6results about How to "Low sampling frequency requirement" patented technology

The invention discloses a characteristic higher harmonic low-frequency sampling method, an APF, equipment and a storage medium, belongs to the technical field of power system harmonic detection, and solves the problem of how to reduce the sampling frequency of characteristic higher harmonics. According to the method, the characteristic higher harmonic signal is sampled into the fundamental wave signal by adopting the sampling frequency with lower frequency, so that the amplitude of the characteristic higher harmonic signal is obtained; meanwhile, sampling the characteristic higher harmonic signal into a direct current signal by adopting a second sampling frequency with a relatively low frequency, so as to obtain the phase of the characteristic higher harmonic signal; combining the known angular frequency of the characteristic higher harmonic signal to obtain all characteristics of the characteristic higher harmonic signal; the sampling frequency is reduced to a fraction or even lower than that of a traditional method, and the sampling frequency requirement is remarkably reduced; a high-frequency sampling chip does not need to be upgraded, and system modification cost is reduced; the phase relative error is greatly reduced in a low-order harmonic band, the overall phase error is controlled within 5%, and the phase detection precision is improved.

The embodiment of the application discloses a DC support capacitor online state monitoring method and device based on PINN, the method comprises the following steps: obtaining a plurality of groups of charge-discharge data of voltage change with time under different capacitance values of DC support capacitor, and determining a training set and a verification set; using the AdamW algorithm to train a preset PINN model according to the training set, adaptively updating the loss function weight and the network weight until a first preset iteration number is reached, and obtaining the model parameters of the trained PINN model; using the L-BFGS algorithm to update the model parameters, and verifying the final PINN model according to the verification set; online obtaining pre-charge data of the DC support capacitor to be measured, and applying the final PINN model to monitor the state of the DC support capacitor to be measured. Through the above method, the embodiment of the application can effectively reduce the influence of the measurement signal-to-noise ratio on the prediction result, and is suitable for capacitor value prediction in a wide range of capacitor intervals under the same topology.

The invention relates to the technical field of equipment security, in particular to an Internet of Things equipment identity authentication method based on online learning. Comprising the following steps: acquiring a plurality of target equipment signals of target Internet of Things equipment in a target time window; performing feature extraction on the plurality of target equipment signals to obtain an initial radio frequency fingerprint of the target Internet of Things equipment; performing dimension reduction on the initial radio frequency fingerprint according to a semi-supervised dimension reduction algorithm to obtain a target radio frequency fingerprint; and inputting the target radio frequency fingerprint into an online learning authentication model to obtain an identity authentication result of the target Internet of Things equipment. According to the method, the accuracy in identity authentication of the Internet of Things equipment is improved, and the problems of high-dimensional data compression and real-time efficient authentication in a dynamic environment are solved.

The invention discloses an ultrasonic transducer instantaneous input power and impedance characteristic real-time measurement method and system based on discrete Fourier transform, and the method comprises the steps: decomposing voltage and current signals into frequency components through Fourier transform, and accurately calculating the amplitude and phase at a specific frequency, thereby calculating the corresponding input power, and achieving the real-time measurement of the impedance characteristic of the ultrasonic transducer. And the method can also be used for calculating the impedance of the ultrasonic transducer on the working frequency. According to the invention, the impedance characteristic of the ultrasonic transducer is monitored in real time, and whether the equipment is damaged, aged or in a dangerous idle state can be evaluated according to the impedance characteristic, so that equipment failure or safety risk is effectively avoided. The method is not only suitable for ultrasonic equipment in medical treatment, but also can be applied to the industrial fields of ultrasonic welding, ultrasonic cleaning, ultrasonic flaw detection and the like, and a more stable and reliable working state monitoring scheme is provided for various ultrasonic systems.

The application discloses a converter near power frequency impedance measurement method, system, device and storage medium, obtains steady voltage / current data when the converter is in steady operation, superimposes a first group of voltage / current data when a voltage or current small disturbance harmonic signal with a frequency of f is added, superimposes a second group of voltage / current data when a voltage or current small disturbance harmonic signal with a frequency of 2f0-f is added, subtracts the first group and the second group of voltage / current data from the steady voltage / current data after the first group and the second group of voltage / current data are aligned with the steady voltage / current data through first and second zero-crossing time deviations, and obtains harmonic data; and calculates sequence impedance and coupling impedance of the converter at the frequencies of f and 2f0-f. The technical scheme can realize accurate measurement of near power frequency impedance of the converter, realize accurate analysis of a signal containing a power frequency component in a near power frequency band under the condition that a sampling law is met, and reduce the requirement on a sampling frequency, and the accuracy and feasibility are considered.

The application provides a target detection method based on FMCW-OAM radar target imaging. Since the vortex electromagnetic wave carries the orbital angular momentum OAM, more target information can be provided in radar imaging and target detection. The vortex phase is added in the traditional frequency-modulated continuous wave FMCW radar, the azimuth angle imaging performance of the FMCW radar is improved, the measurement accuracy is not affected by the actual azimuth angle of the target, the distance and the speed of the target, and the azimuth angle detection range is widened. Compared with the pulse OAM radar, the FMCW-OAM radar has the advantages of small short-distance detection blind area, high measurement accuracy, low power consumption and low sampling frequency.