JP2001042957A - System cooperation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the power factor of a system load and to suppress higher harmonics when multiple inverters are provided. SOLUTION: A power source adjusting device 10 decides the power rate of the system load 66 by a power factor decision circuit 72 and places a operation-stopping inverter 14 in operation when the power factor decreases. Higher harmonic components are then extracted by a BEF 88 from a load current (i) and inverted in phase by a phase inverting circuit 84 to outputs a current signal Irω. The inverter placed in operation switches according to this current signal to supply the inreactive power to be consumed by the system load to the system load and cancel higher harmonics generated by the system load by this output current, thereby improving the power factor of the system load which is viewed from a system power source 16 and suppress higher harmonics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection system for converting electric power generated by power generation means such as a solar cell into electric power corresponding to a system power supply by an inverter and outputting the converted electric power.

[0002]

2. Description of the Related Art In a system interconnection system, DC power generated by a power generation device such as a photovoltaic power generation device is converted by an inverter into AC power corresponding to the system power supply, and regenerated to the system power supply. At this time, the inverter used in the grid connection system prevents the isolated operation due to the power failure of the grid power supply, and also performs the grid connection protection against overvoltage, undervoltage, frequency rise, and frequency drop of the grid power supply.

On the other hand, the inverter can operate most efficiently when the rated power is output. However, in a power generator using a solar cell, the power generated varies depending on the amount of solar radiation and the like. When the power is less than the rated power, the maximum power follow-up control (MPPT control) is performed so that the output efficiency becomes highest according to the change in the generated power.

In an inverter having a large output power,
If the input power is too low with respect to the rated power, the output efficiency will be extremely reduced. For this reason, in a system interconnection system, a proposal has been made to connect multiple inverters in parallel and set the number of inverters to be operated according to the input power so that the inverter can operate efficiently even when the generated power is low. ing.

Further, when a plurality of inverters are provided in one bank (in the same premises) of the system power supply, the power output from the system interconnection system is consumed in the bank or the reverse power flows to the system side. As a result, the voltage of the system power supply rises. For this reason, in the system interconnection system, the output of the inverter is suppressed to prevent a voltage increase of the system power supply.

When a large number of loads are connected to a system power supply in a bank, the power factor of the entire bank may be low even if the power factor of each load is high.
Further, when harmonics are included in the system power supply, it is necessary to suppress the harmonics.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned facts, and makes it possible to improve the power factor and suppress harmonics in a bank when a plurality of inverters are installed in the bank. The purpose is to propose a grid connection system.

[0008]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems is achieved by connecting a plurality of inverters in parallel and providing the DC power by a number of inverters set according to the DC power output from the DC power supply. A system interconnection system for regenerating electric power output from a power supply to a system power supply and supplying the system load to a system load connected to the system power supply, comprising: a voltage detection unit configured to detect a system voltage; and a load supplied to the system load. A load current detecting means for detecting a current; a power factor determining means for determining a power factor from detection results of the voltage detecting means and the load current detecting means; and a power factor determined by the power factor determining means is out of a predetermined range. And operation control for operating the stopped inverter based on the load current when the operation of at least one of the plurality of inverters is stopped. Characterized in that it comprises a stage, a.

According to the present invention, when regenerating DC power to the system power supply using a plurality of inverters, the number of inverters corresponding to the DC power output from the DC power supply is operated and the extra inverter is stopped. Let it be.

On the other hand, the power factor determining means determines the power factor of the system load based on the load current and the system voltage, and when the power factor becomes low, the operation control means operates the inverter whose operation is stopped. At this time, the stopped inverter is operated by constant voltage control based on the load current to generate reactive power included in the load current or reactive power corresponding to a harmonic component and supply the generated reactive power to the system load.

As a result, it is possible to suppress the reactive power and harmonics contained in the load current, to improve the power factor of the system load as viewed from the system power supply, and to prevent the harmonics from flowing into the system power supply.

Further, the present invention includes inverting means for generating an inverse phase component of the load current, and the operation control means stops the operation based on the load current whose phase has been inverted by the inverting means. It is characterized by operating the inverter.

Thus, according to the present invention, the inverter operated by the operation control means is generated by the system load.
Reactive power is supplied to the system load to increase the power factor of the system load viewed from the system power supply. That is, the reactive power supplied from the system power supply to the system load can be reduced.

Further, the present invention includes removing means for removing a fundamental wave of the load current, and the inverting means generates a reverse-phase component of the load current from which the fundamental wave has been removed by the removing means. I do.

According to the present invention, the removing means extracts a harmonic component by removing a fundamental wave from the load current. By operating the inverter based on the output of this removing means, harmonics generated in the system load are canceled out,
It is possible to prevent harmonics generated by the system load from flowing to the system power supply.

According to the present invention, one master unit is set from a plurality of inverters, and this master unit starts / stops the slave unit, and determines whether the slave unit is stopped based on the load current. A configuration for setting a slave unit to be driven can be used.

Further, according to the present invention, the inverter can be formed by a controller provided in each of the inverters and communication means for connecting the controllers.

This eliminates the need to provide special operation control means.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a power supply system 10 applied to the present embodiment.

In the power supply system 10, a solar cell module is used as a DC power supply 12, and a plurality of inverters 14 are connected to the DC power supply 12 in parallel. In the present embodiment, as an example, the power supply system 10 includes three inverters 14A, 14B, and 14C (referred to as “inverter 14” when collectively referred to).

The input side of each inverter 14 is connected to a latch type magnet switch 18 (18A, 18B, 1).
8C), and the output side is connected to the system power supply 16. As a result, the power supply system 10 forms a grid-connected power generation system that converts DC power output from the DC power supply 12 into AC power by the inverter 14 and outputs the AC power to the system power supply 16. In the present embodiment, as an example, a DC power supply 12 having a maximum output power of 10 kW and a 3.5 kW output
An example using one inverter 14 is shown.

As shown in FIG. 2, each inverter 14 includes an inverter circuit 20 and an inverter circuit 2
0 is provided, and the DC power input to the inverter 14 via the magnet switch 18 is supplied to the inverter circuit 20 via the noise filter 26.

A switching element (not shown) is connected to the inverter circuit 20 in a bridge shape. The inverter circuit 20 switches the DC element based on the PWM theory to switch the switching element to a frequency substantially equal to that of the system power supply 16. Outputs pseudo sine wave. At this time, the DC power input to the inverter circuit 20 is converted by the inverter circuit 20 into AC power having substantially the same frequency as that of the system power supply 16 and output.

The AC power output from the inverter circuit 20 is passed through a filter circuit 28, a noise filter 29, and a parallel-off contactor 30 in a transformerless system power supply 1
6 line.

The microcomputer 22 includes an input voltage detector 32 composed of an isolation amplifier for detecting a DC voltage input to the inverter circuit 20, an input current detector 34 composed of a current transformer (CT) for detecting a DC current, Current transformer (C) for detecting an alternating current output from inverter circuit 20
T), and a voltage waveform detector 40 for detecting a system voltage and a voltage waveform of the system power supply 16 by a transformer (PT).

Normally, the microcomputer 22 includes the input voltage detector 3
Based on the DC power detected by the input current detection unit 34 and the voltage detected by the voltage waveform detection unit 40, a duty ratio of a switching signal for driving a switching element (not shown) of the inverter circuit 20 is controlled.

Thus, inverter 14 outputs AC power whose phase and frequency match system power supply 16.
Note that the AC power output from the inverter circuit 20 has a sawtooth waveform, and the filter circuit 28 removes harmonic components from the output power of the inverter circuit 20 so that the AC power having a predetermined voltage waveform Is output.

On the other hand, the parallel contactor 30 is connected to the microcomputer 2
The microcomputer 22 connects and disconnects the inverter 14 and the system power supply 16 by the parallel contactor 30. As a result, for example, the microcomputer 22 uses the DC power supply 12 because the power generated by the solar cell module (DC power supply 12) is small or not generated.
When the operation of the inverter 14 is stopped because the output power from the inverter 14 is small, the inverter 14 and the system power supply 1
6 and immediately before the inverter 14 starts operating, the inverter 14 and the system power supply 16 are connected.

The microcomputer 22 includes a voltage waveform detector 4
When it is determined from the voltage waveform detected by 0 that the system power supply 16 is in a power failure state, the inverter 14 is quickly disconnected from the system power supply 16 by the disconnecting contactor 30 to prevent the inverter 14 from operating alone. Further, the microcomputer 22 can control an overvoltage (OVR), an undervoltage (UVR), a frequency rise (OFR), and a frequency fall (UF).
R) and protection of the inverter 14 against islanding. Note that a conventionally known configuration and control method can be applied to the inverter 14, and a detailed description thereof will be omitted in the present embodiment.

On the other hand, as shown in FIG. 1, in the power supply system 10, remote controllers 50 (50A, 50B, 50C) are connected to the respective inverters 14.

As shown in FIG. 3, the remote controller 50 is provided with a power supply circuit 56 together with a control section 52 having a microcomputer and a display section 54 using an LCD or the like.
Are connected to the control unit 52. The remote controller 50 is provided with a setting switch section 58 and a communication connector 60, which are connected to the control section 52.

The power supply circuit 56 is provided with a backup battery (not shown) and a system power supply 16.
, And the remote controller 50 is operated by the power supplied from the system power supply 16. That is, the remote controller 50 receives no DC power from the DC power
Is operable even when is stopped.

The microcomputer 22 of the inverter 14 is connected to the communication connector 60 of the remote controller 50. This allows the remote controller 50 to manage the operation of the inverter 14, such as integrating the output power amount output from the inverter 14. Further, when the operation of the inverter 14 is stopped to stop the independent operation, this information is input from the microcomputer 22 to the remote controller 50.

As shown in FIG. 1, each of the remote controllers 50 is connected to a drive circuit 62 for driving the magnet switch 18 on / off.

The inverter 14 includes the magnet switch 1
When the DC power is no longer input after the switch 8 is turned off, the operation is stopped, and the operation is started by turning on the magnet switch 18 and supplying the DC power.

Each remote controller 50 turns off the magnet switch 18 when outputting a control signal for instructing the microcomputer 22 of the inverter 14 to stop the operation.
The magnet switch 18 is turned on when outputting a signal for instructing start of operation. Note that the remote controller 5
The microcomputer 22 may turn on / off the magnet switch 18 based on an operation / stop instruction input from 0 to the microcomputer 22.

The other remote controllers 50 are connected to the communication connectors 60 of the respective remote controllers 50 via communication cables 64. At this time, the remote controller 50 is connected by a dedicated communication cable 64 so as to form a loop, for example.

Thus, the remote controller 50
A, 50B, and 50C can exchange operation information of the inverters 14A, 14B, and 14C to which they are connected.

The power supply system 1 configured as described above
In the case of 0, one of the remote controllers 50 serves as a master unit, and the operation / stop of the inverter 14 connected to the master unit and the inverter 14 connected to another remote controller 50 serving as a slave unit. Control. The settings of the master unit and the slave unit can be set by a dip switch (not shown) provided in a setting switch unit 58 of the remote controller 50. In the present embodiment, the remote controller is set by the dip switch. An address for specifying 50 is set.

When setting the remote controller 50 which is the first master unit without using the DIP switch of the setting switch unit 58, the magnet switches 18A, 18B,
18C is closed, and any of the inverters 14 is installed so as to be operable by the power supplied from the DC power supply 12. Thereafter, when the solar cell module serving as the DC power supply 12 starts power generation, the remote controller 50 of the inverter 14 which has started operation first is set as a master unit.

The remote controller 50 thus set as a master unit first sets the remaining remote controllers 50 as slave units so that the other inverters 14 do not start operating. Thereafter, the remote controller 50 set as the master unit always keeps the connected inverter 14 in the operating state and the DC power supply 1
The inverter 14 to which the remote controller 50 as the slave unit is connected is operated / stopped in accordance with the increase or decrease of the output power of Step 2.

On the other hand, in the power supply system 10, for example, when the operation is stopped for one day, based on the operation information such as the integrated value of the output power of the inverters 14 A to 14 C (output power amount) and the integrated value of the operation time, The remote controller 50 as a master is set. Thereby, the inverters 14A to 14A
During C, the output power amount or the integrated value of the operation time is averaged.

That is, the remote controller 50 which is the next master unit is connected to the inverter 14 having the shortest output power or operating time.

For this reason, when the connected inverter 14 is stopped, the remote controller 50 serving as a slave uses the integrated value (output power) of the output power of the inverter 14 as the master. Output to the remote controller 50.

Remote controller 5 serving as a master unit
0 indicates that when the DC power from the DC power supply 12 is stopped, the connected inverter 14 is stopped, and the output power of the inverter 14 is calculated. After that, the output power amounts of the inverters 14 are compared, and the remote controller 50 of the inverter 14 with the least is set as the next master unit. Thus, the next time the power supply system 10 starts up, the remote controller 50 newly set as the master unit controls the operation of each inverter 14.

On the other hand, in the inverter 14 connected to the remote controller 50 set in the master unit, the maximum power tracking control (MPPT: Maximum Power Point Trac) for taking out the maximum output following the change of the input DC power.
king). Further, the inverter 14 connected to the remote controller 50 set as a slave unit
Performs constant power control that always provides the maximum output. The remote controller 50 set as the master unit has a DC power supply 12 so that the inverter 14 of the slave unit can perform constant power control.
Based on the change in the output, the magnet switch 18 is opened and closed together with the operation / stop.

Further, in the power supply system 10, the remote controller 50 set as the master unit is connected to the overvoltage (OVR), the undervoltage (UVR), the frequency drop (UFR), and the frequency rise (OFR) while preventing the isolated operation. The protection is performed collectively, and interference and malfunction due to each inverter 14 individually protecting the interconnection are prevented.

Incidentally, as shown in FIG. 1, the power supply system 10 is provided with a power supply adjusting device 70.
The power supply adjusting device 70 includes a power factor determining circuit 72 and a current extracting unit 74.

The power factor determining circuit 72 includes a load current detecting section 78 having a CT 76 for detecting a load current flowing through the local load 66, a system voltage detecting section 82 having a PT 80 for detecting the voltage of the system power supply 16, and Is connected. Note that the output of the voltage waveform detector 40 provided in the inverter 14 may be used instead of the system voltage detector 82.

The power factor determining circuit 72 includes a load current detecting section 78
The power factor of the local load 66 is detected by the system voltage detection unit 82.

The current extracting section 74 is provided with a phase inverting circuit 84. The phase judging circuit 84 supplies the load current detected by the load current detecting section 78 to the attenuator 86 and the band emission filter (Band Eliminatio).
n filter: hereinafter referred to as “BEF88”).

As shown in FIG. 5, the BEF 88 attenuates a predetermined area including the frequency f ₀ of the system power supply 16,
It has a frequency characteristic in which only harmonic components included in the system power supply 16 pass. Note that a high-pass filter (HPF) may be used instead of the BEF 88.

The phase inversion circuit 84 inverts and outputs the load current input from the BEF 88. That is, it outputs the inverted harmonic component of the load current (hereinafter referred to as “current signal Irω”).

On the other hand, as shown in FIGS. 1, 2 and 4, the output of the phase inversion circuit 84 is connected to the inverter 14, and the current signal Irω output from the phase inversion circuit 84 is Each is entered. Also, as shown in FIGS. 1 to 3, the power factor determination circuit 72 is connected to the remote controller 50 provided for each of the inverters 14, and when the power factor of the system load 66 decreases, A signal indicating a decrease in the power factor is output to the remote controller 50.

In the power supply system 10, as described above, the number of the inverters 14 to be operated according to the generated power is set, only the set number of the inverters 14 is operated, and the other inverters 14 are stopped. At this time, when a signal indicating a decrease in the power factor is input from the power factor determination circuit 72 to the remote controller 50 set in the master device, the master device operates the stopped inverter 14.

As shown in FIGS. 2 and 4, each of the inverters 14 is provided with a changeover switch 90. The inverter 14, which is operated based on the judgment result of the power factor judgment circuit 72, is connected to the microcomputer 22. Operates the changeover switch 90 to switch the input. Thus, the output of the phase inversion circuit 84 is input to the inverter 14 instead of the output of the voltage waveform detection unit 40. At this time, the inverter 14 performs constant voltage control. That is, the inverter 14 operated based on the determination result of the power factor determination circuit 72
Performs constant voltage control based on the inverted harmonic component of the load current.

For example, as shown in FIG.
In the inverter 14, the power generation voltage V_DCAnd system
Voltage V_ACBased on the system voltage V_ACAnd system power supply 16
Frequency f₀Switch to obtain a voltage waveform according to
Generate a signal. The output of the signal generator 92 is
Combined with the current waveform, the switching signal period (eg
For example, 20 Hz) is determined together with the output of the oscillator 94.
Input to the comparator 96. As a result, the comparator 96
The DC power of the power supply 12 to the voltage V of the system power supply 16 _ACAnd around
Wave number f₀The switching signal ST for converting to
Is done.

On the other hand, in the inverter 14 which starts the operation based on the judgment result of the power factor judging circuit 72, when the changeover switch 90 is operated, the system voltage V _AC
Instead, the switching signal ST is generated based on the harmonic component of the inverted load current. Thereby, the inverter 14 outputs a reactive power at a constant voltage according to the load power.

The operation of the present embodiment will be described below.

In the power supply system 10, first, the setting of the master unit of the remote controller 50 is performed. The setting of the master unit may be performed by setting one master unit and one slave unit as initial values together with the address by using a dip switch of a setting switch unit 58 provided in each remote controller 50.

When automatically setting the master / slave unit, the magnet switches 18A to 18C are turned on while the output of the DC power supply 12 is stopped, and the inverter 1 is turned on.
4 is operable. In this state, for example, when the DC power supply 12 starts outputting DC power at sunrise, the inverters 14A to 14C have a slight time difference.
Will start driving. At this time, when any of the inverters 14 starts operation, a signal indicating that the operation has started is output to the remote controller 50.

The remote controller 50 connected to the inverter 14 that has started operation first outputs a control signal to each remote controller 50 so that the other inverter bars 14 do not start operating. As a result, the remote controller 50 of the inverter 14 that has operated first becomes the master unit, and the other remote controllers 50
Is set as a slave unit.

As described above, the remote controller 50A
When the setting of the master unit / slave unit is made between 50C and 50C, the inverter 14A
14C is controlled.

At this time, the inverter 14 serving as a master unit is
MPPT control for changing the output power according to the generated power is performed, and when the generated power exceeds the rated output of the inverter 14 serving as the master, the inverter 14 of the slave starts operating under constant power control. Thus, the power supply system 10 can efficiently regenerate the generated power to the system power supply 16. In the power supply system 10, when the power generated by the DC power supply 12 is relatively low, at least one of the plurality of slave units stops operating.

Incidentally, the power supply system 10 is provided with a current adjusting device 70. This current adjusting device 70
The power factor determining circuit 72 determines the power factor of the local load 66 from the load current detected by the load current detecting unit 82 and the system voltage detected by the system voltage detecting unit 82. As a result, when the power factor of the on-premise load 66 decreases and the reactive power increases,
The fact that the power factor has decreased is output to the remote controller 50.

Remote controller 5 serving as a master unit
When a signal indicating that the power factor has been reduced is input from the power factor determination circuit 72, 0 is checked for the presence or absence of the inverter 14 that has stopped operation, and when there is an inverter 14 that has stopped operation, The remote controller 50 corresponding to the inverter 14 is set to be actively operated.
Output to

When the active operation is instructed from the master unit, the remote controller 50 of the inverter 14 whose operation has been stopped operates the magnet switch 18 and the changeover switch 90 to switch the input to the inverter 14. The operation of the inverter 14 is instructed by the constant voltage control set during the active operation.

As a result, the operation of the inverter 14 whose operation is stopped starts operating under constant voltage control. For example, a remote controller 50A and an inverter 14A
The inverter 14A and the inverter 14B, which is one of the slave units, use the
If the inverter 14C is stopped while the normal operation for regenerating the motor is being performed, the remote controller 50
C starts the active operation of the inverter 14C.

On the other hand, the current adjusting device 70 is provided with a current extracting unit 74. The current extraction unit 74 extracts a harmonic component from the load current detected by the load current detection unit 78 by the BEF 88, and outputs a current signal Irω obtained by inverting the phase of the extracted harmonic component of the load current by the phase inversion circuit 84. I do.

Inverter 14 for starting active operation
By operating the changeover switch 90 (the operation position indicated by the two-dot chain line in FIGS. 2 and 4), the current signal Irω output from the current extraction unit 74 is changed to the system voltage input from the voltage waveform detection unit 40. (Waveform), and switches the switching element based on the switching signal generated based on the current signal Irω.

As a result, the inverter 14 that has started the active operation outputs a reactive power according to the power factor of the local load 66.

That is, as shown in FIG. 1, when the current i ₂ output from the inverter 14C in active operation, the load current is i, and the power factor is cos θ, the current extractor 74 of the current adjusting device 70 Outputs a current signal Irω in which the phase of the load current i is inverted by the phase inversion circuit 84.

The current signal Irω is a signal corresponding to the invalid component of the load current i. The load current Irω is B
Since the harmonic component of the load current i passes through the EF 66, the signal is obtained by inverting the phase of the harmonic component of the system power supply 16.

While inverter 14 normally switches based on the voltage waveform of system power supply 16, inverter 14 that performs active operation switches based on current signal Irω. The power output from the DC power supply 12 is the same as that of the other inverters 1 that are operating normally.
4 (inverters 14A, 14B), the system power supply 16
Therefore, the inverter (the inverter 14C) that performs the active operation outputs reactive power corresponding to the load current i.

That is, as shown in FIG. 6, the current i ₂ output from the inverter 14 that is in active operation is a current corresponding to the invalid component of the load current i. The output of the inverter 14 that performs the active operation is supplied to the system load 66. Therefore, the inverter 14 that performs the active operation supplies the reactive power of the system load 66.

As a result, when the local load 66 to which the power supply system 10 is connected is viewed from the system power supply 16 side, the reactive power is suppressed to a low level and the system load 66 with a high power factor is connected. .

On the other hand, the BEF 88 extracts a harmonic component from the load current i, so that the current i ₂ output from the inverter 14 that is actively operating is reduced by the system load 66.
The current i ₂ is supplied to the system load 66, so that the harmonic current generated in the system load 66 is canceled by the current i ₂ .

Therefore, it is possible to suppress the harmonics generated in the system load 66 from flowing to the system power supply 16.
It is possible to prevent a current including harmonics generated by the system load 66 from flowing to the system power supply 16.

As described above, the power supply system 10 connected to the system load 66 is provided with the current adjusting device 70 and operates the plurality of inverters 14 by the number corresponding to the DC power output from the DC power supply 12. At this time, based on the load current i detected by the current adjusting device 70, the inverter 14 whose operation has been stopped is actively operated. Thereby, the power factor of the system load 66 is
0 can improve it. In addition, the system load 66
Can be suppressed by the power supply system 10.

At this time, since the inverter 14 that has started the active operation outputs reactive power, the DC power supply 12
Other inverter 14 that regenerates the electric power of the
It does not affect the operation or output of the vehicle.

The present embodiment shows an example of the present invention, and does not limit the configuration of the present invention.
INDUSTRIAL APPLICABILITY The present invention can be applied to a system interconnection system of various configurations using a plurality of inverters connected in parallel.

[0082]

As described above, according to the present invention, when the number of inverters set by the DC power output from the DC power supply is operated, the stopped inverters are determined based on the current of the system load. By operating under constant voltage control, it is possible to obtain an excellent effect that the power factor of the system load can be improved and harmonics generated by the system load can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply system applied as a system interconnection system to the present embodiment.

FIG. 2 is a block diagram illustrating a schematic configuration of an inverter used in the power supply system.

FIG. 3 is a block diagram showing a remote controller applied to the power supply system.

FIG. 4 is a block diagram schematically showing generation of a switching signal in an inverter.

FIG. 5 is a diagram schematically illustrating a frequency characteristic of a BEF provided in the power supply adjusting device.

FIG. 6 is a diagram schematically illustrating a load current and a current output from an inverter that performs active operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Power supply system (system interconnection system) 12 DC power supply 14 (14A-14C) Inverter 16 System power supply 22 Microcomputer 66 System load 70 Power supply regulator 72 Power factor judgment circuit (Power factor judgment means) 74 Current extraction part 78 Load current detection Section (load current detecting means) 82 System voltage detecting section (voltage detecting means) 84 Phase inverting circuit (inverting means) 88 BEF (removal means)

Continued on the front page (72) Inventor Isao Morita 2-5-5 Keihanhondori, Moriguchi City, Osaka Prefecture Inside Sanyo Electric Co., Ltd. (72) Inventor Yasuhiro Makino 2-5-5 Keihanhondori, Moriguchi City, Osaka Prefecture F-term (reference) in Sanyo Electric Co., Ltd. 5H420 BB12 BB16 BB18 CC03 DD03 EA37 EA43 EA47 EB05 EB19 EB26 EB39 FF03 FF04 FF09 FF25 FF26

Claims (3)

[Claims] 1. A method in which a plurality of inverters are connected in parallel, and the power output from the DC power supply is regenerated to the system power supply by the number of inverters set according to the DC power output from the DC power supply to the system power supply. A system interconnection system for supplying to a connected system load, a voltage detection unit for detecting a system voltage, a load current detection unit for detecting a load current supplied to the system load, the voltage detection unit, A power factor determining means for determining a power factor from a detection result of the load current detecting means; and a power factor determined by the power factor determining means deviating from a predetermined range, and operating at least one of the plurality of inverters. An operation control means for operating the stopped inverter based on the load current when the operation is stopped. 2. An inverter for generating an anti-phase component of the load current, wherein the operation control unit operates the stopped inverter based on the load current whose phase has been inverted by the inversion unit. The system interconnection system according to claim 1, wherein: 3. The apparatus according to claim 2, further comprising removing means for removing a fundamental wave of said load current, wherein said inverting means generates a negative-phase component of the load current from which a fundamental wave has been removed by said removing means. Grid connection system according to 1.