Master of Science / Department of Electrical and Computer Engineering / Shelli K. Starrett / This thesis introduces a Vehicle to Grid (V2G) system which coordinates the charging, and discharging among the Electric Vehicles (EVs) and two-test systems, to help with peak power shaving and voltage stability of the system. Allowing EVs to charge and discharge without any control may lead to voltage variations and disturbance to the grid, but if the charging and discharging of the EVs is done in a smart manner, they can help the power network. In this thesis, fuzzy logic controllers (FLC) are used to control the flow of power between the grid and the electric vehicles. The presented work in this thesis mainly focuses on the control architecture for a V2G station that allows for using EVs batteries to help the grid’s voltage stability. The designed controllers sustain the node voltage, and thus also achieve peak shaving. The proposed architectures are tested on 16 -generator and 6-generator test systems to examine the effectiveness of the proposed designs. Five fuzzy logic schemes are tested to illustrate the V2G system’s ability to influence system voltage stability. The major contributions of this thesis are as follows: 
 • FLC based control tool for V2G station present at a weak bus in the system. • Investigate the effect of the station location and voltage sensitivity. • Comparison of chargers providing real power versus reactive power. • Simulation of controller and system interactions in a daily load curve cycle. Keywords: State of Charge (SOC), Electric Vehicle (EV), Fuzzy Logic Controller (FLC), Vehicle to grid (V2G), and Power System Voltage Stability.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Shelli K. Starrett / Monitoring and control of modern power systems have become very complex tasks due to the interconnection of power grids. These large-scale power grids confront system operators with a huge set of system inputs and control parameters. This work develops and compares intelligent systems-based algorithms which may be considered by power system operators or planners to help manage, process, and evaluate large amounts of data due to varying conditions within the system. The methods can be used to provide assistance in making operational control and planning decisions for the system in a timely manner. The effectiveness of the proposed algorithms is tested and validated on four different power systems. First, Artificial Neural Network (ANN) models are developed and compared for two different voltage collapse indices and utilizing two different-sized sets of inputs. The ANNs monitor and evaluate the voltage profile of a system and generate intelligent conclusions regarding the status of the system from a voltage stability perspective. A feature reduction technique, based on the analysis of generated data, is used to decrease the number of inputs fed to the ANN, decreasing the number of physical quantities that need to be measured. The major contribution of this work is the development of four different algorithms to control the VAR resources in a system. Four different objectives were also considered in this part of the work, namely: minimization of the number of control changes needed, minimization of the system power losses, minimization of the system's voltage deviations, and consideration of the computational time required. Each of the algorithms is iterative in nature and is designed to take advantage of a method of decoupling the load flow Jacobian matrix to decrease the time needed per iteration. The methods use sensitivity information derived from the load flow Jacobian and augmented with equations relating the desired control and dependent variables. The heuristic-sensitivity based method is compared to two GA-based methods using two different objective functions. In addition, a FL algorithm is added to the heuristic-sensitivity algorithm and compared to a PS-based algorithm. The last part of this dissertation presents the use of one of the GA-based algorithms to identify the size of shunt capacitor necessary to enhance the voltage profile of a system. A method is presented for utilizing contingency cases with this algorithm to determine required capacitor size.

Master of Science / Department of Electrical Engineering / William B. Kuhn / During the development of an educational renewable energy production platform, it was found that there were no low-cost, efficient grid-tie interfaces for a 160 W DC wind turbine. Typically, a small DC wind turbine is used in conjunction with a rechargeable battery bank or, if the wind turbine is directly interfaced with a grid-tie inverter, a regulator with a diversion-load. The use of batteries is undesirable due to their high-cost and high-maintenance characteristics. Diversion loads by nature waste power, as any excess energy that cannot be accepted by a battery or inverter is usually converted into heat through a resistive element. Initially, a 24 V DC, 160 W Air Breeze small wind turbine was directly connected to an Enphase Energy M190 grid-tie micro-inverter. The 24 V DC Air Breeze wind turbine is designed to charge a battery or bank of batteries while the M190 micro-inverter is designed to convert the DC output of a 200 W solar panel to grid-tied AC power. As expected, the power-production response time associated with the small wind turbine and the power-accepting, load-matching response time of the micro-inverter were not compatible. The rapidly changing power output of the small wind turbine conflicted with the slow response time of the micro-inverter resulting in little power production. Ultimately, the response time mismatch also produced sufficiently large voltage spikes to damage the turbine electronics. In this thesis, a solution for a low-cost, efficient grid-tie interface using no batteries and no diversion load is presented. A capacitance of eight Farads is placed in parallel with the small wind turbine and the micro inverter. The large capacitance sufficiently smoothes the potential abrupt voltage changes produced by the wind turbine, allowing the micro-inverter adequate time to adjust its load for optimal power conversion. Laboratory experiments and data from an implementation of such a parallel super capacitor wind turbine to grid-tie micro-inverter configuration are provided along with DC and AC power production monitoring circuits interfaced with a micro controller.

Master of Science / Department of Electrical and Computer Engineering / Sanjoy Das / Noel Schulz / Electrical power, although convenient form of energy to distribute and use, cannot easily be stored in large quantities economically. Most electrical power generated by utility plants is consumed simultaneously in real time. However, in some cases, energy storage systems become crucial when power generated from sources does not fulfill peak power load demand in a power system or energy storage systems are needed as backup. Due to these reasons, various technologies such as batteries, ultracapacitors (UC), superconducting magnetic energy storage (SEMS) and flywheels are beneficial options for energy storage systems. Shipboard power systems must use one or more energy storage systems in order to backup the existing power system if locally generated power is unavailable. This will lessen the effect of voltage sags on power quality, and improve system reliability. This report mainly focuses on the design of a Boost DC-DC converter and the integration of that converter with a previously designed battery storage model, as well as the effect of varying loads at the end of the converter.

Master of Science / Department of Electrical and Computer Engineering / Noel Schulz / Transmission networks are an important part of an electric power system. They help transfer power from the point of generation (power plants) to the substation. In order to minimize losses during power transfer, the lines are operated at high voltages. The high voltage lines not only have a high power transmission capacity, but they are also prone to faults of larger magnitudes. Thus the occurrence of such faults results in a need for the faults to be cleared quickly in order to limit damage caused to the system. Hence, relays are installed at the Buses to provide protection to the lines. Transmission lines in a power system are most commonly protected by distance relays that use directional comparison schemes. However, due to the simplicity of line differential schemes, there has been an increase in the use of differential relays for complex networks. Moreover, since the relays require only current as the operating parameter, their settings can be determined easily. This report discusses the design of a line current differential protection scheme for a transmission line using SEL 311L relays. The relay settings have been determined and then tested for seven fault scenarios, three internal fault points and four external fault points. To set and test the relays, AcSELerator Quickset, SEL 5030 and PowerWorld programs have been used. Real life power system is simulated with the help of SEL AMS (Adaptive Multichannel Source) that acts as the source to provide the required data to the relays. The relays trip and open the breaker contacts for an internal fault. During an external fault, the relays do not trip and the breaker contacts remain closed. The response of the relays in case of communication failures has been discussed.

Master of Science / Department of Electrical Engineering / William B. Kuhn / Designers of mixed-signal systems must understand coupling mechanisms at the system, PC board, package and integrated circuit levels to control crosstalk, and thereby minimize degradation of system performance. This research examines coupling mechanisms in a RF-targeted high-resistivity partially-depleted Silicon-on-Insulator (SOI) IC process and applying similar coupling mitigation strategies from higher levels of design, proposes techniques to reduce coupling between sub-circuits on-chip. A series of test structures was fabricated with the goal of understanding and reducing the electric and magnetic field coupling at frequencies up to C-Band. Electric field coupling through the active-layer and substrate of the SOI wafer is compared for a variety of isolation methods including use of deep-trench surrounds, blocking channel-stopper implant, blocking metal-fill layers and using substrate contact guard-rings. Magnetic coupling is examined for on-chip inductors utilizing counter-winding techniques, using metal shields above noisy circuits, and through the relationship between separation and the coupling coefficient. Finally, coupling between bond pads employing the most effective electric field isolation strategies is examined. Lumped element circuit models are developed to show how different coupling mitigation strategies perform. Major conclusions relative to substrate coupling are 1) substrates with resistivity 1 kΩ·cm or greater act largely as a high-K insulators at sufficiently high frequency, 2) compared to capacitive coupling paths through the substrate, coupling through metal-fill has little effect and 3) the use of substrate contact guard-rings in multi-ground domain designs can result in significant coupling between domains if proper isolation strategies such as the use of deep-trench surrounds are not employed. The electric field coupling, in general, is strongly dependent on the impedance of the active-layer and frequency, with isolation exceeding 80 dB below 100 MHz and relatively high coupling values of 40 dB or more at upper S-band frequencies, depending on the geometries and mitigation strategy used. Magnetic coupling was found to be a strong function of circuit separation and the height of metal shields above the circuits. Finally, bond pads utilizing substrate contact guard-rings resulted in the highest degree of isolation and the lowest pad load capacitance of the methods tested.

Master of Science / Department of Electrical and Computer Engineering / Steven Warren / Polysomnography is a method to obtain physiological signals from individuals with potential sleep disorders. Such physiological data, when acquired from children with autism spectrum disorders, could allow caregivers and child psychologists to identify sleep disorders and other indicators of nighttime well-being that affect their quality of life and ability to learn. Unfortunately, traditional polysomnography is not well suited for children with autism spectrum disorder because they commonly have an aversion to unfamiliar objects – in this case, the numerous wires and electrodes required to perform a full polysomnograph. Therefore, an innovative, unobtrusive method for gathering relevant physiological data must be designed. This report discusses several methods for obtaining a ballistocardiogram (BCG), which is a representation of the ballistic forces created by the heart during the cardiac cycle. A ballistocardiograph design is implemented using an electromechanical film placed under the center of a bed sheet. While an individual sleeps on the bed, the circuitry attached to the film extract and amplify the BCG data, which are then streamed to a computer through a LabVIEW interface and stored in a text file. These data are analyzed with a MATLAB algorithm which uses autocorrelation and linear predictive coding in the time domain to sharpen the signal. Frequency-domain peaks are then extracted to determine average heart rate every ten seconds. Initial tests involved four participants (student members of the research team) who laid in four positions: on their back, stomach, right side, and left side, yielding 16 unique data sets. Each participant laid in at least one position that allowed for accurate tracking of heart rate, with seven of the 16 signals demonstrating heart rates with less than 2% error when compared to heart rates acquired with a commercial pulse oximeter. The stomach position appeared to offer the lowest total error, while lying on the right side offered the highest total error. Overall, heart rates acquired from this initial set of participants exhibited an average error of approximately 2.5% for all four positions.

Master of Science / Department of Electrical and Computer Engineering / William B. Kuhn and Balasubramaniam Natarajan / This thesis presents an energy harvesting wireless sensor network (EHWSN) architecture customized for use within a space suit. The contribution of this research spans both physical (PHY) layer energy harvesting transceiver design and appropriate medium access control (MAC) layer solutions. The EHWSN architecture consists of a star topology with two types of transceiver nodes: a powered Gateway Radio (GR) node and multiple energy harvesting (EH) Bio-Sensor Radio (BSR) nodes. A GR node works as a central controller to receive data from BSR nodes and manages the EHWSN via command packets; low power BSR nodes work to obtain biological signals, packetize the data and transmit it to the GR node. To demonstrate the feasibility of an EHWSN at the PHY layer, a representative BSR node is designed and implemented. The BSR node is powered by a thermal energy harvesting system (TEHS) which exploits the difference between the temperatures of a space suit's cooling garment and the astronaut's body. It is shown that through appropriate control of the duty-cycle in transmission and receiving modes, it is possible for the transceiver to operate with less than 1mW power generated by the TEHS. A super capacitor, energy storage of TEHS, acts as an energy buffer between TEHS and power consuming units (processing units and transceiver radio). The super capacitor charges when a BSR node is in sleep mode and discharges when the node is active. The node switches from sleep mode to active mode whenever the super capacitor is fully charged. A voltage level monitor detects the system's energy level by measuring voltage across the super capacitor. Since the power generated by the TEHS is extremely low(less than 1mW) and a BSR node consumes relatively high power (approximately 250mW) during active mode, a BSR node must work under an extremely low duty cycle (approximately 0.4%). This ultra-low duty cycle complicates MAC layer design because a BSR node must sleep for more than 99.6% of overall operation time. Another challenge for MAC layer design is the inability to predict when the BSR node awakens from sleep mode due to unpredictability of the harvested energy. Therefore, two feasible MAC layer designs, CSA (carrier sense ALOHA based)-MAC and GRI (gateway radio initialized)-MAC, are proposed in this thesis.

Master of Science / Department of Electrical and Computer Engineering / Steven Warren / Handgrip contractions are a useful exercise for assessing muscle fatigue in the forearm musculature. Most conventional hand-forearm ergometer systems require the researcher to manually guide subject activity, collect subject data, and assess subject fatigue after it has occurred. Since post-processing tools are not standardized for this type of experiment, researchers resort to building their own tools. This process can make comparing results between research groups difficult. This thesis presents updates to a hand-forearm ergometer system that automate the control, data-acquisition, and data-analysis mechanisms. The automated system utilizes a LabVIEW virtual instrument as the system centerpiece; it provides the subject/researcher interfaces and coordinates data acquisition from both traditional and new sensors. The system also processes the hand-forearm data within the LabVIEW environment as the data are collected. This allows the researcher to better understand the onset of subject fatigue while an experiment is in progress. System upgrades relative to prior work include the addition of new parameters to the researcher display, a change in the subject display from a binary up-down display to a sliding bar for better control over subject grip state, and a software update from a simple data acquisition and display system to a real-time processing system. The toolset has proven to be a viable support resource for experimental studies performed in the Kansas State University Human Exercise Physiology Laboratory that target muscle fatigue in human forearms. Initial data acquired during these tests indicate the viability of the system to acquire consistent and physiologically meaningful data while providing a useable toolset for follow-on data analyses.

Master of Science / Department of Electrical and Computer Engineering / Punit Prakash / Thermal therapies employing interstitial microwave applicators for hyperthermia or ablation are in clinical use for treatment of cancer and benign disease in various organs. However, treatment of targets in proximity to critical structures with currently available devices is risky due to unfocused deposition of energy into tissue. For successful treatment, complete thermal coverage of the tumor and margin of surrounding healthy tissue must be achieved, while precluding damage to critical structures. This thesis investigates two approaches to increase precision of microwave thermal therapy. Chapter 2 investigates a novel coaxial antenna design for microwave ablation (MWA) employing a hemi-cylinderical reflector to achieve a directional heating pattern. A proof of concept antenna with an S₁₁ of -29 dB at 2.45 GHz was used in ex vivo experiments to characterize the antennas’ heating pattern with varying input power and geometry of the reflector. Ablation zones up to 20 mm radially were observed in the forward direction, with minimal heating (less than 4 mm) behind the reflector. Chapter 3 investigates the use of magnetic nanoparticles (MNP) of varying size and geometry for enhancing microwave tissue heating. A conventional dipole, operating at 2.45 GHz and radiating 15 W, was inserted into a 20 mm radius sphere of distributed MNPs and heating measurements were taken 5 mm, 10 mm, and 15 mm radially away. A heating rate of 0.08°C/s was observed at 10 mm, an increase of 2-4 times that of the control measurement. These approaches provide strong potential for improving spatial control of tissue heating with interstitial and catheter-based microwave antennas.