Analysis Of Frequency Characteristics Research Articles

Analysis of frequency characteristics of power system with wind farm-energy storage coordinated inertial control

With the increasing penetration level of wind power in the power system, the decoupling of wind turbine rotor speed and system frequency has led to the loss of the inertia of wind farms (WF), which can no longer be neglected. With the continuous development of energy storage (ES) technology, WF-ES coordinated inertial control has attracted attention as an effective means for wind turbines (WT) to participate in inertia response. How to build a WF-ES coordinated inertial control strategy and analyze system frequency characteristics has become a key research issue. In this paper, the frequency response model of a power system with WF-ES is established using the system frequency characteristic analysis method. The wind speed zones of the WF are taken into account, and different WF-ES control schemes are adopted under different wind speeds, aiming to ensure the active participation of WTs in the system frequency process across all wind speed conditions and effectively prevent frequency secondary drop. Finally, a power system frequency response simulation model is built in Matlab/Simulink to analyze the frequency characteristics of the power system with WF-ES coordinated inertial control and verify the feasibility of the proposed WF-ES coordinated inertial control strategy under various wind speeds.

Applying explainable artificial intelligence methods to models for diagnosing personal traits and cognitive abilities by social network data

This study utilizes advanced artificial intelligence techniques to analyze the social media behavior of 1358 users on VK, the largest Russian online social networking service. The analysis comprises 753,252 posts and reposts, combined with Big Five personality traits test results, as well as assessments of verbal and fluid intelligence. The objective of this research is to understand the manifestation of psychological attributes in social media users' behavior and determine their implications on user-interaction models. We employ the integrated gradients method to identify the most influential feature groups. The partial dependence plot technique aids in understanding how these features function across varying severity degrees of the predicted trait. To evaluate feature stability within the models, we cluster calculated Shapley values. Our findings suggest that the emotional tone (joy, surprise, anger, fear) of posts significantly influences the prediction of three personality traits: Extraversion, Agreeableness, and Openness to Experience. Additionally, user social engagement metrics (such as friend count, subscribers, likes, views, and comments) correlate directly with the predicted level of Logical thinking. We also observe a trend towards provocative and socially reprehensible content among users with high Neuroticism levels. The theme of religion demonstrates a multidirectional relationship with Consciousness and Agreeableness. Further findings, including an analysis of post frequency and key text characteristics, are also discussed, contributing to our understanding of the complex interplay between social media behavior and psychological traits. The study proposes a transition from the analysis of correlations between psychological (cognitive) traits to the analysis of indicators of behavior in a social network that are significant for diagnostic models of the corresponding traits.

Investigating noise radiation pattern of railway bridges for urban rail transit

Noise from elevated railway bridges in urban areas has been causing severe environmental issues. To find the peak frequency of sound energy and thus develop targeted countermeasures for noise mitigation, policymakers need a better understanding of the noise characteristics of urban railway bridges during train passage. This study approaches this issue by combining transient dynamic analyses and acoustic finite element simulation. Our frequency characteristic analysis focused on two primary noise sources: wheel-rail noise and bridge-borne noise. We built a spatial noise model that predicts the radiated noise of urban railway bridges in both the active and planning stages. The results show that the wheel-rail noise peaked at 800 Hz, 1600 Hz, and 3150 Hz, while the bridge-borne noise peaked at 40 Hz, 50 Hz, 80 Hz, and 125 Hz. The validation results demonstrated that the developed noise spatial prediction model extended well to similar urban railway bridges.

Algorithm for identifying RLC parameters

The article discusses an algorithm capable of determining the substitution scheme of the investigated circuit and calculating the parameters of its elements without operator intervention, based on the admittance frequency characteristics. This algorithm enhances the functional capabilities of RLC meters and can be applied to solve practical problems related to identifying the substitution scheme of the investigated circuit. As an RLC meter measures the total resistance only at one or several fixed frequencies, obtaining an understanding of the substitution scheme from these measurements is challenging. To select the substitution scheme, an analysis of the impedance or admittance frequency characteristics is required. Typically, this analysis is performed manually and is time- consuming. The proposed algorithm automates the analysis of the admittance frequency characteristics. The algorithm associates values and the sequence of slopes of the admittance frequency characteristics with an array of known sequences and slope values for known substitution schemes. The calculation of substitution scheme parameters is based on the resonance frequencies and the heights of zero slopes. To minimize the impact of noise on result accuracy, a synchronous signal detection method is employed. The article introduces a criterion for assessing the algorithm's performance and conducts testing on several types of circuits. During testing, the relative error in calculating substitution scheme parameters was evaluated, with a maximum value not exceeding 6 %.

Frequency Characteristics Analysis of Remote Field Eddy Current Testing on Ferromagnetic Pipes

Pipes made of ferromagnetic alloys are widely installed in petrochemical plants and the steel plants. To implement non-destructive corrosion inspections on these pipes, remote field eddy current testing (ECT) which installs a search coil inside the pipe is a practical inspection method. Remote field ECT has the advantage of being able to detect external surface defects while the distance between the detection coil and the excitation coil is twice of the outer diameter of the testing pipe. Nevertheless, the inspection principle such as the frequency characteristics etc. of ECT signals have not been elucidated, inspection devices based on remote field ECT had not been employed widely. In this paper, we measured the frequency characteristics of ferromagnetic pipes with artificial outer surface defects by remote field ECT, and then detailed finite element analysis are carried out by using the nonlinear eddy current analysis to clarify the inspection principle of the remote field ECT. In both measurement and analysis, peak signal occurs directly under the defect and the optimal frequency range are the same. The phase angle of flux density due to the excitation current and flux density due to eddy current are found to greatly affect the frequency characteristics.

A Meander Delay System Design Using Caps-Triple GAN Optimized with the Remora Optimization Algorithm for IOT Application

In this manuscript, a Meander Delay System design using Caps-Triple GAN optimized with the Remora Optimization Algorithm (ROA) is proposed for the Internet of Things (IoT) application. For designing the Meander Microstrip Delay Line (MMDL) Antenna, the Capsule Triple generative adversarial network (Caps-Triple GAN) is used. The Caps-Triple GAN error and delay parameters are optimized using the ROA. Hence, the designed MMDL Antenna is available in the IoT application. The proposed method is executed in the commercial Sonnet software package. The performance of the proposed method is examined under performance metrics, such as delay time with resistance characteristic, one-step delay time resistance characteristic, delay time, one-step delay time, error, and speed. The prediction results of the proposed MMDL-CAPS-Triple GAN-ROA method predict lower delay times of 14.77%, 15.89%, and 11.50%, higher speed of 32.57%, 16.25%, and 8.44% compared with the existing methods, such as Prediction of the meander delay system parameters for internet-of-things devices utilizing a Pareto-optimal artificial neural network and multiple linear regression (MDS-ANN-MLR), Predicting the frequency characteristics of hybrid meander systems utilizing the feed-forward back propagation network (MDS-FFBPN), Frequency Characteristic Analysis of Meander Structures with Different Connecting Electrodes (MDS-MoM), respectively.

Frequency characteristics analysis of pipe-to-soil potential under metro stray current interference using continuous wavelet transform method

This study aims to investigate the impact of stray current interference from metro systems on the pipe-to-soil potentials of metallic pipelines, which is closely associated with stray current corrosion. The pipe-to-soil potentials were assessed using coupon testing, while in-situ measurement was conducted to measure the metro leakage currents. The collected field data from the pipe-to-soil potentials and metro leakage current measurements were subjected to a statistical analysis using Continuous Wavelet Transform (CWT) and linear correlation methods. The analysis revealed consistent dominant frequencies of interference at the same test point for both on-potentials and off-potentials conditions, as well as within different time periods. However, variations in dominant frequencies of interference were observed among test points along different sections of the pipeline. Notably, three primary test points exhibited frequencies of 8.3, 8.9, and 7.8 mHz, corresponding to the main interstation travel intervals of neighboring metro lines. Furthermore, the dominant period ranges of interference of metro stray current interference were found to align with the interstation travel interval ranges of the metro lines. When the OVPD acts, the leakage current of the metro station grounding system near the test point has a significant contribution to the amplitude of pipe-to-soil potential fluctuation. These findings highlight the significant role of interstation travel intervals in the periodicity of metro stray current interference. The identified dominant interference frequency ranges can be utilized to determine interference sources and evaluate the extent of metro stray current corrosion.

Implementation of Frequency Characteristics Technique in Ground Penetrating Radar to Identify Steam Vent

Ground Penetrating Radar (GPR) is a geophysical method that widely used and developed in a lot of fields because of the non-destructiveness and relatively high resolution of the method. Despite all that, this method can produce a biased result because of factors that could affect the anomaly. To prevent those, advanced analytical methods are used, one of them is frequency characteristic analysis technique. Frequency characteristic technique used GPR’s frequency content to then analyze it in frequency and time domain. The result is quantified in various characters of frequency. This technique is used to help identify steam vents in geothermal environment in Darajat, Garut. Finite difference time domain (FDTD) method is used to generate a synthetic model then we applied frequency characteristic technique to analyzed and compared with the field data to identify the property of steam vent. Based on the result, frequency characteristic technique can be used to help identify presence of a steam vent.

Simulation and Analysis of Harmonic High Voltage Filters for Wind Farm

With the rapid development of the wind power industry, the total installed capacity of wind power has increased dramatically worldwide, and a large number of wind power installations need to be connected to the grid. In wind turbines, voltage flicker due to output power fluctuations caused by wind speed changes, and the application of a Voltage Source Converter (VSC) cause harmonic richness and other power quality problems to become more and more prominent. In this regard, the research is focused on the harmonic and reactive current distribution, impedance frequency characteristics, and voltage distortion rate of several offshore wind farm access systems, including the establishment of a harmonic current simulation model of the offshore wind farm delivery system, simulation analysis of network impedance frequency characteristics, simulation analysis of harmonic currents, and proposed a preferred filtering scheme. Taking into full consideration the characteristic harmonics of the wind farm, the system resonance generated by the submarine cable and the background harmonic level of the power grid, combined with the simulation results of the harmonic voltage, harmonic current, and network impedance frequency characteristics of each node, the technical solution of adding a direct-mounted high-voltage filtering device to the 220 kV bus at the metering station is proposed, which can destroy the system resonance conditions of the 3rd to 6th times of the submarine cable. Various wind farms and system operating conditions are able to form a stable harmonic absorption point to avoid the problem of harmonic amplification.

Time–Frequency Characteristics Analysis and Diagnosis of Rotating Rectifier Faults in Multiphase Annular Brushless System

The excitation system with a multi-phase annular brushless exciter (MPABE) is widely used in large-capacity nuclear power plants. However, in field operation, the rotating rectifier of the excitation system often fails due to the damage of diodes, which can cause serious consequences in long-term operation. To better protect the rotating rectifier, accurate grasp of the characteristics after the rotary rectifier faults becomes essential. Since the rectifier rotates with the rotor at high speed, the rectifier fault cannot be monitored directly. However, it is feasible to monitor the fault according to the characteristics induced in the stator field winding of the MPABE. Hence, this paper makes a thorough theoretical analysis of the rectifier fault mechanism to obtain the time-domain and frequency-domain characteristics of the stator field current when the rectifier is under normal operation, one-tube open-circuit fault, one-phase open-circuit fault and two-phase open-circuit fault. Then a new rectifier open-circuit fault diagnosis method based on the time-frequency characteristics of the fault excitation current is proposed. The final prototype and field experiments show that this method is simple and reliable, which can be used to monitor and detect the rotary rectifier faults in MPABE system.

Dynamic Compensation Optimization and Frequency Characteristic Analysis for Contactless Energy Transfer Under Load Variations in Rotary Ultrasonic Machining

In rotary ultrasonic machining, contactless energy transfer (CET) converts power from an ultrasonic power supply to the ultrasonic transducers. Two-side compensation circuits improve the efficiency of this process, but the addition of secondary compensation causes problems such as dynamic imbalance. Load changes affect the performance of CET system (CETS) with compensation, and dynamic compensation is needed for good CETS performance, such as high transfer efficiency and output power. This article investigates the frequency characteristics of CETS without compensation under different loads. The effects of two-side compensation on CETS under load variations is studied for the dynamic compensation characteristic. The comparison of mathematical model and performance of CETS with dynamic compensation are investigated to propose the optimized dynamic compensation. The model of CETS with optimized dynamic compensation under load variations is developed. The CETS frequency characteristics with optimized dynamic compensation are studied. The experimental results basically agree with the calculated results. The CETS with optimized dynamic compensation at the series resonant frequency can produce high transfer efficiency, high output power, low input impedance range under load variations in the cutting process of RUM, and solves the problems caused by the secondary side compensation.

FLEXIBLE POLYMERIC CHARCOAL-CONTAINING
 ELECTROMAGNETIC RADIATION ABSORBERS
 FOR PROVIDING ELECTROMAGNETIC COMPATIBILITY OF RADIOELECTRONIC DEVICES

Process research results of creating polymer charcoal-containing electromagnetic radiation absorbers by adding powdered coal (coconut activated, wood activated and non-activated) to the composition of polyurethane mastic for reducing the reflection coefficient of electromagnetic radiation in order to ensure the electromagnetic compatibility of radioelectronic devices are presented in the article. A technique for creating charcoal-containing electromagnetic radiation absorbers has been developed, according to which single-layer, two-layer and three-layer carbon-containing electromagnetic radiation absorbers samples have been obtained. The structure of coal particles and the mechanism of their distribution in polyurethane mastic have been studied. Based on the analysis of reflection and transmission coefficients frequency characteristics in the frequency range 3–17 GHz, the optimal layers position and their composition was determined to obtain the optimal shielding level for radioelectronic devices from electromagnetic interference and ensuring electromagnetic compatibility.

Модель инвертора напряжения для анализа частотных характеристик

The purpose of this work is issues related to the design of the control circuit of the energy converter, where the developed model can be considered as a tool for research and analysis of frequency characteristics. The object of the study is a stabilized voltage source based on a bridge converter with an LLC-resonant circuit, designed for the needs of industrial equipment. The first part of the work look is devoted to constructing the Bode diagram of the transducer based on experimental data and comparing the obtained results with calculated curves. In the second half of the work, a computer model of a closed control loop is presented.

PROGRESS IN THE STUDY OF DECAMETER-WAVELENGTH SOLAR RADIO EMISSION WITH UKRAINIAN RADIO TELESCOPES. Part 1. (Invited paper)

Subject and Purpose. Results are presented of the solar corona investigations performed with the world famous Ukrainian radio telescopes. The work has been aimed at offering a consistent review of recent achievements in observations of a variety of low-frequency radio emissions from the Sun. Methods and Methodology. The studies of the quiet (thermal) and sporadic (burst-like) radio emissions from the Sun have been car- ried out with the decameter-wavelength radio telescopes UTR-2, GURT and URAN-2. Specific features of the low-frequency solar radio emissions from a variety of sources are presented, with characterization of the optimized techniques that were applied in each case for evaluating physical parameters of the corona in the areas of decameter-wavelength radio wave generation. Results. The analysis of temporal, frequency and spatial characteristics of solar radio emissions has allowed suggesting a number of models for the coronal electron density distribution, and evaluating magnetic field strengths in the corona. Also, our experimental results have proven to be consistent with the observational data obtained in different frequency ranges and with the use of both ground based and space-borne instruments. Conclusions. The radio observations performed with Ukrainian radio telescopes have permitted studying, with high temporal, fre- quency and spatial resolutions, solar radio frequency emissions from various localized sources. Along with the large effective area and high sensitivity of the antennas, this permits application of a wide range of methods and tools aimed at detecting and analyzing solar bursts, of both strong and weak intensity, against the background of terrestrial interference of natural or artificial origin

A time-frequency approach to ensuring stability of machining by turning

This paper reports a new approach to ensuring the stability of the turning process, which is based on the frequency-time characteristics of the technological machining system (TMS). The approach uses a mathematical model of the turning process as a single-mass system with one degree of freedom, taking into account negative feedback on the normal coordinate and positive feedback with a delay in cutting depth. A new criterion for the stability of the cutting process as a system with a delay in positive feedback is proposed, based on the analysis of frequency characteristics in the form of a Nyquist diagram. It is proved that such a system will be stable when the chart of its Nyquist diagram does not cover a point with coordinates [+1, 0] on the complex plane. The validity of the new criterion has been confirmed by comparing the simulation results in the time range with the location of the Nyquist diagram on the complex plane. Based on the new criterion of stability, an algorithm for automatic construction of a Stability Lobes Diagram (SLD) has been developed. The necessary a priori parameters of TMS, the ranges of frequency change, and the calculation step for constructing such a characteristic in the coordinates "cutting depth – spindle rotational speed" have been determined. The adequacy of the obtained results is confirmed by a full-scale experiment to assess the roughness of machined parts under cutting modes that fall into the area of stability and instability on the SLD chart. The full-scale experiment proved the possibility of a significant reduction in roughness according to the Rz parameter, from 43 µm to 18 µm, while increasing productivity by 1.28 times. The use of a stability lobes diagram is especially effective when programming CNC lathes where it is possible to select the spindle speed in a wide range.

Frequency Characteristic Analysis of Acoustic Emission Signals of Pipeline Leakage

The leakage detection of a water distribution system (WDS) needs the support of a large number of field data. This paper collected over 6800 leak detection signals from cast iron pipelines used in a WDS. We found that 3280 signals indicated leakage, and the remaining indicated no leakage. The characteristics of the signals were extracted and analyzed from three perspectives: the central frequency of the power spectrum, the spectral roll-off rate, and the spectral flatness. Significant statistical distributions were found. The central frequencies of the leakage signals followed the normal distribution, and their spectral roll-off rates demonstrated the Burr distribution; the Birnbaum–Saunders distribution could describe the spectral flatness of the signals. Based on these characteristics, the recognition rate of the ML model for leak detection was improved. The Random Forest model was used to classify the leakage detection signals. The recall rate was 100%, and the false positive rate was 8.27%.

Longitudinal Aerodynamic Parameter Identification for Blended-Wing-Body Aircraft Based on a Wind Tunnel Virtual Flight Test

The wind tunnel virtual flight test realizes the dynamic semi-free flight of the model in the wind tunnel through the deflections of the control surface and uses the test data to identify the aerodynamic derivatives. The difference in dynamics between the wind tunnel virtual flight and the free flight leads to discrepancies between the identification and theoretical results. To solve the problems, a step-by-step identification and correction method for aerodynamic derivatives is established based on the difference between the equations of motion of wind tunnel virtual flight and free flight to identify and correct the lift, drag derivatives, pitch moment derivatives, and velocity derivatives, respectively. To establish an aerodynamic parameter identification model, the flight dynamics equation is expressed as a decoupled form of the free flight force and the influence of the test support frame force on the model’s motions through linearization. To ensure the identification accuracy of each aerodynamic derivative, an excitation signal design method based on amplitude–frequency characteristic analysis is proposed. The longitudinal aerodynamic parameter identification results of a blended-wing-body aircraft show that identification results with higher accuracy can be obtained by adopting the proposed identification and correction method.

Numerical analysis of frequency characteristics of transmitted waves by random waveguide

The frequency characteristics of the transmitted waves by the two-dimensional single-mode waveguide with a slightly rough boundary are investigated in detail. Two realizations of the waveguide with random rough boundaries are considered. Since the boundary element method based on the guided-mode extracted integral equation is employed, the boundary condition on the random rough boundary is accurately satisfied. It is found that the strong resonances with high Q-factor are created close to the cutoff frequency of the second-mode in the waveguide and they cause the small transmission (high reflection). It is shown that the Q-factors of these resonances increase with a decrease in the rms of the rough boundaries. It is shown that the rough boundary whose rms is about several thousand times smaller than the wavelength creates a strong enhanced electric field whose intensity is about several hundred times larger than that of the incident mode.

Fractal Impedance Element Synthesis Based on Multilayer Resistance-Capacitance Environment with C-R-Nc Layer Structure

The idea of fractural calculus appeared almost at the same time as the development of conventional differential calculus began. However, modern scientists became familiar with it only from pioneering works of B. Mandelbrot on fractal geometry of nature in 1980s. Since then, numerous scientific works were published on various aspects of fractural calculus and its application in science and engineering, and the interest to this area remains high. However, for physical implementation of fractural integration operators two-terminal elements with fractional power and frequency law (the fractural impedance elements - FIE) are required. Commercial FIE that could be produced industrially have not been developed so far. The greatest potential, in this case, have FIE built on the basis of multilayer resistance-capacitance element with distributed parameters (RC-distributed elements). One of the baseline designs of such FIEs with R-C-NR layer structure was manufactured as a prototype model. However, when manufacturing and testing of this element, flaws that may prevent its application were detected. The article suggests making FIE based on RC-distributed elements with dual C-R-NC layer structure where, as it is assumed, it is possible to avoid flaws found in FIE with R-C-NR layer structure. However, to solve this problem it is necessary to develop an algorithm and a program of structure synthesis of new type FIE enabling production elements with parameters not worse than those of the existing FIE with R-C-NR layer structure. For this purpose, an algorithm of frequency characteristic analysis of equivalent circuit FIE based on RC-distributed parameters having C-R-NC layer structure and being the component of synthesis algorithm, was developed. Principal stages of synthesis algorithm based on search optimization genetic algorithm were formulated. Ways of information coding of internal structure and parameter C-R-NC FIE were defined. Method of function calculation of individual fitness within population of object representation and ways of genetic operators (selection, crossing-over and mutation) realization in the process of genetic algorithm performance was described. Thereupon the synthesis program was developed and the results of its operation are given in the article. Synthesis result validity was verified by means of circuit simulation software OrCAD by application of Pspice-based C-R-NC-line model. The obtained FIE equivalent circuits integral C-R-NC structures, taking into account chosen materials and layer parameters, were designed. Comparative analysis results of synthesis program operation of C-R-NC FIE and R-C-NR FIE for synthesis FIE with the same requirements to frequency impedance FIE characteristics are given, showing that synthesizing C-R-NC FIE; the FIE with phase uniformity phase-frequency impedance characteristics from - 45° to about - 80° without galvanic coupling between poles and synthesizing R-C-NR FIE, the FIE with phase uniformity of phase-frequency impedance from -10° to about -45° with galvanic coupling between the pole are more likely to be realized.

Reduced Model of Droop-controlled Converters for Transient Simulation Analysis

In recent years, the transient stability problems encountered by power grids have increasingly attracted interest due to the connection of renewable energy resources. One of the effective methods for studying the transient characteristics of a system is transient simulation analysis. To reduce the simulation time, especially in a system with numerous renewable energy resources, model reduction has been widely employed. However, when a general reduced model is adopted to analyze different transient characteristics, a tradeoff between accuracy and simulation speed emerges. In this study, reduced model selection is implemented to resolve this problem. Considering the droop-controlled converter as an example, this approach allows the transient simulation analysis of voltage, frequency, and power angle characteristics. First, a full-order model of the droop-controlled inverter is formulated. Thereafter, the singular perturbation method is applied to derive different reduced-order models. Then, considering accuracy and simulation speed simultaneously, the most suitable reduced models for transient angle, voltage, and frequency simulation analyses are determined through time-domain simulation comparison. Finally, the simulation results based on Matlab/Simulink are used to verify the correctness of the reduced model selection.