168 research outputs found
Control of three-phase electric springs used in microgrids under ideal and non-ideal conditions
No full textA control scheme is proposed for the three-phase electric springs (TPESs), based on the recently introduced δ control and an improved phase locked loop (PLL). The scheme utilizes three independent δ controls, one for each phase, to stabilize the voltages across the critical loads (CLs) while handing over imbalance and distortion of the microgrid voltages, in addition to their fluctuations, to the non-critical loads (NCLs). Instrumental in achieving this outcome is the operation of the improved PLL that separates the fundamental component of the positive sequence of the microgrid voltages from the other sequences and harmonics. The scheme is also able to stabilize the CL voltages under imbalance of CLs and NCLs. Simulation results obtained under various conditions of imbalance of the microgrid voltages and/or the loads, and of distortion of the microgrid voltages, taken individually and together, show the effectiveness of the proposed control scheme of TPESs.</p
Digitized material from "'Fujin bungei' kaisetsu, sōmokuji, sakuin"
Get PDFTables of contents and author-name index for the 10-volume set Fujin bungei.The Mellon Foundation - Council on East Asian Libraries Innovation Grants for East Asian Librarian
Digitized material from "Taishōki fujin mondai bunken shūsei shūroku shomoku : Kokuritsu Kokkai Toshokan hen shozō"
No full textTable of contents and title and author indexes for the 214-reel microfilm set Taishōki fujin mondai bunken shūsei: Kokuritsu Kokkai Toshokan hen shozō.The Mellon Foundation - Council on East Asian Libraries Innovation Grants for East Asian Librarian
Investigation into Multi-Phase Armature Windings for High-Temperature Superconducting Wind Turbine Generators
No full textHigh-Temperature superconducting (HTS) generators are being considered as a competitive candidate in large direct-drive (DD) wind turbines because of their features of being lightweight and compact. Normally a large air gap is inevitable in partially HTS generators, sacrificing the torque producing capability. In this paper, multi-phase armature windings for HTS generators are investigated to reduce the air gap length in HTS generators while not compromising generators' performance. Therefore, the torque density of HTS generators can be improved without any added costs. Five different multi-phase armature winding schemes are studied in the paper. Their performance regarding torque production and rotor losses in a 10 MW DD HTS generator are examined. The findings show that employing multi-phase armature windings can reduce the mechanical air gap without generating extra eddy current losses in the rotor, and the torque production can be improved by up to 9.1%. In addition, the alternating magnetic field reaching the HTS field winding are also reduced by using multi-phase armature windings, resulting in lower AC losses and cooling costs.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Hitome de wakaru Shina jihen to Nisso kankei echizu /
No full textRelief shown by shading and pictorially.; 880-06 Published as supplement to a women magazine, 'Fujin Kurabu', Nov 1937 issue.; Legends include: frontline of China-Japan conflict, pill box of Soviet Army front lines, military ports, military airports, disposition of Red Army troops, the Great Wall of China, areas occupied by the Japanese army in the Sino-Japanese Conflict so far (as of 1 October 1937), areas bombed by the Japanese (as of 1 October 1937).; The main map includes numerous pictorial features of people in each country and region on the map. Names of major cities are given, and several charts, such as a chronological chart of development of Sino-Japanese War and the chart of Soviet Union's army's armaments.; 880-07 Seizu Ebihara Bingo --- on the edge of two maps on the other side; Also available online http://nla.gov.au/nla.map-vn6856147. Cartoon style map of China (Japanese Women's Club)Map of East Asia and Soviet, detailing the development of the SIno-Japanese Conflict and the relationship of the Soviet Union and Japan at that time.Shina jihen to Nisso kankei echizu880-03 title of the map on verso: Konan chiho jikyoku shosaizu880-0 4 title of the map on verso: Shanhai, Nankin fuki
Variable Speed Wind Turbine Based on Multiple Generators Drive-Train Configuration
Get PDFA variable speed wind turbine is presented in this paper, where multiple permanent magnet synchronous generators (MPMSGs) drive-train configuration is employed in the wind turbine. A cascaded multilevel converter interface based on the MPMSGs is developed to synthesize a desired high ac sinusoidal output voltage, which could be directly connected to the grids. What is more, such arrangement has been made so that the output ac voltage having a selected phase angle difference among the stator windings of multiple generators. A phase angle shift strategy is proposed in this paper, which effectively reduce the fluctuation of the electromagnetic torque sum and results in a good performance for the MPMSGs structure. The simulation study is conducted using PSCAD/EMTDC, and the results verify the feasibility of this variable speed wind turbine based on multiple generators drive-train configuration
Power Control of Permanent Magnet Generator Based Variable Speed Wind Turbines
No full textWhen the wind power accounts for a large portion of the grid, it will be required to regulate the active power and reactive power. This paper investigates a MWlevel variable speed wind turbine with a permanent magnet synchronous generator (PMSG). The power control capabilities of two kinds of control schemes conducted respectively on this wind turbine under two conditions, including rapid wind speed change and grids faults, are compared. The simulation study of the wind turbine system is conducted using PSCAD/EMTDC, and the results show the different power control capabilities of the two control schemes.</p
Design and Control of A DC Grid for Offshore Wind Farms
Get PDFWind power is growing rapidly around the world, and the offshore wind farm is currently seen as a promising solution to satisfy the growing demand for renewable energy source. Along with the increase in the capacity of offshore wind farms and the distance between offshore wind farms and land, the high-voltage direct current (HVDC) is attractive. In addition, the DC grid may also be interested for interconnecting the wind turbines in the collection level. As a consequence, a DC grid can be established for the offshore wind farm, where the wind power collection system and power transmission system both adopt DC technology. S far, the existing grid codes for wind turbines are mainly focused on AC system. Therefore, the faults analysis in the DC grid and the appropriate fault protections are required for the DC grid.This thesis focuses on the design and control of the DC grid for offshore wind farms. The DC grid layout for offshore wind farm is introduced. The wind turbine configurations in DC grid are studied. A DC/DC converter is proposed for the wind turbine directly integrating to the DC grid. The operation principle of the DC/DC converter and the control of the wind turbine in DC grid are proposed as well. The HVDC transmission system configuration is studied. A DC/DC converter is proposed as the offshore converter to step up the collection level voltage to the transmission level voltage. The control strategies for the offshore converter and the onshore converter are proposed. The control of the DC grid under AC grid faults is discussed, and the improved control is presented to ride-through the AC grid faults for the DC grid. The cable fault in the HVDC transmission system is discussed. The performances of the HVDC system under faults are analyzed. And then, the protective inductor is proposed and designed for the HVDC system. Afterwards, the redundancy of the HVDC system under cable faults is studied, and a fault ride-through strategy is proposed for the DC grid under cable faults.Throughout the thesis, the DC grid for offshore wind farms examples are modeled with the professional tool PSCAD/EMTDC, and the DC/DC converter prototype was built and tested in the laboratory, and the results verify the theoretical analysis
Design and Control of A DC Grid for Offshore Wind Farms
Get PDFWind power is growing rapidly around the world, and the offshore wind farm is currently seen as a promising solution to satisfy the growing demand for renewable energy source. Along with the increase in the capacity of offshore wind farms and the distance between offshore wind farms and land, the high-voltage direct current (HVDC) is attractive. In addition, the DC grid may also be interested for interconnecting the wind turbines in the collection level. As a consequence, a DC grid can be established for the offshore wind farm, where the wind power collection system and power transmission system both adopt DC technology. S far, the existing grid codes for wind turbines are mainly focused on AC system. Therefore, the faults analysis in the DC grid and the appropriate fault protections are required for the DC grid.This thesis focuses on the design and control of the DC grid for offshore wind farms. The DC grid layout for offshore wind farm is introduced. The wind turbine configurations in DC grid are studied. A DC/DC converter is proposed for the wind turbine directly integrating to the DC grid. The operation principle of the DC/DC converter and the control of the wind turbine in DC grid are proposed as well. The HVDC transmission system configuration is studied. A DC/DC converter is proposed as the offshore converter to step up the collection level voltage to the transmission level voltage. The control strategies for the offshore converter and the onshore converter are proposed. The control of the DC grid under AC grid faults is discussed, and the improved control is presented to ride-through the AC grid faults for the DC grid. The cable fault in the HVDC transmission system is discussed. The performances of the HVDC system under faults are analyzed. And then, the protective inductor is proposed and designed for the HVDC system. Afterwards, the redundancy of the HVDC system under cable faults is studied, and a fault ride-through strategy is proposed for the DC grid under cable faults.Throughout the thesis, the DC grid for offshore wind farms examples are modeled with the professional tool PSCAD/EMTDC, and the DC/DC converter prototype was built and tested in the laboratory, and the results verify the theoretical analysis
An offshore wind farm with dc grid connection and its performance under power system transients
No full textThe continuous increase in wind power penetration level brings new requirements for wind turbine integration into the network. The grid code requires that after clearance of an external short-circuit fault, grid-connected wind turbines should restore their normal operation without power loss caused by disconnections. This paper presents a transient performance study of an offshore wind farm with HVDC transmission for grid connection, where the wind turbines in the offshore wind farm are also connected with dc collection network. A power-reduction control strategy (PRCS) for transient performance improvement is proposed for the offshore wind farm that allows it to withstand severe voltage dips. A simulation model of a 400 MW offshore wind farm developed in PSCAD/EMTDC is presented. The transient performance of the offshore wind farm is studied, and the results show the effectiveness of the proposed control strategy
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