Doctor of Philosophy, The Ohio State University, 2017, Electrical and Computer Engineering

The advent of microgrids has shifted the focus from centralized power generation to a more distributed manner, involving a mix of different distributed energy resources (DERs). Reciprocating engine driven synchronous generators (referred as gensets) are a common DER used for distributed generation. One of the key concerns with such power networks is the aspect of frequency regulation under large disturbances, especially in an islanded mode of operation, without the support of the utility grid. This works looks at possible solution methods for mitigating large frequency disturbances in an islanded microgrid. Due to steep load changes, the gensets undergo large frequency swings and can be even vulnerable to stalling. The benefits of smart loads are analyzed in this work to prevent such occurrence by temporarily reducing the transient overload on gensets. Another solution to mitigate large frequency deviation is the integration of energy storage system (ESS), but the effectiveness depends on its operation as a grid-forming or a grid-following unit. Important metrics such as frequency nadir during load changes in the islanded microgrid are computed to show the usefulness of ESS in islanded microgrids. For this purpose, analytical methods using reduced-order models are developed and found to provide accurate estimates of frequency deviations under power system disturbances. Generally, ESS units are interfaced with an inverter and when operated in grid-forming mode can offer desired dynamic frequency behavior in an islanded microgrid. Similarly, other inverter-based DERs can also provide good frequency regulation as they share the larger portion of the transient overload compared to gensets. However, under certain scenarios the inverter-based DERs are found to collapse due to this large transient loading and can bring down the whole microgrid system as a result. A better coordination between the different DERs in a mixed source microgrid is facilitated in this work to gua (open full item for complete abstract)

Committee: Mahesh Illindala (Advisor); Jin Wang (Committee Member); Jiankang Wang (Committee Member); Alexander Lindsey (Committee Member) Subjects: Electrical Engineering

Master of Science (MS), Ohio University, 1997, Mechanical Engineering (Engineering)

Novel design and optimization of vehicle's natural gas fuel tank

Committee: Bhavin Mehta (Advisor) Subjects: Engineering, Mechanical

Master of Science (MS), Ohio University, 2004, Mechanical Engineering (Engineering)

There is a great deal of attention being concentrated on reducing the weight of pressure vessels and fuel/oxidizer tanks (tankage) by 10% to 20%. Most efforts are focused at the use of new lighter weight high strength materials to achieve this goal. This author proposes another approach called Hydrostatic Pressure Retainment™ (HPR™) which has the potential of reducing tank weights by nearly 40% while simultaneously increasing safety and design versatility. HPR™ is an original invention of the author and his advisor, and represents a truly novel approach to light weight pressure vessel design. Described herein are the initial steps towards development of this new technology.

Committee: Bhavin Mehta (Advisor) Subjects: Engineering, Mechanical