170,106 research outputs found
Scaling properties of noise-induced switching in a bistable tunnel diode circuit
Noise-induced switching between coexisting metastable states occurs in a wide
range of far-from-equilibrium systems including micro-mechanical oscillators,
epidemiological and climate change models, and nonlinear electronic transport
in tunneling structures such as semiconductor superlattices and tunnel diodes.
In the case of tunnel diode circuits, noise-induced switching behavior is
associated with negative differential resistance in the static current-voltage
characteristics and bistability, i.e., the existence of two macroscopic current
states for a given applied voltage. Noise effects are particularly strong near
the onset and offset of bistable current behavior, corresponding to bifurcation
points in the associated dynamical system. In this paper, we show that the
tunnel diode system provides an excellent experimental platform for the
precision measurement of scaling properties of mean switching times versus
applied voltage near bifurcation points. More specifically, experimental data
confirm that the mean switching time scales logarithmically as the 3/2 power of
voltage difference over an exceptionally wide range of time scales and noise
intensities.Comment: 9 pages, 9 figures, accepted manuscript for publication in the
European Physical Journal B, Topical Issue: Non-Linear and Complex Dynamics
in Semiconductors and Related Material
Power quality and electromagnetic compatibility: special report, session 2
The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems.
Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages).
The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks:
Block 1: Electric and Magnetic Fields, EMC, Earthing systems
Block 2: Harmonics
Block 3: Voltage Variation
Block 4: Power Quality Monitoring
Two Round Tables will be organised:
- Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13)
- Reliability Benchmarking - why we should do it? What should be done in future? (RT 15
Maximum power point tracking converter based on the open-circuit voltage method for thermoelectric generators
Thermoelectric generators (TEGs) convert heat energy into electricity in a quantity dependant on the temperature difference across them and the electrical load applied. It is critical to track the optimum electrical operating point through the use of power electronic converters controlled by a Maximum Power Point Tracking (MPPT) algorithm. The MPPT method based on the opencircuit voltage is arguably the most suitable for the linear electrical characteristic of TEGs. This paper presents an innovative way to perform the open-circuit voltage measure during the pseudo-normal operation of the interfacing power electronic converter. The proposed MPPT technique is supported by theoretical analysis and used to control a synchronous buck-boost converter. The prototype MPPT converter is controlled by an inexpensive microcontroller, and a lead-acid battery is used to accumulate the harvested energy. Experimental results using commercial TEG devices prove that the converter accurately tracks the maximum power point during thermal transients. Precise measurements in steady state show that the converter finds the maximum power point with a tracking efficiency of 99.85%
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Diagnostic Applications for Micro-Synchrophasor Measurements
This report articulates and justifies the preliminary selection of diagnostic applications for data from micro-synchrophasors (µPMUs) in electric power distribution systems that will be further studied and developed within the scope of the three-year ARPA-e award titled Micro-synchrophasors for Distribution Systems
Dynamic Response of a fast near infra-red Mueller matrix ellipsometer
The dynamic response of a near infrared Ferroelectric Liquid Crystal based
Mueller matrix ellipsometer (NIR FLC-MME) is presented. A time dependent
simulation model, using the measured time response of the individual FLCs, is
used to describe the measured temporal response. Furthermore, the impulse
response of the detector and the pre-amplifier is characterized and included in
the simulation model. The measured time-dependent intensity response of the MME
is reproduced in simulations, and it is concluded that the switching time of
the FLCs is the limiting factor for the Mueller matrix measurement time of the
FLC-based MME. Based on measurements and simulations our FLC based NIR-MME
system is estimated to operate at the maximum speed of approximately 16 ms per
Mueller matrix measurement. The FLC-MME may be operated several times faster,
since the switching time of the crystals depends on the individual crystal
being switched, and to what state it is switched. As a demonstration, the
measured temporal response of the Mueller matrix and the retardance of a thick
liquid crystal variable retarder upon changing state is demonstrated.Comment: to be published in Journal of Modern Optics 20 pages, 6 figure
Future work on harmonics : some expert opinions part I : wind and solar power
A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. The results of this discussion are summarized in this paper and some of the issues are discussed in more detail in this paper and in its companion paper. This paper discusses emission from wind and solar power as well as advantages and disadvantages of active and passive filters
Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback
This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness
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