Electrical Engineering Department PhD Thesis Defense Session Coordinated Control Design of Distributed Generators Interface Converters and Power Quality Conditioners in MicrogridsAbstract: In recent years, distributed generators have proliferated in electrical systems. In this regard, the concept of microgrid has been newly proposed. A microgrid is a small local grid which comprises distributed resources and loads and is able to operate in grid-connected and islanded modes. Distributed generators are often interfaced to the electrical system by power-electronic converters. The main role of the interface converter is to control power injection. In the present thesis, the control of distributed generators interface converters in order to improve microgrid power quality is addressed. This way, the need for dedicated power quality conditioners such as active power filters will be alleviated. The control of interface converters is coordinated in a way that the distributed generators cooperate in compensating power quality problems and supporting loads demands in proportion with their rated powers. The proposed control structures can be classified as hierarchical (centralized) and local (decentralized) control schemes. In the hierarchical scheme, the power quality enhancement is managed by a central controller which sends proper control signals to distributed generators while in the other scheme local controllers are in charge of compensation control. Various methods are proposed to provide virtual impedance by distributed generators aiming to improve the sharing of load current components and to enhance microgrid power quality. Furthermore, the coordinated control of distributed generators converters and active filters is presented in order to provide more options for power quality compensation. The proposed approaches are applicable in both grid-connected and islanded operation modes of microgrid. Control systems design procedures are discussed in detail and simulations (using Matlab/Simulink software package) and experiments are performed in different cases to validate the proposed control approaches. Ph.D. Candidate : Mehdi Savaghebi FiroozabadiSupervisor : Dr. Alireza JalilianAdvisor: Dr. Josep M. Guerrero

Electrical Engineering Department PhD Thesis Defense Session A Novel Approach For Designing Microstrip Bandpass Filters By The Aid of Fuzzy Inferences Method With Some PrototypesAbstract: In the final step of any filter design process, the desired center frequency, coupling factor and external quality factor (Qext) are used to determine the physical parameters of the filter. Although in the most cases the physical dimensions of a single resonator for a given center frequency are determined using exact analytical or simple approximate equations, usually such simple equations cannot be found to easily relate the required coupling factor and Qext to the physical parameters of the filter. Analytical calculation of coupling factor and Qext versus dimensions are usually complicated due to the geometrical complexities or in some cases such as microstrip resonators due to the lack of exact solution for the field distribution. Therefore coupling factor and Qext of various kinds of resonators, especially microstrip resonators, are related to the physical parameters of the structure by the use of time consuming full wave simulations. In this dissertation a surprisingly fast and completely general approach based on a soft computing pattern-based processing technique, called active learning method (ALM) and spatial membership functions is proposed to overcome the time consuming process of coupling factor and Qext determination. ALM is an adaptive recursive fuzzy learning algorithm based on brain functionality and specifications which models a complex multi-input single-output (MISO) function or system as a fuzzy combination of some single-input single-output (SISO) one. In the modeling process the multi-dimensional functions of coupling factor and Qext are broken down into their simpler aspects, their behaviors are extracted and then final model will be constructed by combining these simpler aspects.Ph.D. Candidate : Payman RezaeeSupervisor : Dr. Majid TayaraniExamining Committee : Prof. Hojjat Kashani, Dr. Komjani, Dr. Khalaj Amirhoseini, Prof. Kamyab, Dr. BrishamianDate: 2012/3/6 MondayLocation: Room 302 Electrical Engineering Faculty

Electrical Engineering Department PhD Thesis Defense Session Improvement of TLM Algorithm Frequency Response in Microstrip Discontinuities and Metamaterials Abstract: The design of high performance electronic components and systems such as waveguide structures, digital systems interfaces and connections, RF circuits and systems requires careful attention to physical modeling. In this way, the intrinsic physical inherent limitations of implementation processes can be accounted for, and adverse effects such as substrate coupling, electromagnetic interference (EMI) and metallic edges effects can be minimized. A high degree of physical fidelity of the models is necessary and can only be achieved by detailed analysis employing electromagnetic field solvers. The time domain Transmission Line Matrix (TLM) method has proven to be a powerful tool for solving electromagnetic field problems and has been successfully applied to the analysis of various complicated planar and general three-dimensional structures.The design of complex systems operating at high frequencies requires that the design and analysis tools can handle circuit and field analysis at the same time since the design system may include a combination of lumped circuits, transmission line components such as couplers, power dividers, interconnections, and waveguide components that may contain field singularities due to metallic sharp edges or corners. The field analysis of such a hybrid system is a difficult task for a space and time discrete numerical method like FDTD or TLM method. Existence of field singularities, complex media and materials such as dispersive materials, metamaterials and ferrite is one of the main problems in using such methods to simulate the desired structures. What is intended in this project is to efficiently eliminate the effects of singularities while increasing the accuracy of results without any additional computational cost. In addition, the ability to simulate dispersive materials and complex structures such as metamaterials using TLM algorithm is another main objectives of this project.Ph.D. Candidate : Mahdi RajabiSupervisor : Dr. Nader KomjaniExamining Committee : Prof. Hojjat Kashani, Prof. Orazi, Dr. Khalaj Amirhoseini, Prof. Rashed Mohasel, Prof. ForooraghiDate: 2012/3/14 WednesdayLocation: Ebnesina Conference Hall, Electrical Engineering Faculty

Electrical Engineering Department PhD Thesis Defense Session Multiple Antenna Multiple Relay Cooperative Systems in Wireless Fading ChannelsAbstract: In cooperative networks a nodes (source) can exploit other nodes (relay) antennas to obtain spatial diversity. In such networks the source broadcast its symbols and the relays receive the transmitted symbols, and after applying their designed algorithm, forward them to the destination node.In this thesis, a Multi-Antenna Multiple Relay Network (MAMR) in which the source and the destination have the same number of antennas (M) and each transmit antenna is virtually paired to a different destination antenna is investigated. Amplify and forward (AF) strategy is used in the relays where the relays multiply the received vector by a matrix, dubbed the relay matrix, and forward the resulting vector to the destination. In this thesis, the aim is to find the optimized relay matrix.The main contribution of this thesis is presented in three parts: In the first part, by applying ZF algorithm in the reception and transmission for each relay, the MAMR network is transformed to M Single-Antenna Multiple Relay Networks (SAMR). In consequence, the network beamforming proposed for SAMR network can be deployed.In the second part, the optimal relay matrix in MAMR network is obtained for two assumptions of complete and partial channel state information (CSI). It is assumed that a parameter (η) that control signal to noise ratio at destination is known. In the optimization problem, the Mean Square Error (MSE) is minimized as the object function subject to individual power constraint at each relay. The duality is used to solve the problem and the parametric relay matrices are obtained where the parameters are Lagrange multipliers. Then these parameters are computed numerically using Active Set method. To obtain η a method based on its statistical properties is proposed. Then we show that problem with partial CSI is a generalization of the complete CSI case and by changing some variables the partial CSI problem is converted to the completed CSI problem. Thus the same approach of the complete CSI can be use to obtain the relay matrices in partial CSI case.At the end, the parametric relations are achieved for special cases: two relays network and a network with high SNR. The obtained matrices are similar to precoding matrix in MIMO systems.Student: Yasser Attar IziDirecting Proffessor: Dr. Abolfazl FalahatiDr. Paeez Azmi, Dr. Soroush Akhlaghi, Dr. Vahid Tabataba Vakili, Dr. Mohammad Kahaei, Dr. Bahman Abolhasani Date: 2012/7/3,Wednesday  Time: 16:30Place: Ibn Sina Amphitheater  Electrical Engineering Department

Electrical Engineering Department PhD Thesis Defense Session Simulation and Implementation of Sensorless PTC method for Induction MotorAbstract: The predictive torque control (PTC) method is being implemented by means of speed sensor in most cases. Also, in model predictive control, adjusting the weighting factor is an important challenge. Therefore, the PTC method has not succeeded to pave its way to the industrial applications.The contributions of this dissertation are categorized to two main parts. In the first part, two novel methods for weighting factor calculation are developed. In the first method, weighting factor of the cost function is calculated via an optimization method in order to minimize the torque ripple. In the second method, a look-up table base method for two-step prediction method is developed. The second part of the dissertation is dedicated to the proposed sensorless predictive torque control methods. Finite control set model predictive control (FCS-MPC) method and dead-beat method are combined with full order and voltage model observers. In order to reduce the effect of sensorless estimation on sensorless prediction, a robust prediction model is proposed for FCS-MPC and an inherently sensorless prediction model is proposed for dead-beat control. For precise estimation of the states, robust full order observer and robust reduced order observer are developed. The robustness of the prediction model and observers is achieved by H-infinity analysis.In order validate the proposed methods, simulation and experimental results are presented and analyzed. Low speed performance, robustness against the variation of the stator and rotor resistances and robustness against current measurement offset are examined to select the most useful method.Ph.D. candidate: Seyed Alireza DavariSupervisor: Dr. Arab Khaburi Examining committee: Dr. Mili Monfared, Dr. Vaez Zadeh, Dr. Shoulaei, Dr. Vahedi, Dr. JalilianDate: 2012/102/26 SundayLocation: Room 304 Electrical Engineering Faculty

Electrical Engineering Department PhD Thesis Defense Session Modeling  And Allocation of RHFC as a New Member of FACTS Devices for Static StudyAbstract: Steady-state and dynamic power-flow control, particularly under heavily loaded system conditions, is an indispensable operational requirement for an interconnected power system. One of the most conventional FACTS devices used to control and transfer the power through certain paths is Phase Shifting Transformer (PST) but it is only more effective to control steady-state power control because of its large time constant. Rotary Hybrid Flow Controller (RHFC) as a new member of  Flexible AC Transmission System (FACTS) controllers  is formed of combination of RPST and other power flow controllers for providing dynamic power flow control. This thesis describes the steady state single phase equivalent circuit and P-Q operational characteristics of RHFC based on power injection model. However OPF makes an objective function to be optimal in the network but it causes other objectives diverge from their optimal value. Therefore, it has been made most of multiobjective optimal power flow to fix all of function in admitting limits from their optimal value. The optimal location and setting of RHFC incorporated in Optimal Power Flow (OPF) problem are found to optimize the total fuel cost, power losses, system loadability in the IEEE 14-, 30- and 118-bus test systems. Furthermore, the results obtained by these devices have been compared to that of PST, HFC  and UPFC. The optimization problem is solved in MATLAB and GAMS softwares using Non Linear Programming (NLP) and Mixed Integer Non Linear Programming (MINLP) as solution procedures. Simulation results show that RHFC has  desirable operation in technical and economical point of views. Student: Roshanak  RezaeipourSupervisor: Mr. Ahad KazemiCommittee Judges: Mr. Jalali, Mr. Kalantar, Mr. Arab Khabouri, Mr. Golkar, Mr. ShayeghiDay: Jan. 31, 13:00 Afternoon Class: 305

Electrical Engineering Department PhD Thesis Defense Session Robust Combination Methods for Biometric SystemsAbstract: Designing multi modal biometric systems proposes more precise and confident technique than single systems, with one biometric modality and one matcher, for authentication. Because absolute security is impossible, investigation of various invasions to these systems and analyzing vulnerability of systems against these attacks cause proposing suitable methods for designing secure authentication systems and increment their robustness. This thesis introduces the possibility and probability of spoof attacks to each modality of biometric matchers and investigates the vulnerability of combined biometric systems against spoofing of their matchers' modalities. In this research for case study face and fingerprint traits are fused in score level for generation of bimodal biometric systems. For studying the vulnerability of systems, we have simulated spoofed scores of each matcher, up on proposed parameters by a novel method, then imposed invasion to authentication systems by these simulated scores, and at last calculated the vulnerability of them by an applicable method. Vulnerability of biometric systems is evaluated in individual and bimodal forms by the most common fusion rules, included fixed combination rules contained analytic and fuzzy rules, and linear and nonlinear trainable rules against various possibilities and probabilities of spoofing and experimental results have been analyzed and compared. Comparison of quality and quantity outcomes of various fusion rules shows the robustness and vulnerability of each of them. In this thesis, spoofed scores database has been constructed from real standard scores database with various possibilities and probabilities of spoofing. Following the goal of research and for improve the robustness of biometric systems against spoofing, rules and guidelines include: finding suitable biometric modality and its matcher, robust combination rule and its robustness conditions are proposed as the contribution of these research.Novel applied experimental researches and extraction method of their results show the importance of consideration to and more investigation the robustness of biometric systems and can help to development of security and creation the appropriate robustness in biometric systems by investigation their vulnerabilities with fusion rules and biometric traits.Mahdi HaririSupervisor: Dr Shahriar Baradaran ShokouhiAdvisor :Dr Sattar MirzakuchakiThe Jury:Dr Ehsanollah Kabir, Dr Nasrollah Moghaddam, Dr Karim Mohammadi, Dr Ahmad Ayatollahi, Dr Golam ali Rezaei RadViva Date:   Sunday 8 Jan 2012Place: Electrical Engineering faculty, Seminar Room (Class 303)

Electrical Engineering Department PhD Thesis Defense Session Design and Simulation of an intelligent Algorithm for Defects Detection in Ultrasound Images Abstract: In non-destructive testing, detection and clustering of defects is an important issue. One of the exploited methods to determine the defects is the use of c-scan images obtained from ultrasound test. The goal of the thesis is detection and clustering of defetcts in ultrasound images. Since the quality of the obtained image is not suitable for processing, it is necessary to enhance the quality of images before applying clustering method. The proposed denoising method in preprocessing step is based on the denoising the wavelet coefficients of the image by the use of independent component analysis and a spatial filter. The filter is used to determine the homogenous areas from the areas containing image details. The method has the capability to reduce different kind of noises including Gaussian, speckle and the noise with weak Gaussian distribution. The proposed clustering algorithm is based on the rosette pattern. For this purpose, by the use of the rosette pattern, the image is sampled and according to the rosette pattern characteristics, the samples are mapped to the two dimensional linear space. In this stage, based on the neighborhood property of the samples, the clustering is performed. Finally, the clustered samples are remapped to the main space. Unlike the conventional clustering methods such as k-means and FCM algorithms requiring the number of clusters as one of the initializing parameters, in the proposed method, there is no need to initialize any parameter. Based on different data sets, the results show that the algorithm improves the capability of clustering, run time and determining the optimal number of clusters about 92%, 99% and 71% compared to k-means and FCM algorithms, rspectively. Moreover, in dealing with high resolution data sets, the efficiency of the algorithm in clusters detection and run time improvement increases considerably.Phd Student : Amirkeyvan MomtazSupervisor: Dr. Ali SadrJudges: Dr. Mahloojifar, Dr. Setaredan, Dr. Ayatollahi, Dr. Mirzakochaki and Dr. AbrishamifarDay: Wednesday, Date: 2012/01/11 Time: 17Class: 303

Electrical Engineering Department PhD Thesis Defense Session Dynamic Analysis, Design and Implementation of Induction Motor Control Based on the Singular Perturbation Theory with Consideration Iron Losses and Core SaturationAbstract: Control of Induction motor due to it’s the nonlinear property is one of the most popular research topics recently. Vector control based algorithms which are used for proper functioning need to estimate the rotor speed and magnetic flux. In many applications, flux and speed must be estimated without using sensors. Thus, in these cases, it is necessary to obtain speed and flux by measuring voltage and current. In this thesis, a nonlinear observer for estimating motor parameters based on Lyapunov function is presented. Using the Lyapunov theory, inputs regulating system and control system are earned which improve increases system performance. Moreover a novel control speed sensorless indirect field-oriented control for the full-order model of the induction motor is presented. It provides local exponential tracking of smooth speed and flux amplitude reference signals together with local exponential field orientation, on the basis of stator current measurements only and under assumption of unknown constant load torque.The absence of the flux model in the proposed algorithm allows for simple and effective time-scale separation between the speed–flux tracking error dynamics (slow subsystem) and the current error dynamics (fast subsystem). This property is exploited to obtain a high performance sensorless controller, with features similar to those of standard field-oriented induction motor drives. The theoretical analysis based on the singular perturbation method enlightens that a persistency of excitation condition is necessary for the asymptotic stability.Extensive simulation and experimental tests confirm the effectiveness of the proposed approach. These results show the advantages of proposed observer in control of induction motor transient performances. The merits of the proposed control system are also indicated in comparison with a traditional optimal control system.Phd Student : Mehdi Alemi RostamiSupervisor: Dr. Adib Abrishamifar Advisor : Dr . Rajaei SalmasiJudges : Dr. Rahmati , Dr. Arabkhaboori , Dr. Vahedi , Dr. mohammadian, Dr. Radan Day : Wednesday     Date: 2011/12/28    Time:15 Class : 305

Electrical Engineering Department PhD Thesis Defense Session Modeling and Parameter Identification of Brushless Synchronous GeneratorAbstract: In this Thesis, a new average modeling approach for brushless excitation system with improved dynamics was developed using mathematical derivation method. Using an efficient VBR model of the generator and taking into account the dynamics of a variable excitation current during the averaging period are the main features of the presentedmodel. Moreover, the analytic nature of this model makes it suitable for analysis of variable frequency systems as well as control and identification purposes. The proposed model simulation results compared with laboratory tests and experimental studies carried out in an actual power plant confirm the validity of the suggested model in steady state and transient operation. The developed excitation system model is an appropriate model for large disturbance simulations and transient stability studies, where a computationally efficient exciter representation is necessary.By: Mostafa ShahnazariSupervisor: Dr. Abolfazl VahediReferees boards: Prof. Lesani, Prof. Milimonfared, Dr. Shahrtash, Dr. Jalilian, Dr. Arab KhaburiDate: Sunday 13 Nov. 2011   Time: 15:00Room: Class 301, Department of Electrical Engineering

Electrical Engineering Department PhD Thesis Defense Session Uncertainty Measurement and Improvement in Evidential Reasoning Problems using Sensor FusionAbstract: Uncertainty evaluation for sensor fusion results as an open problem to justify the results in an efficient manner is concentrated in this thesis. The Aggregate uncertainty measure, AU, which is presented in Dempster-Shafer (DST) framework, is generalized in two procedures to be applicable to the fusion theories based on free and hybrid Dezert-Smarandache model. These fusion theories are Dezert-Smarandache Theory (DSmT) of combination including DSmC and DSmH also Proportional Conflict Redistribution (PCR) rules of combination. The new developed uncertainty measures are called Generalized Aggregate Uncertainty measure-1 (GAU1) and Generalized Aggregate Uncertainty measure-2 (GAU2). Requirements for these uncertainty measures are discussed theoretically. Additionally, modified forms of the AU measure, GAU1 measure and GAU2 measure are presented. Moreover, in order to achieve a well-organized decision making, a hierarchical sensor fusion framework with supervision of an uncertainty evaluator is introduced which it utilizes the uncertainty measures. Capabilities of the developed uncertainty measures in order to evaluate the DSmT-based fusion results in the information fusion framework are verified by two experimental studies. The designed experiments are target differentiation using ultrasonic sensors and localization problem using cameras’ images. Sensors’ data in these experiments are fused by fusion rules based on the obtained models and then the fusion outcomes are evaluated by the associated uncertainty measures in uncertainty point of view. The results are discussed to illustrate high performance of the new developed generalized aggregate uncertainty measures in the introduced decision making systemStudent : Mahdi KhodabandehSupervisor : Dr. Alireza Mohammad-ShahriAssessment committee: Dr. Behzad Moshiri, Dr. Hamidreza Momeni, Dr. Mohammadreza Jahed-Motlagh, Dr. Aliakbar Jalali, Dr. Mohammad FarrokhiDefense Date: Sunday, October 23, 2011 at 5 PMRoom 303, Electrical Engineering Department

Electrical Engineering Department PhD Thesis Defense Session Low Voltage Low Power Digital to Analog Converter Design for Video ApplicationAbstract: Considering the subject of this thesis which is about low voltage low power current steering digital to analog converters design for high definition video applications, in first step with a wide and comparative approach different types of DACs and more specially the well improved ones are investigated. This procedure resulted in selection of appropriate DAC type for intended high precision and high speed application. Then, considering the fact that every DAC includes two digital and analog parts, and since the analog part has more tremendous effect than digital part on DAC’s overall performance, we focused mainly on improving current mirror, current buffer, and deglitching parts and successfully designed some novel structures which resulted in several international papers. Some achievements of this thesis are the design of high performance current mirrors as one of the main building blocks of current steering DACs. Ultra high output resistance (400GΩ), low voltage supply (0.9V), Ultra low current transfer error (3*10-3%), very low input resistance (0.0058Ω), ultra high input and output compliance (0.058V and 0.055V, respectively), very low offset and power dissipation (0.4aA and 86nW, respectively), wide dynamic range and bandwidth (150dB and 210MHz, respectively) are some of improvements we achieved during current mirror design phase in this thesis. One of the current mirrors which was the perfect choice for providing ultra wide dynamic range, low power consumption, very high output resistance, good precision and minimum voltages at input and output nodes was selected for designing the current steering DAC promised in this thesis. The other important and determinative analog part of current steering DAC is its output section which has a tremendous effect on producing glitch, speed and the effective number of bits. This forced us to put a strong emphasis on proposing improved structures for this (output) part. Utilizing the mentioned current mirror with ultra wide dynamic range, low power consumption, very high output resistance, good precision and minimum voltages at input and output nodes, and also the novel current buffer cell with outstanding deglitching scheme whose wonderful capability is mainly due to its ultra fast settling time, local deglitching, and statistical glitch division schemes, realized most of the aforementioned goals and resulted in design of ultra high speed current steering DAC (2GS/s) with 12Bit precision and high SFDR (73.43dB), very low glitch (0.42PV*s), low supply voltage (1V) and low power consumption (3.446mW). This DAC is perfectly suitable for mixed mode, HDTV, and high speed applications in which large glitch energy is considered as the main issues. Whereas most of the previously reported artworks suffer from high power consumption and high glitch energy. The operation of proposed structures is proved by HSPICE simulations in TSMC 0.18 μm CMOS, BSIM3 and Level49 technology.Student : Khalil MonfarediSupervisor : Dr. Seyed Javad AzhariAssessment committee: Dr. Ahmad Ayatollahi, Dr. Sattar Mirzakuchaki, Dr. Seyed Adib Abrishamifar, Dr. Omid Hashemipour, Dr. Hossein GhezelayaghDefense Date: 19 October 2011 Time: 14 Location: Seminar Hall, Electronic Research Center, Iran University of Science and Technology, Narmak, Tehran, Iran

Electrical Engineering Department PhD Thesis Defense Session Analysis, Simulation and Realization of Single Aperture Monopulse Antenna with Circular PolarizationAbstract: Quantum Cellular Automata (QCA) is an emerging technology which utilizes quantum dots in digital computations. Utilizing the QCA technology for implementing logic circuits is one of the approaches which in addition to decreasing the size of logic circuits and increasing the clock frequency of these circuits, reduces the power consumption of these circuits.Power consumption, Area, Latency, Throughput, Clock frequency and Resistance against attacks are main parameters which are used to evaluate the hardware implementation of a cryptographic algorithm. Using the quantum cellular automata will enhance the mentioned parameters.Hardware design and implementation of A5/1 and Trivium from the stream ciphers and Serpent and Rijndael from the block ciphers and simulation of these implementations are discussed by three methods. These methods involve "implementation using VHDL and simulation by ModelSim", "modular implementation in QCA and simulation by QCADesigner" and "modeling QCA circuits by VHDL and simulation by ModelSim".Student : Mohammad Amin AmiriSupervisor : Dr. MirzakuchakiAvisor: Dr. Rashed MohasselAssessment committee: Dr. Ebrahimi Atani, Prof. Raeesi, Dr. Ayatollahi,Prof. Mohammad Nejad, Prof. Mohammadi: Date of Defense: Monday 90/7/4 , 13 pmElectrical Engineering Department, Class No. 303

Electrical Engineering Department PhD Thesis Defense Session Analysis, Simulation and Realization of Single Aperture Monopulse Antenna with Circular PolarizationAbstract: This thesis describes the design and realization of a multi-mode tracking feed antenna system, for a circularly polarized wave, which can generate sum and difference patterns suitable for monopulse tracking in remote sensing earth stations. It uses TE11 and TE21 modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TE21 generated within the feed is separated from the fundamental mode, TE11 by using a mode coupler. Circular polarization is converted to linear polarization by pin polarizer septum. The design of the multimode corrugated horn, optimum TE21 mode coupler and polarizer are described in some details. The size and shape of the sidewall slots of mode coupler is optimized to provide an efficient coupling. The use of compact mode coupler with a conical corrugated horn makes the design particularly simple and inexpensive. The prototyped horn designed here operates in the frequency range of 7.2-8.8GHz. Sum and delta patterns and polarizer axial ratio are presented. The close agreement between measured and simulated data validates the present designStudent : S.H. Mohseni ArmakiSupervisor : Dr. Farrokh Hojjat-KashaniAvisor: Dr. Rashed MohasselAssessment committee: Dr. M. Khalaj-Amirhoseini, Dr. N. Komijani,Dr. Kamyab, Dr. Moghaddasi: Date of Defense Monday, 26 Sep. 2011, at 15:30Room , Department of Electrical Engineering

Electrical Engineering Department PhD Thesis Defense Session Adaptive Multiple Description Scalable Coding for Peer-to-Peer Video StreamingAbstract: Multiple description scalable coding based on T+2D wavelet decomposition provides a flexible structure for peer-to-peer video streaming with lossy links and heterogeneous nodes. In the present thesis, two different strategies are proposed; one based on segmentation and unequal loss protection of the embedded video bit stream and another based on truncation of the scalable bit stream of each code block. In the first strategy, it is important to find the suboptimal sizes of the bit stream segments. To this end, an analytical relation is found between the optimal sizes of any two successive segments which is the result of analysis of the optimization cost function around the optimal point and smart search of the state space. This idea yields a progressive solution with low computational complexity and identical performance as the local search algorithm.In the second strategy, it is necessary to find the optimal truncation point of each code block within each description. This is a complicated problem requiring a full search in a huge dimensional state space. To design an adaptive low-complexity encoder with arbitrarily unbalanced descriptions, a simple clustering algorithm is proposed for partitioning the CBs into a limited number of clusters. This simple and efficient clustering algorithm significantly reduces the size of redundancy-rate assignment matrix, such that one can find the optimal channel-aware cluster-level redundancy-rate assignment matrix using a low-complexity full search approach. This approach improves the decoding quality compared to the co-echelon adaptive frameworks. In addition, the proposed clustering approach (along with an experimental rate-distortion modeling) may be analytically represented by closed-form relations for low-complexity computation of the optimal encoding parameters. Therefore, an efficient real-time post-encoding adaptation mechanism may be realized.Student : Majid Roohollah Ardestani Supervisor : Dr. Ali Asghar Beheshti ShiraziJury: Dr. V. Tabataba Vakili; Dr. A. Falahati; Dr. B. Abolhassani; Dr. E. Kabir; Dr. H. Aghaei Nia: Date of Defense Sunday, September 11, 2011Classroom No. 302, Faculty of Electrical Engineering

Electrical Engineering Department PhD Thesis Defense Session Efficiency and Torque Ripple Improvement of Six-phase induction motor Abstract: Recently, multiphase machines have been received great deal of attention. Some of the advantages of these machines can be listed as: higher redundancy and reliability under fault conditions, lower torque pulsations, reduced rotor harmonic currents, lower DC-link voltage requirement, lower power per phase, and a reduction in the stator copper loss. The six-phase induction machine (6PIM) is known as an interesting and the most discussed types of multi-phase machines. Until recent years, the literature of 6PIM drives has covered different issues.  Some papers addressed the multi-phase drive efficiency; improving efficiency of six-phase induction machine is an important issue that addressed less in the articles. Six-phase induction motor has 64 space voltage vectors which causes more complexity in selecting of inverters switching. Unsuitable selection of switching table leads to large harmonics especially in low speed and it reduces drive efficiency. The six-phase induction machine has large zero sequence harmonic currents of order . These harmonic currents are varied in various techniques. Decreasing this loss is so essential in six-phase induction machine. Improving of ST-DTC of Six-phase induction machine to reduce voltage and current harmonics and torque pulsation is addressed newly in this thesis. Selecting a suitable method by minimizing these harmonics is very important in DTC of six-phase induction motor. Motors are designed to have maximum efficiency at their nominal point. If the motor load or velocity is under this point, flux should be reduced to have appropriate efficiency. There are a number of approaches for choosing a suitable control method including Loss Model based Control (LMC), Search Control (SC). A flux search controller is proposed to improve the efficiency of direct torque control and field oriented control of six-phase induction machine. The proposed flux search controller is based on adaptive gradient descent of motor flux value with fast response and easy implementation. A proper loss model of six phase induction motor in conjunction with the proposed method has been presented. Stator frequency variation with respect to flux reduction is considered as a new aspect of fast flux search control. Reduction of the flux in the search control technique leads an increase in stator frequency and an error in core loss calculation is occurred if the frequency variation is ignored. The proposed search controller greatly improves efficiency by reducing core loss as well as harmonics loss. The approach not only is easy to implement and adaptive about parameter variations but also requires no additional hardware for practical implementation. The simulation and experimental results presented in this paper verify the effectiveness of the proposed method in improving efficiency of direct torque control and field oriented control of six-phase induction motor drive. Adaptive gradient variation of flux technique decreases the convergence time, noise impact, and increases accuracy of algorithm.  Although using the frequency variation affects the core loss calculation, the SC technique causes an increase in accuracy of the core loss calculation. The proposed loss modeling of DTC of 6PIM can describe dynamic variation of losses in the SC technique not only in 6PIM but also in IM. Flux variation in the SC technique results in variation of core loss; a matter previously worked in literature. However, the flux variation leads to a variation in frequency as well as core loss coefficients. In this thesis, the accuracy of loss calculation and efficiency in the SC technique is improved considering the frequency. Student : Asghar Taheri Supervisor : Dr. Abdolreza RahmatiCo supervisor : Dr. Shahriyar KaboliJury:Dr. Vahedi, Dr. Arabkhabouri,  Dr. Abrishamifar, Dr. Mohammadian, Dr. Kianinezhad:  Date of Defense Saturday 3 sep. 2011, 15 pmElectrical Engineering Department, class NO. 305

Electrical Engineering Department PhD Thesis Defense Session Optimal Design and Construction of Multi Level Tubular Linear Reluctance MotorAbstract:Operation of the tubular linear reluctance motor depends strongly on the motor inductance profile. Therefore, calculating the motor inductance with a good accuracy is very important.in this thesis The exact method for calculating the minimum and maximum inductance is proposed  and field intensity inside the iron core is achieved with regard to eddy current. Finite element method is used for motor simulation and its inductance calculation in every plunger position. For evaluating simulation and calculation results, a prototype TLRM was built and its inductance was measured. Also dynamic modeling of tubular linear reluctance motor is performed considering different conditions, such as eddy current effect, skin & proximity effect , different length condition, the current source inverter fed, plunger lock effect  stability curve.This thesis represents a method for increasing the magnetic force and velocity in tubular linear reluctance motor by implementing step winding structure. Moreover the methods used in inductance calculation and the novel motor modeling are presented. The performance improvements in the proposed motor are proved using experimental results and FEM analysis. At the end, the simulation results are compared with experimental results. Good agreement between experimental and simulation results has been observed.Also in this thesis all methods of increase efficiency of tubular linear reluctance motor are introduced, then optimal design of this motor is preformed and Optimal design method of motor are described by algorithms.In the end, Multi Level Tubular Linear Reluctance Motor with control system and the equipment are made and experimental results are compared with dynamic modeling results. Good agreement between experimental and simulation results has been observed.Student : Ali MosallanejadSupervisor : prof. abbas shoulaieJury: prof. vaezzadeh , Dr fathi , Dr vahedi , Dr arabkhabouri,  Dr JaliliyanDate of Defense:Monday 90/06/14 , 9 amElectrcal Engineering Department, class NO. 303.

Electrical Engineering Department PhD Thesis Defense Session Adaptive-Robust Control of Nonholonomic Wheeled Mobile Robots in Presence of Parametric and Non-parametric Uncertainties with Practical ConsiderationsAbstract: In this thesis, the trajectory tracking problem of nonholonomic wheeled mobile robots (WMRs) in presence of both parametric and non-parametric uncertainties is addressed. A combination of adaptive and robust control is employed using input-output feedback linearization, backstepping control technique and Lyapunov-based control techniques of robotic manipulators in order to solve the trajectory tracking control of uncertain nonholonomic mobile robots. At first, an adaptive-robust backstepping-based controller is proposed to solve global tracking problem of all WMR states for every arbitrary initial condition. The complexity of the proposed backstepping-based controller motivates us to design a simpler unified tracking controller in chapter 5. Therefore, an adaptive-robust feedback linearizing controller is proposed to provide a unified tracking controller with minimum complexity and less design parameters for an integrated formulation of uncertain kinematics and, dynamics of WMRs and uncertain actuator dynamics. Simulation and experimental results are presented to evaluate the proposed tracking controller. Since most of commercial WMRs are not equipped with velocity sensors, an output feedback tracking controller is proposed in chapter 6. This controller only requires position measurements of WMRs. The controller design task is accomplished by using control techniques of robotic manipulators. For this reason, a new input-output model is proposed in this thesis which allows the designer to directly apply the control techniques of robotic manipulators to control nonholonomic WMRs. Simulation results are also presented to evaluate the controller performance. Student: Khoshnam ShojaeiSupervisor: Dr. Mohammad ShahriAdvisor: Dr. FarrokhiReferee Committee Members: Dr. Jahed Motlagh, Dr. Jalali, Dr. Davaei Markazi, Dr. Khaki Sedigh, Dr. MousavianDate: Wednesdayu 24 Agust 2011, Time: 10:00Place: Electrical Engineering Department, Room 305.

Electrical Engineering Department PhD Thesis Defense Session Adaptive Robust Control of a Class of Complex Systems in Presence of Time-varying UncertaintiesAbstract: In this thesis, first, an adaptive robust stabilization algorithm is presented for a class of nonlinear systems with mismatched uncertainties. In this regard, a new controller based on the Lyapunov stability theory is proposed in order to covercome the problem of stabilizing nonlinear time-varying systems with mismatched uncertainties. This method is such that the stability of the closed-loop system is guaranteed in the absence of triangularity assumption. The proposed approach leads to asymptotic convergence of the states of the closed-loop system to zero for unknown but bounded uncertainties. Then, this method is modified so that all the signals in the closed-loop system are uniformly ultimately bounded. Numerical simulation for two different examples, and also for synchronization of time-varying Rossler systems shows the effectiveness of the given algorithm. Next, a method for stabilization of nonlinear systems with non-parametric mismatched uncertainties is introduced. This method is also based on Lyapunov stability theory, and the uncertainty of the system is approximated via an adaptive neural network. The method can be applied to Multi-input systems. Numerical simulations on a vertical take-off and landing helicopter and also two numerical examples show that the presented algorithm has a good performance in the face of mismatched uncertainties.   Finally, the previous algorithm is developed for the systems when all the states are not available. To this end, an observer-based stabilization algorithm based on strictly positive real (SPR)-Lyapunov design is presented. Results show that if the SPR condition is satisfied, one can apply the stabilization algorithm using available outputs.     By:Mohammad Mehdi ArefiSupervisor:Dr. Mohammad Reza Jahed-MotlaghReferee committee Dr. Ali Khaki-Sedigh, Dr. Vahid Johari-Majd, Dr. Mohammad Farrokhi, Dr. Javad Poshtan, Dr. Ali Akbar JalaliDate: August 20, 2011,    Time: 10:00Place: Electrical Engineering Department, Room 305. 

Electrical Engineering Department PhD Thesis Defense Session  Design of State Observer in Nonlinear Systems Based on Switching MethodAbstract: Nowadays considerable amount of researches belongs to the sliding mode observers (SMOs) since they have good characteristics such as fast estimation, robustness to the uncertainties. But their sensitivity to the measurement noise degrades their quality. In this thesis, SMOs are analyzed from point of view of relay feedback systems. That is, based on the new structure, the relation between frequency of oscillations and accuracy or effecting from measurement noise are analyzed and discussed. Hence this thesis is based on three stages of design. In the first stage, it shows that by appropriate design of a compensator in the frequency domain, estimation of SMO becomes less affected from the measurement noise. However this design results some estimation errors. In the second stage of design, using another compensator, accuracy of SMOs is increased, but it results increasing of sensitivity of SMOs to the measurement noise. At the final stage of design, designing two different compensators, both increasing of accuracy and decreasing of sensitivity to the measurement noise are added to the SMOs.  Simulations show the acceptable performance of proposed method, compared to the conventional SMOs.Keywords: sliding mode observers, nonlinear system, relay feedback, frequency of oscillation, linear compensator.  Student: Majid HajatipourSupervisor: Dr Mohammad FarrokhiReviewers: Dr Javad Poshtan; Dr Jahed Motlagh; Dr Davayi Markazi; Dr khaloozadeh; Dr Khaki seddighDefense Date: Sunday 1390/5/30Time: 10:00 Place : Electrical department- 305

Department of Electrical Engineering PhD Defence 396 Improving the radiation characteristics of waveguide feed longitudinal slotted arrayAbstract: A suitable centered longitudinal shunt slot is proposed. It is shown that the proposed slot antenna can be an effective candidate for replacing the conventional longitudinal shunt slot. The proposed structure is realized by adding the V-shaped to the ridge of the single ridge waveguide. The wiggly ridge is placed exactly under the slot. It has been shown that the radiation characteristic of the slot can be varied by changing both slot length and V-shaped depth. In order to design a high performance array composed of the proposed slots, two methods are proposed which both are based on the well known Elliott’s design procedure. One of the methods is called semi-analytical and the other called analytical method. In the semi-analytical method, general relation connecting the backward- and forward-scattering dominant mode coefficients to the slot voltage is derived using available electromagnetic field simulator and by fitting some proper polynomials to the derived data. In analytical method, the V-shaped ridge is approximated by discrete steps. Then, the electric field at each step is found by defining a suitable scalar potential ional and solving it. Finally, the electric field in V-shaped wiggly ridge waveguide is found by considering previously obtained electric fields for each step. The general relation connecting the backward- and forward-scattering dominant mode coefficients to the slot voltage is found using reciprocity theorem and by fitting some proper polynomials to the derived data. The Elliott’s design procedure is used to design some slot antenna using analytical and semi-analytical results. The simulation results show that the butterfly lobe suppression of the proposed array is better than 6dB in comparison to the single ridge waveguide fed array while allowing the beam to scan to a relatively wide angle of 40 degrees. By: Mahdi Moradian Supervisor: Dr. Mohammad Khalaj-Amirhosseini Advisor: Dr. Majid Tayarani Assessment Committee: Dr. Farrokh Hodjat Kashani, Dr. Homayoon Oraizi, Dr. Hashem Vajed Samiei, Dr. Jalil Rashed-Mohassel, Dr. Manouchehr Kamyab THE DEFENCE TAKES PLACE: Monday 7 March 2011, at 15.00 Room 303, Department of Electrical Engineering

Iran University of Science and Technology Electrical Engineering Department PhD Thesis Defense Session 396 Optimal Design Algorithm of Superconducting Fault Current Limiters via Multi Criteria Decision Making Techniques Abstract: Superconducting fault current limiters (SFCL), connected in series with the transmission and distributions lines, are one of the important protection devices in future power systems. Considering unique characteristics of materials in superconducting state, several configurations including resistive and inductive types are presented to limit the fault current based on this phenomenon. The main purpose of this thesis is to propose an algorithm for optimal design of resistive and inductive SFCLs via multiple criteria decision making techniques. To achieve this goal, after a comprehensive survey of previous works, an appropriate model describing electrical, thermal and magnetic behavior of the mentioned SFCLs will be presented to analyse their performance in normal and faulty conditions and to choose important parameters. In the next step, using multiple criteria decision making methods the optimal design process of SFCLs will be explained considering some objectives including optimal limiting performance, minimum losses and voltage sag, appropriate response to transient faults and minimum cost. Then, an improved meta-heuristic multi-objective algorithm will be presented based on simulated annealing to be employed in this purpose. Furthermore, a combined algorithm will be offered to optimize number, size and location of SFCL in power system and the results for the standard IEEE 30-bus test system will be appeared. As an additional study, two new configurations based on autotransformer introduced as well as a modified configuration based on magnetic switch and their performances are analyzed. Electro-thermal modeling and optimization algorithm are made in PSCAD/EMTDC environment and the results are compared by FLUX/2D finite element software. By: Reza Sharifi Supervisor: Dr. Hossein Heydari Referee committee: Dr. Gholami ; Dr. Jadid ; Dr. Shahrtash; Dr. Amjadi; Dr. Javadi Defense Date: Sunday 27/02/2011 Time: 17:00 Place : Electronic Research Center, Seminar Room

Electrical Engineering Department PhD Thesis Defense Session 396 High Impedance Fault Detection and Branch Identification in Distribution Networks Abstract High Impedance Faults (HIFs) usually occur in distribution networks and, generally, cannot activate conventional protection relays because of high impedance at the fault point. These faults often occur when an overhead conductor breaks down and touches high impedance surfaces and/or where the conductors become in contact with a high impedance object such as a tree. The main purpose in HIF detection, in contrary to short circuit faults, is not to protect the system, but to protect the human lives and preventing fire hazards due to arcing phenomenon . In this thesis , for the first time a high impedance fault indicator (HIFI), to be mounted on the poles, is proposed to detect and track down the faulted branch. The main contribution of this thesis is the investigation of employing the magnetic field strength signal (MFSS), measured in the vicinity of the conductors of a feeder as a new signature, to detect HIFs based on a novel pattern recognition method. The proposed HIFI is capable of discriminating HIFs (with broken and unbroken conductor) from other similar phenomena, including capacitor switching, feeder switching, load switching, insulator leakage currents and harmonic load. Also , a new multi criteria pattern recognition based algorithm is presented to detect high impedance fault in distribution feeders. This method has three stages: feature generation, feature extraction and classification. The proposed feature sets are generated by applying the multi-resolution morphological gradient to each of the first three half cycles of the post-disturbance current and MFSS signatures . T hese feature sets are fed to support vector machines with r adial b asis f unction (RBF), as the kernel function, for distinguishing HIFs . Applying the data for HIF, insulator leakage current and harmonic load from field tests and for other similar phenomena from simulations has shown high security and dependability of the proposed method . By: Mostafa Sarlak Supervisor: Dr. Seyyed Mohammad Shahrtash Referee committee: Dr. Kazemi ; Dr. Jamali ; Dr. Analuee ; Dr. Haghifam ; Dr. Khederzadeh Defense Date: Wednesday 11/12/1389 Time: 15:00 Place : Electrical Engineering Department, Room 303

Electrical Engineering Department PhD Thesis Defense Session Sensor Selection in Wireless Sensor Networks for Target Tracking Abstract: Wireless sensor networks formed using unattended ground sensors promise to provide an effective low cost solution for observing a physical phenomenon. Due to the energy limitation of WSN , for such a network to be effective over an extended time, power conservation is an absolute necessity. On the other hand, due to the high density in the network topology, it may not be necessary to active all the sensors in each time instance. This work is concerned with the selection of a subset of sensors for a target tracking. To do so, it is assumed that the locations of all sensors are, a priori, known and the predicted target state obtained from the tracking algorithm is used to approximate the target position. Therefore, the criterion for sensor selection is defined by considering the location of all the sensors relative to the target position. Accordingly, a cost function is proposed based on the spatial correlation obtained using the best estimation of the event source. Then, another cost function is derived using the geometrical dilution of precision (GDOP) metric for power measuring sensors. As a result, a sensor selection algorithm is proposed which adaptively determines the number of active sensors and finds the best active set topology for target tracking. The sensor selection methods are evaluated in terms of event distortion, their RMS errors of the target position, energy consumption, percent of intersection between the active set selected by each approach to the best active set and the execution time. First, It is shown that the distortion achieved by the proposed spatial-based cost function and its corresponding minimum number of active sensors for a given distortion constraint was less than those obtained using the suboptimum distortion function. Moreover, the proposed distortion function is less sensitive to the sensor density and range parameter. Also, simulation results are revealed that the performance of the sensor selection algorithm evaluated by the MSE and also computational burden has been improved compared with other algorithms. By: Mohammad Reza Zoghi Supervisor: Dr. Kahaei Referee committee: Dr. Tabatabavakili ; Dr. Falahati; Dr. Abolhasani; Dr. Olfat; Dr. Navaie Defense Date: Monday 25/11/1389 Time: 17:00 Place : Electrical Engineering Department, Room 214

Electrical Engineering Department PhD Thesis Defense Session Robust observer-based fault diagnosis in nonlinear systems Abstract: Fault diagnosis of complex control systems is one of the most important research topics among control engineering community during the last half century. In recent years, attention has tend ed towards designing of robust fault detection and diagnosis approaches both for linear and nonlinear systems. Many of the proposed methods in this field are based on robust observers which can efficiently estimate system states, in the presence of a wide class of modeling uncertainty and external disturbances. It should be noted that robust state estimation needs special conditions, which will limit its implementation. For nonlinear systems complexity is higher. One of the goals of this thesis is to present a robust method with good accuracy and simplicity compared to the so far presented methods for robust fault detection of nonlinear system. For this purpose, first, a method using the Unscented Kalman Filter (UKF) algorithm for detection of faults in nonlinear systems is proposed. Then convergence of the unscented Kalman filter is investigated and its local convergence conditions are obtained. To show the ability and performance of the presented method it is applied to detect and isolate faults of a nonlinear process, and it is shown that the presented method is superior to linearization-based methods such as Extended Kalman Filter (EKF). Since this filter lonely cannot solve the problem related to presence of uncertainty in the model, the concept of unknown input is introduced, and Unknown Input Observer (UIO) is used for fault detection of linearized model of the presented nonlinear system around the point of operation. It is shown that by considering an unknown input in the system and tacking into account its effect on the design of the observer, both unknown input effects and uncertainties can be decoupled from fault effects. UIO is then extended to a more general case and it will be shown that the algorithm presented by Kalman can be used to calculate the observer gain. Therefore, if the extended Kalman methods for nonlinear systems; such as EKF or UKF is used, UIO can be designed without linearization for fault detection purposes in nonlinear systems. Finally, convergence of the proposed observer will be studied and to demonstrate its ability it is applied to the introduced system. It is shown that the proposed observer is able to distinguish between fault effects and uncertainties or unknown inputs. By: Jafar Zarei Supervisor: Dr. Poshtan Referee committee: Dr. Jahed-motlagh ; Dr. Jalali; Dr. Sadjadian; Dr. Momeni; Dr. Khaloozadeh Defense Date: Monday, February 14, 2011 Time: 17:00 Place : Electrical Engineering Department, Room 305