeline possesses a system of Partial Differential Equations (PDE). First, a closed-form solution is applied to the pipeline equations and the leakage location is found solving the steady-state equations. To tackle the case where the pressure and flowrate do not reach constant values, the initial estimations are provided by the closed-form solution. Then, the pressures, flow rates, and leakage coefficient are estimated by solving the system of differential equations. This system is then discretized with respect to the location variable to yield the system state equations which, in turn, are...
Open-Circuit Fault Detection and Localization in Five-Level Active Neutral Point Clamped Converter
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
Five-Level Active-Neutral-Point -Clamped (5L-ANPC) converter is used for medium-voltage and high-power applications. In many of these applications, availability and robustness against fault are the most important issues. On the other hand, this converter is made of a large number of power semiconductor switches, diodes and capacitors which could increase the failure probability. Thus, fault detection of power circuit elements is necessary for fault tolerant operation of the converter. In this thesis, following an introduction to the topology and operation principles of Five-Level Active Neutral point clamped converter, a novel open-circuit fault detection and localization method is...
Fast Failure Detection in Modular Multilevel Converter Power Switches for Fault Tolerant Operation
, Ph.D. Dissertation Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
Multilevel converters are the best solution in medium and high voltage applications because of their better output votage quality, redundant structure, less power semiconductor losses and common-mode voltages. Modular multilevel converters (MMCs) have additional advantages such as higher degree of modularity, transformerless operation capability and using a single common DC-bus. All these useful features make MMC the first alternative for HVDC systems. Fault detection, defected cells insulation and post fault operation control are necessary to ensure MMC continouse service. A simple, fast and accurate fault detection method is proposed for MMC semiconductor power switches in this thesis....
Introducing a Supervisory Hardware Platform for Wireless Body Area Sensor Network with an Anomaly Detection Ability
, M.Sc. Thesis Sharif University of Technology ; Jahed, Mehran (Supervisor)
Abstract
Wireless Body Area Network (WBAN) is a set of various physiological sensors for remote monitoring and controlling of the patient’s health status. Detection of anomalies, containing faults and physiological stresses, and distinguishing between them can eliminate the need for constant presence of specialists and decrease the occurrence of False Alarm Rate (FAR).A supervisory hardware platform for WBAN architecture is introduced and implemented in this thesis. The proposed architecture contains three sensors for recording of biomedical signals, heart rate, SpO2 and body temperature simultaneously and transmitting them to central node wirelessly through Wi-Fi standard. This proposed architecture...
Design and Development of the Automated Irrigation Channel Pilot
, M.Sc. Thesis Sharif University of Technology ; 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
Development a Numerical Algorithm for Differential Relay for Transformer Protection
, M.Sc. Thesis Sharif University of Technology ; 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...
Nonlinear Geometric Approach to Fault Detection in Mechanical Systems
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
The demand for safety operating systems is growing with the new developments in technology. One of the important and critical issues in system monitoring is the capability of the system to detect probable faults and hazards. In model-based fault detection one specific diagnostic signal called residual should be generated for each fault that is only sensitive to a particular fault and independent of other faults and disturbances. In this thesis we try to investigate the nonlinear geometric approach in fault detection of a class of mechanical systems. After a brief introduction to geometric tool for nonlinear inputaffine systems and conditions in which output is decoupled from input, we...
Fault Diagnosis in Power Systems by Wide-area Measurement System
, Ph.D. Dissertation Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
A power transmission system includes transmission lines that are interconnected for economic and security reasons. Power systems are often prone to faults at the transmission level, since transmission lines are spread over vast geographical areas. Being the most serious events in power systems, blackouts are often initiated by a fault and a sequence of events afterward leads to partial or complete power outage. In this condition, fault diagnosis is the first step for power system restoration. In this research work, a new approach utilizing impedance-based fault location is introduced for fault diagnosis. By developing wide-area measurements in the context of smart grids, accurate...
Disturbance Diagnosis In Plant-wide Processes
,
M.Sc. Thesis
Sharif University of Technology
;
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
Fault Detection and Identification in Robotic Systems
, M.Sc. Thesis Sharif University of Technology ; 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...
Transmission Grid Fault Location by Optimal Placement of Phasor Measurement Units (PMU)
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
In this thesis, the problem of placing a minimum number of phasor measurement units (PMUs) in a transmission system is considered so that faults on all lines of the network can be diagnosed and located irrespective of their locations. For this purpose, a PMU placement algorithm is proposed to calculate the required data for impedance-based fault-location of any fault line in the network, achieving the full potential of the circuit laws throughout the system. Another algorithm is then proposed to compute the voltage and current values of the fault line for fault-location purposes. Moreover, as many networks are already equipped with PMUs, the proposed algorithm makes it possible to locate...
RT-Level Test Pattern Generation with Horner Expansion Model
, Ph.D. Dissertation Sharif University of Technology ; Tabandeh, Mahmoud (Supervisor) ; Navabi, Zainalabedin (Co-Advisor)
Abstract
Increasing in size and complexity of digital designs has made manufacturing process more complex and enforces more complexity in verification of designs. This makes it essential to address critical verification issues at the early stages of design cycle. Such a complicated designs needs to be tested for fabrication faults as well as functional faults. Several attempts have been made to raise the quality of testing methods with automatic test pattern generation (ATPG) and design for testability (DFT) methods in logic and lower levels. Although these techniques try to increase the testability of a circuit considerably, but there are always some overheads in area, power and performance....
Fault Tolerant AC/DC/AC Converters for Wind Energy Turbine with Doubly-Fed Induction Generator
, Ph.D. Dissertation Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor) ; Saadate, Shahrokh (Supervisor)
Abstract
AC/DC/AC converters are widely being used in a variety of power applications. Continuity of service of these systems, as well as their reliability and performance are now of the major concerns. Indeed, the failure of the converter can lead to the total or partial loss of the control of the phase currents and can cause serious system malfunction or even shutdown. Thus, uncompensated faults can quickly endanger the system. Therefore, to prevent the spread of the fault to the other system components and to ensure continuity of service, fault tolerant converter topologies associated with quick and effective fault detection and compensation methods must be implemented. In this thesis, the...
Data Mining Approach for Fault Diagnosis of Power Systemby Wide Area Measurement
, M.Sc. Thesis Sharif University of Technology ; 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...
A New Robust Fault Detection Approach to Nonlinear Dynamical Systems
, M.Sc. Thesis Sharif University of Technology ; 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...