JPS6340867A - Amplitude value operation apparatus - Google Patents

Abstract

PURPOSE:To enhance operational accuracy, by altering a sampling interval corresponding to frequency inputted. CONSTITUTION:AC input is applied to an operational processing part 4 through a filter 1, a sample holding circuit 2 and an A/D converter circuit 3 but frequency operation other than amplitude value converting processing is performed in the processing part 4. A clock cycle is corrected on the basis of the frequency, which is obtained by said processing part 4, by a correction circuit 6 to correct sampling frequency so that data becomes 90 deg. as an electric angle. The data becoming 90 deg. as the electric angle is calculated by the sampling frequency corrected and, by this method, the enhancement of operational accuracy is achieved even when the frequency of an AC signal changes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for sampling an AC signal input and calculating an amplitude value of this input.

[Prior Art] Generally, the amplitude value of an AC waveform as shown in FIG.
I”=x(m)”+x(m-1)”, but
Data, (m) and data x (m-1) are only when the electrical angle is 90 degrees lx I 2:x(m)"+x(m-1)"
holds true.

Here, X is the AC input waveform, expressed as x=Xsinωt (X is the amplitude value of the waveform, ω is the angular velocity of the waveform, and indicates time), and x(m) is the data at time m seconds. ,x(
m-1) is data at time m-1 seconds.

Figure 2 shows a block diagram of a conventional amplitude value calculation device. In Figure 2, 1 is an input waveform shaping filter, 2 is a sample hold circuit, and 3 is an analog/digital conversion circuit (A/D conversion circuit). .

Reference numeral 4 designates an arithmetic processing unit that performs the above-mentioned amplitude value calculation processing on the digital output from the A/D conversion circuit 3, and 5 a clock generation circuit that outputs a clock that controls the sampling interval in the sample and hold circuit.

Next, the operation will be explained. First, exchange human power X = Xsin
After ωt is shaped by the input waveform shaping filter 1,
Data for calculation [x (m).

x(m-1)] is sampled by the sample hold circuit 2 at a sampling frequency corresponding to the fundamental frequency. That is, a sampling frequency that provides 90 degrees in electrical angle is selected, and sampling is performed at the timing using the clock from the clock generation circuit 5.

Thereafter, the signal is digitally converted by the A/D conversion circuit 3 and then subjected to necessary amplitude value calculation processing by the calculation processing section 4.

[Problems to be Solved by the Invention] However, since such a conventional amplitude value calculation device is configured as described above, when the frequency of the input waveform deviates from the fundamental frequency, the clock Since sampling is performed at fixed time intervals, the sampled data does not correspond to 90 degrees in electrical angle, which causes an error in the calculation results.

This invention was made to solve the above-mentioned problems, and its purpose is to provide an amplitude value calculation device that improves calculation accuracy by making it possible to change the sampling interval according to the frequency of AC input. shall be.

[Means for Solving the Problems] An amplitude value calculation device according to the present invention includes a sample hold circuit that samples the AC signal at a required timing and holds the sampled value in order to calculate the amplitude value of the AC signal. , a clock generation circuit that supplies the sample and hold circuit with a clock that controls the sampling interval in the sample and hold circuit, and a calculation means that calculates the amplitude value of the alternating current signal based on the output from the sample and hold circuit. A frequency detection means for detecting frequency information of the alternating current signal, and a correction device for outputting a signal to the clock generation circuit to change the clock generation timing in order to change the sampling interval according to the frequency from the frequency detection means. It is equipped with a circuit.

[Function] In the amplitude value calculation device according to the present invention, the sample and hold circuit samples an AC signal, and then the calculation means calculates the amplitude value. At this time, the frequency information of the AC signal is detected by the frequency detection means and corrected. A signal for causing the circuit to change the clock generation timing according to the detected frequency information is output to the clock generating circuit, thereby changing the sampling interval according to the detected frequency.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
FIG. 1 is a block diagram showing an amplitude value calculation device as an embodiment of the present invention. In FIG. 1, 1 is an AC signal input waveform shaping filter, 2 is an AC signal (analog 3 is an A/D conversion circuit that converts the output from the sample and hold circuit 2 into a digital value; 4 is an A/D conversion circuit that samples the output from the A/D conversion circuit 3; An arithmetic processing unit (this arithmetic processing unit 4) performs the above-mentioned amplitude value calculation processing on the digital output.

5 is a clock generation circuit that outputs a clock for controlling the sampling interval in the sample and hold circuit 2; 6 is an arithmetic processing unit 4; This is a correction circuit that outputs a signal to the clock generation circuit 5 for changing the clock generation timing in order to change the sampling interval according to the frequency of the calculated AC signal.

Next, the operation will be explained. AC input is filter 1.
It is converted into a digital value via the sample hold circuit 2 and the A/D conversion circuit 3, and is input to the arithmetic processing section 4, which performs frequency calculation in addition to necessary amplitude value calculation processing. . Then, this arithmetic processing unit 4
The correction circuit 6 corrects the clock period using the frequency obtained in , and corrects the sampling frequency so that the data x (m) and x (m-1) are 90 degrees in electrical angle. . With this corrected sampling frequency, two data x that are 90 degrees in electrical angle
(m) and x(m-1) can be found, and the amplitude value can be calculated with high accuracy.

[Effects of the Invention] As described above, according to the present invention, the sampling frequency is corrected by correcting the clock period according to the frequency of the AC signal, so that two As a result, even if the frequency of the AC signal changes, the amplitude value can be determined with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an amplitude value calculation device as an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional amplitude value calculation device, and FIG. 3 is an AC signal input waveform diagram. In the figure, 1 - manual waveform shaping filter, 2 - sample hold circuit, 3 - A/D conversion circuit. 4--arithmetic processing section, 5--clock generation circuit, 6.--correction circuit. In addition, in one figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In order to calculate the amplitude value of an AC signal, a sample hold circuit that samples the AC signal at a required timing and holds the sample value, and a clock that controls the sampling interval in the sample hold circuit are provided in the sample hold circuit. frequency detection means for detecting frequency information of the alternating current signal; 1. An amplitude value calculation device comprising: a correction circuit that outputs a signal to the clock generation circuit to change the clock generation timing in order to change the sampling interval according to the frequency of the signal.