A Frequency Measurement System for Power Frequency Signals with Universal Voltage Input

Abstract

A universal voltage input power frequency signal frequency measurement system is mainly composed of a voltage conversion circuit, a conversion voltage self-adjustment and amplification circuit, a band-pass filter circuit, a comparator circuit, a digital signal processing circuit and a power supply circuit. The voltage conversion circuit can be applied to a 0 to 300V AC power frequency signal inputand can satisfy most of the application occasions of a power system. The conversion voltage self-adjustment and amplification circuit can automatically adjust the amplification factor of an output voltage according to the amplitude of the output voltage of the voltage conversion circuit to meet the weak power frequency signal frequency detection requirement. The band-pass filter circuit achievesa good selectivity of power frequency signals with a center frequency around 50Hz to suppress the interference of high-frequency signals. The comparator circuit converts an input AC signal into a DC signal, and the signal output by the comparator circuit does not require signal isolation and can be directly connected to the digital signal processor to complete the frequency calculation. The universal voltage input power frequency signal frequency measurement system in the invention has the characteristics of simple circuit, small phase delay, wide application range and high reliability.

Description

technical field [0001] The application belongs to the technical field of electrical systems, and in particular relates to the frequency measurement technology of relay protection devices. Background technique [0002] In the traditional power system relay protection device, the input signal is the power frequency (50Hz) signal transmitted by the secondary transformer, the voltage value may be tens of volts to hundreds of volts, and the relay protection device needs a cycle (20mS) Collect real-time data with a fixed number of points (24 points or 40 points). According to these data, the relay protection device must perform real-time protection algorithm calculations to determine whether there are various faults such as short circuit or grounding in the power grid. In order to ensure the accuracy and reliability of the protection algorithm, the data collected by the cycle wave should be an integral multiple of the actual frequency (50Hz), and the phase delay should be as small...

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Problems solved by technology

[0003] The purpose of the present invention is to overcome the problems of complex circuits, long delays for input signals, difficulty in ensuring accuracy, or narrow application ranges in power system frequency measurement methods in the prior art, and propose a general voltage input power frequency signal frequency measuring system

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