Thesis: THEORY, SIMULATION, AND IMPLEMENTATION OF GRID CONNECTED BACK TO BACK CONVERTERS UTILIZING VOLTAGE ORIENTED CONTROL
Abstract: This work presents a back to back converter topology with the ability to connect two power systems of different voltages and frequencies for the exchange of power. By utilizing indirect AC/AC conversion decoupling is achieved between the power systems with one of the three-phase, two-level voltage source converters performing the AC/DC conversion that maintains the required DC bus voltage level at unity power factor while the other converter operates in all four quadrants supplying/consuming active and/or reactive power with the other power system. The prototype implementation resides at UW-Milwaukee’s USR Building microgrid test bed facility with an emphasis in the design to approach the requirements for harmonic control as recommended by IEEE 519-2014 without power filtering AC capacitors. The challenge in this project was to develop the model based firmware and control for the custom digital signal controller boards interfaced to Rockwell Automation’s PowerFlex 753-Series converters with only a high level knowledge of the proprietary power structure available.
BSEE from University of Minnesota-Twin Cities, 2004.
Thesis: COUPLED ELECTROMAGNETIC AND THERMAL ANALYSIS AND DESIGN OPTIMIZATION OF SYNCHRONOUS ELECTRIC MACHINES
Abstract: A new technique for coupling the electromagnetic, thermal, and air-flow analysis is proposed for electronically controlled synchronous machines. A computationally efficient finite element analysis (CE-FEA) technique is employed for the electromagnetic field analysis. An equivalent circuit network is used for thermal and air-flow analysis. An iterative algorithm, which exploits the fact that the type of machines studied have very low rotor losses and also a relatively reduced dependency of core losses with temperature and load, has been developed. The overall computational time is significantly reduced in comparison with the conventional coupling method, such that the new technique is highly suitable for large scale optimization studies. An automated design optimization method based on differential evolution algorithms has also been developed and implemented on a multi-core computer system. Example case studies are provided for permanent magnet and for synchronous reluctance machines. Computational and experimental results from prototype motors are included.
BSEE from Changchun University of Technology,
Project Service Engineer
AvePoint in Changchun, China
Thesis: MODELING AND PROTECTION SCHEME FOR IEEE 34 RADIAL DISTRIBUTION FEEDER WITH AND WITHOUT DISTRIBUTED GENERATION
Abstract: The existing power system was not designed with distribution generation (DG) in mind. As DG penetration is being considered by many distribution utilities, there is a rising need to address many incompatibility issues which puts a big emphasis on the need to review and implement suitable protection scheme. The usual practice for existing distribution feeders is the Overcurrent scheme which includes coordination between fuses and reclosers. But when DG is added to the distribution feeder, the configuration is no more radial as there is contribution of fault currents from the DG’s and if the existing protection scheme is applied then this could lead to various issues like fuse misoperation or nuisance tripping considering temporary and permanent fault conditions.
This thesis presents a study on the modeling of existing IEEE 34 radial distribution feeder and scaling of the system from 24.9kV to 12.47kV keeping in mind the existing conditions and also proposes a protection scheme with and without the addition of DG’s to the feeder nodes. The protection scheme involves providing appropriate relaying with suitable fuse selection and Current transformer settings. Considerations for proper transformer grounding and capacitor bank fusing protection is also simulated and reviewed. When DG’s added, the results show increase in fault contribution and hence causing misoperations which needs to avoided. Relaying considerations are also provided when an islanded mode occurs. The entire analysis has been simulated by a combination of various tools like Aspen One liner, CYMDist and Wavewin with occasional simulations and calculations performed in MATLAB environment.
BS EEE, SASTRA University, India, 2012
Controls & Protection Engineering at National Grid
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.
BSEE from Birzait University, Palestine, 2009
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
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.
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.
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.
BSEE University of Milwaukee-Wisconsin, 2004
Senior Development Engineer
Thesis Title: A NOVEL BATTERY CHARGER FOR AUTOMOTIVE APPLICATIONS
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.
BSEE from University of Wisconsin-Milwaukee, 2002.
Project Hardware Engineer