ASU Electronic Theses and Dissertations

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Date Range
2010 2017

Many methods have been proposed to estimate power system small signal stability, for either analysis or control, through identification of modal frequencies and their damping levels. Generally, estimation methods have been employed to assess small signal stability from collected field measurements. However, the challenge to using these methods in assessing field measurements is their ability to accurately estimate stability in the presence of noise. In this thesis a new method is developed which estimates the modal content of simulated and actual field measurements using orthogonal polynomials and the results are compared to other commonly used estimators. This new method estimates ...

Contributors
Kokanos, Barrie Lee, Karady, George G, Heydt, Gerald, et al.
Created Date
2010

Market acceptability of distributed energy resource (DER) technologies and the gradual and consistent increase in their depth of penetration have generated significant interest over the past few years. In particular, in Arizona and several other states there has been a substantial in-crease in distributed photovoltaic (PV) generation interfaced to the power distribution systems, and is expected to continue to grow at a significant rate. This has made integration, control and optimal operation of DER units a main area of focus in the design and operation of distribution systems. Grid-connected, distributed PV covers a wide range of power levels ranging from ...

Contributors
Narayanan, Anand, Ayyanar, Raja, Vittal, Vijay, et al.
Created Date
2010

An advantage of doubly fed induction generators (DFIGs) as compared to conventional fixed speed wind turbine generators is higher efficiency. This higher efficiency is achieved due to the ability of the DFIG to operate near its optimal turbine efficiency over a wider range of wind speeds through variable speed operation. This is achieved through the application of a back-to-back converter that tightly controls the rotor current and allows for asynchronous operation. In doing so, however, the power electronic converter effectively decouples the inertia of the turbine from the system. Hence, with the increase in penetration of DFIG based wind farms, ...

Contributors
Gautam, Durga, Vittal, Vijay, Heydt, Gerald, et al.
Created Date
2010

The constant scaling of supply voltages in state-of-the-art CMOS processes has led to severe limitations for many analog circuit applications. Some CMOS processes have addressed this issue by adding high voltage MOSFETs to their process. Although it can be a completely viable solution, it usually requires a changing of the process flow or adding additional steps, which in turn, leads to an increase in fabrication costs. Si-MESFETs (silicon-metal-semiconductor-field-effect-transistors) from Arizona State University (ASU) on the other hand, have an inherent high voltage capability and can be added to any silicon-on-insulator (SOI) or silicon-on-sapphire (SOS) CMOS process free of cost. This ...

Contributors
Lepkowski, William, Thornton, Trevor, Bakkaloglu, Bertan, et al.
Created Date
2010

Optical Instrument Transformers (OIT) have been developed as an alternative to traditional instrument transformers (IT). The question "Can optical instrument transformers substitute for the traditional transformers?" is the main motivation of this study. Finding the answer for this question and developing complete models are the contributions of this work. Dedicated test facilities are developed so that the steady state and transient performances of analog outputs of a magnetic current transformer (CT) and a magnetic voltage transformer (VT) are compared with that of an optical current transformer (OCT) and an optical voltage transformer (OVT) respectively. Frequency response characteristics of OIT outputs ...

Contributors
Kucuksari, Sadik, Karady, George G, Heydt, Gerald T, et al.
Created Date
2010

Recent changes in the energy markets structure combined with the conti-nuous load growth have caused power systems to be operated under more stressed conditions. In addition, the nature of power systems has also grown more complex and dynamic because of the increasing use of long inter-area tie-lines and the high motor loads especially those comprised mainly of residential single phase A/C motors. Therefore, delayed voltage recovery, fast voltage collapse and short term voltage stability issues in general have obtained significant importance in relia-bility studies. Shunt VAr injection has been used as a countermeasure for voltage instability. However, the dynamic and ...

Contributors
Salloum, Ahmed, Vittal, Vijay, Heydt, Gerald, et al.
Created Date
2011

The development of a Solid State Transformer (SST) that incorporates a DC-DC multiport converter to integrate both photovoltaic (PV) power generation and battery energy storage is presented in this dissertation. The DC-DC stage is based on a quad-active-bridge (QAB) converter which not only provides isolation for the load, but also for the PV and storage. The AC-DC stage is implemented with a pulse-width-modulated (PWM) single phase rectifier. A unified gyrator-based average model is developed for a general multi-active-bridge (MAB) converter controlled through phase-shift modulation (PSM). Expressions to determine the power rating of the MAB ports are also derived. The developed ...

Contributors
Falcones, Sixifo Daniel, Ayyanar, Raja, Karady, George, et al.
Created Date
2011

Dynamic loading is the term used for one way of optimally loading a transformer. Dynamic loading means the utility takes into account the thermal time constant of the transformer along with the cooling mode transitions, loading profile and ambient temperature when determining the time-varying loading capability of a transformer. Knowing the maximum dynamic loading rating can increase utilization of the transformer while not reducing life-expectancy, delaying the replacement of the transformer. This document presents the progress on the transformer dynamic loading project sponsored by Salt River Project (SRP). A software application which performs dynamic loading for substation distribution transformers with ...

Contributors
Liu, Yi, Tylavksy, Daniel J, Karady, George G, et al.
Created Date
2011

The high penetration of photovoltaic (PV) both at the utility and at the distribu-tion levels, has raised concerns about the reliability of grid-tied inverters of PV power systems. Inverters are generally considered as the weak link in PV power systems. The lack of a dedicated qualification/reliability standard for PV inverters is a main barrier in realizing higher level of confidence in reliability. Development of a well-accepted design qualification standard specifically for PV inverters will help pave the way for significant improvement in reliability and performance of inverters across the entire industry. The existing standards for PV inverters such as UL ...

Contributors
Alampoondi Venkataramanan, Sai Balasubramanian, Ayyanar, Raja, Vittal, Vijay, et al.
Created Date
2011

All-dielectric self-supporting (ADSS) fiber optic cables are used for data transfer by the utilities. They are installed along high voltage transmission lines. Dry band arcing, a phenomenon which is observed in outdoor insulators, is also observed in ADSS cables. The heat developed during dry band arcing damages the ADSS cables' outer sheath. A method is presented here to rate the cable sheath using the power developed during dry band arcing. Because of the small diameter of ADSS cables, mechanical vibration is induced in ADSS cable. In order to avoid damage, vibration dampers known as spiral vibration dampers (SVD) are used ...

Contributors
Prabakar, Kumaraguru, Karady, George G, Vittal, Vijay, et al.
Created Date
2011

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries.

For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.