A Fast Filtering Method for Sampling Rate Conversion of Multiple Digital Sources in Photoelectric Transformer

Abstract

The invention discloses a fast filtering method for the sampling rate conversion of multiple digital sources in a photoelectric transformer. The conversion of any fractional sampling frequency is realized by cascading interpolation and extraction. The Butterworth analog filter is used as the Based on the calculation of the analog filter cut-off frequency according to different digital source sampling frequencies to achieve anti-aliasing and anti-image effects; then according to the principle of the largest flat passband and the narrowest transition band of the filter, and sampling bilinear transformation, we get Z-domain low-pass filter equation parameters; finally, the FRR method is used for filtering and phase inversion design, and finally the output signal sequence with maximum flatness and zero phase distortion is obtained. The method provided by the present invention can realize fast filtering with lower orders in differential protection of photoelectric transformers to obtain maximum output flatness and zero phase; it is simple and practical, is conducive to fast action of protection, and can reduce frequency aliasing The resulting error realizes the normalization of the sampling frequency.

Description

technical field [0001] The invention relates to a fast filtering method for sampling rate conversion of multiple digital sources in a photoelectric transformer, which processes signals based on zero phase and maximum flat algorithms, and belongs to infinite impulse response (IIR) filter technology. Background technique [0002] The photoelectric transformer (OCT) is a kind of electronic current transformer (Electronic Current Transformer, ECT). In recent years, the research on electronic current transformers has made great progress. At the same time, with the promotion of digital substations, the application of photoelectric transformers has entered the practical stage. ECT / OCT is often integrated inside the gas insulated switchgear (GIS) or installed on the circuit breaker and transformer bushing, and supplied by the respective primary equipment manufacturers. Therefore, when OCT is supplied by different primary equipment suppliers , the sampling data output frequency of e...

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Problems solved by technology

The window function method and the frequency sampling method are simple in design and easy to apply, but they can only carry out limited control on the design index; the equal-ripple design method based on the Chebyshev principle can make the best approximation to the ideal filter, so better The passband and stopband characteristics; but the ripple characteristics of the Chebyshev passband affect the output amplitude characteristics

[0005] In the process of modern multi-source sampling processing, cubic spline interpolation is usually used to convert the signal from high frequency to low frequency; due to the high frequency data mixed in cubic spline interpolation, the spectrum is confused and a large differential current is generated. , causing malfunction of the device

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