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Direct Torque Control of Permanent Magnet Synchronous Machine Using Nonlinear Flux Observer
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
Direct Torque Control (DTC) is one of the vector methods to control Permanent Magnet Synchronous Machines (PMSM). In order to achieve an appropriate control in vector control methods, an accurate estimation of flux is indispensable. Flux estimation should be fulfilled in a wide speed range without considerable dependence on motor parameters. Prevalent flux estimation methods are based on integration of stator voltage which is not feasible in low speed, or performed based on assumption of decoupled equations on d and q axis which is not precise for applications with fast dynamic. Different flux estimation methods are investigated in this thesis with the aim of improving the flux estimation in...
Optimum Design of Low Speed Superconducting Synchronous Machine
, Ph.D. Dissertation Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor) ; Fardmanesh, Mehdi (Supervisor)
Abstract
Using superconducting synchronous machine leads to many advantages such as increasing overall efficiency, decreasing mass and valume of peropulsion system, eliminating some restrictions in hydrodynamic design , etc. The goal of this thesis is design of 200 kW, with 250 rpm superconducting synchronous motor for small ship propulsion drive application. The low speed motor can be directly coupled to the propeller whitch eliminates bulky and inefficient gearbox. After comparison of different structures of superconducting synchronous machines, finally rotating superconducting field with stationary copper armature winding is selected as the most approporiate structure for our application.
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Dynamics of Two Coupled Neurons of Different Types of Excitability
, Ph.D. Dissertation Sharif University of Technology ; Razvan, Mohammad Reza (Supervisor)
Abstract
Excitability is one of the most important characteristics of a neuron. In 1948, Hodgkin identified three different types of excitability of neurons. Excitability an all of its types can be observed in Hodgkin-Huxley model of neuronal dynamics (H-H model) as a four-dimensional system of differential equations and in at least two dimensional reductions of H-H type models. By applying the theory of dynamical systems (e.g. bifurcation theory), one can give a mathematical definition of excitability.Excitability of the neuron is equivalent to that the neuronal model is near a bifurcation through which the state of the system approaches to a stable limit cycle. In this thesis, a two-dimensional...
Synchronizaion of Chaotic Systems by Using Fractional Calculus
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor)
Abstract
Synchronization means to control the response system to follow the drive system. It first began in 1990 in a paper by Pecora and after that it is used in many applications like secure communication. Another application for synchronization which is introduced here is identification of chaotic systems. According to the research done, this application hasn’t been in the literature as it is known to us. Synchronization papers usually devide into two parts. In one of them the parameters of the systems are unknown, so adaptive laws are used to estimate the parameters. In the other part, the parameters are taken known. It is not mentioned in the first group that the estimation would converge to the...
Study and Improvement of Stability of Generator-based Distributed Generation units Inpresence of Large Nonlinear Loads
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Hyderogels are hydrophilic polymers with three dimensional network structure, due to their high water absoption, their application to life and industry is increasing from day to day, such as tissue engineering, actuators and sensors, drug delivery and therapeutic treatment. In this project, it has been attempted to produce polyacrylamide/alginate double network hydrogels with the use of graphene oxide nanosheets to indicate that it is possible to combine toughness and self-healing in a hydrogel with the opposite nature of each other. To evaluate mechanical properties, uniaxial tensile test and loading-unloading test were used. The results indicate that increase the weight ratio of acrylamide...
Comprehensive Optimization and Design a Telecom Charger with Wide Band Gap Devices
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor) ; Nasiri-Gheidarik, Zahra (Co-Supervisor)
Abstract
Nowadays high efficiency and power density are desired for designing a power electronic converter. Technology advances in power semiconductor devices, makes it possible to design converters for operation in higher frequencies to reduce size of the converters. As the frequency is increased, switching losses and temperature is also increased, so designing a converter for high frequency operation needs some tradeoffs. LLC resonant converter as a promising solution for battery chargers has ability to adjust its output voltage during Constant Current and Constant Voltage modes. However, its operation mode would change based on switching frequency change. Therefore, for efficiency-oriented...
Design, Manufacturing and Testing a Micro Hydro Turbine Governor Using Commercial Controller
, M.Sc. Thesis Sharif University of Technology ; Durali, Mohammad (Supervisor)
Abstract
Lots of micro hydropower potentials are spread all around Iran country. They have the capability to produce electricity for workhouses, residential areas, agricultural and animal husbandries and recreational tourism centers. Hence, Sharif University of Technology and Iran Water and Power Resources Development Corporation decided to design and produce three types of hydro micro turbines to cover all range of micro hydropower potentials available in Iran. These three types of micro turbines are Pelton, Banki and Axial and they are designed in order to cover high, middle and low heads in sequence. Frequency control of micro hydropower plants is so vital due to plant off-grid. The most prevalent...
Midterm Scheduling and Assignment of Inbound and Outbound Doors in a Cross Dock Network
, M.Sc. Thesis Sharif University of Technology ; Shavandi, Hassan (Supervisor)
Abstract
Cross docking is a novel docking method which importance in supply chain management has been underlined in recent decades. Two main operations of regular docking centers, including storage and picking up are eliminated in cross docking facilities in order to decrease inventory holding costs, shorten lead times and at the same time increase service level. Although inbound and outbound flow at each cross dock are determined by the flow of shipments through the network, overwhelming majority of papers in this field have addressed each of local and network-wide cross docking problems mutually in isolation. That being so, the problem dealt with in this research, is to how determining the flow of...
Truck and Motorcycle Routing Problem with Mobile Delivery Location
, M.Sc. Thesis Sharif University of Technology ; Akbari Jokar, Mohammad Reza (Supervisor)
Abstract
The emergence and development of E-commerce prompted many companies to reduce their cost by seeking new solutions that improve customer satisfaction level and product distribution. In this research, the coordination of a truck and a motorcycle is considered to utilize both vehicles' benefits. The mobile location of customers is another assumption in this research. Therefore, it is possible for customers to suggest different delivery times and locations. Based on the customer situation, there are three location modes which specify the accessibility. In this study, a mixed-integer linear programming model is presented to minimize service completion time. In addition, two metaheuristic...
Optimum Highway Alignment Using Parallel Processing
, M.Sc. Thesis Sharif University of Technology ; Shafahi, Yusof (Supervisor)
Abstract
Optimum highway alignment problem is among the most substantial but large and complicated topics in transportation area. Infinite number of feasible solutions, numerous local optima and the constrained feature of the problem, associated with complex and mainly non-linear constrains, has put an extra effort into the problem-solving process. Moreover, the problem has a sensitive objective function to input variables. Due to the nature of the problem, conventional methods fail to find any exact solution, and so, using heuristic methods during the solving procedure is inevitable. Large-scale, complexity and sensitivity of the problem leads to a solution which is time-consuming and...
Enhancement in Frequency Control of Microgrids by Application of Modified Controller in Virtual Synchronous Generator
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
global warming and air pollution due to the excessive consumption of fossil fuels have led to the proliferation of renewable energy sources (RESs). RESs are connected to the grid through power electronic converters and therefore, provide insignificant inertia and damping property for the system. As a result, the system overall inertia and damping is decreased and therefore, the system stability is jeopardized. This thesis presents a comprehensive small signal model for a virtual synchronous generator (VSG) integrated into a microgrid. In the developed state space, active and reactive power control loops of the VSG as well as resistances and reactances of the lines are considered. Based on...
Improvement of Matrix Converter Performance in Application of PMSG -Driven Wind Turbine
,
Ph.D. Dissertation
Sharif University of Technology
;
Mokhtari, Hossein
(Supervisor)
Abstract
The use of wind energy and wind generators as an inexpensive type of renewable energy sources is increasing. Wind farms and distributed wind generators connected to the power transmission and distribution systems and microgrids, and wind generators in standalone mode of operation affect the stability and power quality of the grid. In this thesis, the performance of a matrix converter in grid connection of variable speed PMSG–driven wind turbine is improved. In this way, by transferring the matrix converter modulation matrix into the synchronous reference frame and decomposing it into the singular values, a new general method is proposed for analysis, modelling and modulation of a matrix...
The Effect of the Threshold Parameter on the Statistics of Neuronal Avalanches in the Rotational Model
, M.Sc. Thesis Sharif University of Technology ; Moghimi Araghi, Saman (Supervisor)
Abstract
There are experiments that conclude the brain is in the critical or near the critical region. These researches extract avalanches from the neuronal activity and then show that avalanche size (or duration) distribution obeys the power-law distribution. Defining avalanches from neuronal activity has some challenges. In some cases deciding the threshold (which determines the beginning and end of an avalanche) seems arbitrary or fine-tuned. In this thesis, we will show how different thresholds for defining avalanche and different time resolutions for defining neuronal activity can change avalanche size (or duration) distribution
Role of Synchronous Sub-network in the Propagation of Synchronization to the Neuronal Population
, M.Sc. Thesis Sharif University of Technology ; Moghimi Araghi, Saman (Supervisor)
Abstract
Epilepsy is one of the most common non-communicable neurological disorders, characterized by recurrent seizure symptoms. Although much progress has been made in the diagnosis, control, and treatment of epilepsy in recent years, the exact mechanism of seizures, the specific method for early diagnosis of epilepsy and related syndromes, and definitive treatment for all patients are not yet known. In a type of seizure known as focal seizure, the electrical activity of neurons at the epilepsy focus synchronizes abnormally, and this synchronization can propagate to other regions of the brain in a process called secondary generalization, which finding a method for its prevention is our essential goal...
The Information Theory Approach to Communication over Deletion Channel with Hidden Markov Codebook
, M.Sc. Thesis Sharif University of Technology ; Aminzadeh Gohari, Amin (Supervisor)
Abstract
One of the main challenges in data transmission is synchronization error. In practice there are solutions to this issue, but this incurs a cost that can not be neglected. Synchronization error consists of deletion, insertion and substitution. Investigation of such errors in a communication channel has been of a great concern in information theory. Furthermore, in many applications such as biology and data storage on disks, we observe synchronization errors. Deletion channel is defined as a channel in which input symbols are deleted with a probability d independently of each other, such that the order of symbols remains unchanged. In spite of attempts to find a closed form for the capacity of...
Analysis and Evaluation of Security Vulnerabilities of Precision time Protocol (PTP) and Securing IEEE61850 based Digital Substations
, Ph.D. Dissertation Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor)
Abstract
Nowadays, power systems and substations are the most important components of the vital infrastructure of a country, which handle the production, transmission and distribution of the electrical energy. Automation systems increase the efficiency of the power industry while making remote control possible, but the use of computer-based control systems is a potential field for cyberattacks which may cause equipment destruction and electricity network destabilization. One of the main requirements for the utilization of digital substations is the synchronization between different equipment used in it. Several algorithms and protocols have been proposed so far for time synchronization in distributed...
Timetable Optimization and Synchronization in an Urban Subway Network with Stop-Skip Strategy
, M.Sc. Thesis Sharif University of Technology ; Shafahi, Yousef (Supervisor)
Abstract
Stop-skipping and timetable synchronization in a transit network for subway operation are two effective strategies to reduce passengers' total travel time.Most of the current research on the topic does not consider stop-skipping strategy and timetable synchronization simultaneously. This paper proposes a mixed-integer programming model based on passenger smart-card data concerning the trains' capacity to minimize passengers' total waiting time and in-vehicle time and maximize the number of passengers who successfully reach their destination. Since increasing the number of trains, stations, or the study horizon, exponentially increase the size of the problem, seeking practical methods to...
Stimulus Signal Improvement in Order to Alleviate the Symptoms of Parkinson's Disease in Rat
, M.Sc. Thesis Sharif University of Technology ; Vosughi Vahdat, Bijan (Supervisor)
Abstract
Parkinson's disease is a degenerative disorder of the central nervous system. The motor symptoms of Parkinson's disease result from the death of dopamine-generating cells in the substantia nigra. The cause of this cell death is unknown. Early in the course of the disease, the most obvious symptoms are movement-related. Some of the symptoms are: shaking, rigidity, slowness of movement and difficulty with walking and gait. Modern treatments are effective at managing the early motor symptoms of the disease, mainly through the use of levodopa and dopamine agonists. As the disease progresses these drugs eventually become ineffective and produce a complication called dyskinesia, marked by...
Sensor-Less Control of Permanent Magnet Synchronous Motor Using High Frequency Signal Injection
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
In this thesis one of the sensorless methods which exploits the existing anisotropies of the rotor is utilized to estimate rotor position. In order to implement this method, first a high frequency voltage is injected in a specific, time-varying direction and then the corresponding current response would be observed in order to estimate the rotor saliency position. The estimation of rotor position would be more precise as the magnetic anisotropy due to rotor saliency increases and as a result the effect of noise and different disturbances in estimation of rotor position would be decresed. The effect of stator resistence is one of these disturbances which is usually neglected as a result of...
Design and Optimization of a Flux Reversal Permanent Magnet Generator for Power Density Improvement in Direct Drive wind Turbine Application
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor) ; Nasiri Gheidari, Zahra (Co-Supervisor)
Abstract
Nowadays, due to gearbox drawbacks, the direct-drive wind turbines have received much more attention. Permanent magnet synchronous machines are commonly used for this purpose. The flux reversal machine with a magnetic gearbox and high power density could be an appropriate alternative. Due to placement of permanent magnets on the stator, the machine has a simple and robust structure and provides more reliability. There is limited study on optimization of the flux reversal machine and the existing papers are not complete and many parameters like PM dimension, working temperature, and winding reactance are not considered in the optimization process.Considering the flux reversal machine...