63,562 research outputs found
Distributed Generation as Voltage Support for Single Wire Earth Return Systems
Key issues for distributed generation (DG) inclusion in a distribution system include operation, control, protection, harmonics, and transients. This paper analyzes two of the main issues: operation and control for DG installation. Inclusion of DG in distribution networks has the potential to adversely affect the control of voltage. Both DG and tap changers aim to improve voltage profile of the network, and hence they can interact causing unstable operation or increased losses. Simulations show that a fast responding DG with appropriate voltage references is capable of reduction of such problems in the network. A DG control model is developed based on voltage sensitivity of lines and evaluated on a single wire earth return (SWER) system. An investigation of voltage interaction between DG controllers is conducted and interaction-index is developed to predict the degree of interaction. From the simulation it is found that the best power factor for DG injection to achieve voltage correction becomes higher for high resistance lines. A drastic reduction in power losses can be achieved in SWER systems if DG is installed. Multiple DG can aid voltage profile of feeder and should provide higher reliability. Setting the voltage references of separate DGs can provide a graduated response to voltage correction
Architecture of a network-in-the-Loop environment for characterizing AC power system behavior
This paper describes the method by which a large hardware-in-the-loop environment has been realized for three-phase ac power systems. The environment allows an entire laboratory power-network topology (generators, loads, controls, protection devices, and switches) to be placed in the loop of a large power-network simulation. The system is realized by using a realtime power-network simulator, which interacts with the hardware via the indirect control of a large synchronous generator and by measuring currents flowing from its terminals. These measured currents are injected into the simulation via current sources to close the loop. This paper describes the system architecture and, most importantly, the calibration methodologies which have been developed to overcome measurement and loop latencies. In particular, a new "phase advance" calibration removes the requirement to add unwanted components into the simulated network to compensate for loop delay. The results of early commissioning experiments are demonstrated. The present system performance limits under transient conditions (approximately 0.25 Hz/s and 30 V/s to contain peak phase-and voltage-tracking errors within 5. and 1%) are defined mainly by the controllability of the synchronous generator
Calibration and performance of the photon sensor response of FACT -- The First G-APD Cherenkov telescope
The First G-APD Cherenkov Telescope (FACT) is the first in-operation test of
the performance of silicon photo detectors in Cherenkov Astronomy. For more
than two years it is operated on La Palma, Canary Islands (Spain), for the
purpose of long-term monitoring of astrophysical sources. For this, the
performance of the photo detectors is crucial and therefore has been studied in
great detail. Special care has been taken for their temperature and voltage
dependence implementing a correction method to keep their properties stable.
Several measurements have been carried out to monitor the performance. The
measurements and their results are shown, demonstrating the stability of the
gain below the percent level. The resulting stability of the whole system is
discussed, nicely demonstrating that silicon photo detectors are perfectly
suited for the usage in Cherenkov telescopes, especially for long-term
monitoring purpose
Harmonic correction in power supplies feeding non-linear loads
This paper focuses on the design of an electronic circuit which can be used in conjunction with the power supplies used at the input of non-linear loads (computers, TV sets, etc.) in order to filter out the input current harmonics in such loads. The electronic circuit will fill the gaps of the distorted current waveform so that it becomes sinusoidal and also in phase with the mains supply. In this paper different configurations of the proposed electronic circuit are covered (depending on the location with respect to the non-linear load). An optimization algorithm is carried out in order to find the best location, minimum device rating for different type of loads. The proposed circuit monitors the input current, output voltage and power rating of the power supply. The circuit will then decide whether to filter the input current harmonics or the output voltage harmonics. The circuit will also optimize the best switching frequency for the required load so that the power supply operates at the maximum possible efficiency
Technical design and commissioning of the KATRIN large-volume air coil system
The KATRIN experiment is a next-generation direct neutrino mass experiment
with a sensitivity of 0.2 eV (90% C.L.) to the effective mass of the electron
neutrino. It measures the tritium -decay spectrum close to its endpoint
with a spectrometer based on the MAC-E filter technique. The -decay
electrons are guided by a magnetic field that operates in the mT range in the
central spectrometer volume; it is fine-tuned by a large-volume air coil system
surrounding the spectrometer vessel. The purpose of the system is to provide
optimal transmission properties for signal electrons and to achieve efficient
magnetic shielding against background. In this paper we describe the technical
design of the air coil system, including its mechanical and electrical
properties. We outline the importance of its versatile operation modes in
background investigation and suppression techniques. We compare magnetic field
measurements in the inner spectrometer volume during system commissioning with
corresponding simulations, which allows to verify the system's functionality in
fine-tuning the magnetic field configuration. This is of major importance for a
successful neutrino mass measurement at KATRIN.Comment: 32 pages, 16 figure
JUNO Conceptual Design Report
The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine
the neutrino mass hierarchy using an underground liquid scintillator detector.
It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants
in Guangdong, China. The experimental hall, spanning more than 50 meters, is
under a granite mountain of over 700 m overburden. Within six years of running,
the detection of reactor antineutrinos can resolve the neutrino mass hierarchy
at a confidence level of 3-4, and determine neutrino oscillation
parameters , , and to
an accuracy of better than 1%. The JUNO detector can be also used to study
terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard
Model. The central detector contains 20,000 tons liquid scintillator with an
acrylic sphere of 35 m in diameter. 17,000 508-mm diameter PMTs with high
quantum efficiency provide 75% optical coverage. The current choice of
the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO
as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of
detected photoelectrons per MeV is larger than 1,100 and the energy resolution
is expected to be 3% at 1 MeV. The calibration system is designed to deploy
multiple sources to cover the entire energy range of reactor antineutrinos, and
to achieve a full-volume position coverage inside the detector. The veto system
is used for muon detection, muon induced background study and reduction. It
consists of a Water Cherenkov detector and a Top Tracker system. The readout
system, the detector control system and the offline system insure efficient and
stable data acquisition and processing.Comment: 328 pages, 211 figure
Recommended from our members
TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
GRAPE-6: The massively-parallel special-purpose computer for astrophysical particle simulation
In this paper, we describe the architecture and performance of the GRAPE-6
system, a massively-parallel special-purpose computer for astrophysical
-body simulations. GRAPE-6 is the successor of GRAPE-4, which was completed
in 1995 and achieved the theoretical peak speed of 1.08 Tflops. As was the case
with GRAPE-4, the primary application of GRAPE-6 is simulation of collisional
systems, though it can be used for collisionless systems. The main differences
between GRAPE-4 and GRAPE-6 are (a) The processor chip of GRAPE-6 integrates 6
force-calculation pipelines, compared to one pipeline of GRAPE-4 (which needed
3 clock cycles to calculate one interaction), (b) the clock speed is increased
from 32 to 90 MHz, and (c) the total number of processor chips is increased
from 1728 to 2048. These improvements resulted in the peak speed of 64 Tflops.
We also discuss the design of the successor of GRAPE-6.Comment: Accepted for publication in PASJ, scheduled to appear in Vol. 55, No.
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