Dynamic Analysis of a Microgrid Powered With an Inverter and Machine-Based Distributed Resources

The proliferation of renewable distributed energy resources, particularly photovoltaic (PV) power systems, and the increasing need for a reliable power supply has led to the concept of microgrids, a mini-grid that consists of locally connected power generation units and needs, able to operate connected or disconnected from the utility grid, using controlled and coordinated methods to provide for the users of the microgrid the best possible conditions for their needs. The main technical issues facing microgrids include some of the following, seamless transition from stand-alone to utility grid connected operation, how to preserve frequency and voltage stability, and provide the lowest cost power among numerous power resources. Technologies that will be used in the future smart grid will be built, tested, and fielded in modern microgrids with many national laboratories, utility companies, and universities using microgrids of all different types for research and development. This dissertation describes the design, fabrication, and testing of a microgrid facility which comprises adjustable resistive and inductive loads, a diesel-powered generator (DG), an advanced inverter PV system, a battery energy storage system (BESS), monitoring, protection, and control devices. The microgrid facility was built with the foresight that it would be used for conducting tests and experiments related to microgrid technical challenges, thus ease of access and expandability were built in which allows it to be used for both research and education purposes. Numerous experimental tests conducted include the following: (a) the dynamic response of a DG to load changes, (b) an advanced PV inverters autonomous functions, (c) advanced inverter islanding test, (d) load sharing among the DG and PV system, (e) PV and battery storage systems load sharing, (d) dynamic performance of an advanced PV inverter and a DG during unintentional islanding under different power export/import conditions, and (e) BESS iv response to utility outage under different PV operating conditions. Attempts to improve reliability and power quality are made by expanding the PV inverter ride-through times during frequency and voltage abnormalities. An economic analysis in terms of Net Present Value (NPV) is conducted on a residential application where a BESS is paired with a PV system to shift solar energy in favor Time-of-Use (ToU) pricing and to provide ancillary grid services

Status of the nevada Shocker At the University of nevada, Las Vegas

The Nevada shocker is a 540 kV, 7 /spl Omega/, 50 ns pulsed power device based on Marx bank and Blumlein technologies. The Marx bank is composed of nine 60 kV capacitors charged in series with a gamma high voltage source connected by means of Ross relays in an air environment. A trigatron switch energized with an isolated mini capacitor bank is used to erect the Marx bank. The trigatron switch and erecting electrodes are contained in a gas manifold pressurized to 20 /spl plusmn/ 1 psi with dry air. The energy is released sequentially through an inductor and a water filled charging transmission line to the Blumlein immersed in deionized water. The Blumlein shapes and compresses the energy into a 50 ns pulse upon discharge. A self-breaking water switch initiates the release of energy in the Blumlein. The energy flows through a water filled discharging transmission line to the diode end of the Nevada Shocker. The current diode end of the Blumlein supports vacuum pressures as low as 6.5 /spl times/ 10/sup -6/ Torr. The chamber is pumped with the aid of a roughing pump and a cryogenic vacuum pump. The vacuum section of the Nevada Shocker is currently being rebuilt to incorporate mechanical and thermal loading capabilities with sensors located at the experiment. A number of diagnostic developments are currently underway to support flashover studies on plastics. Resistive probe and differential B-dot diagnostics with the aid of a 6 GHz 20 GS/s TDS 6604 real time scope is documented demonstrating the capability of the machine

Slavery's Legalism: Lawyers and the Commercial Routine of Slavery

Eugenius Aristides Nisbet played a critical role in Georgia's secession from the United States. Elected as a delegate to Georgia's 1861 secession convention, Nisbet introduced a resolution in favor of severing ties with the Union, and he led the committee that drafted his state's secession ordinance. Nisbet was a trained lawyer who had served on the Georgia Supreme Court, and his legal training shaped the way that he viewed secession. He believed that the Constitution did not give states the right to dissolve the Union; instead, this power rested solely in the people, and he framed the resolution and ordinance accordingly. Thanks in part to Nisbet, it was the "people of the State of Georgia" who "repealed, rescinded and abrogated" their ratification of the Constitution in 1788.

Exopolysaccharide Microchannels Direct Bacterial Motility and Organize Multicellular Behavior

The myxobacteria are a family of soil bacteria that form biofilms of complex architecture, aligned multilayered swarms or fruiting body structures that are simple or branched aggregates containing myxospores. Here, we examined the structural role of matrix exopolysaccharide (EPS) in the organization of these surface-dwelling bacterial cells. Using time-lapse light and fluorescence microscopy, as well as transmission electron microscopy and focused ion beam/scanning electron microscopy (FIB/SEM) electron microscopy, we found that Myxococcus xanthus cell organization in biofilms is dependent on the formation of EPS microchannels. Cells are highly organized within the three-dimensional structure of EPS microchannels that are required for cell alignment and advancement on surfaces. Mutants lacking EPS showed a lack of cell orientation and poor colony migration. Purified, cell-free EPS retains a channel-like structure, and can complement EPS- mutant motility defects. In addition, EPS provides the cooperative structure for fruiting body formation in both the simple mounds of M. xanthus and the complex, tree-like structures of Chondromyces crocatus. We furthermore investigated the possibility that EPS impacts community structure as a shared resource facilitating cooperative migration among closely related isolates of M. xanthus