Journal articles: 'Phase-frequency characteristic'

1

Shakurskiy, M. V., and V. I. Volovach. "Mathematical model of digital frequency-sampling filters with shiftable phase-frequency characteristic." Radioelectronics and Communications Systems 59, no. 9 (September 2016): 397–401. http://dx.doi.org/10.3103/s0735272716090028.

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Cao, Xiaobin, Zhongmei Li, and Shiwei Yao. "Analysis on the Phase Frequency Characteristic of Soil Impedance." Energy and Power Engineering 10, no. 04 (2018): 17–24. http://dx.doi.org/10.4236/epe.2018.104b003.

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Паровик, Р. И. "Анализ добротности вынужденных колебаний дробного линейного осциллятора." Журнал технической физики 90, no. 7 (2020): 1059. http://dx.doi.org/10.21883/jtf.2020.07.49436.233-19.

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Using the harmonic balance method, analytical formulas are obtained for calculating the amplitude-frequency and phase-frequency characteristics, as well as the quality factor of the forced oscillations of a linear fractional oscillator. It was established that the characteristics under study depend on the dissipative properties of the medium - memory effects, which are described by derivatives of fractional orders. It is shown that fractional orders affect the attenuation of the oscillatory process and are associated with its quality factor. The calculated curves of the characteristics of the forced oscillations of a linear linear fractional oscillator showed that fractional orders can be considered as control parameters of the oscillatory process in a dissipative medium. Key words: quality factor, amplitude-frequency characteristic, phase-frequency characteristic, fractional derivatives, memory.

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Chu, Hai Rong, Bo Liu, and Yue Zhang. "Three-Loop Autopilot Frequency Characteristic Measurement." Applied Mechanics and Materials 494-495 (February 2014): 1332–34. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.1332.

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In order to measurement frequency characteristic of the missile three loop autopilot, three loop autopilot system model of the missile pitch channel was established. Then the autopilot system open-loop model was analyzed , and also open-loop frequency calculation formula was deduced. On the basis of the autopilot system model, half physical frequency characteristic measurement system was built, and the experimental data were processed by using correlation analysis method. Experimental results shows that when the time delay of measurement system was compensated, three loops autopilot actual cut-off frequency was 47.5rad/s, phase margin was 93°, amplitude margin was infinte, compared with the theoretical value, errors was less than 5%. The correctness of three loops autopilot frequency characteristic measurement method was verified.

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CHOI, MI-HYUN, and SOON-CHEOL CHUNG. "EXTRACTION OF COGNITIVE CHARACTERISTIC FUNCTIONS ACCORDING TO VARIOUS PARAMETER CHANGES OF VIBRATORY STIMULATION." Journal of Mechanics in Medicine and Biology 19, no. 08 (December 2019): 1940052. http://dx.doi.org/10.1142/s0219519419400529.

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In this study, vibratory stimuli with various intensities (four levels) and frequencies (10, 50, 100, 150, 200, 225, 250 and 300[Formula: see text]Hz) were applied to the right index finger to extract cognitive characteristic functions for the intensity and frequency. For subjective assessment, an experiment was conducted with 30 healthy adults in their twenties who were right-handed and had normal cognitive function. One trial of the experiment was composed of a vibration phase (0.1 s) and a rest phase (10 s). After vibration simulation was applied once for each intensity and frequency, the participants filled out a subjective assessment form. After extracting the score of each word, the cognitive characteristic function was derived through discriminant analysis and regression analysis according to the frequency and intensity. Through the cognitive characteristic function, the level of cognitive characteristics of each word can be investigated according to the influence of the frequency and intensity. The results observed through the cognitive characteristics function of each word showed that the words affected by the frequency and intensity were “light,” “thick,” “heavy,” “blunt,” “vibrating,” “fast” and “weak.” “Itchy” and “slow” were cognitive characteristics affected only by the frequency, and “strong” and “push” were affected only by the intensity. Through the vibratory stimulation presentation parameters, i.e., frequency and intensity, the results capable of predicting the degrees of various cognitive characteristics were presented.

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Dong, Jun, Zhong-gui Lu, Zhi-hong Sun, Zhi-tao Peng, Yan-wen Xia, Jing-qin Su, Feng Jing, Hao-yu Yuan, Hua Liu, and Jun Tang. "Transforming characteristic of phase-shift from frequency-domain to time-domain in frequency-domain holography." Optics & Laser Technology 44, no. 3 (April 2012): 594–99. http://dx.doi.org/10.1016/j.optlastec.2011.08.027.

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Parovik, Roman. "Frequency characteristics of the fractional oscillator Van der Pol." E3S Web of Conferences 127 (2019): 02010. http://dx.doi.org/10.1051/e3sconf/201912702010.

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Into this paper, the amplitude-frequency and phase-frequency characteristics of the Van der Polar fractional oscillator are studied in order to establish their relationship with the orders of fractional derivatives included in the model equation. Using the harmonic balance method, analytical formulas were obtained for the amplitude-frequency, phase-frequency characteristics, as well as the quality factor – the energy characteristic of the oscillatory system. It was shown that the quality factor depends on the orders of fractional derivatives, and change in their values can lead to both an increase and a decrease in the quality factor.

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Wei, Jin Cheng, and Jin Li. "Dynamic Modulus Characteristic of Large Stone Permeable Asphalt Mixtures." Applied Mechanics and Materials 423-426 (September 2013): 1110–13. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.1110.

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To study the dynamic modulus characteristic of LSPM mixes, dynamic modulus test was conducted for Large Stone Permeable Asphalt Mixtures (LSPM ) with neat asphalt and with modified asphalt and the range of dynamic modulus values for LSPM was determined and the dynamic modulus master curves were developed. The magnitude of the dynamic modulus decreased with an increase in temperature and increased with an increase in the frequency. The phase angle decreased as the frequency increased at low temperature. With temperature increase, there was a transition interval, where the phase angle increased up to frequencies of 0.5 Hz, and then it started to decrease as frequency increased. After the transition interval, the phase angle increased with an increase in frequency. Master curves developed by sigmoidal function showed that LSPM with modified asphalt exhibited higher dynamic modulus values at middle and high frequencies and lower dynamic modulus values at low frequencies.

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Иванов, В. В., Я. В. Еремина, and С. В. Ермолова. "Computer modeling of parametric converters with frequency and phase control." Informacionno-technologicheskij vestnik, no. 2(24) (June 17, 2020): 96–106. http://dx.doi.org/10.21499/2409-1650-2020-24-2-96-106.

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Осуществлено математическое моделирование параметрических преобразователей, использующих режим повышенной чувствительности. Названный режим преобразователей позволяет повысить эксплуатационные показатели аппаратуры авиационно-космических систем. Показано, что преобразователи с фазовым управлением обладают линейными характеристиками и являются более перспективны. Применение в них цифровых фильтров ведет к повышению стабильности частоты и точности настройки, а также минимизируется погрешность характеристики преобразования. Mathematical modeling of parametric converters using high-sensitivity mode is carried out. The named mode of converters allows to increase operational parameters of the equipment of aerospace systems. It is shown that phase-controlled converters are more promising because they have linear characteristics and allow the use of digital filters, which leads to an increase in frequency stability and accuracy of adjustment, and also minimizes the error of the conversion characteristic.

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Demyanov, Vladislav, Ekaterina Danilchuk, Yury Yasyukevich, and Maria Sergeeva. "Experimental Estimation of Deviation Frequency within the Spectrum of Scintillations of the Carrier Phase of GNSS Signals." Remote Sensing 13, no. 24 (December 10, 2021): 5017. http://dx.doi.org/10.3390/rs13245017.

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The term deviation frequency (fd) denotes the boundary between the variable part of the amplitude and phase scintillation spectrum and the part of uninformative noises. We suggested the concept of the “characteristic deviation frequency” during the observation period. The characteristic deviation frequency is defined as the most probable value of the deviation frequency under current local conditions. Our case study involved GPS, GLONASS, Galileo and SBAS data under quiet and weakly disturbed geomagnetic conditions (geomagnetic storm on 16 April 2021, Kpmax = 5, SYM-Hmin = −57 nT) at the mid-latitude GNSS station. Our results demonstrated that the deviation frequency for all signal components of GPS, GLONASS and Galileo varies within 15–22 Hz. The characteristic deviation frequency was 20 Hz for the mentioned GNSS signals. The SBAS differs from other systems: deviation frequency varies within 13–20 Hz. The characteristic deviation frequency is lower and equal to 18 Hz. We suggest the characteristic deviation frequency to determine the optimal sampling rate of the GNSS carrier phase data for the ionospheric studies. In turn, the deviation frequency can be considered as a promising index to estimate the boundary of non-variability of the ionosphere.

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Yoon, Youngkuk, and Seung Jin Song. "Mathematical verification of dual-frequency characteristic in rotating cavitations." Journal of Physics: Conference Series 2217, no. 1 (April 1, 2022): 012015. http://dx.doi.org/10.1088/1742-6596/2217/1/012015.

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Abstract Unlike other common rotating instabilities such as rotating stall, unsteady pressure measurement of inducer rotating cavitation had shown dual-frequency characteristic: the Fourier transformation of the pressure signals showed two distinct frequency peaks. It was assumed that the dual-frequency characteristic is originated from the non-linear interaction between the actual oscillation frequency of the cavity and the blade passing frequency. However, the manifestation of the rotating cavitation as dual-frequency peaks has only been observed experimentally and yet explained theoretically. Thus, based on the oscillating nature of the rotating cavitation, the present paper provides mathematical framework to show that the dual-frequency characteristics can be derived from the phase-locked oscillating cavities. The rotating cavitation is first expressed with respect to the rotating frame, and then transformed into the stationary frame to determine frequency peaks. The predicted frequency peak of the rotating cavitation unsteady pressure signal well captures the experimental results from previous research.

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Huo, Kai, Wei-dong Jiang, Xiang Li, and Jun-jie Mao. "A New OFDM Phase-coded Stepped-frequency Radar Signal and Its Characteristic." Journal of Electronics & Information Technology 33, no. 3 (March 16, 2011): 677–83. http://dx.doi.org/10.3724/sp.j.1146.2010.00532.

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NAKAHARA, Yuji, and Shinji TAMURA. "615 Phase characteristic of frequency response fUnction of 2-DOF Duffing oscillator." Proceedings of Conference of Chugoku-Shikoku Branch 2011.49 (2011): 159–60. http://dx.doi.org/10.1299/jsmecs.2011.49.159.

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Oxenham, Andrew J., and Stephan D. Ewert. "Estimates of auditory filter phase response at and below characteristic frequency (L)." Journal of the Acoustical Society of America 117, no. 4 (April 2005): 1713–16. http://dx.doi.org/10.1121/1.1863012.

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15

Huang, Wen, Tao Zheng, Shi Guang Xu, Zhi Yuan Liu, and Jing Hua Wen. "The Analysis of the Performance of Active Frequency Drift Islanding Method." Advanced Materials Research 846-847 (November 2013): 750–55. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.750.

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Active frequency drift islanding detection method is one of most widely used in the distributed generator islanding detection. Now domestic researches of islanding detection have not been done deep researched about the reason why islanding detection method will become invalid. Therefore, the paper analyses the performances of the frequency drift islanding method from load phase frequency characteristic and algorithm phase frequency characteristic, which are the major factors affecting the effectiveness of islanding detection method. At last, this paper proved the analysis results with MATLAB.

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Eremenko, Volodymyr, Artur Zaporozhets, Vitalii Babak, Volodymyr Isaienko, and Kateryna Babikova. "Using Hilbert Transform in Diagnostic of Composite Materials by Impedance Method." Periodica Polytechnica Electrical Engineering and Computer Science 64, no. 4 (August 13, 2020): 334–42. http://dx.doi.org/10.3311/ppee.15066.

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The article is devoted to the problem of the increasing of information quality for the impedance method of nondestructive testing. The purpose of this article is to get for the pulsed impedance method of nondestructive testing the additional informative parameters. Instantaneous values of the information signal's amplitude is a sensitive parameter to the effects of interference, in particular friction, which necessitates the use of additional informative features. It was experimentally measured signals from defective and defectless areas of the test pattern. Using of the Hilbert transform gave possibility to determine phase characteristics of these signals and realize demodulation to extract a low-frequency envelope for further analysis of its shape. It was received the informative features as a result of researches. Among them are instantaneous frequency of a signal, the integral of a phase characteristic on the selected interval and the integral of a difference signal phase characteristics. In order to compare quality of the defect detection using selected parameters it was carried out evaluation of the testing result reliability for a product fragment made of a composite material. Considering the influence of the change in the mechanical impedance of the researched area on the phase-frequency characteristics of the output signal of the converter, it is proposed to use as the diagnostic signs: the instantaneous frequency and the value of the phase characteristic of the current signal for certain points in time. The proposed informative features enable to increase general reliability of composite materials testing by the pulsed impedance method.

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Abramov, Y., V. Kryvtsova, and A. Mikhailyuk. "PHASE METHODS OF GAS GENERATORS CONTROL HYDROGEN STORAGE AND SUPPLY SYSTEMS." Municipal economy of cities 6, no. 166 (November 30, 2021): 146–50. http://dx.doi.org/10.33042/2522-1809-2021-6-166-146-150.

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Methods of control of technical condition of gas generators of systems of storage and supply of hydrogen based on use of their phase-frequency characteristics are considered. Methods of control of gas generators are divided into two groups depending on the mathematical models used to describe the operation of such gas generators. It is shown that when using as such a mathematical model the transfer function of the gas generator in the form of an inertial link, it is possible to implement control algorithms both by its phase-frequency characteristics and by its time constant. In the first case, the phase-frequency characteristic is measured at an a priori set frequency. In the second case, there is no such restriction. When using as a mathematical model of the gas generator the transfer function in the form of a fractional-rational function of the second order, the implementation of algorithms for its control can be carried out directly using the phase-frequency characteristics of the gas generator. With this implementation of algorithms for monitoring the technical condition of gas generators, the measurement of the values of their phase-frequency characteristics is carried out at several frequencies. This approach to the control of gas generators can increase the reliability of its results. All methods of monitoring the technical condition of gas generators of hydrogen storage and supply systems are focused on the use of tolerance criteria. The parameters of the tolerance criteria can be both the values of the time constants of gas generators of hydrogen storage and supply systems, and fixed values of the phase-frequency characteristics of such gas generators. In the latter case, control algorithms are implemented that cover the entire operating frequency range of gas generators.

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Brzhezitsky, V. O., Y. O. Haran, A. O. Derzhuk, O. R. Protsenko, Y. O. Trotsenko, and M. M. Dixit. "Ultimate effect of non-identity of capacitive elements of high-voltage arm on frequency characteristics of voltage divider (analytical research)." Electrical Engineering & Electromechanics, no. 4 (July 29, 2021): 46–52. http://dx.doi.org/10.20998/2074-272x.2021.4.06.

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Purpose. Determination in the analytical form of the maximum limiting influence of the non-identity of the capacitive elements of the high-voltage arm on the amplitude-frequency characteristic and phase-frequency characteristic of the voltage divider with parallel-series connection of R-, C-elements of the high-voltage arm. Methodology. Based on the previously developed theory of broadband voltage dividers with parallel-series connection of R-, C-elements, analytical expressions for amplitude-frequency and phase-frequency characteristics of the voltage divider are obtained and investigated taking into account the limit case of non-identical capacitive elements of high-voltage arm. Results. The nature of the dependencies of the frequency characteristics of the broadband voltage divider on the value of the tolerance of the capacitive elements of the high-voltage arm, the division factor of the voltage divider in a wide range of frequency changes is determined. Simplified approximating expressions for the maximum values of frequency characteristics of the voltage divider are proposed and their error is determined. Originality. For the first time in the analytical form the limiting influence of non-identity of capacitive elements of a high-voltage arm of a voltage divider on its frequency characteristics is considered. A mathematical model of this influence is constructed and the limit values of frequency characteristics of the voltage divider are determined. Practical value. It is recommended to introduce into the normative documentation of broadband voltage dividers the corrected value of the division factor, which allows to significantly reduce the deviation of the actual value of the division factor of the voltage divider from the normalized value in a wide range of frequency changes.

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Xie, Jingsong, Wei Cheng, Yanyang Zi, and Mingquan Zhang. "Phase-based spectrum analysis method for identifying weak harmonics." Journal of Vibration and Control 24, no. 23 (March 16, 2018): 5585–96. http://dx.doi.org/10.1177/1077546318760904.

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Fault characteristic frequency extraction is an important means for the fault diagnosis of rotating machineries. Traditional signal processing methods commonly use the amplitude information of signals to detect damages. However, when the amplitudes of characteristic frequencies are weak, the recognition effects of traditional methods may be unsatisfactory. Therefore, this paper proposes the phase-based enhanced phase waterfall plot (EPWP) method and frequency equal ratio line (FERL) method for identifying weak harmonics. Taking a cracked rotor as an example, the characteristic frequency detection performances of the EPWP and FERL methods are compared with that of the traditional signal processing methods namely fast Fourier transform, short-time Fourier transform, discrete wavelet transform, continuous wavelet transform, ensemble empirical mode decomposition, and Hilbert–Huang transform. Research results demonstrate that the effects of EPWP and FERL for the recognitions of weak harmonics which are contained in steady signals and transient signals are better than that of the traditional signal processing methods. The accurate identification of weak characteristic frequencies in the vibration signals can provide an important reference for damage detections and improve the diagnostic accuracy.

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Cseresnyés, I., K. Rajkai, and E. Vozáry. "Role of phase angle measurement in electrical impedance spectroscopy." International Agrophysics 27, no. 4 (December 1, 2013): 377–83. http://dx.doi.org/10.2478/intag-2013-0007.

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Abstract Importance of phase angle measurement during the application of electrical impedance spectroscopy was studied by executing pot experiments with maize. Electrical impedance, phase angle (strength of capacitive character), and dissipation factor in the plant-soil system were scanned between 100 and 10 000 Hz current frequency. The frequency-dependent change in the phase angle could be described by optimum curves culminating within 920-3 650 Hz. Since the rate of energy dissipation is independent of root extent, the higher phase angle and lower energy dissipation were associated with the higher coefficient of determination achieved for the root electrical impedance - root system size (root dry mass and root surface area) regressions. The characteristic frequency selected on the basis of phase angle spectra provided a higher significance level at statistical comparison of plant groups subjected to stress conditions influencing root development. Due to the physicochemical changes observable in aging root tissue, the apex of phase angle spectra, thus the characteristic frequency, shifted continuously toward the higher frequencies over time. Consequently, the regularly repeated phase angle measurement is advisable in time-course studies for effective application of the electrical impedance method, and the systematic operation at the same frequency without determination of phase angle spectra should be avoided.

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SATO, TADANOBU. "FRACTAL CHARACTERISTICS OF PHASE SPECTRUM OF EARTHQUAKE MOTION." Journal of Earthquake and Tsunami 07, no. 02 (June 2013): 1350010. http://dx.doi.org/10.1142/s1793431113500103.

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The purpose of this research is to make clear the phase spectrum characteristic of earthquake motion. After the introduction of past researches we introduce the concept of fractional Brownian process (FBP). A simple method is proposed to determine the Hurst index and the variance of a given process characterized by the FBP. We find that the phase characteristic of earthquake motion can be expressed by this process which is a non-stationery function of the circular frequency with a constant correlation coefficient. Using several observed earthquake motion we demonstrate this fact and show the efficiency of newly founded result to simulate realistic earthquake motion phase and also compare simulated earthquake motions with those of observed ones. We also simulate design response spectrum compatible earthquake motions by simulating the earthquake motion phase using the identified Hurst index and variance of the given earthquake motion. We investigate the effect of hypocenter distance on the variance and Hurst index of earthquake motion phase, as well as on the mean gradient of earthquake motion phase with respect to the circular frequency.

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Jia, Zhao-Min, Xu-Hai Yang, Bao-Qi Sun, Xiao-Ping Zhou, Bo Xiang, and Xin-Yu Dou. "Direct Digital Frequency Control Based on the Phase Step Change Characteristic between Signals." Chinese Physics Letters 34, no. 9 (August 2017): 090601. http://dx.doi.org/10.1088/0256-307x/34/9/090601.

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Luo, Jiufei, Haitao Xu, Kai Zheng, Xinyi Li, and Song Feng. "Barycenter Theorem in Phase Characteristics of Symmetric and Asymmetric Windows." Symmetry 10, no. 8 (August 8, 2018): 329. http://dx.doi.org/10.3390/sym10080329.

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Asymmetric windows are of increasing interest to researchers because of the nonlinear and adjustable phase response, as well as alterable time delay. Short-time phase distortion can provide an essential improvement in speech coding, and also has better performance in speech recognition. The merits of asymmetric windows in the aspect of spectral behaviors have an important function in frequency component detection and parameter estimation. In this paper, the phase response of windows were further studied, and the phase characteristics of symmetric and asymmetric windows are described. The relationship between the barycenter of windows in the time domain, and the phase characteristic at the center of the main lobe in the frequency domain, was established. In light of the relationship, an improved version of the asymmetric window- based frequency estimation algorithm was proposed. The improved algorithm has advantages of straightforward implementation and computational efficiency. The numeric simulation results also indicate that the improved approach is more robust than the traditional method against additive random noise.

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Chen, Man, He Yan Li, and Biao Ma. "Fault Mechanism Analysis and Characteristic Extraction for Multi-Disc Clutch." Applied Mechanics and Materials 526 (February 2014): 155–63. http://dx.doi.org/10.4028/www.scientific.net/amm.526.155.

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The thermo-elastic coupling model of clutch friction pair is established by the thermoelastic instability theory to acquire the basic process of friction disc warp due to hot agglomeration; according to this process, thought of reflecting initial phase clutch fault by observing the partial deformation generated by hot spots is proposed in this paper. And based on this thought, the multi-disc clutch dynamics simulation model is established to acquire the dynamic characteristics existing on the friction pair when tiny deformation happens; according to vibration characteristics of this characteristics and the feature that the interference noise of the high frequency section of the transmission system is comparatively light, and based on the analysis on the difference of frequency spectrum of the high frequency section before and after shifting gears, a new kind of initial phase multi-disc clutch fault diagnosing method based on vibration signal analysis is proposed. The test results further prove that, this method can be used to extract the impact vibration generated by tiny deformation happened on the friction pair, and is hopeful to be used in the practical engineering of initial phase multi-disc clutch fault diagnosing.

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Wang, Xinsheng, Danwei Wang, Senqiang Zhu, and Eng Kee Poh. "Fractional Describing Function Analysis of PWPF Modulator." Mathematical Problems in Engineering 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/287040.

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Pulse-width pulse-frequency (PWPF) modulators are widely used in spacecraft thruster control. Their dynamic characteristic is still lack of effective analysis tools. This paper presents a fractional describing function method to describe the frequency characteristics of PWPF. A frequency-dependent gain and phase shift are clearly described by fractional-order expression, and the fractional-order behaviors depict the nonlinear properties of PWPF modulators. This fractional describing function method can also be applied to other kinds of modulators.

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Qiang, Yan, Yingzhou Wang, Lan Luo, Gang Wang, Yuyang Zhao, and Liejiang Wei. "Method for filtering proportional valve-frequency-response test data containing impulsive noise." Advances in Mechanical Engineering 11, no. 3 (March 2019): 168781401983629. http://dx.doi.org/10.1177/1687814019836298.

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Impulsive noise, generated by inverters and other equipment used in the field, tends to easily enter test channels in scenarios where continuous frequency conversion signals are employed to test the frequency response of electrohydraulic proportional valves. Interference caused by such noise reduces the signal-to-response ratio of response signals, thereby influencing the accuracy of the frequency response of proportional valves. To address this concern, in this article, an integrated filtering method that combines ensemble empirical mode decomposition with median filtering is proposed. The proposed method first preprocesses the response signals of the systems and subsequently obtains frequency-response diagrams using fast Fourier transforms. Simulation results demonstrate that the proposed method reduces the root mean square error associated with the amplitude–frequency characteristic curves of the proportional directional valve considered from 2.1 to 0.3, whereas that associated with phase–frequency characteristic curves is reduced from 78.0 to 1.4 with signal-to-noise ratios in the high-frequency band being of the order of –20 dB. Experimental results also reveal that the proposed method reduces the root mean square error of the amplitude–frequency characteristic curves of the proportional directional valve by 52.5% and that of the phase–frequency characteristic curves by 71.2%.

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Xing, Ya Min, Sheng Hu Liu, and Dong Xu Wang. "Design and Research on Piezoelectric Acceleration Geophone." Advanced Materials Research 468-471 (February 2012): 826–30. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.826.

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A kind of piezoelectricity acceleration geophone is studied and discussed. carried on its amplitude frequency, phase-frequency characteristic theoretically, obtained the primary factor of the influence on frequency response, and improved in the piezoelectric crystal choice and geophone structure. The theory and the field test result indicated that, this piezoelectricity acceleration geophone has better response characteristic on low frequency and the high-frequency as well as a higher sensitivity, it is one better detection method.

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Li, Rui, and Li Xin Guo. "The Research of Vehicle Seat Dynamic Comfort Characteristic." Applied Mechanics and Materials 310 (February 2013): 244–48. http://dx.doi.org/10.4028/www.scientific.net/amm.310.244.

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Increasing consumption of the automobile make vehicle seat comfort characteristic paid more attention to. Damping performance as the third important factors is not allowed to ignore. A three freedom "human - seat" system model has been created for simulation. The result show that as the natural frequency f0 improved, the two resonance peak frequency of the system also improved, the growth of the first order resonance frequency is quite obvious, the second is less growth. And the higher the f0 the less change is. With the improvement of f0, the first order resonance peak to peak value obviously reduced, and the second order resonance peak to peak value increased. So, it is said that the higher the f0 the poor damping effect in high frequency area. The influence of ξ for the damping ratio of work frequency is not big, but the influence for the amplitude value is significant. Increase the natural frequency can make phase angle decreased when resonance, but the change of damping ratio, do not have obviously changes.

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Duan, Hui-qiang, Ming-tao Gao, and Hong-yu Yan. "Time-Frequency Characteristics of Acoustic Emission Signals on Water-Bearing Sandstone Specimen Subjected to Conventional Uniaxial Compression." Geofluids 2022 (May 11, 2022): 1–11. http://dx.doi.org/10.1155/2022/8101861.

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This paper presents an experimental investigation of acoustic emission (AE) time-frequency characteristics of a water-bearing sandstone specimen in a conventional uniaxial compression test. The main achievements are as follows: (1) The violent fluctuation of AE time domain parameters indicates that the water-bearing sandstone specimen is about to be destroyed. This characteristic provides a theoretical basis for predicting the failure of water-bearing rock in engineering practice. (2) In the elastic phase, the AE b value is the lowest but has a sudden increase after falling into the steady crack propagation phase. In the unsteady crack propagation phase, the AE b value is further increased. This characteristic is of great indicative value for predicting the failure of the water-bearing sandstone specimen. (3) The difference of dominant frequency among the three key points is very small, indicating that the crack initiation and propagation of the water-bearing sandstone specimen has a certain stability in the damage and failure process. But, the two-dimensional frequency spectrum structure of AE waveform signals shows that the closer to failure, the more the number of the frequency spectrum structure peaks. (4) The energy of AE signals is mainly concentrated in the first three frequency bands. The closer to failure, the more the energy proportion of the first three frequency bands is reduced; conversely, the energy proportion of the latter five frequency bands is increased, which leads to more complexity of the failure modes of the water-bearing sandstone specimen.

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Tian, Jin Yue, Bei Jing Hu, Bao Lin Yang, and Xian Feng Wang. "Stability Problems of Frequency-Converting Rotation Dynamics on Concrete Mixer." Applied Mechanics and Materials 215-216 (November 2012): 907–11. http://dx.doi.org/10.4028/www.scientific.net/amm.215-216.907.

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As a number of parameters significantly influence the concrete mixtures quality, the concrete fluidity impacts much on the production process and product quality. To improve the concrete mixtures quality, the concept of frequency-converting rotation is proposed based on the rotation driving dynamic characteristics of mixer. By analysing the phase-frequency characteristic of twin-shaft mixer's working system, the dynamic behavior of mixing concrete is defined. When the agitating shaft is frequency-converting drive, the "boiling" movement occurs in concrete, which characteristics are better than that constant speed drive makes and improves the microscopic homogeneity of concrete.

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Wang, S. K., S. J. Lee, O. C. Jones, and R. T. Lahey. "Statistical Analysis of Turbulent Two-Phase Pipe Flow." Journal of Fluids Engineering 112, no. 1 (March 1, 1990): 89–95. http://dx.doi.org/10.1115/1.2909374.

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The statistical characteristics of turbulent two-phase pipe flow have been evaluated. In particular, the autocorrelation functions and the power spectral density functions of the axial turbulence fluctuations in the liquid phase were determined. The high frequency content of the power spectrum in bubbly two-phase pipe flow was found to be significantly larger than in single-phase pipe flow and, in agreement with previous studies of homogeneous two-phase flows (Lance et al., 1983), diminished asymptotically with a characteristic −8/3 slope at high frequency. The power spectrum and the autocorrelation functions in two-phase pipe flow, although distinctively different from those in single-phase pipe flow, were insensitive to the local void fraction and the mean liquid velocity when plotted against wave number and spatial separation, respectively. Finally, the dissipation scale, determined from the shape of the autocorrelation function, indicated that the turbulent dissipation rate in two-phase pipe flow was significantly greater than that in single-phase pipe flow.

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32

Fan, Wen Yuan, and Xiao Hong Yin. "Nonlinear Analysis of Bubble Formation Dynamics in Shear-Thinning Fluids." Advanced Materials Research 881-883 (January 2014): 717–20. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.717.

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The dynamics of bubble generating in carboxymethylcellulose (CMC) aqueous solution were studied using chaos method. The results show that for low position (P) and gas flowrate (Qg), the characteristic frequency of axial and radial velocities are both consistent to bubble periodic shear frequency; but for high position, power spectrums are of broad coverage within low frequency range. The magnitudes of radial characteristic peaks increase with gas flowrate. Phase portraits of reconstructed phase space of velocity time series display certain features of chaotic attractor. For lowPandQg, phase portrait takes on uniform elliptical shape due to liquid periodic motion caused by bubble periodic rising. Whereas for highPandQg, the liquid turbulence is reinforced by bubble increasing velocity and large-scale turbulent intensity around bubble increases, consequently, leading to significant compression of phase portrait.

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Zhang, Shuai, Bin Sun, and Er Peng Wang. "Characteristic Variables Extracting of the Gas-Liquid Two-Phase Flow through V-Cone Flowmeter Based on Adaptive Optimal-Kernel Theory." Advanced Materials Research 516-517 (May 2012): 1082–85. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.1082.

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In order to study the mechanism of gas-liquid two-phase flow, a method of characteristic variables extracting based on Adaptive Optimal-Kernel (AOK) theory was represented in the paper. First, to collect dynamic differential pressure signal of gas-liquid two-phase flow through a horizontal V-cone flow meter, and then the AOK theory was used to analyze the dynamic differential pressure signal. The movement law of two-phase flow was discussed through the time-frequency spectrum. Finally, four characteristic variables were defined by using the time-frequency spectrum and the ridge of AOK. After the characteristic variables were visual analyzed, the relationship between the different combination of characteristic variables and the flow pattern was obtained. The results show that, characteristic variables defined by this method can get a clear description of the flow information. This method provides a new way for the flow patterns identification.

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Yu, Liang Jun, Li Hua Sun, and Cui Cui Huang. "Design of Comprehensive Test Instrument Based on FPGA and Cortex-M0." Applied Mechanics and Materials 312 (February 2013): 583–87. http://dx.doi.org/10.4028/www.scientific.net/amm.312.583.

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The design consists of three modules: the voltage amplitude measurement module, the level oscillator module and the amplitude-frequency characteristic test module. The voltage amplitude measurement module uses AD817 to consist three-stage amplifier. The magnification of each level can be adjusted for 1 times/10 times. At the same time, the author uses the Cortex-M0 for controlling the relay switch to achieve automatic range conversion. The principle of DDS is adopted in the level oscillator module. FPGA is used for realizing the phase accumulator, the phase modulator, the sine ROM look-up table. Digital signal is finally outputted by high-speed analog-to-digital conversion chip DAC900. Then, by controlling the 6-channel relay switch to make the magnification in the amplifying circuit,which can be adjusted step-by-step from-30dB to 20dB. Through outputting sine wave whose amplitude is fixed, but frequency is variable to the network under test, amplitude-frequency characteristic test module measures the relation betthe authoren the amplitude change of the output signal and the signal frequency to obtain the amplitude-frequency characteristics of the network under test..

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35

Feng, Guoli, Zhihao Ye, Yihui Xia, Heng Nian, Liming Huang, and Zerun Wang. "High Frequency Resonance Suppression Strategy of Three-Phase Four-Wire Split Capacitor Inverter Connected to Parallel Compensation Grid." Energies 15, no. 4 (February 17, 2022): 1486. http://dx.doi.org/10.3390/en15041486.

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With the continuous penetration and development of renewable energy power generation, the distributed grid and the microgrid are becoming increasingly important in modern power systems. In distribution networks and the microgrid, the grid impedance is comparatively large and cannot be ignored. Usually, the parallel compensation is used to improve the grid quality. In the grid with parallel compensation, the large phase angle difference between the impedance of the grid-connected inverter and the impedance of the grid at amplitude intersection will result in high frequency resonance (HFR). Because the inverter shows filter characteristics due to limited bandwidth of the controller, the parallel compensation grid, respectively, performs as the capacitance characteristic and inductance characteristic in different high frequency range. Compared with the three-phase, three-wire system, an additional zero-sequence path exists in the three-phase four-wire split capacitor inverter (TFSCI) system, so that the existing high frequency resonance suppression methods will be not effective. Since the zero-sequence component is neglected, HFR will also occur, in addition to the positive-sequence component and the negative-sequence component. Therefore, in order to suppress the high frequency resonance caused by positive-sequence, negative-sequence and zero-sequence components, an impedance reshaping strategy based on current feedback is proposed in this paper. This proposed method can reshape the amplitude and phase of the inverter impedance in a high frequency range without affecting the performance of the fundamental frequency control and ensure that the inverter contains a sufficient phase margin. Additionally, the proposed method can reshape the impedance of TFSCI within a wide frequency range, which makes it able to cope with the challenge of the parallel compensation degree change. Theoretical analysis and experiments verify the availability of the proposed control strategy.

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Geldof, H., E. J. van der Schee, and J. L. Grashuis. "Electrogastrographic characteristics of interdigestive migrating complex in humans." American Journal of Physiology-Gastrointestinal and Liver Physiology 250, no. 2 (February 1, 1986): G165—G171. http://dx.doi.org/10.1152/ajpgi.1986.250.2.g165.

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Interdigestive myoelectric activity and mechanical activity were studied simultaneously by means of cutaneous electrodes (electrogastrography) and intraluminal pressure recording, respectively, in 10 healthy male volunteers. The aims of the present study were 1) to describe the characteristics of the electrogastrogram during the different phases of the interdigestive migrating complex (IMC) in healthy subjects and 2) to determine to what extent these characteristics can be used to identify the different phases of the IMC. The electrogastrograms were analyzed visually and by running-spectrum analysis. It was concluded that in humans the gastric frequency present in the electrogastrogram appears to be less stable during motor activity than during motor quiescence, in particular during phase III, but far more stable than its canine counterpart. A small but consistent drop in gastric frequency was observed in the changeover from motor quiescence to phase II motor activity. The power of the gastric frequency increased with increasing motor activity, except during phase III. A characteristic frequency and power behavior during phase III could only be recognized in a minority of the IMCs. In general, electrogastrography cannot, given the present state of the art, be used to precisely identify the different phases of the IMC.

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Yamada, Kou, Tatsuya Sakanushi, Takaaki Hagiwara, Iwanori Murakami, Yoshinori Ando, Shun Yamamoto, and Nhan Luong Thanh Nguyen. "The Parameterization of all Stabilizing Modified Repetitive Controllers for Multiple-Input/Multiple-Output Plants with the Specified Input-Output Frequency Characteristic." Applied Mechanics and Materials 36 (October 2010): 273–81. http://dx.doi.org/10.4028/www.scientific.net/amm.36.273.

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In this paper, we examine the parameterization of all stabilizing modified repetitive controllers for multiple-input/multiple-output plants with the specified input-output frequency characteristic. The parameterization of all stabilizing modified repetitive controllers for non-minimum phase systems was solved by Yamada et al. However, when we design a stabilizing modified repetitive controller using the parameterization by Yamada et al., the input-output frequency characteristic of the control system cannot be settled so easily. The input-output frequency characteristic of the control systems is required to be easily settled. This problem is solved by obtaining the parameterization of all stabilizing modified repetitive controllers with the specified input-output frequency characteristic. However, no paper has proposed the parameterization of all stabilizing modified repetitive controllers for multiple-input/multiple-output plants with the specified input-output frequency characteristic. In this paper, we propose the parameterization of all stabilizing modified repetitive controllers for multiple-input/multiple-output plants with the specified input-output frequency characteristic.

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Meng, Fei, Jien Yang, Peng Song Yang, and Biao Sun. "The Research of Frequency Characteristics of Tracking Differentiator." Applied Mechanics and Materials 182-183 (June 2012): 1474–78. http://dx.doi.org/10.4028/www.scientific.net/amm.182-183.1474.

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Function fhan() and tracking differentiator are important components of Active Disturbance Rejection Control Technique. It is pointed out that function fhan() is not the optimal control synthesis function of discrete system, but function fsun() is. Amplitude and phase frequency characteristic curves of tracking differentiators constructed respectively by function fhan() and fsun() are given by computer simulations. The account formula about turning frequency is also given. Influence of parameter variation on tracking differentiator frequency characteristic is analyszed. The conclusion of this paper is supplement and perfection for the theory of tracking differentiator in Active Disturbance Rejection Control Technique, and it can promote rapid development of Active Disturbance Rejection Control Technique.

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Li, Yijin, Jianhua Lin, Geng Niu, Ming Wu, and Xuteng Wei. "A Hilbert–Huang Transform-Based Adaptive Fault Detection and Classification Method for Microgrids." Energies 14, no. 16 (August 17, 2021): 5040. http://dx.doi.org/10.3390/en14165040.

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Fault detection in microgrids is of great significance for power systems’ safety and stability. Due to the high penetration of distributed generations, fault characteristics become different from those of traditional fault detection. Thus, we propose a new fault detection and classification method for microgrids. Only current information is needed for the method. Hilbert–Huang Transform and sliding window strategy are used in fault characteristic extraction. The instantaneous phase difference of current high-frequency component is obtained as the fault characteristic. A self-adaptive threshold is set to increase the detection sensitivity. A fault can be detected by comparing the fault characteristic and the threshold. Furthermore, the fault type is identified by the utilization of zero-sequence current. Simulations for both section and system have been completed. The instantaneous phase difference of the current high-frequency component is an effective fault characteristic for detecting ten kinds of faults. Using the proposed method, the maximum fault detection time is 13.8 ms and the maximum fault type identification time is 14.8 ms. No misjudgement happens under non-fault disturbance conditions. The simulations indicate that the proposed method can achieve fault detection and classification rapidly, accurately, and reliably.

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40

Osipov, A. V., and V. M. Rulevskiy. "Resonant LCL Converter with Frequency-Pulse-Width Control." Proceedings of Tomsk State University of Control Systems and Radioelectronics 24, no. 2 (2021): 77–83. http://dx.doi.org/10.21293/1818-0442-2021-24-2-77-83.

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The paper considers the features of frequency-pulse-width control in a resonant LCL converter with an active rectifier in the mode of parametric stabilization of the output current. The analysis of the properties of the LCL converter during regulation by the rectifier is carried out, the phase frequency characteristic and the coefficient of parametric stabilization are obtained. It is shown that the rectifier introduces a reactive component into the impedance of the resonant circuit. It is illustrated that the introduction of the control angle leads to the loss of roots by the equation on a part of the load range. The estimation of the frequency adjustment in the converter is carried out, the control characteristic is obtained, the energy advantages of frequency-pulse-width control are demonstrated, which consists in the zero phase of the inverter current and minimization of the recuperation interval

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Tian, Feng, and Hong Jie Si. "The Method of Fast Frequency Response Testing Based on LabVIEW." Applied Mechanics and Materials 433-435 (October 2013): 833–36. http://dx.doi.org/10.4028/www.scientific.net/amm.433-435.833.

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This paper designs a virtual spectrum analyst based on LabVIEW,chirp signal is used for pumping signal of the system. A fast frequency estimation method is realized by the graph programming language LabVIEW. Compared with traditional virtual spectrum analyst, this method can better and faster measure amplitude-frequency characteristic and phase frequency characteristic. The interference factors emerged frequently during the data acquisition were described briefly, and the technology of verification and manipulation of the anomalous signals were studied.

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42

Xie, Yuchen, Zhengrong Li, Feiqiang Chen, Huaming Chen, and Feixue Wang. "The Unbiased Characteristic of Doppler Frequency in GNSS Antenna Array Processing." International Journal of Antennas and Propagation 2019 (April 24, 2019): 1–10. http://dx.doi.org/10.1155/2019/5302401.

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The antenna array technology, especially the spaced-time array processing (STAP), is one of the effective methods used in Global Navigation Satellite System (GNSS) receivers to refrain the power of jamming and enhance the performance of receivers in the circumstance of interference. However, biases induced to the receiver because of many reasons, including characteristic of antennas, front-end channel electronics, and space-time filtering, are extremely harmful to the high precise positioning of receivers. Although plenty of works have been done to calibrate the antenna and to mitigate these biases, achieving a good performance of antijamming, high accuracy, and low complexity at the same time still remains challenging. Different from existing works, this paper leverages the characteristic of GNSS signal’s Doppler frequency in STAP, which is proven to remain unbiased to solve the problem, even when the nonideal antennas are used and the interference circumstance changes. Since the integration of frequency is carrier phase, the unbiased Doppler frequency leads to an accurate estimation of carrier phase which can be used to calibrate the antenna array without extra apparatus or complicating algorithms. Therefore, a simple Doppler-aid strategy may be developed in the future to solve the difficulty of STAP bias mitigation.

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Feng, Shi Min, Sui Hua Zhou, and Hong Xin Zhang. "A Method on Underwater Extremely Low Frequency Atmospheric Noise." Applied Mechanics and Materials 333-335 (July 2013): 2457–60. http://dx.doi.org/10.4028/www.scientific.net/amm.333-335.2457.

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On the basis of low-pass characteristic of the ocean in extremely low frequency (ELF) band , which makes the atmospheric noise distort and signal to noise (SNR) of the receiver worse, magnitude-frequency and phase frequency characteristic of the ocean in ELF band were researched. Influence at different depth of the ocean on the atmospheric noise was simulated and frequency compensation filter was designed with the best uniform approximation method to compensate the distorted atmospheric noise. With the sampling frequency fs=1KHz, at 30m~200m depth, no more than 9th-order IIR filter was used to design frequency compensation filter. The maximal error of the magnitude-frequency characteristic of the designed frequency compensation filter is less than 0.5dB compared with the theoretical. With the filter, the sharpness of the ELF atmospheric noise spikes are restored and the SNR of the receiver is improved.

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Yang, Duoxing, and Lianzhong Zhang. "Propagation of Pore Pressure and Stress in Saturated Porous Media Based on a Darcy-Brinkman Formulation." Geofluids 2021 (December 27, 2021): 1–12. http://dx.doi.org/10.1155/2021/1301044.

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Propagation of pore pressure and stress in water-saturated elastic porous media is theoretically investigated when considering the Darcy-Brinkman law. The wave mode, phase velocity, phase lag, damping factor, and characteristic frequency are found from the updated mathematic model. The Brinkman term describes the fluid viscous shear effects and importantly contributes to the dispersion relation and wave damping. The coincidence of the properties of Biot waves of the first and second kinds occurs at a characteristic frequency, which is remarkably influenced by the Brinkman term. A key finding is that, compared to the Darcy-Brinkman law, Darcy’s law overestimates the phase velocity, damping, and phase lag of the first wave, while underestimates the phase velocity, damping, and phase difference of the second wave. The introduction of the Darcy-Brinkman law yields an improved description of the damping of the compressional wave modes in saturated porous media.

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Qi, Junwei, Sergey B. Makarov, Mingxin Liu, Beiming Li, and Wei Xue. "Research on an Optimization Method for a Partially Responsive Continuous Phase Modulated (CPM) Signal Based on an Optimal Generic Function." Symmetry 11, no. 9 (September 3, 2019): 1114. http://dx.doi.org/10.3390/sym11091114.

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This paper establishes an optimal generic function model in order to obtain a continuous phase modulated (CPM) signal with a smoother phase modulation function. This is achieved by finding the solution to the symbol signals at different lengths of the CPM function. In the solution process, the unknown amount that needs to be solved is reduced by using the even function symmetry characteristic of the signal to be solved. For each different form of the signal, the time domain form of the CPM function and the corresponding normalized energy spectral density are compared under the influence of the phase modulation signal length and the generic function parameter n. The data transmission rate is improved by introducing inter-symbol interference, and the modulation process is realized using six-way parallel transmission when the CPM function is 6T. The simulation results show that the CPM function obtained by establishing an optimal generic function model has high-quality time-frequency characteristics. The real-time phase trajectory and the high-order derivative are both continuous, and the modulated signal has constant envelope characteristics. The CPM function has a fast rolling-off in the frequency domain and small out-of-band radiation, which greatly improves the characteristics of the frequency band utilization.

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46

Li, Yuan Yuan, Qi Zhong Liu, and Chao Gang Yu. "Wavelet Transform for Starting Characteristics of Three-Phase Cage Asynchronous Motor." Advanced Materials Research 347-353 (October 2011): 2987–90. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.2987.

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In electric machinery performance test, tooth harmonic time-frequency characters of first order of three-phase cage asynchronous motor are most important. The MATLAB software is used to make model and simulate the starting characteristic of asynchronous motor in this article, while the stator current signal of starting motor is de noised by wavelet transform. Through decomposition and reconstruction of wavelet transform, the amplitude of fundamental and harmonic wave in de noising stator current can be reduced, and then the tooth harmonic of first order of starting rotor is extracted. Using the excellent time-frequency analyzing characters of wavelet package transform, the tooth harmonic time-frequency curve is fitted.

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DAVIS, MATTHEW S., NATHAN G. NUTTER, and EPAMINONDAS ROSA. "DRIVING PHASE SYNCHRONOUS PLASMA DISCHARGES WITH SUPERIMPOSED SIGNALS." International Journal of Bifurcation and Chaos 17, no. 10 (October 2007): 3513–18. http://dx.doi.org/10.1142/s0218127407019287.

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Numerical simulations and experimental measurements performed on a plasma discharge, simultaneously paced with two independent sinusoidal functions, show the plasma moving from one synchronous state to another, back and forth, between the two independent pacers. Different approaches for studying this competition for phase synchronization indicate the relevance of the relative frequency values of the two sinusoidal functions with respect to the predominant frequency characteristic of the unpaced plasma discharge.

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48

Liu, Xuewen, Zhengcheng Qin, and Hongsheng Li. "Online Compensation of Phase Delay Error Based on P-F Characteristic for MEMS Vibratory Gyroscopes." Micromachines 13, no. 5 (April 19, 2022): 647. http://dx.doi.org/10.3390/mi13050647.

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In this paper, an online compensation method of phase delay error based on a Phase-Frequency (P-F) characteristic has been proposed for MEMS Coriolis Vibratory Gyroscopes (CVGs). At first, the influences of phase delay were investigated in the drive and sense mode. The frequency response was acquired in the digital control system by collecting the demodulation value of drive displacement, which verified the existence and influence of the phase delay. In addition, based on the P-F characteristic, that is, when the phase shift of the nonresonant drive force through the resonator is almost 0° or 180°, the phase delay of the gyroscope is measured online by injecting a nonresonant reference signal into the drive-mode dynamics. After that, the phase delay is self-corrected by adjusting the demodulation phase angle without affecting the normal operation of the gyroscopes. The approach was validated with an MEMS dual-mass vibratory gyroscope under double-loop force-to-rebalance (in-phase FTR and quadrature FTR) closed-loop detection mode and implemented with FPGA. The measurement results showed that this scheme can detect and compensate phase delay to effectively eliminate the effect of the quadrature error. This technique reduces the zero rate output (ZRO) from −0.71°/s to −0.21°/s and bias stability (BS) from 23.30°/h to 4.49°/h, respectively. The temperature sensitivity of bias output from −20 °C to 40 °C has reached 0.003 °/s/°C.

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Liu, Guang Ya, and Xiao Song Li. "The Design and Simulation of Three-Phase PWM Converter." Applied Mechanics and Materials 321-324 (June 2013): 917–20. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.917.

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Three-phase voltage source PWM rectifier generally adopts double closed loop control system. According to the high frequency characteristic of three-phase voltage source PWM rectifier, this paper put forward the setting method of current inner ring regulator and voltage outer ring regulator PI parameter. Finally, it is verified by simulation.

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Zhang, Zhong Lin, and Tao Wang. "Single-Phase Independent Droop Control Strategy in Low-Voltage Microgrid." Applied Mechanics and Materials 733 (February 2015): 684–90. http://dx.doi.org/10.4028/www.scientific.net/amm.733.684.

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In the three-phase four-wire low-voltage micro grid, three-phase imbalance usually happens because of a large number of single-phase loads. In this situation, the traditional control method cannot effectively control the voltage and frequency stability when the low-voltage micro grid operates in the island mode. According to the characteristics of the three-phase four-wire low-voltage micro grid, this paper designs a single-phase independent control based on the droop control. This paper firstly uses the improved droop control considering that the impedance characteristic of the low voltage micro gird is mainly resistance, and also designs single-phase independent control to ensure the control system have the ability to run under the unbalanced loads. Then this paper designs a two-level control strategy to control the voltage and frequency in the micro grid during the island operation. Finally, a simulation analysis based on the proposed method is used to prove the effectiveness. A micro grid is set up on PSCAD, and verifies the effectiveness of the single-phase control strategy based on the improved droop control. The proposed method can also realize the requirement of the voltage and frequency stability during the island operation. At the same time, the control method proposed in this paper can achieve the control objective under the condition of unbalanced three-phase.

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Journal articles on the topic 'Phase-frequency characteristic'

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