JPH063381A - Adjusting device for power measuring instrument - Google Patents

Abstract

PURPOSE:To achieve an adjusting device for measuring instruments for power which dispenses with reading of much data and reduces time for adjusting the measuring instrument for power by reducing the number of measuring instruments including a low-distortion sinusoidal wave generator. CONSTITUTION:The title device for compensating the phase error of a measuring instrument by a compensation function stored in a storage element of the measuring instrument for power applies three types of sinusoidal waveform signals to a measuring instrument 50 for power successively while shifting the phase difference between voltage input and current input by 90 degrees each for a power supply 9, a signal source 6, a phase shifter 7, a voltmeter 8, a writer 13, and sinusoidal wave signals with two types of input frequencies, thus calculating the phase error between the voltage input and the current input according to a wattage operation output including phase error characteristics. A means for calculating the compensation coefficient of compensation function which is an equation of the first degree of input frequency from the phase error and two types of input frequencies and for storing the compensation coefficient of the calculated compensation function in the storage element of the measuring instrument for power is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power meter using digital technology, and more particularly to a power meter adjusting device for correcting a phase error between an input voltage and an input current generated in an input transformer.

[0002]

2. Description of the Related Art FIG. 6 shows a block diagram of a conventional example. Figure 6
FIG. 6A is a power meter configured only with an analog circuit, and FIG. 6B is a power meter using a digital technique in the calculation part. In FIG. 6A, the signal line to be measured is often a high-voltage, large-current power supply line, and the input signal is insulated and stepped down by the transformer 1a and input to the analog arithmetic circuit 2. As for the output of the analog arithmetic circuit 2, the power value is displayed by the display means 3a. On the other hand, FIG. 6 (B)
In, the input signal is insulated and stepped down by the transformer 1b, input to the A / D converters 4a and 4b, and converted into a digital value. The outputs of the A / D converters 4a and 4b are input to the programmable digital calculator 5. The digital arithmetic unit 5 outputs the calculation result to the PWM (Pulse Width Modu
lation) After being converted into a signal such as a signal, it is sent to the display means 3b, and a power value, a voltage value, an effective current value, a reactive power, an apparent power,
Displays the phase angle, power factor, frequency, etc.

Here, the above-mentioned transformers 1a and 1b are
It acts as a phase lead element between the primary side input and the secondary side output, and since the phase advance differs between voltage conversion and current conversion, a phase error occurs between the input voltage and the input current. Furthermore, this phase error is a function of the input frequency,
This phase error becomes a factor that reduces the accuracy of the entire power meter.

In the power meter using the analog circuit shown in FIG. 6A, a complicated circuit and a great amount of adjustment man-hours are required to accurately correct the phase error. Therefore, the power meter without the correction function is required. Most instruments. On the other hand, FIG.
In the power meter using the digital technique shown in (B), the circuit operation can be defined by the internal program, and the phase error can be corrected by the correction function.

As a method of correcting the phase error with a correction function, there is a power meter adjusting method according to Japanese Patent Application No. 4-51411. In this method, a low distortion sine wave is input and A
The digital output from the / D converter is directly taken out as serial data, the input waveform is estimated by the least square method, and the correction coefficient is calculated so as to correct the estimated waveform.

[0006]

However, Japanese Patent Application No. 4-5.
The power meter adjusting method according to No. 1411 requires a low distortion sine wave generator for estimating the input waveform with high accuracy and an interface for taking in the serial data. Further, in order to estimate the input waveform with high accuracy by the least squares method, it is necessary to import a large amount of data, and since the amount of calculation is huge, this acquisition time and the calculation time of the acquired data become long, Adjustment time of the power meter becomes long. Therefore, an object of the present invention is to reduce the number of measuring instruments such as a low-distortion sine wave generator and the like, and to realize an electric power meter adjusting device in which a large amount of data acquisition processing is unnecessary and the electric power meter adjusting time is short.

[0007]

In order to achieve such an object, the present invention provides a power meter adjusting device for correcting a phase error of a meter by a correction function stored in a storage element of the power meter. , A power supply for supplying a power supply voltage to the power meter, a signal source for applying a sine wave signal of an arbitrary input frequency to a voltage input terminal of the power meter, and a phase shift of the sine wave signal of the signal source. A phase shifter applied to a current input terminal of the power meter, a voltmeter for measuring a power value calculation output of the power meter, a writer for writing the correction coefficient in a storage element of the power meter, and A signal source is controlled to apply sinusoidal signals of two types of input frequencies to the power meter, and a phase shifter is controlled to input a voltage input and a current input for each sinusoidal signal of the two types of input frequencies. Phase difference of 90 degrees Then, three kinds of sine wave signals are sequentially applied to the power meter, and the power value calculation output including the phase error characteristic of the power meter at each input measured by the voltmeter is taken in. From this power value calculation output The phase error between the voltage input and the current input is calculated, and the correction coefficient of the correction function, which is a linear expression of the input frequency, is calculated from the phase error and the two types of input frequencies, and the writer is controlled to perform the calculation. Arithmetic control means for storing the correction coefficient of the corrected correction function in the storage element of the power meter.

[0008]

[Function] With the power meter adjusting device for two types of frequencies,
By obtaining the correction coefficient of the phase error correction function only from the measurement outputs of three points with different phase differences, the number of measuring devices is reduced, the process of taking in a lot of data is unnecessary, and the adjustment time of the power meter is shortened. .

[0009]

The present invention will be described in detail below with reference to the drawings.
FIG. 1 is a configuration block diagram showing an embodiment of a power meter adjusting device according to the present invention. 6 is a signal source that supplies a sine wave to the voltage input terminal of the power meter 50, 7 is a phase shifter that changes the phase of the signal source 6 and supplies the current input terminal of the power meter 50, and 8 is a power meter. 50 power value calculation output signal 10
A voltmeter for detecting 0, 9 is a power source for supplying the power meter 50, 10 is a signal source 6, and a work station which is an arithmetic control unit for controlling the other measuring instruments. In addition, the power meter 50 is a storage element 11 that stores a correction coefficient of a correction function, and an ASIC (Application) that performs analog / digital conversion of an input signal and performs calculation to control display or output.
specific integrated circuit: hereinafter referred to as ASIC circuit). 13 is a memory element 11
It is a writer for writing the correction coefficient of the correction function to. Here, since the workstation 10 does not perform much arithmetic processing, a slow workstation is sufficient.

The power meter 50 has an A
It has a / D converter, a microprocessor, and the like. In the normal operation, after the voltage and current that have been taken in are A / D converted, they are corrected by the correction coefficient of the correction function stored in the storage element 11, the power is calculated, and the result is output.

The operation of FIG. 1 will be described with reference to the flowchart of FIG. As a step, the power meter 50 is brought into a normal operation state. Workstation 7 as a step
Applies a sine wave to the current and voltage input terminals of power meter 50. As a step, the frequency is changed by the signal source 6, and the phase shifter 7 changes the phase of the sine wave applied to the current input terminal with respect to the sine wave applied to the voltage input terminal of the power meter 50. As a step, the voltmeter 8 measures the power value calculation output signal 100 of the power meter 50 in this state. As a step, the phase difference for each of the two frequencies is "-90 °", "0 °", "+90".
Check if the measurement of the single-phase power output of ° ”has been completed. If not completed, repeat steps and steps. 2 from 6 types of data measured as steps
Find the phase error at different frequencies. As a step, a correction coefficient is calculated from two types of frequencies and a phase error at the frequency, and the coefficient of the calculated correction function is written in the storage element 11 of the power meter 50 by the writer 13.

Further, this correction function will be described with reference to the characteristic curve diagrams of FIGS. FIG. 3 is a characteristic curve diagram showing a time change of voltage or current. "A" in Figure 3
Is a voltage or current waveform actually taken in, and "b" is a voltage or current waveform when there is no phase error between the voltage input and the current input. In FIG. 3, “D” is a phase error “ΔΦ” between the voltage input and the current input, and “C” is the ASIC circuit 1.
Equivalent to the phase of one sampling cycle of A / D converter in 2 "
Φ _sampling ”.

Since the single-phase power is affected by the phase error "ΔΦ" between the voltage input and the current input, the phase of the voltage input is corrected to match the phase of the current input, or the The phase error “ΔΦ” may be set to zero by correcting the phase and matching it with the phase of the voltage input. That is, the nth sampling data of the voltage input or the current input is “S (n)”, and the immediately preceding data, that is, the (n−1) th sampling data is “S (n−).
1) ”, the corrected nth sampling
The data "S _comp (n)" is obtained by linear interpolation as follows. S _comp (n) = S (n)-[{S (n) -S (n-1)} / Φ _sampling ] ・ ΔΦ = ΔΦ / Φ _sampling・ S (n-1) + (1-ΔΦ / Φ _sampling ) ・ S (n) (1)

Further, the phase error "ΔΦ" is obtained from the single phase power output of the phase difference "-90 °", "0 °" and "+ 90 °" by the phase shifter 7. FIG. 4 is a characteristic curve diagram showing the relationship between the phase difference by the phase shifter 7 and the single-phase power. In FIG. 4, “A” is the characteristic when the phase error is “0”, and “B” is the characteristic when there is the phase error “ΔΦ” shown in “C”. Here, “d”, “e”, and “f” in FIG. 4 are single-phase power outputs when the phase difference by the phase shifter 7 is “−90 °”, “0 °”, and “+ 90 °”, respectively. It is "P".

When the phase difference due to the phase shifter 7 is "Φ" and the voltage input value and the current input value are "V ₀ " and "I ₀ ", respectively, the single-phase power output "P (Φ)" is as follows. It is represented by a formula. P (Φ) = phase difference due to _{(V 0 · I 0/2} ) cos (Φ + ΔΦ) (2) phase shifter 7 "-90 °", "0 °" and "
Since a + 90 ° ", the formula (2) is, P (-90 °) = ( V 0 · I 0/2) cos (-90 ° + ΔΦ) = - (V 0 · I 0/2) sinΔΦ (3 ) P (0 °) = ( V 0 · I 0/2) cos (0 ° + ΔΦ) = (V 0 · I 0/2) cos (ΔΦ) (4) P (90 °) = (V 0 · I _{0/2) cos (90 °} + ΔΦ) = become _{(V 0 · I 0/2} ) sinΔΦ (5).

From equations (3) to (5), the phase error "ΔΦ"
Can be obtained by ΔΦ = tan ⁻¹ {−P (−90 °) / P (0 °)} = tan ⁻¹ {P (90 °) / P (0 °)} (6). However, since the phase error “ΔΦ” is a function of the frequency of the input waveform as described above,
ΔΦ / Φ _sampling is “δ”, and this “δ” is a linear expression of the frequency as follows: δ = Gf + H (7) where “G” and “H” are correction coefficients and “f” "Is the frequency of the input waveform.

Therefore, the two types of frequencies "f ₁ " and "f
_{For 2} ", two kinds of phase error" Δ
Φ ₁ ″, “ΔΦ ₂ ”, that is, “δ ₁ ”, “δ ₂ ”, are obtained, and the following simultaneous equations are obtained by substituting into equation (7): δ ₁ = Gf ₁ + H δ ₂ = By solving Gf ₂ + H, the correction coefficients “G” and “H” are obtained as follows: G = (δ ₂ −δ ₁ ) / (f ₂ −f ₁ ) H = (f ₂ · δ ₁ − f ₁ δ ₂ ) / (f ₂ −f ₁ )

FIGS. 5 (A) and 5 (B) are characteristic curve diagrams showing the simulation results of the power meter adjusted by the power meter adjusting device described above. FIG. 5A shows 50 to 60 Hz.
In the range of (B), the correction coefficient is calculated in the range of 40 to 70 Hz, and the phase difference between the voltage input and the current input is “Φ = + 90 °” with the single-phase power meter with the phase error “ΔΦ ≦ 0.36 °”.
The reading error of the single-phase power meter in the case of is shown. However, in FIG. 5, “a” and “c” indicate the case where no correction is performed, and “b” and “d” indicate the case where correction is performed, respectively. Here, in FIG. 5A, the read error is improved to about 1/1000 in the range of 50 to 60 Hz, and in FIG. 5B, the read error is improved to about 1/4 in the range of 40 to 70 Hz.

As a result, the low-distortion sine wave generator and interface used in the conventional adjustment method are no longer required, and the data to be captured becomes 6 types, and only "tan ^-1 " and several arithmetic operations are required. Therefore, the acquisition time and the calculation time are also shortened. In addition, the adjustment system can be easily constructed when readjustment is performed on a production line or a customer where it is difficult to use a low-distortion sine wave generator or a high-speed workstation, which are generally expensive.

In equation (6), the phase error "ΔΦ"
(6) when the calculation accuracy is not required when calculating
If one of the two values is required, the average value of both values is used. In addition, the phase difference due to the phase shifter 7 is "-90.
“”, “0 °” and “+ 90 °”, not the phase difference
It may be 0 ° "," + 90 ° "," + 180 ° ", or the like.

Further, in the case of performing the non-linearity correction together with the phase error correction, the power meter adjusting apparatus according to the present invention is combined with the power meter adjusting method according to Japanese Patent Application No. 4-51411. Can be realized.

[0022]

As is apparent from the above description,
The present invention has the following effects. The number of measuring devices such as low distortion sine wave generators as in the conventional example is reduced by obtaining the correction coefficient of the phase error correction function by using only the measurement outputs of three points with different phase differences for two kinds of frequencies. As a result, it is possible to realize a power meter adjustment device that does not require data acquisition processing and has a short time for adjusting the power meter.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of an electric power meter adjusting device according to the present invention.

FIG. 2 is a flowchart illustrating the operation of the device of FIG.

FIG. 3 is a characteristic curve diagram showing a time change of voltage or current.

FIG. 4 is a characteristic curve diagram showing a relationship between a phase difference and single-phase power.

5 is a characteristic curve diagram showing a simulation result of the power meter adjusted in the example of FIG.

FIG. 6 is a configuration block diagram showing an example of a conventional power meter.

[Explanation of symbols]

 1a, 1b Transformer 2 Analog operation circuit 3a, 3b Display means 4a, 4b A / D converter 5 Digital operation device 6 Signal source 7 Phase shifter 8 Voltmeter 9 Power supply 10 Workstation 11 Memory element 12 ASIC circuit 13 Writer 50 Power meter 100 Power value calculation output signal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Fujino 2-9-32 Nakamachi 2-chome, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

[Claims] 1. A power meter adjusting device for correcting a phase error of a meter by a correction function stored in a storage element of the power meter, comprising: a power supply for supplying a power supply voltage to the power meter; and the power meter. A signal source for applying a sine wave signal having an arbitrary input frequency to the voltage input terminal of the power source, a phase shifter for shifting the phase of the sine wave signal of the signal source and applying the current input terminal of the power meter, and the power Voltmeter that measures the power value calculation output of the power meter, a writer that writes the correction coefficient in the storage element of the power meter, and a sine wave signal having two input frequencies by controlling the signal source. Applied to a measuring instrument and controlling the phase shifter to shift the phase difference between the voltage input and the current input by 90 ° for each of the sine wave signals of the two types of input frequencies, and sequentially output the three types of sine wave signals. Apply to the power meter, before The power value calculation output including the phase error characteristic of the power meter at each input measured by the voltmeter is taken in, and the phase error between the voltage input and the current input is calculated from this power value calculation output. An operation of calculating a correction coefficient of a correction function, which is a linear expression of the input frequency, from the input frequency of each type, and controlling the writer to store the calculated correction coefficient of the correction function in a storage element of the power meter. An electric power meter adjusting device, comprising: a control means.