Rapid filtering method for conversion of multiple digital source sampling frequencies in photoelectric transformer

Abstract

The invention discloses a rapid filtering method for conversion of multiple digital source sampling frequencies in a photoelectric transformer. According to the rapid filtering method, conversion of any fractional multiple sampling frequencies is achieved by cascading interpolation and extraction, and based on a Butterworth analog filter, the cut-off frequency of the analog filter is calculated according to the different digital source sampling frequencies so that the anti-aliasing and anti-image effect can be achieved; an equation parameter of a low pass filter in a domain z is obtained by sampling bilinear transformation according to the principle of the maximum smoothness of a pass band of the filter and a narrowest transitional zone of the filter; the FRR method is adopted for filtering and reverse design, and the output signal sequence of the maximum smoothness and zero-phase distortion is finally obtained. According to the rapid filtering method, in differential protection of the photoelectric transformer, lower-order rapid filtering is achieved so that the maximum output smoothness and the zero phase can be obtained. The rapid filtering method is simple, practical and beneficial for rapid protection, can reduce errors caused by aliasing of the frequencies, and achieves the uniformization of the sampling frequencies.

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] Optical Transformer (OCT) is a type of 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 each OCT may be inconsistent. However, pro...

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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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