Electromotive Force Technique Research Articles

Disturbance Rejection Through Adaptive Frequency Estimation Observer for Wind-Solar Integrated AC Microgrid

The renewable energy generation is the cornerstone component of the greener and cleaner ac microgrid. The high penetration of wind and solar photovoltaic energy sources in the distribution network causes unbalanced voltages, voltage rise, flicker, and internal and external uncertainties leading to disturbance and unreliable operation of the system. This paper presents the performance enhancement of the wind-solar integrated ac microgrid by implementing the adaptive frequency estimation observer (AFEO) aiming for disturbance rejection. The model uncertainties and unknown disturbances are taken care of by nonlinear active disturbance rejection controller based phase-locked loop in conjunction with the AFEO. No detailed mathematical model is required, instead the controller provides decent anti-interference and effortless parameter tuning. The fluctuations in power, interharmonics, current harmonics, and power quality (PQ) issues produced by wind and solar energy resource permeation into the grid, are addressed and mitigated by successful implementation of the AFEO for switching the grid side voltage source converter. The machine side converter obtains its switching pulses from vector control scheme. The encoderless speed and rotor position estimation of the synchronous generator (SG) driven by wind turbine is carried out by back electromotive force technique. The environmental variation of the wind and solar energy are overcome by utilizing perturb and observe scheme for optimal power extraction. Test results are obtained from the laboratory prototype under steady state and dynamic conditions including environmental changes, i.e., intermittent wind speed, solar insolation, and variable load conditions. PQ issues are addressed, investigated, and mitigated successfully.

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition.

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique.

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition.

Thermodynamic study of monoclinic pyrrhotite in equilibrium with pyrite in the Ag-Fe-S system by solid-state electrochemical cell technique

An equilibrium mixture of monoclinic pyrrhotite and pyrite was synthesized in the eutectic AlCl3- KCl melt at 525 K. The reaction 7FeS2(cr) + 12Ag(cr) = 8Fe0.875S(cr) + 6Ag2S(cr) was studied by an electromotive force technique in an all-solid-state electrochemical cell with an Ag+-conductive solid electrolyte in Ar at atmospheric pressure: (-) Pt | Ag | AgI | Ag2S, Fe0.875S, FeS2 | Pt (+). In the 490-565 K temperature range a linear electromotive force vs. temperature trend was obtained from which the temperature dependence of the sulfur fugacity was determined for the monoclinic pyrrhotitepyrite equilibrium: logfS2(mpo+py) = 14.079 - 14406⋅T-1, (500 < T/K < 565). In addition, standard thermodynamic functions were calculated for monoclinic pyrrhotite Fe0.875S at 298 K and atmospheric pressure: ΔGf(mpo, 298.15 K) = -(136 200 ± 3000) J/mol, S°(mpo, 298.15 K) = (66.7 ± 1.3) J/(mol-K), ΔHf(mpo, 298.15 K) = -(157 400 ± 3000) J/mol. Gaseous sulfur, S2-ideal gas at 1 bar (105 Pa) pressure- was taken as a standard state for sulfur.

Determination of standard thermodynamic properties of Sb2O3 by a solid-oxide electrolyte EMF technique

A solid oxide electrolyte galvanic cell has been employed to obtain the thermodynamic properties of antimony trioxide Sb2O3 in the temperature range from 782 to 1080K. Standard Gibbs energy of formation ΔfG°, the standard enthalpy of formation ΔfH°298 and standard entropy S°298 were obtained by the electromotive force (EMF) method. The experimental procedure has been improved in order to increase the accuracy of the existing thermodynamic data. The obtained results have been compared to the data gathered in the previous studies. The standard Gibbs energies of formation obtained from multiple galvanic cells are linear functions of temperature as:ΔfG°/kJmol−1=−679.82+0.235T/K±0.413 (782−903.65K) both phases are solidΔfG°/kJmol−1=−739.53+0.301T/K±0.502 (903.65−929.15K) Sb—liquid; Sb2O3—solidΔfG°/kJmol−1=−682.21+0.239T/K±0.419 (929.15−1080K) both phases are liquidThe standard enthalpy of formation ΔfH°298 (−709.74/kJmol−1) and standard entropy S°298 (124.05/J(molK)−1) were calculated for Sb2O3 using the measured values and cp functions given by previous studies.

Thermoelectric power and electrochemical studies on CdI2–Ag2O–V2O5–B2O3 system

A quaternary super-ion-conducting system, 20CdI2 − 80[xAg2O − y(0.7V2O5 − 0.3B2O3)] where 1 ≤ x/y ≤ 3, has been prepared by melt quenching technique. The electrical conductivity measured was the order of 10−4 S/cm at room temperature. The values of silver-ion transport number obtained by electromotive force technique are nearly unity. The thermoelectric power and electrochemical studies were done on the CdI2–Ag2O–V2O5–B2O3 system. The discharge and polarization characteristics were examined for different cathodes to evaluate the utility of these cells as power sources for low energy applications.

Dynamic and Impact Deformation Evaluation by Electromotive Force Technique

Dynamic and Impact Deformation Evaluation by Electromotive Force Technique

Control of a High-Speed Flywheel System for Energy Storage in Space Applications

A novel control algorithm for the charge and discharge modes of operation of a flywheel energy storage system for space applications is presented. The motor control portion of the algorithm uses sensorless field oriented control with position and speed estimates determined from a signal injection technique at low speeds and a back electromotive force technique at higher speeds. The charge and discharge portion of the algorithm use command feedforward and disturbance decoupling, respectively, to achieve fast response with low gains. Simulation and experimental results are presented demonstrating the successful operation of the flywheel control up to the rated speed of 60 000 r/min.

Activity coefficients of Dy dissolved in liquid Bi

Using an electromotive force technique, activity coefficients of Dy dissolved in liquid Bi in the 820–1101 K range and at Dy concentrations of 10 −5–10 −2 mole fractions have been determined. The dependence of activity coefficient on concentration for each investigated temperature was linear, and the activity coefficient increased with the temperature increase.

Electric-field correlation of femtosecond pulses by use of a photoelectromotive-force detector

A semiconductor photoinduced electromotive-force detector is used to measure the square of the electric-field correlation of nominal 100-fs laser pulses. For transform-limited pulses, this measurement gives the intensity correlation and thus directly gives the pulse width. The photoinduced electromotive-force technique using semi-insulating GaAs:Cr performs detection that is linear in intensity, making it possible to characterize weak femtosecond pulses with an average power of microwatts.

Electromotive force technique applied to the design of planar dielectric antennas with low side lobes

AbstractThe diffraction problem of a dominant surface mode scattering by a finite number of metal strips placed on a surface of a planar dielectric waveguide is considered. The electromotive force technique is utilized, and results concerning the analysis and design of beam antennas with low side‐lobe level at millimeter wavelength are presented. © 1994 John Wiley &amp; Sons, Inc.

Solubility of AgCl in Molten NaCl ‐ AlCl3 and KCl ‐ AlCl3

Measurements of solubility (in mol fraction units) in molten and were determined by an electromotive force technique. For the experiments, the temperature was maintained at 448 K and the composition of the solvent varied from . There was a compositional dependence of the solubilities with a minimum near the equimolar solvent composition. The minimum solubility in mol fraction of was at . The true solubility produce for at 448 K was calculated to be . The magnitude of the solubility product is primarily related to the fact that the standard free energy of formation of from and is about 67 kJ mol−1 more negative than the corresponding free energy for (i.e., is unstable). In basic and in somewhat acidic melts, the solubility is related to the formation of the associated ionic species such as ,, , and . From our measurements, the formation constant of at 448 K, , was . Further, the specific bond free energy for the associated complex , , has been calculated as −47.5 kJ mol−1. For the experiments, the composition was maintained at the equimolar and the temperature varied in the range 518 to 583 K. The solubility increases from at 518 K to at 583 K. The apparent heat of solution was 17.68 kJ mol−1 for this temperature range.