14 research outputs found
Output Voltage Response Improvement and Ripple Reduction Control for Input-parallel Output-parallel High-Power DC Supply
A three-phase isolated AC-DC-DC power supply is widely used in the industrial
field due to its attractive features such as high-power density, modularity for
easy expansion and electrical isolation. In high-power application scenarios,
it can be realized by multiple AC-DC-DC modules with Input-Parallel
Output-Parallel (IPOP) mode. However, it has the problems of slow output
voltage response and large ripple in some special applications, such as
electrophoresis and electroplating. This paper investigates an improved
Adaptive Linear Active Disturbance Rejection Control (A-LADRC) with flexible
adjustment capability of the bandwidth parameter value for the high-power DC
supply to improve the output voltage response speed. To reduce the DC supply
ripple, a control strategy is designed for a single module to adaptively adjust
the duty cycle compensation according to the output feedback value. When
multiple modules are connected in parallel, a Hierarchical Delay Current
Sharing Control (HDCSC) strategy for centralized controllers is proposed to
make the peaks and valleys of different modules offset each other. Finally, the
proposed method is verified by designing a 42V/12000A high-power DC supply, and
the results demonstrate that the proposed method is effective in improving the
system output voltage response speed and reducing the voltage ripple, which has
significant practical engineering application value.Comment: Accepted by IEEE Transactions on Power Electronic
Recent Development of Hybrid Renewable Energy Systems
Abstract: The use of renewable energies continues to increase. However, the energy obtained from renewable resources is variable over time. The amount of energy produced from the renewable energy sources (RES) over time depends on the meteorological conditions of the region chosen, the season, the relief, etc. So, variable power and nonguaranteed energy produced by renewable sources implies intermittence of the grid. The key lies in supply sources integrated to a hybrid system (HS)
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
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Effects of overvoltage on power consumption
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.In the recent years there is an increasing need of electrical and electronic units for household, commercial and industrial use. These loads require a proper electrical power supply to convey optimal energy, i.e. kinetic, mechanical, heat, or electrical with different form. As it is known, any electrical or electronic unit in order to operate safely and satisfactory, requires that the nominal voltages provided to the power supply are kept within strict boundary values defined by the electrical standards and certainly there is no unit that can be supplied with voltage values above or below these specifications; consequently, for their correct and safe operation, priority has been given to the appropriate electrical power supply. Moreover, modern electrical and electronic equipment, in order to satisfy these demands in efficiency, reliability, with high speed and accuracy in operation, employ modern semiconductor devices in their circuitries or items. Nevertheless, these modern semiconductor devices or items appear non-linear transfer characteristics in switching mode, which create harmonic currents and finally distort the sinusoidal ac wave shape of the current and voltage supply.
This dissertation proposes an analysis and synthesis of a framework specifically on what happens on power consumption in different types of loads or equipment when the nominal voltage supply increases over the permissibly limits of operation. A variety of loads have been selected from those used in everyday life, for household needs, office needs, as well as trade and industry. They were classified in two main categories, the passive loads and the non-linear loads. The classification was made on the event that the passive loads do not create harmonic currents but the non-linear loads create harmonic currents. For the above purpose was made practical experimental testings on several loads – equipment of both the categories in the laboratories, summarising the effects of the supplying voltages in power consumption at higher values1 gradually, from the nominal values up to the overvoltages. Also in some cases, for more accurate observation, was used the PSpice simulating program.
1 For a better understanding of the events, some experimental testings was made at lower supplying voltages – undervoltages across the loads.
Finally, the results from the experimental testings confirmed that the effects of the overvoltages are:
the increased consumption of power,
the decrease of the lifespan of electronic components due to overheating,
they are different with respect to the nature of the loads,
the increased amplitude of the current harmonics in the non-linear loads.
For harmonic current reduction, an easy to use Pulse Width Modulation (PWM) method is proposed through booster topology, using a minimum number of components. This electronic circuit (harmonic current reducer) is cheap and easy to use, and can be easily connected between the mains supply and the non-linear load. It reduces, or keeps in low level the amplitudes of the current harmonics of the supplying current (distorted) of a non-linear load, in order to offer an extra protection or relief to the load when the supplying voltage or mains increases from its nominal value to undesired overvoltage values.
Also, in order to avoid the undesirable effects on power consumption, due to overvoltages, design of a prototyping electronic circuit is proposed. This circuit (stabiliser), like the above harmonic current reducer, can be easily connected between the mains supply and a load or equipment; despite the mains supply variations, it keeps constant the desired or nominal voltage supply (voltage amplitude, Vpeak to peak) across the load or equipmen