Power system frequency measuring circuit

Abstract

The invention discloses a power system frequency measuring circuit which comprises a mutual inductor circuit, a signal conditioning and filtering circuit, a two-stage clamping circuit, a two-stage gain circuit, a hysteresis comparison circuit and a biasing circuit which are connected in sequence. The mutual inductor circuit converts a high-voltage signal of a primary side into a low-voltage signal of a secondary side, and electrically isolates the signal at the same time; the signal conditioning and filtering circuit is used for conditioning an output signal of the mutual inductor to a proper amplitude value and carrying out low-pass filtering on the output signal so as to filter high-frequency interference; the two-stage clamping circuit clamps a preceding-stage large-amplitude signal to a small-amplitude signal; the two-stage gain circuit amplifies a preceding-stage signal; and the hysteresis comparison circuit compares the input signal which is finally amplified by the two stages with a reference signal, and outputs a stable square wave signal with the same frequency as the input signal, and the square wave signal is used for frequency measurement of a post-stage CPU (Central Processing Unit). According to the invention, high signal frequency measurement resolution and wide dynamic range can be ensured, harmonic waves and inter-harmonic waves can be measured at the same time, and the frequency measurement precision is high.

Description

technical field [0001] The invention relates to the field of power systems, in particular to a power system frequency measurement circuit. Background technique [0002] Power system frequency measurement is an indispensable indicator, which is related to the calculation of various harmonics and power factors in the power field. It is widely used in fault recording, power quality monitoring, distribution network intelligent terminals, relay protection and other fields. . [0003] At present, there are many frequency measurement methods, the designed frequency measurement circuits are not the same, and the measurement indicators that can be achieved are uneven. There are mainly the following problems: the frequency measurement result is unstable under the rated value; the dynamic range of the frequency measurement signal amplitude is relatively small. The frequency measurement accuracy of small, large and small amplitude signals is not high; the harmonics superimposed on the ...

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Problems solved by technology

[0004] In order to solve the problems in the power system frequency measurement circuit that the frequency measurement result is unstable under the rated value, the dynamic range of the frequency measurement signal amplitude is small, and the harmonics and interharmonics affect the frequency measurement accuracy, etc., the present invention provides a frequency measurement The circuit can accurately measure the signal frequency of the rated value, large value, small amplitude, and superimposed harmonics and inter-harmonics. The dynamic range of frequency measurement is wide and the accuracy is high.

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