Home About us Contact
|
Home About us Contact | ||
|
|
||
Voltage Fluctuation (voltage + fluctuation)
Selected AbstractsA simple method for output voltage control of a three-phase multilevel inverter considering DC voltage fluctuationELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010Kenji Amei Abstract Multilevel inverter circuit generates the stair-like voltage without using transformer and interphase reactor, and it is the circuit which realizes reduction in the harmonics and enlargement of the capacity. In addition, the application of PWM control improves the waveform, and reduces the switching component to the conventional half, and the filter capacity is reduced. In this paper, improvement on the voltage utilization factor and feedback control of output voltage are applied to multilevel inverter circuit. For the DC power supply with the intense fluctuation, it is necessary to construct inverter circuit which can supply stabilized AC voltage. One-chip microcomputer with various functions is used for the control equipment of this circuit, and miniaturization and cost reduction of the control equipment are realized. Here, the control principle and experimental results of this equipment are mainly reported. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 40,47, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20906 [source] Voltage fluctuation compensator for ShinkansenELECTRICAL ENGINEERING IN JAPAN, Issue 4 2008Tetsuo Uzuka Abstract In AC electric railways, three-phase voltage is changed into the single-phase circuit of two circuits with the Scott-connected transformer. If unbalancing of the load between single-phase circuits becomes large, voltage fluctuation becomes large on the three-phase side. Railway static power conditioner (RPC) was developed for the purpose of controlling voltage fluctuation on the three-phase side. An RPC is comprised of a pair of self-commutated PWM inverters. These inverters connect the main phase and teaser feeding buses, coupled with a DC side capacitor such as a back-to-back (BTB) converter. In this way, the two self-commutated inverters can act as a static var compensator (SVC) to compensate for the reactive power and as an active power accommodator from one feeding bus to another. 20 MVA/60 kV RPCs started commercial operation in 2002 at each two substations on the newly extended Tohoku Shinkansen for compensating voltage fluctuation on the three-phase side caused by traction loads, absorbing harmonic current. The results of operational testing indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, and handle the exciting rush current of transformers, as well as compensate for harmonics successfully. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(4): 25,34, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20397 [source] Application of decentralized control for remote power system stabilization by installing renewable energy power plantIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2008Tomonobu Senjyu Senior Member Abstract The generating power of wind turbines varies in proportion to the cube of wind speed, hence, they cannot supply constant power and this causes fluctuations in frequency and voltage. This article presents a methodology for controlling grid frequency, hydrogen volume, and terminal bus voltage. This system consists of diesel generators, wind turbines, and load. Aqua electrolyzer and fuel cells are introduced in order to control grid frequency, voltage, and hydrogen volume. By applying H, control, frequency, voltage fluctuation, and hydrogen volume, controls are achieved. H, decentralized controllers are designed and installed for diesel generators, aqua electrolyzers, and fuel cells in series. In order to verify the effectiveness of the suggested system, MATLAB/SIMULINK is used for simulation. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Electrical penetration graphs of the nymphal stage of Bemisia argentifoliiENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2003Y.X. Jiang Abstract Electrical penetration graph (EPG, DC system) waveforms were recorded from first, second, and third instar Bemisia argentifolii nymphs. Waveforms recorded were similar among the three instars. Four waveforms were recorded and were named C, J, L, and H. Waveform J is new, whereas waveforms C, L, and H of B. argentifolii nymphs were similar to those published previously from greenhouse whitefly nymphs. As in the previous study on greenhouse whitefly nymphs, there was variation in each of waveforms C, L, and H. Waveform C was recorded at an extracellular voltage level, and represents a pathway phase where the stylets penetrate the plant tissue in an intercellular pathway. At the end of waveform C, the voltage dropped to an intracellular level, indicating penetration of a living cell, and the stylet tips then remained in that cell for the rest of the EPG recording, which was sometimes as long as 16 h. Three waveforms (J, L, and H) were recorded during this intracellular phase, beginning with J, a brief (average = 31 s), low amplitude, irregular waveform. J appeared only at the beginning of the intracellular phase, and was followed by either L (five out of eight times) or H (three out of eight times). Waveforms L and H then alternated with one another for the remainder of the intracellular phase. The most conspicuous difference between L and H was the frequency of their voltage fluctuations; L had a lower frequency and H a higher frequency. Usually the shape of waveform L was dominated by voltage peaks in a positive direction, while waveform H was characterized by strong voltage peaks in a negative direction; although some variants of both L and H had distinct voltage peaks in both directions. The electrical origin of both the positive and negative voltage peaks was electromotive force (emf) fluctuation rather than resistance fluctuation. During waveform H, copious amounts of honeydew were produced, indicating that the penetrated cell was a sieve element. We conclude, therefore, that H represents phloem sap ingestion; and because J and L are produced in the same cell as H, then phloem phase is represented by waveforms J, L, and H. The biological correlations for J and L are not yet known. [source] New converter-fed power source to increase the dynamic performance of the three-phase electric arc furnaceEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2000A. Wolf The conventional three-phase electric arc furnaces frequently cause undesired distortions in the power system, which has a low short-circuit capacity in the form of voltage fluctuations (flicker) at the point of common coupling. This is due to the fluctuating reactive power consumption of the furnace. This paper describes a electronic-controlled furnace transformer which enables the reactive power consumed by the furnace to be kept constant. This is made possible if the conventional power system of the three-phase electric arc furnace is supplemented with three-phase power controllers and a booster transformer. By regulating the (reactive) power input, these disturbances can be reduced to a minimum. This new power source was experimentally tested on a single-phase model and the results, which are presented, are very satisfactory. [source] | ||||||||||