Electrical and Computer Engineering Commons^™

Linking Lignin Source With Structural And Electrochemical Properties Of Lignin-Derived Carbon Materials, Wenqi Li, Yan Zhang, Lalitendu Das, Yikai Wang, Mi Li, Namal Wanninayake, Yunqiao Pu, Doo Young Kim, Yang-Tse Cheng, Arthur J. Ragauskas, Jian Shi

Biosystems and Agricultural Engineering Faculty Publications

Valorization of lignin to high-value chemicals and products along with biofuel production is generally acknowledged as a technology platform that could significantly improve the economic viability of biorefinery operations. With a growing demand for electrical energy storage materials, lignin-derived activated carbon (AC) materials have received increasing attention in recent years. However, there is an apparent gap in our understanding of the impact of the lignin precursors (i.e., lignin structure, composition and inter-unit linkages) on the structural and electrochemical properties of the derived ACs. In the present study, lignin-derived ACs were prepared under identical conditions from two different lignin …

Cfd Modeling On Hydrodynamic Characteristics Of Multiphase Counter-Current Flow In A Structured Packed Bed For Post-Combustion Co2 Capture, Li Yang, Fang Liu, Kozo Saito, Kunlei Liu

Mechanical Engineering Faculty Publications

Solvent-based post combustion CO₂ capture is a promising technology for industrial application. Gas-liquid interfaces and interactions in the packed bed are considered one of the key factors affecting the overall CO₂ absorption rate. Understanding the hydrodynamic characterizations within packed beds is essential to identify the appropriate enhanced mass transfer technique. However, multiphase counter-current flows in the structured packing typically used in these processes are complicated to visualize and optimize experimentally. In this paper, we aim to develop a comprehensive 3D multiphase, counter-current flow model to study the liquid/gas behavior on the surface of structured packing. The output from …

Optimal Design Of A Switched Reluctance Motor With Magnetically Disconnected Rotor Modules Using A Design Of Experiments Differential Evolution Fea-Based Method, Vandana Rallabandi, Jie Wu, Ping Zhou, David G. Dorrell, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Switched reluctance (SR) machines are attractive because they present relatively high efficiency and torque density in spite of lacking permanent magnets. This paper focuses on a two-objective optimization of an external rotor SR motor with a stator that has concentrated coils and a rotor with magnetically isolated modules. The objectives are minimum loss and mass, and 11 independent dimensionless geometric variables are considered as inputs that affect them. A combined design of experiments (DOE) and differential evolution (DE) approach is proposed. The DOE methodology is used to reduce the search space by eliminating from consideration input variable values, leading to …

Two-Level Surrogate-Assisted Differential Evolution Multi-Objective Optimization Of Electric Machines Using 3-D Fea, Narges Taran, Dan M. Ionel, David G. Dorrell

Power and Energy Institute of Kentucky Faculty Publications

A two-level surrogate-assisted optimization algorithm is proposed for electric machine design using 3-D finite-element analysis (FEA). The algorithm achieves the optima with much fewer FEA evaluations than conventional methods. It is composed of interior and exterior levels. The exploration is performed mainly in the interior level, which evaluates hundreds of designs employing affordable kriging models. Then, the most promising designs are evaluated in the exterior loop with expensive 3-D FEA models. The sample pool is constructed in a self-adjustable and dynamic way. A hybrid stopping criterion is used to avoid unnecessary expensive function evaluations.

An Accurate And Efficient Time Delay Estimation Method Of Ultra-High Frequency Signals For Partial Discharge Localization In Substations, Pengfei Li, Kejie Dai, Tong Zhang, Yantao Jin, Yushun Liu, Yuan Liao

Electrical and Computer Engineering Faculty Publications

Partial discharge (PD) localization in substations based on the ultra-high frequency (UHF) method can be used to efficiently assess insulation conditions. Localization accuracy is affected by the accuracy of the time delay (TD) estimation, which is critical for PD localization in substations. A review of existing TD estimation methods indicates that there is a need to develop methods that are both accurate and computationally efficient. In this paper, a novel TD estimation method is proposed to improve both accuracy and efficiency. The TD is calculated using an improved cross-correlation algorithm based on full-wavefronts of array UHF signals, which are extracted …

Simulation Studies For A Multi-Mw Hybrid Wind-Solar Pv System For Desalination Plants, Vandana Rallabandi, Nasser Alawhali, Oluwaseun M. Akeyo, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

This paper presents a power system configuration and control schemes for a Multi-MW wind-solar hybrid system, which includes multiple wind turbines and solar panels to support a desalination plant. The wind and solar systems are sized such that the desalination plant obtains, as far as possible, its power from the renewable sources, to minimize the dependence on the utility grid. Each section of the wind turbine system includes a variable speed permanent magnet synchronous generator connected to the grid via a back-to-back voltage source converter. The rectifier operates the wind system at the maximum power point, and the inverter provides …

Real Time Operation Of Smart Homes With Pv And Battery Systems Under Variable Electricity Rate Schedules And Transactive Power Flow, Huangjie Gong, Oluwaseun M. Akeyo, Vandana Rallabandi, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

According to some utility schedules, the electricity rate is variable such that homes may be encouraged to buy and store power in a battery when it is inexpensive, and self-consume or sell to the grid during other times. Power arbitrage through a battery energy storage (BES), can help maintain consumer comfort and minimize residential electricity bills. This paper reports the calculated daily energy costs incurred by different types of homes for a given utility electricity rate schedule. The homes exchange power among each other behind a section of the distribution network. A free market system is formed and the electricity …

Power Utility Tests For Multi-Mw High Energy Batteries, Oluwaseun M. Akeyo, Huangjie Gong, Vandana Rallabandi, Nicholas Jewell, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

This paper reviews the procedures, layouts and metrics described in the new test manual issued by the Electric Power Research Institute (EPRI), in order to determine the performance and functionality of a utility scale battery energy storage system (BESS). In this approach, the large battery unit is connected to the dc-link of a bidirectional power conversion system (PCS), which may be interfaced with either the utility grid or a load bank for the purpose of estimating the BESS operation and performance characteristics, some of which includes; available charge/discharge energy at rated power, continuous charge/discharge duration, battery ramp rate, and ac …

Transistor-Clamped Multilevel H-Bridge Inverter In Si And Sic Hybrid Configuration For High-Efficiency Photovoltaic Applications, Yibin Zhang, Jiangbiao He, Sanjeevikumar Padmanaban, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Using wide bandgap (WBG) devices has been a promising solution to improve the efficiency of power inverters for photovoltaic (PV) applications. However, for multilevel inverters, using WBG devices to improve the inverter efficiency can increase the system cost dramatically due to the high price of WBG devices in the present market as well as the large number of power devices typically required in multilevel inverter topologies. In this paper, a five-level transistor clamped H-bridge (TCHB) inverter will be further investigated. This inverter requires much lower number of semiconductor switches and fewer isolated dc sources than the conventional cascaded H-bridge inverter. …

Torque Production Capability Of Axial Flux Machines With Single And Double Rotor Configurations, Narges Taran, Greg Heins, Vandana Rallabandi, Dean Patterson, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Axial flux PM (AFPM) machines are used particularly in applications requiring a compact structure. Their disc shape topology and axial air-gap have lead to a variety of configurations including two popular ones: the yokeless and segmented armature (YASA), and the single-stator single-rotor or single sided machine. In this study, a comprehensive comparative analysis of these configurations is conducted at different magnetic and electric loadings. It is found that at lower loadings, typically employed for air-cooled machines, the torque/ampere characteristics of the YASA machine are almost identical to those of a single sided machine constructed with half the magnet volume. On …

Improving The Capacity Factor And Stability Of Multi-Mw Grid Connected Pv Systems With Results From A 1mw/2mwh Battery Demonstrator, Oluwaseun M. Akeyo, Vandana Rallabandi, Nicholas Jewell, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Conventional PV systems integrated with a battery connect the array and the energy storage unit to a dc-link through individual dc-dc converters for maximum power point tracking (MPPT) and battery charge control. This paper proposes a new system configuration, which connects the PV array and battery unit to the dc-link of the system inverter via a single dc-dc converter capable of simultaneously operating as a charge controller and MPPT device. This dc-dc converter is controlled such that it charges/discharges the battery with the amount of power required to maintain the PV array at its MPPT reference voltage. The proposed system …

Exploring The Efficiency And Cost Limits Of Fractional Hp Axial Flux Pm Machine Designs, Narges Taran, Vandana Rallabandi, Greg Heins, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Optimizing the design of electric machines is a vital step in ensuring the economical use of active materials. The three-dimensional flux paths in axial flux PM (AFPM) machines necessitate the use of computationally expensive 3D electromagnetic analysis. Furthermore, a large number of design evaluations is required to find the optimum, causing the total computation time to be excessively long. In view of this, a two-level surrogate assisted algorithm capable of handling such expensive optimization problems is introduced, which substantially reduces the number of FEA evaluations. The proposed algorithm is employed to optimally design an AFPM machine within a specified envelope, …

Net Zero Energy Houses With Dispatchable Solar Pv Power Supported By Electric Water Heater And Battery Energy Storage, Huangjie Gong, Vandana Rallabandi, Dan M. Ionel, Donald G. Colliver, Shaun Duerr, Cristinel Ababei

Power and Energy Institute of Kentucky Faculty Publications

Over a year, net zero energy (NZE) houses produce and feed zero net metered electrical energy to the grid. Technical challenges, notably the `duck curve' arise due to the fact that peak solar generation and load demand are seldom coincident. Common approaches to mitigate this limitation include the curtailment of solar power, and the use of storage. Surplus solar energy may be stored in a battery, which can subsequently be discharged to supply the home electricity needs when demand is in excess. In addition to batteries, less expensive electric water heaters, which are ubiquitous, can be modified as energy storage …

Hybrid Pv-Wind, Micro-Grid Development Using Quasi-Z-Source Inverter Modeling And Control—Experimental Investigation, Neeraj Priyadarshi, Sanjeevikumar Padmanaban, Dan M. Ionel, Lucian Mihet-Popa, Farooque Azam

Power and Energy Institute of Kentucky Faculty Publications

This research work deals with the modeling and control of a hybrid photovoltaic (PV)-Wind micro-grid using Quasi Z-source inverter (QZsi). This inverter has major benefits as it provides better buck/boost characteristics, can regulate the phase angle output, has less harmonic contents, does not require the filter and has high power performance characteristics over the conventional inverter. A single ended primary inductance converter (SEPIC) module used as DC-DC switched power apparatus is employed for maximum power point tracking (MPPT) functions which provide high voltage gain throughout the process. Moreover, a modified power ratio variable step (MPRVS) based perturb & observe (P&O) …

Coreless And Conventional Axial Flux Permanent Magnet Motors For Solar Cars, Narges Taran, Vandana Rallabandi, Greg Heins, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Axial flux permanent magnet (AFPM) motors are suitable options for solar-powered vehicles due to their compact structure and high torque density. Furthermore, certain types of AFPM machines may be configured without stator cores, which eliminates associated losses and cogging torque and simplifies the manufacturing and assembly. This paper examines two machine designs for use in the solar-powered vehicle of the challenger class-a single rotor, single stator conventional AFPM machine, and a coreless AFPM machine with multiple stator and rotor disks. The response surface methodology (RSM) is utilized for the systematic comparison of the conventional and coreless topologies and to select …

Power Electronics Powertrain Architectures For Hybrid And Solar Electric Airplanes With Distributed Propulsion, Damien Lawhorn, Vandana Rallabandi, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

Distributed propulsion in aircraft has been shown to increase reliability and benefit aerodynamic performance. This paper discusses power electronic architectures and proposes control schemes suitable for distributed propulsion in hybrid and electric airplanes. Hybrid electric airplanes include permanent magnet synchronous generators driven by jet engines. The output of the generators is connected to the propulsion motors through back to back voltage source converters. Batteries, connected to the DC bus through buck-boost converters, are used to provide additional power to the propulsion motors during take off and climb. In the case of electric airplanes, the jet engine-permanent magnet generator system is …

Multi-Physics Modeling For Electric And Hybrid Vehicles With In-Wheel Electric Motors, Vandana Rallabandi, Damien Lawhorn, Dan M. Ionel, Xiao Li

Power and Energy Institute of Kentucky Faculty Publications

This paper discusses multi-domain and multi-physics modeling of in-wheel electric vehicles using ANSYS Simplorer and ANSYS Maxwell. The study includes component level modeling of the vehicle, brakes, wheels, battery, traction motor, inverter, solar panels and boost converter. The traction motor used is an axial flux permanent magnet synchronous machine. In order to accommodate both the large time constants of the mechanical system and the high switching frequency power electronics, average models of the inverter and boost converter are considered. Simulation examples are provided for the University of Kentucky Gato Del Sol V car.

A Comparative Study Of Constant Power Operation Techniques For Low Inductance Machines, Damien Lawhorn, Narges Taran, Vandana Rallabandi, Dan M. Ionel

Power and Energy Institute of Kentucky Faculty Publications

In traditional electric machines, it is usually possible to achieve constant power high-speed operation by employing field weakening through the injection of a negative d-axis current component. However, in machines with low armature inductance, such as high power density permanent magnet synchronous machines, and more specifically, coreless machines, which are gaining increasing attention because of their high specific torque, the extended speed range obtained using this method is very narrow. This paper summarizes the performance characteristics of existing approaches for obtaining constant power operation and proposes two new techniques, specially applicable to coreless axial flux permanent magnet machine namely, current …

Performance Evaluation Of Energy-Autonomous Sensors Using Power-Harvesting Beacons For Environmental Monitoring In Internet Of Things (Iot), George Dan Moiş, Teodora Sanislav, Silviu Corneliu Folea, Sherali Zeadally

Information Science Faculty Publications

Environmental conditions and air quality monitoring have become crucial today due to the undeniable changes of the climate and accelerated urbanization. To efficiently monitor environmental parameters such as temperature, humidity, and the levels of pollutants, such as fine particulate matter (PM2.5) and volatile organic compounds (VOCs) in the air, and to collect data covering vast geographical areas, the development of cheap energy-autonomous sensors for large scale deployment and fine-grained data acquisition is required. Rapid advances in electronics and communication technologies along with the emergence of paradigms such as Cyber-Physical Systems (CPSs) and the Internet of Things (IoT) have led to …

Fault Identification And Location For Distribution Network With Distributed Generations, Wen Fan, Yuan Liao

Electrical and Computer Engineering Faculty Publications

Power distribution networks with distributed generations may experience faults. It is essential to promptly locate the fault for fast repair and restoration. This paper presents a novel method for identifying the faulted section and accurate location of faults that occur on power distribution grid. Appropriate matrices are set up to represent meter locations on the grid and the topology of the grid. The voltage and current measurements obtained are utilized to decide the fault sections. Then fault location is determined by solving equations that link measurements and fault locations through bus impedance matrix. The method is applicable to both single …

The 3d Stress-Tensor Bootstrap, Anatoly Dymarsky, Filip Kos, Petr Kravchuk, David Poland, David Simmons-Duffin

Physics and Astronomy Faculty Publications

We study the conformal bootstrap for 4-point functions of stress tensors in parity-preserving 3d CFTs. To set up the bootstrap equations, we analyze the constraints of conformal symmetry, permutation symmetry, and conservation on the stress-tensor 4-point function and identify a non-redundant set of crossing equations. Studying these equations numerically using semidefinite optimization, we compute bounds on the central charge as a function of the independent coefficient in the stress-tensor 3-point function. With no additional assumptions, these bounds numerically reproduce the conformal collider bounds and give a general lower bound on the central charge. We also study the effect of gaps …

Three Dimensional View Of Arbitrary Q Syk Models, Sumit R. Das, Aminik Ghosh, Antal Jevicki, Kenta Suzuki

Physics and Astronomy Faculty Publications

In [15] it was shown that the spectrum and bilocal propagator of SYK model with four fermion interactions can be realized as a three dimensional model in AdS₂ ×S¹/Z₂ with nontrivial boundary conditions in the additional dimension. In this paper we show that a similar picture holds for generalizations of the SYK model with q-fermion interactions. The 3D realization is now given on a space whose metric is conformal to AdS₂ × S¹/Z₂ and is subject to a non-trivial potential in addition to a delta function at the center of …

Preventing Crossover In Redox Flow Batteries Through Active Material Oligomerization, Susan A. Odom

Chemistry Faculty Publications

No abstract provided.

Universality Of Fast Quenches From The Conformal Perturbation Theory, Anatoly Dymarsky, Michael Smolkin

Physics and Astronomy Faculty Publications

We consider global quantum quenches, a protocol when a continuous field theoretic system in the ground state is driven by a homogeneous time-dependent external interaction. When the typical inverse time scale of the interaction is much larger than all relevant scales except for the UV-cutoff the system’s response exhibits universal scaling behavior. We provide both qualitative and quantitative explanations of this universality and argue that physics of the response during and shortly after the quench is governed by the conformal perturbation theory around the UV fixed point. We proceed to calculate the response of one and two-point correlation functions confirming …

Accurate Location Of Evolving Faults On Transmission Lines Using Sparse Wide Area Measurements, Xiangqing Jiao, Yuan Liao

Electrical and Computer Engineering Faculty Publications

In electric power systems, not all fault conditions remain unchanged during faults. An evolving fault has one characteristic initially and changes to a different condition subsequently. Locating evolving faults is challenging due to the change in fault type shortly after the fault initiation. This paper presents a new approach for estimating the locations of evolving faults on transmission lines. By using sparse wide area voltage measurements, this method is able to accurately locate evolving faults without requiring measurements from either end of the faulted line. There is no need to detect whether a fault is an evolving fault or not. …

Contributions To Hybrid Power Systems Incorporating Renewables For Desalination Systems, Nasser Alawhali

Theses and Dissertations--Electrical and Computer Engineering

Renewable energy is one of the most reliable resource that can be used to generate the electricity. It is expected to be the most highly used resource for electricity generation in many countries in the world in the next few decades. Renewable energy resources can be used in several purposes. It can be used for electricity generation, water desalination and mining. Using renewable resources to desalinate the water has several advantages such as reduce the emission, save money and improve the public health. The research described in the thesis focuses on the analysis of using the renewable resources such as …

Advanced Synchronous Machine Modeling, Yuqi Zhang

Theses and Dissertations--Electrical and Computer Engineering

The synchronous machine is one of the critical components of electric power systems. Modeling of synchronous machines is essential for power systems analyses. Electric machines are often interfaced with power electronic components. This work presents an advanced synchronous machine modeling, which emphasis on the modeling and simulation of systems that contain a mixture of synchronous machines and power electronic components. Such systems can be found in electric drive systems, dc power systems, renewable energy, and conventional synchronous machine excitation. Numerous models and formulations have been used to study synchronous machines in different applications. Herein, a unified derivation of the various …

Stability Analysis And Design Of A Tracking Filter For Variable Frequency Applications, Pranav Aramane

Theses and Dissertations--Electrical and Computer Engineering

The work presented in this thesis is a frequency adaptive tracking filter that can be used in exact tracking of power frequencies and rejection of unwanted harmonics introduced during power disturbances. The power synchronization process includes power converters and other equipment that have many non-linear components that introduce unwanted harmonics. This new design is motivated by the requirement of a filter that can filter all the harmonics and exactly track a rapidly varying fundamental frequency with little time delay and phase error. This thesis analyzes the proposed filter mathematically based on Lyapunov theory and simulations are presented to show the …

A Fault Location Algorithm For Unbalanced Distribution System Without Fault Type Information, Yizhe Li

Theses and Dissertations--Electrical and Computer Engineering

Power system faults normally result in system damage, profit loss and consumer dissatisfaction. Consequently, there is a strong demand on precise and fast fault location estimation for power system to minimize the system restoration time.

This paper examines a method to locate short-circuit faults on a distribution system with unbalanced loads without fault type information. Bus impedance matrix technique was harnessed in the fault location estimation algorithm. The system data including line impedances, source impedance and distribution system layout was assumed to be known factors, hence pre-fault bus impedance can be calculated and implemented into the algorithm. Corresponding methods to …

Distribution System Optimization With Integrated Distributed Generation, Sarmad Khaleel Ibrahim

Theses and Dissertations--Electrical and Computer Engineering

In this dissertation, several volt-var optimization methods have been proposed to improve the expected performance of the distribution system using distributed renewable energy sources and conventional volt-var control equipment: photovoltaic inverter reactive power control for chance-constrained distribution system performance optimisation, integrated distribution system optimization using a chance-constrained formulation, integrated control of distribution system equipment and distributed generation inverters, and coordination of PV inverters and voltage regulators considering generation correlation and voltage quality constraints for loss minimization. Distributed generation sources (DGs) have important benefits, including the use of renewable resources, increased customer participation, and decreased losses. However, as the penetration level …