Line Coupling Effects Research Articles

A Novel Scalable and Reliable Control for DC Microgrids With Varying Number of Agents.

Existing scalable control methods mainly rely on a fixed block-diagonal structure for the Lyapunov matrix, potentially resulting in numerical infeasibility issues. To overcome this limitation, this article proposes a novel scalable and reliable control scheme for dc microgrids. Initially, a general model for dc microgrids is established to enhance reliability, considering scenarios involving loss of control effectiveness (LoCE) and offset faults. Subsequently, a structured free-weight matrix technique is introduced to mitigate negative coupling effects of power lines, and to address numerical infeasibility by avoiding the assumption about the Lyapunov matrix. Furthermore, the stability of the entire dc microgrid is guaranteed by checking local agent conditions, independently of power line couplings. Therefore, the proposed control scheme ensures plug-and-play scalability with varying number of agents. Finally, theoretical results are validated through numerical simulations using the MATLAB/SimPowerSystems toolbox.

The j and k dependencies of the line coupling and line mixing effects: Theoretical studies of the relaxation matrices of N2-broadened CH3D

Line coupling and line mixing effects in parallel and perpendicular bands of CH3D perturbed by N2 have been studied. The work focuses on exhibiting the j and k dependencies of these two processes. The calculations were based on a previously reported anisotropic intermolecular potential including both the long-range multipole, induction, and dispersion forces and a short-range atom-atom model. It is shown that components with L1 = 3 of the atom-atom model are dominant contributions to the diffusion operator. As a consequence, in comparison with other molecular systems such as the CH3Cl-N2 and CH3I-N2, theoretically predicted line coupling and line mixing effects exhibit completely new j and k dependencies. In general, the theoretically calculated halfwidths and intra-doublets’ off-diagonal elements of the relaxation matrix are in reasonable agreement with measurements.

Line coupling and line mixing effects on calculated widths of symmetric-top molecules with the k-degeneracy: A theoretical study of N2-, O2-, and air-broadened lines of CH3I

Calculations of the N2-, O2-, and air-broadened widths, together with their temperature dependence exponents have been made for transitions of CH3I in the ν5 and ν6 bands. The calculations are based on a semi-classical line shape formalism developed by the current authors through modifying and refining the Robert-Bonamy formalism. In recent years, we have applied this formalism for linear molecules, symmetric-top molecules with inversion symmetry, and asymmetric-top molecules. For symmetric-top molecules with the k degeneracy such as CH3I, the formalism has a new feature. In this case, one should consider each of the CH3I transitions labeled by ki or f ≠ 0 as a doublet. Then, one needs to consider the effects of the line mixing process between these two components. Comparisons of our theoretical predictions with some data available demonstrate a very reasonable agreement. Finally we propose new experiments at higher perturber pressures that would enable one to check the theoretically calculated relaxation matrices and to extend the analysis to the inter-doublet mixing effects.

Theoretical study of CH3Cl-N2 line shapes in the ν1 band. Line mixing effects in QR doublets and QQk sub-branches

Line coupling and line mixing effects of CH3Cl lines in the ν1 band perturbed by N2 have been investigated. We have taken into account the non-diagonality of the exp(−S2) operator within specified line spaces as well as the k-degeneracy of the transitions (due to the double degeneracy of the j,k levels with k ≠ 0). These transitions should be considered as doublets coupled by the line mixing process. A new problem appears in the calculation when the atom-atom potential model is introduced. In order to overcome this difficulty, a pragmatic approach is proposed. Comparisons of theoretically calculated matrix elements of W with measurements of QR(j,k) doublets as well as some QQk sub-branches, which are strongly affected by line mixing, have been made. The results show that the formalism improved in this way leads to rather accurate predictions.

Simultaneous Single-Event Transient (SET) Observation on LM139A Wired-and Comparator Circuit

The sensitivity of the LM139A quad voltage comparator toward simultaneous single-event transient has been investigated through laser single photon absorption. The results have been supported and compared to heavy-ion tests. The analysis of sensitivity leads to the observation of two sensitive cases related to internal charge-sharing mechanism between comparator function and input line coupling effects.

Novel Fault Location Method for Power Systems Based on Attention Mechanism and Double Structure GRU Neural Network

Fault location is one of the most essential techniques to maintain the stable operation of power systems. A fast and accurate fault location allows operators to restore power grids faster and avoid economic losses. Conventional methods rely on expert knowledge to extract the necessary features (e.g. DWT, DFT). For large systems, more coupling effects of transmission lines require more complex feature engineering, and incomplete features can easily introduce large errors. To overcome this, a deep learning approach without manual feature extraction is introduced to the fault location model under big data application. Towards this end, in the proposed method, the attention mechanism, the Bi-GRU and a dual structure network are applied to analyze the current data from different perspectives. Complete information for the fault features is extracted for the fault location. Based on a time series model and benefit from the ability to internally acquire the information architecture of faulty line, the established model is adaptive to the power grids with very complex topologies. Simulation results indicate that the proposed double-structure model reduces the maximum error and is less affected by noise. In comparison with different structures and different models, the proposed method shows better performance in IEEE 39-bus system.

Holomorphic embedding load flow for unbalanced radial distribution networks with DFIG and tap‐changer modelling

In this study, the holomorphic-embedding method as a linear and non-iterative method is developed and implemented to solve the load flow of the three-phase unbalanced radial distribution networks. Previously, this method was used to solve the load flow problem of balanced transmission networks. The proposed methodology could be applied for a variety of unbalanced radial distribution networks with any number of buses and branches. The characteristics of unbalanced radial distribution networks including line coupling effects, unbalanced loads and unsymmetrical phases are considered in this study. The proposed method uses an unbalanced network structure and modifies the calculation approach of the admittance matrix. In this manner, an unbalanced network is modelled the same as the balanced networks. The tap-changer, doubly-fed induction generator (DFIG), and photovoltaic system are modelled in the admittance matrix or current injection vector. The performance of the proposed method is validated on the 19-bus unbalanced radial distribution network. Finally, the effectiveness of the proposed method in solving the load flow problem is investigated.

Relaxation matrix for symmetric tops with inversion symmetry: Line coupling and line mixing effects on NH3 lines in the 𝝂4 band.

Line shape parameters including the half-widths and the off-diagonal elements of the relaxation matrix have been calculated for self-broadened NH3 lines in the perpendicular ν4 band. As in the pure rotational and the parallel ν1 bands, the small inversion splitting in this band causes a complete failure of the isolated line approximation. As a result, one has to use formalisms not relying on this approximation. However, due to differences between parallel and perpendicular bands of NH3, the applicability of the formalism used in our previous studies of the ν1 band and other parallel bands must be carefully verified. We have found that, as long as potential models only contain components with K1 = K2 = 0, whose matrix elements require the selection rule Δk = 0, the formalism is applicable for the ν4 band with some minor adjustments. Based on both theoretical considerations and results from numerical calculations, the non-diagonality of the relaxation matrices in all the PP, RP, PQ, RQ, PR, and RR branches is discussed. Theoretically calculated self-broadened half-widths are compared with measurements and the values listed in HITRAN 2012. With respect to line coupling effects, we have compared our calculated intra-doublet off-diagonal elements of the relaxation matrix with reliable measurements carried out in the PP branch where the spectral environment is favorable. The agreement is rather good since our results do well reproduce the observed k and j dependences of these elements, thus validating our formalism.

Vibrational dependence of line coupling and line mixing in self-broadened parallel bands of NH3

Line coupling and line mixing effects have been calculated for several self-broadened NH3 lines in parallel bands involving an excited ν2 mode. It is well known that once the ν2 mode is excited, the inversion splitting quickly increases as this quantum number increases. In the present study, we have shown that the ν2 dependence of the inversion splitting plays a dominant role in the calculated line-shape parameters. For the ν2 band with a 36cm−1 splitting, the intra-doublet couplings practically disappear and for the 2ν2 and 2ν2 - ν2 bands with much higher splitting values, they are completely absent. With respect to the inter-doublet coupling, it becomes the most efficient coupling mechanism for the ν2 band, but it is also completely absent for bands with higher ν2 quantum numbers. Because line mixing is caused by line coupling, the above conclusions on line coupling are also applicable for line mixing. Concerning the check of our calculated line mixing effects, while the present formalism has well explained the line mixing signatures observed in the ν1 band, there are large discrepancies between the measured Rosenkranz mixing parameters and our calculated results for the ν2 and 2ν2 bands. In order to clarify these discrepancies, we propose to make some new measurements. In addition, we have calculated self-broadened half-widths in the ν2 and 2ν2 bands and made comparisons with several measurements and with the values listed in HITRAN 2012. In general, the agreements with measurements are very good. In contrast, the agreement with HITRAN 2012 is poor, indicating that the empirical formula used to predict the HITRAN 2012 data has to be updated.

The relaxation matrix for symmetric tops with inversion symmetry. II. Line mixing effects in the ν1 band of NH3.

Line mixing effects have been calculated in the ν1 parallel band of self-broadened NH3. The theoretical approach is an extension of a semi-classical model to symmetric-top molecules with inversion symmetry developed in the companion paper [Q. Ma and C. Boulet, J. Chem. Phys. 144, 224303 (2016)]. This model takes into account line coupling effects and hence enables the calculation of the entire relaxation matrix. A detailed analysis of the various coupling mechanisms is carried out for Q and R inversion doublets. The model has been applied to the calculation of the shape of the Q branch and of some R manifolds for which an obvious signature of line mixing effects has been experimentally demonstrated. Comparisons with measurements show that the present formalism leads to an accurate prediction of the available experimental line shapes. Discrepancies between the experimental and theoretical sets of first order mixing parameters are discussed as well as some extensions of both theory and experiment.

The influence of experimental uncertainties in the measured gas pressures and wavenumber scale calibration on multispectrum fitting results

The paper considers the artificial corrections of measured gas pressures and wavenumber scale shifts for multispectrum fit by the example of R(22) carbon dioxide self-broadened line of 30013←00001 vibrational band. For this purpose the two quadratic and hypergeometric speed-dependent Voigt line profile models including line mixing within the (Rosenkranz) first-order approximation for line-coupling effects with linear dependences of corresponding model parameters on pressure were applied. The intercomparison of the retrieved results only for pressure corrections, only for wavenumber scale shifts, for both together, and for no correction case demonstrates considerable disagreement between them. The most significant differences in parameters, retrieved in such a way, belong to the first-order line-mixing coefficients and are caused mostly by the shift scattering of wavenumber scale at different pressures.

A Miniaturized Frequency Reconfigurable Antenna With Single Bias, Dual Varactor Tuning

Frequency reconfigurable antenna designs often suffer from limited tuning ranges and complex bias networks. This paper describes a dual varactor-tuned miniaturized antenna with a single bias introduced through the RF feed that addresses these challenges. The dual varactors provide a large tuning range (410-990 MHz, 2.1-3.5 GHz; VSWR = 2:1), while the single bias voltage applied to both varactors greatly simplifies the bias network. The introduction of the bias through the RF feed eliminates the need for separate bias lines. As a result, when the electrical size of the antenna is decreased through tuning, undesired bias line coupling and radiation effects are nonexistent. The design highlights the radiation efficiency limitations associated with the desirable planar topology for electrically small antennas with very wide tuning range requirements. An overview of the antenna's geometry and operation is presented along with detailed measurements to characterize its performance.

Line interference effects using a refined Robert-Bonamy formalism: The test case of the isotropic Raman spectra of autoperturbed N2

A symmetrized version of the recently developed refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] is proposed. This model takes into account line coupling effects and hence allows the calculation of the off-diagonal elements of the relaxation matrix, without neglecting the rotational structure of the perturbing molecule. The formalism is applied to the isotropic Raman spectra of autoperturbed N2 for which a benchmark quantum relaxation matrix has recently been proposed. The consequences of the classical path approximation are carefully analyzed. Methods correcting for effects of inelasticity are considered. While in the right direction, these corrections appear to be too crude to provide off diagonal elements which would yield, via the sum rule, diagonal elements in good agreement with the quantum results. In order to overcome this difficulty, a re-normalization procedure is applied, which ensures that the off-diagonal elements do lead to the exact quantum diagonal elements. The agreement between the (re-normalized) semi-classical and quantum relaxation matrices is excellent, at least for the Raman spectra of N2, opening the way to the analysis of more complex molecular systems.

Line coupling effects in the isotropic Raman spectra of N2: a quantum calculation at room temperature.

We present quantum calculations of the relaxation matrix for the Q branch of N2 at room temperature using a recently proposed N2-N2 rigid rotor potential. Close coupling calculations were complemented by coupled states studies at high energies and provide about 10,200 two-body state-to state cross sections from which the needed one-body cross-sections may be obtained. For such temperatures, convergence has to be thoroughly analyzed since such conditions are close to the limit of current computational feasibility. This has been done using complementary calculations based on the energy corrected sudden formalism. Agreement of these quantum predictions with experimental data is good, but the main goal of this work is to provide a benchmark relaxation matrix for testing more approximate methods which remain of a great utility for complex molecular systems at room (and higher) temperatures.

Measurements and modelling of high pressure pure CO 2 spectra from 750 to 8500 cm −1. I—central and wing regions of the allowed vibrational bands

Precise modelling of infrared absorption by carbon dioxide is of primary importance for radiative transfer calculations in CO 2-rich atmospheres like those of Venus and Mars. Despite various measurements and theoretical models dedicated to this subject, accurate data at different temperatures and pressures are still lacking in numerous spectral regions. In this work, using two Fourier Transform Spectrometers, we have measured spectra of pure CO 2 in a large spectral region range, from 750 to 8500 cm −1 at various densities (3–57 amagat) and temperatures (230–473 K). Comparisons between measured dipolar absorption bands and spectra calculated with the widely used Lorentz line shape show very large discrepancies. This result is expected since the Lorentz approach neglects line-coupling effects due to intermolecular collisions which transfer absorption from the wings to the band center. In order to account for this effect, a theoretical approach based on the impact and Energy Corrected Sudden approximations has been developed. Comparisons of this model with numerous laboratory spectra in a wide range of pressure, temperature and spectral domain show satisfactory agreements for band centers and near wing regions where the impact approximation is valid. However, as expected, due to the breakdown of the impact approximation, the model fails when considering far wing regions. In the absence of precise models accounting for line-mixing and finite collision duration (non impact) effects, empirical approximations are proposed in order to model the far wings.

Formal derivation of optimal active shielding for low-power on-chip buses

Passive shielding has been used to reduce the capacitive coupling effects of adjacent bus lines by inserting passive ground or power lines (shields) between them. Active shielding is another shielding technique in which the shield is allowed to switch depending on the switching pattern of its adjacent bus lines. This paper formally derives the optimal active shielding logic function for minimum power dissipation. It is also shown that this optimal active shielding architecture depends on the ratio of coupling to ground capacitance (/spl gamma/=C/sub c//C/sub g/). Optimal active shielding is shown to provide up to 25% reduction in bus power dissipation compared to conventional passive shielding. A suboptimal active shielding architecture with simpler hardware is also proposed. Theoretically, using the suboptimal shielding architecture leads to less than 6% bus power penalty compared to the optimal active shielding logic circuit. However, due to the simpler shield encoding circuitry, simulation results show that the suboptimal active shielding architecture leads to higher overall energy savings compared to the optimal active shielding architectures.

Forward degenerate four-wave-mixing spectra of NO in the strong-field regime including polarization, line coupling, and multipole effects. I. Theory

In the present paper, we investigate the saturation mechanism of FDFWM (forward degenerate four-wave-mixing) spectra, observed with different polarizations of the input beams, line coupling, and Doppler effect. Our theoretical approach uses a nonperturbative resolution of the density matrix equations, decomposed on the irreducible tensor basis. This formalism greatly simplifies analytical expressions and allows for a correct treatment of magnetic sublevels structure in a three-J level system. Systematic calculations of the FDFWM signal for specific NO lines are performed to characterize intensities and line shapes as a function of saturation. Relative intensities exhibit strong changes in the intermediate regime of saturation further supporting the necessity for using such a complete model. Under saturating conditions, line coupling is shown to distort the spectra, according to the type of transition and the polarization configuration. This effect is observed in the following paper [V. Kr\uger et al., paper II, Phys. Rev. A 2001 (to be published)], where saturated experimental spectra of NO are presented and interpreted for two polarization configurations of interest for diagnostic purposes.

Forward degenerate four-wave-mixing spectra of NO in the strong-field regime including polarization, line coupling, and multipole effects. II. Experiments

The behavior of forward degenerate four-wave-mixing spectra of NO $\~A\ensuremath{-}\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{X}(0,0)$ in the presence of strong optical fields is observed for two crossed-polarization arrangements. The NO features in terms of coupled and isolated lines are interpreted with the complete model described in the preceding paper [V. Kr\"uger et al., paper I, Phys. Rev. 63, 012716 (2001)]. In the intermediate regime of saturation, the variation of relative line intensities with input energy is properly reproduced for NO. Thanks to these fits, we have been able to determine saturation threshold with a good accuracy. Important properties of the different polarization schemes are observed and discussed.

Practical inclusion of CO 2 line mixing effects in a line-by-line atmospheric retrieval system

A practical operational method is devised for computing air-broadened CO 2 line-coupling effects for least-squares estimation of the atmospheric state from IR spectra. Prior to operational data processing, a set of coefficients is derived that fully captures the line coupling effects within the impact approximation and a relaxation model. These coefficients are tabulated at reference temperature/pressure pairs, where they are computed from line pair relaxation rates, estimated using an exponential power energy-gap (PEG) law, the HITRAN values of line widths, and a parity-biased sum rule. The operational line-by-line retrieval software interpolates these tables to each atmospheric layer, and computes frequency-dependent absorption for the cluster of lines using the complex Voigt function. The time for computing the effects of coupling clusters of lines is thereby comparable to standard line-by-line processing on a per-line basis; no significant compute-time penalty is incurred, despite the fact that lines in clusters are fully coupled. The temperature and pressure dependence of the line coupling effects is shown to be acceptably accurate for several CO 2 Q-branches observed under conditions typical at the earth's surface and above, and is more rigorous and accurate than the first-order-in-pressure perturbation methods that have been reported elsewhere. Fully consistent partials of observed fluxes with respect to atmospheric parameters are computed and used successfully for least-square atmospheric retrievals.

Modeling of bipolar HVDC links in the harmonic domain

A method for accurate calculation of the harmonics generated by a bipolar HVDC link is described. The method illustrates the importance of including detailed representation of the mutual coupling effects of DC transmission lines, even when smoothing reactors are included. The overall solution is achieved by means of a unified Newton algorithm in the harmonic domain.