Dissertation: Modeling and Simulation of Conducted EMI Noise Generated in the Electric Power Converters of the Electric and Hybrid Electric Vehicles
Abstract: In developing a complex power electronic system, proper modeling at prototype sample level can save the time and cost to develop final product. Hybrid Electric Vehicle (HEV) is equipped with several high-powered electric devices such as DC/DC converters and DC/AC inverters. Considering that there are many restrictions in mounting and wiring the electric power system in engine room, analysis and modeling of Electromagnetic Interference (EMI) coupling path is crucial in designing optimal electric power system satisfying various EMC regulations. In this thesis, conductive common mode (CM) and differential mode (DM) equivalent models for those electric power converters used in Hybrid Electric Vehicles (HEV) were developed and evaluated through the simulation both in time domain and frequency domain. The simulation results were compared to those of real experimental tests performed in EMC testing Laboratory. It is confirmed that the suggested noise equivalent models followed the actual power electric systems in the point of conducted CM and DM EMI view.
Dissertation: "SCR-BASED WIND ENERGY CONVERSION CIRCUITRY AND CONTROLS FOR DC DISTRIBUTED WIND FARMS"
Abstract: The current state of art for electrical power generated by wind generators are in alternating current (AC). The wind farms distribute this power as 3-phase AC. There are inherent stability issues with AC power distribution. The grid power transfer capacity is limited by the distance and characteristic impedance of the lines. Furthermore, wind generators have to implement complicated, costly, and inefficient back-to-back converters to implement AC generation. AC distribution does not offer an easy integration of energy storage. To mitigate these drawbacks with AC generation and distribution, direct current (DC) generation and high voltage direct current (HVDC) distribution for the wind farms is proposed. DC power distribution is inherently stable. The generators convert AC power to DC without the use of a back-to-back converter. DC grid offers an easy integration of energy storage.
The proposed configuration for the generator is connected to a HVDC bus using a 12 pulse thyristor network, which can apply Maximum Power Point Tracking (MPPT). To properly control the system, several estimators are designed and applied. This includes a firing angle, generator output voltage, and DC current estimators to reduce the noise effects. A DSP-based controller is designed and implemented to control the system and provide gate pulses. Performance of the proposed system under faults and drivetrain torque pulsation have been analyzed as well. Converter paralleling when turbines operate at different electrical power levels are also studied. The proposed new Wind Energy Conversion System (WECS) is described in details and is verified using MATLAB®/ Simulink® simulation and experimental test setup. The proposed solution offers higher reliability, lower conversion power loss, and lower cost. The following is proposed as future work.
Study different control methods for controlling the SCR’s. Investigate reducing torque pulsations of the PMSG as well as using the proposed power conversion method for DFIG turbines. Explore options for communication/control between PMSG, circuit protection and grid-tied inverters. Investigate the best possible configuration for DC storage/connection to the HVDC/MVDC bus. Study the filtering needed to improve the DC bus voltage at the generator.
MSEE from Marquette University, Milwaukee, WI, 2001.
BSEE University of Wisconsin-Milwaukee, Milwaukee, WI, 1997.
Dissertation: "LITHIUM-ION ULTRACAPACITOR ENERGY STORAGE INTEGRATED WITH A VARIABLE SPEED WIND TURBINE FOR IMPROVED
POWER CONVERSION CONTROL"
Abstract: The energy of wind has been increasingly used for electric power generation worldwide due to its availability and ecologically sustainability. Utilization of wind energy in modern power systems creates many technical and economical challenges that need to be addressed for successful large scale wind energy integration. Variations in wind velocity result in variations of output power produced by wind turbines. Variable power output becomes a challenge as a number of wind turbines integrated into power systems increase. Power variations cause voltage and frequency disturbances that may lead to activation of relay protective equipment, that sense these disturbances, which may result in power outages. While a majority of power produced in modern power systems comes from synchronous generators that have large inertias and whose control systems can compensate for slow power variations in the system, faster power variations at the scale of fraction of a second to the tens of seconds can seriously reduce reliability of power system operation. Energy storage integrated with wind turbines can address this challenge. In this dissertation, lithium-ion ultracapacitors are investigated as a potential solution for filtering power variations at the scale of tens of seconds. Another class of issues related to utilization of wind energy is related to economical operation of wind energy conversion systems. Wind speed variations create large mechanical loads on wind turbine components, which lead to their early failures. One of the most critical components of a wind turbine is a gearbox that mechanically couples turbine rotor and generator. Gearboxes are exposed to large mechanical load variations which lead to their early failures and increased cost of wind turbine operation. This dissertation proposes a new critical load reduction strategy that removes mechanical load components that are the most dangerous in terms of harmful effect they have on a gearbox, resulting in more reliably operation of a wind turbine.
BSEE, University of Belgrade, Belgrade, Serbia, 2004.
Dissertation: "TRANSIENT STABILITY IMPROVEMENT FOR DFIG WIND TURBINES USING ULTRACAPACITOR"
Abstract: Wind energy source is characterized as variable and unpredictable. A random wind speed and blade rotational turbulence can produce fluctuations on the voltage and power supplied into the system. This fluctuated power makes the wind power undispatchable, causing frequency deviations and power outage when wind power penetration is significant. The fluctuating power will impact on power balance and voltage at the point of common coupling. Output power of wind turbine is cubic function of the wind speed. Since wind speed is a nearly random parameter, the output power of the wind turbine is also random process. Even a small variation of wind speed could cause a large variation in the output power. As a result, a large voltage fluctuation may cause voltage variations outside the regulation limit at connection point.
Energy storage devices such as batteries, ultra capacitors, super inductors, and flywheels can be utilized in a hybrid system to solve this problem. A selective control method to mitigate the power fluctuations using the rotor inertia is introduced in the literature. This method is also modified to obtain better energy capturing efficiency. The energy extracting capability using this method is comparable with other methods such as Maximum Power Extraction (MPE) algorithm. In this thesis, a new integrated topology of DFIG wind turbine and Ultracapcitor is introduced. The Ultracapcitor is directly placed on the DC bus of the power conversion device on the rotor. A control technique is developed to adjust the active and reactive power of the turbine, apply power smoothing, and keep the DC bus voltage within an acceptable range.
Matlab Simulink simulation results for various cases are performed on a doubly fed induction generator that verifies the theoretical analysis.
Thesis: SPEED AND TORQUE CONTROL OF PERMANENT MAGNET SYNCHRONOUS GENERATORS FOR WIND POWER APPLICATIONS
Abstract: The world is constantly increasing its need for electrical power. Electronic devices are gaining greater popularity throughout the world. Studies show that power consumption will increase over 40% in the next 20 years. As a result new technologies are being investigated to help supply the need for the increased electrical power.
Energy resources are separated into two major groups: Non-Renewable and Renewable. Power production from non-renewable resources has been around for many, many, decades. The most widely used source of non-renewable resources is the coal-fired power plant. Even though coal has been well established it does have some undesired effects on the environment. It tends to add pollution, in the form of "greenhouse gasses", to the environment and the supply is limited. The concept of producing power from renewable resources has regained popularity in recent years. Hydroelectric power plants have been used all over the world for many years. It is non-pollution and as long as water in the river keeps flowing the source for power will keep replenishing itself. Other forms of renewable energy power production are from wind, solar, and geothermal energy sources. Even though the renewable energy sources are considered to be non-polluting they do have some drawbacks. For example, power production is not always consistent and there are some undesirable impacts to the environment.
This thesis investigates one form of renewable energy power production. Wind energy has had an increasing amount of research to support it. This paper investigates maximum power production profile of a wind turbine containing a permanent magnet synchronous generator and implements both speed and torque controls during instances of higher wind speeds. Implementation is supported through simulation results.
BSEE from University of Wisconsin-Milwaukee, 1998.
BSEE from University of Wisconsin-Milwaukee, 2002.
Abstract: In this thesis, a new power electronics topology is introduced for battery pulse charging. The topology is based on a bidirectional isolated Cuk converter. The charging method provides positive and negative current and resting periods. This charging method results in less generated heat and longer battery life cycle. Different operating modes of the system and its small signal analysis are presented. The small signal system has been modeled using MATLAB. Simulation results are also provided to validate the mathematical analysis.
Thesis Title: A Novel Battery Charger For Automotive Applications.
He worked for Moshanir Power Engineering Company, Tehran, Iran, from 1998 to 2001. He also worked for ForHealth Technologies, Inc., Daytona Beach, Florida, from 2004 to 2005 on an automated syringe filling device. Dr. Nasiri is presently a Professor in the Department of Electrical Engineering and Computer Science at the University of Wisconsin-Milwaukee, where he is the director of power electronics and electric motor drives laboratory. His research interests are renewable energy systems including wind and solar energy, and energy storage. Dr. Nasiri has published numerous technical journal and conference papers on related topics. He also holds four patent disclosures. He is a co-author of the book "Uninterruptible Power Supplies and Active Filters," CRC Press, Boca Raton, FL.
Dr. Nasiri is currently an Editor of IEEE Transactions on Smart Grid, Associate Editor of IEEE Transactions on Industry Applications, Associate Editor of the International Journal of Power Electronics, and Associate Editor of Journal of Power Components and Systems. He is also a member of IEEE Industry Applications, Industrial Electronics, Power Electronics, Power and Energy, and Vehicular Technologies Societies. He has also been a member of organizing committee for ECCE and IECON conferences.
He is the primary investigator on several federally and industry funded projects including "Lithium-Ion Ultracapacitors integrated with Wind Turbines Power Conversion Systems to Extend Operating Life and Improve Output Power Quality" funded by DOE, "Characterization of Energy Storage System for Wind Energy Support" funded by NSF, "Integrated Alternative Power Systems" funded by US Army, "Utilizing Energy Storage with PV for Residential and Commercial Use" funded by We Energies and several other industry projects. Dr. Nasiri was the recipient of the 2010 UWM Graduate School/UWM Foundation Research Award. He was also selected as the 2010 Young Engineer of the Year by Engineers and Scientists of Milwaukee (ESM).
Dissertation: "SERIES VOLTAGE COMPENSATION FOR DOUBLY-FED INDUCTION GENERATOR WIND TURBINE LOW VOLTAGE RIDE-THROUGH SOLUTION"
Abstract: Wind is clean and unlimited free source of energy. But in order for the wind energy to be effectively and efficiently harvest without interruption, the wind generators required to ride-through grid disturbances and support the grid during voltage sag events. The Doubly-Fed Induction Generator (DFIG) is known for its poor response to the voltage sags. This work develops an approach to provide a robust ride through technique for the DFIG during different types of voltage sags.
In this work, a mathematical model for the DFIG is developed and used to analyze the voltage sags effects. The DFIG stator flux is the main state that affects the system during the voltage sags. A component of the stator flux declines with the slow time constant of the generator during sudden voltage sag and forces a large rise of current in the rotor windings. This current rise damages double conversion power electronics converter connected to the rotor winding.
The existing techniques for Low Voltage Ride Through (LVRT) solutions have many drawbacks. In brief, they introduce undesirable spikes in generator torque and currents. In addition, they do not provide support to the grid during low voltage conditions.
In order to mitigate the effect of the slow declining component of the stator flux during voltage sags, the system is augmented with a series converter on stator circuitry. The converter injects a voltage on the stator to correct the air gap flux and to ultimately prevent the rotor current rise. A dead-beat control technique is developed to adjust the converter. In addition to the extensive computer simulation, a laboratory scale prototype is developed to validate the proposed solution. The size of the energy storage system required for the converter is also discussed in this thesis.
Future work directions are proposed including more robust control technique, minimizing number of additional parts and bigger laboratory scale prototype.
MSEE in Signal and System, University of Detroit Mercy, Detroit, USA, 2005.
BS in Industrial Automation, Palestine Polytechnic University, Palestine.
Thesis: A LINEAR GENERATOR FOR POWERING IMPLANTED ELECTRONIC DEVICES
Abstract: Due to recent developments in power electronics devices and systems, permanent magnet machines are finding many applications in various fields, including automotive systems and renewable energy. These machines provide high efficiency, compact size, robustness, light weight, and low noise. These features qualify them as the best suitable machine for medical applications. The system proposed is a self-contained, small size, and reliable device that can continuously provide power. The proposed linear generator will have two layers of Permanent Magnets (PM) and one layer of coils. It generates power from multidirectional movement. The movement of the device will cause the middle coils layer to move. The relative movement of the coils versus PMs, on two sides, creates a varying flux in the windings. This change in flux produces voltage in the winding and can be converted into electrical power if a load is connected. In order to provide a continuous power source, the muscle used in this system must not stop working. The best option for such a system is to use a muscle that is linked to the respiratory system. Some of these muscles are accessible without having to tap into the windpipes themselves. There are many potential locations in the human body for implantation of the proposed device. The primary target location is the abdominal wall, due to continuous movement, sufficient travel distance and small surgical risks. The output voltage produced by the generator is a very small, alternating-current (AC) waveform, which must be appropriately transformed and rectified for a given load.
BSEE from American University of Sharjah, United Arab Emirates, 2006.
Dissertation: Integration of Permanent Magnet Synchronous Generator Wind Turbines into Power Grid.
Abstract: Wind energy is becoming a major source of generating electrical energy. High price of oil and environmental issues are the most incentives to develop wind power plants. Due to high price of foundation of wind farms, employing variable speed wind turbines to maximize the extracted energy from blowing wind is more beneficial.
On the other hand, since wind power is intermittent, integrating energy storage systems with wind farms has attracted a lot of attention.
These two subjects are addressed in this dissertation in detail. Permanent Magnet Synchronous Generators (PMSG) are used in variable speed wind turbines. In this thesis, the dynamic of the PMSG is investigated and a power electronic converter is designed to integrate the wind turbine to the grid. The risks of PMSG wind turbines such as low voltage ride through and short circuits, are assessed and the methods of mitigating the risks are discussed.
In the second section of the thesis, various methods of smoothing wind turbine output power are explained and compared. Two novel methods of output power smoothing are analyzed: Rotor inertia and Super capacitors. The advantages and disadvantages of each method are explained and the dynamic model of each method is developed. The performance of the system is evaluated by simulating the wind turbine system in each method.
The concepts of the methods of smoothing wind power can be implemented in other types of wind turbines such as Doubly Fed Induction Generator (DFIG) wind turbines.
Assistant Professor of Electrical and Computer Engineering Department,
Khaje Nasir Toosi University of Technology,
MSEE from Sharif University of Technology, Tehran, Iran, 2003.
BSEE from Isfahan University of Technology, Isfahan, Iran, 2001.
Dissertation: "ENERGY STORAGE FOR SHORT-TERM AND LONG-TERM WIND ENERGY SUPPORT"
Abstract: Wind farm output power fluctuations create adverse effects on the voltage, frequency, and transient stability of the utility grid. Short term wind farm power variations and steep ramp rates cause voltage instability, especially if the farm is located in weak grid areas. In this diisertation, integration of wind energy with energy storage devices to support the short-term shortcomings of wind energy is discussed. A turbine level hybrid configuration of an energy storage system is used to limit the power ramp rate and apply power smoothing. The utilized energy storages devices are zinc bromide flow battery and Lithium-Ion Capacitors (LIC). The actual models of the battery and capacitor, which are derived from testing, are used in this study. The wind farm power is also modeled using measured wind speed data. FCP and ACP as two new concepts have been introduced to evaluate the effect of energy storage system for wind energy support. The analyses show that significant improvements can be made to shape the output power of the farm using practical and turbine level energy storage systems.
Moreover, the dissertation studies a wind farm integrated with a storage device in order to shift the wind power generation to the peak demand periods. A model of system including practical utility level battery integrated with wind farm at wind turbine level is developed and presented. In order to measure the effect of this integration, actual profiles of load, wind energy, and other power sources is studied and the Effective Load Carrying Capability (ELCC) for wind energy, after and before adding the battery, is calculated. Results show that the battery can make some improvements in the ELCC of wind energy.
A wind turbine emulator is built in the lab, and was connected to a storage device, which is tied to the grid. Different tests were conducted at various situations. The wind emulator power data indicates the need for a mechanism to reduce the uncertainty of the wind power. The analysis and figures show that wind power variations and fluctuations can be mitigated using a storage system with a proper control algorithm.
MSEE from Sharif University of Technology, Tehran, Iran, 2005.
BSEE from Shiraz(Pahlavi) University , Shiraz, Iran, 2003.
Thesis: Design and Implementation of a Solar Powered Electric Golf Cart
Abstract: With the rapidly growing energy demand and shrinking supply of expendable resources, recently, much attention has been paid to alternative energy sources and more efficient ways of harnessing energy. The Photovoltaic (PV) solar cells can directly convert sunlight to electricity. In this research work, design, simulation, and implementation for utilization ofsolar PV panels to power a golf cart have been performed. Three PV panels are installed on top of a golf cart and are designed to charge a 36 volt battery system. The maximum power rating of the three panels is 261 watts. This rating is the power output under Standard Test Conditions known as STC. We have also desined and utilized a Maximum Power Point Tracking (MPPT) intelligent controller which is able to vary the voltage of the panel to keep its operating point closer to its maximum output power at different sun irridations.
The actual power gain over a non-MPPT controller with the same panel will vary with conditions, but a 10-30% gain is typical. We are applying a multi-stage charging technique that allows for a fuller battery charge without reducing the battery life or "boiling off" the electrolyte. The battery is held at a higher voltage for a period of time while it gets the full charge, and then the voltage is reduced to provide maintenance charge without overcharging the battery. Temperature compensation avoids excessive electrolyte usage and thermal runaway at higher temperatures and helps compensate for increased internal resistance in the battery at lower temperatures. This results in a longer battery life due to not overcharging at higher temperatures while still preserving full charges at low temperatures.
The proposed system has been designed, modeled, implemented and tested. The results are presented and discussed in this thesis. The test results indicate that the installed PV panels can provide enough power for modest usage of the cart.
MSEE University of Tarbiat Modaress, Tehran, Iran, 2005
BSEE University of Polytechnic, Tehran, Iran, 2002
Dissertation: "MULTI-LEVEL MEDIUM VOLTAGE INVERTER FOR DC DISTRIBUTED WIND FARM TO ESTABLISH GRID INTERFACE AND PROVIDE ANCILLARY SUPPORT"
Abstract: Wind energy has gained in popularity in recent years due to cost, security and environmental concerns associated with conventional energy sources like fossil fuels. However, the utilization of wind energy in power systems creates many technical and non-technical challenges that need to be addressed for successful integrations. The main technical issues related to wind energy are its uncertainty and variability and their impacts on stability, reliability and quality of the electric power. In systems with high wind energy penetrations, unlike conventional generations, sudden changes in active and/or reactive power demand cannot be supported by wind energy. This lack of demand support may create unwanted voltage and frequency variations in the grid. On the hand, the existing AC distributed wind farms have several drawbacks including complexity, higher cost, and lower efficiency.
In this dissertation, a medium voltage direct current (MVDC) distribution system for wind farms is investigated. The proposed system offers higher reliability, lower cost, higher efficiency and more importantly grid support. It also allows for easier integration of energy storage systems at DC level. Design, control, implementation, and testing of a three-level medium voltage inverter are presented. The inverter can provide active and reactive power support to the grid in case of frequency and voltage droops. Simulation and experimental results are presented to verify the viability of the proposed system and control techniques.
MSEE from Illinois Institute of Technology, Chicago. 2003
BSEE from Maharaja Sayajirao University of Baroda, INDIA. 2000
Thesis: X-ray Tube Induction Motor Design Optimization Technique
Abstract: High power CT X-ray tubes require the use of a rotating target to ensure the focal track is kept below the material’s temperature limit during x-ray generation. The target rotation is driven by a mono or poly-phase induction motor. Modern x-ray tubes vary in envelope size, bearing technology, moment of inertia, and have inherent motor design challenges such as large air gaps and wide temperature operating ranges leading to various motor sizes and performance requirements. An approach to design optimization utilizing Design Analysis of Computer Experiments with consideration for Design Analysis for Cost will be defined and demonstrated on a 3-phase induction motor for an x-ray tube. Multiple X’s (inputs) will be defined from envelope/size limitations, performance requirements, and standard induction motor design considerations. Four Y’s (outputs), including three performance requirements and one requirement to minimize cost, will be optimized through a total of 18,000 potential designs. This parameterized electro-mechanical design optimization achieves the simultaneous objectives of required performance in a small and lower cost package, achieving almost 50% estimated cost reduction.
This paper will present the approach and execution for an optimized induction motor design meeting all requirements, and practical application will be demonstrated experimentally on design prototypes with component level dynamometer bench tests, hence validating the software design tool.
Thesis: WIND TURBINE ENERGY STORAGE LEVEL FOR LOW VOLTAGE RIDE THROUGH (LVRT)
Abstract: Renewable energy is a green source of energy that is clean, available and sustainable. Wind energy generation has been experiencing the largest growth among renewable sources due to lower cost and advanced technologies. Wind energy power plants or farms need low maintenance and last for long time. The increasing higher penetration of wind energy in the grid has transformed wind energy into major player in grid operation and economics. Wind energy systems now have to participate in grid support and provide ancillary services.
Variable wind speed leads to variable wind power generation, voltage fluctuations, and frequency deviations, which are the main problems related to wind energy integration into grid. These problems become more evident in weak grids. In addition, wind farms have to take the grid problems into consideration and have to provide support during grid instability and transients.
In this thesis, a PMSG wind turbine full energy conversion system design and modeling have been performed using Matlab Simulink. The system is a grid integrated and applies MPPT control to extract the maximum power from the wind and utilizes a full conversion circuitry to interface the unregulated generator AC power to the grid. Modules of Lithium-Ion Capacitors (LIC) have been placed on the DC bus in order to support the grid with wind energy power smoothing and LVRT. LICs offer high power density and reasonable energy density. During grid faults, wind energy can be stored in the LICs and discharged into grid as soon as the voltage restored. This feature will support the grid to stabilize the voltage. Detailed modeling of the architecture and controls have been performed to verify the viability of the proposed system.
Ramazan Bayindir is a Professor at the Technology Faculty, Department of Electrical-Electronic Engineering, Gazi University, Ankara, Turkey. He graduated from the
Electrical Education Department, Technical Education Faculty in Gazi University, Ankara, Turkey, in 1992. He holds M.Sc. and Ph.D. degrees from Gazi University, Ankara, received in 1998 and 2002, respectively. His main interests include power electronics, electrical machines, power factor correction, microcontroller programming and renewable energy.
Hesamedin H. Sadeghi received the B.S. degree in electrical engineering from Sharif University of Technology, Tehran, Iran, the M.S. degree in power engineering from the University of Manchester Institute of Science and Technology, Manchester, England, and the Ph.D. degree in electronic systems engineering from Essex University, Colchester, U.K., in 1980, 1984, and 1991, respectively.
In 1992, he was appointed as a Research Assistant Professor at Vanderbilt University, Nashville, TN. During 1996-1997, and 2005-2006 he was a Visiting Professor at the University of Wisconsin, Milwaukee. He joined Amirkabir University of Technology, Tehran, Iran where he was promoted to the position of Full Professor of electrical engineering. He holds 3 patents and is the author or coauthor of one book and over 250 scientific papers published in reviewed journals and presented at international conferences. His current research interests include electromagnetic non-destructive evaluation of materials and electromagnetic compatibility issues in power engineering. Professor Sadeghi is a senior member of IEEE.