JP5864999B2 - Power measurement device, inverter control circuit, grid-connected inverter system, and power measurement method - Google Patents

Description

  The present invention relates to a power measurement device that measures active power or reactive power, an inverter control circuit that includes the power measurement device, a grid-connected inverter system that includes the inverter control circuit, and a power measurement method.

  2. Description of the Related Art Conventionally, a grid-connected inverter system has been developed that converts DC power generated by a solar cell or the like into AC power and supplies it to an electric power system.

  FIG. 12 is a block diagram for explaining a conventional general grid-connected inverter system.

  The grid-connected inverter system A100 converts the DC power generated by the DC power source 1 into AC power and supplies it to the three-phase power system B. Hereinafter, the three phases are referred to as a U phase, a V phase, and a W phase.

  The inverter circuit 2 converts a DC voltage input from the DC power supply 1 into an AC voltage by switching a switching element (not shown). The filter circuit 3 removes a switching frequency component included in the AC voltage output from the inverter circuit 2. The transformer circuit 4 boosts (or steps down) the AC voltage output from the filter circuit 3 to the system voltage of the power system B. The inverter control circuit 700 receives the current signal and the voltage signal detected by the current sensor 5 and the voltage sensor 6, generates a PWM signal based on the current signal and the voltage signal, and outputs the PWM signal to the inverter circuit 2. The inverter circuit 2 performs switching of the switching element based on the PWM signal input from the inverter control circuit 700.

  The inverter control circuit 700 detects the output active power and the output reactive power, and performs feedback control for making these coincide with the target values. The power measuring unit 710 receives the active power P and the reactive power from the voltage signal V (Vu, Vv, Vw) input from the voltage sensor 6 and the current signal I (Iu, Iv, Iw) input from the current sensor 5. Q is calculated. The power control unit 72 generates a compensation signal for active power control and a compensation signal for reactive power control based on the active power P and the reactive power Q calculated by the power measurement unit 710.

The power measuring unit 710 converts the voltage signals Vu, Vv, and Vw into an α-axis voltage signal Vα and a β-axis voltage signal Vβ that are orthogonal to each other, and the current signals Iu, Iv, and Iw are orthogonal to each other. Converted to the shaft current signal Iβ, the active power P is calculated by the following equation (1), and the reactive power Q is calculated by the following equation (2).
P = Vα · Iα + Vβ · Iβ (1)
Q = −Vβ · Iα + Vα · Iβ (2)

Yasufumi Akagi, Kihei Kanazawa, Mitsuaki Fujita, Akira Namba, “Generalized theory of instantaneous reactive power and its application”, IEEJ Transactions B, Vol.103, No.7, July 1983, p. 41- Page 48

  However, since the power system B includes an AC signal for the negative phase in addition to the AC signal for the positive phase of the fundamental wave, the power measurement unit 710 calculates the active power and reactive power for the positive phase of the fundamental wave. It cannot be measured accurately. That is, since the voltage signal V input from the voltage sensor 6 and the current signal I input from the current sensor 5 also include signals for opposite phases, the active power P and the reactive power Q are calculated based on these signals. In such a case, these include errors due to the reverse phase component. Even if ripple is removed from the calculated active power P and reactive power Q by a low-pass filter or the like, the error cannot be completely removed.

For example, alpha V ₁ the amplitude of the positive phase of the fundamental wave contained in the shaft voltage signal Vα and β-axis voltage signal V?, When the amplitude of the reversed phase and V _-1,
Vα = V ₁ cos (ωt) + V ₋₁ cos (−ωt)
Vβ = V ₁ sin (ωt) + V ₋₁ sin (−ωt)
And the amplitude of the positive phase of the fundamental wave included in the α-axis current signal Iα and the β-axis current signal Iβ is I ₁ , and the amplitude of the opposite phase is I ₋₁ .
Iα = I ₁ cos (ωt−θ ₁ ) + I ₋₁ cos (−ωt−θ ₋₁ )
Iβ = I ₁ sin (ωt−θ ₁ ) + I ₋₁ sin (−ωt−θ ₋₁ )
It is represented by Θ ₁ is the phase difference between the current signal and the voltage signal for the positive phase, and θ ₋₁ is the phase difference between the current signal and the voltage signal for the reverse phase.

となり、これから直流分を抽出すると、
Ｐ＝Ｖ₁Ｉ₁cosθ₁＋Ｖ_-1Ｉ_-1cosθ_-1 ・・・ （３）
となる。上記（３）式に示すように、有効電力Ｐには、正相分の有効電力の他に、逆相分の有効電力も含まれている。 In this case, when the active power P is calculated by the above equation (1),

And when we extract the DC component from this,
P = V ₁ I ₁ cos θ ₁ + V ₋₁ I ₋₁ cos θ ₋₁ (3)
It becomes. As shown in the above equation (3), the active power P includes the active power for the reverse phase in addition to the active power for the normal phase.

Similarly, when the reactive power Q is calculated by the above equation (2) and the DC component is extracted,
Q = −V ₁ I ₁ sin θ ₁ −V ₋₁ I ₋₁ sin θ ₋₁ (4)
It becomes. As shown in the above equation (4), the reactive power Q includes the reactive power for the reverse phase in addition to the reactive power for the positive phase.

  If the active power and reactive power for the positive phase of the fundamental wave cannot be accurately measured, the inverter control circuit 700 cannot properly control the output active power and the output reactive power. In particular, when the reverse phase of power system B increases due to system disturbance such as a momentary drop, the calculated active power P and reactive power Q are far from the active power and reactive power for the positive phase of the actual fundamental wave. Therefore, the output active power and the output reactive power cannot be appropriately controlled.

  The present invention has been conceived under the circumstances described above, and accurately measures active power or reactive power of a predetermined component even when a plurality of signals are superimposed on a voltage signal and a current signal. The object is to provide a power measuring device capable of performing the above.

  In order to solve the above problems, the present invention takes the following technical means.

The power measuring device provided by the first aspect of the present invention is a power measuring device that measures active power or reactive power based on the detected voltage signal and current signal of each phase of the three-phase AC. A voltage signal converting means for converting the three voltage signals into a first voltage signal and a second voltage signal; and a current for converting the three current signals into a first current signal and a second current signal. A signal conversion means; a first component voltage signal that is a signal of a predetermined component included in the first voltage signal; and a second component voltage signal that is a signal of the predetermined component included in the second voltage signal. Are respectively extracted, a first component current signal that is a signal of the predetermined component included in the first current signal, and a predetermined component included in the second current signal. Second component current that is a signal Are extracted by the component current signal extracting unit, the first component voltage signal and the second component voltage signal extracted by the component voltage signal extracting unit, and the component current signal extracting unit. Power calculating means for calculating active power or reactive power from the first component current signal and the second component current signal, wherein the predetermined component is a fundamental wave or a harmonic of a three-phase AC signal. a positive phase or reverse phase of the wave, the component voltage signal extraction hand stage, said first voltage signal and the real component, the second voltage signal is input to complex signal to the imaginary component, the complex extracts each signal using the coefficient filter, wherein the component current signal extracting means, said first current signal and the real component, the second current signal is input complex signal to the imaginary component, complex coefficients And extracts each signal using a filter.

  In a preferred embodiment of the present invention, the complex coefficient filter used by the component voltage signal extraction unit or the component current signal extraction unit is a band pass type complex coefficient filter.

である。 In a preferred embodiment of the present invention, the transfer function H (z) by the z-transform expression of the complex coefficient filter has a normalized central angular frequency of the pass band as Ω _d (−π <Ω _d <π), and a pass band. Where r (0 <r <1), the imaginary unit is j, and the exponential function of the base of natural logarithm is exp ().

It is.

  In a preferred embodiment of the present invention, the complex coefficient filter used by the component voltage signal extraction means or the component current signal extraction means is a band rejection type complex coefficient filter.

である。 In a preferred embodiment of the present invention, the transfer function H (z) represented by the z-transform expression of the complex coefficient filter has a normalized central angular frequency of the stop band as Ω _d (−π <Ω _d <π), and a stop band. Where r (0 <r <1), the imaginary unit is j, and the exponential function of the base of natural logarithm is exp ().

It is.

  In a preferred embodiment of the present invention, the component voltage signal extraction unit or the component current signal extraction unit uses a filter in which a plurality of complex coefficient filters are connected in multiple stages.

In a preferred embodiment of the present invention, the power calculation means includes the first component voltage signal Vα, the second component voltage signal Vβ, the first component current signal Iα, and the second component voltage signal. When the component current signal is Iβ, the active power P is calculated by the following formula.

P = Vα · Iα + Vβ · Iβ

In a preferred embodiment of the present invention, the power calculation means includes the first component voltage signal Vα, the second component voltage signal Vβ, the first component current signal Iα, and the second component voltage signal. When the component current signal is Iβ, the reactive power Q is calculated by the following equation.

Q = −Vβ · Iα + Vα · Iβ

  In a preferred embodiment of the present invention, the predetermined component is a component of a fundamental wave of the three-phase alternating current.

  The inverter control circuit provided by the second aspect of the present invention performs output power control using active power or reactive power measured by the power measuring device provided by the first aspect of the present invention. And

  The grid interconnection inverter system provided by the third aspect of the present invention includes the inverter control circuit provided by the second aspect of the present invention and the inverter circuit controlled by the inverter control circuit. It is characterized by.

The power measurement method provided by the fourth aspect of the present invention is a power measurement method for measuring active power or reactive power based on the detected voltage signal and current signal of each phase of the three-phase alternating current. A first step of converting the three voltage signals into a first voltage signal and a second voltage signal; and a first step of converting the three current signals into a first current signal and a second current signal. 2, a first component voltage signal that is a signal of a predetermined component included in the first voltage signal, and a second component voltage signal that is a signal of the predetermined component included in the second voltage signal , A first component current signal that is a signal of the predetermined component included in the first current signal, and a signal of the predetermined component included in the second current signal. The second component current signal that is The first component voltage signal and the second component voltage signal extracted by the third step, the first component current signal extracted by the fourth step, and A fifth step of calculating active power or reactive power from the second component current signal, wherein the predetermined component is a positive phase component or a reverse phase component of a fundamental wave or a harmonic wave of a three-phase AC signal. min and the higher third Engineering, the first voltage signal and the real component, the second voltage signal is input to complex signal to an imaginary number component, extract each signal using the complex coefficient filter In the fourth step, a complex signal having the first current signal as a real component and the second current signal as an imaginary component is input, and each signal is extracted using a complex coefficient filter. Features.

  According to the present invention, a signal of a predetermined component is extracted from each voltage signal and each current signal by a complex coefficient filter, and active power or reactive power is calculated using the extracted signal of the predetermined component. Therefore, even when multiple signals are superimposed on each detected voltage signal and each current signal, only the signal of the predetermined component is extracted and calculation is performed, so that the active power and reactive power of the predetermined component are accurately measured. can do.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a block diagram for demonstrating the grid connection inverter system which concerns on 1st Embodiment. It is a block diagram for demonstrating the internal structure of the electric power measurement part which concerns on 1st Embodiment. It is a block diagram which shows the arithmetic processing of a complex coefficient band pass filter. It is a figure which shows the circuit structure which performs the complex arithmetic process of a complex coefficient band pass filter. It is a figure which shows the frequency characteristic of a complex coefficient band pass filter. It is a block diagram which shows the arithmetic processing of a complex coefficient notch filter. It is a figure which shows the circuit structure which performs the complex arithmetic process of a complex coefficient notch filter. It is a figure which shows the frequency characteristic of a complex coefficient notch filter. It is a block diagram for demonstrating the internal structure of the positive phase divided voltage signal extraction part which concerns on 3rd Embodiment. It is a figure which shows the frequency characteristic of the positive phase divided voltage signal extraction part which concerns on 3rd Embodiment. It is a block diagram for demonstrating the internal structure of the inverter control circuit which concerns on 4th Embodiment. It is a block diagram for demonstrating the conventional general grid connection inverter system.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, taking as an example a case where the power measuring device according to the present invention is provided in an inverter control circuit of a grid-connected inverter system.

  FIG. 1 is a block diagram for explaining a grid-connected inverter system according to the first embodiment.

  As shown in the figure, the grid-connected inverter system A includes a DC power source 1, an inverter circuit 2, a filter circuit 3, a transformer circuit 4, a current sensor 5, a voltage sensor 6, and an inverter control circuit 7.

  The DC power source 1 is connected to the inverter circuit 2. The inverter circuit 2, the filter circuit 3, and the transformer circuit 4 are connected in series to the output lines of the U-phase, V-phase, and W-phase output voltages in this order, and connected to the three-phase AC power system B. Yes. The current sensor 5 and the voltage sensor 6 are installed on the output side of the transformer circuit 4. The inverter control circuit 7 is connected to the inverter circuit 2. The grid interconnection inverter system A converts the DC power output from the DC power supply 1 into AC power and supplies it to the power grid B. In addition, the structure of the grid connection inverter system A is not restricted to this. For example, the current sensor 5 and the voltage sensor 6 may be provided on the input side of the transformer circuit 4, or other sensors necessary for controlling the inverter circuit 2 may be provided. Further, the transformer circuit 4 may be provided on the input side of the filter circuit 3, or a so-called transformer-less system in which the transformer circuit 4 is not provided. Further, a DC / DC converter circuit may be provided between the DC power supply 1 and the inverter circuit 2.

  The DC power source 1 outputs DC power and includes, for example, a solar battery. A solar cell generates direct-current power by converting solar energy into electrical energy. The DC power source 1 outputs the generated DC power to the inverter circuit 2. Note that the DC power source 1 is not limited to one that generates DC power from a solar cell. For example, the DC power source 1 may be a fuel cell, a storage battery, an electric double layer capacitor, a lithium ion battery, or AC power generated by a diesel engine generator, a micro gas turbine generator, a wind turbine generator, or the like. It may be a device that converts to DC power and outputs it.

  The inverter circuit 2 converts a DC voltage input from the DC power source 1 into an AC voltage and outputs the AC voltage to the filter circuit 3. The inverter circuit 2 is a three-phase inverter, and is a PWM control type inverter circuit including three sets of six switching elements (not shown). The inverter circuit 2 converts the DC voltage input from the DC power supply 1 into an AC voltage by switching each switching element on and off based on the PWM signal input from the inverter control circuit 7. In addition, the inverter circuit 2 is not limited to this, For example, a multilevel inverter may be sufficient.

  The filter circuit 3 removes high frequency components due to switching from the AC voltage input from the inverter circuit 2. The filter circuit 3 includes a low pass filter including a reactor and a capacitor. The AC voltage from which the high frequency component has been removed by the filter circuit 3 is output to the transformer circuit 4. The configuration of the filter circuit 3 is not limited to this, and any known filter circuit for removing high frequency components may be used. The transformer circuit 4 boosts or lowers the AC voltage output from the filter circuit 3 to a level substantially the same as the system voltage.

  The current sensor 5 detects the alternating current of each phase output from the transformer circuit 4 (that is, the output current of the grid interconnection inverter system A). The detected current signal I (Iu, Iv, Iw) is input to the inverter control circuit 7. The voltage sensor 6 detects the system voltage of each phase of the power system B. The detected voltage signal V (Vu, Vv, Vw) is input to the inverter control circuit 7. Note that the output voltage output by the grid interconnection inverter system A substantially matches the grid voltage.

  The inverter control circuit 7 controls the inverter circuit 2 and is realized by, for example, a microcomputer. The inverter control circuit 7 commands the waveform of the output voltage output from the grid-connected inverter system A based on the current signal I input from the current sensor 5 and the voltage signal V input from the voltage sensor 6. The command value signal is generated, and a pulse signal generated based on the command value signal is output as a PWM signal. The inverter circuit 2 outputs an alternating voltage having a waveform corresponding to the command value signal by switching each switching element on and off based on the input PWM signal.

  The inverter control circuit 7 controls the output power and the output current by changing the waveform of the command value signal to change the waveform of the output voltage of the grid interconnection inverter system A. That is, the inverter control circuit 7 detects the output active power and the output reactive power, performs feedback control for matching these to the target value, detects the output current, and matches this to the target value. Perform feedback control. A compensation signal for feedback control of output power is used as a target value for feedback control of output current, and a compensation signal for feedback control of output current is added to a signal based on voltage signal V to give a command value. A signal is generated. In FIG. 1, only the configuration for performing output power control and output current control is described, and the other configurations are omitted.

  The inverter control circuit 7 includes a power measurement unit 71, a power control unit 72, a current control unit 73, a system counter component generation unit 74, and a PWM signal generation unit 75.

  The power measuring unit 71 is based on the current signal I (Iu, Iv, Iw) input from the current sensor 5 and the voltage signal V (Vu, Vv, Vw) input from the voltage sensor 6. The output active power and output reactive power of A are calculated. The power measuring unit 71 outputs the active power P and the reactive power Q as the calculation results to the power control unit 72. Details of the arithmetic processing performed by the power measuring unit 71 will be described later.

  The power control unit 72 generates a compensation signal for active power control and a compensation signal for reactive power control based on the active power P and the reactive power Q input from the power measuring unit 71. The power control unit 72 is for performing feedback control (for example, PI control) for matching the active power P and the reactive power Q with the respective target values, and a compensation signal for the control is supplied to the current control unit. To 73.

  The current control unit 73 generates a compensation signal for current control based on the current signal I (Iu, Iv, Iw) input from the current sensor 5. The current control unit 73 performs a so-called three-phase / two-phase conversion process (αβ conversion process) and a rotation coordinate conversion process (dq conversion process), and converts the three current signals Iu, Iv, Iw into two d-axis current signals and Convert to q-axis current signal. Then, feedback control (for example, PI control) for matching the d-axis current signal and the q-axis current signal with the compensation signal for active power control and the compensation signal for reactive power control input from the power control unit 72, respectively. )I do. Further, the current control unit 73 converts the two compensation signals generated for the control into 3 so-called static coordinate conversion processing (inverse dq conversion processing) and two-phase / three-phase conversion processing (inverse αβ conversion processing). Convert to one compensation signal and output.

  The system counter component generation unit 74 receives the voltage signal V (Vu, Vv, Vw) from the voltage sensor 6 and generates and outputs a system command value signal. The system command value signal serves as a reference for the command value signal for commanding the waveform of the output voltage output from the grid interconnection inverter system A. The system command value signal output from the system counter component generation unit 74 and the three compensation signals output from the current control unit 73 are added to calculate the command value signal and input to the PWM signal generation unit 75.

  The PWM signal generation unit 75 generates a PWM signal by a triangular wave comparison method based on an input command value signal and a carrier signal generated as a triangular wave signal having a predetermined frequency (for example, 4 kHz). In the triangular wave comparison method, a command value signal and a carrier signal are respectively compared. For example, a pulse signal that is high when the command value signal is larger than the carrier signal and low when it is smaller is generated as a PWM signal. The generated PWM signal is output to the inverter circuit 2.

  Next, details of the power measuring unit 71 will be described with reference to FIGS.

  FIG. 2 is a block diagram for explaining the internal configuration of the power measuring unit 71.

  As shown in the figure, the power measuring unit 71 includes a voltage signal three-phase / two-phase conversion unit 711, a current signal three-phase / two-phase conversion unit 712, a positive phase divided voltage signal extraction unit 713, and a positive phase divided current signal extraction. Unit 714 and power calculation unit 715.

  The voltage signal three-phase / two-phase converter 711 converts the three voltage signals Vu, Vv, Vw input from the voltage sensor 6 into an α-axis voltage signal Vα and a β-axis voltage signal Vβ. The voltage signal three-phase / two-phase conversion unit 711 performs so-called three-phase / two-phase conversion processing (αβ conversion processing), and converts the voltage signals Vu, Vv, Vw into orthogonal α-axis components and β-axis components. Respectively, and the α-axis voltage signal Vα and the β-axis voltage signal Vβ are generated by combining the axis components.

The conversion process performed by the voltage signal three-phase / two-phase conversion unit 711 is represented by a determinant represented by the following equation (5).

  The current signal three-phase / two-phase converter 712 converts the three current signals Iu, Iv, Iw input from the current sensor 5 into an α-axis current signal Iα and a β-axis current signal Iβ. The current signal three-phase / two-phase conversion unit 712 performs a so-called three-phase / two-phase conversion process (αβ conversion process). The current signals Iu, Iv, Iw are converted into an α-axis component and a β-axis component orthogonal to each other. To generate the α-axis current signal Iα and the β-axis current signal Iβ.

The conversion process performed by the current signal three-phase / two-phase conversion unit 712 is expressed by a determinant represented by the following equation (6).

  The positive phase divided voltage signal extraction unit 713 extracts a signal for the positive phase of the fundamental wave from the α-axis voltage signal Vα and the β-axis voltage signal Vβ input from the voltage signal three-phase / two-phase conversion unit 711. Yes, a complex coefficient band-pass filter (band-pass complex coefficient filter) is provided.

The complex coefficient bandpass filter is composed of a complex coefficient first-order IIR filter whose transfer function H (z) expressed by z-transform is expressed by the following equation (7). In the following equation (7), f _d in the complex coefficient a ₁ is a normalized frequency obtained by normalizing the center frequency f _{0 of the} passband with the sampling frequency. Ω _d is a normalized angular frequency. For example, if the sampling frequency is f _sr , the normalized frequency f _d is f ₀ / f _sr , and the normalized angular frequency Ω _d is 2π · f _d = 2π · (f ₀ / f _sr ). The normalized angular frequency Ω _d is −π <Ω _d <π. R is a parameter (0 <r <1) that determines the bandwidth of the passband, j is an imaginary unit, and exp () is an exponential function of the base e of the natural logarithm.

FIG. 3 is a block diagram showing the arithmetic processing of the above equation (7). As shown in the figure, the complex-coefficient bandpass filter is configured by a circuit that multiplies the denominator arithmetic processing of equation (7) by a feedback circuit and multiplies the output of the feedback circuit by a numerator coefficient b _0. .

In the block diagram shown in FIG. 3, u [k] (k: index number representing discrete time) is input data, x [k] is state data, and y [k] is output data. Between input data u [k], state data x [k] and output data y [k]
x [k] = r.exp (j. [Omega] _d ) .x [k-1] + u [k] (8)
y [k] = (1-r) .x [k] (9)
Is established.

In the complex coefficient bandpass filter, regardless of whether the input data u [k] is complex data or real data (data in which the imaginary part of the complex data is “0”), the state data x [k] and the output data y [k] ] Is complex data. Accordingly, the input data u [k], state data x [k] and the output data y [k], respectively _{u [k] = u r [} k] + j · u j [k], x [k] = x r [ k] + j · x _j [k], y [k] = y _r [k] + j · y _j [k] complex data, and the complex coefficient a ₁ is a ₁ = r · exp (j · Ω _d ) = a _r + j · a _j = r · cos (Ω _d ) + j · r · sin (Ω _d ) is substituted into the above equations (8) and (9) and divided into relational expressions of the real part and the imaginary part. When,
_{x r [k] = r ·} cos (Ω d) · x r [k-1] -r · sin (Ω d) · x j [k-1] + u r [k] ··· (10)
x _j [k] = r · cos (Ω _d ) · x _j [k−1] + r · sin (Ω _d ) · x _r [k−1] + u _j [k] (11)
y _r [k] = (1−r) · x _r [k] (12)
y _j [k] = (1-r) · x _j [k] (13)
It becomes.

FIG. 4 is a diagram showing a circuit configuration for performing complex arithmetic processing of a complex coefficient bandpass filter based on the above equations (10) to (13). In the figure, coefficient a _r and coefficient a _j are the real part and imaginary part of complex coefficient a ₁ = r · exp (j · Ω _d ), respectively, and a _r = r · cos (Ω _d ), a _j = R · sin (Ω _d ).

As shown in the figure, the complex coefficient bandpass filter includes six multipliers 12a to 12f, two adders 12g and 12h, and two delay circuits 12i and 12j. The delay circuit 12i is a circuit that generates a real part x _r [k-1] of state data, and the delay circuit 12j is a circuit that generates an imaginary part x _j [k-1] of state data. The multipliers 12a and 12b are arithmetic units for calculating the first term and the second term (including a negative sign) of the above equation (10), respectively, and the adder 12g is the first term and the second term of the above equation (10). An arithmetic unit that adds the second term and the third term. Therefore, the real part x _r [k] of the state data represented by the above equation (10) is output from the adder 12g.

On the other hand, the multipliers 12c and 12d are arithmetic units for calculating the first term and the second term of the above equation (11), respectively, and the adder 12h is the first term, the second term and the third term of the above equation (11). It is an arithmetic unit that adds terms. Therefore, the imaginary part x _j [k] of the state data indicated by the above equation (11) is output from the adder 12h. The multipliers 12e and 12f are arithmetic units for calculating the above expressions (12) and (13), respectively.

In the present embodiment, the voltage signal three-phase / two-phase converter 711 converts the three voltage signals Vu, Vv, Vw into an α-axis voltage signal Vα and a β-axis voltage signal Vβ that are orthogonal to each other. Since the α-axis voltage signal Vα and the β-axis voltage signal Vβ can respectively correspond to the real part and the imaginary part of the complex data u _r + j · u _j , the sampling data of the α-axis voltage signal Vα is used as the real part of the input data. u _r [k] is input to the adder 12g, and sampling data of the β-axis voltage signal Vβ is input to the adder 12h as an imaginary part u _j [k] of the input data.

Each time sampling data of the α-axis voltage signal Vα is input, the delay circuit 12i, the multipliers 12a, 12b, and 12e and the adder 12g repeat the arithmetic processing of the above expressions (10) and (12). The output data y _r [k] is output from the multiplier 12e. The output data y _r [k] is obtained by extracting only the component corresponding to the normalized angular frequency Ω _d from the α-axis voltage signal Vα. Each time sampling data of the β-axis voltage signal Vβ is input, the delay circuit 12j, the multipliers 12c, 12d, 12f, and the adder 12h repeat the arithmetic processing of the above expressions (11) and (13). As a result, output data y _j [k] is output from the multiplier 12f. The output data y _j [k] is obtained by extracting only the component corresponding to the normalized angular frequency Ω _d from the β-axis voltage signal Vβ.

となり、(１−２ｒ・cos(Ω_d±ω)＋ｒ²)＝０を満たすωで極が表れるから、２次ＩＩＲフィルタはその極の周波数を通過させる特性を有する。ｒ≒１とすると、cos(Ω_d±ω)≒１より、２次ＩＩＲフィルタを通過させる正規化周波数ｆ_dはｆ_d＝±Ω_d／２πとなるから、実係数の２次ＩＩＲフィルタでは、正相分、逆相分とも通過させることになる。 When the bandpass filter is configured by a real coefficient second-order IIR filter, the transfer function H (z) (z = exp (j · ω)) of the second-order IIR filter is
H (z) = (1-r ² +2 (r-1) · r · cos (Ω _d ) · z ^-1 ) / (1-2r · cos (Ω _d ) · z ^-1 + r ² · z ^-2 )
It is represented by When the amplitude characteristic M (ω) of the transfer function H (z) is obtained,

Since the pole appears at ω that satisfies (1-2r · cos (Ω _d ± ω) + r ² ) = 0, the second-order IIR filter has a characteristic of passing the frequency of the pole. When r≈1, the normalized frequency f _d that passes through the second-order IIR filter is f _d = ± Ω _d / 2π from cos (Ω _d ± ω) ≈1, and therefore the real coefficient second-order IIR filter Both the positive phase portion and the reverse phase portion are allowed to pass through.

On the other hand, when the amplitude characteristic M (ω) of the transfer function H (z) shown in the above equation (7) is obtained,
M (ω) = (1-r) / √ {1-2r · cos (Ω _d −ω) + r ² }
Thus, a pole appears only in ω that satisfies (1-2r · cos (Ω _d −ω) + r ² ) = 0. Therefore, since the normalized frequency f _d that passes through the first-order IIR filter with complex coefficients is f _d = Ω _d / 2π, in the first-order IIR filter with complex coefficients, only one of the positive phase component and the opposite phase component is obtained. Can be passed.

The positive phase divided voltage signal extraction unit 713 extracts a signal for the positive phase of the fundamental wave from the α-axis voltage signal Vα and the β-axis voltage signal Vβ input from the voltage signal three-phase / two-phase conversion unit 711. is there. The extracted positive phase divided voltage signals V′α and V′β are output to the power calculator 715. As the normalized angular frequency Ω _d that determines the pass band of the complex-coefficient band-pass filter included in the positive phase divided voltage signal extraction unit 713, the angular frequency ω ₀ (for example, ω ₀ = Ω _d normalized 120 π [rad / sec] (60 [Hz])) is set in advance. The positive phase divided voltage signal extraction unit 713 inputs the α-axis voltage signal Vα and the β-axis voltage signal Vβ as input data u _r [k] and u _j [k] (see FIG. 4) to the complex coefficient bandpass filter, Output data y _r [k] and y _j [k] are output as positive phase divided voltage signals V′α and V′β.

FIG. 5 is a diagram illustrating frequency characteristics of a complex coefficient bandpass filter included in the positive phase divided voltage signal extraction unit 713. Since the central angular frequency of the passband is the angular frequency ω ₀ of the fundamental wave (normal phase) of the system voltage, signals of other angular frequencies (anti-phase and harmonic components) are preferably removed and the positive phase Only minutes can be extracted.

The positive phase current signal extraction unit 714 extracts a signal corresponding to the positive phase of the fundamental wave from the α-axis current signal Iα and the β-axis current signal Iβ input from the current signal three-phase / two-phase conversion unit 712. And a complex coefficient band pass filter similar to the positive phase divided voltage signal extraction unit 713 is provided. The extracted positive phase current signals I′α and I′β are output to the power calculator 715. Also normalized angular frequency Omega _d which determines the pass band of the complex coefficient band pass filter provided in the positive phase component current signal extracting section 714, similar to the positive phase component voltage signal extraction unit 713, sets a normalized angular frequency omega _d advance Has been. The positive phase current signal extraction unit 714 inputs the α-axis current signal Iα and the β-axis current signal Iβ as input data u _r [k] and u _j [k] (see FIG. 4) to the complex coefficient bandpass filter, Output data y _r [k] and y _j [k] are output as positive phase current signals I′α and I′β. The frequency characteristics of the complex coefficient bandpass filter included in the positive phase current signal extraction unit 714 also have the characteristics shown in FIG. 5, so that signals with angular frequencies other than the angular frequency ω ₀ (negative phase components and harmonic components) are preferably removed. Thus, only the positive phase can be extracted.

  Note that the complex coefficient band-pass filter included in the positive phase divided voltage signal extraction unit 713 and the positive phase divided current signal extraction unit 714 is not limited to the transfer function H (z) shown in the above equation (7). For example, it may be a complex coefficient band-pass filter configured by an IIR filter having a second or higher order complex coefficient.

The power calculation unit 715 calculates active power P and reactive power Q. The power calculation unit 715 includes the positive phase divided voltage signals V′α and V′β input from the positive phase divided voltage signal extraction unit 713 and the positive phase divided current signal I input from the positive phase divided current signal extraction unit 714. From 'α, I'β, active power P is calculated by the following equation (14), and reactive power Q is calculated by the following equation (15). The calculated active power P and reactive power Q are output to the power control unit 72.
P = V′α · I′α + V′β · I′β (14)
Q = −V′β · I′α + V′α · I′β (15)

  In the present embodiment, the three voltage signals Vu, Vv, Vw are converted into an α-axis voltage signal Vα and a β-axis voltage signal Vβ orthogonal to each other, and the three current signals Iu, Iv, Iw are orthogonal to each other. It is converted into Iα and β-axis current signal Iβ. The complex-coefficient band-pass filter extracts the positive phase voltage signals V′α and V′β from the α-axis voltage signal Vα and the β-axis voltage signal Vβ, and the positive-phase component from the α-axis current signal Iα and the β-axis current signal Iβ. Current signals I′α and I′β are extracted. Then, active power P and reactive power Q are calculated from the extracted positive phase divided voltage signals V′α and V′β and positive phase divided current signals I′α and I′β. Therefore, even if the detected voltage signals Vu, Vv, Vw and the current signals Iu, Iv, Iw are superposed with antiphase components or harmonic components, only the positive phase signals of the fundamental wave are extracted and calculated. Therefore, the active power and reactive power for the positive phase of the fundamental wave can be accurately measured.

  In the first embodiment, the case where the signal for the positive phase is extracted using the complex coefficient bandpass filter has been described. However, the signal for the positive phase is extracted using the complex coefficient notch filter (band rejection type complex coefficient filter). A signal may be extracted. The case where a complex coefficient notch filter is used will be described below as a second embodiment.

  The block diagram for explaining the internal configuration of the power measurement unit according to the second embodiment is common to that of the power measurement unit 71 of the first embodiment shown in FIG. In the second embodiment, the positive phase component voltage signal extraction unit 713 and the positive phase component current signal extraction unit 714 shown in FIG. 2 include complex coefficient notch filters. The positive-phase component voltage signal extraction unit 713 and the positive-phase component current signal extraction unit 714 extract the positive-phase component by the complex coefficient notch filter suppressing passage of the reverse-phase component.

The complex coefficient notch filter provided in the positive phase divided voltage signal extraction unit 713 and the positive phase divided current signal extraction unit 714 has a complex function first order with a transfer function H (z) expressed by z-transform expression expressed by the following equation (16). It consists of an IIR filter. In the following equation (16), Ω _d is the normalized central angular frequency of the stop band (−π <Ω _d <π), r is a parameter (0 <r <1) that determines the bandwidth of the stop band, j is an imaginary unit, and exp () is an exponential function of the base e of the natural logarithm.

  FIG. 6 is a block diagram showing the arithmetic processing of the above equation (16). FIG. 6 is obtained by adding a circuit that newly outputs a value obtained by subtracting output data y [k] from input data u [k] as output data e [k] to the block diagram shown in FIG. Since the output data is e [k], hereinafter, y [k] is simply referred to as data y [k]. Detailed description of the block diagram shown in FIG. 6 is omitted.

FIG. 7 is a diagram illustrating a circuit configuration for performing complex arithmetic processing of a complex coefficient notch filter. 7 adds an adder 12n after the real part multiplier 12e to the block diagram shown in FIG. 4, and the adder 12n converts the real part u _r [k] of the input data to the data y [k]. ] Is subtracted from the real part y _r [k] and the real part e _r [k] of the output data is output. Further, an adder 12o is added to the subsequent stage of the imaginary part multiplier 12f, and the adder 12o subtracts the imaginary part y _j [k] of the data y [k] from the imaginary part u _j [k] of the input data. Thus, the imaginary part e _j [k] of the output data is output. Detailed description of the arithmetic processing of the circuit shown in FIG. 7 is omitted.

A value obtained by subtracting the data y _r [k] output from the multiplier 12e from the input data u _r [k] is output as output data e _r [k]. Output data e _r [k] is such as to only suppress the corresponding components in the input data u _r [k] from the normalized angular frequency Omega _d. A value obtained by subtracting the data y _j [k] output from the multiplier 12f from the input data u _j [k] is output as output data e _j [k]. The output data e _j [k] is obtained by suppressing only the component corresponding to the normalized angular frequency Ω _d from the input data u _j [k].

As the normalized angular frequency Ω _d for determining the stop band of the complex coefficient notch filter included in the positive phase divided voltage signal extraction unit 713, the angular frequency “−ω ₀ ” of the negative phase of the fundamental wave of the system voltage is normalized. “−ω _d ” is preset. The positive phase divided voltage signal extraction unit 713 inputs the α-axis voltage signal Vα and the β-axis voltage signal Vβ as input data u _r [k] and u _j [k] to the complex coefficient notch filter, and outputs data e _r [k ] And e _j [k] are output as the positive phase divided voltage signals V′α and V′β.

FIG. 8 is a diagram illustrating frequency characteristics of the complex coefficient notch filter included in the positive phase divided voltage signal extraction unit 713. Since the central angular frequency of the stop band is the angular frequency “−ω ₀ ” of the negative phase of the fundamental wave of the system voltage, signals of other angular frequencies (positive phase) are preferably passed through and only the positive phase component is passed. Can be extracted.

Similarly to the positive phase component voltage signal extraction unit 713, the normalized angular frequency “−ω _d ” is also applied to the normalized angular frequency Ω _d that determines the stop band of the complex coefficient notch filter included in the positive phase component current signal extraction unit 714. It is set in advance. The positive phase current signal extraction unit 714 inputs the α-axis current signal Iα and the β-axis current signal Iβ as input data u _r [k] and u _j [k] to the complex coefficient notch filter, and outputs data e _r [k ] And e _j [k] are output as positive phase current signals I′α and I′β. The frequency characteristic of the complex coefficient notch filter included in the positive phase current signal extraction unit 714 also exhibits the characteristic of FIG. 8, so that signals having an angular frequency other than the angular frequency “−ω ₀ ” (positive phase) are preferably passed. Only the positive phase can be extracted.

  Note that the complex coefficient notch filter included in the positive phase divided voltage signal extraction unit 713 and the positive phase divided current signal extraction unit 714 is not limited to the transfer function H (z) shown in the above equation (16). For example, it may be a complex coefficient notch filter composed of a second or higher order IIR filter of complex coefficients.

  Also in the second embodiment, it is possible to extract the positive phase divided voltage signals V′α and V′β and the positive phase divided current signals I′α and I′β, respectively, and use these to extract the active power P and the invalidity. The power Q is calculated. Therefore, the same effect as that of the first embodiment can be obtained.

  In the second embodiment, the positive-phase component voltage signal extraction unit 713 and the positive-phase component current signal extraction unit 714 extract the positive-phase component by suppressing the passage of the negative component of the fundamental wave. Therefore, when the input signal includes a harmonic component, the positive phase component voltage signal extraction unit 713 and the positive phase current signal extraction unit 714 also pass the harmonic component. The case where the positive phase component of the fundamental wave is extracted with higher accuracy by suppressing the passage of the harmonic component when the power system B includes the harmonic component will be described below as a third embodiment. To do.

  FIG. 9 is a block diagram for explaining an internal configuration of the positive phase divided voltage signal extraction unit according to the third embodiment.

The positive phase divided voltage signal extraction unit 713 ′ shown in FIG. 9 includes four complex coefficient notch filters 713a to 713d connected in multiple stages, and thus the positive phase divided voltage signal extraction unit 713 according to the second embodiment. (See FIG. 2). The complex coefficient notch filter 713a is the same as the complex coefficient notch filter included in the positive phase divided voltage signal extraction unit 713 according to the second embodiment, and is for suppressing the reverse phase component of the fundamental wave. As the normalized angular frequency Ω _d for determining the stop band of the complex coefficient notch filter 713a, “−ω _d ” obtained by normalizing the angular frequency “−ω ₀ ” of the negative phase of the fundamental wave of the system voltage is set in advance. Yes. The complex coefficient notch filters 713b to 713d are for suppressing fifth-order, seventh-order, and eleventh-order harmonics (positive phase components), respectively. “−5ω _d ”, “7ω _d ”, and “−11ω _d ” are set in advance as normalized angular frequencies Ω _d that determine the stop bands of the complex coefficient notch filters 713b to 713d, respectively.

FIG. 10 is a diagram illustrating frequency characteristics of the positive phase divided voltage signal extraction unit 713 ′. According to the figure, the antiphase component of the fundamental wave (angular frequency “−ω ₀ ”), the fifth harmonic component (angular frequency “−5ω ₀ ”), the seventh harmonic component (angular frequency “7ω ₀ ”), The eleventh harmonic component (angular frequency “−11ω ₀ ”) is suppressed, and other components are passed. In the positive phase divided voltage signal extraction unit 713 ′, the complex coefficient notch filters 713a to 713d suppress not only the negative phase component of the fundamental wave but also the fifth, seventh, and eleventh harmonics (positive phase component). Thus, only the positive phase component of the fundamental wave can be passed more suitably.

In general, since the harmonics superimposed on the electric power system B are many fifth, seventh, and eleventh harmonics, these are suppressed in the present embodiment. In addition, what is necessary is just to design positive phase divided voltage signal extraction part 713 'according to the order of the harmonic which needs to be suppressed. For example, when it is desired to suppress only the fifth harmonic as the harmonic, it is sufficient to provide only the complex coefficient notch filters 713a and 713b. A complex coefficient notch filter in which “13ω _d ” is set as the angular frequency Ω _d may be further provided.

  Similarly, the positive phase current signal extraction unit (not shown, but for the sake of explanation, referred to as “positive phase current signal extraction unit 714 ′”) according to the third embodiment is the positive phase current signal extraction unit according to the second embodiment. Complex coefficient notch filters provided in the current signal extraction unit 714 and complex coefficient notch filters for suppressing the fifth, seventh, and eleventh harmonics (positive phase components) (complex coefficient notch filters 713b to 713d shown in FIG. 9), respectively. ). That is, it is the same as that of the positive phase divided voltage signal extraction unit 713 '. Since the frequency characteristic of the positive phase current signal extraction unit 714 ′ also shows the characteristic of FIG. 10, the negative phase component, the fifth harmonic component, the seventh harmonic component, and the eleventh harmonic component of the fundamental wave are suppressed. Component (the positive phase component of the fundamental wave) is passed. Therefore, only the positive phase component of the fundamental wave can be more suitably passed.

  In the third embodiment, even when harmonics are superimposed on the power system B, the positive phase component of the fundamental wave can be accurately extracted.

  In the first to third embodiments, the case where both the active power P and the reactive power Q are calculated has been described. However, the present invention is not limited to this. Only one of them may be calculated. For example, if the inverter control circuit 7 controls the output active power by the input DC voltage control, there is no need to calculate the active power P because the active power control is not necessary. This case will be described below as a fourth embodiment.

  FIG. 11 is a block diagram for explaining an internal configuration of the inverter control circuit according to the fourth embodiment. In the figure, the same or similar elements as those of the inverter control circuit 7 shown in FIG.

  The inverter control circuit 7 'is different from the inverter control circuit 7 in that the output active power is controlled by the input DC voltage control. Specifically, the power measuring unit 71 ′ calculates only the reactive power Q without calculating the active power P, and the power control unit 72 ′ is based on the reactive power Q input from the power measuring unit 71 ′. A compensation signal for reactive power control is generated and output to the current control unit 73. The DC voltage control unit 76 performs feedback control (for example, PI control) for making the DC voltage input from the DC power supply 1 to the inverter circuit 2 detected by the DC voltage sensor 8 coincide with the target value. A compensation signal for control is output to the current control unit 73. The output active power of the grid-connected inverter system A is controlled by the input DC voltage control by the DC voltage control unit 76.

  In the present embodiment, the power measuring unit 71 ′ extracts the positive phase divided voltage signals V′α and V′β and the positive phase divided current signals I′α and I′β, respectively, and uses them to react to the reactive power Q. Is calculated. Therefore, also in the fourth embodiment, the same effect as in the first embodiment can be obtained.

  In the first to fourth embodiments, the positive phase divided voltage signal extraction unit 713 (713 ′) and the positive phase divided current signal extraction unit 714 (714 ′) are both complex coefficient bandpass filters or complex coefficient notch filters. Although the case where it uses is demonstrated, it is not restricted to this. For example, the positive phase component voltage signal extraction unit 713 extracts the positive phase signal by passing the signal using the complex coefficient bandpass filter, and the positive phase component current signal extraction unit 714 (714 ′) uses the complex coefficient notch filter. The signal for the positive phase may be extracted by suppressing the passage of the signal for the reverse phase. Further, the positive-phase component voltage signal extraction unit 713 (713 ′) extracts the positive-phase signal by suppressing the passage of the negative-phase signal using the complex coefficient notch filter, and the positive-phase component current signal extraction unit. 714 may be extracted by passing a positive phase signal using a complex coefficient bandpass filter.

In the first to fourth embodiments, the normalized angular frequency Ω _d used in the positive phase divided voltage signal extraction unit 713 (713 ′) and the positive phase current signal extraction unit 714 (714 ′) is set in advance. However, the present invention is not limited to this. When the sampling period of the signal processing is a fixed sampling period, the angular frequency of the fundamental wave of the system voltage may be detected by a frequency detection device and the detected angular frequency may be normalized and used.

In the first to fourth embodiments, the case where the active power or reactive power of the fundamental wave is controlled has been described. However, the present invention is not limited to this. For example, in the complex coefficient filters of the positive phase voltage signal extraction unit 713 and the positive phase current signal extraction unit 714, the angular frequency of the negative phase of the fundamental wave is normalized as the normalized center angular frequency Ω _d of the pass band or stop band. By setting the normalized normalization angular frequency, it is possible to measure the active power or reactive power for the opposite phase of the fundamental wave. Similarly, by setting the normalized angular frequency obtained by normalizing the angular frequency of the fifth harmonic (positive phase) as the normalized center angular frequency Ω _d , the active power or reactive power of the fifth harmonic is measured. be able to. Therefore, active power or reactive power other than the fundamental wave can be controlled.

  In the first to fourth embodiments, the case where the power measuring device according to the present invention is incorporated in the inverter control circuit 7 has been described. However, the present invention is not limited to this. The power measuring device according to the present invention is provided separately from the inverter control circuit 7, and the calculated active power P (reactive power Q) is always displayed on the display device as the output active power (output reactive power) of the grid-connected inverter system. In the meantime, the active power P and the reactive power Q calculated by the power measuring device may be output to the inverter control circuit 7.

  In the said 1st thru | or 4th embodiment, although the case where the electric power measuring device which concerns on this invention was used for the grid connection inverter system was demonstrated, it is not restricted to this. The power measuring apparatus according to the present invention can be used alone as a measuring apparatus for measuring active power or reactive power of three-phase alternating current.

  The power measurement device, inverter control circuit, grid-connected inverter system, and power measurement method according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the power measuring device, the inverter control circuit, the grid-connected inverter system, and the power measuring method according to the present invention can be varied in design in various ways.

A Grid-connected inverter system 1 DC power supply 2 Inverter circuit 3 Filter circuit 4 Transformer circuit 5 Current sensor 6 Voltage sensor 7, 7 'Inverter control circuit 71, 71' Power measurement unit 711 Voltage signal three-phase / two-phase conversion unit (voltage Signal conversion means)
712 Current signal three-phase / two-phase converter (current signal converter)
713, 713 'positive phase divided voltage signal extraction unit (component voltage signal extraction means)
713a-713d Complex coefficient notch filter 714 Positive phase current signal extraction unit (component current signal extraction means)
715 Power calculation unit 72, 72 ′ Power control unit 73 Current control unit 74 System counter component generation unit 75 PWM signal generation unit 76 DC voltage control unit 8 DC voltage sensor B Power system

Claims (12)

A power measuring device that measures active power or reactive power based on a detected voltage signal of each phase of the three-phase alternating current and a current signal of each phase,
Voltage signal conversion means for converting the three voltage signals into a first voltage signal and a second voltage signal;
Current signal conversion means for converting the three current signals into a first current signal and a second current signal;
A first component voltage signal that is a signal of a predetermined component included in the first voltage signal and a second component voltage signal that is a signal of the predetermined component included in the second voltage signal are respectively extracted. Component voltage signal extraction means for
A first component current signal that is a signal of the predetermined component included in the first current signal and a second component current signal that is a signal of the predetermined component included in the second current signal, respectively. Component current signal extraction means for extracting;
The first component voltage signal and the second component voltage signal extracted by the component voltage signal extraction means, and the first component current signal and the second component extracted by the component current signal extraction means A power calculating means for calculating active power or reactive power from the current signal;
With
The predetermined component is a positive phase component or a reverse phase component of a fundamental wave or a harmonic wave of a three-phase AC signal,
The component voltage signal extraction means is input with a complex signal having the first voltage signal as a real component and the second voltage signal as an imaginary component, and extracts each signal using a complex coefficient filter,
The component current signal extraction means is input with a complex signal having the first current signal as a real component and the second current signal as an imaginary component, and extracts each signal using a complex coefficient filter.
A power measuring device characterized by that.   The power measurement device according to claim 1, wherein the complex coefficient filter used by the component voltage signal extraction unit or the component current signal extraction unit is a band-pass type complex coefficient filter. The transfer function H (z) represented by the z-transform representation of the complex coefficient filter has a normalized central angular frequency of the pass band Ω _d (−π <Ω _d <π), and a parameter that determines the pass band bandwidth r (0 <R <1), where imaginary unit is j and exponential function of base e of natural logarithm is exp (),

The power measurement device according to claim 2, wherein   The power measurement device according to claim 1, wherein the complex coefficient filter used by the component voltage signal extraction unit or the component current signal extraction unit is a band rejection type complex coefficient filter. The transfer function H (z) represented by the z-transform expression of the complex coefficient filter has a normalized central angular frequency of the stop band Ω _d (−π <Ω _d <π), and a parameter that determines the stop band bandwidth r (0 <R <1), where imaginary unit is j and exponential function of base e of natural logarithm is exp (),

The power measurement device according to claim 4, wherein   The power measurement device according to claim 4 or 5, wherein the component voltage signal extraction unit or the component current signal extraction unit uses a filter in which a plurality of complex coefficient filters are connected in multiple stages. When the first component voltage signal is Vα, the second component voltage signal is Vβ, the first component current signal is Iα, and the second component current signal is Iβ, the power calculation means is effective power P is calculated by the following formula,
The power measuring device according to any one of claims 1 to 6.

P = Vα · Iα + Vβ · Iβ When the first component voltage signal is Vα, the second component voltage signal is Vβ, the first component current signal is Iα, and the second component current signal is Iβ, the power calculation means is reactive power Q is calculated by the following formula,
The power measuring device according to any one of claims 1 to 7.

Q = −Vβ · Iα + Vα · Iβ   The power measuring device according to claim 1, wherein the predetermined component is a component of a fundamental wave of the three-phase alternating current.   An inverter control circuit that performs output power control using active power or reactive power measured by the power measuring device according to claim 1.   A grid-connected inverter system comprising the inverter control circuit according to claim 10 and an inverter circuit controlled by the inverter control circuit. A power measuring method for measuring active power or reactive power based on a detected voltage signal of each phase of the three-phase alternating current and a current signal of each phase,
A first step of converting the three voltage signals into a first voltage signal and a second voltage signal;
A second step of converting the three current signals into a first current signal and a second current signal;
A first component voltage signal that is a signal of a predetermined component included in the first voltage signal and a second component voltage signal that is a signal of the predetermined component included in the second voltage signal are respectively extracted. A third step of
A first component current signal that is a signal of the predetermined component included in the first current signal and a second component current signal that is a signal of the predetermined component included in the second current signal, respectively. A fourth step of extracting;
The first component voltage signal and the second component voltage signal extracted by the third step, and the first component current signal and the second component current signal extracted by the fourth step. A fifth step of calculating active power or reactive power from
With
The predetermined component is a positive phase component or a reverse phase component of a fundamental wave or a harmonic wave of a three-phase AC signal,
Wherein as third Engineering is to the first voltage signal and the real component, the second voltage signal is input to complex signal to an imaginary number component, it extracts each signal using the complex coefficient filter,
The fourth step receives a complex signal having the first current signal as a real component and the second current signal as an imaginary component, and extracts each signal using a complex coefficient filter.
A power measurement method characterized by that.

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