JPH0998539A - System interconnection inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sense easily the separate driving of an inverter through a simple configuration by sensing the separate driving of the inverter through the cooperation of a frequency-abnormality sensing means with a phase advancing means. SOLUTION: Into the output side of a band-pass filter 203 for determining the waveshape of a reference current Isref associated with an AC output current Is, a phase advancing circuit 204 for determining the phase of the reference current Isref is inserted to drive an inverter 20 in the state of a leading power factor. Thereby, the frequency increase of an AC voltage Vs when the inverter 20 is driven separately is sensed by an over-frequency sensor 27. In this case, the over-frequency can be sensed enough by the function of a general purpose over-frequency sensor 27 and the separately driving state of the inverter 20 is sensed surely to stop it. Therefore, its separate driving can be sensed easily by a simple configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grid interconnection inverter device used in connection with a commercial power grid.
The present invention relates to a grid interconnection inverter device that can reliably detect an islanding operation without performing complicated control to prevent an islanding state and suppress a voltage rise on the commercial power grid side during reverse power flow. is there.

[0002]

2. Description of the Related Art Conventionally, in a dispersed power source such as a photovoltaic power generator connected to a commercial power system through an inverter device, a dispersed power source (inverter device) on the solar power generator side
When it is in an isolated operation state, the high voltage boosted by a transformer or the like is applied to the commercial power system side, which may impair the safety of restoration work.

Therefore, detecting and preventing the isolated operation of the distributed power supply including the DC power supply and the inverter is a very important problem from the viewpoint of ensuring safety. FIG. 6 is a configuration diagram schematically showing a conventional grid interconnection inverter device described in, for example, Japanese Patent Application Laid-Open No. 6-31164. In this case, in the interconnection state between a commercial power system and a solar power generation device. , A function of detecting an isolated operation of a photovoltaic power generation device (inverter device) including an inverter.

In the figure, 1 is a photovoltaic power generator, 3 is a variable load circuit connected to the output terminal of the photovoltaic power generator 1 to detect the independent operation of the photovoltaic power generator 1, and 4 is supplied with AC power. A load 5 is a commercial power system that forms an interconnection system in association with the solar power generation device 1, and 6 is drawn between the solar power generation device 1 and the commercial power system 5 to supply AC power to the load 4. It is a distribution line.

Although not shown, a switch for disconnecting the photovoltaic power generator 1 including the inverter 20 is inserted in the distribution line 6, and the variable load circuit 3 operates the photovoltaic power generator 1 independently. When the state is detected, the solar power generation device 1 is disconnected from the load 4.

The solar power generation device 1 comprises a solar cell 10 and an inverter 20 having a DC terminal connected to the solar cell 10. The variable load circuit 3 includes a switching element 31 having one end connected to the AC terminal of the inverter 20, that is, the distribution line 6, a capacitor 32 inserted between the other end of the switching element 31 and the ground, and a switching element 31. And a pulse signal generator 33 for inputting the pulse signal Ssw.

Next, in the conventional system interconnection inverter device shown in FIG. 6, the operation of the voltage source current control type inverter 20 connected to the commercial power supply system 5 will be described. Normally, the DC power generated by the solar cell 10 is
After being converted into AC power by the inverter 20, it is supplied to the load 4 via the distribution line 6.

At this time, since the inverter 20 is also connected to the commercial power system 5 via the distribution line 6, the commercial power system 5 supplies the output power of the inverter 20 smaller than the load power. , Power is being exchanged. However, when the commercial power system 5 is cut off, the inverter 20 continues to supply the AC power to the load 4 independently, and the so-called solar power generation device 1 is in an isolated operation state.

Since such an isolated operation state may impair safety as described above, it is necessary to promptly detect the isolated operation state and stop the inverter 20.
However, when the output power of the inverter 20 is balanced with the load power, it is very difficult to detect the islanding operation state of the solar power generation device 1.

Therefore, the variable load circuit 3 is provided on the distribution line 6, the switching element 31 is opened / closed by the switching pulse signal Ssw from the pulse signal generator 33, and the capacitor 32 is de-energized at regular intervals. As a result, the load power factor viewed from the inverter 20 changes and the inverter 20
Output frequency changes in synchronism with the on / off of the capacitor 32, so that it is possible to detect this frequency fluctuation and detect the islanding operation state.

The commercial power system 5 is the solar power generation system 1
When the capacitor 32 is connected to, the output frequency of the inverter 20 does not change even if the capacitor 32 is turned on and off. When the islanding state is detected in this way, the switch (not shown) on the distribution line 6 is opened (OFF),
The solar power generation device 1 is disconnected from the load 4.

Further, instead of providing the variable load circuit 3,
It is known that, even when the output current phase is periodically changed in the control of the inverter 20, the islanding operation state can be similarly detected.

Further, for example, as disclosed in Japanese Patent Laid-Open No. 5-336666, the output power of the inverter 20 is periodically changed, and the islanding operation state is detected by the frequency change synchronized with the output power change. It is known that it is also possible to prevent islanding.

[0014]

As described above, the conventional grid interconnection inverter device requires various configurations for detecting the isolated operation state. For example, when the variable load circuit 3 is used. However, there was a problem that it would increase the cost.

Further, when the current phase of the inverter 20 is periodically changed, it is necessary to set the fluctuation period short in order to detect the islanding operation quickly, so that the frequency fluctuation becomes small and detection is difficult. And the frequency on the commercial power system 5 side changes slightly during normal operation (disturbance)
However, there is a problem that erroneous detection may occur.

The present invention has been made to solve the above-mentioned problems, and it is possible to reliably detect the isolated operation without performing complicated control to prevent the isolated operation state and to prevent the isolated flow. An object of the present invention is to obtain a grid interconnection inverter device capable of suppressing a voltage rise on the commercial power grid side.

[0017]

An inverter device for grid interconnection according to claim 1 of the present invention comprises an inverter connected to a DC power source and an inverter control means for controlling the inverter, and is connected to a commercial power system. In an inverter device for system interconnection that supplies power to a load by a system, a phase lead means for operating the inverter at a constant lead power factor and a frequency abnormality that stops the inverter when an abnormality in the output frequency of the inverter is detected. The detection means is provided, and the frequency abnormality detection means cooperates with the phase advance means to form an isolated operation detection means for detecting the isolated operation of the inverter and disconnecting the output of the inverter.

According to a second aspect of the present invention, in the grid interconnection inverter device according to the first aspect, the inverter comprises a voltage type current control type inverter, and the phase advance means is connected in series within the inverter control means. It is composed of a phase advance circuit inserted in.

Further, in the grid interconnection inverter device according to a third aspect of the present invention, in the first aspect, the inverter control means determines the AC output waveform of the inverter by passing the commercial frequency of the commercial power system. The phase lead means includes a pass filter, and is configured by the set value of the first-order lag time constant in the band pass filter.

According to a fourth aspect of the present invention, in the grid interconnection inverter device according to the third aspect, the bandpass filter includes two analog operational amplifiers that are connected in series to form a two-stage primary delay system. Including, the phase advance means is 2
It is configured by the setting value of the first-order lag time constant of the succeeding analog operational amplifier of the two analog operational amplifiers.

According to a fifth aspect of the present invention, in the grid interconnection inverter device according to the third aspect, the bandpass filter is a digital filter using a digital signal processor, and the phase advance means is the digital filter. It is built in.

According to a sixth aspect of the present invention, in the grid interconnection inverter device according to any one of the first to fifth aspects, the advance power factor of the inverter is a commercial power during normal interconnection operation. The value is set to a value that suppresses the AC voltage during reverse power flow that is fed to the system side to a predetermined regulation value.

According to a seventh aspect of the present invention, in the grid interconnection inverter device according to any one of the first to fifth aspects, the advance power factor of the inverter is set to about 0.95. Is.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a first embodiment of the present invention, in which 1, 4, 6, 6, and 20 are the same as those described above. In addition, the solar cell 10 may be configured by another fuel cell or a DC power generation facility such as a storage battery.

A switch 23 is inserted in the distribution line 6 between the inverter 20 and the load 4, and disconnects the output power of the inverter 20 from the commercial power system 5 when the islanding state is detected. Reference numeral 25 is a current transformer provided on the distribution line 6, and detects the AC output current Is supplied from the inverter 20. An overfrequency detector 27 opens the switch 23 by detecting an increase in the output frequency of the inverter 20, that is, an overfrequency of the AC voltage Vs, and constitutes a frequency abnormality detecting means. IL is a load current (usually in a delay phase with respect to the AC voltage Vs) supplied from the distribution line 6 to the load 4.

Reference numeral 200 is an AC output current I of the inverter 20.
s and the AC voltage Vs of the distribution line 6 and the like, which is an inverter control means for performing PWM control of the inverter 20, and includes the following circuit components 201 to 207. 201
Is a power control circuit for determining the output power of the inverter 20, and is constituted by a maximum power follow-up control circuit or a constant DC voltage control circuit, and outputs a DC level signal for determining the magnitude of the AC output current Is. To do.

Reference numeral 202 is a transformer for detecting the AC voltage Vs on the distribution line 6, and 203 is a bandpass filter (BPF) for removing the high frequency component from the AC voltage Vs and extracting the fundamental wave component Vs' (only the sine waveform). , 204 is the fundamental wave component V
The phase of s'is advanced by the phase difference θ and advances to the fundamental wave (Vs'
This is a phase advance circuit that outputs + θ).

Reference numeral 205 denotes an AC output current I of the inverter 20.
Reference current Isr that determines the magnitude, waveform and phase of s
This is a multiplier that generates ef, and obtains the reference current Isref by multiplying the DC level signal from the power control circuit 201 and the lead fundamental wave (Vs ′ + θ) from the phase lead circuit 204. Reference numeral 206 is the reference current Isref and the AC output current I
It is a subtracter that calculates a current deviation ΔIs (= Isref-Is) from s.

Reference numeral 207 is a PWM that outputs a PWM control signal CP to the inverter 20 based on the current deviation ΔIs.
This is a waveform generation circuit, which drives the inverter 20 by the PWM control signal CP to generate an AC output current Is
To follow the reference current Isref at high speed.

The AC voltage Vs detected by the transformer 202 in the inverter control means 200 is also input to the overfrequency detector 27. Although not shown, the detection signal from the over-frequency detector 27 is output by the switch 2
3 is not only opened, but also input to the PWM waveform creation circuit 207 in the inverter control means 200, for example, to disable the PWM waveform creation circuit 207 and stop the inverter 20.

As shown in FIG. 1, a phase lead circuit 204 for determining the phase of the reference current Isref is inserted at the output side of the bandpass filter 203 for determining the waveform of the reference current Isref with respect to the AC output current Is. Then, by increasing the operation of the inverter 20 to the power factor, the frequency increase of the AC voltage Vs during the isolated operation on the inverter 20 side is detected by using the overfrequency detector 27, and the switch 23 is shut off to perform the isolated operation. It is designed to prevent the situation.

FIG. 2 is an explanatory diagram showing the mutual vector relationship of the AC output current Is, the AC voltage Vs, and the load current IL. The phase difference φ of the load current IL with respect to the AC voltage Vs.
Is a lagging phase, and the AC output current Is is a leading phase by a phase difference θ. IL 'has a load power factor PF of 1.0.
It is the load current in the case of (no phase delay with respect to the AC voltage Vs).

FIG. 3 is a characteristic diagram showing changes in the frequency f when the load power factor PF is changed during the independent operation of the inverter 20, and the load power factor PF and the AC voltage Vs obtained experimentally.
Shows the relationship with the frequency f. In FIG. 3, when the load 4 is an inductive load and is in a lagging phase (the load power factor PF is smaller than 1.0), the frequency f is high, and the load 4 is a capacitive load and is in a leading phase. When the load power factor PF is smaller than 1.0, the frequency f becomes low.

Next, the operation of the first embodiment of the present invention shown in FIG. 1 will be described with reference to FIGS. 2 and 3. First, at the time of steady interconnection operation, the switch 23 is closed (ON), and the load current IL for the load 4 is
Is supplied from both the power generation device including the solar cell 10 and the inverter 20 and the commercial power system 5 in an interconnected manner.

The power control circuit 201 also determines the magnitude of the AC output current Is of the inverter 20, and the transformer 20
2 and the bandpass filter 203 determine the waveform of the AC output current Is based on the fundamental wave component Vs ′ obtained from the AC voltage Vs, and the phase lead circuit 204 determines the fundamental wave component Vs.
Determine the phase difference θ for s'. As a result, the AC output current Is of the inverter 20 during the steady operation is phase difference θ with respect to the phase of the AC voltage Vs by the PWM control signal CP.
It is controlled to the advanced state.

At this time, the vector relationship between the load current IL and the AC output current Is with respect to the AC voltage Vs is as shown in FIG. 2, and the load current I determined by the load power factor PF.
The phase of L is normally behind the AC voltage Vs by a phase difference φ. Even if the maximum value is taken into consideration, the load power factor PF only approaches 1.0 in FIG. 3, and the advance power factor cannot be the load of a general consumer.

Although the power factor of the customer is set so as not to advance, for example, in a high-voltage customer or the like, a power factor improving capacitor is left on and the power factor advances at night. Can be. However, in the case of the inverter 20 for photovoltaic power generation, since there is no solar cell output at night, it is operated only in the daytime, so there is no need to consider the possibility of the advance power factor at night.

During the steady interconnection operation, the phase of the AC output current Is is the same as the phase of the AC voltage Vs. On the other hand, when the commercial power system 5 is cut off, the inverter 20
Is in an isolated operation state, and the change characteristic of the frequency f at this time in an isolated operation is experimentally obtained using the load power factor PF as a parameter, as shown in FIG. In this case, the inverter 20 is in an operating state with a power factor of 1.0.

In FIG. 3, the frequency f of the AC voltage Vs
Is high when the load 4 is the delayed power factor (the load power factor PF is on the delayed side), and conversely, the advanced power factor (the load power factor PF is on the advanced side).
Then it will be lower. Further, the change of the frequency f is larger on the delay power factor side. The frequency f increases when the load power factor PF is the delay power factor, for example, for the following reason.

That is, the inverter 20 supplies the load current IL to the load 4, but since the load current IL has a delay power factor, the phase of the AC voltage Vs is relatively only the phase difference φ as shown in FIG. It will be advanced. The phase of the AC output current Is of the inverter 20 is further advanced by the phase difference φ because the phase of the AC voltage Vs is used as a reference. Therefore,
Since the phase of the AC output current Is acts to advance,
The frequency f of the AC voltage Vs gradually increases.

The overfrequency detecting operation during the isolated operation will be specifically described below. As mentioned above, the inverter 2
The AC output current Is of 0 is controlled by the action of the phase advance circuit 204 in a phase that leads the AC voltage Vs by the phase difference θ. Here, under the condition that the load power factor PF is set to 1.0 at the maximum (the leading load cannot be present), the state in which the frequency rise is most unlikely is as shown in FIG.
This is when the load power factor PF is 1.0.

However, due to the action of the phase lead circuit 204, the inverter control means 200 leads the inverter 2 by a phase difference θ with respect to the phase of the AC voltage Vs.
Since the AC output current Is of 0 is about to flow, the phase of the AC output current Is gradually advances in a time series.

Therefore, as described above, the inverter 2
0 is the operation method with a power factor of 1.0, and the load 4 is completely equivalent to the action when the load is a delayed load (the load power factor PF is delayed) (see FIG. 3), and the AC voltage Vs is caused by the phase lead of the AC output current Is. Frequency f increases.

In this way, the frequency f of the AC voltage Vs increases in accordance with the progress of the AC output current Is, so that the overfrequency detector 27 can easily detect the overfrequency state caused by the isolated operation state of the solar power generation device 1. Then, the inverter 20 is stopped by the over-frequency detection signal, and the switch 23 is shut off (OFF) to prevent the islanding operation immediately.

In this way, the inverter 20 is connected to the AC voltage V
By operating with a lead power factor having a constant phase difference θ with respect to s, the load power factor PF is 1.0 at the maximum when viewed from the operation of the inverter 20 when the solar power generation device 1 is operating alone. However, the load power factor PF apparently has the action of the delay power factor.

That is, even when the inverter 20 is operated at a forward power factor during the continuous interconnection operation, and the power factor PF of the load 4 is 1.0 when the photovoltaic generator 1 is in the independent operation state. As seen from the inverter 20, the load 4 is set as an apparently delayed load, and the rise of the frequency f is manifested to reliably detect the isolated operation state. As a result, the output frequency f of the inverter 20 rises, so that the overfrequency detector 27, which is provided for general purpose, can sufficiently detect the overfrequency, and reliably detect the isolated operation state and stop it. Can be made.

Since the frequency f of the AC voltage Vs during the islanding operation rises quickly, the overfrequency can be detected within 1 second after entering the islanding state. Further, since the change in the frequency f is large, there is no erroneous detection of the disturbance of the commercial power system 5 during the steady interconnection operation.

The phase difference θ of the AC output current Is advanced and controlled by the phase advance circuit 204 is, for example, 10
Although it is sufficient to set the angle to about 0 °, it is desirable to set the phase difference θ (about 18 °) so that the advance power factor of the inverter 20 during the steady operation is about 0.95 with a margin. That is, when the inverter 20 is operated at a leading power factor of about 0.95, the operating efficiency of the inverter 20 and the like hardly change. Therefore, with the above detection method, the conventional performance can be maintained and the independent operation can be performed easily and reliably. Driving can be prevented.

In addition, operating the inverter 20 at the advanced power factor causes a delay load when viewed from the commercial power system 5, so that the power factor at the power receiving point of the commercial power system 5 is advanced. It does not bring about the effect.

Further, by operating the inverter 20 at a constant forward power factor, during reverse power flow during normal interconnection operation (the output power of the inverter 20 exceeds the load power required by the load 4, the commercial power system 5 It has an effect of preventing the rise of the AC voltage Vs in the state of being fed to the side), and also has an effect as a measure for suppressing the voltage rise. That is, in general, when the impedance (including reactance) of the distribution line 6 is high, the AC voltage Vs rises during reverse power flow during steady interconnection operation, and overvoltage is applied to various devices forming the load 4. The harmful effect such as being applied becomes large.

However, as described above, if the inverter 20 is operated at a leading power factor of about 0.95, the lagging power factor will be seen from the viewpoint of the commercial power system 5, so that the reactance drop of the distribution line 6 will occur. Therefore, the rise of the AC voltage Vs can be suppressed, and the overvoltage is not applied to the load 4.
The reactance drop Vx of the AC voltage Vs is based on the reactive power, and is represented by the following equation (1), where R is the resistance value of the distribution line 6 and X is the reactance.

Vx = Is · R + Is · X · sin θ (1)

As is clear from the equation (1), as the phase difference θ becomes smaller and the operating power factor of the inverter 20 approaches 1.0, the reactance drop becomes smaller and the AC voltage Vs becomes smaller.
Rises. However, by setting the operating power factor of the inverter 20 to about 0.95 (θ = about 18 °), in most cases, the regulation value for preventing overvoltage can be cleared. If the regulation value cannot be cleared, the operating power factor of the inverter 20 may be set to a smaller value, for example, about 0.9 (corresponding to about θ = 26 °).

Embodiment 2. Although the phase advance circuit 204 is provided in order to advance the phase of the AC output current Is with respect to the AC voltage Vs by the phase difference θ in the first embodiment, the band pass filter 203 is provided without the phase advance circuit 204. A phase advance function may be included. A second embodiment of the present invention that does not require the phase advance circuit 204 will be described below with reference to the drawings.

FIG. 4 is a block diagram showing a bandpass filter 203 according to the second embodiment of the present invention.
2, 203 and 205 are the same as described above. In FIG. 4, the bandpass filter 203 is a two-stage analog operational amplifier 203a and 203b connected in series.
First-order lag circuit including an analog operational amplifier 203a
And 203b, and a subtractor 203c inserted between the two.

The output terminal of the transformer 202 is connected to the input terminal of the analog operational amplifier 203a and the non-inverting input terminal of the subtractor 203c, respectively.
The output terminal of 3a is connected to the inverting input terminal of the subtractor 203c, and the output terminal of the subtractor 203c is connected to the input terminal of the analog operational amplifier 203b.

Each analog operational amplifier 203a and 20
The first-order lag time constants T ₁ and T ₂ of 3b determine the lower limit ω _L and the upper limit ω _H of the passband of the bandpass filter 203, and are represented by the following equations (2) and (3), respectively.

Ω _L = 1 / (2πT ₁ ) (2) ω _H = 1 / (2πT ₂ ) (3)

Here, the analog operational amplifier 203 in the preceding stage
Assuming that the transfer function Ga of a is 1 / (1 + T ₁ S), the transfer function Gc through the subtractor 203c is expressed by the following equation (4).

Gc = 1-Ga = 11-1 / (1 + T ₁ S) = T ₁ S / (1 + T ₁ S) (4)

Also, the analog operational amplifier 203b in the subsequent stage
If the transfer function Gb of (1) is 1 / (1 + T ₂ S), the overall transfer function G (s) of the bandpass filter 203 is expressed by the following equation (5).

G (s) = {T ₁ S / (1 + T ₁ S)} × {1 / (1 + T ₂ S)} (5)

FIG. 5 is a Bode diagram showing the gain G and the phase difference θ of the bandpass filter 203 represented by the equation (5) as a characteristic diagram for the angular frequency ω.

[0064] In FIG. 5, the horizontal axis represents in common logarithm, the solid line characteristic curve before changing the constant T ₂ time, the broken line indicates the characteristic curve after changing the constant T ₂ time. Also,
ω o is the commercial angular frequency, ω _L and ω _H are the lower and upper limits of the pass band of the band pass filter 203, ω _H ′ is the upper limit of the pass band after changing the time constant T ₂ , and θ ′ is the time constant T ₂
Is the phase difference at the commercial angular frequency ωo after the change. Here, the lower limit ω _L and the upper limit ω _H (see the solid line) set by the time constants T ₁ and T ₂ are expressed by the following equations (6) and (7).
Shall be represented by.

Ω _L = ω o / 2 (6) ω _H = 2 · ω o (7)

Each time constant T such that equations (6) and (7) are obtained.
_{When 1} and T ₂ are determined, the phase difference θ at the commercial angular frequency ωo becomes 0 as shown by the solid line in FIG. On the other hand, when the time constant T ₂ is determined so that the upper limit of the filter pass band becomes a value ω _H ′ larger than ω _H , the characteristic curve of the gain G and the phase difference θ changes as shown by the broken line, and the commercial angular frequency ω o
In, the target waveform of the AC output current Is of the inverter 20 is advanced by the phase difference θ ′.

At this time, the phase difference θ'is set within the range of 18 ° to 26 °, and cos θ'has a value within the range of 0.9 to 0.95.

As described above, in the original function of the bandpass filter 203, the phase advance function can be realized easily and at low cost only by changing the first-order delay time constant T ₂ of the analog operational amplifier 203b. Therefore,
Even if the phase advance circuit 204 (see FIG. 1) is not installed,
The same effect as the above can be exhibited.

Embodiment 3 In the second embodiment, the band-pass filter 203 having the phase advance function is the analog operational amplifier 203a and 203b. However, the band-pass filter 203 may be a digital filter using a DSP (digital signal processor). In this case, since the processing can be performed only by digital calculation, the accuracy of detecting the islanding operation is improved. In addition, since productivity is improved, further cost reduction can be realized.

As described above, according to the present invention, the advance power factor (about 0.95) of the inverter 20 due to the constant phase difference θ is set.
By operating the inverter 2 even if the load power factor PF is 1.0 in the independent operation, the load has an apparent delay power factor when viewed from the inverter 20, and the inverter 2
The output frequency f of 0 greatly increases. Therefore, the function of the overfrequency detector 204 has an effect of being able to easily detect the islanding operation with a simple configuration and obtain an inexpensive and highly accurate grid interconnection inverter device.

Further, by operating the inverter 20 at a forward power factor, it is possible to suppress an abnormal rise in the AC voltage Vs that occurs during reverse power flow during normal interconnection operation. Also,
As a phase lead function in the inverter control means 200 for leading the inverter 20 into the power factor, one constant (time constant T in the band pass filter 203 for creating the current waveform reference).
By changing ₂ ), the phase advance function can be easily realized at low cost.

Furthermore, by using a digital filter using a DSP as the bandpass filter 203, it is possible to improve the detection accuracy of the isolated operation state and further reduce the cost.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between an AC voltage according to the first embodiment of the present invention, an AC output current of an inverter, and a load current as a vector.

FIG. 3 is a characteristic diagram showing experimental data on the relationship between load power factor and frequency according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a bandpass filter according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram showing in a Bode diagram the relationship between the gain and the phase difference of the bandpass filter with respect to the angular frequency according to the second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a conventional grid interconnection inverter device.

[Explanation of symbols]

1 solar power generation device, 4 loads, 5 commercial power system, 6
Distribution line, 10 solar cell (DC power supply), 20 inverter, 23 switch, 25 current transformer, 27 overfrequency detector (frequency abnormality detection means), 200 inverter control means, 202 transformer, 203 bandpass filter, 2
03a, 203b analog operational amplifier, 204 phase lead circuit, f frequency, _IL load current, Is AC output current, T ₁ , T ₂ first-order lag time constant, Vs AC voltage,
θ, θ ′ Phase difference, ωo Commercial angular frequency.

Claims (7)

[Claims] 1. An inverter connected to a DC power supply, and inverter control means for controlling the inverter,
In a grid interconnection inverter device that feeds power to a load by linking with a commercial power grid, phase lead means for operating the inverter at a constant lead power factor, and when an abnormality in the output frequency of the inverter is detected A frequency abnormality detecting means for stopping the inverter is provided, and the frequency abnormality detecting means cooperates with the phase advance means,
An inverter device for grid interconnection, comprising an islanding operation detecting means for detecting an islanding operation of the inverter and disconnecting an output of the inverter. 2. The inverter is composed of a voltage type current control type inverter, and the phase advance means is composed of a phase advance circuit inserted in series in the inverter control means. 1. The grid interconnection inverter device according to 1. 3. The inverter control means includes a bandpass filter that passes a commercial frequency of the commercial power system to determine an AC output waveform of the inverter, and the phase advance means includes a primary filter in the bandpass filter. The grid interconnection inverter device according to claim 1, wherein the delay time constant is configured by a set value. 4. The bandpass filter includes two analog operational amplifiers that are connected in series to form a two-stage first-order lag system, and the phase lead means is an analog of a latter stage of the two analog operational amplifiers. 4. The grid interconnection inverter device according to claim 3, wherein the operational amplifier is constituted by a set value of a first-order lag time constant. 5. The system interconnection according to claim 3, wherein the bandpass filter is composed of a digital filter using a digital signal processor, and the phase advance means is incorporated in the digital filter. Inverter device. 6. The advance power factor of the inverter is set to a value that suppresses an AC voltage during reverse power supply to the commercial power system side during normal interconnection operation to a predetermined regulation value. The grid interconnection inverter device according to any one of claims 1 to 5, wherein 7. The advance power factor of the inverter is 0.95.
The inverter device for grid interconnection according to any one of claims 1 to 5, wherein the inverter device is set to a certain degree.