JP2009288070A - Device for measuring alternating current electric power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for measuring alternating current electric power for reducing double frequency components and having high electric power measurement precision. <P>SOLUTION: The device 140 for measuring alternating current power includes: a reference frequency circuit 141 for generating a reference frequency; a voltage phase delay circuit 142 for delaying the phase of a measurement alternating current voltage to generate a delay alternating current voltage based on the reference frequency; a current phase delay circuit 143 for delaying the phase of a measurement alternating current to generate a delay alternating current based on the reference frequency; and a power arithmetic circuit 144 for regarding an added value adding a multiplied value of the delay alternating current voltage and the delay alternating current to a multiplied value of the measurement alternating current voltage and the measurement alternating current as an active power, and regarding a subtracted value subtracting a multiplied value of the measurement alternating current voltage and the delay alternating current from a multiplied value of the measurement alternating current and the delay alternating current voltage as reactive power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AC power measuring apparatus that measures AC active power and reactive power.

Conventionally, in the measurement of single-phase AC power, the product of the voltage and current at the power measurement points measured by the voltage detection circuit 31 and the current detection circuit 34 is passed through a low-pass filter 149-1 as shown in FIG. The active power value was measured by the measurement circuit 145. Further, a function in which the current phase at the power measurement point is shifted by 90 degrees by the current phase delay circuit 143 is generated, and the product of this function and the voltage at the power measurement point is passed through the low-pass filter 149-2, and the reactive power value measurement circuit 146 The reactive power value was measured at (see, for example, Patent Document 1).
JP 59-150349 A

  In the conventional power measurement method, the product of the voltage and the current at the power measurement point and the product of the function and the voltage at the power measurement point have an amplitude of the magnitude of the apparent power, which is twice the frequency of the power measurement point. An AC component having a frequency (hereinafter, “AC component having a frequency twice the frequency of the power measurement point” will be referred to as “double frequency component”) will be included. In order to remove the double frequency component, it was necessary to lengthen the time constant of the low-pass filter. However, if the time constant of the low-pass filter is lengthened, the time response between the active power and the reactive power is delayed, and the deviation from the instantaneous value is increased, so that there is a problem in the response and accuracy of power measurement.

  Therefore, an object of the present invention is to provide an AC power measuring device that can reduce a double frequency component and has high power measurement accuracy.

  In order to achieve the above-mentioned object, the present invention calculates an active power value and a reactive power value from a measured AC voltage and a measured AC current at a power measurement point, and a delayed AC voltage and a delayed AC current whose phases are delayed. did.

  Specifically, the AC power measurement device according to the present invention includes a reference frequency circuit that generates a reference frequency, and a measurement AC voltage that is an AC voltage at a power measurement point based on the reference frequency from the reference frequency circuit. A delayed AC current is generated by delaying the phase of the measured AC current, which is the AC current at the power measurement point, based on the reference frequency from the reference frequency circuit and a voltage phase delay circuit that generates a delayed AC voltage by delaying the phase. A current phase delay circuit, an addition value obtained by adding a multiplication value of the delayed AC voltage and the delayed AC current to a multiplication value of the measurement AC voltage and the measurement AC current, and an active power value, A power calculation circuit having a reactive power value as a subtraction value obtained by subtracting a multiplication value of the measurement AC voltage and the delay AC current from a multiplication value of the delay AC voltage.

  By adding the multiplied value of the delayed AC voltage and the delayed AC current to the multiplied value of the measured AC voltage and the measured AC current, the double frequency component included in the active power value can be reduced. Further, the double frequency component included in the reactive power value can be reduced by subtracting the multiplication value of the measurement AC voltage and the delay AC current from the multiplication value of the measurement AC current and the delay AC voltage. The calculation of the active power value and the reactive power value performed by the AC power measuring apparatus according to the present invention will be described below.

ここで、Ｖ_ｓ：電力測定点の交流電圧の実効値、Ｉ_ｓ：電力測定点の交流電流の実効値、ω_ｓ：電力測定点の交流の角周波数である。 A measurement AC voltage V _s (t) that is an AC voltage at a power measurement point and a measurement AC current I _s (t) that is an AC current at a power measurement point whose phase is delayed by φ [rad] are expressed by Equation (1). The

Here, V _s : RMS value of AC voltage at power measurement point, I _S : RMS value of AC current at power measurement point, and ω _s : AC angular frequency at power measurement point.

ここで、ω_ｃｏ：測定装置の規準角周波数である。 Here, the delayed AC voltage V ″ _s (t) and the delayed AC current I ″ _s (t) in which the phases of the measured AC voltage V _s (t) and the measured AC current I _s (t) are delayed by π / (2ω _co ). ) Is expressed by Equation (2).

Where ω _co is the reference angular frequency of the measuring device.

Next, a calculated value PPP (t) and a calculated value QQQ (t) as shown in Equation (3) are considered. These calculated values are values (instantaneous values) determined with respect to an arbitrary time t.

数式（４）より、計算値ＰＰＰ（ｔ）は一定の有効電力値Ｖ_ｓＩ_ｓｃｏｓφに、振幅がＶ_ｓＩ_ｓｓｉｎψである２ω_ｓ成分（ｓｉｎ（２ω_ｓ・ｔ−φ＋ψ））が重畳したものになる。Ｖ_ｓＩ_ｓｓｉｎψが十分小さいので、計算値ＰＰＰ（ｔ）を有効電力値とすれば電力測定装置の有効電力の測定精度を向上させることができる。 First, a calculated value PPP (t) is obtained. When formula (1) and formula (2) are substituted into formula (3) and rearranged, formula (4) is obtained.

From Equation (4), the calculated value PPP (t) is superimposed on a constant active power value V _s I _s cosφ by a 2ω _s component (sin (2ω _s · t−φ + ψ)) whose amplitude is V _s I _s sin ψ. It will be. Since V _s I _s sin ψ is sufficiently small, the measurement accuracy of the active power of the power measuring device can be improved if the calculated value PPP (t) is the active power value.

ψが０に近いためｃｏｓψはほぼ１であり、計算値ＱＱＱ（ｔ）はほぼ無効電力値Ｖ_ｓＩ_ｓｓｉｎφとなる。この式には、２ω_ｓ成分は重畳しない。このため、計算値ＱＱＱ（ｔ）を無効電力値とすれば電力測定装置の無効電力の測定精度を向上させることができる。 Next, a calculated value QQQ (t) is obtained. When formula (1) and formula (2) are substituted into formula (3) and rearranged, formula (5) is obtained.

Since ψ is close to 0, cos ψ is almost 1, and the calculated value QQQ (t) is almost the reactive power value V _s I _s sinφ. The expression, 2 [omega _s component is not superimposed. For this reason, if the calculated value QQQ (t) is the reactive power value, the measurement accuracy of the reactive power of the power measuring apparatus can be improved.

  Therefore, the AC power measurement apparatus according to the present invention can reduce the double frequency component and increase the power measurement accuracy.

  The active power power calculation circuit of the AC power measuring apparatus according to the present invention preferably passes the added value through a low-pass filter to obtain the active power value. The double frequency component included in Equation (4) can be further reduced, and the accuracy of active power measurement can be further improved. In the reactive power power calculation circuit, the subtraction value can be passed through a low-pass filter to obtain the reactive power value.

The reference frequency circuit of the AC power measuring apparatus according to the present invention desirably synchronizes the reference frequency and the AC frequency at the power measurement point by a PLL or the like, but it may not be equal. If the angular frequency ω _s and the reference angular frequency ω _co are matched, ψ = 0 as shown in Equation (2). Therefore, V _s I _s sin ψ is 0, and the calculated value PPP (t) in Equation (4) is equal to the active power value. On the other hand, cos ψ is 1, and the calculated value QQQ (t) of Expression (5) is equal to the reactive power value, so that the measurement accuracy of the active power value and the reactive power value is further improved.

  The present invention can provide an AC power measuring device that can reduce double frequency components and has high power measurement accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. In the present specification and drawings, the same reference numerals denote the same components.

  In FIG.1 and FIG.2, the schematic block diagram of the alternating current power measuring apparatus of this embodiment is shown. The AC power measurement device 140 shown in FIGS. 1 and 2 receives the AC voltage value detected by the voltage detection circuit 31 and the AC current value detected by the current detection circuit 34 at the AC power measurement point. The current detection circuit 34 detects an AC current at an AC power measurement point via a current transformer 38.

  The AC power measuring apparatus 140 delays the phase of the measured AC voltage, which is the AC voltage at the power measurement point, based on the reference frequency circuit 141 that generates the reference frequency and the reference frequency from the reference frequency circuit 141, and generates the delayed AC voltage. A voltage phase delay circuit 142 to be generated; a current phase delay circuit 143 that generates a delayed AC current by delaying the phase of the measurement AC current that is an AC current at the power measurement point based on the reference frequency from the reference frequency circuit 141; The addition value obtained by adding the multiplication value of the delayed AC voltage from the voltage phase delay circuit 142 and the delayed AC current from the current phase delay circuit 143 to the multiplication value of the measurement AC voltage and the measurement AC current is used as the active power value. Multiplying the measured AC voltage and the delayed AC current from the current phase delay circuit 143 from the multiplied value of the current and the delayed AC voltage from the voltage phase delay circuit 142 It includes a power calculating circuit 144 to disable power value obtained by subtracting subtraction value.

  FIG. 2 is a diagram for explaining connections in the power calculation circuit 144 of FIG. The power calculation circuit 144 is a multiplier 147-1 that multiplies the measurement AC voltage and the measurement AC current, a multiplier 147-2 that multiplies the delay AC voltage and the delay AC current, and multiplies the measurement AC voltage and the delay AC current. And a multiplier 147-4 for multiplying the measured alternating current and the delayed alternating voltage. Furthermore, the power calculation circuit 144 subtracts the output of the multiplier 147-3 from the output of the adder 148-1 and the multiplier 147-4 that adds the output of the multiplier 147-1 and the output of the multiplier 147-2. A subtractor 148-2. The power calculation circuit 144 inputs the output of the adder 148-1 to the active power value measurement circuit 145 to measure the active power value, and inputs the output of the subtractor 148-2 to the reactive power value measurement circuit 146 to invalidate it. Measure the power value.

ここでの規準角周波数ω_ｃｏは規準周波数回路１４１が生成した規準周波数に基づいた角周波数である。規準周波数回路１４１は、電力測定点の周波数をモニタすることによって、規準周波数と電力測定点の交流の周波数とを同期させてもよい。 FIG. 3 shows an example of the voltage phase delay circuit 142. The same applies to the current phase delay circuit 143. The voltage phase delay circuit 142 outputs an output signal f ″ (t) obtained by delaying the input signal f (t) as shown in Equation (6).

The reference angular frequency ω _co here is an angular frequency based on the reference frequency generated by the reference frequency circuit 141. The reference frequency circuit 141 may synchronize the reference frequency and the AC frequency of the power measurement point by monitoring the frequency of the power measurement point.

  The power calculation circuit 144 may pass the addition value output from the adder 148-1 through the low-pass filter 149-1 and input it to the active power value measurement circuit 145. Further, the power calculation circuit 144 may pass the subtraction value output from the subtractor 148-2 through the low-pass filter 149-2 and input it to the reactive power value measurement circuit 146.

(simulation result)
A simulation was performed for the measurement with the conventional AC power measurement device and the measurement with the AC power measurement device of FIG. FIG. 4 shows the circuit on which the simulation was performed. An inductor Lo having an inductance of 127.3 mH and a resistor Ro having a resistance value of 100Ω were connected in series to the single-phase AC power supply 240 as a load. Single-phase AC power supply 240 corresponds to a measurement AC voltage at a power measurement point. The output voltage V _s of the single-phase AC power supply 240 was 141 sin (100πt).

従って、有効電力値Ｐ及び無効電力値Ｑとすると、それぞれ数式（８）のようになる。

An alternating current i that flows through the inductor Lo and the resistor Ro is expressed by Equation (7).

Accordingly, assuming that the active power value P and the reactive power value Q are given by Equation (8), respectively.

  FIG. 5 shows simulation waveforms of instantaneous values of the active power value P and the reactive power value Q when measured with a conventional AC power measuring device. Furthermore, the FFT result of this is shown in FIG. Moreover, the simulation waveform of the instantaneous value of the active power value P and the reactive power value Q at the time of measuring with the alternating current power measuring apparatus of FIG. 2 is shown in FIG. Furthermore, the FFT result of this is shown in FIG.

  Comparing the data of FIG. 5 to FIG. 8, when measured with a conventional AC power measuring device, the instantaneous value of the active power value P and the reactive power value Q is 100 Hz AC, and includes a double frequency component with a large amplitude. . On the other hand, when measured with the AC power measurement device of FIG. 2, the instantaneous value of the active power value P and the reactive power value Q becomes a direct current and does not include a double frequency component.

  As described above, since the AC power measuring device of FIG. 2 can reduce the double frequency component, the power measurement accuracy and responsiveness can be made higher than those of the conventional AC power measuring device.

  The AC power measuring device of the present invention can be applied to a single-phase power measuring device and an autonomous parallel operation control single-phase AC / DC converter that independently control the active power value and the reactive power value. Moreover, by using three units, it can be applied to a three-phase apparatus.

It is a schematic block diagram of the alternating current power measuring apparatus which concerns on this invention. It is a schematic block diagram of the alternating current power measuring apparatus which concerns on this invention. It is an example of the voltage phase delay circuit which the alternating current power measuring apparatus which concerns on this invention has. It is a schematic block diagram of the alternating current power measuring apparatus which performed simulation. It is a simulation waveform of the instantaneous value of the active power value P and the reactive power value Q when measured by a conventional AC power measuring device. It is the FFT result of the simulation waveform of the instantaneous value of the active power value P and the reactive power value Q when measured by a conventional AC power measuring device. It is a simulation waveform of the instantaneous value of the active power value P and the reactive power value Q when measured by the AC power measuring device according to the present invention. It is a FFT result of the simulation waveform of the instantaneous value of the active power value P and the reactive power value Q when measured by the AC power measuring device according to the present invention. It is a schematic block diagram of the conventional alternating current power measuring device.

Explanation of symbols

31: Voltage detection circuit 34: Current detection circuit 38: Current transformer 40: Single phase AC power supply 140: AC power measuring device 141: Reference frequency circuit 142: Voltage phase delay circuit 143: Current phase delay circuit 144: Power calculation circuit 145 : Active power value measuring circuit 146: Reactive power value measuring circuit 147-1, 147-2, 147-3, 147-4: Multiplier 148-1: Adder 148-2: Subtractor 240: Single-phase AC power supply Lo : Inductor Ro: Resistance

Claims (4)

A reference frequency circuit for generating a reference frequency;
Based on the reference frequency from the reference frequency circuit, a voltage phase delay circuit that generates a delayed AC voltage by delaying the phase of the measurement AC voltage that is an AC voltage at a power measurement point;
Based on the reference frequency from the reference frequency circuit, a current phase delay circuit that generates a delayed alternating current by delaying the phase of the measured alternating current that is an alternating current at a power measurement point;
The addition value obtained by adding the multiplication value of the delayed AC voltage and the delayed AC current to the multiplication value of the measurement AC voltage and the measurement AC current is used as an active power value, and the multiplication of the measurement AC current and the delay AC voltage is performed. A power calculation circuit having a reactive power value as a subtraction value obtained by subtracting a multiplication value of the measured alternating voltage and the delayed alternating current from a value;
AC power measuring device comprising:   The AC power measuring apparatus according to claim 1, wherein the power calculation circuit passes the addition value through a low-pass filter to obtain the active power value.   The AC power measuring device according to claim 1, wherein the power calculation circuit passes the subtraction value through a low-pass filter to obtain the reactive power value.   4. The AC power measuring apparatus according to claim 1, wherein the reference frequency circuit synchronizes the reference frequency with an AC frequency at the power measurement point. 5.

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