This thesis presents the applications of a series interconnection scheme for small distributed generation (DG) systems in distribution networks. The concept uses one set of voltage source converter (VSC) to control the injected voltage magnitude and phase angle for power injection and voltage sag mitigation. Through an energy storage device and the VSC, DG outputs vary concurrently with the line loading and provide load leveling functions. Under voltage sag situations, it provides missing voltages to effectively deal with power quality problems. Due to its series connection characteristic, it is convenient in preventing islanding operation and good for fault current limiting. The concept is suitable for locations where the voltage phase shift is not a major concern. Due to the use of only one set of converter, it is economic for customer site distributed energy resource applications and its control strategy would depend on the types of load connected.

Transient Recovery Voltage (TRV) is an important consideration in the selection and installation of circuit breakers with appropriate ratings. Capacitor banks with inrush current limiting reactors are an integral part of the power system. Capacitor banks with inrush reactors on the load side terminal of the capacitor breaker alter the TRV seen across the breaker and it is critical to carry out the TRV analysis to prevent circuit breaker failure. TRV analysis has been performed for various capacitor bank - inrush reactor configurations, with the fault occurring at different terminals on the load side. Analytical solutions have been presented for both single-phase and three-phase ungrounded capacitor banks. Neutral displacement voltage of three-phase ungrounded capacitor banks result in increased stress across the breaker. Results have been validated with PSCAD simulation and MATLAB plots. / text

No description available.

[pt] Esta tese apresenta os principais fenômenos eletromecânicos, que ocorrem durante a operação do forno a arco, com ênfase especial nos fenômenos elétricos e magnéticos envolvidos. Apresenta também uma simulação computacional, que tem por objetivo verificar que a utilização de um reator série limitador de corrente no circuito de alimentação do forno, visando estabilizar o arco, não reduz significativamente a potência operacional do mesmo à 60Hz. A tese apresenta ainda os resultados de uma simulação analógica, que permite verificar que a impedância do reator série limitador, vista pelo circuito do forno, é pequena à 60 Hz e relativamente elevada em outras freqüências. Desta forma, tem-se um efetivo amortecimento das flutuações de corrente e tensão, causadas pela operação do forno, sem restringir a potência operacional do mesmo. / [en] This thesis presents the main electromechanical phenomena, occuring during the operating of an arc furnace, focusing the electric and magnetic ones. It also presents a digital simulation aiming to verify that the utilization of a series limiting current reactor included into the furnace feeding circuit, for arc stabilization purposes, does not reduce its operational capacity at 60 Hz. It is also presented the results of an analogic simulation, which shows that the reactor impedance seen by the furnace circuit is small at 60 Hz and relatively large at other frequencies. Hence, an effective damping of the current and voltage variations, caused by the furnace operation, can be achieved.

Energy efficiency is a driving factor in modern electronic design particularly in power conversion where conversion losses directly set the upper limit of system efficiency. A wide variety of commercially available DC-DC conversion elements have inefficiencies in the 90-97% range. The efficiency range of most common commercial-off-the-shelf (COTS) power supplies is 75-85%, highlighting the fact that COTS power supplies have not kept pace with efficiency improvements of modern conversion elements. Unmanned ground vehicles (UGVs) is an application where efficiency can be crucial in extending tight power budgets. In autonomous ground vehicles, geographic diversity with regard to sensor location is inherent because sensor orientation and placement are crucial to performance. Sensor power, therefore, is also distributed by nature of the devices being supplied. This thesis presents the design and evaluation of a smart power module used to implement a distributed power network in an autonomous ground vehicle. The module conversion element demonstrated an average efficiency of 96.7% for loads from 1-4A. Current monitoring and an adjustable output current limit were provided through a second circuit board within the same module enclosure. The module processing element sends periodic updates and receives commands over a CAN bus. The smart power modules successfully supply critical sensing and communication components in an operational autonomous ground vehicle. / Master of Science

科学研究費補助金 研究種目:基盤研究(A)(2) 課題番号:14205040 研究代表者:早川 直樹 研究期間:2002-2003年度