Frequency Of Harmonic Signal Research Articles

АДАПТИВНІ СПОСТЕРІГАЧІ ЧАСТОТИ ДВОФАЗНИХ ТА ОДНОФАЗНИХ ГАРМОНІЧНИХ СИГНАЛІВ

An adaptive observer for frequency and magnitude of two-phase symmetrical sinusoidal signal is presented. It is de-signed based on control concept of internal model approach. The observer guarantees global exponential estimation and high performance. If the information about one of the two-phase signal components is missing, a modified structure of the observer is proposed. This case is equivalent to the measurement of a single-phase sinusoidal signal. The proper-ties of local exponential stability of single-phase signal observer are proved using Lyapunov’s conversion theorem for disturbed systems. The robustness of the two-phase signal observer with respect to additive disturbances (high-frequency noise, varying frequency) is confirmed by simulation results. It is shown that the observer estimation speed can be arbitrarily increased by increasing the feedback gains. A method for single-phase harmonic signal frequency observer tuning is developed, which ensures the expansion of the stability region. References 14, figures 7.

Instantaneous Fundamental Frequency and Model Order Estimation of Non-Stationary Harmonic Signals

Instantaneous Fundamental Frequency and Model Order Estimation of Non-Stationary Harmonic Signals

Periodic‐phase‐diagram similarity method for weak signal detection

AbstractThe periodic‐phase‐diagram similarity method is proposed to identify the frequency of weak harmonic signals. The key technology is to find a set of optimal coefficients for Duffing system, which leads to the periodic motion under the influence of weak signal and strong noise. Introducing the phase diagram similarity, the influences of strong noise on the similarity of periodic phase diagram are discussed. The principle of highest similarity of periodic phase diagram with the same frequency is detected by discussing the persistence of similarity of periodic motion phase diagram under the strong noise and the periodic‐phase‐diagram similarity method is constructed. The weak signals of early fault and strong noise are input into Duffing system to obtain the identified system. The stochastic subharmonic Melnikov method is extended to obtain the conditions of the optimal coefficients for the identified system. Based on the results, the constructed frequency conversion harmonic weak signals are considered to form a datum periodic system. With the change of frequency in the datum periodic system, the phase diagram similarity of the two constructed systems can be calculated. Based on the periodic‐phase‐diagram similarity method, the frequency of weak harmonic signals can be identified by the principle of highest similarity of periodic phase diagram with the same frequency. The results of numerical simulation and the early fault diagnosis results of actual bearings verify the feasibility of the periodic‐phase‐diagram similarity method. The accuracy of the detection effect is 97%, and the minimum signal‐to‐noise ratio is −80.71 dB.

Алгоритм оцінювання частоти комплексного гармонічного сигналу з сегментацією даних спостережень

The article deals with the technology of estimating the frequency of harmonic components in the presence of additive normal interferences for solving applied problems of spectral analysis. Objective: to develop a methodology for the synthesis of algorithms for determining the frequency of a complex harmonic signal in discrete sections of the process, this is observed when using data segmentation. Objective: to develop the optimal technology for determining the frequency of the hormonal component of the process, provided by a finite number of discrete compartments, according to model representations and requirements that meet the problems of the current state of spectral analysis practice. These results were obtained. The problem of estimating the harmonic frequency from segmented data in the presence of additive Gaussian interference in observations based on the method of maximum likelihood is solved. The processing algorithm and the consequences of digital modeling of the synthesized evaluation technology for a given number of discrete process samples are given. The analysis of both the practical capacity of the technology for determining the assessment and certain qualitative indicators of assessment is performed. Conclusions. The scientific novelty of the obtained results is as follows: further development as a method for solving problems of estimating the frequency of the harmonic signal from a few sample values of the process under conditions of additive normal interference and methods for optimizing the structure of digital processing of observations in data segmentation. The synthesized technology uses one sample of observations to determine the estimates, which ensure the efficiency of information processing in a simple software implementation. The use of segmentation in the technological process of digital processing of observations allows obtaining estimates, the quality of which corresponds to the indicators of maximum likelihood. For unambiguous assessment, there is a need to eliminate ambiguity. Under these conditions, the technology with a given number of samples can significantly solve the range of signal-to-noise ratios at which can be obtained unbiased estimates.

A novel frequency tracker for sinusoidal signal based on state dependent Riccati Equation filter

This paper presents a new approach for frequency estimation and tracking based on State Dependent Riccati Equation Filter (SDREF). The SDREF is an alternative concept to the well-known Extended Kalman Filter (EKF) to design a robust nonlinear filter, with low computational costs and better performances. The aim is to estimate and track the time-varying fundamental frequency of harmonic sinusoidal signals in general and more particularly the fundamental electric frequency. Through this study, the performance of the proposed approach is compared to the widely adopted the EKF, taking into account several aspects both theoretically and real-life applications. It has been shown that the proposed estimator performs better than the usual EKF estimator in terms of noise robustness, estimation accuracy, and tracking ability both in numerical simulations and experimental study.

Adaptive Hybrid Generalized Integrator Based SMO for Solar PV Array Fed Encoderless PMSM Driven Water Pump

The encoder influences reliability and cost of permanent magnet synchronous motor (PMSM) operated solar water pump (WP). It is even sensitive to electromagnetic noise and temperature, which thereby reduces its accuracy. To overcome these problems, an encoderless PMSM control by using adaptive hybrid generalized integrator (AHGI) based sliding mode observer (SMO) for the solar WP system is presented in this paper. The widely used low pass filter based SMO produces phase-shift, attenuation and dominant lower order harmonics (DLOH). This decreases the position estimation accuracy. Besides, the need for tracking dynamic system frequency further exacerbates its performance. The developed AHGI structure eliminates these drawbacks and provides an accurate estimate of position over a wide speed range. A harmonic decoupling network, a hybrid generalized integrator and an adaptive frequency tracker constitute AHGI, which respectively performs dominant harmonic signal generation, DLOH elimination and frequency tracking. The improvement in behavior of AHGI over the existing methods is analyzed by transfer functions, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bode</i> plots and back electromotive force helices. Meanwhile an incremental conductance algorithm for PV array maximum power control is used. The developed structure is experimentally validated on a laboratory prototype and a comparison with the existing methods is also made.

Phase-Based Estimation of the Harmonic Signal Frequency

This paper examines estimating the frequency of the information signal based on the analysis of the probability characteristics of the phase fluctuations when a mix of signal and narrowband noise is observed. The new estimation algorithm is described while the shortcomings of the commonly applied methods are specified. The performance of the proposed approach is illustrated by a number of examples. In particular, it is demonstrated that the application of the introduced procedure allows high accuracy measurements of the carrier frequency of the non-modulated, the multilevel phase and quadrature keyed signals.

Distribution of optical-comb-based multi-frequency microwave signals over 100 km optical fiber with high phase stability.

We demonstrate a long-distance multi-frequency microwave distribution system over an optical fiber link with high phase stability based on transferring an optical frequency comb (OFC). The phase fluctuation induced by the transmission link variations is detected by applying a reference OFC and is then compensated with the proposed optical voltage-controlled oscillator (OVCO) by adjusting the phase of the repetition rate of the transmitted OFC. By applying the OVCO, we perform the OFC-based multi-frequency microwave distribution over a 100 km standard single-mode fiber. The performance of the transmission system can be exhibited by evaluating the repetition rate (10.015 GHz) and second harmonic frequency (20.03 GHz) signals achieved at the remote end. The residual phase noise of the 10.015 GHz and 20.03 GHz signal is -64 dBc/Hz and -58 dBc/Hz at 1 Hz frequency offset from the carrier, respectively. The fractional frequency instability is 1.4×10-16 and 2.4×10-16 at 10000 s averaging time, respectively. And the timing jitter in the frequency range from 0.01 Hz to 1 MHz reaches 88 fs and 87 fs, respectively. Based on the phase-locked loop theory, we conduct a simulation model of the transmission system and the simulated results match well with experiments. It shows that by detecting the phase fluctuation with higher harmonic frequency signals in the simulation system, the performance of the transmission system can be further improved.

Variable scale-convex-peak method for weak signal detection

A variable scale-convex-peak method is constructed to identify the frequency of weak harmonic signal. The key of this method is to find a set of optimal identification coefficients to make the transition of dynamic behavior topologically persistent. By the stochastic Melnikov method, the lower bound of the chaotic threshold continuous function is obtained in the mean-square sense. The intermediate value theorem is applied to detect the optimal identification coefficients. For the designated identification system, there is a valuable co-frequency-convex-peak in bifurcation diagram, which indicates the state transition of chaos-period-chaos. With the change of the weak signal amplitude and external noise intensity in a certain range, the convex peak phenomenon is still maintained, which leads to the identification of frequency. Furthermore, the proposition of the existence of reversible scaling transformation is introduced to detect the frequency of the harmonic signal in engineering. The feasibility of constructing the hardware and software platforms of the variable scale-convex-peak method is verified by the experimental results of circuit design and the results of early fault diagnosis of actual bearings, respectively.

Research on Harmonic Detection System Based on Wavelet Packet Transform

This paper introduces the basic concepts of harmonics in power system, and expounds the basic principles of harmonic detection algorithms such as Fourier transform, short wavelet transform and wavelet packet transform. The effectiveness of the proposed algorithm is verified by simulation, which shows that the improved wavelet packet algorithm can achieve the uniform division of the harmonic signal frequency band, and improve the detection accuracy of the harmonic signal. Wavelet packet transform could detect the fundamental and harmonic components of the original signal, which is most suitable for the detection of harmonic signals.

Research on Harmonic Analysis and Detection Based on Improved Wavelet Packet Inverter

This paper introduces the basic concepts of harmonics in power system, and expounds the basic principles of harmonic detection algorithms such as Fourier transform, short wavelet transform and wavelet packet transform. The effectiveness of the proposed algorithm is verified by simulation, which shows that the improved wavelet packet algorithm can achieve the uniform division of the harmonic signal frequency band, and improve the detection accuracy of the harmonic signal. Wavelet packet transform could detect the fundamental and harmonic components of the original signal, which is most suitable for the detection of harmonic signals.

Theoretical Investigations of the Ultrasonic Wave Generation by an Electromagnetic Acoustic Transducer

Background. The article considers the analysis of the electromagnetic acoustic (EMA) converter with controlled angular input of acoustic waves, using parameters influencing the formation of an acoustic wave.Objective. The aim of the paper is to analyze the formation of an acoustic wave with angular input in the EMA converters of non-destructive testing systems.Methods. Mathematical modelling was used to investigate the influence of the distance from the yarn-emitters to the control object surface. The influence of various factors (current magnitudes, external magnetic field values, distance from the yarn-emitter and the grating to the control object surface) is investigated with the help of mathematical modeling.Results. The optimal value of the magnetic induction of an external magnetic field is shown. The calculation of the pressure created by the yarn-emitters and the grating on the controlled object surface was carried out. A formula for the ultrasonic wave input angle was obtained. The formula depends on the parameters of the control environment, the distance between the emitters, the phase shift between the harmonic current signals applied to the adjacent emitters and the harmonic signal frequency. It was found that a change in the angle between the EMA transducer and the surface of the control object leads to a significant deterioration in the acoustic wave generation on the surface of the controlled object.Conclusions. We investigated the possibility of the angular input of an ultrasonic wave using system of parallel-arranged yarn-emitters. A decrease in the acoustic pressure, with increasing distance from the yarn-emitters to the controlled object surface was observed.

АЛГОРИТМ ОПРЕДЕЛЕНИЯ ЧАСТОТЫ ГАРМОНИЧЕСКОГО СИГНАЛА С ИСПОЛЬЗОВАНИЕМ СТОХАСТИЧЕСКОЙ ДИСКРЕТИЗАЦИИ

The paper deals with the development of an algorithm for determining frequency of harmonic signals using a probabilistic-statistical method. The main feature of this algorithm is a short time of addressing to the investigated signal, which much shorter than signal period, according to three integrated sample collections with digital processing. Instantaneous values of the investigated signal in each sampling are based on stochastic discretization over time, according to the uniform distribution law. The main advantages of the algorithm are the short time of access to the signal under study and high accuracy of frequency measurement, which is essential for the infralow frequency signals with a duration period measured in minutes, hours, days, etc. There has been performed a numerical experiment in order to evaluate an error in determining frequency of such signals, depending on the accuracy of their sampling by real analog-to-digital converters. The paper shows that the error of frequency determined by the developed algorithm makes a few hundredths of a percent and scarcely depends on accuracy of a signal discretization by a certain level. The error obtained corresponds to discretization accuracy under conversion into accepted values of analogue-to-digital converters from 6- to 16-bit analogue-to-digital converters. The present algorithm may find practical use in radio technical processing of infralow frequency signals in acoustics, hydro-acoustics, seismic acoustics, underwater and underground communication.

Simultaneous fundamental and subharmonic/ harmonic frequency signals generation from a dual-cavity fiber laser based on regenerative mode-locking and active mode-locking

This paper presents a dual-cavity mode-locked laser, which is able to simultaneously output two optical pulses with different wavelengths and frequency. In this dual-cavity configuration, one cavity works as a regenerative mode-locked laser and outputs signal with a fundamental repetition frequency, the other one acts as an active mode-locked laser and generates signal with subharmonic or harmonic frequency by fine tuning the cavity length. In experimental demonstration, 5GHz signal from regenerative mode-locked cavity and 2.5/ 5/ 10/ 15/ 20GHz signal from active mode-locked cavity are simultaneously obtained. Additionally, signals in active mode-locked cavity get further super-mode suppression.

Stochastic resonance in photo-switchable spin-crossover solids

The stochastic kinetic in photo-switchable spin-crossover materials with periodic driving force in the context of stochastic resonance (SR) was studied. The resonance phenomena in spin-crossover system have been analyzed by means of spectral power amplification (SPA) function. The influence of the parameters of harmonic signal (amplitude and frequency) together with changes of noise intensity have been considered. The SPA is characterized by double peak curve with qualitatively different mechanisms of amplification of the peaks and is examined by Fourier analysis.

An Improved Method for Power Harmonic Analysis Based on Blackman Window and Phase Difference Correction

It is difficult to make the realization of synchronous sampling and the whole cycle truncation when we use the fast Fourier transform (FFT) for power system harmonic analysis .Once the FFT is used, the spectral leakage caused by it will affect the accuracy. Using Blackman window weighted to the harmonic signal, combined with the spectrum analysis of phase, An improved method for power harmonic analysis based on Blackman window and phase shifted difference correction is presented in this paper. The calculation equation of multiple fundamental harmonic signal frequency, amplitude and initial phase angle is derived and the conventional spectral phase correction method is improved. The simulation results show that the calculation accuracy using Blackman window phase correction signal harmonic analysis is improved significantly compared to Hanning window interpolation, Blackman window interpolation and Hanning window phase difference. The algorithm is simple, and has high precision and versatility, which can be applied to high-precision power metering and power quality analysis.

Fast frequency synchronization systems

The new methods of acceleration harmonic signal frequency tracking based on estimates ofinstantaneous frequency and phase, are proposed and investigated. Better efficiency of new systems e.g. quicker transient process and bigger frequency range is proved in comparison with conventional system of frequency synchronization

Application of Linear-Phase Filters in Induction Motor Speed Detection

In rotor-slot-harmonic-based speed detection schemes, a grid-connected induction motor's rotational speed isresolved from the phase of a rotor slot harmonic signal for condition monitoring purposes. In such schemes,frequency-selective digital filters are often applied to attenuate interferences in sampled motor currents before rotorslot harmonic signals are extracted. This paper demonstrates that the use of linear-phase filters, which is a family ofdigital filters with linear phase responses, helps preserve the rotor slot harmonic signal's phase during the filteringoperation. This paper also shows that, for grid-connected induction motors with periodically time-varying loads, therotor slot harmonic signal's frequency is modulated by periodic speed oscillations and hence contains multiple sidebandsin the frequency spectrum. Experimental results further show that linear-phase filters allow for a more accuratedetection of the induction motor speed than filters with nonlinear phase responses.

Simultaneous reduction of IMD3 and IMD5 in bisection laser diode by feedback second harmonic injection

This paper reports a scheme for reducing third and fifth order intermodulation distortion in 1.3µm gain lever laser diode. Third and fifth order intermodulation components are reduced in the laser diode output by second harmonic frequency signals which are extracted from the laser diode itself. The number of RF components required in the linearization circuit for distortion reduction is significantly reduced in this scheme. The active region of the laser diode is split into two sections at a ratio of 0.97:0.03 for realizing gain lever effect. The longer and shorter section currents are fixed as 20mA and 5mA, respectively, corresponding to maximum gain lever. The rate equation approach is used for the analysis. In this scheme, third and fifth order intermodulation components are simultaneously reduced, by injecting second harmonic of two tone signals with appropriate amplitude and phase. A 14.7dB and 9.4dB improvement in third order and fifth order intermodulation respectively, are predicted at 2.4GHz. The magnitudes of third and fifth order intermodulation products are calculated from analytical expressions and the results are found to agree with simulation. Further the effect of RF carrier frequency and channel spacing on distortion reduction is also investigated.

A steady-state point capture-based blind harmonic signal extraction algorithm under the chaotic background

To further improve the performance of blind extraction of harmonic signals under the chaotic background, an algorithm based on the steady-state point capture was proposed. Since energy distribution of the chaotic signal has an important influence on the extraction accuracy, when the frequency of harmonic signals drop in the energy focused region of the chaotic signals, the data after the chaotic signal meet the steady-state point is capable of significantly improving the extraction precision. The solution to capturing steady-state point of typical chaotic system was obtained by solving the Lyapunov exponent. Furthermore, the influence of the frequency interval between harmonic signals was analysed. An empirical constant value of frequency interval to ensure the effective extraction was also derived by a large number of simulation experiments. Simulation results show the effectiveness of the proposed method, and the method provides an effective means to verify the security of chaotic secure communication system.