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

Novel Algorithms for Modern Power Systems

The restructuring of the electric power industry has brought about many interesting and new problems to be solved by researchers. Some of the problems have been considered and suitable intelligent techniques that have been developed are described in this thesis. A new technique using wavelet transform and neural networks for fault location and protection of a practical tee-circuit has been developed. Fault simulation is carried out using EMTP software. The waveforms obtained from the simulation are then used in wavelet analysis to generate patterns for training and validation, which is carried out using Radial Basis Function network. Dynamic Protection Modelling (DPM) software developed by the University of Strathclyde, Centre for Electrical Power Engineering is used for the evaluation of relay settings. A new approach is proposed to use object oriented techniques and improved genetic algorithms in developing software to estimate generator excitation control system parameters. Simulation studies are carried using data representing a generator, with its transformer connected to an infinite busbar. Application of evolutionary programming to Optimal Power Flow is another technique that is proposed in this work. The objective is to minimize fuel cost keeping the system secure under both normal and contingent states. Studies are carried out using the IEEE - 30 bus test system. A short-term load-forecasting model using Artificial Neural Networks and Genetic Algorithm has been developed and tested on data obtained from a power company. It is found that the time taken to obtain a satisfactory solution is long, as the problem is very complex. This points in the direction of evolutionary computing being integrated with parallel processing techniques to solve such practical problems. A novel approach to the formulation and evaluation of transmission loss and line flow through a set of new loss coefficients and distribution factors respectively which are efficient, exact and robust and suitable for real time application is proposed. These loss coefficients and distribution factors are generated from the available load flow solution with trivial computational burden. Results on IEEE Test systems show that the coefficients need not be re-evaluated for wide changes in system operating condition

Optimised design of isolated industrial power systems and system harmonics

This work has focused on understanding the nature and impact of non-linear loads on isolated industrial power systems. The work was carried out over a period of 8 years on various industrial power systems: off-shore oil and gas facilities including an FPSO, a wellhead platform, gas production platforms, a mineral processing plant and an LNG plant. The observations regarding non-linear loads and electrical engineering work carried out on these facilities were incorporated into the report.A significant literature describing non-linear loads and system harmonics on industrial power systems was collected and reviewed. The literature was classified into five categories: industrial plants and system harmonics, non-linear loads as the source of current harmonics, practical issues with system harmonics, harmonic mitigation strategies and harmonic measurements.Off-shore oil and gas production facilities consist of a small compact power system. The power system incorporates either its own power generation or is supplied via subsea cable from a remote node. Voltage selection analysis and voltage drop calculation using commercially available power system analysis software are appropriate tools to analyse these systems. Non-linear loads comprise DC rectifiers, variable speed drives, UPS systems and thyristor controlled process heaters. All nonlinear loads produce characteristic and non-characteristic harmonics, while thyristor controlled process heaters generate inter-harmonics. Due to remote location, harmonic survey is not a common design practice. Harmonic current measurements during factory acceptance tests do not provide reliable information for accurate power system analysis.A typical mineral processing plant, located in a remote area includes its own power station. The power generation capacity of those systems is an order of magnitude higher than the power generation of a typical off-shore production facility. Those systems comprise large non-linear loads generating current and voltage interharmonics. Harmonic measurements and harmonic survey will provide a full picture of system harmonics on mineral processing plants which is the only practical way to determine system harmonics. Harmonic measurements on gearless mill drive at the factory are not possible as the GMD is assembled for the first time on site.LNG plants comprise large non-linear loads driving gas compressor, however those loads produce integer harmonics. Design by analysis process is an alternative to the current design process based on load lists. Harmonic measurements and harmonic survey provide a reliable method for determining power system harmonics in an industrial power system

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

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)

NASA Tech Briefs, September 1993

Topics include: Microelectronics; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Reports

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