Interpolation FFT Algorithm Research Articles

Voltage unbalance factor detection based Kaiser- maximum sidelobe decay convolution window and amplitude method

The wide application of distributed energy and nonlinear load causes the voltage unbalance of power grid. This paper establishes an accurate method based on the Kaiser- maximum sidelobe decay (K-MSD) convolution window and three-spectral line interpolated FFT algorithm and the amplitude method to detect the negative sequence voltage unbalance factor. The voltage fundamental wave amplitude is calculated by improved FFT algorithm, which improves the calculation accuracy. Then, the negative sequence voltage unbalance factor is calculated by the amplitude method. It avoids complex phasor calculations. Based on the proposed method the voltage unbalance factor detection system is developed and implemented in a platform. The simulation experiment results show that the proposed algorithm in this paper can effectively realize the accurate detection of unbalance factor under the interference of fundamental wave, harmonics and noise. Compared with the method recommended by the IEC61000-4-27, it is easy to implement and can achieve the same level of precision.

Synchrophasors Determination Based on Interpolated FFT Algorithm

Within the standard IEEE C37.118 applications and proposed hardware structure of a phasor measurement unit (PMU) are described. This paper presents the concept of the system for measuring and transferring synchrophasors from a theoretical aspect. Synchrophasor algorithms are developed in MATLAB/Simulink for the purpose of easier verification and hardware deployment on today’s market available and affordable real time development kits. Analysis of the synchrophasor measurement process is performed gradually. Firstly, by defining the synchrophasor based on three-phase to αβ-transformation and then introducing a discrete Fourier transform (DFT) based on synchrophasor estimation algorithm. Later, accompanying adverse effects resulting from its application are analyzed by means of simulation. To increase accuracy and improve estimation algorithm interpolated discrete Fourier transform (IpDFT) with and without windowing technique is used. To further optimize algorithm performance convolution sum in recursive form has been implemented instead of classical DFT approach. This study was carried out in order to validate described measurement system for the monitoring of transients during island operation of a local power electric system. Finally, simulation and experimental results including error analysis are also presented.

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

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.

Bundle Conductors Corona Current Harmonic Wave Measurement

In order to research high level harmonic wave of six bundle conductors corona current, a measurement system was developed, and a series of wave data was obtained. Corona current is one of important corona characteristic research contents. The corona current measurement system can be used to measure the wide frequency band corona current. Six-bundle conductors was tested, and corona current was obtained. And the current signal collected in this way is safe and reliable. To research the six-bundle conductors’ corona current characteristic, conductor corona current harmonic wave was analyzed, by advanced Hanning windowed interpolation FFT algorithm was adopted. Corona current harmonic characteristics before and after corona onset were compared. Research results show that, after corona onset, corona current odd harmonic increases in evidence, and even-order harmonic increase less relatively. Triple-frequency harmonics and quintuple harmonics increase obviously very much.

A Harmonic Analysis Algorithm Based on Tracking the Fundamental

In the FFT harmonic detection, the detection accuracy is reduced because of asynchronicity between the sampling frequency and the signal of base wave frequency. In order to improve the detection accuracy, a harmonic detection algorithm based on the fundamental frequency tracking is proposed. Firstly windowed interpolation FFT algorithm is used to detect signal of base wave frequency, then the fundamental frequency is tracked and the sampling frequency is dynamically adjusted. Finally, the signal sequence is obtained by quasi synchronous sampling with frequency multiplication technology, and amplitudes and phases of the signal are received with the FFT analysis. Because the sampling frequency synchronization error and the influence of frequency spectrum leakage are reduced, the detection accuracy is improved. This algorithm is applied to the electrical energy harmonic analysis with simple implementation and high accuracy.

Frequency Estimation of Distorted and Noisy Signals in Power Systems by FFT-Based Approach

This paper focuses on the accurate frequency estimation of power signals corrupted by a stationary white noise. The noneven item interpolation FFT based on the triangular self-convolution window is described. A simple analytical expression for the variance of noise contribution on the frequency estimation is derived, which shows the variances of frequency estimation are proportional to the energy of the adopted window. Based on the proposed method, the noise level of the measurement channel can be estimated, and optimal parameters (e.g., sampling frequency and window length) of the interpolation FFT algorithm that minimize the variances of frequency estimation can thus be determined. The application in a power quality analyzer verified the usefulness of the proposed method.

Performance Comparison of Windowed Interpolation FFT and Quasisynchronous Sampling Algorithm for Frequency Estimation

The DFT-based frequency estimations have inherent limitations such as spectral leakage and picket-fence effect due to asynchronous sampling. This paper focuses on comparing the windowed interpolation FFT (WIFFT) and quasisynchronous sampling algorithm (QSSA) for frequency estimation. The WIFFT uses windows to reduce spectral leakage and employs interpolation algorithm to eliminate picket-fence effect. And the QSSA utilizes quasisynchronous weighted iterations for frequency estimation. The accuracy and time complexity of WIFFT and QSSA are theoretically studied. Computer simulations of frequency estimations with noise and fluctuations by using WIFFT and QSSA are performed. Simulations results show that the wideband noise sensitivity of QSSA is lower than that of WIFFT. However, the WIFFT exhibits less time complexity than QSSA.

Broadband Bioimpedance Spectroscopy Based on a Multifrequency Mixed Excitation and Nuttall Windowed FFT Algorithm

Bioimpedance spectroscopy (BIS) has become an important clinical indicator for monitoring the pathological status of biological tissues, and multifrequency simultaneous measurement of BIS may provide more accurate diagnostic information compared with the traditional frequency-sweep measurement technology. This paper proposes a BIS multifrequency simultaneous measurement method based on multifrequency mixed (MFM) signal excitation and a Nuttall windowed interpolation FFT algorithm. Firstly, the excitation source adopts the nine-frequency MFM signalf(9,t), which has excellent spectral characteristic and is very suitable for BIS measurement. On this basis, a Nuttall window is adopted to truncate sample data, and an interpolation FFT algorithm based on Nuttall window is built to perform spectral analysis, in which the parameter correction formula is provided based on polynomial approximation. A BIS measurement simulation experiment is performed on an RC three-element equivalent circuit, and results on the 9 primary harmonic frequencies ranging from 3.9 kHz to 1 MHz show a high accuracy with the impedance amplitude relative error|Ez|<0.3%, and the phase absolute error|Ep|<0.1°. This paper validates the feasibility of BIS multifrequency simultaneous measurement method and establishes an algorithm foundation for the development of practical broadband BIS measurement system.

An Interpolation FFT Algorithm with High Accuracy

To further improving the precision of harmonics measurement, a new interpolation FFT algorithm based on Rife–Vincent (I) window is provided in this paper. First the spectrum leakage of FFT briefly and the frequency response of the Class I Rife- Vincent window is discussed, and then paper analyzes the interpolation algorithm on Rife–Vincent (I) window in detail. At last the cubic spine function is adopted to calculate the frequency and the harmonic amplitude modification coefficient. An example of simulation is given, and simulative calculation results show that Rife–Vincent (I) window interpolation algorithm by using cubic spine function has the amplitude error less than 1×10-6 % , the frequency error less than 1×10-7Hz, and the phase error less than 0.0001%. Comparing with other cosine windows interpolation FFT algorithm, the new interpolation FFT algorithm based on Rife–Vincent (I) window has the highest accuracy.

Simple Interpolated FFT Algorithm Based on Minimize Sidelobe Windows for Power-Harmonic Analysis

This paper focuses on the low-computation harmonic-analysis procedure with sufficient suppression of spectral leakage and picket-fence effect. The interpolated FFT algorithm based on the minimized sidelobe window is considered, and its calculate procedure and formulas are given, which is free of solving high-order equations. The implementation of the proposed algorithm in the digital-signal-processor (DSP) based three-phase harmonic ammeter is also introduced. The proposed algorithm has the major advantages that the calculate formulas for harmonic parameters can be easily implemented by hardware multipliers, making the method a good choice for real-time applications. The simulation and application results validate the accuracy and efficiency of the proposed algorithm.

IFFTC-Based Procedure for Hidden Tone Detection

In this paper a procedure for the detection of hidden tones in the spectrum of a signal is proposed and experimentally evaluated. It is based on the Corrected Interpolated FFT algorithm for the estimation of spectral parameters of nonhidden tones, and on the analysis of the disagreement between measured and expected spectra in order to detect hidden tones. The design of the procedure takes advantage of experimental design techniques in the threshold evaluation

Design and implementation of a fast logarithmic stepped sine for a fixed rate digital network analyzer

A method is presented for measuring transfer function and harmonic distortion with a very accurate 12th-octave stepped-sine analysis between 20 Hz and 20 kHz using a digital fast-Fourier-transform (FFT)-based analyzer. One of the major concerns in developing the algorithm was to obtain maximum measurement speed while maintaining high accuracy. The interpolated FFT algorithm is used, making it possible to reduce the frequency error relative to the perfect 12th-octave frequency to less than 0.1% while keeping the needed amount of measured data, and thus the measurement time, quite low. Despite some small problems with the calibration of the channel, the transfer-function measurement accuracy is better than +or-0.0004 linear error of the amplitude and 0.01 deg in phase in the band from 20 Hz to 10 kHz. In the 10-20 kHz band, the phase error rises to +or-0.1 deg, while the amplitude error remains the same. The dynamic range of the harmonic distortion measurement is about 75 dB. It allows the visualization of each of the harmonics as well as the total harmonic distortion for the first five harmonics in the 20-kHz band.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>