KR101029016B1 - Power meter having error calibration function and method for calibrating phase error - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power meter for measuring power by receiving a voltage signal and a current signal, and more particularly, to a power meter and a phase error correction method having a function of correcting a phase error occurring in a power measurement process.

The power meter 3 according to the present invention comprises: a preprocessor 32 for preprocessing at least a voltage signal and a current signal; A nonvolatile memory 37 for receiving and storing correction data for correcting a phase error between the voltage signal and the current signal preprocessed by the preprocessor 32; An A / D converter (34) for sampling the voltage signal and the current signal preprocessed by the preprocessor (32) at independent points of time and converting them into digital signals to output voltage and current values; A voltage is output from the A / D converter 34 by outputting a sampling control signal for the sampling in the A / D converter 34 based on the correction data stored in the nonvolatile memory 37. And calculating a mean power by multiplying and accumulating a value and a current value, wherein the multiplicative degree is performed based on the correction data stored in the nonvolatile memory 37.

The time points of the sampling performed at independent time points for the voltage signal and the current signal may be different from each other by the correction time tc1, which is the remainder obtained by dividing the total correction time tc by the sampling period Ts. Is characterized in that the total correction time tc is multiplied by the index offset Nos which is the quotient obtained by dividing by the sampling period Ts.

Power Meter, Phase Difference, Error Angle, High Speed Sampling, Calibration, Calibration

Description

POWER METER HAVING ERROR CALIBRATION FUNCTION AND METHOD FOR CALIBRATING PHASE ERROR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power meter for measuring power by receiving a voltage signal and a current signal, and more particularly, to a power meter and a phase error correction method having a function of correcting a phase error occurring in a power measurement process.

In addition, the present invention relates to a power meter and a phase error correction method that is easy to correct phase error even for a power meter that performs high-speed sampling.

In general, the power measurement method senses the voltage and current flowing through the power device and inputs it to the power meter, and the power meter preprocesses it and converts it in the analog-to-digital converter. The average power is calculated by finding the average per cycle.

In the process of sensing voltage and current, PT (Current Transformer) and CT (Current Transformer) are used to convert the actual high voltage and current into signal voltage and signal current. have.

In addition, the signal voltage and signal current input to the power meter inevitably go through additional analog circuits in order to be provided to the input terminal of the analog-to-digital converter (pre-processing process). The phase delay difference, i.e., the phase error, is generated.

This phase error between voltage and current causes an error in the actual calculated power. If the phase delays of voltage and current occur equally, since the phase error is zero, the error of the power value calculated by ADC sampling the voltage signal and the current signal becomes zero.

As such, when the voltage and the current have the same phase delay characteristics, an error of the power value does not occur, but when the phase delay characteristics between the voltage and the current have a difference, an error is caused.

1 is a graph illustrating the phase error between voltage and current.

a denotes a reference voltage, b denotes a reference current, and c denotes a delay current. {In FIG. 1, only the relative difference between voltage and current in phase delay is reflected in the current, and only the delay current is plotted on the graph.}

The actual sample values obtained through the analog-to-digital converter (A / D converter) are obtained only with the reference voltage of a and the delay current values of c.

Therefore, there is a problem that an error occurs in the average power calculated by the power meter due to the difference (phase error) of the phase delay of the voltage signal and the current signal.

An object of the present invention for solving the problem of the background technology, a power meter and a phase error correction method capable of correcting the phase error caused by the difference in the phase delay generated during the sensing and pre-processing of the voltage signal and the current signal In providing.

In addition, another object of the present invention is to provide a power meter and a phase error correction method that enables accurate error correction even when the phase error of the voltage and current signals out of the sampling period due to high speed sampling.

According to an aspect of the present invention, a power meter includes a preprocessor 32 for preprocessing at least a voltage signal and a current signal; A nonvolatile memory 37 for receiving and storing correction data for correcting a phase error between the voltage signal and the current signal preprocessed by the preprocessor 32; An A / D converter (34) for sampling the voltage signal and the current signal preprocessed by the preprocessor (32) at independent points of time and converting them into digital signals to output voltage and current values; A voltage is output from the A / D converter 34 by outputting a sampling control signal for the sampling in the A / D converter 34 based on the correction data stored in the nonvolatile memory 37. And calculating a mean power by multiplying and accumulating a value and a current value, wherein the multiplicative degree is performed based on the correction data stored in the nonvolatile memory 37.

The time points of the sampling performed at independent time points for the voltage signal and the current signal may be different from each other by the correction time tc1, which is the remainder obtained by dividing the total correction time tc by the sampling period Ts. Is characterized in that the total correction time tc is multiplied by the index offset Nos which is the quotient obtained by dividing by the sampling period Ts.

A phase error correction method of a power meter according to an aspect of the present invention, the pre-processing unit 32 for pre-processing the voltage signal and the current signal, and the voltage signal and current signal pre-processed by the pre-processing unit 32 A / D In the method for correcting the phase error in the power meter (3) including the A / D conversion unit 34 to convert, the pre-processing unit 32 samples the voltage signal and the current signal, the phase error A first step of sampling the sampling time points for the voltage signal and the current signal different from each other by the correction time tc which is the remainder obtained by dividing the total correction time tc for correcting by the sampling period Ts; A second step of converting the voltage signal and the current signal sampled in the first step into a digital signal to obtain a voltage value and a current value of the digital signal; Multiply the voltage value and the current value and accumulate and average the result of the multiplication to obtain an average power, wherein the multiplication is performed by an index offset Nos which is a quotient obtained by dividing the total correction time tc by a sampling period Ts. And a third step of multiplying by misalignment.

The present invention has the effect of correcting the phase error generated during the sensing and pre-processing of the voltage signal and the current signal.

In addition, the present invention has an effect that can accurately correct the phase error even when the phase error of the voltage and current signals out of the sampling period due to the high-speed sampling.

In addition, the present invention has an effect that can easily correct a wide range of phase error even in a power meter that performs a high-speed sampling.

<First Embodiment>

FIG. 2 is a graph showing an ADC sampling point on a waveform by enlarging the 'A' portion of FIG. 1.

Referring to FIG. 2, when the voltage (a) and the current (c) are sampled at the same time, samples of the symbol Δ and symbol * are selected, and an error occurs when power is calculated using the samples. Therefore, if the sampling time of voltage is different from the sampling time of current, samples of symbols △ and ○ are obtained, A / D conversion to these samples, and the power is calculated to obtain accurate power.

As such, when the sampling time is corrected and sampled by a time corresponding to a phase error of voltage and current, a value for an accurate sample (symbol □) of the original current signal can be obtained. {Although the diagrams of FIGS. 1 and 2 show that there is no delay in the voltage signal, there may be a delay in the actual voltage signal, and only the delay is shown for convenience of description.

Although there may be a phase delay in the voltage signal and the current signal, respectively, the phase error can be corrected by adjusting the sampling time point for one signal only by the difference (ie, the phase error). In addition, the adjustment of the sampling time point may be delay correction or enhancement correction.

3 is a sampling timing diagram for a case where there is no phase error between voltage and current, and FIG. 4 is a sampling timing diagram for correcting a phase error when a current is delayed more than the voltage. FIG. Sampling timing diagram for correcting phase error in case of further delay.

6 is a diagram illustrating a power meter, a voltage-current generator, and a control PC having an error correction function according to one embodiment of the present invention.

For example, a process of setting the power meter 3 before it is produced and shipped or before the user uses the power meter 3 is required.

In the above process, a voltage-current generator 1 and a control PC 2 are required separately from the power meter 3. However, when the power measuring device 3 has the functions of the voltage-current generator 1 and the control PC 2, they may be omitted separately.

 The voltage-current generator 1 generates a reference voltage and a reference current according to the control signal of the control PC 2 and applies it to the power meter 3.

The control PC 2 outputs a control signal to the voltage-current generator 1 to generate a reference voltage and a reference current, and calculates an average power from the information about the reference voltage and the reference current generated. In addition, the control PC 2 receives the value of the average power measured by the power meter 2, compares the calculated average power with the measured average power, calculates correction data, and outputs the correction data to the power meter 3. The correction data is data used by the power meter 3 to correct the phase error.

The power meter 3 includes a mode recognizer 31, a preprocessor 32, an A / D converter 34, an operation controller 35, a data input / output unit 36, a nonvolatile memory 37, and a display unit ( 38).

Here, the mode recognizing unit 31 receives the input from the user or recognizes whether the mode of the power meter is the test mode or the normal mode and provides the information to the operation control unit 35. The test mode is a mode in which the power meter 3 operates in a state in which the phase error is not corrected, and is a mode for calculating and setting the correction data to the power meter 3. The normal mode is a mode in which the power meter 3 operates in a state of correcting a phase error.

The preprocessor 32 performs preprocessing on the input voltage signal and current signal. In the test mode, the preprocessor 32 will receive the reference voltage signal and the reference current signal from the voltage-current generator 1 as shown in FIG. 6, and in the normal mode, the voltage signal and current sensed by the load to be measured in practice. The signal will be input to the preprocessor 32. {The voltage-current generator 1 and the control PC 2 may be connected as shown in FIG. 6 to check whether the power meter 3 actually operates correctly even in the normal mode.}

 On the other hand, considering the PT (Current Transformer) and CT (Current Transformer) used to sense the voltage signal and the current signal in the actual load, the voltage-current generator 1 is to give a phase error between the voltage signal and the current signal Can be. The preprocessing unit 32 may include a noise filter, and removes noise of a signal converted through PT (Potential Transformer) and CT (Current Transformer) using the noise filter. Since PT (Current Transformer), CT (Current Transformer), and noise filter are well known to those skilled in the art, detailed description thereof will be omitted.

The A / D converter 34 samples the voltage signal and the current signal input from the preprocessor 32 according to a control signal of the operation controller 35 at appropriate intervals, converts the signal into a digital signal, and outputs a voltage value and a current value. .

The operation control unit 35 outputs a control signal to the A / D converter 34 and multiplies and accumulates the voltage value and the current value input from the A / D converter 34 to calculate the average power. The operation control unit 35 controls the sampling period and the sampling time point of the A / D converter 34, and outputs a sampling control signal for this purpose.

In the test mode, the operation control unit 35 controls the A / D converter 34 so that sampling is performed at the same time with respect to the voltage signal and the current signal (see FIG. 3). On the other hand, in the normal mode, the operation control unit 35 adjusts the sampling time point for the voltage signal and the current signal in consideration of the correction time for the phase error in controlling the sampling time point of the voltage signal and the current signal (FIG. 4 and 5). In the normal mode, the operation control unit 35 controls the sampling timing of the voltage signal and the current signal based on the correction data stored in the nonvolatile memory 37. Sampling is performed at independent time points for the voltage signal and the current signal. Here, the correction data is expressed as a value reflecting the correction time tc, as shown in FIG. For example, the correction time tc is positive when the ground current correction is performed based on the voltage signal, and the correction time tc is negative when the phase correction is performed. In the normal mode, the operation control unit 35 controls the A / D converter 34 to relatively delay or advance the sampling point of the voltage signal or the current signal by the correction time tc.

The nonvolatile memory 37 stores a program necessary for the operation of the power meter 37, and particularly stores the correction data for controlling the sampling time of the A / D converter 34. This correction data is received from the control PC 2 and stored.

The data input / output unit 36 functions as a data input / output function between the power meter 3 and an external device. In particular, the data input / output unit 36 outputs the measured average power to the control PC 2 and receives a correction data from the control PC 2. To perform.

The display unit 38 displays various values and state information measured by the power meter 3, and in particular, displays the measured average power.

7 is a diagram illustrating a process of calculating correction data for correcting a phase error of a power meter in a test mode according to an exemplary embodiment of the present invention.

First, the control PC 2 instructs the voltage-current generator 1 to generate a reference voltage and a reference current (S1). At this time, the control PC 2 may also set the magnitude, phase difference, cycle, and the like of the reference voltage and the reference current. In the step S10, the control PC 2 may operate the voltage-current generator 1 manually by a human being. Accordingly, the voltage-current generator 1 generates the set reference voltage and reference current (S21), and the generated reference voltage and reference current will be input to the power meter 3 (not shown).

The control PC 11 sets the power meter 3 to the test mode and commands power measurement (S11). The mode setting and power measurement command in step S11 may be manually operated by a human being without the control PC 2 performing. Accordingly, the power meter 3 performs power measurement (S20).

{It does not matter even if the posterior relationship between the above step S10 and step S11 is changed or simultaneous. It is also possible that the relationship between the steps S20 and S21 is changed or coincidental.

In step S20, the power meter 3 performs power measurement. The power measurement includes the following operations. The preprocessor 32 of the power meter 3 performs preprocessing, and the A / D converter 34 performs A / D conversion to provide A / D converted voltage values and current values. The operation control unit 35 controls the A / D converter 34 and calculates an average power from digital voltage values and current values output from the A / D converter 34. The average power can be calculated by multiplying the voltage and current values and accumulating them over a predetermined cycle. On the other hand, the calculation control unit 35 outputs a sampling control signal to the A / D conversion unit 34 for power measurement.

In the test mode, the operation control unit 35 outputs a sampling control signal without error correction. Even if there is a phase error between the voltage signal and the current signal, the sampling control signal is output so that the voltage signal and the current signal can be sampled at the same time as shown in FIG. 3 without correction.

In step S30, the power meter 3 provides the value of the measured average power to the control PC 2.

And since the control PC 2 knows the information about the voltage and the current which generate | occur | produced in the voltage-current generator 1, it can calculate average power from this. Therefore, the control PC 2 can calculate the phase error between the voltage and current signals by comparing the calculated average power with the average power provided from the power meter 3. The control PC 2 calculates correction data from the calculated phase error (S40).

The control PC 2 transmits the calculated correction data to the power meter 3 (S50), so that it can be stored in the nonvolatile memory 37 of the power meter 3.

On the other hand, the normal mode is a mode in which the power meter 3 corrects the phase error to accurately measure the actual average power so that the power meter 3 operates normally. It is also a mode that operates for the user where the actual power meter 1 is used. {In addition, it is possible to check whether the calculated power value and the measured power value are the same by connecting with the control PC 2 and the voltage-current generator 1 in the normal mode before shipment of the product.}

In any case, in the normal mode, the power meter 3 A / D converts the voltage signal and the current signal while correcting the phase error based on the correction data stored in the nonvolatile memory 37.

및

와 같은 신호일 수 있다). 그러나, 이러한 신호에 한정되는 것은 아니며, 예를 들면, 샘플링 시점을 표현하는 디지털 데이터 형태이어도 상관없다.In particular, in the normal mode, the operation control unit 35 outputs a sampling control signal for correcting the phase error based on the correction data stored in the nonvolatile memory 37. As shown in FIG. 4 or FIG. 5, a sampling control signal obtained by adjusting a sampling time point for a voltage signal and a current signal is output. The sampling control signal exists separately with respect to the voltage and the current, and may be, for example, a signal having a falling edge at each sampling time point (that is, a start time of holding).

And

It may be a signal such as). However, the present invention is not limited to such a signal and may be, for example, a digital data type representing a sampling time point.

&Lt; Embodiment 2 >

8 is a diagram illustrating an example of a timing diagram in the A / D converter 34.

은 전압을 위한 샘플링 제어 신호를 나타내고

는 전류를 위한 샘플링 제어 신호를 나타낸다. 시점 T1에 전압 신호를 샘플한다음 홀드하며, 시점 T2에 전류 신호를 샘플한 다음 홀드한다. 따라서 시점 T1과 시점 T2 사이의 시간차가 위상 오차를 보정하기 위한 보정시간이다.CLK is a clock signal,

Represents the sampling control signal for voltage

Denotes a sampling control signal for the current. The voltage signal is sampled and held at the time point T1, and the current signal is sampled and then held at the time point T2. Therefore, the time difference between the time point T1 and the time point T2 is a correction time for correcting the phase error.

D15-D0 represents digital data after A / D conversion, DATA1 is for voltage, and DATA2 is for current.

The A / D converter 34 may be implemented as a general multi-channel ADC chip, and has a port for outputting A / D converted data. In the case of multi-channel, data of each channel is generally outputted continuously using the same port. That is, the A / D converted voltage value DATA1 and the current value DATA2 are output with a time difference using the same port.

및

의 active영역(0V인 부분)도 각 샘플링 주기마다 있어야, 샘플링 주기마다 전압 및 전류를 각각 샘플링하여 A/D변환할수 있다. 따라서 전압과 전류의 샘플링 시간 차이를 샘플링 주기보다 크게 하는 것은 생각하기 어렵다. 즉, 위상 오차에 대한 보정 시간을 샘플링 주기이상으로 부여하는 것은 어렵다고 생각하는 것이 통상적이었다. 그러나 본 발명의 제 2 실시 예에 따른 발명은 그 틀을 벗어나고자 하였다.As shown in FIG. 8, the voltage and current signals should be sampled at each sampling period. And sampling control signal

And

The active area of (0V part) must also exist in each sampling period, and A / D conversion can be performed by sampling voltage and current for each sampling period. Therefore, it is hard to think that the difference between the sampling time of voltage and current is larger than the sampling period. That is, it was common to think that it is difficult to give the correction time for phase error more than a sampling period. However, the invention according to the second embodiment of the present invention intends to depart from the framework.

Also in the second embodiment of the present invention, the structure of the power meter 3 is the same as that of the power meter 3 according to the first embodiment (see Fig. 6). However, the correction method for the content and phase error of the correction data and the power calculation method are different from those in the first embodiment.

9 is a diagram schematically showing a sampling time according to the second embodiment of the present invention.

The total correction time tc required is outside the sampling period Ts. However, for each sampling period Ts, the A / D converter 34 samples both voltage and current signals. The correction time tc1 in each sampling period Ts is calculated as follows.

The total correction time tc required is divided by the sampling period Ts, and the quotient is the index offset Nos value, and the remainder is the correction time tc1.

That is, the total correction time (tc) = [index offset (Nos) * sampling period (Ts)] + correction time (tc1). For example, the correction time tc1 is represented by a positive value of zero or more and smaller than Ts. The index offset Nos value is 0 or a positive value in the case of ground correction, and a negative value in the case of fastening correction.

In the normal mode, the operation control unit 35 outputs a sampling control signal to sample the voltage signal and the current signal for each sampling period Ts, but delay the other one by a correction time tc1 for the predetermined one.

On the other hand, in the normal mode according to the second embodiment of the present invention, the method of calculating the average power is different from that of the first embodiment.

The average power is calculated using the voltage value and the current value, but is calculated by referring to the above-described index offset value.

10 is a schematic diagram of multiplying a voltage value and a current value according to the second embodiment of the present invention.

In FIG. 10, each column of the upper portion represents a register or a memory in which voltage values are sequentially stored, and each column of the lower portion represents a resistor or memory in which current values are sequentially stored. For example, V [0] and I [0] represent voltage values and current values sampled in the first sampling period, and the voltage values and current values will already be sampled to reflect the correction time t _c1 .

As shown in the figure, when the index offset value is 2, multiplication is performed by shifting the voltage and the current by two sections.

On the other hand, correction data is stored in the nonvolatile memory 37. The correction data may be data relating to the total correction time tc or data related to the index offset Nos value and the correction time tc1. The correction data is received by the power meter 3 and stored in the control PC 2.

The control PC outputs only the total correction time tc as the correction data, or in the total correction time tc, [total correction time (tc) = index offset (Nos) * sampling period (Ts) + correction time (tc1)] The index offset Nos and the correction time tc1 may be calculated and output using a formula.

The calculated correction data is then output to the data input / output unit 36 of the power meter 3, and the data input / output unit 36 receives the correction data. Subsequently, the input correction data is stored in the nonvolatile memory 37 (S18) and the test mode ends. At this time, when only the total correction time tc is input from the control PC 2, the arithmetic control unit 35 selects [total correction time tc = [index offset Nos] * sampling period from the total correction time tc. Ts)] + correction time (tc1)] to calculate the index offset Nos and the correction time tc1 and store it in the nonvolatile memory 37, or the actual index offset Nos and the correction time ( tc1) may be calculated when necessary.

According to the second embodiment of the present invention, the process of calculating correction data for correcting the phase error of the power meter in the test mode is almost similar to that of the first embodiment. However, after the total correction time tc is calculated, it is different from that for calculating the index offset Nos and the correction time tc1.

In high-speed sampling with a large number of sampling, since the sampling period is short, when the phase error of voltage and current is larger than the sampling period, the invention according to the first embodiment has a limitation in correcting this.

However, the invention according to the second embodiment automatically calculates and uses the index offset and correction time for a wide range of phase errors of voltage and current from the required total correction time even when the sampling period Ts is short due to high speed sampling. Therefore, in the high-speed sampling, the total correction time can be significantly extended, and thus the power measurement accuracy can be improved.

1 is a graph illustrating the phase error between voltage and current.

FIG. 2 is a graph showing an ADC sampling point on a waveform by enlarging the 'A' portion of FIG. 1.

3 is a sampling timing for the case where there is no phase error between voltage and current.

4 is a sampling timing diagram for correcting a phase error when a current is further delayed compared to a voltage.

5 is a sampling timing diagram for correcting a phase error when a voltage is further delayed compared to a current.

6 is a diagram illustrating a power meter, a voltage-current generator, and a control PC having an error correction function according to one embodiment of the present invention.

7 is a diagram illustrating a process of calculating correction data for correcting a phase error of a power meter in a test mode according to an exemplary embodiment of the present invention.

8 is a diagram illustrating an example of a timing diagram in the A / D converter 34.

9 is a diagram schematically showing a sampling time according to the second embodiment of the present invention.

10 is a schematic diagram of multiplying a voltage value and a current value according to the second embodiment of the present invention.

Description of the Related Art [0002]

1: voltage-current generator

2: control PC

3: power meter

31: mode recognition unit

32: voltage-current preprocessor

33: sample holder

34: A / D converter

35: operation control unit

36: data input / output unit

37: nonvolatile memory

38: display unit

Claims (6)

delete A preprocessor 32 for preprocessing at least a voltage signal and a current signal; An A / D converter 34 for sampling the voltage signal and the current signal preprocessed by the preprocessor 32 and converting the voltage signal and the current signal into digital signals to output voltage and current values; A nonvolatile memory (37) for receiving and storing correction data for correcting a phase error of a voltage signal and a current signal when the A / D converter 34 performs the sampling; A voltage is output from the A / D converter 34 by outputting a sampling control signal for the sampling in the A / D converter 34 based on the correction data stored in the nonvolatile memory 37. And a calculation control unit for calculating an average power by multiplying and accumulating the value and the current value. Has a test mode and a normal mode, And the correction data is calculated in the test mode. A preprocessor 32 for preprocessing at least a voltage signal and a current signal; A nonvolatile memory 37 for receiving and storing correction data for correcting a phase error between the voltage signal and the current signal preprocessed by the preprocessor 32; An A / D converter (34) for sampling the voltage signal and the current signal preprocessed by the preprocessor (32) at independent points of time and converting them into digital signals to output voltage and current values; A voltage is output from the A / D converter 34 by outputting a sampling control signal for the sampling in the A / D converter 34 based on the correction data stored in the nonvolatile memory 37. And calculating a mean power by multiplying and accumulating a value and a current value, wherein the multiplicative degree is performed based on the correction data stored in the nonvolatile memory 37. The timings of the sampling performed at independent time points for the voltage signal and the current signal are different from each other by the correction time tc1 which is the remainder obtained by dividing the total correction time tc by the sampling period Ts. The multiplication operation is a power meter having an error correction function, characterized in that the multiplication by multiplying by the offset offset (Nos) that is the quotient of the total correction time (tc) divided by the sampling period (Ts). The method of claim 3, The correction data is, Derived by comparing the average power measured from the reference voltage and the reference current with the measured average power without correcting the phase error between the voltage signal and the current signal in a state where the power meter receives a reference voltage and a reference current from the outside Power meter having an error correction function, characterized in that. A power meter including a preprocessor 32 for preprocessing a voltage signal and a current signal, and an A / D converter 34 for A / D converting a preprocessed voltage signal and a current signal; In the method for correcting the phase error in 3), The voltage signal and the current signal pre-processed by the preprocessor 32 are sampled, and the voltage signal is equal to the remaining time obtained by dividing the total correction time tc for correcting the phase error by the sampling period Ts. And a first step of sampling the time points of the sampling with respect to the current signal different from each other; A second step of converting the voltage signal and the current signal sampled in the first step into a digital signal to obtain a voltage value and a current value of the digital signal;  Multiply the voltage value and the current value and accumulate and average the result of the multiplication to obtain an average power, wherein the multiplication is performed by an index offset Nos which is a quotient obtained by dividing the total correction time tc by a sampling period Ts. A third step of mismatching multiplication;  Phase error correction method of a power meter comprising a. The method according to claim 5, The total correction time (tc), In the state where the power meter receives the reference voltage and the reference current from the outside, the average power measured without comparing the phase error between the voltage signal and the current signal is compared with the average power calculated from the reference voltage and the reference current. Phase error correction method of the power meter, characterized in that derived.

Images