JP3047036B2 - Power measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power measuring device using digital technology, and more particularly to a device capable of simultaneously measuring power and integrating power.

[0002]

2. Description of the Related Art Among power measuring devices using digital technology, there is a digital sampling system configured to sample an input voltage waveform and an input current waveform, perform A / D conversion, and calculate the measured value. .

FIG. 5 is a diagram showing a time relation of a basic operation of a conventional power measuring apparatus using such a digital technique. In the figure, the measurement cycle is, for example, 250 ms, and each cycle is divided into an A / D sampling period and a calculation period.

An A / D sampling period is a period for A / D sampling an input voltage and an input current, and the period is determined between 150 ms and 200 ms depending on the frequency of an input waveform. In the meantime, the instantaneous power is obtained and sum of products (Σω (t)).

In the calculation period, each function value (V, A,
W, VA, Var, PF, DEG), and performs processing necessary for display such as scaling.

On the other hand, FIG. 6 is a time relationship diagram of integrated power measurement in a power measuring device using a conventional digital technique. In the figure, when measuring the integrated power, the input voltage waveform and the input current waveform are always digitally sampled without interruption , and from each sampled data obtained here,
Find the instantaneous power for each sampling cycle and convert this
After calculating the total power,
Was.

[0007]

However, in such a conventional method, since sampling is always performed, there is not enough time to perform operations other than the integrated power measurement, and the active power, the reactive power, and the apparent power are not obtained. It was not possible to make other measurements such as phase, phase angle, power factor, etc. simultaneously.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a power measuring apparatus capable of measuring other functions simultaneously with measuring integrated power.

[0009]

A power measuring apparatus according to the present invention multiplies input voltage waveforms and input current waveforms by means of sampling and A / D conversion, and digitally converted voltage data and current data. Means for obtaining instantaneous power, means for summing and summing these instantaneous powers a fixed number of times in accordance with the frequency of the input waveform, means for obtaining average power within a sample period, and sum of product for the average power obtained in each sample period And means for calculating the integrated power by converting the product-sum result of the average power into time.

[0010]

[Operation] The input waveform is sampled for a certain period and A /
D conversion is performed, and the integrated power is obtained based on the conversion result.

Therefore, it is possible to perform a function operation other than the integrated power during a period in which no sampling is performed, and it is possible to measure other functions simultaneously with the integrated power measurement.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual configuration diagram of the present invention. In the figure, reference numeral 1 denotes a voltage input terminal, which is connected to an input circuit 2. The input circuit 2 is connected to an A / D converter 4 that performs A / D conversion according to an output clock of a clock generator 3, and the A / D converter 4 is connected to one input terminal of a computing unit 5. . Reference numeral 6 denotes a current input terminal, which is connected to the input circuit 7. The input circuit 7 is connected to an A / D converter 9 that performs A / D conversion according to an output clock of a clock generator 8, and the A / D converter 9 is connected to the other input terminal of the arithmetic unit 5. . Reference numeral 10 denotes a display, which is connected to an output terminal of the calculator 5.

FIG. 2 is a block diagram showing a main configuration of the arithmetic unit 5 in FIG. That is, the arithmetic unit 5 includes a multiplying unit 11 for multiplying digitally converted voltage data and current data to obtain instantaneous power, and a product-sum unit 12 for multiplying and adding these instantaneous powers a certain number of times according to the frequency of the input waveform. When,
An arithmetic averaging unit 13 for determining an average power during a sample period;
It comprises a sum-of-products unit 14 that sums and calculates the average power obtained in each sample period, and a time conversion unit 15 that converts the sum-of-products result of the average power into time to obtain integrated power. In addition,
Other known function calculation parts are omitted.

FIG. 3 is a flow chart showing the flow of calculation in the calculator 5 of FIG. (Step) The instantaneous power w (t) is obtained by multiplying the A / D converted instantaneous value data i (t) and v (t) of the current for each A / D sampling.

W (t) = i (t) × v (t) (Step) The product of the instantaneous powers w (t) is summed.

Σw (t) (step) A / D sampling determined by the frequency of the input waveform
Repeat the steps only during the period .

(Step) The processing of the step is performed only during the A / D sampling period.
Sum of products of instantaneous power w (t) obtained by repeating
A / D is obtained by dividing the value by the number of samplings n.
The average power W during the sampling period is obtained. W = Σw (t) / n Therefore, the average power W obtained here is the A / D sump.
This is the effective power value during the ring period. (Step) The average power W obtained in the step is
Fixed cycle (measurement cycle from the start of measurement to one cycle before
You. In ()), the average power W obtained by the same procedure is summed up.

{Product sum of average power W obtained in W (step) step}
W is converted to time to obtain an integrated power Wh.

Wh = ΣW × display update rate (ms) / 1 hour (step) Various calculations such as VA, Var, PF, and DEG are performed, and further, calculation value processing such as scaling for displaying them is executed. .

(Step) The designated function value is displayed. FIG. 4 is a time relationship diagram of the integrated power measurement in the power measuring device of the present invention. In the figure, the period (n
The average power value obtained in -1) is W (n-1), the average power value obtained in period (n) is W (n), and the period (n +
The average power value obtained in 1) is defined as W (n + 1).

At the time of the first display update, the integrated power Wh is Wh = W (n−1) × 250 × 10 ⁻³ / 3600.

Subsequently, at the time of the second display update, the integrated power W
h is Wh = {W (n-1) + W (n)} × 250 × 10 ⁻³ / 3600.

Similarly, at the time of the Nth display update, the integrated power Wh is

[0024]

(Equation 1)

## EQU1 ## That is, the power measuring device of the present invention
Represents each sampling cycle in the A / D sampling period.
By summing the instantaneous power w (t) obtained for each period,
And the total instantaneous power of the A / D sampling period Σw (t)
In the A / D sampling period during the calculation period.
Divide the total instantaneous power Σw (t) by the number of samplings n
To obtain the average power W (effective power), where
The average power W obtained and the average power W
By summing the average power obtained and converting this value to time
Thus, the integrated power Wh is obtained. Therefore, the power measurement of the present invention
The device performs sampling during the calculation period of each measurement cycle.
First, the calculation for calculating the integrated power Wh using this period is performed.
And each function value (V, A, W, VA, Var,
Necessary for calculation of PF, DEG) and display of scaling etc.
Measurement and integrated functions
Measurement of values (V, A, W, VA, Var, PF, DEG)
Can be performed simultaneously. When the display 10 is configured to display, for example, three types of data at the same time, the integrated power and the values of the other two types of functions can be displayed at the same time, and the multiple data display function is enabled. You can make use of it.

The integrated current Ah can be measured and displayed by executing the same arithmetic processing.

[0027]

According to the present invention described in detail above, the following effects can be obtained. Since the integrated power is obtained by sampling the input voltage waveform and input current waveform without a continuous sampling, but by sampling for a certain period of time, it is possible to perform a function operation other than the integrated power while sampling is not performed, Simultaneous display of integrated power and other function data, which was impossible with the conventional configuration, can be realized.

When a plurality of types of data are configured to be displayed simultaneously, the function can be effectively used to enhance the measurement contents.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of the present invention.

FIG. 2 is a block diagram showing a main configuration of a computing unit 5 in FIG.

FIG. 3 is a flowchart showing a flow of a calculation in a calculator 5 of FIG. 2;

FIG. 4 is a time relationship diagram of integrated power measurement in the power measurement device of the present invention.

FIG. 5 is a time relation diagram of a basic operation of a power measuring device using a conventional digital technique.

FIG. 6 is a time relationship diagram of integrated power measurement in a power measuring device using a conventional digital technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voltage input terminal 2, 7 Input circuit 3, 8 Clock generator 4, 9 A / D converter 5 Computing unit 6 Current input terminal 10 Display 11 Multiplier 12, 14, Sum-of-product part 13 Arithmetic averaging part 15 Time conversion Department

Claims (1)

(57) [Claims] A means for sampling an input voltage waveform and an input current waveform and performing A / D conversion; a means for multiplying digitally converted voltage data and current data to obtain instantaneous power; Means for summing the product a certain number of times in accordance with the frequency of the sample, means for calculating the average power in the sample period, means for summing the average power obtained in each sample period, and calculating the product sum of the average power. A power measuring device, comprising: means for obtaining integrated power by time conversion.