8 results about "Discrete-time Fourier transform" patented technology

The invention discloses a partial discharge signal detection method based on a power frequency voltage transformer and a related product, and belongs to the technical field of insulation detection. The method comprises the following steps: acquiring a power grid side actual voltage signal of a power distribution network cable terminal by means of a power frequency voltage transformer, preprocessing to obtain an original partial discharge signal, and performing discrete time Fourier transform on the original partial discharge signal to obtain a z-domain signal of the original partial discharge signal; fitting the frequency domain response of the power frequency voltage transformer to obtain a z-domain inverse transfer function; and performing digital compensation on the z-domain signal of the original partial discharge signal by using the z-domain inverse transfer function to obtain a compensated z-domain signal, and converting the compensated z-domain signal to a time domain through inverse z transformation to obtain a final original partial discharge signal. Voltage signals are acquired through the original power frequency voltage transformer of the power distribution network, frequency band limitation of the power frequency voltage transformer is overcome through digital compensation, and live detection and online real-time monitoring of partial discharge signals of the power distribution network cable can be realized without power failure and additional installation of the transformer.

The invention discloses a Coriolis flowmeter signal processing method based on adaptive unscented Kalman filter (UKF) and sliding discrete time Fourier transform (SDTFT), and belongs to the field of Coriolis flowmeter signal processing. The method comprises the following steps: firstly, preprocessing a signal by using a band-pass filter; secondly, extracting a signal frequency by adopting zero-cross detection; furthermore, the frequency obtained by zero-cross detection is taken as the reference frequency, and the phase difference of the two paths of signals is extracted in real time by adopting an SDTFT algorithm considering negative frequency correction; and finally, introducing an adaptive process noise covariance adjustment mechanism based on a phase difference change rate, and constructing an adaptive UKF to carry out error correction on the frequency and the phase difference. According to the invention, the accuracy and real-time performance of signal processing of the Coriolis flowmeter under the conditions of strong interference and sudden phase change can be improved.

The application relates to the technical field of power system analysis, and particularly provides a power quality monitoring method and device, which comprises the following steps: sampling power quality parameters by using a three-cycle sampling method; adopting a discrete-time Fourier transform method to analyze the amplitude of each frequency point of a sampling signal; and performing aggregate analysis on the power quality parameters based on the amplitude of each frequency point of the sampling signal to obtain an aggregate spectrum diagram corresponding to the power quality parameters. The technical scheme provided by the application can collect and analyze power quality parameters in a power grid in real time, and accurately judge the power quality state.

The application discloses an FID signal frequency estimation method and system based on improved interpolation DFT, and relates to the technical field of signal processing.The application adds a maximum sidelobe attenuation window to an input signal, derives an initial frequency estimation value under the condition of considering negative spectrum components, and significantly reduces the interference of negative spectrum leakage on frequency estimation on the basis of the initial frequency estimation value; on the basis, the application is no longer limited to discrete integer frequency points, but uses a discrete time Fourier transform (DTFT) to perform spectrum interpolation, thereby effectively alleviating the inherent fence effect of a fast Fourier transform (FFT), and making the frequency estimation no longer limited to the discrete interval of spectrum lines. A high-precision frequency estimation model further constructed can maintain consistent estimation performance in a full frequency band, and overcomes the defects of the existing IpDFT method that the precision fluctuates due to frequency changes. Therefore, higher estimation precision, smaller negative spectrum residual influence, and stronger robustness in a full frequency band can be realized in a complex electromagnetic environment.

The present invention discloses a partial discharge signal detection method based on a power frequency voltage transformer and related products, belonging to the field of insulation detection technology. The actual voltage signal on the grid side of the distribution network cable terminal is collected by means of a power frequency voltage transformer, and the original partial discharge signal is obtained through preprocessing. The discrete time Fourier transform is performed on the signal to obtain the z-domain signal of the original partial discharge signal; the frequency domain response of the power frequency voltage transformer is fitted to obtain the z-domain inverse transfer function; the z-domain signal of the original partial discharge signal is digitally compensated using the z-domain inverse transfer function to obtain the compensated z-domain signal, and then the signal is converted to the time domain through the inverse z-transformation to obtain the final original partial discharge signal. The voltage signal is collected by the original power frequency voltage transformer of the distribution network, and the frequency band limitation of the power frequency voltage transformer is overcome by digital compensation. The live detection and online real-time monitoring of the partial discharge signal of the distribution network cable can be realized without power outage and additional installation of transformers.

The present invention belongs to the technical field of satellite gravity measurement and discloses a method for determining satellite gravity measurement error based on accelerometer radial observation noise, comprising: obtaining a radial observation noise time series of an accelerometer under an observation time length T; performing time-domain windowing on the radial observation noise time series to obtain a radial observation noise time series after time-domain windowing; wherein the window function used is 1 during a satellite orbit-descending period and is -1 during a satellite orbit-ascending period; calculating a discrete-time Fourier transform of the radial observation noise time series after time-domain windowing; substituting the discrete-time Fourier transform into a relationship satisfied between the accelerometer radial observation noise and a gravity field potential coefficient error to obtain a gravity field potential coefficient error; the gravity field potential coefficient error is used to reflect the satellite gravity measurement error; the present invention clarifies the propagation mechanism between the accelerometer radial observation noise and the gravity measurement error, which is of great significance for the payload design and error analysis of gravity satellites.

The invention relates to the field of microphone array wind speed and wind direction measurement, in particular to a microphone array-based wind speed and wind direction measurement method. According to the technical scheme, the method comprises the following steps: synchronously acquiring acoustic signals by adopting microphone arrays which are distributed in central symmetry in east, south, west and north directions, and discretizing to obtain a time domain signal sequence; discrete time Fourier transform is carried out on the time domain signal segments, and an amplitude spectrum is calculated; determining a frequency point index according to the passband frequency band, extracting an energy integral in the passband frequency band, normalizing the energy integral to unit time, obtaining an energy mean value in each direction, calculating synthetic energy through a south-north energy difference and an east-west energy difference, obtaining an average wind speed in combination with an energy-wind speed calibration curve, and calculating a wind direction angle according to the average wind speed. The method is suitable for low-altitude meteorological wind speed and wind direction detection of the unmanned aerial vehicle.

The application provides a calibration method and device of a special-shaped linear array radar, a radar and a storage medium. The method comprises: performing discrete-time Fourier transform on echo intermediate frequency signals obtained by each antenna channel of the special-shaped linear array radar detecting a metal column, to determine actual phases of the echo intermediate frequency signals; based on the actual phases of the echo intermediate frequency signals received by each antenna channel, searching for actual position coordinates of the metal column in a position search range of the metal column by using an optimization problem; based on the actual position coordinates of the metal column, calculating theoretical phases of the metal column detected by each antenna channel; based on the actual phases and the theoretical phases of the echo intermediate frequency signals, determining channel calibration factors of each antenna channel; and using the channel calibration factors to calibrate target echo intermediate frequency signals received by the corresponding antenna channel. The application can avoid the problem of unfocused images caused by different gains and phases of different antenna channels in the special-shaped linear array radar, and improve the radar detection effect.