Resonance Mode Analysis Research Articles

Analysis of Fault Zone Resonance Modes Recorded by a Dense Seismic Array Across the San Jacinto Fault Zone at Blackburn Saddle

AbstractWe present observations and modeling of spatial eigen‐functions of resonating waves within fault zone waveguide, using data recorded on a dense seismic array across the San Jacinto Fault Zone (SJFZ) in southern California. The array consists of 5‐Hz geophones that cross the SJFZ with ~10–30 m spacing at the Blackburn Saddle near the Hemet Stepover. Wavefield snapshots after the S wave arrival are consistent for more than 50 near‐fault events, suggesting that this pattern is controlled by the fault zone structure rather than source properties. Data from example event with high signal to noise ratio show three main frequency peaks at ~1.3, ~2.0, and ~2.8 Hz in the amplitude spectra of resonance waves averaged over stations near the fault. The data are modeled with analytical expressions for eigen‐functions of resonance waves in a low‐velocity layer (fault zone) between two quarter‐spaces. Using a grid search‐based method, we investigate the possible width of the waveguide, location within the array, and shear wave velocities of the media that fit well the resonance signal at ~1.3 Hz. The results indicate a ~300 m wide damaged fault zone layer with ~65% S wave velocity reduction compared to the host rock. The SW edge of the low‐velocity zone is near the mapped fault surface trace, indicating that the damage zone is asymmetrically located at the regionally faster NE crustal block. The imaging resolution of the fault zone structure can be improved by modeling fault zone resonance modes and trapped waves together.

Study of resonance issues between DFIG-based offshore wind farm and HVDC transmission

Wide-frequency range of resonances can occur in HVDC-connected DFIG-based offshore wind farm (OWF), thus induce large harmonic distortion or endanger system stability. Previous studies usually treat OWF as a single-machine system without considering the switching states of individual wind turbines and collecting cables, or ignore the converter responses to wind speed variation and generation control order. In this paper, such factors are included in the modelling of OWF. Their impacts on resonance frequency, amplification level and the occurrence of negative damping are analyzed applying the resonance mode analysis method. Harmonic stability and power quality issues are demonstrated for the frequency range from several Hz to a few kHz. Simulations in MATLAB/Simulink validate the analytical results. Additionally, resonance damping strategies are discussed regarding the identified resonances in widely spread frequencies.

Resonant Mode Analysis on Wireless Power Transfer with Relay Coils

Resonant Mode Analysis on Wireless Power Transfer with Relay Coils

Lowest threshold lasing modes localized on marginally unstable periodic orbits in a semiconductor microcavity laser.

The lowest threshold lasing mode in a rounded D-shape microcavity is theoretically analyzed and experimentally demonstrated. To identify the lowest threshold lasing mode, we investigate threshold conditions of different periodic orbits by considering the linear gain condition due to the effective pumping region and total loss consisting of internal and scattering losses in ray dynamics. We compare the ray dynamical result with resonance mode analysis, including gain and loss. We find that the resonance modes localized on the pentagonal marginally unstable periodic orbit have the lowest threshold in our fabrication configuration. Our findings are verified by obtaining the path lengths and far-field patterns of lasing modes.

Analysis of resonance modes at harmonic frequencies in high-voltage networks

Analysis of resonance modes at harmonic frequencies in high-voltage networks

Magnetic properties of a spin-2 antiferromagnet with metal-radical hybrid spins

We present an $S=2$ antiferromagnet composed of a Mn-verdazyl complex $[\mathrm{Mn}{(\mathrm{hfac})}_{2}]\phantom{\rule{0.16em}{0ex}}[o\text{\ensuremath{-}}\mathrm{Py}\text{\ensuremath{-}}\mathrm{V}\text{\ensuremath{-}}{(4\text{\ensuremath{-}}\mathrm{F})}_{2}]$. An analysis of the magnetic behavior reveals that the strong antiferromagnetic intramolecular interaction between spins on ${\mathrm{Mn}}^{2+}$ and the verdazyl radical forms an $S=2$ hybrid spin below approximately 100 K. In the low-temperature regions, the magnetic susceptibility and the specific heat indicate a phase transition to the three-dimensional order of the $S$ = 2 system. Below the transition temperature, the magnetization curve exhibits a metamagnetic phase transition. From the analysis of electron spin resonance modes, we evaluate the on-site biaxial anisotropy responsible for the anisotropic magnetic behavior.

Анализ резонансных режимов в электроэнергетических системах с тяговой нагрузкой

Анализ резонансных режимов в электроэнергетических системах с тяговой нагрузкой

Resonance Modes at Harmonics Frequencies in Electrical Networks

Resonance modes at harmonic frequencies in electrical networks are a serious problem. They arise due to the availability of electrical equipment with capacitive and inductive elements. The values of the harmonics of currents and voltages increase at resonances. The voltage quality indices in resonant modes exceed the limit values. Harmonics cause energy losses in electrical equipment, reduce its service life, create economic damage. Capacitor banks are often damaged by resonances. Network nodes with resonant circuits and resonant harmonics can be determined using the frequency characteristics of the nodal reactance (susceptance). The paper presents an algorithm and HARMONICS software for the analysis and forecasting of resonance modes, the results of studies of resonance modes in the high-voltage networks of Eastern Siberia.

Optimal Positioning of Power Quality Meters for Monitoring Potential Conditions of Harmonic Resonances in a MV Distribution System

This research proposes an optimized allocation methodology of power quality (PQ) meters in medium voltage (MV) distribution system (DS), considering the potential harmonic resonance conditions. The allocation methodology uses the harmonic resonance mode analysis (HRMA) to calculate the critical modal impedances and identify the harmonic resonance frequencies. Thereby, using the HRMA, it is possible to build a binary observability matrix, which contains the information of nodes' observability for potential harmonic resonance frequencies. The allocation problem is modeled as a constraint integer linear programming that minimizes the number of necessary PQ meters, ensuring the complete observation of the determined harmonic resonance frequencies. The final feasible solution indicates the best locations to install the PQ meters, considering the harmonic resonance conditions, which include distinct operation scenarios of the DS, regarding the capacitor banks of the customers for power-factor correction. The allocation algorithm was applied in two test DSs, based on a CIGRÉ MV network and on the IEEE 34-node test feeder. The results show that four PQ meters are required to completely monitor the potential harmonic resonance frequencies in both the test DSs. It is also shown that the final allocation solution is applicable even for certain variability of the considered capacitor banks.

Empirical estimation approach to the study of inter-area resonance interactions in power systems

Studies to deal with the identification of inter-area resonance interactions by fault diagnosis and historical databases at interconnected power systems have led to the development of new methods to delimit and split resonant regions and their control area regulations. This paper contributes in employing the frequency-domain empirical orthogonal functions (EOFs) for the measurement-based analysis of the inter-area resonance modes and its neighborhood. This multi-resolution empirical approach, developed for multiple-input multiple-output (MIMO) systems, is considered to contribute in understanding the spatial orientation properties and the dynamical/physical behavior of inter-area resonance interactions. Also, the method contributes much in advancing our knowledge of inter-area phase-matching patterns (PMPs) modes and their phase shifts from large data sets. In order to demonstrate the usefulness of obtaining and delimiting neighboring areas with resonant interactions in interconnected power systems, the proposed method is numerically applied in detail to the IEEE 16-generator 68-bus test system.

Probabilistic Harmonic Resonance Assessment Considering Power System Uncertainties

The presence of power system uncertainties results in variations of the harmonic resonance behaviors. There is, therefore, a need to perform the probabilistic assessment in harmonic resonance study. In this paper, a systematic methodology for probabilistic harmonic resonance assessment considering power system uncertainties is presented. First, potential system uncertainties are analyzed and modeled. The stochastic behavior of harmonic resonance due to system uncertainties is then studied using both Monte Carlo approach and harmonic resonance mode analysis technique. A modified power iteration method is further used to efficiently reduce the calculation time. Three indices, including probabilistic expressions of 1) resonance frequency band, 2) modal impedances in the resonance band, and 3) sensitivity information at the bus-level and the element-level are used to represent the stochastic behaviors of harmonic resonance. In addition, the resonance mitigation scheme based on probabilistic resonance frequency band shift technique is described. The effectiveness of the proposed method is demonstrated through case studies in an uncertain power system. Its potential applications are also discussed.

Harmonic voltage measurement error of the capacitor voltage transformer.

This paper explores the mechanism for the harmonic voltage measurement error (HVME) of a capacitor voltage transformer (CVT) in a comprehensive way and develops a practical error correction method to improve the harmonic measurement performance of a CVT. The harmonic equivalent circuit (HEC) of CVTs with different types of dampers are established and the parameter value calculation methods of the circuit elements are presented. Characteristics of the individual inherent resonance mode of the HEC, including the resonant frequency, the resonant type and the circuit elements involved, are analyzed systematically. Centered on resonance mode formulation, an universal error correction method for CVTs in measuring harmonic voltage is proposed based on the piecewise fitting of the transformation ratio. A physical experimental platform available for low-voltage CVTs is developed in laboratory, which utilizes a 10-kV harmonic generator and a step-up transformer to provide harmonic signals with high voltage level. Moreover, a novel experimental scheme for testing the HVME of high-voltage CVTs is proposed based on alternating current/direct current (AC/DC) filters. Experiments are conducted on these experimental platforms to test the HVME of a 35-kV CVT in laboratory and a 525-kV CVT in a back-to-back DC converter station. The experimental results verify the validity of the built HECs of CVTs, the resonant mode analysis results and the resonant frequency calculation method. Finally, the effectiveness of the proposed harmonic error correction method is proved by several examples.

Overview of Harmonic and Resonance in Railway Electrification Systems

Harmonic distortion and harmonic resonance problems have been widely concerned and reported in railway electrification systems (RESs) due to the harmonic injection from the nonlinear electric train, especially high-speed/high-capacity/large-power trains. This paper presents an overview of the harmonic and resonance problems in the RES, including harmonic problem composition, harmonic modeling, available influential factors assessment, harmonic resonance, and associated suppression methods. The harmonic problem mainly consists of the background harmonics brought from the utility system, resonance-region harmonics interacted by capacitive and inductive network elements, and characteristic harmonics generated from the switching process of the onboard power conversion system. The mathematical modeling and analysis methods are introduced, including frequency scanning analysis, S-domain analysis, resonance mode analysis, and modal sensitivity analysis. Available influential factors/parameters have been fully investigated against above-mentioned harmonic problems. Finally, different harmonic suppression methods have been compared and summarized in this paper.

Magnetism and the phase diagram of MnSb2O6

Static and dynamic magnetic properties of P\={3}1$m$-phase MnSb$_2$O$_6$ have been studied by means of muon spin relaxation ($\mu$SR), high-frequency electron spin resonance (HF-ESR), specific heat, and magnetisation studies in magnetic fields up to 25\,T. The data imply onset of long-range antiferromagnetic order at $T_N$ =~8~K and a spin-flop-like transition at $B_{SF}\approx 0.7 - 1$~T. Below $T_N$, muon asymmetry exhibits well-defined oscillations indicating a narrow distribution of the local fields. A competing antiferromagnetic phase appearing below $T_2$ =~5.3~K is evidenced by a step in the magnetisation and a slight kink of the relaxation rate. Above $T_N$ , both $\mu$SR and HF-ESR data suggest short-range spin order. HF-ESR data show that local magnetic fields persist up to at least $12\cdot T_{\rm N}\approx 100$\,K. Analysis of the antiferromagnetic resonance modes and the thermodynamic spin-flop field suggest zero-field splitting of $\Delta \approx 18$\,GHz which implies small but finite magnetic anisotropy.

Application of Resonance Analysis to AC–DC Networks

Medium to long-distance underground ac lines and both short- and long-distance HVdc are frequently integrated into network expansion plans. In conjunction with growing numbers of power-electronic converters in the grid, there is a rising risk related to the effects of harmonic currents. Resonance analysis should therefore be part of power system expansion planning. In this paper, network harmonic modeling and analysis are discussed, in particular, power transformer and power converter frequency models are proposed. Frequency scanning and resonance mode analysis are compared and discussed. The changes in resonance response due to transmission network expansion are drawn. The methods are applied to the investigation of the impact of one link reinforcement, both ac and ac solutions, as well as the impact of the power transformer disconnection. The performed analysis enables finding the resonance location at each studied case. The frequency analysis methods presented in this paper enable forseeing network frequency behavior that is valuable for both network analysis and network expansion planning.

A Rapid Modal Analysis Method for Harmonic Resonance Using Modified Power Iteration

Resonance mode analysis based on eigenvalue decomposition is a very computing-intensive work in the frequency scan process. This letter presents a modified power iteration method for modal analysis to reduce the computing time. Simulation results verify that the proposed method possesses a faster computing speed by evidently eliminating the unnecessary iteration numbers.

Third Harmonic Generation Enhanced by Multipolar Interference in Complementary Silicon Metasurfaces

Nonlinear harmonic generation in metasurfaces has shown great promises for applications such as novel light sources, nonlinear holography and nonlinear imaging. In particular, dielectric metasurfaces have shown multi-fold enhancement of the harmonic efficiency in comparison to their plasmonic counterparts due to lower optical loss and much higher damage threshold. In this work, we propose to enhance the efficiency of the third harmonic generation in a complementary silicon nonlinear metasurface, consisting of nanoapertures of cross-like shape in the silicon film. The efficiency enhancement is based on a multipolar interference between the magnetic dipole and electric quadrupole, resulting in significant near-field enhancement and a large mode volume of the nonlinear interaction. The measured efficiency of third harmonic generation from the silicon metasurface is 100 times higher than that from a planar silicon film of the same thickness. Numerical analysis of the near-field resonant modes confirms the mul...

Frequency scans and resonance mode analysis for resonance problems identification in power networks in presence of harmonic pollution

Frequency scans and resonance mode analysis for resonance problems identification in power networks in presence of harmonic pollution

Low‐profile broadband circularly polarised patch antenna with gain enhancement

A low-profile broadband circularly polarised patch antenna with four parasitic patches (PPAs) is presented. The proposed antenna has the advantages of broadband reflection coefficient, broadband axial-ratio (AR) performance and low-profile structure. First, a broadband feed network is employed to realise wide reflection coefficient and AR bandwidths. To enhance the gain performance, two types of PPAs employing parasitic technique scheme are designed and compared. Then, resonance mode theories and simulated current distributions are utilised to explain the gain enhancement issue within the operating frequency. Furthermore, the designed antenna is optimised carefully by adopting parametric analysis before fabricating and measuring. Finally, the gain enhancement is verified by the measured results of designed antenna possessing the characteristic of both high-gain and low-profile structure. The results indicate that the adding PPAs scheme and the resonance mode analysis are helpful on research of this type of patch antenna.

On the qualitative analysis of nonlinear resonant modes in multidimensional structures

The resonant behavior of multidimensional structures simulated via strongly nonlinear dynamic systems has been studied. The energy balance principle has been applied for the qualitative analysis of these systems. The number of potential nonlinear resonant modes under periodic polyharmonic force and parametric excitation has been estimated. The dynamic effects have been investigated and examples have been provided.