JP2008245349A - Systematically interconnecting inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the divergence of a feedback control system by adjusting the phase of harmonics to be controlled in the feedback control system. <P>SOLUTION: This systematically interconnecting inverter device of this invention is installed between solar cells and an electric power system to supply electric power to the electric power system by converting DC power supplied from the solar cells into AC power of system frequency. This device comprises a divergence determination portion 41, which determines whether the feedback control system is in the tendency of divergence or not based on a level extracted from a dq conversion portion 32, and a phase adjustment portion 43, which, when the divergence determination portion 41 determines during the control in the feedback system that the feedback control system is in the tendency of divergence, stops the control in the feedback control system and changes the prescribed phase in an inverted dq conversion portion 36 to a different phase. The prescribed phase in the inverted dq conversion portion 36 is replaced with the phase changed by the phase adjustment portion 43 to start a control in the feedback control system. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a grid-connected inverter device that is provided between a DC power source and a power system, converts DC power supplied from the DC power source into AC power, and supplies the AC power to the power system.

  Conventionally, as a grid interconnection inverter device, for example, there is one described in Patent Document 1 filed by the applicant of the present application. As shown in FIG. 7, this grid-connected inverter device is connected between a DC power source 51 that is, for example, a solar cell and a power system 52, and includes an inverter unit 53, an LC filter unit 54, a grid unit 55, a first unit. Current sensor 56, second current sensor 57, drive circuit 58 and inverter control circuit 59.

Japanese Patent Laid-Open No. 2001-16867

  The inverter unit 53, the LC filter unit 54, and the interconnection unit 55 are connected in series, the first current sensor 57 is provided between the inverter unit 53 and the LC filter unit 54, and the second current sensor 58 is The LC filter unit 54 and the interconnection unit 55 are provided. The inverter control circuit 59 is connected to the drive circuit 58, and the drive circuit 58 is connected to the inverter unit 53.

  The first current sensor 56 and the second current sensor 57 are connected to the inverter control circuit 59. The inverter control circuit 59 includes a filter output distortion extraction control unit 60 and an inverter output current control unit 61. The filter output distortion extraction control unit 60 includes a distortion component extraction unit 62, a distortion threshold value creation unit 63, a first subtracter 64, and a filter output distortion control unit 65. The inverter output current control unit 61 includes an inverter output current fundamental wave component creation unit 66, a first adder 67, a second subtracter 68, and an inverter output current control unit main body 69.

  In this grid-connected inverter device, the DC (DC voltage and DC current) supplied from the DC power supply 51 is converted into AC (AC voltage and AC DC) by the inverter unit 53. The alternating current output from the inverter unit 53 is detected by the first current sensor 56 and input to the inverter output current control unit 61. Further, the switching noise component is removed from the AC voltage output from the inverter unit 53 by the LC filter unit 54. The alternating current from which the switching noise component has been removed is detected by the second current sensor 57 and input to the filter output distortion extraction control unit 60.

  The filter output distortion extraction control unit 60 performs the following processing by digital arithmetic processing at a predetermined cycle. First, the level of harmonics that cause distortion is extracted for each harmonic from the alternating current detected by the second current sensor 57 by the distortion component extraction unit 62. Further, the first subtracter 64 calculates the deviation between the harmonic level and the threshold value created by the distortion threshold value creation unit 63, and this deviation is input to the filter output distortion control unit 65. In the filter output distortion control unit 65, the deviation and the predetermined phase set in advance for each harmonic (the phase in which the harmonic distortion of the alternating current detected by the second current sensor 57 is most suppressed) are described above. An output current distortion compensation command for making the deviation of the output zero is generated. This output current distortion compensation command is input to the inverter output current control unit 61.

  In the inverter output current control unit 61, a fundamental wave component of the inverter output current (system frequency component, 60 Hz or 50 Hz in Japan) is created by the inverter output current fundamental wave component creation unit 66, and the fundamental wave component of this inverter output current is The first adder 67 adds the output current distortion compensation command from the filter output distortion extraction control unit. Further, a deviation between the command of the inverter output current output from the first adder 67 by the second subtracter 68 and the alternating current detected by the first current sensor 56 is calculated, and this deviation is the inverter output current control unit main body. 69. The inverter output current control unit main body 69 generates an inverter output voltage correction signal whose deviation is zero and outputs it to the drive circuit 58.

  The drive circuit 58 generates a drive signal based on the inverter output voltage correction signal, and this drive signal is input to the inverter unit 53. The inverter unit 53 is controlled by a drive signal based on the inverter output voltage correction signal.

  As described above, in the grid-connected inverter device, the feedback control system is configured by the filter output distortion extraction control unit 60 and the inverter output current control unit 61, and the AC voltage and AC current supplied to the power system 52 by this feedback control system. Are controlled so as to satisfy the standards (guidelines that define allowable conditions for frequency, phase, waveform distortion, etc.).

  Harmonic distortion suppression control in the feedback control system of the above grid-connected inverter device creates an output current distortion compensation command for each harmonic order to suppress harmonics that cause harmonic distortion, and outputs the output By adding the current distortion compensation command to the output current command to the inverter unit 53, when the alternating current output from the inverter unit 53 is supplied from the LC filter unit 54 to the power system 52, the harmonics included in the alternating current are included. This suppresses the wave component (a harmonic component generated by distortion of the system voltage and flowing into the capacitor constituting the LC filter unit 54).

  In the harmonic distortion suppression control in the feedback control system, the harmonics for generating the output current distortion compensation command are matched with the harmonics included in the alternating current detected by the second current sensor 57 as much as possible. This is very important. That is, it is necessary to accurately acquire information on the level and phase of the harmonic that is desired to be suppressed, and generate a harmonic that actually flows between the LC filter unit 54 and the power system 52.

  However, in the above-described grid-connected inverter device, only the harmonic level is extracted in real time from the alternating current detected by the second current sensor 57, and the phase of the harmonic is fixed to a predetermined value obtained in advance by experience. Although the fixed value can be adjusted, it is not detected in real time.

  Therefore, in the above-described grid-connected inverter device, the load condition when the power system 52 side is viewed from the inverter unit 53 is relatively stable, and the harmonic distortion is effectively reduced when the change in the phase of the harmonic is small. For example, if the predetermined phase set for each harmonic in the filter output distortion control unit 65 is not appropriate, unlike the case where the load condition of the power system 52 is assumed, harmonic distortion is effective. Can not be suppressed to a problem. In particular, when the harmonic phase is reversed, the harmonic distortion suppression control in the feedback control system becomes the positive feedback control, which works in the direction of divergence, and there is a possibility that the control becomes impossible.

In FIG. 8, the power system 52 is considered as an inductance load for the grid-connected inverter device (in FIG. 8, the inductance is indicated by L ₂ ). A case where the inductance L ₂ affects the resonance frequency f ₀ of the LC filter unit 54 can be considered.

That is, the value of the inductance L ₂ of the power system 52 varies depending on the power system 52 to which the grid-connected inverter device is connected, and also changes in the operating state of the power system 52. As shown in FIG. 8, when the inductance of the LC filter unit 54 is L ₁ and the capacitance is C ₁ , the resonance frequency f ₀ of the LC filter unit 54 is f ₀ = 1 / (2 · π · √ (L ₁ · C ₁ )), the resonance frequency f ₀ ′ when the inductance of the power system 52 forms the resonance circuit of the LC filter unit 54 is f ₀ ′ = f ₀ · √ ((L ₁ + L ₂ ) / L ₂ ) To change. According to the expression of f ₀ ′, the resonance frequency f ₀ of the LC filter unit 54 increases as the inductance L ₂ of the power system 52 increases. For example, the resonance frequency f ₀ of the LC filter unit 54 becomes equal to the system frequency f. be lower than the third harmonic frequency 3f _S of _S, it is possible to close the inductance L ₂ of the electric power system 52 to the third harmonic frequency 3f _S.

In this case, since the third harmonic current flows from the power system 52 to the capacitor of the LC filter unit 54 as a resonance current, the third harmonic component included in the alternating current output to the power system 52 increases rapidly. And harmonic distortion gets worse. When the resonance frequency f ₀ of the LC filter unit 54 is close to the third harmonic frequency 3f _S of the system frequency f _S , the phase of the third harmonic is close to 180 °, and thus the opposite phase (−180 If the phase of the third harmonic is reversed, the harmonic distortion suppression control in the feedback control system becomes positive feedback control as described above, and control becomes impossible. . As a result, when the harmonic distortion cannot be suppressed and the standard is not satisfied, the grid-connected inverter device will be abnormally stopped.

  This invention makes it the subject to provide the grid connection inverter apparatus which can suppress the divergence of a feedback control system by adjusting the phase of the harmonic of the control object of a feedback control system automatically. .

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

  The grid-connected inverter device provided by the present invention is provided between a DC power source and a power system, converts DC power supplied from the DC power source to AC power of a system frequency, and supplies the AC power to the power system. A grid-connected inverter device comprising a bridge circuit formed by bridge-connecting a plurality of switching elements, a DC-AC conversion means for converting DC power supplied from the DC power source into the AC power, and the DC -Filter means provided at the output stage of the AC conversion means for removing switching noise contained in the AC signal output from the DC-AC conversion means; and detecting an AC signal output from the filter means to the power system AC signal detecting means for detecting a harmonic wave of a predetermined order included in the AC signal detected by the AC signal detecting means at a predetermined cycle. Harmonics are extracted from the harmonic level extracting means for extracting the level, and the level extracted by the harmonic level extracting means and the predetermined phase of the harmonic set in advance at the predetermined period, Output signal compensation command generating means for generating an output signal compensation command for suppressing the harmonics contained in the AC signal output from the filter means using harmonics, and the DC-AC in the predetermined cycle An output signal command for outputting an AC signal having the system frequency from the conversion unit is generated, and the plurality of switchings are performed using the output signal command and the output signal compensation command generated by the output signal compensation command generation unit. A control signal for controlling the on / off operation of the element is generated and extracted by the harmonic control means for supplying to the DC-AC conversion means and the harmonic level extraction means And determining means for determining whether or not the control by the harmonic control means tends to diverge based on the level to be controlled, and during the control by the harmonic control means, the control by the harmonic control means is performed by the determining means. When it is determined that there is a tendency to diverge, the control by the harmonic control means is stopped, the phase changing means for changing the predetermined phase in the output signal compensation command generating means to a different phase, and the output signal compensation command generation And a harmonic control restarting means for starting the control by the harmonic control means by replacing the predetermined phase in the means with the phase changed by the phase changing means (Claim 1). .

  According to this invention, during the control by the harmonic control means, if it is determined by the determination means that the control by the harmonic control means tends to diverge, the control by the harmonic control means is stopped, and the output signal compensation command The predetermined phase in the generating means is changed to a different phase. Then, the predetermined phase in the output signal compensation command generating means is replaced with the changed phase, and the control by the harmonic control means is started. In this way, for example, even if the resonance frequency of the filter means is close to the harmonic frequency due to the inductance of the power system and the harmonic current may flow from the power system to the filter means as a resonance current, Since the phase is replaced with an appropriate phase and the control by the high frequency control means is performed, the divergence of the feedback control system constituted by the AC signal detection means, the harmonic level extraction means, the output signal compensation command generation means and the high frequency control means is reduced. Can be suppressed.

  According to a preferred embodiment, the discriminating unit compares the level extracted by the harmonic level extracting unit with a predetermined first threshold, and a time when the extraction level exceeds the predetermined first threshold for a predetermined time If it continues above, it is good to discriminate | determine that the control by the said harmonic control means has a divergence tendency (Claim 2).

  According to another preferred embodiment, the phase changing means includes a plurality of phases obtained by changing the predetermined phase in the output signal compensation command generating means at a predetermined pitch within a predetermined angular range set in advance. Are temporarily controlled by the harmonic control means, and the level extracted by the harmonic level extraction means is the lowest of the plurality of phases during the control by the harmonic control means. Preferably, the phase corresponding to is used as the different phase.

  According to another preferred embodiment, when the level extracted by the harmonic level extraction means exceeds a second threshold value smaller than the first threshold value during temporary control by the harmonic control means. The harmonic phase in the generation of the output signal compensation command is changed within the predetermined angle range at a pitch different from the predetermined pitch for each period, and then temporarily controlled by the harmonic control unit again. It is good to carry out (Claim 4).

  According to another preferred embodiment, the AC signal detected by the AC signal detection means is a three-phase AC signal, and the harmonic level extraction means converts the three-phase AC to the d-axis and q-axis. A rotation coordinate conversion means for converting to a two-phase signal; and a DC extraction means for extracting only the direct current component of the d-phase and q-axis two-phase signals converted by the rotation coordinate conversion means. The command generation means integrates the d-axis and q-axis DC components extracted from the DC extraction means, respectively, the d-axis and q-axis DC components integrated by the integration means, and the predetermined phase It is good to be comprised with the rotation inverse coordinate conversion means to convert into a three-phase alternating current harmonic using (Claim 5).

  According to another preferred embodiment, the harmonics of the predetermined order include at least third, fifth, seventh, eleventh and thirteenth harmonics, and the harmonic control is performed for each harmonic. It is preferable to provide a feedback control system by means.

  According to another preferred embodiment, the DC power source may be a solar cell.

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

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings.

  FIG. 1 is a diagram showing a configuration of a grid interconnection inverter system to which a grid interconnection inverter device according to the present invention is applied.

  This grid-connected inverter system includes a solar cell 1, a grid-connected inverter device 2, and a power system 3.

  The solar cell 1 corresponds to the “DC power supply” of the present invention. The solar cell 1 has a large number of photoelectric conversion elements (not shown) made of a semiconductor such as silicon, and converts light energy into electric energy by each photoelectric conversion element for output. The solar cell 1 supplies DC power to the grid interconnection inverter device 2. The power system 3 supplies commercial power (in Japan, AC power of 50 Hz or 60 Hz, which is a system frequency) to a general household or the like.

  The grid interconnection inverter device 2 includes a DC-AC conversion unit 4, a filter unit 5, a transformer unit 6, a disconnecting contactor 7, a control unit 8, a first current sensor 11, and a second current sensor 12. The DC-AC conversion unit 4, the filter unit 5, the transformer unit 6, and the disconnecting contactor 7 are arranged in series in this order between the terminal 2a to which the DC voltage is input from the solar cell 1 and the power system 3. Are connected to each other. The control unit 8 is connected to the DC-AC conversion unit 4 via the control line 9.

  In addition, L between the grid connection inverter apparatus 2 and the electric power system 3 shows the inductance of the electric power system 3, and the value changes according to the form of the electric power system 3 and an operation condition.

  The DC-AC converter 4 converts the DC voltage supplied from the solar cell 1 into an AC voltage v and outputs it. The DC-AC converter 4 is configured by a voltage-controlled self-excited inverter circuit including a three-phase bridge circuit including a plurality of (for example, six) switching elements (not shown) such as bipolar transistors, field effect transistors, and thyristors. ing. Specifically, the DC-AC converter 4 has the circuit configuration shown in FIG. 2 (note that the first current sensor 11 is omitted in FIG. 2).

  That is, the DC-AC conversion unit 4 is configured by a bridge circuit in which six switching elements TR1 to TR6 are bridge-connected. Feedback diodes D1, D2, D3, D4, D5, and D6 are connected in parallel to the switching elements TR1, TR2, TR3, TR4, TR5, and TR6, respectively. The DC voltage Vdc output from the solar cell 1 is supplied to both ends of the series connection of the switching element TR1 and the switching element TR2, the series connection of the switching element TR3 and the switching element TR4, and the series connection of the switching element TR5 and the switching element TR6. Three-phase alternating current voltage and alternating current (U phase, V phase, from connection point a between element TR1 and switching element TR2, connection point b between switching element TR3 and switching element TR4, and connection point c between switching element TR5 and switching element TR6. W-phase AC voltage and AC current) are respectively output.

  The six switching elements TR <b> 1 to TR <b> 6 are each controlled to be turned on and off by a PWM (Pulse Width Modulation) signal output from the control unit 8. The control unit 8 controls the value of the AC output voltage v output from the DC-AC conversion unit 4 by controlling the pulse width of the PWM signal.

The filter unit 5 removes switching noise included in the AC output voltage v output from the DC-AC conversion unit 4. The filter unit 5 is configured by, for example, an LC low-pass filter. Specifically, as shown in FIG. 2, the filter unit 5 connects the inductors L _F to the output lines from the connection points a, b, and c, and connects the capacitors C _F between the output lines at the subsequent stages. It is a thing. Inverted L-type connection by the U-phase of the inductor L _F and the capacitor C _F between the output line, V-phase, low-pass filter is configured for each phase of the W-phase.

The first current sensor 11 detects the alternating current i ₁ output from the DC-AC converter 4. The second current sensor 12 detects the alternating current i ₂ output from the transformer unit 6. Since the DC-AC converter 4 converts the DC voltage into a three-phase (U-phase, V-phase, W-phase) AC voltage, the AC current i ₁ detected by the first current sensor 11 includes the U-phase voltage. AC current i _1U , V-phase AC current i _1V, and W-phase AC current i _1W are included. Similarly, the AC current i ₂ detected by the second current sensor 12 includes a U-phase AC current i _2U , a V-phase AC current i _2V, and a W-phase AC current i _2W . The first current sensor 11 and the second current sensor 12 are connected to the control unit 8, and the alternating currents i ₁ and i ₂ detected by these current sensors 11 and 12 are input to the control unit 8.

  In addition, the control system comprised by the 1st and 2nd current sensor 11 and the control part 8 connects the alternating voltage and alternating current output from the DC-AC conversion part 4 to the electric power grid | system 3 so that it may mention later. Therefore, the feedback control system is configured to perform control so as to satisfy the standards (including the harmonic distortion suppression standard). Hereinafter, this control system is referred to as a “feedback control system”.

  The transformer unit 6 boosts or lowers the AC output voltage output from the filter unit 5 to substantially the same level as the system voltage. The disconnecting contactor 7 is for disconnecting the grid-connected inverter system from the power system 3 when an abnormality occurs.

  The control unit 8 constitutes a feedback control system by the first and second current sensors 11 and 12 and controls the DC-AC conversion operation of the DC-AC conversion unit 4. Specifically, the control unit 8 provides the DC-AC conversion unit 4 with an AC voltage and an AC current that satisfy the guidelines for the power system 3 (system frequency with harmonic distortion suppressed within a predetermined allowable range. The generation of the PWM signal is controlled so as to output an alternating voltage and an alternating current. The control unit 8 is composed of a microcomputer and periodically generates a PWM signal by digital arithmetic processing.

  Note that, in a grid-connected inverter device using a solar cell as a DC power supply, the maximum power follow-up control is generally performed in feedback control. However, in the control unit 8 in the present embodiment, the configuration of the maximum power follow-up control is omitted. Now, a configuration related to harmonic distortion suppression control will be described.

  The control unit 8 includes a harmonic extraction control unit 13, a fundamental wave component generation unit 14, a first calculation unit 15, a second calculation unit 16, a current control unit 17, and a PWM signal generation unit 18. ing.

The harmonic extraction control unit 13 extracts a harmonic level of a predetermined order included in the detected current i ₂ detected by the second current sensor 12, and a predetermined level set in advance for this level and its harmonics. Generate harmonics from the phase. Then, the harmonic extraction control unit 13 creates a current compensation command value as an output signal compensation command for suppressing harmonics of the order included in the AC signal output from the filter unit 5 using this harmonic. Then, it is output to the first calculation unit 15. Further, when the feedback control system tends to diverge, the harmonic extraction control unit 13 performs phase search control on the detected current i ₂ detected by the second current sensor 12 to suppress divergence of the feedback control system. It has the function to do.

  Here, the phase search control is a control for searching for an appropriate value because the predetermined phase set for each harmonic in the harmonic extraction control unit 13 is not appropriate when the feedback control system tends to diverge. It is. Details of the phase search control will be described later.

  The fundamental wave component generation unit 14 generates a fundamental frequency of AC voltage and AC current to be output from the DC-AC conversion unit 4, that is, a command value of the system frequency. The fundamental wave frequency command value output from the fundamental wave component generation unit 14 is input to the first calculation unit 15.

  The first computing unit 15 adds the current compensation command value output from the harmonic extraction control unit 13 to the fundamental frequency command value output from the fundamental component generation unit 14. The addition result by the first calculation unit 15 is input to the second calculation unit 16. By adding the current compensation command value to the command value of the fundamental frequency, the command value input to the second calculation unit 16 is a command value obtained by mixing the fundamental wave component and the harmonic component to be suppressed.

The second calculation unit 16 subtracts the detected current i ₁ detected by the first current sensor 11 from the addition result from the first calculation unit 15. In this subtraction process, the deviation of the actual AC current from the calculation result (control target AC current) by the first calculation unit 15 is obtained. The deviation calculated by the second calculation unit 16 is input to the current control unit 17.

  The current control unit 17 generates a voltage correction command value such that the deviation becomes zero by performing P (proportional) control on the deviation input from the second calculation unit 16. This voltage correction command value is input to the PWM signal generator 18.

  The PWM signal generation unit 18 generates a PWM control signal for controlling a plurality of switching elements of the three-phase bridge circuit in the DC-AC conversion unit 4. The PWM signal generation unit 18 generates an AC voltage signal based on the voltage correction command value input from the current control unit 17, compares the AC voltage signal with a predetermined triangular waveform, and generates a PWM control signal.

  As shown in FIG. 2, the three-phase bridge circuit in the DC-AC conversion unit 4 includes switching elements TR1 and TR2, switching elements TR3 and TR4, and switching elements TR5 and TR6, respectively. The three pairs of switching elements are controlled to be turned on and off by three types of PWM control signals having different phases. Therefore, the PWM signal generation unit 18 generates three types of PWM control signals having different phases, and these PWM control signals are input to the DC-AC conversion unit 4. Moreover, the control part 8 except the harmonic extraction control part 13 functions as a "harmonic control means" of the present invention.

  FIG. 3 is a block diagram showing an internal configuration of the harmonic extraction control unit 13.

  The harmonic extraction control unit 13 includes an AD conversion unit 21, a plurality of data processing units 22, an addition unit 23, and a reset unit 24.

The AD converter 21 converts an analog signal as a detected current (alternating current) i ₂ detected by the second current sensor 12 into a digital signal. The detection current i ₂ as a digital signal converted by the AD conversion unit 21 is input to each of the plurality of data processing units 22.

The data processing unit 22 extracts an n (n: odd number greater than or equal to 3) order harmonic component included in the detected current i ₂ detected by the second current sensor 12, and suppresses the n order harmonic component. Each current compensation command value is output. Therefore, the data processing unit 22 is provided according to the nth harmonic. For example, a data processing unit 22 for processing fifth, seventh, eleventh or thirteenth harmonics is provided. The basic configuration of each data processing unit 22 that processes each nth-order harmonic is the same, and the data processing unit 22 that processes the third-order harmonic among the nth-order harmonics will be mainly described below.

  The adding unit 23 adds the n-order harmonic current compensation command value input from each data processing unit 22 for each of U, V, and W phases. The three-phase current compensation command value output from the adding unit 23 is input to the reset unit 24.

  The reset unit 24 resets the current compensation command value output from the data processing unit 22 at a predetermined timing based on a reset control signal from a reset control unit 42 described later. The predetermined timing is when control for suppressing high-frequency distortion in the feedback control system (hereinafter referred to as “high-frequency suppression control”) is stopped and phase search control is started as described later.

  The data processing unit 22 includes a three-phase / two-phase conversion unit 31, a dq conversion unit 32, an LPF unit 33, a gain processing unit 34, an integration processing unit 35, an inverse dq conversion unit 36, a two-phase / three-phase unit. The phase conversion unit 37 and the basic configuration are made. In the present embodiment, a divergence determination unit 41, a reset control unit 42, a phase adjustment unit 43, and a level monitoring unit 44 are further provided for the above basic configuration.

The three-phase / two-phase converter 31 converts the three-phase alternating current i ₂ detected by the second current sensor 12 into a two-phase signal (iα, iβ) in the stationary coordinate system (α axis, β axis). It is. The alternating current i ₂ converted into the two-phase signal is input to the dq converter 32.

The dq converter 32 converts the alternating current i ₂ converted into the two-phase signal into a signal (id, iq) of the rotating coordinate system (d axis, q axis). For example, if it is a third harmonic, it is converted into a rotating coordinate system that rotates at 3ωt (where ωt is the rotation angle of the fundamental wave (system frequency) positive phase). By this rotational coordinate conversion, the alternating current i ₂ can be expressed by the DC amount of the d-axis output value id and the q-axis output value iq. These output values id and iq are input to the LPF unit 33.

  The LPF unit 33 extracts only the level of the third harmonic. The LPF unit 33 is composed of a digital low-pass filter. In this case, the frequency other than the third harmonic is represented by the AC amount of the difference frequency from the third harmonic. In view of this, the LPF unit 33 averages the AC amount to zero, thereby removing harmonic levels other than the third harmonic level. The three-phase / two-phase conversion unit 31, the dq conversion unit 32, and the LPF unit 33 function as “harmonic level extraction means” of the present invention.

  The gain processing unit 34 calculates the difference between each output value id, iq from the LPF unit 33 and a predetermined threshold value. That is, in the gain processing unit 34, for example, zero is set as the predetermined threshold value, and the gain processing unit 34 calculates the deviation between each output value id, iq from the LPF unit 33 and zero, and integrates the calculated deviation. To the unit 35. The predetermined threshold corresponds to a harmonic suppression level, and is set to zero as an example in the present embodiment.

  The integration processing unit 35 integrates the deviation from the gain processing unit 34 (for example, I (integral) control). The integrated deviation is input to the inverse dq conversion unit 36.

  The inverse dq converter 36 uses a two-phase signal (iα, iβ) in the stationary coordinate system (α axis, β axis) using an integral deviation (DC amount) expressed in the rotating coordinate system and a predetermined phase set in advance. ). This two-phase signal is input to the two-phase / three-phase converter 37.

  The two-phase / three-phase converter 37 reversely converts the two-phase signal input from the inverse dq converter 36 into a three-phase alternating current, and supplies it to the adder 23 as a current compensation command value corresponding to the nth harmonic. Output. The integration processing unit 35, the inverse dq conversion unit 36, and the two-phase / three-phase conversion unit 37 function as “output signal compensation command generation means” of the present invention.

  The divergence determination unit 41 determines whether or not the feedback control system has a divergence tendency. The divergence determination unit 41 includes a comparison unit 41a and a determination unit 41b. The comparison unit 41a compares the output value iq (DC amount) of the LPF unit 33 with a predetermined first threshold value. The comparison result in the comparison unit 41a is input to the determination unit 41b. The determination unit 41b determines whether or not the feedback control system tends to diverge based on the comparison result in the comparison unit 41a.

  Specifically, the determination unit 41b determines whether or not the feedback control system tends to diverge depending on whether or not the time when the output value iq of the LPF unit 33 exceeds the first threshold continues for a predetermined time or more. That is, as shown in FIG. 4, the comparison unit 41a samples the output value iq of the LPF unit 33 at a predetermined cycle (for example, 0.25 msec). Next, it is detected that the output value iq of the LPF unit 33 has become equal to or greater than the first threshold value, and when the detection continues for a plurality of times (for example, three times), it is determined that the feedback control system tends to diverge.

  That is, the fact that the feedback control system tends to diverge indicates that, for example, the phase of the nth-order harmonic is about to become opposite. If the phase is about to become opposite, for example, the level of the nth-order harmonic also increases. Therefore, in the present embodiment, the level of the output value iq of the LPF unit 33 is compared with a predetermined first threshold value to determine whether or not the feedback control system tends to diverge.

  Note that the output value iq of the LPF unit 33 may suddenly rise due to a cause different from the divergence of the feedback control system. Also in this case, if it is determined that the feedback control system tends to diverge, false detection occurs, and therefore the determination unit 41b detects that the output value iq of the LPF unit 33 is equal to or greater than the first threshold value a plurality of times. Unless it continues, it is determined that the feedback control system does not tend to diverge. The divergence determining unit 41 functions as the “discriminating unit” of the present invention.

By the way, the harmonic distortion suppression control in the feedback control system is performed such that the harmonic distortion of the AC voltage and AC current output to the power system 3 satisfies the guidelines. If the harmonic level included in the alternating current i ₂ detected by the second current sensor 12 is sufficiently suppressed to satisfy the guideline, the suppression control of the harmonic does not necessarily have to be continued. .

  Therefore, the divergence determining unit 41 is provided with an auxiliary threshold for determining whether the level sufficiently satisfies the guideline for each harmonic (first threshold> auxiliary threshold), and the output value iq of the LPF unit 33 is You may make it detect whether it is below an auxiliary | assistant threshold value. Then, when it is detected that the output value iq is equal to or less than the auxiliary threshold, a process for stopping the harmonic suppression control in the feedback control system may be performed.

  By performing such processing, when the output value iq is less than or equal to the auxiliary threshold value, it is assumed that the harmonic distortion factor is originally small. Therefore, by stopping the harmonic suppression control, the load of the control processing is reduced. There is an advantage that can be reduced.

  When the divergence determination unit 41 determines that the feedback control system has a divergence tendency, the divergence determination unit 41 outputs a determination result that the feedback control system has a divergence tendency to the reset control unit 42 and the phase adjustment unit 43.

  Based on the determination result from the divergence determination unit 41, the reset control unit 42 resets the integration value in the integration processing unit 35 and the current compensation command value that is the output of the harmonic extraction control unit 13. Specifically, the reset control unit 42 outputs a reset command to the integration processing unit 35 and the reset unit 24 when a determination result indicating that the feedback control system tends to diverge is input from the divergence determination unit 41. As a result, the integration processing unit 35 resets the integrated deviation value of the gain processing unit 34. The reset unit 24 resets the current compensation command value (stops input of the current compensation command value to the first calculation unit 15). This is to stop the harmonic suppression control and shift to phase search control.

  In the harmonic extraction control unit 13, when the divergence determination unit 41 determines that the feedback control system has a divergence tendency, the control proceeds to phase search control. The phase search control is a process for searching for the optimum phase of the harmonic in the harmonic suppression control in order to avoid the divergence tendency in the feedback control system. In other words, this is a process for adjusting the rotation angle at the time of the rotation coordinate conversion in the inverse dq conversion unit 36 to an appropriate phase value.

  When the divergence determining unit 41 determines that the feedback control system has a divergence tendency, the phase adjusting unit 43 adjusts a predetermined predetermined harmonic phase used in the inverse dq conversion unit 36. is there. The phase adjustment unit 43 includes a phase variable unit 43a and a phase width change unit 43b.

  When the phase variable unit 43a receives a determination result indicating that the feedback control system tends to diverge from the divergence determining unit 41, the current phase of the harmonics (hereinafter referred to as “reference phase”) used in the inverse dq conversion unit 36. The phase φ ′ different from φ is output to the inverse dq converter 36 as a rotation angle command value at the time of inverse dq conversion.

  Specifically, as shown in FIG. 5, the phase variable unit 43 a has a phase corresponding to a predetermined displacement angle m · η (m is an integer, η is a reference displacement angle) with respect to a harmonic reference phase φ. Are outputted to the inverse dq converter 36 as a new phase φ ′ (= φ + m · η). The waveform shown in FIG. 5 is a sine wave for convenience of explanation, but the actual waveform is not limited to this. After that, as shown in Table 1, the phase variable unit 43a changes the displacement angle m · η every predetermined time, and sequentially outputs the displaced new phases to the inverse dq conversion unit 36. In this case, the phase variable unit 43 a outputs a timing signal to the level monitoring unit 44 every time the displaced new phase is output to the inverse dq conversion unit 36.

  For example, the phase variable unit 43 a outputs a new phase φ ′ whose phase is shifted by the displacement angle η with respect to the reference phase φ to the inverse dq conversion unit 36 at the first output time. After the predetermined time has elapsed, at the time of the second output, a new phase φ ′ having a phase shifted by the displacement angle 2η with respect to the phase φ is output to the inverse dq conversion unit 36.

  Table 1 shows a case where the phase variable unit 43a changes the phase while the displacement angle m · η rotates once (m · η = 360 °). That is, if the number of outputs m is 12, the displacement angle η is 30 °, and the phase variable unit 43a is displaced 12 times while being displaced by 30 ° while the displacement angle m · η is rotated once. Is output. In the present embodiment, the phase varying unit 43a performs an operation for changing the phase in an angle range over two rotations (0 ° to 720 °). This is to improve the accuracy of control. Note that the angle range of the operation for changing the phase is not limited to 0 ° to 720 °.

  The level monitoring unit 44 monitors the level of the output value iq of the LPF unit 33 while the phase variable unit 43a outputs the phase in the angle range of 0 ° to 720 ° while displacing the phase in the phase search control, and the displacement angle The timing when the level becomes the minimum value during m · η rotates twice is output to the phase variable unit 43a. In other words, the level monitoring unit 44 has a memory (not shown), and the level value of the output value iq of the LPF unit 33 and the level value in each level value in accordance with the operation of shifting the phase in the phase variable unit 43a. The time since the start of the phase search control is stored. Then, during the two rotations of the displacement angle m · η, the time from the start of the phase search control when the level reaches the minimum value is output to the phase variable unit 43a.

FIG. 6 is a diagram illustrating an example of the relationship between the level and phase detected by the level monitoring unit 44. According to the figure, for example, when the displacement angle is “3η”, which is the third output from the displacement variable unit 43a, the level detected by the level monitoring unit 44 is minimum (see Lm in FIG. 5). The level monitoring unit 44 outputs the time T ₃ after the start of the phase search control at the minimum value level value (Lm) to the phase variable unit 43a.

Since the phase variable unit 43a knows at which timing each phase that has been displaced is output, a signal (for example, time T) from the level monitoring unit 44 that indicates the timing when the level reaches the minimum value. Based on ₃ ), the displacement angle m · η of the phase output at the above timing is selected from the plurality of phases output to the inverse dq conversion unit 36. For example, when the time when the level reaches the minimum value from the level monitoring unit 44 is the third output time in Table 1, “3η” is selected as the displacement angle m · η.

  The phase variable unit 43a sets the selected displacement angle m · η as an optimum value, shifts the phase again by the optimum displacement angle m · η with respect to the reference phase φ, and converts the displaced phase to the inverse dq conversion unit 36. And output as a rotation angle command value during dq reverse conversion. When the phase selected with this optimum value is output to the inverse dq conversion unit 36, the feedback control system again shifts from phase search control to normal harmonic suppression control. That is, in the harmonic suppression control in the data processing unit 22 at this time, the current compensation command value is generated using the phase when the distortion component of the harmonic becomes the smallest. The phase varying unit 43a functions as the “phase changing unit” of the present invention.

In this way, the phase variable unit 43a shifts the phase by the displacement angle and outputs it to the inverse dq conversion unit 36, and the level monitoring unit 44 selects the displacement phase when the level is the minimum, for example, the power system Even when the resonance frequency f ₀ of the LC filter circuit 5 is changed to a frequency close to the harmonic by the inductance L _{2 of} 3, and the phase of the harmonic is close to 180 °, it is set in the inverse dq converter 36. Since the high-frequency suppression control is performed by replacing the phase with an appropriate phase, the possibility that the feedback control system diverges can be further reduced.

  Even if the divergence tendency of the feedback control system is suppressed by the displacement phase searched in the phase search control of the phase variable unit 43a and the normal operation of the suppression control of the harmonic distortion in the feedback control system is ensured, the phase width changing unit 43b Since the wave may not be sufficiently suppressed to satisfy the guidelines, the phase width is further finely varied and phase search control is performed again to find the optimal phase where the harmonics sufficiently satisfy the guidelines It is. That is, when phase search control is performed with the phase varied in the phase variable unit 43a, the divergence of the feedback control system is suppressed, but the feedback control system has a distortion rate equal to or higher than a predetermined standard value (for example, 3% or less). It may be working. Therefore, in such a case, the phase width to be further displaced is subdivided from the phase width changing unit 43b and the phase search control is performed again to search for a more optimal high-frequency phase.

  In this case, when the harmonic suppression control is started again based on the displacement phase selected by the phase variable unit 43a in the initial phase search control, the level monitoring unit 44 detects the level value as a predetermined second threshold value ( If it does not fall below (first threshold value> second threshold value), a signal indicating this is output to the phase width changing unit 43b. That is, as shown in FIG. 6, the minimum value Lm of the level is lower than the first threshold value, but is not lower than the second threshold value.

  Based on the signal from the level monitoring unit 44, the phase width changing unit 43b is a displacement angle m · η / p (p is an integer) obtained by further subdividing the displacement angle m · η described above with respect to the reference phase φ. The phase is shifted, and a new phase φ ″ (= φ + m · η / p) is output to the inverse dq conversion unit 36. Thereafter, the phase width changing unit 43b changes the displacement angle m · η / p every predetermined time. Thus, the displaced new phase φ ″ is sequentially output to the inverse dq converter 36.

  The level monitoring unit 44 outputs the output value iq of the LPF unit 33 while the phase width changing unit 43b outputs the phase while displacing the phase in the second phase search control (while the displacement angle m · η / p rotates twice). And the timing when the level reaches the minimum value is output to the phase width changing unit 43b.

  The phase width changing unit 43b selects the phase displacement angle m · η / p output at that time based on the signal from the level monitoring unit 44 indicating the timing when the level reaches the minimum value. The selected displacement angle m · η / p is set to the optimum value, the phase is shifted again with respect to the reference phase φ by the optimum displacement angle m · η / p, and the new phase φ ″ thus displaced is subjected to inverse dq conversion. It outputs to the part 36.

  In this way, the variable phase width is further subdivided and phase search control is performed, so that a more optimal high-frequency phase can be searched. It should be noted that the value of p used when subdividing is further subdivided as the value increases, and a more optimal high-frequency phase can be searched for. However, the load of control processing increases accordingly, so that an appropriate value is obtained. Is preferably selected.

  Next, phase search control in the grid-connected inverter device will be described with reference to the flowchart shown in FIG. In the following description, it is assumed that normal harmonic distortion extraction operation control in the harmonic extraction control unit 13 is also performed.

  In the comparison unit 41a of the divergence determination unit 41, the level of the output value Iq (DC amount) that is the output of the LPF unit 22 is constantly monitored and detected (S1). The divergence determining unit 41 determines whether or not the feedback control system has a divergence tendency based on the comparison result of the comparing unit 41a (S2).

  Specifically, when the output value iq of the LPF unit 33 is equal to or higher than the first threshold value in the comparison unit 41a, the result is output to the determination unit 41b. In the determination unit 41b, as shown in FIG. 4, the output of the comparison unit 41a is sampled at a predetermined period (for example, 0.25 msec), and the output value iq of the LPF unit 33 is equal to or higher than the first threshold value at each sampling. It is determined whether or not it has been continuously detected a plurality of times (for example, three times).

  The determination unit 41b determines that the feedback control system tends to diverge when the output value iq of the LPF unit 33 is continuously detected a plurality of times (for example, three times) when the output value iq is equal to or greater than the first threshold (S2). : YES) When the output value iq of the LPF unit 33 is not continuously detected when the output value iq is equal to or greater than the first threshold, for example, when it is suddenly singular, it is determined that the feedback control system does not tend to diverge (S2). : NO).

  When the determination unit 41b determines that the feedback control system tends to diverge (S2: YES), the determination result is output to the reset control unit 42 and the phase adjustment unit 43. Thereby, phase search control is started. That is, in the feedback control system, phase search control is performed instead of normal harmonic suppression control.

  First, the reset control unit 42 outputs a reset command to the integration processing unit 35 and the reset unit 24 (S3). Thereby, the integration processing unit 35 resets the integrated value of the gain processing unit 34. The reset unit 24 resets the current compensation command value.

  In the phase variable unit 43a of the phase adjusting unit 43, when a determination result indicating that the feedback control system tends to diverge is input from the divergence determining unit 41, as shown in FIG. The phase is shifted by a predetermined displacement angle η (refer to the waveform of the dashed line in S4 in FIG. 5). Then, a new phase φ ′ (= φ + η) is output to the inverse dq converter 36 as a rotation angle command value at the time of inverse dq conversion (S5). In the feedback control system, high-frequency distortion component extraction control is performed based on the new phase φ ′ output to the inverse dq converter 36.

  At this time, the level monitoring unit 44 detects the level of the output value Iq of the LPF unit 33. That is, the high-frequency level of the displaced new phase φ ′ is detected (S6) and stored in the memory of the level monitoring unit 44 (S7).

  Next, the phase variable unit 43a determines whether or not a predetermined time has elapsed (S8), and when the predetermined time has elapsed (S7: YES), the phase displacement for an angle range of 0 ° to 720 ° (for two laps). It is determined whether or not control has been performed (S9).

  When phase displacement control is not performed for the angle range of 0 ° to 720 ° (S9: NO), the process returns to step S4, and the phase is shifted at the next displacement angle 2η (S4, the two-dot chain line in FIG. 5). Waveform reference). Also in this case, a new phase φ ′ (= φ + 2η) is output to the inverse dq conversion unit 36 as a rotation angle command value at the time of inverse dq conversion (S5), and high-frequency distortion component extraction control is performed. Then, the level monitoring unit 44 detects the level of the output value Iq of the LPF unit 33, detects the high frequency level at the new phase φ ′ (S6), and stores it in the memory (S7).

  Thereafter, the same processing is performed, and when the phase displacement control is finished for the angle range of 0 ° to 720 ° (S9: YES), the level monitoring unit 44 sets the minimum value among the level values stored in the memory. Are selected (S10).

  Next, it is determined whether or not the selected minimum value level is below a predetermined second threshold (S11). The second threshold value is used to determine whether or not to perform phase search control again by subdividing the displacement angle in the phase width changing unit 43b. That is, although the feedback control system does not tend to diverge, it may operate at a distortion rate equal to or higher than a predetermined standard value (for example, 3% or less), and the second threshold value is used for the determination.

  When the level of the selected minimum value is lower than the predetermined second threshold (S11: YES), that is, feedback is performed without subdividing the displacement angle by the phase width changing unit 43b and performing phase search control again. When the control system is operating at a distortion rate equal to or less than a predetermined standard value, the level monitoring unit 44 outputs timing data when the level reaches the minimum value to the phase variable unit 43a.

  Since the phase variable unit 43a recognizes the timing when the phase is sequentially varied and output, the level is set to the minimum value based on the timing data from the level monitoring unit 44 when the level reaches the minimum value. The displacement angle m · η of the phase output at that time is selected (S12). Then, in the phase variable unit 43a, the selected displacement angle m · η is set to the optimum value, and the phase is shifted again by the optimum value of the displacement angle m · η with respect to the reference phase φ. Is output to the inverse dq converter 36 (S13).

  In this way, since the high-frequency phase is searched and selected so that the level detected by the level monitoring unit 44 is as low as possible, the occurrence of divergence in the feedback control system can be suppressed.

  On the other hand, when the level of the selected minimum value does not fall below the predetermined second threshold (S11: NO), the level monitoring unit 44 outputs a control signal indicating that to the phase width changing unit 43b. . With this control signal, the phase width changing unit 43b further subdivides the phase width and performs phase search control again.

  That is, the phase width changing unit 43b shifts the phase by a displacement angle m · η / p (p is an integer) obtained by further subdividing the displacement angle m · η described above based on the control signal from the level monitoring unit 44. Processing is performed (S14). Then, a new phase φ ″ (= φ + m · η / p) is output to the inverse dq converter 36 (S15). Thereafter, the displacement angle m · η / p is changed and output every predetermined time, and the level The monitoring unit 44 detects the level for each changed displacement angle m · η / p (S16) and stores it in the memory (S17).

  When these phase operations are repeatedly executed and the phase displacement control is finished for an angle range of 0 ° to 720 ° (S19: YES) after a predetermined time has elapsed (S18: YES), the level monitoring unit 44 stores in the memory. The level of the minimum value among the stored level values is selected (S20).

  Thereafter, the level monitoring unit 44 outputs the timing data when the level reaches the minimum value to the phase width changing unit 43b. In the phase width changing unit 43b, the level from the level monitoring unit 44 becomes the minimum value. Based on the timing data at this time, the phase displacement angle m · η / p output when the level reaches the minimum value is selected (S12). Then, the phase is shifted again with respect to the reference phase φ at the selected displacement angle m · η / p, and the displaced new phase φ ″ is output to the inverse dq conversion unit 36 (S13).

  In this way, when the feedback control system does not fall below the distortion rate in the initial phase search control, the displacement angle can be further subdivided to search for and select the optimal phase, thus making the divergence of the feedback control system more effective. Can be suppressed.

  Of course, the scope of the present invention is not limited to the embodiment described above. For example, in the above embodiment, the high-frequency level is detected to determine whether or not the initial phase search control is less than or equal to a sufficient distortion rate. Instead, the distortion rate is directly measured or calculated. You may do it.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the whole structure of the grid connection inverter system with which the grid connection inverter apparatus which concerns on this invention is applied. It is a figure which shows the circuit structure of the DC-AC conversion part and filter part which output a three-phase alternating current. It is a block diagram which shows the internal structure of a harmonic extraction control part. It is a figure for demonstrating the operation | movement for detecting whether a feedback system has a divergence tendency, (a) is a case where it is detected that a feedback system has a divergence tendency, (b) is a tendency for a feedback system to diverge. The case where it is detected that it is not in is shown. It is a figure for demonstrating the control which displaces a phase. It is a figure which shows an example of the relationship between the level and phase which a level monitoring part detects. It is a flowchart which shows the phase search control in a grid connection inverter apparatus. It is a figure which shows the whole conventional structure of the grid connection inverter system to which the grid connection inverter apparatus is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Grid connection inverter apparatus 3 Electric power system 4 DC-AC conversion part 5 Filter part 6 Transformer part 7 Disconnection contactor 8 Control part 11 1st current sensor 12 2nd current sensor 13 Harmonic extraction control part 14 Fundamental wave Component generation unit 15 First calculation unit 16 Second calculation unit 17 Current control unit 18 PWM signal generation unit 21 AD conversion unit 22 Data processing unit 23 Addition unit 24 Reset unit 31 Three-phase / two-phase conversion unit 32 dq conversion unit 33 LPF Unit 34 gain processing unit 35 integration processing unit 36 inverse dq conversion unit 37 two-phase / three-phase conversion unit 41 divergence determination unit 42 reset control unit 43 phase adjustment unit 44 level monitoring unit

Claims (7)

A grid-connected inverter device that is provided between a DC power source and a power system, converts DC power supplied from the DC power source into AC power having a system frequency, and supplies the AC power to the power system,
DC-AC conversion means comprising a bridge circuit formed by bridge-connecting a plurality of switching elements, and converting DC power supplied from the DC power source into the AC power;
Filter means provided at an output stage of the DC-AC conversion means, for removing switching noise contained in an AC signal output from the DC-AC conversion means;
AC signal detection means for detecting an AC signal output from the filter means to the power system;
Harmonic level extraction means for extracting a level of a harmonic of a predetermined order included in the AC signal detected by the AC signal detection means at a predetermined period;
In the predetermined cycle, the harmonic is generated from the level extracted by the harmonic level extraction means and a predetermined phase of the harmonic set in advance, and is output from the filter means using the harmonic. Output signal compensation command generating means for generating an output signal compensation command for suppressing the harmonics included in the AC signal,
Generates an output signal command for outputting an AC signal of the system frequency from the DC-AC converter in the predetermined cycle, and the output signal generated by the output signal command and the output signal compensation command generator Harmonic control means that generates a control signal for controlling on / off operation of the plurality of switching elements using a compensation command and supplies the control signal to the DC-AC conversion means;
Based on the level extracted by the harmonic level extraction means, a determination means for determining whether or not the control by the harmonic control means has a divergence tendency;
During the control by the harmonic control means, if the control by the determination means determines that the control by the harmonic control means tends to diverge, the control by the harmonic control means is stopped, and the output signal compensation command generation means Phase changing means for changing the predetermined phase to a different phase;
Harmonic control restarting means for starting the control by the harmonic control means by replacing the predetermined phase in the output signal compensation command generating means with the phase changed by the phase changing means;
A grid-connected inverter device comprising: The discrimination means includes
The level extracted by the harmonic level extraction means is compared with a predetermined first threshold value, and if the time when the extraction level exceeds the predetermined first threshold value continues for a predetermined time or longer, the control by the harmonic control means diverges. The grid-connected inverter device according to claim 1, wherein it is determined that there is a tendency. The phase changing means includes
The predetermined phase in the output signal compensation command generation means is replaced with a plurality of phases that are changed at a predetermined pitch within a predetermined angle range, and control by the harmonic control means is temporarily performed. And during the control by the harmonic control means, the phase corresponding to the lowest level extracted by the harmonic level extraction means among the plurality of phases is used as the different phase. The grid connection inverter apparatus of Claim 1 or 2.   During the temporary control by the harmonic control means, if the level extracted by the harmonic level extraction means exceeds a second threshold value smaller than the first threshold value, the harmonics in the generation of the output signal compensation command The phase of the wave is changed within the predetermined angle range at a pitch different from the predetermined pitch for each period, and the harmonic control means again performs temporary control. 4. The grid interconnection inverter device according to 3. The AC signal detected by the AC signal detecting means is a three-phase AC signal,
The harmonic level extraction means includes
Rotational coordinate conversion means for converting the three-phase alternating current into d-phase and q-axis two-phase signals, and direct current for extracting only the direct current components of the d-axis and q-axis two-phase signals converted by the rotational coordinate conversion means. It consists of extraction means,
The output signal compensation command generating means is
Integrating means for integrating the d-axis and q-axis DC components extracted from the DC extracting means respectively, and using the d-axis and q-axis DC components integrated by the integrating means and the predetermined phase, three-phase The system interconnection inverter device according to any one of claims 1 to 4, wherein the system interconnection inverter device comprises a rotating inverse coordinate conversion means for converting into an AC harmonic.   The harmonics of the predetermined order include at least third-order, fifth-order, seventh-order, eleventh-order, and thirteenth-order harmonics, and each harmonic has a feedback control system by the harmonic control means. The grid interconnection inverter device according to any one of claims 1 to 5.   The grid-connected inverter device according to any one of claims 1 to 6, wherein the DC power source is a solar battery.

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