JP2013083566A - Unbalance rate detection device and unbalance rate detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unbalance rate detection device for detecting unbalance rate with simple operation processing.SOLUTION: The unbalance rate detection device 1 for detecting three phase AC unbalance rate is provided with: a three phase/two phase conversion part 21 for converting detected three phase voltage signals into an α axis voltage signal and a βaxis voltage signal; a positive-phase-sequence component extraction part 22 for extracting a signal of positive-phase-sequence component of the α axis voltage signal and βaxis voltage signal; a negative-phase-sequence component extraction part 23 for extracting a signal of a negative-phase-sequence component; and an unbalance rate calculation part 24 for calculating the unbalance rate from the extracted signal of positive-phase-sequence component and signal of negative-phase-sequence component. The positive-phase-sequence component extraction part 22 and negative-phase-sequence component extraction part 23 use complex coefficient filter to extract respective signals. Signals of positive-phase-sequence component and signals of negative-phase-sequence component are easily extracted respectively, and the unbalance rate is easily calculated, so that unbalance rate is detectable with simple operation processing.

Description

  The present invention relates to an unbalance rate detection device and an unbalance rate detection method for detecting an unbalance rate of a three-phase alternating current.

  Conventionally, an unbalance rate detection device for detecting an unbalance rate of a three-phase alternating current has been developed.

  FIG. 10 is a block diagram for explaining a conventional general unbalance rate detection apparatus.

  The unbalance rate detection apparatus 100 detects the unbalance rate of the three-phase AC voltage of the three-phase power system. Hereinafter, the three phases of the three-phase power system are referred to as a U phase, a V phase, and a W phase, respectively. The voltage sensor 400 detects each line voltage of the three-phase power system, and detects the line voltage signal Vuv that detects the line voltage of the U phase with respect to the V phase and the line voltage of the V phase with respect to the W phase. The line voltage signal Vvw and the line voltage signal Vwu, in which the W-phase line voltage relative to the U-phase is detected, are output to the unbalance rate detection apparatus 100. The unbalance rate detection apparatus 100 detects the unbalance rate based on the line voltage signals Vuv, Vvw, Vwu input from the voltage sensor 400.

  The unbalance rate detection apparatus 100 includes a calculation unit 200 and a display unit 300. The calculation unit 200 calculates an unbalance rate, and is realized by, for example, a microcomputer. The calculation unit 200 outputs the unbalance rate k as a calculation result to the display unit 300. The display unit 300 displays the calculation result, and is realized by display means such as a monitor. The display unit 300 displays the unbalance rate k input from the calculation unit 200. The calculation unit 200 includes a reference voltage calculation unit 201, a normal phase voltage calculation unit 202, a negative phase voltage calculation unit 203, and an unbalance rate calculation unit 204.

The reference voltage calculation unit 201 calculates the reference voltage Vs from the line voltage signals Vuv, Vvw, Vwu input from the voltage sensor 400 according to the following equation (1). The reference voltage calculation unit 201 outputs the calculated reference voltage Vs to the normal phase voltage calculation unit 202 and the reverse phase voltage calculation unit 203.

Vs = (Vuv + Vvw + Vwu) / 2 (1)

The positive phase voltage calculation unit 202 calculates the positive phase voltage Vp from the line voltage signals Vuv, Vvw, Vwu and the reference voltage Vs input from the reference voltage calculation unit 201 by the following equation (2). is there. The positive phase voltage calculation unit 202 outputs the calculated positive phase voltage Vp to the unbalance rate calculation unit 204.

The negative phase voltage calculation unit 203 calculates the negative phase voltage Vn from the line voltage signals Vuv, Vvw, Vwu and the reference voltage Vs input from the reference voltage calculation unit 201 by the following equation (3). is there. The negative phase voltage calculation unit 203 outputs the calculated negative phase voltage Vn to the unbalance rate calculation unit 204.

The unbalance rate calculation unit 204 calculates the unbalance rate from the normal phase voltage Vp input from the normal phase voltage calculation unit 202 and the negative phase voltage Vn input from the negative phase voltage calculation unit 203 according to the following equation (4). k is calculated. The unbalance rate calculation unit 204 outputs the calculated unbalance rate k to the display unit 3.

k = (Vn / Vp) × 100 [%] (4)

Japanese Patent Laid-Open No. 10-232254

  However, in the case of the unbalance rate detection apparatus 100, there is a problem that the arithmetic processing performed by the arithmetic unit 200 is complicated.

  The present invention has been conceived under the circumstances described above, and an object of the present invention is to provide an unbalance rate detection device capable of detecting an unbalance rate with simpler arithmetic processing.

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

  The unbalance rate detection apparatus provided by the first aspect of the present invention includes three-phase two-phase conversion means for converting three signals based on a three-phase alternating current into a first signal and a second signal, and the first A positive phase signal that is a positive phase signal included in the first signal and a second positive phase signal that is a positive phase signal included in the second signal are respectively extracted. Phase extraction means, a first negative phase signal that is a negative phase signal included in the first signal, and a second negative phase that is a negative phase signal included in the second signal A negative phase component extracting means for extracting the respective partial signals, the first positive phase signal and the second positive phase signal extracted by the positive phase component extracting means, and the negative phase component extracting means. An unbalance rate calculation for calculating an unbalance rate from the first antiphase component signal and the second antiphase component signal extracted by And a stage, the positive phase component extracting means and said reverse-phase extraction means, characterized by each extracting each signal using the complex coefficient filter. Note that the “positive phase signal” is a signal having the same frequency and the same phase order as the three-phase AC fundamental wave, and the “negative phase signal” is a three-phase AC fundamental wave and frequency. The signals are the same but in reverse phase order.

  In a preferred embodiment of the present invention, the complex coefficient filter used by the positive phase component extracting unit or the negative phase component extracting unit is a band pass type complex coefficient filter.

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 ().

である。

It is.

  In a preferred embodiment of the present invention, the complex coefficient filter used by the positive phase component extracting unit or the negative phase component extracting unit is a band rejection type complex coefficient filter.

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 ().

である。

It is.

  In a preferred embodiment of the present invention, the normal phase extraction means or the reverse phase extraction means 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 unbalance rate calculation means includes the first positive phase signal as Xα, the second positive phase signal as Xβ, and the first negative phase signal as Yα. If the second antiphase signal is Yβ, the unbalance rate k is calculated using the following equation.

  In a preferred embodiment of the present invention, there is further provided display means for displaying the unbalance rate calculated by the unbalance rate calculation means.

  In a preferred embodiment of the present invention, the three signals are phase voltage signals obtained by detecting each phase voltage of three-phase alternating current.

  In a preferred embodiment of the present invention, the three signals are line voltage signals obtained by detecting line voltages of three-phase alternating current.

  The unbalance rate detection method provided by the second aspect of the present invention includes a first step of converting three signals based on a three-phase alternating current into a first signal and a second signal, and the first signal. A second positive phase signal that is a first positive phase signal that is a positive phase signal included in the second signal and a second positive phase signal that is a positive phase signal included in the second signal. A first negative phase signal that is a negative phase signal included in the first signal, and a second negative phase signal that is a negative phase signal included in the second signal, and Are extracted in the third step, the first positive phase signal and the second positive phase signal extracted in the second step, and the first step extracted in the third step. A fourth step of calculating an unbalance rate from one negative-phase component signal and the second negative-phase component signal, and the second step and Serial third step, characterized by respectively extracting each signal using the complex coefficient filter.

  According to the present invention, the signal for the positive phase and the signal for the negative phase are each easily extracted, and the unbalance rate is easily calculated from the signal for the positive phase and the signal for the negative phase. Therefore, the unbalance rate can be detected by a simple arithmetic process.

  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 imbalance rate detection apparatus 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 part extraction part which concerns on 3rd Embodiment. It is a figure which shows the frequency characteristic of the positive phase part extraction part which concerns on 3rd Embodiment. It is a block diagram for demonstrating the conventional general unbalance rate detection apparatus.

  Embodiments of the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a block diagram for explaining the unbalance rate detection apparatus according to the first embodiment.

  The unbalance rate detector 1 detects the unbalance rate of the three-phase AC voltage of the three-phase power system. The voltage sensor 4 detects each phase voltage of the three-phase power system. The phase voltage signal Vu detects the phase voltage of the U phase, the phase voltage signal Vv detects the phase voltage of the V phase, and the phase of the W phase. The phase voltage signal Vw whose voltage has been detected is output to the unbalance rate detection device 1. The unbalance rate detection device 1 detects the unbalance rate based on the phase voltage signals Vu, Vv, Vw input from the voltage sensor 4.

  The unbalance rate detection apparatus 1 includes a calculation unit 2 and a display unit 3. The computing unit 2 computes the unbalance rate, and is realized by, for example, a microcomputer. The calculation unit 2 outputs the unbalance rate k as a calculation result to the display unit 3. The display unit 3 displays the calculation result, and is realized by display means such as a monitor. The display unit 3 displays the unbalance rate k input from the calculation unit 2. The calculation unit 2 includes a three-phase / two-phase conversion unit 21, a normal phase extraction unit 22, a reverse phase extraction unit 23, and an unbalance rate calculation unit 24.

  The three-phase / two-phase converter 21 converts the three phase voltage signals Vu, Vv, Vw input from the voltage sensor 4 into an α-axis voltage signal Vα and a β-axis voltage signal Vβ. The three-phase / two-phase converter 21 performs a so-called three-phase / two-phase conversion process (αβ conversion process), and converts the phase voltage signals Vu, Vv, Vw into an α-axis component and a β-axis component orthogonal to each other. The α-axis voltage signal Vα and the β-axis voltage signal Vβ are generated by disassembling each of them and collecting the respective axis components.

The conversion process performed in the three-phase / two-phase conversion unit 21 is represented by a determinant represented by the following equation (5).

  The normal phase extraction unit 22 and the reverse phase extraction unit 23 extract a signal having a specific frequency component from the α-axis voltage signal Vα and the β-axis voltage signal Vβ input from the three-phase / two-phase conversion unit 21. And a complex coefficient band-pass filter (band-pass complex coefficient filter).

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 (6). In the following equation (6), 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. 2 is a block diagram showing the arithmetic processing of the above equation (6). As shown in the figure, the complex-coefficient bandpass filter is configured by a circuit that multiplies the denominator of the above equation (6) 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. 2, 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 · Ω _d ) · x [k−1] + u [k] (7)
y [k] = (1-r) .x [k] (8)
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 (7) and (8) 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] ... (9)
x _j [k] = r · cos (Ω _d ) · x _j [k−1] + r · sin (Ω _d ) · x _r [k−1] + u _j [k] (10)
y _r [k] = (1−r) · x _r [k] (11)
y _j [k] = (1−r) · x _j [k] (12)
It becomes.

FIG. 3 is a diagram showing a circuit configuration for performing complex arithmetic processing of the complex coefficient bandpass filter based on the above equations (9) to (12). 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 equation (9), respectively, and the adder 12g is the first term and the second term of the equation (9). 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 (9) 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 equation (10), respectively, and the adder 12h is the first term, the second term and the third term of the equation (10). It is an arithmetic unit that adds terms. Therefore, the imaginary part x _j [k] of the state data indicated by the above equation (10) is output from the adder 12h. The multipliers 12e and 12f are arithmetic units for calculating the expressions (11) and (12), respectively.

In the present embodiment, the three-phase / two-phase converter 21 converts the three phase 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 (9) and (11). 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. Further, every 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 (10) and (12). 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 (6) 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 component extraction unit 22 extracts a fundamental phase positive phase signal from the α-axis voltage signal Vα and the β-axis voltage signal Vβ input from the three-phase / two-phase conversion unit 21. The extracted positive phase signals Vαp and Vβp are output to the unbalance rate calculation unit 24. As the normalized angular frequency Ω _d for determining the pass band of the complex coefficient band pass filter included in the positive phase component extraction unit 22, the angular frequency ω ₀ (for example, ω ₀ = 120π [ [omega] _d normalized rad / sec] (60 [Hz])) is set in advance. The positive phase extraction unit 22 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. 3) to the complex coefficient bandpass filter, and outputs the output data. y _r [k] and y _j [k] are output as positive phase separated signals Vαp and Vβp.

FIG. 4A is a diagram illustrating frequency characteristics of the complex coefficient bandpass filter included in the positive phase component extraction unit 22. 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 negative phase component extraction unit 23 extracts a negative phase component signal of the fundamental wave from the α-axis voltage signal Vα and the β-axis voltage signal Vβ input from the three-phase / two-phase conversion unit 21. The extracted negative phase signals Vαn and Vβn are output to the unbalance rate calculation unit 24. As a normalized angular frequency Omega _d which determines the pass band of the complex coefficient bandpass filter is reverse-phase extraction section 23 comprises, fundamental angular frequency of the reversed phase of the system voltage is preset. Since the phase sequence of the negative phase component is opposite to that of the positive phase component, the angular frequency of the negative phase component is a negative value of the angular frequency of the positive phase component. That is, “−ω _d ” obtained by normalizing “−ω ₀ ”, which is a negative value of the angular frequency ω _{0 for} the positive phase, is set as the normalized angular frequency Ω _d . The anti-phase component extraction unit 23 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. 3) to the complex coefficient bandpass filter, and outputs the output data. y _r [k] and y _j [k] are outputted as antiphase signals Vαn and Vβn.

FIG. 4B is a diagram illustrating the frequency characteristics of the complex coefficient bandpass filter provided in the antiphase component extracting unit 23. Since the central angular frequency of the passband 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 and harmonic components) are preferably removed, Only the negative phase component of the fundamental wave can be extracted.

  Note that the complex coefficient bandpass filter provided in the positive phase component extraction unit 22 and the negative phase component extraction unit 23 is not limited to that of the transfer function H (z) shown in the above equation (6). 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 unbalance rate calculation unit 24 calculates the following (13) from the positive phase signals Vαp and Vβp input from the positive phase extraction unit 22 and the negative phase signals Vαn and Vβn input from the negative phase extraction unit 23. ) To calculate the unbalance rate k. The unbalance rate calculation unit 24 outputs the calculated unbalance rate k to the display unit 3.

  In the present embodiment, the three phase voltage signals Vu, Vv, Vw are converted into an α-axis voltage signal Vα and a β-axis voltage signal Vβ that are orthogonal to each other. From the α-axis voltage signal Vα and the β-axis voltage signal Vβ, the positive-phase component signals Vαp and Vβp and the negative-phase component signals Vαn and Vβn are easily extracted by complex coefficient band pass filters, respectively. Then, the unbalance rate k is easily calculated from the extracted positive phase signals Vαp and Vβp and the negative phase signals Vαn and Vβn. Therefore, the unbalance rate can be detected by a simple arithmetic process.

  In the first embodiment, the case of extracting a positive phase signal and a negative phase signal using a complex coefficient bandpass filter has been described. However, a complex coefficient notch filter (band rejection type complex coefficient filter) is used. A normal phase signal and a negative phase 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 unbalance rate detection apparatus according to the second embodiment is common to that of the unbalance rate detection apparatus 1 of the first embodiment shown in FIG. In the second embodiment, the normal phase extraction unit 22 and the negative phase extraction unit 23 illustrated in FIG. 1 include complex coefficient notch filters. The positive phase component extraction unit 22 extracts the positive phase component by suppressing the passage of the negative phase component by the complex coefficient notch filter, and the negative phase component extraction unit 23 suppresses the passage of the positive phase component by the complex coefficient notch filter. To extract the reverse phase.

The complex coefficient notch filter included in the positive phase component extraction unit 22 and the negative phase component extraction unit 23 includes a first-order IIR filter having a complex coefficient whose transfer function H (z) expressed by z-transform expression is expressed by the following equation (14). Has been. In the following equation (14), Ω _d is the normalized center 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. 5 is a block diagram showing the arithmetic processing of the above equation (14). FIG. 5 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. 5 is omitted.

FIG. 6 is a diagram illustrating a circuit configuration for performing complex arithmetic processing of a complex coefficient notch filter. 6 adds an adder 12n to the subsequent stage of the multiplier 12e of the real part to the block diagram shown in FIG. 3, and the adder 12n converts the data y [k] from the real part u _r [k] of the input data. ] 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. A detailed description of the arithmetic processing of the circuit shown in FIG. 6 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]. The output data _er [k] is obtained by suppressing only the component corresponding to the normalized angular frequency Ω _d from the α-axis voltage signal Vα. 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 β-axis voltage signal Vβ.

As the normalized angular frequency Ω _d that determines the stop band of the complex coefficient notch filter included in the positive phase extraction unit 22, the angular frequency “−ω ₀ ” of the negative phase of the fundamental wave of the system voltage is normalized. _d ”is preset. The positive phase extraction unit 22 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 the output data e _r [k] and e _j [k] is output as the positive phase signal Vαp, Vβp.

FIG. 7A is a diagram illustrating frequency characteristics of the complex coefficient notch filter included in the positive phase component extraction unit 22. 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.

As the normalized angular frequency Ω _d for determining the stop band of the complex coefficient notch filter included in the anti-phase component extraction unit 23, ω _{d obtained} by normalizing the angular frequency ω ₀ of the fundamental wave (positive phase component) of the system voltage is set in advance. Has been. Reverse-phase extraction unit 23, alpha input to complex coefficient notch filter axis voltage signals Vα and β-axis voltage signal Vβ as input data u _r [k] and u _j [k], the output data e _r [k] and e _j [k] is output as anti-phase signal Vαn, Vβn.

FIG. 7B is a diagram illustrating frequency characteristics of the complex coefficient notch filter included in the antiphase component extraction unit 23. Since the center angular frequency of the stop band is the angular frequency ω ₀ of the fundamental wave (forward phase) of the system voltage, signals of other angular frequencies (reverse phase) are preferably passed through, and the negative phase component of the fundamental wave is passed. Only can be extracted.

  Note that the complex coefficient notch filter provided in the positive phase component extracting unit 22 and the negative phase component extracting unit 23 is not limited to the one having the transfer function H (z) shown in the above equation (14). For example, it may be a complex coefficient notch filter composed of a second or higher order IIR filter of complex coefficients.

  Also in this embodiment, the positive phase signals Vαp and Vβp and the negative phase signals Vαn and Vβn can be easily extracted. Then, the unbalance rate k is easily calculated from the extracted positive phase signals Vαp and Vβp and the negative phase signals Vαn and Vβn. Therefore, the same effect as that of the first embodiment can be obtained.

  In the second embodiment, the positive phase component extraction unit 22 extracts the positive phase component by suppressing the passage of the fundamental wave in the negative phase component, and the negative phase component extraction unit 23 passes the fundamental wave (the positive phase component). The negative phase component is extracted by suppressing. Therefore, when the harmonic component is included in the α-axis voltage signal Vα and the β-axis voltage signal Vβ, the positive phase component extraction unit 22 and the negative phase component extraction unit 23 also pass the harmonic component. The case where the positive phase component or the reverse phase component of the fundamental wave is extracted with higher accuracy by suppressing the passage of the harmonic component when a harmonic component is included will be described below as a third embodiment. To do.

  FIG. 8 is a block diagram for explaining the internal configuration of the positive phase extraction unit according to the third embodiment.

The positive phase component extracting unit 22 ′ illustrated in FIG. 8 includes four complex coefficient notch filters 22a to 22d connected in multiple stages, and thus the positive phase component extracting unit 22 according to the second embodiment (see FIG. 1). ) Is different. The complex coefficient notch filter 22a is the same as the complex coefficient notch filter included in the positive phase component extraction unit 22 according to the second embodiment, and is for suppressing the negative phase component of the fundamental wave. As the normalized angular frequency Ω _d that determines the stop band of the complex coefficient notch filter 22a, “−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 22b to 22d are for suppressing fifth, seventh, and eleventh 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 22b to 22d, respectively.

FIG. 9A is a diagram illustrating the frequency characteristics of the positive phase extraction unit 22 ′. According in FIG. 6 (a), reverse phase (angular frequency "- [omega] ₀ ') of the fundamental wave, the fifth harmonic component (angular frequency" -5Omega ₀ "), the seventh harmonic component (angular frequency" 7Omega ₀ )), The 11th harmonic component (angular frequency “−11ω ₀ ”) is suppressed, and other components are passed. In the positive phase component extraction unit 22 ′, the complex coefficient notch filters 22a to 22d suppress not only the negative phase component of the fundamental wave but also the fifth, seventh, and eleventh harmonics (positive phase component). Only the positive phase portion of the wave can be passed more suitably.

In general, since the harmonics superimposed on the three-phase power system have many fifth, seventh, and eleventh harmonics, these are suppressed in this embodiment. In addition, what is necessary is just to design positive phase part extraction part 22 '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 22a and 22b. A complex coefficient notch filter in which “13ω _d ” is set as the angular frequency Ω _d may be further provided.

  Similarly, the negative phase component extraction unit 23 according to the second embodiment is the same as the negative phase component extraction unit (not shown, but referred to as “negative phase component extraction unit 23 ′”). And a complex coefficient notch filter (complex coefficient notch filters 22b to 22d shown in FIG. 8) for suppressing the fifth, seventh, and eleventh harmonics (positive phase components). .

FIG. 9B is a diagram illustrating the frequency characteristics of the negative phase extraction unit 23 ′. According to FIG. 5B, the positive phase component (angular frequency “ω ₀ ”) of the fundamental wave, the fifth harmonic component (angular frequency “−5ω ₀ ”), and the seventh harmonic component (angular frequency “7ω ₀ ”). ), The 11th harmonic component (angular frequency “−11ω ₀ ”) is suppressed, and other components are passed. In the negative phase component extracting unit 23 ′, not only the positive phase component of the fundamental wave but also the fifth, seventh, and eleventh harmonics (positive phase component) are suppressed, so that only the negative phase component of the fundamental wave is more suitable. Can be passed through.

  The third embodiment can accurately extract the normal phase component or the reverse phase component of the fundamental wave even when harmonics are superimposed on the three-phase power system.

  In the first to third embodiments, the case where both the positive phase extraction unit 22 (22 ′) and the negative phase extraction unit 23 (23 ′) use a complex coefficient bandpass filter or a complex coefficient notch filter will be described. However, it is not limited to this. For example, the positive phase component extraction unit 22 extracts the positive phase signal by passing the positive phase signal using the complex coefficient bandpass filter, and the negative phase component extraction unit 23 (23 ′) uses the complex coefficient notch filter to extract the positive phase component. You may make it extract a negative phase signal by suppressing passage of a signal. Further, the positive phase component extraction unit 22 (22 ′) extracts the positive phase signal by suppressing the passage of the negative phase signal using the complex coefficient notch filter, and the negative phase component extraction unit 23 detects the complex coefficient band pass. You may make it extract by allowing a negative phase signal to pass through using a filter.

In the first to third embodiments, the case where the normalized angular frequency Ω _d used in the normal phase extraction unit 22 (22 ′) and the reverse phase extraction unit 23 (23 ′) is set in advance will be described. However, it 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 third embodiments, the case where the voltage sensor 4 detects the phase voltage has been described. However, the present invention is not limited to this. For example, the present invention can be applied even when the voltage sensor 4 detects a line voltage. In this case, the determinant represented by the following equation (15) may be used for the conversion process performed by the three-phase / two-phase converter 21 instead of the determinant represented by the above equation (5). Further, a configuration for converting a line voltage signal into a phase voltage signal is added to the three-phase / two-phase conversion unit 21 to convert the line voltage signals Vuv, Vvw, Vwu into phase voltage signals Vu, Vv, Vw. Then, it may be converted into the α-axis voltage signal Vα and the β-axis voltage signal Vβ by the above equation (5).

  Further, the unbalance rate may be detected based on current signals Iu, Iv, and Iw input from the current sensor. In this case, the configurations of the first to third embodiments can be used as they are.

  In the first to third embodiments, the case where the calculated unbalance rate k is displayed on the display unit 3 has been described. However, the present invention is not limited to this. For example, when the unbalance rate k exceeds a predetermined threshold, a warning with a buzzer or the like may be given.

  In the first to third embodiments, the case where the unbalance rate detection apparatus according to the present invention is used alone has been described. However, the present invention is not limited to this. For example, an unbalance rate detection device may be incorporated into a grid-connected inverter system, and when the unbalance rate k exceeds a predetermined threshold, the inverter is stopped and the connection with the three-phase power system may be disconnected. . In this case, since it is not necessary to display the unbalance rate k, the display unit 3 may not be provided, or may be displayed on the display unit of the grid interconnection inverter system. Further, the voltage signal detected by the voltage sensor of the grid-connected inverter system may be input to the three-phase / two-phase converter 21.

  The unbalance rate detection apparatus and the unbalance rate detection method according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the unbalance rate detection apparatus and the unbalance rate detection method according to the present invention can be varied in design in various ways.

DESCRIPTION OF SYMBOLS 1 Unbalance rate detection apparatus 2 Computation part 21 Three-phase / two-phase conversion part 22,22 'Normal phase extraction part 23 Reverse phase extraction part 24 Unbalance rate calculation part 3 Display part 4 Voltage sensor

Claims (11)

Three-phase two-phase conversion means for converting three signals based on a three-phase alternating current into a first signal and a second signal;
A first positive phase signal that is a positive phase signal included in the first signal and a second positive phase signal that is a positive phase signal included in the second signal, respectively, Positive phase extraction means for extracting;
A first negative phase signal that is a negative phase signal included in the first signal and a second negative phase signal that is a negative phase signal included in the second signal, respectively, A reverse phase extraction means for extracting;
The first positive-phase component signal and the second positive-phase component signal extracted by the normal-phase component extraction unit, the first negative-phase component signal extracted by the negative-phase component extraction unit, and the first An unbalance rate calculating means for calculating an unbalance rate from the two negative phase signals;
With
The positive phase component extracting unit and the negative phase component extracting unit respectively extract each signal using a complex coefficient filter.
An unbalance rate detecting device characterized by that.   The unbalance rate detection apparatus according to claim 1, wherein the complex coefficient filter used by the positive phase component extracting unit or the negative phase component extracting 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 unbalance rate detection device according to claim 2, wherein   The unbalance rate detection apparatus according to claim 1, wherein the complex coefficient filter used by the positive phase component extracting unit or the negative phase component extracting 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 unbalance rate detection apparatus according to claim 4, wherein   The unbalance rate detection apparatus according to claim 4 or 5, wherein the positive phase component extraction unit or the negative phase component extraction unit uses a filter in which a plurality of complex coefficient filters are connected in multiple stages. The unbalance rate calculation means is configured to output the first positive phase signal as Xα, the second positive phase signal as Xβ, the first negative phase signal as Yα, and the second negative phase signal as X2. Assuming Yβ, the unbalance rate k is calculated using the following equation:
The unbalance rate detection apparatus according to any one of claims 1 to 6.

  The unbalance rate detection apparatus according to claim 1, further comprising display means for displaying the unbalance rate calculated by the unbalance rate calculation means.   The unbalance rate detection device according to any one of claims 1 to 8, wherein the three signals are phase voltage signals obtained by detecting respective phase voltages of three-phase alternating current.   The unbalance rate detection device according to any one of claims 1 to 8, wherein the three signals are line voltage signals obtained by detecting line voltages of three-phase alternating current. A first step of converting three signals based on a three-phase alternating current into a first signal and a second signal;
A first positive phase signal that is a positive phase signal included in the first signal and a second positive phase signal that is a positive phase signal included in the second signal, respectively, A second step of extracting;
A first negative phase signal that is a negative phase signal included in the first signal and a second negative phase signal that is a negative phase signal included in the second signal, respectively, A third step of extracting;
The first positive phase signal and the second positive phase signal extracted in the second step, the first negative phase signal and the second phase signal extracted in the third step A fourth step of calculating an unbalance rate from the negative phase signal;
With
In the second step and the third step, each signal is extracted using a complex coefficient filter.
An unbalance rate detection method characterized by the above.

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