Meng Zhuo

Bio: Meng Zhuo is an academic researcher from Hunan University. The author has contributed to research in topics: Time domain & Signal. The author has an hindex of 7, co-authored 17 publications receiving 186 citations.

Harmonic Estimation Using Symmetrical Interpolation FFT Based on Triangular Self-Convolution Window

Abstract: Harmonic estimation is an important topic in power system signal processing. Windowed interpolation fast Fourier transformation (WIFFT) is an efficient algorithm for power system harmonic estimation, which can eliminate the errors caused by spectral leakage and picket fence effect. However, the fitting polynomial in the interpolation procedure contains both even and odd terms, and this increases the computational burden. This paper proposes a simple symmetrical interpolation FFT algorithm, where the even terms are removed from the fitting polynomial based on the triangular self-convolution windows (TSCW). The polynomials for frequency and amplitude computations are provided. Considerable leakage errors and harmonic interferences can be suppressed by the TSCW. Accurate estimations of harmonic parameters can be obtained via the fitting polynomial and the TSCW, both with adjustable order to fulfill different accuracy and speed requirements of practical power harmonic measurement. Simulation results and measurements have validated the proposed method.

Harmonic analysis method based on Kaiser self-convolution window dual-spectrum line interpolation FFT (Fast Fourier Transform) and device thereof

Abstract: The invention discloses a harmonic analysis method based on Kaiser self-convolution window dual-spectrum line interpolation FFT (Fast Fourier Transform) and a device thereof. The method comprises the following steps of sampling a signal: sampling a time-domain continuous signal, and discretizing to obtain an infinitely long discrete sequence; windowing a four-order Kaiser self-convolution window function: performing four-order Kaiser self-convolution window operation on the infinitely long discrete sequence; performing N-point FFT on a windowed and truncated signal to obtain the discrete spectrum of the signal; determining the peak parameter of the discrete spectrum: searching the local spectrum peak of each integer harmonic frequency around the integer harmonic frequency; and calculating a harmonic parameter: solving a coefficient alpha by adopting a discrete spectrum interpolation correction formula based on an LSM (Least Square Method), and calculating parameters such as a harmonic frequency, an amplitude, an initial phase angle and the like. Due to the adoption of the method, the fundamental and harmonic components of a tested signal can be detected rapidly and accurately, and accurate frequency measurement is realized; and the method is convenient for implementing an embedded system, and the tested signal can be detected continuously for a long time.

Dynamic signal phasor measurement method based on time domain quasi-synchronization

Abstract: The invention discloses a dynamic signal phasor measurement method based on time domain quasi-synchronization. The dynamic signal phasor measurement method based on the time domain quasi-synchronization comprises the following steps: estimating the fundamental wave frequency of a sampled signal by a time domain quasi-synchronization sampling algorithm; carrying out time domain quasi-synchronization on the sampled signal by the estimated value of the fundamental wave frequency; reconstructing a quasi-synchronization sampling sequence by Newton interpolation; carrying out frequency domain analysis on the reconstructed quasi-synchronization sampling sequence by FFT (fast Fourier transform) to obtain a dynamic signal phasor measurement result. According to the method, the influence on the measurement precision of the traditional phasor measurement method by frequency spectrum leakage caused by nonsynchronous sampling is avoided. The computation complexity of the dynamic signal phasor measurement method based on the time domain quasi-synchronization is smaller than the computation complexity of the traditional phasor measurement method based on the discrete Fourier transform, and the dynamic signal phasor measurement method based on the time domain quasi-synchronization is easy to realize in an embedded system.

Harmonic time frequency characteristic parameter estimating method based on fast S conversion and analysis meter

Abstract: The invention discloses a harmonic time frequency characteristic parameter estimating method based on fast S conversion and an analysis meter The harmonic time frequency characteristic parameter estimating method comprises the steps of 1, analog-digital conversion, 2 low-pass filtering, and 3 fast S conversion, thus obtaining a harmonic time frequency characteristic parameter outcome The invention also comprises the analysis meter The harmonic time frequency characteristic parameter estimating method is less in calculated amount, high in efficiency and high in practicability and has a capability of accurately extracting the harmonic time frequency characteristic parameters from complex distorted signals The analysis meter is simple in structure and reasonable in configuration

Method for extracting time-frequency parameters of power quality disturbance signals on basis of fast K-S (Kaiser-S) transformation

Abstract: The invention discloses a method for extracting time-frequency parameters of power quality disturbance signals on the basis of fast K-S (Kaiser-S) transformation. The method includes steps of (1), sampling the tested samples; (2), performing the fast K-S transformation on the tested signals; (3), repeating executing the step (2) until amplitudes, phases and start-stop and sudden-change moments of all the disturbance signals are analyzed, and extracting the time-frequency parameters of the power quality disturbance signals. Compared with the prior art, the method has the advantages that Kaiser windows replace Gauss windows for traditional S transformation, widths and heights of Kaiser window functions can be adaptively adjusted along with change of frequencies, and the energy accumulation and frequency adaptive adjustment capacity of time-frequency analysis of the traditional S transformation can be improved; the computational complexity can be reduced by means of judging characteristic frequencies; the method is wide in application range, and the fast K-S transformation and the method for extracting the time-frequency parameters of the power quality disturbance signals have a wide application prospect in fields of vibration signal analysis, fault diagnosis, pattern recognition, noise measurement and biomedical examination.

Adaptive Feedforward Algorithm Without Grid Impedance Estimation for Inverters to Suppress Grid Current Instabilities and Harmonics Due to Grid Impedance and Grid Voltage Distortion

Abstract: The performance of the grid-connected inverter was affected by the uncertainty of the grid conditions including the background distortion and the grid impedance. Typically, the feedforward of the grid voltage at the point of common coupling (PCC) highly suppressed the grid current harmonics caused by the grid voltage distortion; however, the PCC grid usually had a nonnegligible grid impedance, and the PCC voltage feedforward aroused serious grid current harmonics or instability. This study proposes a novel adaptive algorithm for the PCC voltage feedforward to work well with the varied grid impedance. In the proposal, the band-pass filters at the harmonic frequencies are used to detect the variation of the grid impedance as well as to facilitate the adaptive PCC voltage feedforward. It is not necessary to inject an additional harmonic to estimate the grid impedance. The basic principles as well as the realization and logic of the proposed algorithm are detailed, and some selected waveforms are provided to verify the superior performance. Compared with the typical robust design or adaptive control, the proposed algorithm does not have to sacrifice the dynamic or the harmonics rejection performance, or to use the on or offline grid impedance estimation.

Research on a Composite Voltage and Current Measurement Device for HVDC Networks

Abstract: With the global trend to develop digital substation automation systems, measurement devices are required to be reliable, of small size and light weight and of acceptable accuracy in a wide frequency band. This article presents a combined high voltage direct current measurement method which comprises the above-mentioned features that makes it suitable for smart grids protection and control applications. The proposed measurement method utilizes Hall sensor array for dc current measurement. DC voltage is measured using a voltage divider circuit while the harmonic currents are measured using a square Rogowski coil made of four straight bars along with a high precision digital integration algorithm. A four-spectral line interpolation fast Fourier transform algorithm based on trapezoidal convolution window is proposed to improve the extraction accuracy of the dc and harmonic components from the measured signal. Experimental results show that the error variation of the proposed method is less than 0.098% for voltage measurement while it is less than 0.104% for current measurement. The harmonic measurement ratio error is less than 0.2% and the angle error is less than 8'.

Power harmonic and interharmonic detection method in renewable power based on Nuttall double-window all-phase FFT algorithm

Abstract: Harmonics and interharmonics adversely affect power grids. The fast Fourier transform (FFT) algorithm is one of the most commonly used methods for harmonic analysis. However, in practical applications, the accuracy of harmonic analysis can be seriously affected by fence effect and spectral leakage, which are undesired characteristics inherent to discrete Fourier transforms. Moreover, when non-synchronous sampling is carried out, the phase measurement is not accurate enough, and there is a large error in the identification of interharmonics. In order to improve the measurement precision, the method of all-phase spectrum analysis is used, since it has the characteristics of phase invariance and good spectral leakage suppression. A novel method based on improved Nuttall double-window all-phase FFT is proposed by improving the window function and the spectrum correction method for achieving higher precision. Through simulation and experimental verification, the proposed algorithm has proven to perform better than the traditional algorithms both for the detection of harmonics and interharmonics. In addition, the computation burden is not considerably increased when compared to such algorithms, which allows the on-line use of the proposed algorithm.

A General Noise-Resilient Technique Based on the Matrix Pencil Method for the Assessment of Harmonics and Interharmonics in Power Systems

Abstract: This paper presents a high-accuracy technique for the assessment of harmonics and interharmonics in power systems. In the proposed method, a generalized eigenvalue problem is solved by making use of the matrix pencil method. It is a general method in the sense that it has the ability to predict the frequency, amplitude, and relative phase of frequency components present in a given signal, while the dc-off set and damping factors can be accurately estimated. It also offers a noise-resilient feature which helps to efficiently analyze the noise-contaminated signals. It shows a good performance in dealing with modulated signals as well. Due to its excellent accuracy, the proposed method is foreseen to properly work for the estimation of phasors which is a crucial need in the electrical networks. Different simulation and experimental cases are presented to evaluate the efficiency of the proposed method.