JP3354369B2 - Grid-connected power supply - Google Patents

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 supply such as a solar cell to a commercial power system via an inverter, and more particularly to a system having a booster circuit in front of an inverter circuit. The present invention relates to an interconnection power supply.

[0002]

2. Description of the Related Art In a grid-connected power supply device for converting an output voltage obtained from a DC power supply such as a solar cell into AC by an inverter and supplying the AC power to a commercial power system, it is necessary to supply power to the commercial power system. There is known a method of providing a booster circuit in an inverter to obtain a necessary voltage.

FIG. 7 shows the overall configuration of a conventional grid-connected power supply. As shown, the DC output voltage obtained from the solar cell (10) is first supplied to the booster circuit of the inverter (90).
The inverter circuit (30) of the inverter (90) is stepped up to a height that allows reverse power flow to the commercial power system (8) by (20).
Supplied to As a result, the input voltage of the inverter circuit (30) is converted into an alternating current, and the reverse power flows to the commercial power system (8). A control circuit (60) is connected to the booster circuit (20) and the inverter circuit (30), and the operation of the booster circuit (20) and the inverter circuit (30) is 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 boosting circuit performs a boosting operation by turning on / off the switching element SW, and the boosting ratio Vo / Vi changes according to the ON period of the switching element SW. For example, FIG.
As shown in FIG. 10, when the on-period and the off-period of the switching element SW are the same, the boosting ratio is set to 2, and as shown in FIG.
When the length is double, the boost ratio is set to 4.
As shown, the current IL flowing through the coil L in the boosting operation fluctuates around its average value Ia in accordance with the on / off of the switching element SW, and as the boosting ratio increases, the maximum value Imax of the current IL increases. However, the minimum value Imin will decrease. Here, the loss of the booster circuit tends to increase sharply 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. Will increase. From this, it can be said that setting the boosting ratio of the boosting circuit as low as possible is effective for improving the efficiency of the circuit.

In order to reversely flow the power boosted by the booster circuit to the commercial power system, as shown in FIG. 11, the output voltage V1 of the booster circuit has a value that is 1/2 of the peak value Vp of the system voltage V. Also need to be high. If the output voltage V1 of the booster circuit decreases and the half value thereof becomes lower than the peak value Vp of the system voltage V as shown in FIG.
The waveform of the current I flowing into the commercial power system has a distortion W near the peak point of the system voltage V as shown in FIG. In a commercial power system, for example, a power supply for 100 V is allowed to fluctuate in system voltage within a range of 101 ± 6 V in an operation regulation, and the peak value Vp of the system voltage V usually has some fluctuation. It is. Therefore, when the peak value Vp of the system voltage rises, there is a great possibility that the waveform distortion W occurs. Therefore, conventionally, as shown in FIG. 11, the boost target voltage of the boost circuit is set to a sufficient margin Vd from the peak value of the commercial power system voltage.
(50 to 60 V) to prevent the generation of harmonic components.

[0006]

However, in the conventional inverter, since the boost target voltage is set to a constant value with a sufficient margin as described above, it is necessary to suppress the waveform distortion of the output current of the inverter circuit. As a result, an unnecessarily high boosting ratio is set, which causes a problem that the efficiency of the boosting circuit is reduced. An object of the present invention is to suppress the waveform distortion of the output current of the inverter circuit by always controlling the boost target voltage of the boost circuit to an optimum value irrespective of the fluctuation of the system voltage. An object of the present invention is to provide an obtained system interconnection power supply device.

[0007]

According to the present invention, there is provided a grid-connected power supply device in which 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. And a control circuit for controlling a boost ratio of the booster circuit, and an inverter circuit for converting an output voltage of the booster circuit into an alternating current.

[0008] The characteristic configuration of the grid-connected power supply device is characterized in that the control circuit includes a detecting means for detecting an electric state quantity at an output terminal of the inverter circuit and a detected electric state quantity based on the detected electric state quantity. A signal processing means for generating a boost target voltage for suppressing a harmonic component included in an output current of the inverter circuit to a certain level or less, and a boost ratio of the boost circuit so that an output voltage of the boost circuit approaches the boost target voltage. And a boost control means for controlling the boost target voltage as the harmonic component increases. Specifically, the electric state quantity is an output voltage of the inverter circuit or an output current of the inverter circuit.

In the above system interconnection power supply of the present invention, by detecting the output voltage of the inverter circuit, that is, the system voltage, when the system voltage is high and there is a possibility that waveform distortion may occur in the output current, The boost ratio can be adjusted to a value corresponding to the system voltage. Therefore, no distortion occurs in the waveform of the output current of the inverter circuit. or,
By detecting the output current of the inverter circuit, a harmonic component included in the current flowing into the system can be directly detected, and the boost ratio can be adjusted so as to suppress the harmonic component. Therefore, an output current without waveform distortion is always obtained from the inverter circuit.

[0010] 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 waveform of the output current of the inverter circuit is a harmonic component that is an integral multiple of 2 or more of the system frequency. Therefore, waveform distortion can be effectively suppressed by adjusting the boost ratio so as to reduce these harmonic components.

Further, another system interconnection power supply device according to the present invention includes a DC power supply connected to a commercial power system via an inverter, wherein the inverter has a booster circuit for boosting an output voltage of the DC power supply, A control circuit for controlling a boost ratio of the circuit;
And an inverter circuit for converting the output voltage of the booster circuit into an alternating current.

[0013] A characteristic configuration of the grid-connected power supply device includes a first voltage detector for detecting an output voltage of the booster circuit;
A second voltage detector for detecting an output voltage of the inverter circuit, wherein the control circuit responds 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 for controlling a boost ratio so that a ratio of an output voltage of the booster circuit to the voltage evaluation value becomes a predetermined constant value based on the voltage evaluation value; To increase the ratio. As the voltage evaluation value, for example, an effective value can be adopted.

[0014] In the above system interconnection power supply of the present invention,
The control circuit includes a voltage evaluation value of an 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 higher than the output voltage of the booster circuit. When there is a possibility that waveform distortion may occur in the output current, the step-up ratio is increased to increase the output voltage of the step-up circuit. Therefore, no distortion occurs in the waveform of the output current of the inverter circuit.

Further, in another system interconnection power supply device according to the present invention, 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 boost ratio of the circuit;
And an inverter circuit for converting the output voltage of the booster circuit into an alternating current.

A characteristic configuration of the grid-connected power supply device includes a current detector for detecting an output current of the inverter circuit, and the control circuit determines the system frequency of the inverter circuit based on an output signal of the current detector. A harmonic extraction means for extracting a harmonic component of an integral multiple of the above, and a control means for controlling a boost ratio so as to suppress the extracted harmonic component to a certain level or less, with the increase of the harmonic component The boost ratio is increased.

In the above grid-connected power supply of the present invention,
Harmonic extraction means extracts harmonic components of an integral multiple of two or more of the system frequency caused by distortion of the waveform of the output current of the inverter circuit, and control means increases the boost ratio so as to suppress these harmonic components. Is adjusted, an output current without waveform distortion can always be obtained from the inverter circuit.

In a specific configuration of the system interconnection power supply,
The input terminal and the output terminal of the booster circuit are connected to each other via switch means capable of on / off control, and the control circuit turns on the switch means during a period when the boosting ratio of the booster circuit is 1, and The boosting operation of the booster circuit is stopped.

As described above, during the period when the boost ratio becomes 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 or the like of the circuit element constituting the booster circuit becomes zero.

[0020]

According to the grid-connected power supply of the present invention, the boost ratio of the booster circuit is set to the lowest optimum value within a range where no harmonic component is generated in the inverter output current regardless of the fluctuation of the system voltage. Can be controlled. As a result, while suppressing the waveform distortion of the output current of the inverter circuit, higher efficiency than in the related art can be obtained.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to FIGS.
A specific description will be given based on one embodiment with reference to the drawings. First Embodiment A grid-connected power supply according to a first embodiment shown in FIG.
The boosting ratio of the boosting circuit (2) is controlled based on the output voltage of the inverter circuit (3) constituting (9).

As shown in the figure, a DC power supply composed of a solar cell
(1) is connected to a commercial power system (8) via an inverter (9). The inverter (9) includes a booster circuit (2) that boosts a DC output voltage obtained from the DC power supply (1) to a height that allows reverse power flow to the commercial power system (8), and a booster circuit.
An inverter circuit (3) for converting the output voltage of (2) into AC and supplying the AC voltage to the commercial power system (8) is provided. A first voltage detector (4) for detecting the output voltage of the booster circuit (2) is provided upstream of the inverter circuit (3), and an inverter circuit is provided downstream thereof.
A second voltage detector (41) for detecting the output voltage of (3) and a current detector (5) for detecting the output current are connected, and a DC power supply (1) is provided upstream of the booster circuit (2). A third voltage detector (42) for detecting an output voltage is connected. Output terminals of the first, second, and third voltage detectors (4), (41), (42) and the current detector (5) are connected to a 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 AC and output.

The control circuit (6) is provided with first and second voltage detection signals V1, V2 from the first and second voltage detectors (4, 41).
, A switching signal for controlling the boosting operation of the booster circuit (2) is generated, 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 a configuration of a circuit portion of the control circuit (6) that performs a boost ratio control operation of the booster 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). In the effective value circuit (61), based on the second voltage detection signal V2, an effective value signal V2 'representing the effective value of the output voltage of the inverter circuit (3) is created and output to the first amplifier (62). . In the first amplifier (62), the effective value signal V2 'is multiplied by the gain M to generate a boost target voltage signal MV2', which is output to the subsequent stage. Here, the gain M is set so that the minimum required boost target voltage signal MV2 'is obtained with respect to the effective value signal V2' of the inverter circuit (3), for example.
Set to 1.7.

The boost 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 is output from the first voltage detection signal V1 to the boost target signal MV2'. The voltage signal MV2 'is subtracted to generate the original error signal E, which is output to the second amplifier (64). Second amplifier (64)
Is multiplied by the gain N, a reference error signal E 'is created and 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 by the triangular wave generating circuit (65) is compared with the reference error signal E ', and a switching signal that is turned on during a period when the triangular wave signal T is larger than the reference error signal E' is created. It is supplied to the switching element SW1.

FIGS. 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, FIG.
As described above, the reference error signal E 'gradually decreases. Accordingly, the ON period of the switching element SW gradually increases, and the step-up ratio increases. Conversely, when the system voltage gradually decreases, the reference error signal E 'gradually increases, and accordingly, the ON period of the switching element SW gradually shortens, and the step-up ratio decreases. Further, when the output voltage of the DC power supply (1) decreases due to a decrease in the amount of solar radiation or the like, the output voltage of the booster circuit (2) decreases due to this, so that the reference error signal E 'decreases. Along with this, the ON period of the switching element SW becomes longer, and the boosting ratio rises. Conversely, when the output voltage of the DC power supply (1) increases, the output voltage of the booster circuit (2) increases, so that the reference error signal E 'increases.
The ON period of the switching element SW is shortened, and the step-up ratio is reduced. As a result, the output voltage of the booster circuit (2) is always a constant ratio to the effective value of the system voltage (the voltage across the U-phase and V-phase in the case of a single-phase three-wire system), which is 1.7 in this embodiment.
Is adjusted so as to satisfy the ratio.

As described above, according to this embodiment, the DC power supply
If the output voltage or the system voltage of (1) fluctuates, the boost 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. Never.

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). The system power supply device controls the boosting ratio based on the output current of the inverter circuit (3). The configuration and operation of the boosting circuit (2) and the inverter circuit (3) are the same as those of the first embodiment shown in FIG. This is the same as the embodiment.

The control circuit (6) generates 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). The switching signal is supplied to the switching element SW1 of the booster circuit (2). This allows the booster circuit
The boosting operation of (2) is controlled. FIG. 4 shows a configuration of a circuit portion in the control circuit (6) for performing a boost ratio control operation of the boost circuit (2). As shown, the current detection signal I detected by the current detector (5) is first input to the band-pass filter circuit (67). In the band-pass filter circuit (67), a harmonic component is extracted, a harmonic current signal Io having a magnitude corresponding to the harmonic component is created, and output to a subsequent stage. Here, the harmonic component generated in the output current of the inverter circuit (3) is a harmonic component of an integral multiple of 2 or more of the system frequency, and among these, a harmonic component of an odd multiple of 3 or more is particularly large. The level of the harmonic component decreases as the frequency increases, and the harmonic components three and five times the system frequency are dominant. Therefore, when the system frequency is 60 Hz, the band-pass filter circuit (67) is provided by a band-pass filter (72) that passes only the component of 180 Hz as shown in FIG.
A band-pass filter (73) that passes a component of 80 Hz and a band-pass filter (74) that passes a component of 300 Hz
Can be connected in parallel. The harmonic current signal Io created in this manner is input to an effective value circuit (68) shown in FIG. 4, and a harmonic effective value signal Io 'representing the effective value is created, and the second subtractor ( 69).

In a second subtracter (69), a harmonic suppression target value Iref is subtracted from the harmonic effective value signal Io '.
(Io'-Iref) is created and output to the third amplifier (70). Here, the harmonic suppression target value Iref is
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 an adder (71) together with a boost target reference voltage value Vref, and these are added to generate a boost target voltage signal [G (Io'-Iref)]. +
Vref] is generated 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, the boost target voltage signal [G (Io '
−Iref) + Vref] is subtracted to generate an original error signal E, which is output to the second amplifier (64). In the second amplifier (64), the gain N is multiplied to generate a reference error signal E ', which is output to the comparator (66). In the comparator (66), the triangular wave signal T output by the triangular wave generation circuit (65) is compared with the reference error signal E ', and a switching signal that is turned on during a period 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 boost target voltage is optimally adjusted so as to reduce the harmonic components generated by the distortion of the output current waveform of the inverter circuit. An output current without distortion can be obtained.

Further, according to the first and second embodiments, the boost ratio of the booster circuit (2) increases the harmonics of the output current of the inverter irrespective of the fluctuation of the output voltage of the DC power supply (1) or the system voltage. Since it is set to the lowest value within the range where no component occurs,
Higher efficiency than before can be obtained.

Third Embodiment A system interconnection power supply 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. The positive terminal of the first capacitor C1 and the positive terminal of the second capacitor C2, which constitute the booster circuit (2), are connected to each other via an on / off switch SWo to connect the coil L1 and the diode D1. A bypass 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 step-up ratio control function as in the first embodiment or the second embodiment, and also has a new function for reducing losses due to the resistance of the coil L1 and the diode D1. Have. That is, the control circuit (6)
Compares the third voltage detection signal V3 obtained from the third voltage detector (42) with the above-mentioned step-up target voltage in the step-up ratio control process, and determines whether the two values are the same or the step-up target voltage is smaller. That is, when the boosting ratio becomes 1 or less, the switching operation of the switching element SW1 is stopped, and the on / off switch SWo is turned on. If the two values are different and the boost 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, during the period when the boost ratio should be 1 or less, the output current of the DC power supply (1) is supplied directly to the inverter circuit (3) via the on / off switch SWo. Therefore, during this period, the loss due to the resistance of the coil L1 and the diode D1 becomes zero.
When the boost ratio is set to be more than 1, the first
In the same manner as in the embodiment or the second embodiment, an optimal 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 component in the second embodiment is not limited to the band pass filter circuit (67) of hardware, but can be performed by software of a 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 illustrating an overall configuration of a system interconnection power supply device according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a circuit portion that performs a boosting ratio control operation of a boosting circuit in the control circuit of the first embodiment.

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

FIG. 4 is a block diagram showing a configuration of a circuit portion for performing a boost ratio control operation of a boost circuit in a control circuit of a second embodiment.

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

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

FIG. 7 is a block diagram illustrating an entire configuration of a conventional grid-connected power supply device.

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

FIG. 9 is a diagram illustrating a change in a current flowing through a coil and an on / off state of a switching element when a boost ratio is set to 2 in the booster circuit.

FIG. 10 is the same drawing when the boost ratio is set to 4;

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

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

[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. (56) References JP-A-6-332554 (JP, A) JP-A-62- 200413 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 3/00-5/00 H02M 7/48

Claims (9)

(57) [Claims] 1. A DC power source is interconnection to the commercial power system through an inverter, the inverter includes a booster circuit for boosting an output voltage of the DC power supply, a control circuit for controlling the boosting ratio of the boosting circuit in the grid interconnection power supply and the inverter circuit is provided for converting the AC output voltage of the booster circuit, wherein the control circuit includes a detection means for detecting an electrical quantity of state at the output of the inverter circuit, detects based on the electric state quantity is, a signal processing means for generating a boost target voltage for suppressing the harmonic components included in the output current of the inverter circuit at a constant level or less, the output voltage of the booster circuit and the as close to boost target voltage, and a boost control means for controlling a boosting ratio of said booster circuit, the high
A grid-connected power supply device characterized in that the boost target voltage is increased with an increase in a harmonic component . 2. The grid-connected power supply according to claim 1, wherein said electric state quantity is an output voltage of said inverter circuit. 3. A system interconnection power supply device according to claim 1 wherein the electrical state variable is an output current of the inverter circuit. 4. The grid-connected power supply according to claim 1, wherein the harmonic component is a frequency component that is an integral multiple of two or more of a system frequency. 5. A DC power supply is interconnection to the commercial power system through an inverter, the inverter includes a booster circuit for boosting an output voltage of the DC power supply, a control circuit for controlling the boosting ratio of the boosting circuit in the grid interconnection power supply and the inverter circuit is provided for converting the AC output voltage of the booster circuit, a first voltage detector for detecting an output voltage of the booster circuit,
The size of said second voltage detector comprises detecting an output voltage of the inverter circuit, said control circuit based on the output signal of the first voltage detector and the second voltage detector, the output voltage of the inverter circuit based on the voltage evaluation value corresponding to, as the ratio of the output voltage of the booster circuit to said voltage evaluation value becomes a predetermined constant value, and a control means for controlling the step-up ratio, the
The boost ratio increases as the output voltage of the inverter circuit increases.
A grid-connected power supply device characterized by being added . Control means wherein said control circuit includes: a first calculating means for calculating a voltage evaluation value of the output voltage of the inverter circuit based on an output signal of said second voltage detector, said voltage rating calculated creating a second calculating means for creating the <br/> boost target voltage by multiplying the predetermined constant value to the value, an error signal by subtracting the boost target voltage from the output signal of the first voltage detector 6. The system interconnection power supply device according to claim 5, further comprising: a third calculating means for performing the operation; and a boosting ratio adjusting means for changing a boosting ratio in a direction in which the error signal decreases. 7. DC power is interconnection to the commercial power system through an inverter, the inverter includes a booster circuit for boosting an output voltage of the DC power supply, a control circuit for controlling the boosting ratio of the boosting circuit in the grid interconnection power supply and the inverter circuit is provided for converting the AC output voltage of the booster circuit, comprising a current detector for detecting an output current of the inverter circuit, the control circuit, said current detector a harmonic extraction unit from the output signal for extracting two or more integral multiple of the harmonic components of the system frequency of the i <br/> inverter circuit, so as to suppress the extracted the harmonic component below a predetermined level, the and control means for controlling the step-up ratio, before with the increase of the harmonic component
System interconnection power supply apparatus characterized by increasing the serial step-up ratio. Wherein said control circuit comprises a voltage detector for detecting an output voltage of the booster circuit, wherein, the signal evaluation according to the magnitude of the output signal of the <br/> harmonic extracting means a first calculating means for calculating a value, and a second arithmetic means for generating said temperature <br/> pressure target voltage having a magnitude corresponding to the signal evaluation value by applying a predetermined arithmetic operation to calculate the signal evaluation value , comprises a third arithmetic means for creating an error signal by subtracting the boost target voltage from the output signal of the voltage detector, and a step-up ratio adjusting means for the error signal alters the step-up ratio in a direction to decrease The grid-connected power supply according to claim 7. 9. input and the output of the boosting circuit is connected to each other via a switch means capable of ON / OFF control, wherein the control circuit, the on period during which the step-up ratio of the step-up circuit becomes 1 9. The system interconnection power supply device according to claim 1, wherein the switch means is turned on and the boosting operation of the booster circuit is stopped.