JP2008032465A - Electrical power measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical power measurement apparatus which can reduce an arithmetic error which occurs at a multiplier and is not directly proportional to an input signal or an output signal. <P>SOLUTION: The output signal of a correction signal generation section 108 which generates a correction signal in accordance with the input signal is added to the output signal of the multiplier 107 by an adder 110, thereby reducing the arithmetic error occurring in the multiplier 107. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power measuring apparatus that measures power from an alternating voltage and alternating current of a system to be measured.

2. Description of the Related Art Conventionally, power measuring devices that detect external voltage and current and measure power have been widely used. The power measuring apparatus includes a multiplication unit that multiplies a signal that is directly proportional to the voltage and current of the system under measurement, and a correction unit that corrects an error generated by the multiplication. (For example, Patent Document 1)
Japanese Patent Laid-Open No. 04-310868 (page 6, FIG. 1)

As described above, a power measuring apparatus including a multiplying unit that multiplies a signal that is directly proportional to the voltage and current of the system to be measured and a correcting unit that corrects an error caused by the multiplication is widespread. In the conventional power measuring apparatus, the error correction unit can correct a linear error that is directly proportional to the output signal of the multiplication unit. However, the multiplication unit may have a non-linear error that is not directly proportional to the output signal or the input signal. For example, in a circuit used in a multiplication unit called a Gilbert cell, it is known that an operation error that is directly proportional to the square of an input signal occurs. In such a case, there has been a problem that the calculation error generated in the multiplication unit cannot be effectively reduced by performing correction only by multiplying the output signal of the multiplication unit by a certain coefficient.

  In view of the above problems, an object of the present invention is to provide a power measuring apparatus capable of reducing a calculation error that is not directly proportional to an input signal or an output signal generated in a multiplication unit.

In order to achieve the above object, a power measuring apparatus according to the present invention includes a first variable voltage generating means for generating a reference signal, a signal directly proportional to the current of the system under test, and the first variable voltage generating means. A first signal selecting means for selecting one of the signals generated by the above, a second variable voltage generating means for generating a reference signal, a signal directly proportional to the voltage of the system under test, the second Second signal selecting means for selecting one of the signals generated by the variable voltage generating means, a signal directly proportional to the current of the system under test selected by the first signal selecting means, and the second A signal directly proportional to the voltage of the system under measurement selected by the signal selection means, or a signal generated by the first variable voltage generation means selected by the first signal selection means and the second signal By means of selection Multiplication means for multiplying the selected signal generated by the second variable voltage generation means, and the first variable voltage generation selected by the first signal selection means multiplied by the multiplication means. Error detecting means for detecting an error of a signal representing a product of the signal generated by the means and the signal generated by the second variable voltage generating means selected by the second signal selecting means; and the error detecting means Correction signal generating means for converting a signal detected by the above-mentioned signal and a signal directly proportional to the current of the system under measurement selected by the first signal selection means into a correction signal; and the first multiplied by the multiplication means. A signal representing the product of a signal directly proportional to the current of the measured system selected by the signal selecting means and a voltage directly proportional to the voltage of the measured system selected by the second signal selecting means; And characterized by including an addition means for adding the correction signal converted by the signal generating means.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power measurement apparatus which can reduce the calculation error which is not directly proportional to the input signal or output signal which generate | occur | produces in a multiplication part can be provided.

  Examples of the present invention will be described below.

  Embodiment 1 of a power measuring apparatus according to the present invention will be described with reference to FIG.

  In FIG. 1, reference numeral 100 denotes a power measuring device main body. In this embodiment, a single-phase two-wire power measuring device is used.

Reference numeral 101 denotes a terminal portion which is made of a conductive metal such as copper, and receives a voltage directly proportional to the alternating current of the system under test from the outside.

Reference numeral 102 denotes a terminal portion which is made of a conductive metal such as copper, and receives a voltage directly proportional to the AC voltage of the system under test from the outside.

Reference numeral 103 denotes a first variable voltage generator, which is composed of an analog-digital converter or the like and generates a reference voltage.

Reference numeral 104 denotes a second variable voltage generator, which includes an analog-digital converter or the like, and generates a reference voltage.

A first signal selection unit 105 includes an analog switch or the like, and is generated by the voltage directly proportional to the alternating current of the system under test input to the terminal unit 101 or generated by the first variable voltage generation unit 103. Select and output a reference voltage.

Reference numeral 106 denotes a second signal selection unit configured by an analog switch or the like. The second signal selection unit 106 generates a voltage directly proportional to the AC voltage of the measured system input to the terminal unit 102 or the second variable voltage generation unit 104. Select and output a reference voltage.

A multiplication unit 107 includes an analog multiplication circuit made of a semiconductor such as a transistor, and multiplies signals output from the signal selection unit 105 and the signal selection unit 106. As the analog multiplication circuit, a circuit called a Gilbert cell has recently become widespread.

Reference numeral 108 denotes a first correction signal generator, which includes a function generation circuit made of a semiconductor such as a transistor, and converts the signal output from the first signal selection unit 105 into a voltage for error reduction and outputs it.

Reference numeral 109 denotes a second correction signal generation unit, which includes a function generation circuit made of a semiconductor such as a transistor, and converts a signal output from the second signal selection unit 106 into a voltage for error reduction and outputs the voltage.

Reference numeral 110 denotes an adder, which is composed of an adder circuit made up of an operational amplifier or the like, which adds and outputs the output signals of the multiplier 107, the first correction signal generator 108, and the second correction signal generator 109.

Reference numeral 111 denotes a signal switching unit, which includes an analog switch made of a semiconductor such as a transistor, and the like. The output voltage signal of the adder 110 is input to an output terminal 112, which will be described later, and the output voltages of the first variable voltage generator 103 and the second variable voltage generator 104 are input to a multiplier 107. In some cases, the output voltage signal of the adder 110 is output to an analog-digital converter 113 described later.

An output terminal 112 is made of a conductive metal such as copper, and outputs a voltage signal that is directly proportional to the power of the system under measurement output by the signal switching unit 111.

Reference numeral 113 denotes an analog-digital conversion unit, which is configured by a circuit made of a semiconductor such as a transistor, and converts a voltage signal output from the signal switching unit 111 into a digital signal.

Reference numeral 114 denotes a control unit configured by a microcomputer or the like, and includes a first signal selection unit 105, a second signal selection unit 106, a first variable voltage generation unit 103, a second variable voltage generation unit 104, and a signal. The switching unit 111 is controlled. Further, the control unit 114 multiplies the reference voltage generated by the first variable voltage generation unit 103 and the second variable voltage generation unit 104, which is analog-digital converted by the analog-digital conversion unit 113, by the multiplication unit 107. The first correction signal generator 108 and the second correction signal generator 109 are controlled according to the digital signal corresponding to the output voltage.

  Next, the operation of this embodiment will be described.

As described above, the multiplier 107 uses a circuit called a Gilbert cell, for example. In the present embodiment, an embodiment in which a Gilbert cell type multiplier circuit is used for the multiplier 107 will be described.

The Gilbert cell type multiplication circuit is an analog type multiplication circuit that has been widespread in recent years, but its output voltage includes an error component that is not linear with respect to the multiplication result of the input voltage. The output voltage Ew1 is expressed by the following equation.

Ew1 = k · Ex · Ey + m · Ex ² + n · Ey ³ (1)

Here, Ex is a voltage input to the X side of the multiplier 107, and Ey is a voltage input to the Y side of the multiplier 107. k, m, and n are coefficients.

Therefore, the term m · Ex ² + n · Ey ^{3 in} the above formula is an error component, and in order to reduce the error, it is necessary to subtract the error component from the output voltage Ew1 of the multiplier 107.

  That is, it is possible to reduce the calculation error generated in the multiplication unit by performing the following calculation.

^{Ew1-m · Ex 2 -n ·} Ey 3 = k · Ex · Ey = Ew2 ··· (2)

Here, Ew2 is an output voltage in which the calculation error of the multiplier 107 is reduced.

The correction signal generator 108 converts the voltage Ex on the X input side of the multiplier 107 into −m · Ex ² . A square circuit may be prepared in advance for the correction signal generation unit 108, or a programmable function generation circuit may be used.

The correction signal generation unit 109 converts the voltage Ey on the Y input side of the multiplication unit 107 into −n · Ey ³ . The correction signal generator 108 may have a cube circuit prepared in advance, or a programmable function generator circuit may be used.

The operation of the present embodiment relating to the calculation procedure of the coefficient m of the calculation error −m · Ex ² due to the input voltage Ex on the X input side of the multiplier 107 will be described with reference to the program configuration diagram of FIG. This program is stored in a program memory (not shown) in the control unit 114 and controls the operation of the control unit 114.

First, the control unit 114 controls the signal switching unit 111 so that the output of the signal switching unit 111 is input to the analog-digital conversion unit 113 (step 201).

In addition, the first signal selection unit 105 outputs a signal from the first variable voltage generation unit 103, and the second signal selection unit 106 outputs a signal from the second variable voltage generation unit 104. Is controlled (step 202).

Further, control is performed so that the output signals of the first correction signal generator 108 and the second correction signal generator 109 become ‘0’ (step 203).

The hardware is set so that the multiplier 107 multiplies the voltages generated by the variable voltage generator 103 and the variable voltage generator 104 in the operations of steps 201 to 203 and the controller 114 can detect the calculation error. The

Next, the control unit 114 enters an operation for detecting the magnitude of the error in the output voltage.

The controller 114 sets the output voltage Ey0 of the second variable voltage generator 104 to “0v” (step 204). In the present embodiment, the output voltage Ey0 of the second variable voltage generator 104 is set to ‘0v’, but other voltages such as ‘1v’ may be used.

Next, the control unit 114 sets the output voltage Ex0 of the first variable voltage generation unit 103 to “+5 v” in order to detect the magnitude of the m · Ex ² term in the equation (1), and adds the addition unit 110, the signal A digital signal corresponding to the output signal of the multiplication unit 107 that has been analog-digital converted by the analog-digital conversion unit 113 is received via the switching unit 111 and stored in a storage unit (not shown) in the control unit 114 (step 205). ). The output signal at this time is Vxp5. In the present embodiment, the output voltage Ex0 of the first variable voltage generator 103 is set to “+5 v”, but other voltages such as “+2 v” may be used.

Further, the control unit 114 sets the output voltage Ex0 of the first variable voltage generation unit 103 to “−5v”, and performs multiplication that is analog-digital converted by the analog-digital conversion unit 113 via the addition unit 110 and the signal switching unit 111. A digital signal corresponding to the output signal of the unit 107 is received and stored in a storage unit (not shown) in the control unit 114 (step 206). The output signal at this time is Vxn5. In the present embodiment, the output voltage Ex0 of the first variable voltage generator 103 is set to “−5v”, but other voltages such as “−2v” may be used.

Next, the control unit 114 calculates the value of the coefficient m from the stored error voltage Vxp5 and error voltage Vxn5 (step 207). Specifically, since Ey is 0v, equation (1) is

Ew1 = k · Ex · Ey + m · Ex ² + n · Ey ³ = m · Ex ² (3)

Since Ex is + 5v and -5v, respectively,

| Vxp5 | = m · Ex ² = m · (+ 5v) ² (4)
| Vxn5 | = m · Ex ² = m · (−5v) ² (5)

It becomes. In order to obtain m from the average of the error voltage Vxp5 and the error voltage Vxn5, the following equation is obtained by summing the equations (4) and (5).

| Vxp5 | + | Vxn5 | = m · (+ 5v) ² + m · (−5v) ² (6)

If m is calculated from this,

m = (| Vxp5 | + | Vxn5 |) / ((+ 5v) ² + (− 5v) ² ) (7)

It becomes.

Next, the control unit 114 instructs the first correction signal generation unit 108 to output a voltage of −m · Ex ² (step 208).

In order to confirm that the calculation error is reduced, the control unit 114 generates the output voltage Ex0 of the first variable voltage generation unit 103 in a state where a voltage of −m · Ex ² is generated from the correction signal generation unit 108. The digital signal corresponding to the output signal of the multiplier 107 that has been analog-to-digital converted by the analog-to-digital converter 113 is received via the adder 110 and the signal switching unit 111 and is shown in the control unit 114. Store it in the storage unit that does not (step 209). The output signal at this time is Vxp1. In the present embodiment, the output voltage Ex0 of the first variable voltage generator 103 is set to “+1 v”, but may be set to other voltages, for example, “+0.1 v”.

Further, in order to confirm that the calculation error is reduced, the control unit 114 generates a voltage of −m · Ex ² from the first correction signal generation unit 108 and generates the first variable voltage generation unit. The output voltage Ex0 of 103 is set to “−1v”, and the digital signal corresponding to the output signal of the multiplier 107 that has been analog-digital converted by the analog-digital converter 113 is received via the adder 110 and the signal switch 111. The data is stored in a storage unit (not shown) in the control unit 114 (step 210). The output signal at this time is Vxn1. In the present embodiment, the output voltage Ex0 of the first variable voltage generator 103 is set to “−1v”, but other voltages such as “−0.1v” can also be used.

  Next, the control unit 114 determines whether the voltages Vxp1 and Vxn1 are within predetermined values (step 211). In the ideal state, the voltages Vxp1 and Vxn1 should be zero, but may not be zero due to an error generated in the circuit. If it is determined that the value is not within the predetermined value, the control unit 114 calculates again the value of m such that the error voltages Vxp5, Vxn5, Vxp1, and Vxn1 are averaged (step 212). If it is determined that the value is within the predetermined value, the operation of calculating the multiplier m of the correction signal generator 108 is terminated.

The operation of this embodiment relating to the calculation procedure of the coefficient n of the calculation error −n · Ey ³ caused by the input voltage Ey on the Y input side of the multiplier 107 will be described with reference to the program configuration diagram of FIG. This program is stored in a program memory (not shown) in the control unit 114 and controls the operation of the control unit 114.

First, the control unit 114 controls the signal switching unit 111 so that the output of the signal switching unit 111 is input to the analog-digital conversion unit 113 (step 301).

In addition, the first signal selection unit 105 outputs a signal from the first variable voltage generation unit 103, and the second signal selection unit 106 outputs a signal from the second variable voltage generation unit 104. Is controlled (step 302).

Further, control is performed so that the output signals of the first correction signal generator 108 and the second correction signal generator 109 become ‘0’ (step 303).

The hardware is set so that the multiplier 107 can multiply the voltages generated by the variable voltage generator 103 and the variable voltage generator 104 in the operations of steps 301 to 303 and the controller 114 can detect the calculation error. The

Next, the control unit 114 enters an operation for detecting the magnitude of the error in the output voltage.

The control unit 114 sets the output voltage Ex0 of the first variable voltage generation unit 103 to ‘0v’ (step 304). In the present embodiment, the output voltage Ex0 of the first variable voltage generator 103 is set to '0v', but other voltages, for example, '1v' may be used.

Next, the control unit 114 sets the output voltage Ey0 of the second variable voltage generation unit 104 to '+ 5v' in order to detect the size of the term n · Ey ^{3 in} the equation (1), and adds the addition unit 110, the signal A digital signal corresponding to the output signal of the multiplication unit 107 that has been analog-digital converted by the analog-digital conversion unit 113 is received via the switching unit 111 and stored in a storage unit (not shown) in the control unit 114 (step 305). ). The output signal at this time is Vyp5. In the present embodiment, the output voltage Ey0 of the second variable voltage generator 104 is set to “+5 v”, but other voltages such as “+2 v” may be used.

Further, the control unit 114 sets the output voltage Ey0 of the second variable voltage generation unit 104 to “−5v”, and performs multiplication that is analog-digital converted by the analog-digital conversion unit 113 via the addition unit 110 and the signal switching unit 111. A digital signal corresponding to the output signal of the unit 107 is received and stored in a storage unit (not shown) in the control unit 114 (step 306). The output signal at this time is Vyn5. In the present embodiment, the output voltage Ey0 of the second variable voltage generator 104 is set to “−5v”, but other voltages such as “−2v” may be used.

Next, the control unit 114 calculates the value of the coefficient n from the stored error voltage Vyp5 and error voltage Vyn5 (step 307). Specifically, since Ex = 0, equation (1) is

Ew1 = k · Ex · Ey + m · Ex ² + n · Ey ³ = n · Ey ³ (8)

And Ey is + 5v and -5v, respectively.

| Vyp5 | = | n · Ey ³ | = | n · (+ 5v) ³ | (9)
| Vyn5 | = | n · Ey ³ | = | n · (−5v) ³ | (10)

It becomes. In order to obtain n from the average of the error voltage Vyp5 and the error voltage Vyn5, the following equation is obtained by summing the equations (9) and (10).

| Vyp5 | + | Vyn5 | = | n · (+ 5v) ³ | + | n · (−5v) ³ |

From this, n is obtained as follows: n = (| Vyp5 | + | Vyn5 |) ÷ (| (+ 5v) ³ | + | (−5v) ³ |)
(12)

It becomes.

Next, the control unit 114 instructs the second correction signal generation unit 109 to output a voltage of −n · Ey ³ (step 308).

In order to confirm that the calculation error has been reduced, the control unit 114 generates a voltage of −n · Ey ³ from the second correction signal generation unit 109 in the state where the second variable voltage generation unit 104 The output voltage Ey0 is set to “+ 1v”, and the digital signal corresponding to the output signal of the multiplier 107 that has been analog-digital converted by the analog-digital converter 113 is received via the adder 110 and the signal switch 111, and the controller 114 This is stored in a storage unit (not shown) (step 309). The output signal at this time is Vyp1. In the present embodiment, the output voltage Ey0 of the second variable voltage generator 104 is set to “+1 v”, but other voltages, for example, “+0.1 v” may be used.

Further, in order to confirm that the calculation error is reduced, the control unit 114 generates a voltage of −n · Ey ³ from the second correction signal generation unit 109 in a state where the second variable voltage generation unit 109 The output voltage Ey0 of 104 is set to “−1v”, and a digital signal corresponding to the output signal of the multiplier 107 that has been analog-digital converted by the analog-digital converter 113 is received via the adder 110 and the signal switch 111. The data is stored in a storage unit (not shown) in the control unit 114 (step 310). The output signal at this time is Vyn1. In the present embodiment, the output voltage Ey0 of the second variable voltage generator 104 is set to “−1v”, but other voltages such as “−0.1v” may be used.

  Next, the control unit 114 determines whether the voltages Vyp1 and Vyn1 are within predetermined values (step 311). In the ideal state, the voltages Vyp1 and Vyn1 should be zero, but may not be zero due to an error generated in the circuit. If it is determined that the value is not within the predetermined value, the control unit 114 calculates again the value of n such that the error voltages Vyp5, Vyn5, Vyp1, and Vyn1 are averaged (step 312). When it is determined that the value is within the predetermined value, the operation of calculating the multiplier n of the correction signal generation unit 109 is terminated.

In the AC power measuring device, the n · Ey ³ term in the above equation may be very small or may be canceled as a whole, and n may not be calculated.

  The calculation operation of m and n is performed, for example, when the power measuring device is turned on or at regular intervals of one hour.

Thereafter, the control unit 114 instructs the first correction signal generation unit 108 to generate a voltage of −m · Ex ² and the second correction signal generation unit 109 to generate a voltage of −n · Ey ³ , and The first signal selector 105 selects a voltage signal that is directly proportional to the alternating current of the system under test of the second system, and the second signal so as to select a voltage signal that is directly proportional to the alternating voltage of the system under test from the terminal 102. The selection unit 106 controls the signal switching unit 111 so that the output is connected to the output terminal 112 side and starts power measurement (not shown in the figure). Then, a voltage obtained by adding the voltage −m · Ex ^{2 and the} voltage −n · Ey ³ to the output voltage multiplied by the multiplier 107 is output by the adder 110. as a result

Ew1-m · Ex ² -n · Ey ³
= K · Ex · Ey + m · Ex ² + n · Ey ³ −m · Ex ² −n · Ey ³
= K · Ex · Ey · · · (13)

Is output from the output terminal 112.

As a result of this series of operations, a voltage that is directly proportional to the power of the system under test and that has few calculation errors due to multiplication is output from the output terminal 112.

  As described above, by using the present embodiment, it is possible to provide a power measurement device that can reduce a calculation error that is not directly proportional to an input signal or an output signal generated in a multiplier.

  In addition, it is possible to provide a power measuring device with improved temperature characteristics and aging characteristics by performing an error correction operation at regular intervals.

The block diagram which shows the structure of Example 1 of the electric power measuring apparatus by this invention The program block diagram which shows the program of Example 1 by this invention The program block diagram which shows the program of Example 1 by this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Power measuring device main body 101 Terminal part 102 Terminal part 103 Variable voltage generation part 104 Variable voltage generation part 105 Signal selection part 106 Signal selection part 107 Multiplication part 108 Correction signal generation part 109 Correction signal generation part 110 Addition part 111 Signal switching part 112 Output terminal 113 Analog-digital conversion unit 114 Control unit

Claims (4)

First variable voltage generating means for generating a reference signal;
First signal selecting means for selecting one signal out of a signal directly proportional to the current of the system under measurement and a signal generated by the first variable voltage generating means;
Second variable voltage generating means for generating a reference signal;
Second signal selection means for selecting one signal out of a signal directly proportional to the voltage of the system under measurement and a signal generated by the second variable voltage generation means;
A signal directly proportional to the current of the measured system selected by the first signal selecting means and a signal directly proportional to the voltage of the measured system selected by the second signal selecting means, or the first signal selection Multiplying means for multiplying the signal generated by the first variable voltage generating means selected by the means and the signal generated by the second variable voltage generating means selected by the second signal selecting means;
The signal generated by the first variable voltage generation means selected by the first signal selection means and the second variable selected by the second signal selection means multiplied by the multiplication means. Error detecting means for detecting an error of a signal representing a product of signals generated by the voltage generating means;
Correction signal generation means for converting a signal detected by the error detection means and a signal directly proportional to the current of the system under measurement selected by the first signal selection means into a correction signal;
The product of the signal directly proportional to the current of the system under measurement selected by the first signal selection means multiplied by the multiplication means and the signal directly proportional to the voltage of the system under measurement selected by the second signal selection means. An electric power measuring apparatus comprising: an adding means for adding a signal representing the correction signal and the correction signal converted by the correction signal generating means. First variable voltage generating means for generating a reference signal;
First signal selecting means for selecting one signal out of a signal directly proportional to the current of the system under measurement and a signal generated by the first variable voltage generating means;
Second variable voltage generating means for generating a reference signal;
Second signal selection means for selecting one signal out of a signal directly proportional to the voltage of the system under measurement and a signal generated by the second variable voltage generation means;
A signal directly proportional to the current of the measured system selected by the first signal selecting means and a signal directly proportional to the voltage of the measured system selected by the second signal selecting means, or the first signal selection Multiplying means for multiplying the signal generated by the first variable voltage generating means selected by the means and the signal generated by the second variable voltage generating means selected by the second signal selecting means;
The signal generated by the first variable voltage generation means selected by the first signal selection means and the second variable selected by the second signal selection means multiplied by the multiplication means. Error detecting means for detecting an error of a signal representing a product of signals generated by the voltage generating means;
First correction signal generation means for converting a signal detected by the error detection means and a signal directly proportional to the current of the system under measurement selected by the first signal selection means into a first correction signal;
Second correction signal generation means for converting a signal detected by the error detection means and a signal directly proportional to the voltage of the system under measurement selected by the second signal selection means into a second correction signal;
The product of the signal directly proportional to the current of the system under measurement selected by the first signal selection means multiplied by the multiplication means and the signal directly proportional to the voltage of the system under measurement selected by the second signal selection means. An adding means for adding the first correction signal converted by the first correction signal generating means and the second correction signal converted by the second correction signal generating means; A power measuring apparatus comprising: The power measuring apparatus according to claim 1, wherein the error detection unit includes an analog-digital conversion unit. The power measurement apparatus according to claim 1, wherein the error detection unit performs error detection at regular intervals.

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