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permanent-magnets
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Proposal of a Modular Structure and a Load Sharing Strategy among Back to Back Converters for Wind Turbines
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
The utilization of wind power has been increasing in recent years which lead to enhance the the usage of wind power capacity in the range of MegaWatt. However, due to the limitation ofswitching devices capacity, which exists in power electronic converters, improving the capacity of wind power generation is not accessible. Thus, a feasible solution for this problem is paralleling power electronics converters, which increases both the capacity of power generation and the reliability of wind turbine systems. Nevertheless, paralleling converters may cause a circulating-current which brings current discrepancy, current waveform distortion, power losses, increase in THD of currents, and reduction...
Speed Control of Permanent Magnet Synchronous Motor with Flexible Coupling Using Load Torque Observer
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
Elastic joints in 2-mass drive systems, because of their limited stiffness, can decrease the performance of the control system and lead to motor and load speed oscillation. Shaft torque ignoring can also stress both mechanical and electrical drive components. Because of low degree of freedom, conventional controllers, such as the PI controllers, cannot improve the performance of the system and keep the system stable at the same time. In this thesis, the dynamic response and stability of the 2-mass systems is improved using state controller. State estimation of 2-mass system is required for state space controller . In the thesis, different state observer is analyzed and compared with each...
Diffuser miniature pump with an extra ferrofluidic valve
, Article Microfluidics and Nanofluidics ; Volume 19, Issue 5 , November , 2015 , Pages 1235-1244 ; 16134982 (ISSN) ; Shafii, M. B ; Moosavi, A ; Sharif University of Technology
Springer Verlag
2015
Abstract
This paper presents the prototype design and fabrication of a magnetically actuated miniature pump that utilizes self-sealing capability of ferrofluid-covered permanent magnets in both pumping and valving mechanisms. The valving action is performed by employing one active valve along with two nozzle/diffuser elements. Two cylindrical permanent magnets are placed inside the flat-wall channels: One magnet acts as the active valve and the other one serves as a reciprocating piston actuating the working fluid. In order to seal the gaps between the channel walls and the permanent magnet of the valve/piston, ferrofluid is used to cover the surfaces of both magnets. The valve and the piston are...
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...
Stand alone performance of permanent magnet synchronous wind power generator with current source matrix converter
, Article Electric Power Components and Systems ; Volume 43, Issue 8-10 , 2015 , Pages 1018-1027 ; 15325008 (ISSN) ; Mokhtari, H ; Chang, L ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
A matrix converter is a voltage/current source AC/AC frequency converter. In grid-connected operation of a variable-speed permanent magnet synchronous wind power generator, the matrix converter is normally controlled as a voltage source converter. In this control method, the generator-side voltage is synthesized from the grid-side voltage source. However, in the stand-alone mode of operation, the grid-side stiff voltage source is not available, and the input filter of the matrix converter is unstable. In this article, a new control method is presented that controls a permanent magnet synchronous wind generator in a stand-alone mode with a matrix converter as a current source converter. The...
The select of a permanent magnet brushed DC motor with optimal controller for providing propellant of @home mobile robot
, Article 2010 IEEE International Conference on Mechatronics and Automation, ICMA 2010, 4 August 2010 through 7 August 2010 ; August , 2010 , Pages 1137-1141 ; 9781424451418 (ISBN) ; Khosroshahi, M ; Abbasi, M ; Ghaemi Osgouie, K ; Sharif University of Technology
2010
Abstract
This paper first will describe @Home Mobile Robot and DC motors. In continuous, is designed a Direct current (DC) motor for special task due to specific speed diagram for considered robot. This robot wants to work in intermittent operation condition. Finally is done a speed control on a selected permanent magnet brushed DC motor using of Linear-Quadratic-Regulator (LQR), Linear-Quadratic-Gaussian (LQG) and Fuzzy logic controllers
Equational reasoning on ad hoc networks
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 15 April 2009 through 17 April 2009, Kish Island ; Volume 5961 LNCS , 2010 , Pages 113-128 ; 03029743 (ISSN) ; 3642116221 (ISBN) ; Fokkink, W ; Movaghar, A ; Sharif University of Technology
2010
Abstract
We provide an equational theory for Restricted Broadcast Process Theory to reason about ad hoc networks. We exploit an extended algebra called Computed Network Theory to axiomatize restricted broadcast. It allows one to define an ad hoc network with respect to the underlying topologies. We give a sound and complete axiomatization for the recursion-free part of the term algebra CNT, modulo what we call rooted branching computed network bisimilarity
Automata based model checking for reo connectors
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 15 April 2009 through 17 April 2009 ; Volume 5961 LNCS , 2010 , Pages 260-275 ; 03029743 (ISSN) ; 3642116221 (ISBN) ; Izadi, M ; Sharif University of Technology
Abstract
Reo is a connector language for the exogenous composition and orchestration of components in a software system. An operational semantics of Reo connectors can be given in terms of Büchi automata over a suitable alphabet of records, capturing both synchronization and context dependency requirements. In this paper, we define an action based linear time temporal logic for expressing properties of Reo connectors. Formulas can be synthesized into Büchi automata representing Reo connectors, thus leading to an automata based model checking algorithm. By generalizing standard automata based model checking algorithms for linear time temporal logic, we give an efficient on-the-fly algorithm for the...
Performance verification of saturated IPM bearingless motors considering magnetic pull variation
, Article Proceedings - 2016 IEEE International Power Electronics and Motion Control Conference, PEMC 2016, 25 September 2016 through 28 September 2016 ; 2016 , Pages 643-649 ; 9781509017980 (ISBN) ; Nasiri Gheidari, Z ; Rahman, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Interior permanent magnet (IPM) bearingless motors are becoming a good choice for high-speed applications. In these motors, reducing the thickness of the PM leads to the increase of the radial forces which affects the demagnetizing fields. Various types of PM motors have so far been recommended for enhancement of the radial forces and torque. In the proposed IPM motor the d-axis flux-linkage and the q-axis torque component are raised due to the armature reaction and this saturates the stator teeth. In addition, the magnetic attraction force generated by displacement force depends on the armature reaction. The mathematical model of IPM bearingless motor based on the dq transformation,...
Electromagnetic design optimization of a modular linear flux-reversal motor
, Article Electric Power Components and Systems ; Volume 44, Issue 18 , 2016 , Pages 2112-2120 ; 15325008 (ISSN) ; Tootoonchian, F ; Sharif University of Technology
Taylor and Francis Inc
Abstract
Although modular linear flux-reversal permanent magnet motors are widely attractive for high reliability urban rail transit because of their advantages such as high power density, high reliability, low permanent magnet flux leakage problem, and improved fault-tolerant capability, they suffer from high thrust ripples. In this article the authors use a layer model for defining different optimization problems to improve thrust density, efficiency, and thrust ripples, independently and simultaneously. Design variables are chosen based on the sensitivity analysis of different objective functions relative to motor different geometrical parameters and some constraints are taken into account to...
Three-phase PFC rectifier with high efficiency and low cost for small PM synchronous wind generators
, Article 7th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2016, 16 February 2016 through 18 February 2016 ; 2016 , Pages 302-307 ; 9781509003754 (ISBN) ; Tahami, F ; Valipour, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Small Permanent Magnet Synchronous Generators (PMSG's) are widely used in low power wind turbines. In order to inject the electrical power, generated by PMSG, to the grid, a back-To-back AC/AC power electronic converter is required. In this paper, a novel low cost efficient AC/DC converter is proposed for rectifier stage to obtain the maximum power per ampere of PMSG by using Power Factor Correction method. The new structure is based on DCM SEPIC converter. Reducing the number of semi-conductor switches has decreased converter cost. Additionally, other advantages of this Converter are employing easy control method to obtain the maximum power per ampere and using Synchronous inductance of...
Cogging force mitigation techniques in a modular linear permanent magnet motor
, Article IET Electric Power Applications ; Volume 10, Issue 7 , 2016 , Pages 667-674 ; 17518660 (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institution of Engineering and Technology
Abstract
Modular linear doubly salient permanent magnet motors are well adapted to linear propulsion systems because of their distinct characteristics, such as high efficiency and power density, reduced maintenance and initial cost, low noise and permanent magnet (PM) leakage flux, and fault tolerance capability. However, such motors suffer from high cogging thrust. In this study, various techniques based on previously proposed methods for PM machines are applied on the studied motor and evaluated by using non-linear three-dimensional time-stepping finite element analysis; three novel, optimised techniques are then presented. The techniques presented are based on the minimisation of the variation in...
Approach for analytical modelling of axial-flux PM machines
, Article IET Electric Power Applications ; Volume 10, Issue 6 , 2016 , Pages 441-450 ; 17518660 (ISSN) ; Abedini Mohammadi, A ; Oraee, A ; Oraee, H ; Sharif University of Technology
Institution of Engineering and Technology
2016
Abstract
In the presented paper, an analytical model is developed for calculation of the air gap magnetic flux density in the axial-flux surface-mounted PM machines. The slotting effect is taken into account in the air gap magnetic flux distribution, accurately. The main novelty of this study is replacing the stator teeth by some surface currents at the border of the removed stator teeth. The uniqueness theorem is applied to find the surface currents. The two-dimensional (2D) field solution in the slotless machine is solved easily by separation of variables method. The multi-slice quasi-3D method is applied for taking 3D nature of field distribution into account. In addition, the back-EMF, armature...
Direct Speed Control of Permenant Magnet Synchronous Machine
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
Accurate and fast position controlling is an important issue in today’s industrial needs. Drives used for position control require fast dynamics on speed control. Cascade linear controllers have sluggish response due to bandwidth limitations on speed and current loop. These structures limit the dynamics above all in high power applications where the switching frequency is low. In this thesis, deadbeat direct speed control is proposed, which overcomes limitations by cascade loops resulting in high-speed control dynamics. This approach uses a model of the plant to generate the control signals. According to measured speed and currents, the controller specifies the best voltage vector in order...
An Analytical Model for No-Load, Slotted, Axial Flux Surface-Mounted PM Machines: Air Gap Flux Density and Cogging Torque
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor) ; Taghipour Boroujeni, Samad (Co-Advisor)
Abstract
In the presented dissertation an analytical model is developed for the air gap flux density and the cogging torque in the axial flux surface-mounted PM machines. The slotting effect is taken into account in the magnetic flux distribution.The model is derived from solving the 2D Poisson' equation in the slotted air gap. To simplify the solution process, the concept of the uniqueness theorem is used to replace the slotted air gap by a slotless one and some surface current distribution. In addition, the separation of variables method is applied to the analytical solution of the Poisson equation. However, the proposed 2D analytical model is developed for the quasi 3D model by the well-known...
Sensor fault-tolerant scheme for IPM synchronous motor drives via nonlinear observer
, Article AUPEC'09 - 19th Australasian Universities Power Engineering Conference: Sustainable Energy Technologies and Systems, 27 September 2009 through 30 September 2009, Adelaide ; 2009 ; 9780863967184 (ISBN) ; Farshidnia, A ; Keivanian, R ; Sharif University of Technology
Abstract
This paper describes a control scheme that allows an IPMS motor drive system to operate in the event of current and speed sensor faults. This task can be achieved by two control strategies: a nominal performance controller and a fault detection part. The nominal controller combines field oriented control and addresses fault tolerance scheme. Fault-tolerant strategy will operate in parallel with the system until a fault is detected. This approach is based on the adaptive backstepping observer. Stator resistance as possible source of system uncertainty is taken into account under different operating conditions. Sensors failure are detected and developed observer is used to estimate currents...
A new loss minimization approach with flux and torque ripples reduction of direct torque controlled permanent magnet synchronous motors
, Article 2009 13th European Conference on Power Electronics and Applications, EPE '09, 8 September 2009 through 10 September 2009, Barcelona ; 2009 ; 9781424444328 (ISBN) ; Vaez Zadeh, S ; Tahami, F ; Sharif University of Technology
Abstract
The main purpose of this paper is to minimize the loss while reducing the flux and torque ripples in permanent magnet synchronous motors (PMSMs) under direct torque control (DTC). Offline method is used to minimize the loss and obtain the optimal flux. To reduce the amount of computation, the optimal flux table is produced according to the conditions in which the machine works. To reduce the flux and torque ripples and to control the switching frequency, SVM-DTC method is applied. Simulation results depict a noticeable increase in efficiency of the motor and a reduction in flux and torque ripples
Performance Analysis, Optimization and Prototyping of Doubly Salient PM Vernier Generators
, M.Sc. Thesis Sharif University of Technology ; Oraee, Hashem (Supervisor) ; Nasiri-Gheidari, Zahra (Supervisor)
Abstract
In this thesis, no-load and full-load performance of Permanent Magnet Vernier Generators (PMVGs) is investigated in fully-aligned condition and under different types of mechanical faults. The studied mechanical faults are Static Eccentricity (SE), Dynamic Eccentricity (DE), Inclined Rotor (IR), and Run-out (RO). Furthermore, an analytical model is also developed to calculate the permeance of the air-gap and the induced voltages in the health machine and under studied mechanical faults. Then, 2-D and 3-D non-linear, time stepping finite element method is utilized for performance evaluation of the generator in no-load and full-load (with resistive, inductive and capacitive loads). In continue,...
Performance analysis of concentrated wound-rotor resolver for its applications in high pole number permanent magnet motors
, Article IEEE Sensors Journal ; Volume 17, Issue 23 , 2017 , Pages 7877-7885 ; 1530437X (ISSN) ; Nasiri Gheidari, Z ; Tootoonchian, F ; Oraee, H ; Sharif University of Technology
Abstract
High pole number permanent magnet (PM) motors, due to their high torque density, have been receiving considerable attentions in recent years. To achieve an accurate position control in PM machines, resolvers are suggested for industrial applications. Mechanical and electromagnetic considerations in the case of high pole number resolvers lead the machine designers to choose small cores with low slot numbers. This paper proposes two different on-tooth winding configurations to achieve high pole number without increasing the slot numbers, while the accuracy of the detected position is intended to be the maximum value. Variable turn on tooth winding (VTTW) is compared with fractional slot...
Numerical simulation of magnetic convection ferrofluid flow in a permanent magnet–inserted cavity
, Article Journal of Magnetism and Magnetic Materials ; Volume 442 , 2017 , Pages 270-278 ; 03048853 (ISSN) ; Behshad Shafii, M ; Sharif University of Technology
Abstract
The magnetic convection heat transfer in an obstructed two-dimensional square cavity is investigated numerically. The walls of the cavity are heated with different constant temperatures at two sides, and isolated at two other sides. The cavity is filled with a high Prandtl number ferrofluid. The convective force is induced by a magnetic field gradient of a thermally insulated square permanent magnet located at the center of the cavity. The results are presented in the forms of streamlines, isotherms, and Nusselt number for various values of magnetic Rayleigh numbers and permanent magnet size. Two major circulations are generated in the cavity, clockwise flow in the upper half and...