JP2013090438A - Independent operation detection device, system interconnection inverter system, and independent operation detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an independent operation detection device that extracts an in-phase signal and an opposite-phase signal of an injected harmonic through simple processing.SOLUTION: The independent operation detection device that detects independent operation by injecting a predetermined inter-degree harmonic current to an electric power system by a single phase includes: a voltage signal three-phase/two-phase conversion section 61 which converts a detected three-phase voltage signal into voltage signals Vα, Vβ; a current signal three-phase/two-phase conversion section 63 which converts a detected three-phase current signals into current signals Iα, Iβ; voltage signal extraction parts 62a, 62b which extract in-phase signals Vαp, Vβp of inter-degree harmonics included in the voltage signals Vα, Vβ, and opposite-phase signals Vαn, Vβn; and current signal extraction parts 64a, 64b which extract in-phase signals Iαp, Iβp of inter-degree harmonics included in the current signals Iα, Iβ, and opposite-phase signals Iαn, Iβn. Complex coefficient filters are used to extract the in-phase and opposite-phase signals.

Description

  The present invention relates to an isolated operation detection device, a grid-connected inverter system including the isolated operation detection device, and an isolated operation detection 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 a connected load or power system.

  FIG. 10 is a block diagram for explaining a grid-connected inverter system provided with a conventional isolated operation detection device.

  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 connected load C and 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 device 2 converts a DC voltage input from the DC power source 1 into an AC voltage by switching a switching element (not shown). The inverter control device 3 receives the current signal and the voltage signal detected by the current sensor 4 and the voltage sensor 5, generates a PWM signal based on the current signal and the voltage signal, and outputs the PWM signal to the inverter device 2. The inverter device 2 performs switching of the switching element based on the PWM signal input from the inverter control device 3.

  When an accident occurs in the power system B, etc., the circuit breaker D is activated by the protective device provided on the power system B side, so that the grid-connected inverter system A100 is disconnected from the power system B (power failure). In this case, a single operation state in which power is supplied to the load C only from the grid-connected inverter system A100 is obtained. Under the condition where the output power of the grid interconnection inverter system A100 and the power consumption of the load C are balanced, the grid interconnection inverter system A100 cannot detect a power failure of the power grid B. In order to ensure the safety of maintenance workers, the grid interconnection inverter system A100 is provided with a function of detecting an isolated operation, disconnecting the load C from the grid interconnection inverter system A100, and automatically stopping the power conversion operation. ing. Further, when reclosing is performed immediately after being disconnected by the circuit breaker D, there is a case where a large overcurrent flows due to connection in a state where the phase is shifted. In this case, the circuit breaker D is disconnected again, and an upper substation of the electric power system B is also affected. In the worst case, there is a possibility that a wide-area power failure occurs. In order to prevent this, it is necessary to detect isolated operation appropriately and at high speed.

  The isolated operation detection device 600 is for detecting an isolated operation of the grid interconnection inverter system A100. When the isolated operation detection device 600 detects an isolated operation, the isolated operation detection device 600 outputs an open signal to the switch 8 and outputs a stop signal to the inverter control device 3. The switch 8 to which the open signal is inputted disconnects the connection between the grid interconnection inverter system A100 and the load C. Further, the inverter control device 3 to which the stop signal is input stops generating the PWM signal and stops the power conversion operation. Thereby, the independent operation state of grid connection inverter system A100 is avoided.

  The islanding operation detection device 600 detects the islanding operation by a passive method for detecting the islanding state by detecting a change in voltage waveform or phase that occurs when the islanding operation is changed to the islanding operation. There is an active method in which a fluctuation factor is given to the device, and when the voltage waveform or phase changes correspondingly, it is detected that the state is in an isolated operation state. Among these, as an active method, an isolated operation detection method using an inter-order harmonic detection method has been developed. The isolated operation detection method of the inter-order harmonic detection method is a harmonic that is not normally included in the power system B, and is a harmonic having a frequency that is a non-integer multiple of the fundamental wave of the power system B (hereinafter referred to as “inter-order harmonics”). In this case, the impedance or admittance of the harmonics of the power system B as viewed from the interconnection point is detected and the islanding operation is detected from the change. is there.

  The islanding operation detection device 600 periodically issues a command to the current injection device 7 to convert a single-phase current of inter-order harmonics (for example, 2.4-order harmonics) between predetermined phases (for example, U-phase) of the power system B. Between V phases). Then, from the current signal input from the current sensor 4 and the voltage signal input from the voltage sensor 5, the signal for the positive phase and the signal for the reverse phase of the interharmonic harmonic are obtained by discrete Fourier transform and symmetrical coordinate transformation. And are extracted respectively. The isolated operation detection device 600 calculates the admittance for the normal phase from the voltage signal and current signal for the normal phase, and calculates the admittance for the reverse phase from the voltage signal and current signal for the reverse phase. Then, when the single operation is detected from the change in the admittance for the positive phase and the single operation is also detected from the change in the admittance for the reverse phase, it is determined that the single operation has been detected. When it is determined that the isolated operation is detected, the isolated operation detection device 600 outputs an open signal to the switch 8 and outputs a stop signal to the inverter control device 3.

JP 2003-250226 A

  However, in the case of the method described above, when extracting the signal for the positive phase and the signal for the negative phase of the inter-order harmonic component from the current signal and the voltage signal, respectively, first, for each coefficient that is expanded in the Fourier series, It is necessary to extract a signal of inter-order harmonic components by using discrete Fourier transform, and further to perform a symmetrical coordinate transformation to extract a signal for the positive phase and a signal for the reverse phase.

  The present invention has been conceived under the circumstances described above, and is capable of extracting a single phase operation signal and a positive phase signal of the injected harmonics by simple processing. Its purpose is to provide a device.

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

  An isolated operation detection device provided by the first aspect of the present invention is an isolated operation detection device that detects an isolated operation of a grid-connected inverter system that is linked to a three-phase AC power system. Current injection instruction means for single-phase injection of a harmonic current of a predetermined angular frequency; voltage signal conversion means for converting the detected three-phase voltage signal into a first voltage signal and a second voltage signal; Current signal conversion means for converting a three-phase current signal into a first current signal and a second current signal, and a first positive-phase divided voltage that is a signal of the predetermined angular frequency included in the first voltage signal A positive phase divided voltage signal extracting means for extracting a signal and a second positive phase divided voltage signal which is a signal of the predetermined angular frequency included in the second voltage signal, and the first voltage signal Inverse phase component of the predetermined angular frequency included A negative phase that extracts a first negative phase voltage signal that is a signal and a second negative phase voltage signal that is a negative phase signal of the predetermined angular frequency included in the second voltage signal, respectively. A divided voltage signal extracting means; a first positive phase divided current signal that is a signal of the predetermined angular frequency included in the first current signal; and a signal of the predetermined angular frequency included in the second current signal. A positive phase current signal extracting means for extracting each second positive phase current signal; and a first negative phase signal that is a negative phase signal of the predetermined angular frequency included in the first current signal. An anti-phase component current signal extracting means for extracting an anti-phase component signal and a second anti-phase component signal that is an anti-phase signal of the predetermined angular frequency included in the second current signal; A first positive phase voltage signal, a second positive phase voltage signal, and the first positive phase voltage signal; A positive-phase component circuit constant calculation means for calculating a positive-phase component circuit constant from the current signal and the second positive-phase component current signal; the first negative-phase component voltage signal and the second inverse component; A negative-phase component network circuit constant calculating means for calculating a negative-phase system circuit constant from the phase-divided voltage signal, the first negative-phase component current signal, and the second negative-phase component current signal; A single operation determination means for determining a single operation based on a change in the system circuit constant of the phase and the system circuit constant of the negative phase, the positive phase divided voltage signal extraction means, the negative phase division voltage signal The extraction means, the positive-phase current signal extraction means, and the negative-phase current signal extraction means each extract each signal using a complex coefficient filter.

  In a preferred embodiment of the present invention, the complex coefficient used by the positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, or the negative phase divided current signal extracting means. The filter 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 used by the positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, or the negative phase divided current signal extracting means. The filter 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 positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, or the negative phase divided current signal extracting means includes a plurality of A filter in which complex coefficient filters are connected in multiple stages is used.

  In a preferred embodiment of the present invention, the predetermined angular frequency is a non-integer multiple angular frequency of the fundamental wave of the power system.

  In a preferred embodiment of the present invention, the islanding determination means can determine that the islanding operation is based on a change in the system circuit constant for the positive phase and based on a change in the system circuit constant for the reverse phase. Only when it can be determined as an isolated operation, it is determined as an isolated operation.

  In a preferred embodiment of the present invention, the current injection instructing unit instructs the grid interconnection inverter system to inject a harmonic current having the predetermined angular frequency.

  In a preferred embodiment of the present invention, the system circuit constant is an absolute value of admittance.

  The grid interconnection inverter system provided by the second aspect of the present invention includes the islanding operation detection apparatus provided by the first aspect of the present invention.

  An islanding operation detection method provided by the third aspect of the present invention is an islanding operation detection method for detecting islanding operation of a grid-connected inverter system linked to a three-phase AC power system. A first step of single-phase injection of a harmonic current of a predetermined angular frequency; a second step of converting the detected three-phase voltage signal into a first voltage signal and a second voltage signal; A third step of converting a three-phase current signal into a first current signal and a second current signal, and a first positive phase divided voltage that is a signal of the predetermined angular frequency included in the first voltage signal A fourth step of extracting a signal and a second positive phase divided voltage signal which is a signal of the predetermined angular frequency included in the second voltage signal, and the first voltage signal includes the first step. A first negative phase voltage signal that is a negative phase signal of a predetermined angular frequency. And a fifth step of extracting a second negative phase voltage signal that is a negative phase signal of the predetermined angular frequency included in the second voltage signal, and the first current signal A first positive-phase current signal that is a signal of the predetermined angular frequency included and a second positive-phase current signal that is a signal of the predetermined angular frequency included in the second current signal are respectively extracted. A sixth phase step, a first negative phase current signal that is a negative phase signal of the predetermined angular frequency included in the first current signal, and the predetermined angle included in the second current signal. A seventh step of extracting a second negative phase current signal that is a negative phase signal of the frequency, respectively, the first positive phase voltage signal and the second positive phase voltage signal; From the first positive-phase current signal and the second positive-phase current signal, system circuit constants for the positive phase From the eighth step of calculating, the first negative phase voltage signal and the second negative phase voltage signal, the first negative phase current signal and the second negative phase current signal A ninth step of calculating a system circuit constant for the reverse phase, and a ninth step of detecting an isolated operation based on a change in the system circuit constant for the positive phase and the system circuit constant of the reverse phase. In the fourth to seventh steps, each signal is extracted using a complex coefficient filter.

  According to the present invention, the complex phase filter extracts the positive-phase component and the negative-phase component of the predetermined angular frequency from each voltage signal and each current signal, respectively, and uses the extracted positive-phase component signals for the positive phase. The system circuit constants for the phase are calculated, and the system circuit constants for the antiphase are calculated using the extracted signals for the antiphase. Then, the isolated operation is detected based on the change in the calculated system circuit constant for the positive phase and the system circuit constant for the reverse phase. Since the complex coefficient filter is used, it is possible to extract the signals for the positive phase and the negative phase having a predetermined angular frequency by simple processing.

  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 isolated operation 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 block diagram for demonstrating the internal structure of the positive phase divided voltage signal extraction part which concerns on 2nd Embodiment. It is a figure which shows the frequency characteristic of the part for the positive phase (reverse phase) voltage signal extraction part which concerns on 2nd Embodiment. It is a block diagram for demonstrating the grid connection inverter system provided with the conventional isolated operation detection apparatus.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, taking as an example a case where the isolated operation detection 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 device 2, an inverter control device 3, a current sensor 4, a voltage sensor 5, an isolated operation detection device 6, a current injection device 7, and a switch. 8 is provided. The DC power source 1 is connected to the inverter device 2. The inverter device 2 is connected to a three-phase AC power system B via an output line of U-phase, V-phase, and W-phase output voltages via a switch 8. The current sensor 4 and the voltage sensor 5 are installed on the output side of the inverter device 2. The inverter control device 3 is connected to the inverter device 2. The grid interconnection inverter system A converts the DC power output from the DC power supply 1 into AC power and supplies the power grid B and the load C. In addition, the structure of the grid connection inverter system A is not restricted to this. For example, other sensors necessary for controlling the inverter device 2 may be provided.

  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 device 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 device 2 converts a DC voltage input from the DC power source 1 into an AC voltage and outputs the AC voltage to the load C and the power system B. The inverter device 2 includes a PWM control type three-phase inverter circuit including three sets and six switching elements (not shown). The inverter circuit converts the DC voltage input from the DC power source 1 into an AC voltage by switching each switching element on and off based on the PWM signal input from the inverter control device 3. Further, the inverter device 2 removes a high-frequency component due to switching by a built-in filter circuit (not shown), and boosts or steps down the AC voltage to a level substantially equal to the system voltage by a built-in transformer circuit. In addition, the structure of the inverter apparatus 2 is not restricted to this. For example, the inverter circuit may be a multi-level inverter circuit. Also, a so-called transformer-less system without a transformer circuit may be used. Further, a DC / DC converter circuit may be provided between the DC power source 1 and the inverter device 2.

  The inverter control device 3 controls the inverter device 2 and is realized by, for example, a microcomputer. The inverter control device 3 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 4 and the voltage signal V input from the voltage sensor 5. 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 device 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 device 3 includes a command value signal generation unit 31 and a PWM signal generation unit 32.

  The command value signal generator 31 receives the current signal I from the current sensor 4 and the voltage signal V from the voltage sensor 5 to control the output power and the output current of the grid-connected inverter system A. A compensation signal is generated, and a command value signal is generated based on the compensation signal. The generated command value signal is output to the PWM signal generation unit 32. A description of each control and the command value signal generation method is omitted.

  The PWM signal generation unit 32 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 device 2. Moreover, the PWM signal generation part 32 stops the production | generation of a PWM signal, when the isolated operation detection signal (stop signal) is input from the isolated operation detection apparatus 6. FIG. Thereby, the power conversion operation of the inverter device 2 is stopped.

  The current sensor 4 detects a current flowing through each phase at a connection point with the power system B (that is, an output current of the system connection inverter system A). The detected current signal I (Iu, Iv, Iw) is input to the inverter control device 3 and the isolated operation detection device 6. The voltage sensor 5 detects the voltage of each phase at the connection point with the power system B. The detected voltage signal V (Vu, Vv, Vw) is input to the inverter control device 3 and the independent operation detection device 6. Note that, when the grid-connected inverter system A is linked to the power grid B, the voltage at the grid point substantially matches the grid voltage.

  The isolated operation detection device 6 detects an isolated operation, and is realized by, for example, a microcomputer. The islanding operation detection device 6 periodically outputs a current injection instruction signal to the current injection device 7, and causes the current injection device 7 to inject a current of interharmonics into the power system B. The isolated operation detection device 6 detects an isolated operation based on the voltage signal and the current signal detected when the current injection device 7 injects a current of interharmonic harmonics. Details of the detection method of the isolated operation will be described later. The isolated operation detection device 6 outputs an isolated operation detection signal when an isolated operation is detected. The isolated operation detection signal output from the isolated operation detection device 6 is input to the PWM signal generation unit 32 of the inverter control device 3 as a stop signal and input to the switch 8 as an open signal.

  The current injection device 7 injects a single-phase current of inter-order harmonics into the power system B, and is configured by an inverter circuit, a transformer, and the like. The current injection device 7 injects a single-phase current of inter-order harmonics between predetermined phases (for example, between the U phase and the V phase) of the power system B in response to the instruction signal input from the isolated operation detection device 6. In the present embodiment, for example, 2.4 order harmonics are used as interharmonics to be injected.

  The switch 8 disconnects the connection between the grid-connected inverter system A and the load C. The switch 8 disconnects the connection between the grid-connected inverter system A and the load C when an isolated operation detection signal (open signal) is input from the isolated operation detection device 6. Thereby, the independent operation state of the grid connection inverter system A is avoided.

  Next, details of the isolated operation detection device 6 will be described with reference to FIGS.

  FIG. 2 is a block diagram for explaining the internal configuration of the isolated operation detection device 6.

  As shown in the figure, the isolated operation detection device 6 includes a voltage signal three-phase / two-phase converter 61, a positive-phase divided voltage signal extractor 62a, a reverse-phase divided voltage signal extractor 62b, a current signal three-phase / two-phase. A conversion unit 63, a positive phase component current signal extraction unit 64a, a negative phase component current signal extraction unit 64b, a positive phase component system circuit constant calculation unit 65, a negative phase component system circuit constant calculation unit 66, an isolated operation determination unit 67, and A determination instruction unit 68 is provided. Since the present invention relates to an active type isolated operation detection method, only the configuration for detecting the active type isolated operation is described. Actually, the isolated operation detection device 6 also includes a configuration for passive isolated operation detection, but the description and explanation thereof are omitted in the present embodiment.

  The voltage signal three-phase / two-phase converter 61 converts the three voltage signals Vu, Vv, Vw input from the voltage sensor 5 into an α-axis voltage signal Vα and a β-axis voltage signal Vβ. The voltage signal three-phase / two-phase conversion unit 61 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 converter 61 is expressed by a determinant represented by the following equation (1).

  The positive phase divided voltage signal extraction unit 62a extracts the positive phase signal of the inter-order harmonics 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 61. It has a complex coefficient bandpass filter (bandpass type 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 (2). In the following equation (2), 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 (2). As shown in the figure, the complex-coefficient bandpass filter is configured by a circuit that multiplies the denominator calculation process of equation (2) 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] (3)
y [k] = (1-r) .x [k] (4)
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 (3) and (4) 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] ··· (5)
x _j [k] = r · cos (Ω _d ) · x _j [k−1] + r · sin (Ω _d ) · x _r [k−1] + u _j [k] (6)
y _r [k] = (1−r) · x _r [k] (7)
y _j [k] = (1−r) · x _j [k] (8)
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 (5) to (8). 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 (5), respectively. The adder 12g is the first term and the second term of the equation (5). An arithmetic unit that adds the second term and the third term. Therefore, the real part x _r [k] of the state data shown by the above equation (5) 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 (6), respectively, and the adder 12h is the first term, the second term, and the third term of the above equation (6). It is an arithmetic unit that adds terms. Therefore, the imaginary part x _j [k] of the state data indicated by the above equation (6) is output from the adder 12h. The multipliers 12e and 12f are arithmetic units for calculating the expressions (7) and (8), respectively.

In the present embodiment, the voltage signal three-phase / two-phase converter 61 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 (5) and (7). 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 (6) and (8). 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 (2) 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 62a is a signal for the positive phase of the injected interharmonic harmonics from the α axis voltage signal Vα and β axis voltage signal Vβ input from the voltage signal three-phase / two-phase conversion unit 61. Is extracted. The extracted positive phase divided voltage signals Vαp and Vβp are output to the positive phase divided system circuit constant calculation unit 65. A normalized angular frequency obtained by normalizing the angular frequency of the inter-order harmonics injected into the power system B 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 62a. Is preset. When the injected interharmonic harmonic is a 2.4 harmonic, the angular frequency ω ₀ (for example, ω ₀ = 120π [rad / sec] (60 [Hz])) of the fundamental wave (positive phase) of the system voltage If the normalized angular frequency obtained by normalizing ω is ω _d , 2.4ω _d is preset. The positive phase divided voltage signal extraction unit 62a 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 Vαp and Vβp.

FIG. 5A is a diagram illustrating frequency characteristics of a complex coefficient bandpass filter included in the positive phase divided voltage signal extraction unit 62a. Since the center angular frequency of the passband is the 2.4-order harmonic angular frequency of 2.4ω ₀ , signals of other angular frequencies are preferably removed, and only the signal of the positive phase of the 2.4-order harmonic is included. Can be extracted.

The negative phase voltage signal extracting unit 62b is a signal for the negative phase of the interharmonics injected from the α-axis voltage signal Vα and β-axis voltage signal Vβ input from the voltage signal three-phase / two-phase converter 61. Is extracted. The extracted negative phase divided voltage signals Vαn and Vβn are output to the negative phase divided system circuit constant calculation unit 66. As the normalized angular frequency Ω _d that determines the pass band of the complex coefficient band pass filter included in the negative phase voltage signal extraction unit 62b, the angular frequency of the negative phase of the inter-order harmonics injected into the power system B is normalized. A normalized angular frequency 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, “−2.4ω _d ” obtained by normalizing “−2.4ω ₀ ”, which is a negative value of the angular frequency 2.4ω _{0 for} the positive phase, is set as the normalized angular frequency Ω _d . The negative phase voltage signal extraction unit 62b 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 antiphase voltage signals Vαn and Vβn.

FIG. 5B is a diagram illustrating frequency characteristics of a complex coefficient bandpass filter included in the negative phase divided voltage signal extraction unit 62b. Since the central angular frequency of the pass band is the angular frequency “−2.4ω ₀ ” of the reverse phase of the 2.4 th harmonic, signals of other angular frequencies are preferably removed and the 2.4 th harmonic is removed. It is possible to extract only the signal of the opposite phase.

  Note that the complex coefficient bandpass filter provided in the positive phase divided voltage signal extraction unit 62a and the negative phase divided voltage signal extraction unit 62b is not limited to the one having the transfer function H (z) shown in the above equation (2). 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 current signal three-phase / two-phase converter 63 converts the three current signals Iu, Iv, Iw input from the current sensor 4 into an α-axis current signal Iα and a β-axis current signal Iβ. The current signal three-phase / two-phase conversion unit 63 performs a so-called three-phase / two-phase conversion process (αβ conversion process). The current signals Iu, Iv, and Iw are converted into an α-axis component and a β-axis component that are 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 63 is represented by a determinant represented by the following equation (9).

The positive phase current signal extraction unit 64a is a signal for the positive phase of the injected interharmonic harmonics 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 63. And a complex coefficient band pass filter similar to that of the positive phase divided voltage signal extraction unit 62a. The extracted positive-phase current signals Iαp and Iβp are output to the positive-phase current system circuit constant calculation unit 65. Similarly to the positive phase component voltage signal extraction unit 62a, the normalized angular frequency 2.4ω _d is also applied to the normalized angular frequency Ω _d that determines the pass band of the complex coefficient band pass filter included in the positive phase current signal extraction unit 64a. It is set in advance. The positive-phase current signal extraction unit 64a 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 Iαp and Iβp. The frequency characteristic of the complex coefficient bandpass filter provided in the positive phase current signal extraction unit 64a also exhibits the characteristic shown in FIG. 5A. Therefore, signals having angular frequencies other than the angular frequency 2.4ω ₀ are preferably removed, Only the positive phase signal of the 4th harmonic can be extracted.

The negative phase current signal extraction unit 64b is a signal for the negative phase of the inter-order harmonics injected 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 63. And a complex coefficient bandpass filter similar to that of the negative phase divided voltage signal extraction unit 62b. The extracted negative phase current signals Iαn and Iβn are output to the negative phase system circuit constant calculation unit 66. Similarly to the anti-phase component voltage signal extraction unit 62b, the normalized angular frequency “−2.4ω” is also applied to the normalized angular frequency Ω _d that determines the pass band of the complex coefficient band pass filter included in the anti-phase component current signal extraction unit 64b. _d ”is preset. The negative phase current signal extraction unit 64b 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 antiphase current signals Iαn and Iβn. Since the frequency characteristic of the complex coefficient bandpass filter provided in the negative phase current signal extraction unit 64b also exhibits the characteristic of FIG. 5B, signals of angular frequencies other than the angular frequency “−2.4ω ₀ ” are preferably removed. Thus, it is possible to extract only the signal of the reverse phase of the 2.4th harmonic.

  Note that the complex coefficient band-pass filter included in the positive-phase component current signal extraction unit 64a and the negative-phase component current signal extraction unit 64b is not limited to that of the transfer function H (z) shown in the above equation (2). 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 positive phase system circuit constant calculation unit 65 calculates system circuit constants for the positive phase. In this embodiment, the absolute value of admittance is calculated as the system circuit constant for the positive phase. The positive phase distribution system circuit constant calculation unit 65 includes the positive phase divided voltage signals Vαp and Vβp input from the positive phase divided voltage signal extraction unit 62a and the positive phase divided current signal input from the positive phase divided current signal extraction unit 64a. The absolute value Yp of the admittance for the positive phase is calculated from Iαp and Iβp by the following equation (10). The calculated absolute value Yp of the admittance for the positive phase is output to the isolated operation determination unit 67.

The anti-phase system circuit constant calculation unit 66 calculates system circuit constants for the anti-phase. In this embodiment, the absolute value of the admittance is calculated as the system circuit constant for the reverse phase. The negative-phase component system circuit constant calculation unit 66 includes the negative-phase divided voltage signals Vαn and Vβn input from the negative-phase divided voltage signal extraction unit 62b and the negative-phase divided current signal input from the negative-phase divided current signal extraction unit 64b. From Iαn and Iβn, the absolute value Yn of the admittance for the reverse phase is calculated by the following equation (11). The calculated absolute value Yn of the reversed phase admittance is output to the isolated operation determination unit 67.

  The isolated operation determination unit 67 determines whether or not the grid interconnection inverter system A is in an isolated operation state. The isolated operation determination unit 67 performs determination when a determination instruction signal is input from the determination instruction unit 68, and outputs an isolated operation detection signal when it is determined that the vehicle is in the isolated operation state. The isolated operation determination unit 67 has a positive phase admittance absolute value Yp input from the normal phase distribution system circuit constant calculation unit 65 smaller than a predetermined value set in advance and a reverse phase distribution system circuit constant calculation unit 66. When the absolute value Yn of the admittance for the reverse phase calculated by is smaller than a predetermined value set in advance, it is determined that the vehicle is in the single operation state.

  The absolute value Yp of the admittance for the positive phase calculated by the positive phase system circuit constant calculation unit 65 is the magnitude of the admittance for the positive phase with respect to the injected inter-order harmonics of the power system B viewed from the interconnection point. Show. The absolute value Yn of the antiphase admittance calculated by the antiphase system network circuit constant calculation unit 66 is the magnitude of the admittance of the antiphase for the injected inter-order harmonics of the power system B viewed from the interconnection point. It shows. The absolute value of the admittance of the electric power system B viewed from the connection point when the system connection inverter system A is in the single operation state is smaller than that in the connection state. Accordingly, when the detected absolute value of the admittance becomes smaller than a predetermined value set in advance, it can be determined that the vehicle is in the single operation state. Injecting a single-phase current between the phases of the three-phase AC power system B is equivalent to injecting a positive-phase and a reverse-phase three-phase current of the same magnitude at the same time. In the present embodiment, by performing a double determination of the determination based on the absolute value of the admittance for the positive phase of the inter-order harmonic and the determination based on the absolute value of the admittance for the reverse phase, it is possible to prevent erroneous detection. Yes.

  Note that the method for determining the isolated operation state is not limited to that described above. In addition to the determination method described above, a determination based on the difference between the absolute value Yp of the admittance for the normal phase and the absolute value Yn of the admittance for the reverse phase may be added. In the determination, the absolute value Yp of the admittance for the positive phase and the absolute value Yn of the admittance for the reverse phase are substantially equal during normal operation, and the absolute value Yp of the admittance for the positive phase and the admittance of the reverse phase during system transient. The fact that the absolute value Yn is different is used. Further, when it is determined that the single operation is performed by either the determination based on the absolute value Yp of the admittance for the normal phase or the determination based on the absolute value Yn of the admittance for the reverse phase, it may be determined that the state is the single operation. Alternatively, it may be determined that the vehicle is in the single operation state only by the determination based on the absolute value Yp of the admittance for the positive phase. Moreover, you may make it determine combining each determination mentioned above.

  The system circuit constants calculated by the normal phase system circuit constant calculation unit 65 and the reverse phase system circuit constant calculation unit 66 are not limited to the absolute value of admittance but may be the absolute value of impedance. In this case, the isolated operation determination unit 67 may determine whether or not the calculated absolute value of the impedance is greater than a predetermined value set in advance.

  The determination instruction unit 68 instructs determination of the single operation state, periodically outputs a current injection instruction signal to the current injection device 7, and sends a determination instruction signal to the single operation determination unit 67. Output. Instead of providing the determination instruction unit 68, the current injection device 7 may periodically inject current, and the isolated operation determination unit 67 may perform determination in synchronization therewith. Further, the inverter device 2 may inject a single-phase current of inter-order harmonics without providing the current injection device 7. In this case, the determination instruction unit 68 periodically outputs a current injection instruction signal to the command value signal generation unit 31 of the inverter control device 3, and the command value signal generation unit 31 superimposes the inter-order harmonics to generate the command value. A signal may be generated.

  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. Then, by the complex coefficient band pass filter, the injected inter-order harmonic positive phase divided voltage signals Vαp, Vβp and negative phase divided voltage signals Vαn, Vβn are extracted from the α axis voltage signal Vα and the β axis voltage signal Vβ, respectively. Then, from the α-axis current signal Iα and the β-axis current signal Iβ, the positive-phase component current signals Iαp and Iβp and the negative-phase component current signals Iαn and Iβn of the inter-order harmonics are extracted, respectively. Then, the absolute value Yp of the admittance for the normal phase and the absolute value Yn of the admittance for the reverse phase are calculated from the extracted signal, and the isolated operation is determined based on this. Since the complex coefficient bandpass filter is used, the signals for the positive and negative phases of the inter-order harmonic can be extracted by simple processing.

  In the first embodiment, the case where the signal for the positive phase and the signal for the negative phase of the inter-order harmonic is extracted using the complex coefficient bandpass filter has been described. However, the complex coefficient notch filter (band rejection type) These signals may be extracted using a complex coefficient filter. 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 isolated operation detection device according to the second embodiment is the same as that of the isolated operation detection device 6 according to the first embodiment shown in FIG. The negative phase component voltage signal extraction unit 62b, the positive phase component current signal extraction unit 64a, and the negative phase component current signal extraction unit 64b each include a plurality of complex coefficient notch filters. (Refer to FIG. 8 to be described later), and it is changed to a negative phase component voltage signal extraction unit 62b ′, a positive phase component current signal extraction unit 64a ′, and a negative phase component current signal extraction unit 64b ′. (Other than the voltage signal extraction unit 62a 'is not shown). The positive phase component voltage signal extraction unit 62a ′, the negative phase component voltage signal extraction unit 62b ′, the positive phase component current signal extraction unit 64a ′, and the negative phase component current signal extraction unit 64b ′ pass components other than the components to be extracted. The desired component is extracted by suppressing.

The complex coefficient notch filter included in the positive phase divided voltage signal extracting unit 62a ′, the negative phase divided voltage signal extracting unit 62b ′, the positive phase divided current signal extracting unit 64a ′, and the negative phase divided current signal extracting unit 64b ′ is a z-transform. The transfer function H (z) by expression is composed of a first-order IIR filter having a complex coefficient expressed by the following equation (12). In the following equation (12), 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 (12). 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].

  FIG. 8 is a block diagram for explaining the internal configuration of the positive phase divided voltage signal extraction unit 62a '.

The positive phase divided voltage signal extraction unit 62a ′ illustrated in FIG. 8 includes a filter in which six complex coefficient notch filters NF1 to NF6 are connected in multiple stages. As the normalized angular frequency Ω _d for determining the stop band of the complex coefficient notch filter NF1, “ω _d ” obtained by normalizing the angular frequency “ω ₀ ” of the positive phase of the fundamental wave of the system voltage is set in advance. Complex coefficient notch filter NF1 is input to the complex coefficient notch filter as α input shaft voltage signal Vα and β-axis voltage signal Vβ data u _r [k] and u _j [k], the output data e _r [k] and e _j [k] is output to the complex coefficient notch filter NF2. The complex coefficient notch filter NF1 suppresses and outputs a signal corresponding to the positive phase of the fundamental wave out of the α-axis voltage signal Vα and the β-axis voltage signal Vβ. Similarly, the complex coefficient notch filters NF2 to NF6 respectively have a negative phase component of the fundamental wave, a negative phase component of the 2.4th harmonic, a fifth harmonic (positive phase component), and a seventh harmonic (positive phase component). , For suppressing the 11th harmonic (positive phase). “−ω _d ”, “−2.4ω _d ”, “−5ω _d ”, “7ω _d ”, “−11ω” are respectively used as the normalized angular frequencies Ω _d that determine the stop bands of the complex coefficient notch filters NF 2 to NF 6. _d ”is preset.

FIG. 9A is a diagram illustrating the frequency characteristics of the positive phase divided voltage signal extraction unit 62a ′. According to the figure, the fundamental wave component (angular frequency “ω ₀ ”), the anti-phase component of the fundamental wave (angular frequency “−ω ₀ ”), and the anti-phase component of the fourth harmonic (angular frequency “−2. 4ω ₀ ”), the fifth harmonic component (angular frequency“ −5ω ₀ ”), the seventh harmonic component (angular frequency“ 7ω ₀ ”), and the eleventh harmonic component (angular frequency“ −11ω ₀ ”) are suppressed. The other components (the positive phase component of the 2.4th harmonic) are passed. Therefore, the positive phase divided voltage signal extraction unit 62a ′ can suitably pass only the positive phase component of the 2.4th harmonic, and the 2.4th harmonic from the α axis voltage signal Vα and the β axis voltage signal Vβ. The positive phase divided voltage signals Vαp and Vβp obtained by extracting only the positive phase component of the wave are output.

In general, since the harmonics superimposed on the power system B are many fifth, seventh, and eleventh harmonics, in this embodiment, the positive and negative phase components of these and the fundamental wave, and injection The negative phase component of the 2.4th harmonic is suppressed. In addition, what is necessary is just to design positive phase divided voltage signal extraction part 62a '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 NF1 to NF4, and when it is desired to suppress the thirteenth harmonic as well, the stopband is determined. A complex coefficient notch filter in which “13ω _d ” is set as the angular frequency Ω _d may be further provided.

The negative phase divided voltage signal extraction unit 62b ′ also includes a filter in which six complex coefficient notch filters NF1 to NF6 are connected in multiple stages. In the negative phase divided voltage signal extraction unit 62b ′, the angular frequency “2.4ω ₀ ” of the positive phase of the 2.4th harmonic is used as the normalized angular frequency Ω _d that determines the stop band of the complex coefficient notch filter NF3. Is different from the positive phase divided voltage signal extraction unit 62a ′ (see FIG. 8) in that “2.4ω _d ” is set.

FIG. 9B is a diagram illustrating the frequency characteristics of the negative phase divided voltage signal extraction unit 62b ′. According to the figure, the fundamental wave component (angular frequency “ω ₀ ”), the negative phase component of the fundamental wave (angular frequency “−ω ₀ ”), and the positive phase component of the fourth harmonic (angular frequency “2.4ω). ₀ ”), the fifth harmonic component (angular frequency“ −5ω ₀ ”), the seventh harmonic component (angular frequency“ 7ω ₀ ”), and the eleventh harmonic component (angular frequency“ −11ω ₀ ”) are suppressed. , And other components (the reverse phase component of the 2.4th harmonic) are passed. Therefore, the negative phase divided voltage signal extraction unit 62b ′ can suitably pass only the negative phase component of the 2.4th order harmonic, and the 2.4th order harmonic can be obtained from the α axis voltage signal Vα and the β axis voltage signal Vβ. The negative phase voltage signals Vαn and Vβn obtained by extracting only the negative phase component of the wave are output.

  The positive phase component current signal extraction unit 64a 'includes the same filter as the positive phase component voltage signal extraction unit 62a'. Since the frequency characteristics of the positive phase current signal extraction unit 64a ′ also have the characteristics shown in FIG. 9A, the fundamental wave component, the antiphase component of the fundamental wave, the antiphase component of the 2.4th harmonic, and the fifth harmonic. The component, the seventh harmonic component, and the eleventh harmonic component are suppressed, and the other components (the positive phase component of the 2.4 harmonic) are passed. Therefore, only the positive phase component of the 2.4th harmonic can be suitably passed, and only the positive phase component of the 2.4th harmonic is extracted from the α-axis current signal Iα and the β-axis current signal Iβ. Divided current signals Iαp and Iβp are output.

  The negative-phase component current signal extraction unit 64b 'includes a filter similar to that of the negative-phase component voltage signal extraction unit 62b'. Since the frequency characteristic of the negative phase current signal extraction unit 64b ′ also shows the characteristic shown in FIG. 9B, the fundamental wave component, the negative phase component of the fundamental wave, the positive phase component of the 2.4th harmonic, and the fifth harmonic. The component, the seventh harmonic component, and the eleventh harmonic component are suppressed, and the other components (the reverse phase component of the 2.4 harmonic) are passed. Therefore, only the reverse phase component of the 2.4th harmonic can be suitably passed, and only the reverse phase component of the 2.4th harmonic is extracted from the α axis current signal Iα and the β axis current signal Iβ. The phase split current signals Iαn and Iβn are output.

  The complex coefficient notch filter included in the positive phase divided voltage signal extraction unit 62a ′, the negative phase divided voltage signal extraction unit 62b ′, the positive phase divided current signal extraction unit 64a ′, and the negative phase divided current signal extraction unit 64b ′ is: It is not limited to the transfer function H (z) shown in the above equation (12). 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, the positive phase divided voltage signals Vαp and Vβp, the negative phase divided voltage signals Vαn and Vβn, the positive phase divided current signals Iαp and Iβp, and the negative phase divided current signals Iαn and Iβn can be extracted, respectively. These can be used to determine whether or not an islanding operation is performed. Therefore, the same effect as that of the first embodiment can be obtained.

In the second embodiment, the positive phase divided voltage signal extraction unit 62a ′, the negative phase divided voltage signal extraction unit 62b ′, the positive phase divided current signal extraction unit 64a ′, and the negative phase divided current signal extraction unit 64b ′. It has been described a case where the normalized angular frequency Omega _d of the complex coefficient filter used previously set, but is not limited thereto. When the sampling cycle of signal processing is a fixed sampling cycle, the complex coefficient notch filters NF1, 2, 4 to 6 detect the angular frequency of the fundamental wave of the system voltage with a frequency detection device or the like, and the detected angular frequency is calculated. It may be used after being normalized. Since the angular frequency of the injected inter-order harmonics is fixed, the complex coefficient notch filter NF3 may set a normalized angular frequency based on the angular frequency. Similarly, the normalized angular frequency based on the angular frequency of the injected inter-order harmonics may be set for the complex coefficient bandpass filter in the first embodiment.

  In the first or second embodiment, the positive phase divided voltage signal extracting unit 62a, the negative phase divided voltage signal extracting unit 62b, the positive phase divided current signal extracting unit 64a, and the negative phase divided current using a complex coefficient band pass filter are used. When the signal extraction unit 64b is provided, the positive phase divided voltage signal extraction unit 62a ′, the negative phase divided voltage signal extraction unit 62b ′, the positive phase divided current signal extraction unit 64a ′, and the negative phase divided current using a complex coefficient notch filter. Although the case where the signal extraction unit 64b ′ is provided has been described, the present invention is not limited to this. For example, a positive-phase divided voltage signal extraction unit 62a and a positive-phase divided current signal extraction unit 64a are provided and extracted by passing a positive-phase signal using a complex coefficient bandpass filter, and a negative-phase divided voltage signal extraction unit. 62b 'and a negative phase current signal extraction unit 64b' may be provided, and a negative phase signal may be extracted using a complex coefficient notch filter. In addition, a positive phase divided voltage signal extraction unit 62a is provided to extract the positive phase signal using a complex coefficient band pass filter, and a negative phase divided voltage signal extraction unit 62b is provided to provide a complex coefficient band pass filter. Is extracted by passing the signal for the reverse phase, and the signal for the positive phase is extracted using the complex coefficient notch filter provided with the positive phase current signal extraction unit 64a ′, and the negative phase current signal extraction is performed. The signal may be extracted by using a complex coefficient notch filter with a unit 64b ′.

In the first or second embodiment, a case has been described in which 2.4-order harmonics are injected into the power system B and 2.4-order harmonic components are extracted from the detected voltage signal and current signal. However, the present invention is not limited to this, and harmonics between orders other than the 2.4 order may be used. Moreover, you may make it utilize the harmonic which is not a harmonic between orders. The reason why inter-order harmonics are used is that, by using harmonics that do not substantially exist in the power system B, it is possible to accurately extract even if the injected current is reduced. Therefore, if the amount existing in the electric power system B is a very small harmonic (for example, the 10th harmonic), it can be used instead of the interharmonic harmonic. By setting the normalized angular frequency Ω _d that determines the passband (stopband) of each complex coefficient filter according to the angular frequency of the harmonics used, the signal for the positive phase of the desired harmonics and the negative phase Minute signal can be extracted.

  In the first or second embodiment, the isolated operation detection device according to the present invention has been described as a configuration different from the inverter control device. However, the single operation detection device is included in the inverter control device and realized by a single microcomputer or the like. May be.

  In the said 1st or 2nd embodiment, although the case where the isolated operation detection apparatus which concerns on this invention was used for the grid connection inverter system was demonstrated, it is not restricted to this. The isolated operation detection device according to the present invention can also be used in a grid interconnection device such as a synchronous generator.

  The isolated operation detection device, the grid interconnection inverter system, and the isolated operation detection method according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the isolated operation detection device, the grid interconnection inverter system, and the isolated operation detection 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 device 3 Inverter control device 31 Command value signal generator 32 PWM signal generator 4 Current sensor 5 Voltage sensor 6 Independent operation detector 61 Voltage signal three-phase / two-phase converter (voltage Signal conversion means)
62a, 62a ′ Positive phase divided voltage signal extraction unit NF1 to NF6 Complex coefficient notch filter 62b Negative phase divided voltage signal extraction unit 63 Current signal three-phase / two-phase conversion unit (current signal conversion means)
64a Positive phase current signal extraction unit 64b Reverse phase current signal extraction unit 65 Positive phase system circuit constant calculation unit 66 Reverse phase system circuit constant calculation unit 67 Independent operation determination unit 68 Determination instruction unit (current injection instruction means)
7 Current injection device 8 Switch B Power system C Load D Breaker

Claims (12)

An isolated operation detection device for detecting isolated operation of a grid-connected inverter system linked to a three-phase AC power system,
Current injection instruction means for single-phase injection of harmonic current of a predetermined angular frequency into the power system;
Voltage signal conversion means for converting the detected three-phase voltage signal into a first voltage signal and a second voltage signal;
Current signal conversion means for converting the detected three-phase current signal into a first current signal and a second current signal;
A first positive phase voltage signal that is a signal of the predetermined angular frequency included in the first voltage signal and a second positive phase component that is a signal of the predetermined angular frequency included in the second voltage signal. Positive phase divided voltage signal extracting means for extracting the voltage signals,
A first negative phase voltage signal that is a negative phase signal of the predetermined angular frequency included in the first voltage signal, and a negative phase signal of the predetermined angular frequency that is included in the second voltage signal. A negative phase divided voltage signal extracting means for extracting the second negative phase divided voltage signal,
A first positive phase current signal that is a signal of the predetermined angular frequency included in the first current signal, and a second positive phase component that is a signal of the predetermined angular frequency included in the second current signal. Positive phase current signal extraction means for extracting current signals, respectively;
A first negative phase current signal, which is a negative phase signal of the predetermined angular frequency included in the first current signal, and a negative phase signal of the predetermined angular frequency, which is included in the second current signal. A negative phase component current signal extracting means for extracting a second negative phase component current signal, respectively,
From the first positive phase divided voltage signal and the second positive phase divided voltage signal, and from the first positive phase divided current signal and the second positive phase divided current signal, a system circuit constant for the positive phase is obtained. Positive phase distribution system circuit constant calculation means for calculating
From the first negative phase divided voltage signal and the second negative phase divided voltage signal, and the first negative phase divided current signal and the second negative phase divided current signal, a system circuit constant for the negative phase is obtained. A negative phase distribution system circuit constant calculating means for calculating
Isolated operation determination means for determining isolated operation based on changes in the system circuit constant for the positive phase and the system circuit constant for the reverse phase;
With
The positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, and the negative phase divided current signal extracting means each extract each signal using a complex coefficient filter. ,
An isolated operation detection device.   The complex coefficient filter used by the positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, or the negative phase divided current signal extracting means is a band-pass type complex coefficient filter. The isolated operation detection device according to claim 1, wherein 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 isolated operation detection device according to claim 2, wherein   The complex coefficient filter used by the positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, or the negative phase divided current signal extracting means is a band rejection type complex coefficient filter. The isolated operation detection device according to claim 1, wherein 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 isolated operation detection device according to claim 4, wherein   The positive phase divided voltage signal extracting means, the negative phase divided voltage signal extracting means, the positive phase divided current signal extracting means, or the negative phase divided current signal extracting means is a filter in which a plurality of complex coefficient filters are connected in multiple stages. The isolated operation detection device according to claim 4 or 5, which is used.   The isolated operation detection device according to any one of claims 1 to 6, wherein the predetermined angular frequency is an angular frequency that is a non-integer multiple of a fundamental wave of the power system.   The isolated operation determination means can be determined as isolated operation based on a change in the system circuit constant for the positive phase, and only when it can be determined as isolated operation based on a change in the system circuit constant for the reverse phase. The isolated operation detection device according to claim 1, wherein the isolated operation is determined as isolated operation.   The islanding operation detection device according to any one of claims 1 to 9, wherein the current injection instruction means instructs the grid interconnection inverter system to inject a harmonic current having the predetermined angular frequency.   The isolated operation detection device according to any one of claims 1 to 9, wherein the system circuit constant is an absolute value of admittance.   A grid-connected inverter system comprising the isolated operation detection device according to any one of claims 1 to 10. An isolated operation detection method for detecting isolated operation of a grid-connected inverter system linked to a three-phase AC power system,
A first step of injecting a single-phase harmonic current of a predetermined angular frequency into the power system;
A second step of converting the detected three-phase voltage signal into a first voltage signal and a second voltage signal;
A third step of converting the detected three-phase current signal into a first current signal and a second current signal;
A first positive phase voltage signal that is a signal of the predetermined angular frequency included in the first voltage signal and a second positive phase component that is a signal of the predetermined angular frequency included in the second voltage signal. A fourth step of extracting each of the voltage signals;
A first negative phase voltage signal that is a negative phase signal of the predetermined angular frequency included in the first voltage signal, and a negative phase signal of the predetermined angular frequency that is included in the second voltage signal. A fifth step of extracting the second negative phase divided voltage signal, respectively,
A first positive phase current signal that is a signal of the predetermined angular frequency included in the first current signal, and a second positive phase component that is a signal of the predetermined angular frequency included in the second current signal. A sixth step of extracting current signals respectively;
A first negative phase current signal, which is a negative phase signal of the predetermined angular frequency included in the first current signal, and a negative phase signal of the predetermined angular frequency, which is included in the second current signal. And a second step of extracting the second negative phase current signal, respectively,
From the first positive phase divided voltage signal and the second positive phase divided voltage signal, and from the first positive phase divided current signal and the second positive phase divided current signal, a system circuit constant for the positive phase is obtained. An eighth step of calculating
From the first negative phase divided voltage signal and the second negative phase divided voltage signal, and the first negative phase divided current signal and the second negative phase divided current signal, a system circuit constant for the negative phase is obtained. A ninth step of calculating
A ninth step of detecting an isolated operation based on a change in the system circuit constant for the positive phase and the system circuit constant for the reverse phase;
With
In the fourth to seventh steps, each signal is extracted using a complex coefficient filter.
An isolated operation detection method characterized by the above.

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