Zhaosheng Teng

Harmonic Phasor Analysis Based on Improved FFT Algorithm

An approach for power system harmonic phasor analysis under asynchronous sampling is proposed in this paper. It is based on smoothing sampled data by windowing the signal with the four-term fifth derivative Nuttall (FFDN) window, and then calculating harmonic phasors in the frequency domain with an improved fast Fourier transform (IFFT) algorithm. The applicable rectification formulas of the IFFT are obtained by using the polynomial curve fitting, dramatically reducing the computation load. The FFDN window can effectively inhibit the spectral leakage and the picket fence effect can be modified by the IFFT algorithm under asynchronous sampling, and the overall algorithm can easily be implemented in embedded systems. The effectiveness of the proposed method was analyzed by means of simulations and practical experiments for multifrequency signals with the fluctuation of the fundamental frequency and with the presence of white noise and interharmonics.

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.

Design of Power Quality Monitoring System Based on LabVIEW

A multifunctional vitual power quality monitoring system is designed and implemented in LabVIEW environment. S-transform is introduced and applied to perform time-frequency analysis on power quality disturbances. The root mean square(RMS) value, the waveforms of three-phase voltage and current, the harmonic components, the total harmonic distortion(THD) and S-transform analysis waveforms of the three-phase voltage and current signals can be calculated and displayed in the system. Furthermore, the remote transfer of measured results is implemented using the AppletVIEW Toolkit in LabVIEW adopting a B/S framework. Measurement results show the feasibility and validity of the system.

Accurate Algorithm for Harmonic Analysis Based on Minimize Sidelobe Window

Errors caused by spectral leakage and picket fence effect can be reduced by the windowed interpolation FFT algorithm in the electric power harmonic analysis. In this paper, the spectral characteristics of minimize sidelobe window were analyzed and the interpolation FFT algorithms for electrical harmonic analysis based on the minimize sidelobe window were proposed. The applicable formulas of the interpolation were obtained by using polynomial curve fit functions, and subsequently calculating burden was dramatically reduced. The simulation results indicate that, with non-synchronized sampling and non-integral period truncation, the proposed method gave the accurate results for weak harmonic extraction and complicate harmonic analysis. The proposed method was applied in the three phase multiply function power energy meter, which verified the usefulness of the proposed method.