Five-level inverter employing WRPWM switching scheme

Multilevel Random Pulse Width Modulation (RPWM) schemes have drawn increasing attention in the past few years. Multilevel topologies provide high voltage and high power capabilities and random PWM schemes offer reduction in discrete harmonics spectral. This dissertation provides a generalized theory and analysis methods of the standard five-level Weighted RPWM (WRPWM). Equations have been derived to analyze the spectral performance and average switching frequency of the WRPWM output waveform using statistical approach. A modified WRPWM scheme has been proposed. The modified WRPWM scheme is then analyzed with the equations derived from the same approach. The analyzed theoretical spectrum of the standard five-level WRPWM is then compared with the three-level WRPWM scheme and the conventional carrier based PWM scheme. A scaled laboratory prototype diode clamping five-level inverter has been built for verification of the standard and the proposed modified WRPWM schemes. It can be seen that the experimental measurements and the theoretical analyzed results are all in good agreement. Results show the two five-level WRPWM schemes offers significant improvements on the spectrum content than the conventional carrier based PWM scheme. It was found that the five-level WRPWM schemes have successfully suppress the magnitude of third harmonic below 5% of the magnitude of fundamental component and even less for the higher order harmonic components. Research contributions made by the dissertation are: - The proposed modified multilevel WRPWM scheme which utilizing the switching decision redundancy of multilevel inverter to manipulate the harmonic content of the output signal. - The derived mathematical equations of the standard and modified five-level WRPWM scheme for analytical purposes.Dissertation (MEng (Electrical Engineering))--University of Pretoria, 2005.Electrical, Electronic and Computer Engineeringunrestricte

Investigación sobre la flexibilidad de la demanda en redes eléctricas inteligentes: control directo de cargas

In recent decades, the European Union has made decisive efforts to maintain its global leadership in renewable energies to meet climate change targets resulting from international agreements. There is a deliberate intention to reduce the usage of non-renewable energy sources and promote the exploitation of renewable generation at all levels as shown by energy production data within the Eurozone. The electricity sector illustrates a successful implementation of these energy policies: The electricity coming from combustible fuels was at historical lows in 2018, accounting for 83.6 % of the electricity generated from this source in 2008. By contrast, the pool of renewables reached almost 170 % of the 2008 production. Against this background, power systems worldwide are undergoing deep-seated changes due to the increasing penetration of these variable renewable energy sources and distributed energy resources that are intermittent and stochastic in nature. Under these conditions, achieving a continuous balance between generation and consumption becomes a challenge and may jeopardize the system stability, which points out the need of making the power system flexible enough as a response measure to this trend. This Ph.D. thesis researches one of the principal mechanisms providing flexibility to the power system: The demand-side management, seen from both the demand response and the energy efficiency perspectives. Power quality issues as a non-negligible part of energy efficiency are also addressed. To do so, several strategies have been deployed at a double level. In the residential sector, a direct load control strategy for smart appliances has been developed under a real-time pricing demand response scheme. This strategy seeks to minimize the daily cost of energy in presence of diverse energy resources and appliances. Furthermore, a spread spectrum technique has also been applied to mitigate the highfrequency distortion derived from the usage of LED technology lighting systems instead of traditional ones when energy efficiency needs to be improved. In the industrial sector, a load scheduling strategy to control the AC-AC power electronic converter in charge of supporting the electric-boosted glass melting furnaces has been developed. The benefit is two-fold: While it contributes to demand flexibility by shaving the peaks found under conventional control schemes, the power quality issues related to the emission of subharmonics are also kept to a minimum. Concerning the technologies, this Ph.D. thesis provides smart solutions, platforms, and devices to carry out these strategies: From the application of the internet of things paradigm to the development of the required electronics and the implementation of international standards within the energy industry.En las últimas décadas, la Unión Europea ha realizado esfuerzos decisivos para mantener su liderazgo mundial en energías renovables con el fin de cumplir los objetivos de cambio climático resultantes de los acuerdos internacionales. Muestra una intención deliberada de reducir el uso de fuentes de energía no renovable y promover la explotación de la generación renovable a todos los niveles, como demuestran los datos de producción de energía en la eurozona. El sector de la electricidad ilustra un caso de éxito de estas políticas energéticas: la electricidad procedente de combustibles fósiles estaba en mínimos históricos en 2018, representando el 83,6 % de la electricidad generada a partir de esta fuente en 2008; en cambio, el grupo de renovables alcanzó casi el 170 % de la producción de 2008. En este contexto, los sistemas eléctricos de todo el mundo están experimentando profundos cambios debido a la creciente penetración de estas fuentes de energía renovable y de recursos energéticos distribuidos que son de naturaleza variable, intermitente y estocástica. En estas condiciones, lograr un equilibrio continuo entre generación y consumo se convierte en un reto y puede poner en peligro la estabilidad del sistema, lo que señala la necesidad de flexibilizar el sistema eléctrico como medida de respuesta a esta tendencia. Esta tesis doctoral investiga uno de los principales mecanismos que proporcionan flexibilidad al sistema eléctrico: la gestión de la demanda vista tanto desde la perspectiva de la respuesta a la demanda como de la eficiencia energética. También se abordan los problemas de calidad de suministro entendidos como parte no despreciable de la eficiencia energética. Para ello, se han desplegado varias estrategias a un doble nivel. En el sector residencial, se ha desarrollado una estrategia basada en el control directo de cargas para los electrodomésticos inteligentes siguiendo un esquema de respuesta a la demanda con precios en tiempo real. Esta estrategia busca minimizar el coste diario de la energía en presencia de diversos recursos energéticos y electrodomésticos. Además, también se ha aplicado una técnica de espectro ensanchado para mitigar la distorsión de alta frecuencia derivada del uso de sistemas de iluminación con tecnología LED, empleados para la mejora de la eficiencia energética frente a las tecnologías convencionales. En el sector industrial, se ha desarrollado una estrategia de planificación de cargas para controlar el convertidor AC-AC de los hornos de fundición de vidrio con soporte eléctrico. El beneficio es doble: mientras que se contribuye a la flexibilidad de la demanda al eliminar los picos encontrados en los esquemas de control convencionales, también se reducen al mínimo los problemas de calidad de suministro relacionados con la emisión de subarmónicos. En cuanto a las tecnologías, esta tesis doctoral aporta soluciones, plataformas y dispositivos inteligentes para llevar a cabo estas estrategias: desde la aplicación del paradigma del internet de las cosas hasta el desarrollo de la electrónica necesaria y la implementación de estándares internacionales dentro de la industria energética

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion