In a Doubly-fed Induction Generator (DFIG) wind energy conversion system, the rotor of a wound rotor induction generator is connected to the grid via a partial scale ac/ac power electronic converter which controls the rotor frequency and speed. In this research, detailed models of the DFIG wind energy conversion system with Sinusoidal Pulse-Width Modulation (SPWM) scheme and Optimal Pulse-Width Modulation (OPWM) scheme for the power electronic converter are developed in detail in PSCAD/EMTDC. As the computer simulation using the detailed models tends to be computationally extensive, time consuming and even sometimes not practical in terms of speed, two modified approaches (switching-function modeling and average-value modeling) are proposed to reduce the simulation execution time. The results demonstrate that the two proposed approaches reduce the simulation execution time while the simulation results remain close to those obtained using the detailed model simulation.

In a Doubly-fed Induction Generator (DFIG) wind energy conversion system, the rotor of a wound rotor induction generator is connected to the grid via a partial scale ac/ac power electronic converter which controls the rotor frequency and speed. In this research, detailed models of the DFIG wind energy conversion system with Sinusoidal Pulse-Width Modulation (SPWM) scheme and Optimal Pulse-Width Modulation (OPWM) scheme for the power electronic converter are developed in detail in PSCAD/EMTDC. As the computer simulation using the detailed models tends to be computationally extensive, time consuming and even sometimes not practical in terms of speed, two modified approaches (switching-function modeling and average-value modeling) are proposed to reduce the simulation execution time. The results demonstrate that the two proposed approaches reduce the simulation execution time while the simulation results remain close to those obtained using the detailed model simulation.

Saarbrücken, Univ., Diss., 1993.

Saarbrücken, Univ., Diss., 1993. / Computerdatei im Fernzugriff.

Universiẗat, Diss., 1993--Saarbrücken.

No description available.

The benefits of being average were examined within the context of romantic relationships by focusing on courtship progression and events for 164 married couples. The courtship progression was captured using a graph of the fluctuations in the percentage chance of marriage for each spouse from when couples first began dating up until the wedding day. Five factors were then used to capture the graph: Time elapsed to progress from 25 to 75% chance of marriage, turbulence in chance of marriage values, average change in percent chance of marriage between relationship events, courtship length, and the sum of squared deviations from a straight line connecting when couples first started dating until their marriage date. Couples also reported on the timing of important relationship events (i.e., meeting parents, first fell in love, first sexual intercourse, and engagement) that were then compared to the order of the average courtship event progression. Deviations from the average courtship in terms of either graphical or event indicators did not significantly predict whether or not couples divorced in the first 13 years of marriage. / text

One of the critical issues of systems utilizing Orthogonal Frequency Division Multiplexing (OFDM) is the high peak to the average power ratio of OFDM signals. We have used Precoding as a way to mitigate the PAPR problem. Furthermore the performance of Precoded OFDM in fading multi-path channels has been studied. This thesis is based on an efficient technique for reducing the PAPR of OFDM signals. The proposed technique is data-independent and thus, does not require new processing and optimization for each transmitted OFDM block. The reduction in PAPR of the OFDM signal is obtained through a proper selection of a Precoding scheme that distributes the power of each modulated symbol over the OFDM block. The obtained results show that this Precoding scheme is an attractive solution to the PAPR problem of OFDM signals.

The recent convergence in average earnings in the regions of Great Britain is in contrast to the increasing inequality in the overall structure of earnings. This thesis investigates the degree of earnings inequality in the regions of Great Britain over the period 1975 to 1995. The analysis employs the New Earnings Survey and the British Household Panel Survey datasets to decompose national earnings inequality into between-group and within-group inequality, both cross-sectionally ad over time, and finds that it is the increasing inequality within regions that is the primary source of increasing inequality in the national distribution of earnings. A decomposition of the Gini coefficient is also adopted to illustrate how regional convergence of the Gini coefficient is also adopted to illustrate how regional convergence in average earnings has been accompanied by increasing overall earnings inequality in Great Britain. The New Earnings Survey data is further used to model the determinants of regional earnings. Cross-section earnings equations are estimated to identify those factors that influence the determination of earnings within regions, and how these factors have contributed to the increase in overall earnings inequality over the twenty-year period. Quantile regression analysis is employed to show whether the effects of the determinants of regional earnings are the same across the regional earnings distributions, and national OLS and quantile regressions are estimated in order to test potential explanations for the rise in national earnings inequality. Using the panel nature of the NES a fixed-effects specification is also used to estimate regional earnings equations, where such a specification allows for the control of individual-specific heterogeneity.

No description available.