JPH09163610A - Power unit of system interconnection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power unit linked to a circuit where the wave distortion of the output current of an inverter circuit is suppressed and besides higher efficiency than that of conventional one can be obtained, by controlling the objective value of boost of a boosting circuit to an always optimum value, regardless of the ripple of circuit voltage. SOLUTION: A DC power source 1 is linked to a commercial power system 8 through an inverter 20, and the inverter 20 is provided with a boosting circuit 2 and an inverter circuit 3. At the latter stage of the inverter circuit 3, a current detector 5 and a voltage detector 41 are connected, and a control circuit 6 makes the objective voltage of boost, based on the voltage detection signal V2 from the voltage detector 41, and adjusts the boosting ratio of the boosting circuit 2 so that the output voltage of the boosting circuit 2 may come close to that objective voltage of boost. Moreover, the control circuit 6 can make the objective voltage of boost, based on the current detection signal 1 from the current detector 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection power supply device for interconnecting a DC power source such as a solar cell to a commercial power system via an inverter, and more particularly to a system having a step-up circuit in front of an inverter circuit. The present invention relates to an interconnection power supply device.

[0002]

2. Description of the Related Art In a grid interconnection power supply device that converts an output voltage obtained from a direct current power source such as a solar cell into an alternating current by an inverter and supplies it to a commercial power grid, in order to supply power to the commercial power grid. A method is known in which a booster circuit is provided in an inverter to obtain a required voltage.

FIG. 7 shows the overall configuration of a conventional system interconnection power supply device. As shown in the figure, the DC output voltage obtained from the solar cell (10) is first calculated by the booster circuit of the inverter (90).
It is boosted by the (20) to the level that allows reverse flow to the commercial power system (8), and the inverter circuit (30) of the inverter (90)
Supplied to As a result, the input voltage of the inverter circuit (30) is converted into an alternating current and is reversely flown to the commercial power system (8). A control circuit (60) is connected to the booster circuit (20) and the inverter circuit (30), and the operations of the booster circuit (20) and the inverter circuit (30) are controlled by the control circuit (60). .

FIG. 8 shows a general booster circuit.
The booster circuit includes a switching element SW, a coil L, a diode D and a capacitor C. The step-up circuit performs a step-up operation by turning on / off the switching element SW, and its step-up ratio Vo / Vi changes according to the ON period of the switching element SW. For example, in FIG.
10, when the ON period and the OFF period of the switching element SW are the same, the step-up ratio is set to 2, and the ON period of the switching element SW is 3 of the OFF period as shown in FIG.
When the length is doubled, the boost ratio is set to 4.
As shown in the figure, the current IL flowing through the coil L during the step-up operation fluctuates around the average value Ia according to the ON / OFF of the switching element SW, and the maximum value Imax of the current IL rises as the step-up ratio increases. However, the minimum value Imin will decrease. Here, the loss of the booster circuit tends to increase rapidly as the current flowing through the switching element SW and the diode D increases. Therefore, the increase in loss due to the increase in the maximum value Imax of the current IL flowing through the coil L is larger than the decrease in loss due to the decrease in the minimum value Imin. As a result, the higher the boost ratio, the lower the loss of the entire booster circuit. Will increase. From this, it can be said that setting the boosting ratio of the boosting circuit as low as possible is effective in improving the efficiency of the circuit.

By the way, in order to reversely flow the electric power boosted by the booster circuit to the commercial power system, as shown in FIG. 11, the half value of the output voltage V1 of the booster circuit is less than the peak value Vp of the system voltage V. It is also necessary to be high. If the output voltage V1 of the booster circuit drops and its half value becomes lower than the peak value Vp of the system voltage V as shown in FIG. 12,
The waveform of the current I flowing into the commercial power system is a current waveform in which distortion W occurs near the peak point of the system voltage V as shown in the figure and harmonic components are added to the sine wave. Further, in a commercial power system, for example, for a 100V power supply, fluctuations in the system voltage are allowed within the range of 101 ± 6V according to the operational regulations, and it is usual that the peak value Vp of the system voltage V slightly fluctuates. Is. Therefore, when the peak value Vp of the system voltage rises, the waveform distortion W is likely to occur. Therefore, conventionally, as shown in FIG. 11, the boosting target voltage of the boosting circuit has a sufficient margin Vd from the peak value of the commercial power system voltage.
A constant value of (50 to 60 V) is set to prevent the generation of harmonic components.

[0006]

However, in the conventional inverter, the boosting target voltage is set to a constant value with a sufficient margin as described above, so that the waveform distortion of the output current of the inverter circuit is suppressed. Therefore, there is a problem that the boosting ratio is set higher than necessary, which lowers the efficiency of the boosting circuit. The object of the present invention is to suppress the waveform distortion of the output current of the inverter circuit by controlling the boosting target voltage of the boosting circuit to an optimum value at all times regardless of the fluctuation of the system voltage, and to achieve higher efficiency than the conventional one. It is to provide an obtained grid interconnection power supply device.

[0007]

In a system interconnection power supply device according to the present invention, a DC power source is connected to a commercial power system via an inverter, and the inverter has a booster circuit for boosting the output voltage of the DC power source. A control circuit that controls the step-up ratio of the step-up circuit and an inverter circuit that converts the output voltage of the step-up circuit into alternating current are provided.

A characteristic configuration of the system interconnection power supply device is that the control circuit detects the electric state quantity at the output end of the inverter circuit and the detected electric state quantity based on the detected electric state quantity. Signal processing means for creating a boost target voltage for suppressing the harmonic component contained in the output current of the inverter circuit to a certain level or less, and a boost ratio of the boost circuit so that the output voltage of the boost circuit approaches the boost target voltage. Boosting control means for controlling In particular,
The electrical state quantity is an output voltage of the inverter circuit or an output current of the inverter circuit.

In the above-mentioned grid interconnection power supply device of the present invention, when the output voltage of the inverter circuit, that is, the grid voltage is detected, the grid voltage is high and waveform distortion may occur in the output current. The step-up ratio can be adjusted to a magnitude according to the system voltage. Therefore, the waveform of the output current of the inverter circuit is not distorted. or,
By detecting the output current of the inverter circuit, the harmonic component contained in the current flowing into the system can be directly detected, and the boosting ratio can be adjusted so as to suppress the harmonic component. Therefore, the output current without waveform distortion is always obtained from the inverter circuit.

Specifically, the harmonic component is a frequency component that is an integral multiple of 2 or more of the system frequency.

The harmonic component generated in the output current due to the distortion of the output current waveform of the inverter circuit is a harmonic component that is an integral multiple of 2 or more of the system frequency. Therefore, the distortion of the waveform can be effectively suppressed by adjusting the boosting ratio so as to reduce these harmonic components.

In another system interconnection power supply device according to the present invention, a DC power source is connected to a commercial power system via an inverter, and the inverter has a booster circuit for boosting an output voltage of the DC power source and a booster circuit. A control circuit for controlling the step-up ratio of the circuit,
An inverter circuit for converting the output voltage of the booster circuit into alternating current is provided.

The characteristic configuration of the system interconnection power supply device is that the first voltage detector detects the output voltage of the booster circuit,
A second voltage detector for detecting an output voltage of the inverter circuit, wherein the control circuit is responsive to the magnitude of the output voltage of the inverter circuit based on the output signals of the first voltage detector and the second voltage detector. Control means is provided for controlling the step-up ratio so that the ratio of the output voltage of the step-up circuit to the voltage evaluation value becomes a predetermined constant value with reference to the voltage evaluation value. As the voltage evaluation value, for example, an effective value can be adopted.

In the system interconnection power supply device of the present invention,
The control circuit, the voltage evaluation value of the output voltage of the inverter circuit,
For example, since the boost ratio is adjusted so that the ratio of the output voltage of the booster circuit to the effective value becomes a predetermined constant value, the effective value of the output voltage of the inverter circuit, that is, the effective value of the system voltage is relative to the output voltage of the booster circuit. When there is a fear that waveform distortion will occur in the output current, the boost ratio is increased to increase the output voltage of the boost circuit. Therefore, the waveform of the output current of the inverter circuit is not distorted.

Further, in another system interconnection power supply device according to the present invention, a DC power source is connected to a commercial power system via an inverter, and the inverter has a booster circuit for boosting an output voltage of the DC power source and a booster circuit. A control circuit for controlling the step-up ratio of the circuit,
An inverter circuit for converting the output voltage of the booster circuit into alternating current is provided.

The characteristic configuration of the system interconnection power supply device comprises a current detector for detecting the output current of the inverter circuit, and the control circuit determines the system frequency of the inverter circuit from the output signal of the current detector. It is provided with a harmonic extraction means for extracting the harmonic component of an integral multiple and a control means for controlling the step-up ratio so as to suppress the extracted harmonic component to a certain level or less.

In the system interconnection power supply device of the present invention,
The harmonic extraction means extracts a harmonic component that is an integral multiple of 2 or more of the system frequency and is generated by the distortion of the waveform of the output current of the inverter circuit, and the control means controls the boosting ratio so as to suppress these harmonic components. Is adjusted, it is possible to always obtain an output current without waveform distortion from the inverter circuit.

In the concrete constitution of the grid interconnection power supply device,
The input terminal and the output terminal of the booster circuit are connected to each other via a switch means capable of ON / OFF control, and the control circuit turns on the switch means during a period when the booster ratio of the booster circuit is 1. Stop the boosting operation of the booster circuit.

As described above, during the period when the boost ratio is 1,
Since the output current from the DC power supply is supplied to the inverter circuit via the switch means, the loss due to the resistance of the circuit elements forming the booster circuit becomes zero.

[0020]

According to the system interconnection power supply device of the present invention, the step-up ratio of the step-up circuit is set to the lowest optimum value within the range in which no harmonic component is generated in the inverter output current, regardless of fluctuations in the system voltage. It can be controlled. As a result, the waveform distortion of the output current of the inverter circuit can be suppressed and higher efficiency can be obtained than in the conventional case.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below.
A detailed description will be given based on one embodiment with reference to the drawings. First Embodiment A grid-connected power supply device of this embodiment shown in FIG.
The step-up ratio of the step-up circuit (2) is controlled on the basis of the output voltage of the inverter circuit (3) constituting (9).

As shown in the figure, a DC power source comprising a solar cell
(1) is connected to the commercial power system (8) via an inverter (9). The inverter (9) includes a booster circuit (2) for boosting a DC output voltage obtained from the DC power supply (1) to a height at which reverse power flow can be performed with respect to the commercial power system (8), and a booster circuit.
An inverter circuit (3) is provided which converts the output voltage of (2) into alternating current and supplies it to the commercial power system (8). Further, a first voltage detector (4) for detecting the output voltage of the booster circuit (2) is provided at the front stage of the inverter circuit (3), and an inverter circuit is provided at the rear stage.
The second voltage detector (41) that detects the output voltage of (3) and the current detector (5) that detects the output current are connected, and the DC power supply (1) is connected in front of the booster circuit (2). A third voltage detector (42) for detecting the output voltage is connected. The output terminals of the first, second and third voltage detectors (4) (41) (42) and the current detector (5) are connected to the control circuit (6).

The control circuit (6) controls the inverter circuit (3) based on the current detection signal I from the current detector (5) and the second voltage detection signal V2 from the second voltage detector (41). A gate signal for driving is created, and the gate signal is supplied to each gate element G1, G2, G3, G4 of the inverter circuit (3). As a result, the inverter circuit (3) becomes a booster circuit.
The output voltage of (2) is converted into alternating current and output.

The control circuit (6) further includes first and second voltage detection signals V1 and V2 from the first and second voltage detectors (4) and (41).
Based on the above, a switching signal for controlling the boosting operation of the booster circuit (2) is created, and the switching signal is supplied to the switching element SW1 of the booster circuit (2). As a result, the booster circuit (2) boosts and outputs the output voltage of the DC power supply (1). FIG. 2 shows the configuration of the circuit portion of the control circuit (6) which performs the boost ratio control operation of the boost circuit (2). As shown, the second voltage detection signal V2 obtained from the second voltage detector (41) is first input to the effective value circuit (61). The effective value circuit (61) creates an effective value signal V2 'representing the effective value of the output voltage of the inverter circuit (3) based on the second voltage detection signal V2 and outputs it to the first amplifier (62). . In the first amplifier (62), the effective value signal V2 'is multiplied by the gain M to generate the boost target voltage signal MV2', which is output to the subsequent stage. Here, the gain M is set, for example, to obtain a minimum required boosting target voltage signal MV2 ′ for the effective value signal V2 ′ of the inverter circuit (3).
It is set to 1.7.

The boosting target voltage signal MV2 'is input to the first subtractor (63) together with the first voltage detection signal V1 obtained from the first voltage detector (4), and the boosting target voltage signal MV2' is inputted from the first voltage detection signal V1. The voltage signal MV2 'is subtracted to create the original error signal E, which is output to the second amplifier (64). Second amplifier (64)
Then, the gain N is multiplied to generate the reference error signal E ', which is output to the comparator (66). Here, the gain N is
For example, it is set to 10 to 100. In the comparator (66),
The triangular wave signal T output from the triangular wave generation circuit (65) is compared with the reference error signal E ', and a switching signal that is turned on when the triangular wave signal T is larger than the reference error signal E'is created, It is supplied to the switching element SW1.

3A and 3B show the operation of the comparator 66. For example, when the output voltage of the inverter circuit (3), that is, the system voltage gradually increases,
As described above, the reference error signal E'decreases gradually. Along with this, the ON period of the switching element SW gradually increases, and the boost ratio increases. On the contrary, when the system voltage gradually decreases, the reference error signal E ′ gradually increases, and accordingly, the ON period of the switching element SW gradually decreases and the boosting ratio decreases. Further, when the output voltage of the DC power source (1) decreases due to a decrease in the amount of solar radiation, the output voltage of the booster circuit (2) decreases accordingly, and the reference error signal E'decreases. Along with this, the ON period of the switching element SW becomes longer, and the boost ratio increases. On the contrary, when the output voltage of the DC power supply (1) rises, the output voltage of the booster circuit (2) rises, so that the reference error signal E'increases.
The ON period of the switching element SW is shortened and the boost ratio is reduced. As a result, the output voltage of the booster circuit (2) is always at a constant ratio to the effective value of the system voltage (U-phase and V-phase voltage in the case of the single-phase three-wire system), which is 1.7 in this embodiment.
Will be adjusted so that the ratio becomes.

As described above, according to this embodiment, the DC power source
When the output voltage or system voltage of (1) fluctuates, the boosting target voltage of the booster circuit (2) is optimally adjusted according to these fluctuations, so that the waveform of the output current of the inverter circuit (3) is distorted. There is no such thing.

Second Embodiment In the first embodiment, the step-up ratio of the step-up circuit (2) is controlled based on the output voltage of the inverter circuit (3), whereas the system connection of the present example is controlled. The system power supply device controls the step-up ratio on the basis of the output current of the inverter circuit (3). The configuration and operation of the step-up circuit (2) and the inverter circuit (3) are as shown in FIG. Same as the embodiment.

The control circuit (6) creates a switching signal based on the first voltage detection signal V1 obtained from the first voltage detector (4) and the current detection signal I obtained from the current detector (5). , And supplies the switching signal to the switching element SW1 of the booster circuit (2). This enables the boost circuit
The boosting operation of (2) is controlled. FIG. 4 shows the configuration of the circuit portion of the control circuit (6) which performs the step-up ratio control operation of the step-up circuit (2). As shown in the figure, the current detection signal I detected by the current detector (5) is first input to the bandpass filter circuit (67). The bandpass filter circuit (67) extracts the harmonic component, creates a harmonic current signal Io having a magnitude corresponding to the harmonic component, and outputs the harmonic current signal Io to the subsequent stage. Here, the harmonic component that occurs in the output current of the inverter circuit (3) is a harmonic component that is an integral multiple of 2 or more of the system frequency, and among these, a harmonic component that is an odd multiple of 3 or more is particularly large. Further, the level of the harmonic component decreases as the frequency increases, and the harmonic components 3 and 5 times the system frequency are dominant. Therefore, when the system frequency is 60 Hz, the band pass filter circuit (67) uses a band pass filter (72) that passes only the 180 Hz component as shown in FIG.
Bandpass filter (73) that passes the 80 Hz component and bandpass filter (74) that passes the 300 Hz component
Can be connected in parallel. The harmonic current signal Io thus created is input to the effective value circuit (68) shown in FIG. It is output to 69).

In the second subtractor (69), the harmonic suppression target value Iref is subtracted from the harmonic effective value signal Io ', and the signal
(Io'-Iref) is created and output to the third amplifier (70). Here, the harmonic suppression target value Iref is the inverter
It is set to a value of 1 to 2% of the rated current value of (9). Third
In the amplifier (70), the signal (Io'-Iref) is multiplied by the gain G to generate a signal [G (Io'-Iref)], which is output to the subsequent stage.

The signal [G (Io'-Iref)] is input to the adder (71) together with the boost target reference voltage value Vref, and these are added to add the boost target voltage signal [G (Io'-Iref)]. +
Vref] is created and output to the subsequent stage. Here, the boost target reference voltage value Vref is set to, for example, about 350V.

The boost target voltage signal [G (Io'-Iref) +
Vref] is input to the first subtractor (63) together with the first voltage detection signal V1 detected by the first voltage detector (4),
From the first voltage detection signal V1 to the boost target voltage signal [G (Io '
-Iref) + Vref] is subtracted to generate the original error signal E, which is output to the second amplifier (64). The second amplifier (64) multiplies the gain N to create a reference error signal E ', which is output to the comparator (66). The comparator (66) compares the triangular wave signal T output from the triangular wave generation circuit (65) with the reference error signal E ', and a switching signal which is turned on when the triangular wave signal T is larger than the reference error signal E'. Is generated and supplied to the switching element SW1. The operation of the comparator 66 is the same as that of the first embodiment.

As described above, in the present embodiment, the boosting target voltage is optimally adjusted so as to reduce the harmonic component generated by the distortion of the waveform of the output current of the inverter circuit. It is possible to obtain a distortion-free output current.

Further, according to the first and second embodiments, the step-up ratio of the step-up circuit (2) is a harmonic of the inverter output current regardless of fluctuations in the output voltage of the DC power source (1) and the system voltage. Since it is set to the lowest value within the range where components do not occur,
Higher efficiency than before can be obtained.

Third Embodiment A system interconnection power supply device of this embodiment shown in FIG. 6 includes a booster circuit (2) and an inverter circuit (3) having the same configurations as those of the first and second embodiments, and The positive side terminal of the first capacitor C1 and the positive side terminal of the second capacitor C2 forming the booster circuit (2) are connected to each other via an on / off switch SWo, and a coil L1 and a diode D1 are connected. A detour signal path is formed. An on / off control signal is supplied from the control circuit (6) to the on / off switch SWo.

The control circuit (6) has the same boost ratio control function as that of the first or second embodiment, and has a new function of reducing the loss due to the resistance of the coil L1 and the diode D1. Have That is, the control circuit (6)
In the step-up ratio control process, the third voltage detection signal V3 obtained from the third voltage detector (42) is compared with the above-mentioned step-up target voltage, and when both values are the same or the step-up target voltage is smaller. That is, when the boosting ratio is 1 or less, the switching operation of the switching element SW1 is stopped and the on / off switch SWo is turned on. When the two values are different and the boosting ratio exceeds 1, the switching operation of the switching element SW1 is started and the on / off switch SWo is turned off.

As a result, the output current of the DC power source (1) is directly supplied to the inverter circuit (3) through the on / off switch SWo during the period when the boosting ratio should be 1 or less. Therefore, in this period, the loss due to the resistance of the coil L1 and the diode D1 is zero.
When the boost ratio is set to exceed 1, the above first
As in the case of the embodiment or the second embodiment, the optimum boost target voltage is created, and the waveform distortion of the output current of the inverter circuit (3) is suppressed.

The description of the above embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof.
In addition, the configuration of each part of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

For example, in the second embodiment shown in FIG.
In the adder (71), instead of the boost target reference voltage value Vref,
It is also possible to input the boost target voltage signal MV2 'generated by the first amplifier (62) of the first embodiment shown in FIG. Further, the extraction of the harmonic components in the second embodiment is not limited to the hardware band pass filter circuit (67), but may be performed by the software of the microcomputer. Further, the on / off control of the on / off switch SWo in the third embodiment can be performed not only by the hardware control circuit (6) but also by the software of the microcomputer.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a grid interconnection power supply device of the present invention.

FIG. 2 is a block diagram showing a configuration of a circuit portion for performing a step-up ratio control operation of a step-up circuit in the control circuit of the first example.

FIG. 3 is a waveform diagram illustrating the principle of on / off control of a switching element provided in the booster circuit.

FIG. 4 is a block diagram showing a configuration of a circuit portion for performing a step-up ratio control operation of a step-up circuit in the control circuit of the second example.

FIG. 5 is a block diagram showing two configuration examples of a bandpass filter circuit according to a second embodiment.

FIG. 6 is a diagram showing an overall configuration of a grid interconnection power supply device according to a third embodiment.

FIG. 7 is a block diagram showing an overall configuration of a conventional system interconnection power supply device.

FIG. 8 is a diagram showing a general booster circuit.

FIG. 9 is a diagram showing a change in current flowing through a coil and an ON / OFF state of a switching element when the boost ratio is set to 2 in the boost circuit.

FIG. 10 is a diagram of the same as above when the step-up ratio is set to 4.

FIG. 11 is a diagram showing a waveform of a current flowing into the commercial power system when the output voltage of the booster circuit is sufficiently higher than the peak value of the system voltage.

FIG. 12 is a diagram of the same as above when the output voltage of the booster circuit drops.

[Explanation of symbols]

 (1) DC power supply (2) Boost circuit (3) Inverter circuit (4) First voltage detector (41) Second voltage detector (5) Current detector (6) Control circuit (8) Commercial power system SW1 switching Element SWo ON / OFF switch

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Maekawa 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (9)

[Claims] 1. A DC power supply is connected to a commercial power system via an inverter, and the inverter has a booster circuit for boosting an output voltage of the DC power supply, a control circuit for controlling a boosting ratio of the booster circuit, and a booster circuit. In a system interconnection power supply device provided with an inverter circuit that converts the output voltage of the inverter into an alternating current, the control circuit includes a detection unit that detects an electrical state quantity at an output end of the inverter circuit, and a detected electrical state. A signal processing means for creating a boost target voltage for suppressing the harmonic component contained in the output current of the inverter circuit to a certain level or less based on the amount; and an output voltage of the boost circuit to approach the boost target voltage, A system interconnection power supply device comprising: a step-up control means for controlling a step-up ratio of a step-up circuit. 2. The system interconnection power supply device according to claim 1, wherein the electrical state quantity is an output voltage of the inverter circuit. 3. The grid interconnection power supply device according to claim 1, wherein the electrical state quantity is an output current of the inverter circuit. 4. The grid interconnection power supply device according to claim 1, wherein the harmonic component is a frequency component that is an integral multiple of 2 or more of the system frequency. 5. A DC power supply is connected to a commercial power system via an inverter, and the inverter has a booster circuit for boosting an output voltage of the DC power supply, a control circuit for controlling a boosting ratio of the booster circuit, and a booster circuit. A voltage detector for detecting the output voltage of the booster circuit and a second voltage detector for detecting the output voltage of the inverter circuit. The control circuit boosts the voltage evaluation value based on the output signals of the first voltage detector and the second voltage detector with reference to a voltage evaluation value corresponding to the magnitude of the output voltage of the inverter circuit. A system interconnection power supply device comprising control means for controlling a step-up ratio so that a ratio of an output voltage of the circuit becomes a predetermined constant value. 6. The control means of the control circuit comprises: first calculating means for calculating a voltage evaluation value of the output voltage of the inverter circuit based on the output signal of the second voltage detector; and the calculated voltage evaluation value based on the calculated voltage evaluation value. Second computing means for multiplying a predetermined constant value to create a boost target voltage, third computing means for subtracting the boost target voltage from the output signal of the first voltage detector to create an error signal, and error signal 6. The system interconnection power supply device according to claim 5, further comprising a step-up ratio adjusting means for changing the step-up ratio in a direction in which the voltage decreases. 7. A DC power supply is connected to a commercial power system via an inverter, and the inverter has a booster circuit for boosting an output voltage of the DC power supply, a control circuit for controlling a boosting ratio of the booster circuit, and a booster circuit. In a system interconnection power supply device provided with an inverter circuit for converting the output voltage of the into an alternating current, comprising a current detector for detecting the output current of the inverter circuit,
The control circuit extracts a harmonic component that is an integer multiple of 2 or more of the system frequency of the inverter circuit from the output signal of the current detector, and a harmonic extraction unit that suppresses the extracted harmonic component to a certain level or less. A system interconnection power supply device comprising a control means for controlling a step-up ratio. 8. The control circuit comprises a voltage detector for detecting the output voltage of the booster circuit, and the control means calculates a signal evaluation value according to the magnitude of the output signal of the harmonic extraction means. Calculating means, second calculating means for performing a predetermined calculation on the calculated signal evaluation value to create a boost target voltage having a magnitude corresponding to the signal evaluation value, and the boost target voltage from the output signal of the voltage detector. 8. The grid interconnection power supply device according to claim 7, further comprising: third calculating means for subtracting the error signal to generate an error signal; and boosting ratio adjusting means for changing the boosting ratio in a direction in which the error signal decreases. 9. An input terminal and an output terminal of the booster circuit are connected to each other via a switch means capable of on / off control,
9. The grid interconnection power supply device according to claim 1, wherein the control circuit turns on the switch means and stops the boosting operation of the booster circuit during a period when the booster ratio of the booster circuit is 1. .