JP2002135983A - Distributed power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distributed power supply which can check if the plural inverters are running in an independent operation. SOLUTION: This independent power supply is provided with plural dc power supplies 1a-1c, plural ac inverters 11a-11c which convert the dc output of the dc power supplies 1a-1c into ac power to supply to the load 30 together with the commercial power system 20, an active voltage fluctuation generator 12 which outputs the same active voltage fluctuation data to fluctuate the output voltage of the inverter 11a-11c, an independent run checker 14 which decides based on the voltage at the linkage joint that the inverters are in an independent operation due to interrupted commercial power 20, and a system protective section 15 to stop the inverters 11a-11c cutting them off from the commercial power 20 when the checker 14 decides that the inverters are running in an independent operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed power supply used in connection with a commercial power system.

[0002]

2. Description of the Related Art FIG. 8 shows a block diagram of a conventional distributed power supply device. This distributed power supply device converts a plurality of DC power supplies 1a and 1b such as solar cells for converting sunlight energy into DC power, and converts the DC power of the plurality of DC power supplies 1a and 1b into AC power. A plurality of inverters 11a and 11b which are connected to the commercial power system 20 to supply AC power to the load 30, and an inverter corresponding to active fluctuation data for varying output currents of the inverters 11a and 11b, respectively. A plurality of active fluctuation creating units 12a and 12b respectively outputting to the respective 11a and 11b, and a plurality of voltage detecting units 13a and 13b respectively detecting a voltage at an interconnection point between the inverter units 11a and 11b and the commercial power system 20.
And the commercial power system 20 is stopped based on the detection results of the corresponding voltage detection units 13a and 13b, and the inverter units 11a and 11b
And a plurality of isolated operation determining units 14a and 14b that determine that the inverters 11a and 11b are in the isolated operation state and the inverter units 11a and 11b are in the isolated operation state when the commercial power system 20 is stopped. Is determined, the disconnection relays 16a, 16b are disconnected and the inverter 11
a, 11b and a system interconnection protection unit 15 for separating the commercial power system 20 from the system.

Here, inverter units 11a and 11b,
Active fluctuation creating units 12a and 12b and voltage detecting units 13a and
13b, the isolated operation determination units 14a and 14b, the parallel-off relays 16a and 16b, and the system interconnection protection units 15a and 15b convert the DC power of the DC power supply unit 1 into AC power and connect with the commercial power system 20. Power conditioners 10a and 10b for supplying AC power to a load in a system are configured. Further, DC power supply units 1a, 1b and power conditioners 10a, 1
0b constitutes a distributed power supply device.

[0004] By the way, when the commercial power system 20 is disconnected at the time of occurrence of an accident, maintenance and inspection, and the power system from the commercial power system 20 is stopped, it is assumed that the distributed power supply unit continues to operate independently. From the distributed power supply to the commercial power system 20
The distribution line is charged reversely, which may lead to an increase in accident damage and an electric shock accident of the worker.
0 may be damaged. Therefore, the commercial power system 20
It is necessary to reliably prevent the isolated operation of the distributed power supply device that occurs when the power supply is opened.

In order to detect the isolated operation state of the inverter units 11a and 11b, the isolated operation determination units 14a and 14b provide an overvoltage detection function (OV) and an undervoltage detection function (U
V), a frequency increase detection function (OF), and a frequency decrease detection function (UF). The passive function and the active method are used in combination to increase the probability of detecting the isolated operation state. I have. Here, the overvoltage detection function (O
V), an undervoltage detection function (UV), a frequency rise detection function (OF), and a frequency decrease detection function (UF) are output voltage changes and frequency changes that occur when the inverter units 11a and 11b shift to islanding operation. The islanding operation determination sections 14a and 14b each determine an islanding operation state based on the detection result of each function.

However, the inverter units 11a, 11
Under a condition where the power relationship between the output power b and the power consumption of the load 30 is completely balanced (that is, a condition where both the active power and the reactive power are balanced), the commercial power system 2
Even if the supply of power from 0 is stopped, the amount of change in the voltage and frequency at the disconnection point is small, so that the above-described function alone may not be able to detect the isolated operation state.

For this reason, the islanding operation determination sections 14a and 14b detect the islanding operation state of the inverter sections 11a and 11b by using both a passive system and an active system described later. Here, the passive system is a system that detects a sudden change in the voltage phase or frequency that occurs when the inverter units 11a shift to the islanding operation, and generally has a feature that the speed is excellent.

On the other hand, the active method is defined
a to constantly output, for example, active fluctuation data for fluctuating the output current to the inverter unit 11a.
1a... Are given a predetermined amount of variation in the output current, and the increase in the amount of variation in the output current at the time of transition to the isolated operation is detected. That is, even when the output current of the inverter units 11a changes during the interconnection operation with the commercial power system 20, the voltage at the interconnection point between the inverter units 11a and the commercial power system 20 does not change. When the system 20 is stopped and the inverter units 11a shift to the islanding operation, the voltage at the interconnection point changes in accordance with the fluctuation of the output current, so that the islanding operation determining unit 14a detects the voltage detected by the voltage detecting unit 13a. The state of islanding operation is detected from the change in.

Note that the active system includes a system such as an active power fluctuation system, a reactive power fluctuation system, and a frequency shift system. In the active power fluctuation method, the active fluctuation generating section 12a outputs active fluctuation data for changing the magnitude of the output current to the inverter sections 11a at fixed time intervals, and the isolated operation determining section 1a.
4a... In the same period, the voltage at the interconnection point detected by the voltage detection units 13a.
… Is detected. Further, in the reactive power fluctuation method, the active fluctuation generating units 12a.
Active change data for changing the phase of the output current is output at fixed time intervals, and the isolated operation determination units 14a... Change in the same cycle at the interconnection point detected by the voltage detection units 13a. The independent operation state of the inverter units 11a is detected. Further, in the frequency shift method, the active fluctuation generator 12a... Outputs active fluctuation data for changing the frequency of the output current of the inverters 11a. 1
1a... Every cycle, and the isolated operation determination unit 14a.
, The frequency of the voltage at the interconnection point detected by the voltage detectors 13a gradually changes.
… Is detected.

Here, the DC power supply units 1a are constituted by solar cell modules, but a plurality of DC power supply units 1a are provided.
.. May have different numbers of solar cell modules in series or different light receiving surfaces, or may use different DC power supplies such as fuel cells or wind power generators. When connected to one power conditioner, there is a problem that the entire power generation efficiency is reduced. Therefore, in the conventional distributed power supply device, a small-capacity power conditioner 10a is installed for each of the small-capacity DC power supply units 1a having different output characteristics. Such a distributed power supply device is called a string inverter. .

[0011]

In the distributed power supply device having the above-described structure, different active fluctuation data are output from the active fluctuation generators 12a of the power conditioners 10a to the inverters 11a. , The output currents of the inverter sections 11a... Therefore, even though the commercial power system 20 is stopped, the fluctuations given to the output currents of the inverter units 11a interfere with each other, and the voltage at the interconnection point does not change so much. May not be reliably detected, the inverter units 11a may be stopped at the time of transition to the isolated operation state, or the disconnection relay 16a
There was a problem that it was delayed to disconnect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a distributed control system capable of reliably detecting whether or not a plurality of inverter units are operating in an isolated operation state. To provide a type power supply.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of DC power supplies for generating DC power and a DC power generated by the plurality of DC power supplies are converted into AC power. A plurality of inverter units that respectively convert and supply AC power to a load in connection with a commercial power system, and an active fluctuation creating unit that outputs active fluctuation data for varying the output to the plurality of inverter units. A single operation determination unit that determines that the commercial power system is stopped and the inverter unit is in an isolated operation state based on a voltage at an interconnection point between the plurality of inverter units and the commercial power system, A system interconnection protection unit that disconnects a plurality of inverter units from the commercial power system and stops the plurality of inverter units when the islanding operation determination unit determines that the inverter unit is in the islanding operation state. The active fluctuation creating section is characterized by outputting the same active fluctuation data to a plurality of inverter sections, and each DC power supply section is provided with an inverter section for converting DC power to AC power. Since each inverter unit can be operated according to the output characteristics of the DC power supply unit, it is possible to prevent the overall power generation efficiency from lowering even when the output characteristics of each DC power supply unit are different. In addition, since the active fluctuation creating section outputs the same active fluctuation data to a plurality of inverter sections, the outputs of the plurality of inverter sections can have the same variation, and the outputs of the plurality of inverter sections can be output. Due to the interference of the given fluctuations, the detection result of the voltage detection unit does not change even though the commercial power system is stopped, and the islanding operation determination unit cannot detect the islanding operation state of the inverter unit. When the system shifts to islanding operation, the grid connection protection unit disconnects the multiple inverters from the commercial power system and stops the multiple inverters, thereby preventing the expansion of accidents and electric shock accidents to workers. It can be reliably prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, one-way communication is performed between the active variation creating section and the plurality of inverter sections, and the active variation creating section is connected to the plurality of inverter sections. The active fluctuation generator outputs the same active fluctuation data to a plurality of inverters simultaneously, so that the active fluctuation generator and the plurality of inverters are simultaneously output. All the inverters can receive the same active fluctuation data at the same timing without delaying the communication time between the inverters, and the same fluctuation can be given to the outputs of multiple inverters at the same timing. Because the fluctuations given to the outputs of multiple inverters interfere with each other, the detection result of the voltage detector may change despite the commercial power system being stopped. , It can be prevented reliably from isolated operation determination unit can not be detected islanding operation state of the inverter unit.

According to a third aspect of the present invention, in the first or second aspect of the present invention, when the independent operation determination unit determines that the commercial power system is stopped and the plurality of inverter units are in the independent operation state, the system connection is established. The system protection unit outputs an operation stop command for stopping the operation of the inverter unit to a plurality of inverter units simultaneously, and when the isolated operation determination unit detects the isolated operation state of the plurality of inverter units, the system interconnection is performed. Since the protection unit outputs the operation stop command to multiple inverters at the same time, the operation of multiple inverters can be stopped reliably, preventing the expansion of accidents and electric shock accidents of workers. Can be.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the active variation creating section outputs the active variation data to the plurality of inverters at a constant cycle, and the active variation creating section outputs the active variation data longer than the fixed cycle. When the active fluctuation data cannot be received for a certain period of time, the inverter unit stops operating when the active fluctuation data cannot be received. Therefore, when the communication line connecting the active fluctuation creating unit and the plurality of inverter units is disconnected, the inverter unit can be automatically stopped when the communication line is disconnected. In this case, it is possible to prevent the inverter unit from receiving the operation stop command from the system interconnection protection unit and continuing the isolated operation state.

According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, individual address data is assigned to the plurality of inverter units, and the address data is transmitted from the system interconnection protection unit to each inverter unit. When the status request command including the status request command is transmitted, the inverter unit whose address data matches returns status data indicating the current operation state to the grid interconnection protection unit. By outputting a status request command including address data to the units, status data indicating the current operation state can be received from each inverter unit, and the current operation state of each inverter unit can be grasped.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 1 A distributed power supply according to the present invention
Embodiments will be described with reference to the drawings. FIG. 1 is a block diagram of a distributed power supply device according to the present embodiment. The distributed power supply device includes a plurality of solar cells (for example, three in the present embodiment) such as solar cells that convert sunlight energy into DC power. DC power supply units 1a to 1c and a plurality of DC power supply units 1a to 1c
A plurality of inverters 11a to 11c, which respectively convert the DC power into AC power and supply AC power to the load 30 in connection with the commercial power system 20;
Active fluctuation creating unit 12 that outputs active fluctuation data for varying the outputs of the inverters 11a to 11c to the inverter units 11a to 11c via a communication line, and the voltage at the interconnection point between the inverter units 11a to 11c and the commercial power system 20. Voltage detection unit 1 for detecting
3 and the islanding determination unit 1 that determines that the commercial power system 20 is stopped and the inverter units 11a to 11c are in the islanding operation state based on the voltage value of the interconnection point detected by the voltage detection unit 13.
4, the commercial power system 20 stops, and the inverter units 11a to
When the island 11c is in the islanding operation state, the islanding operation determination unit 1
4 includes a system interconnection protection unit 15 that disconnects the disconnection relay 16 and disconnects the inverter units 11 a to 11 c from the commercial power system 20 when the determination is made. In the present embodiment, the solar cells are used as the DC power supply units 1a to 1c. However, the DC power units 1a to 1c are not limited to the solar cells, but may be a DC power supply such as a fuel cell or a wind power generator. The DC power supply units 1a to 1c may be configured by a combination thereof.

In the system interconnection protection unit 15, as shown in FIG. 2, the active fluctuation creating unit 12 includes inverter units 11a to 11c.
Output the same active fluctuation data. The active fluctuation generator 12 changes the outputs of the inverters 11a to 11c by, for example, a frequency shift method. That is, the active fluctuation creating unit 12 includes the inverter units 11a to 11a.
The active variation data that changes the frequency of the output current c by a very small amount from the frequency of the voltage at the interconnection point one cycle before is output to the inverters 11a to 11c. Based on the active fluctuation data input from the fluctuation creating unit 12, output currents whose frequencies are slightly changed are output. As described above, the inverter units 11a to 11c include the active fluctuation creating unit 1
2, the output current is varied based on the same active variation data input from the
The fluctuations of the output current do not interfere with each other in a to 11c.

Here, when the commercial power system 20 is interconnected, the voltage at the interconnection point hardly changes even if the output current of each of the inverters 11a to 11c fluctuates. On the other hand, when the commercial power system 20 is stopped, when the output current of each of the inverters 11a to 11c fluctuates, the voltage at the interconnection point changes. Determines that the commercial power system 20 has been stopped and has shifted to the islanding operation state, and the system interconnection protection unit 15 can stop the inverter units 11a to 11c and disconnect the disconnection relay 16, thereby expanding the accident. And electric shock accidents of workers can be reliably prevented.

In this embodiment, a plurality of DC power supply units 1 are provided.
Inverters 11a to 11c for converting DC power into AC power are provided for each of the inverters 11a to 1c.
Since a to 11c can be operated, it is possible to prevent the overall power generation efficiency from decreasing even when the output characteristics of the DC power supply units 1a to 1c are different.

Incidentally, one-way communication between the active fluctuation generator 12 and the inverters 11a to 11c is performed between the active fluctuation generator 12 and the plurality of inverters 11a to 11c. As shown in FIG. 2, since the same active fluctuation data is output simultaneously, there is no communication time lag between the active fluctuation creating unit 12 and the inverter units 11a to 11c, and the same is applied to all the inverter units 11a to 11c. Can be received at the same time.
In each of the inverter sections 11a to 11c, the active fluctuation creating section 1
Since the output current is varied based on the same active variation data simultaneously input from
The same variation can be given to the outputs of the inverters 11a to 11c at the same timing.
The fluctuations given to the output current 1c do not interfere with each other, and the isolated operation state can be reliably detected.

When the isolated operation determination unit 14 determines that the commercial power system 20 has stopped and the plurality of inverter units 11a to 11c have shifted to the isolated operation state, the system interconnection protection unit 15 sets the disconnection relay 16 And the inverter unit 11a
11 and the commercial power system 20, the operation stop command is output to each of the inverter units 11a to 11c to stop the operation state of the inverter units 11a to 11c. As shown in FIG. Interconnection protection unit 15
, An operation stop command is simultaneously output to each of the inverter units 11a to 11c.
1c can be stopped at the same time.

When the operation stop command is output from the system interconnection protection unit 15 to the inverter units 11a to 11c,
As shown in FIG. 4, the operation stop command may be output a plurality of times, and the inverter units 11a to 11c may fail to receive the operation stop command, and
11c can be prevented from continuing the operation state, and the inverter units 11a to 11c can be reliably stopped.

In addition, the operation stop command output from the grid connection protection unit 15 at the time of transition to the islanding operation because the communication line connecting the grid connection protection unit 15 and the inverter units 11a to 11c is disconnected. Cannot be received by the inverters 11a to 11c and the inverters 11a to 11c continue operating, the inverters 11a to 11c continue to operate independently, and the problem as described in the conventional example is solved. This may occur.

Here, when the communication line between the inverter 11c and the grid connection protection unit 15 is broken, the inverter 11c outputs the active fluctuation data (the output of the active fluctuation generator 12) at a constant period. For example, in the case of the frequency shift method, it is not possible to receive data that changes the frequency of the output current of the inverter unit 11c by a very small amount from the frequency of the voltage at the interconnection point one cycle before, so that it is longer than the certain period. If the inverter units 11a to 11c have a function of automatically stopping the operation when the active fluctuation data cannot be received for a certain period of time (for example, about 0.5 seconds), the inverter units 11a to 11c cannot receive the operation stop command.
11c can be prevented from continuing the isolated operation state.

Further, in the above-described embodiment, communication in only one direction is performed from the system interconnection protection unit 15 to the inverter units 11a to 11c, but a transmission terminal (not shown) of the system interconnection protection unit 15 is used. Is connected to a receiving terminal (not shown) of each of the inverter units 11a to 11c via a communication line, and a receiving terminal (not shown) of the system interconnection protection unit 15 is connected to a transmitting terminal (not shown) of each of the inverter units 11a to 11c. (Not shown) via another communication line, and bidirectional communication may be performed from the system interconnection protection unit 15 to the inverter units 11a to 11c. That is, individual address data is assigned to each of the inverter units 11a to 11c, and as shown in FIG.
State request command including the address data of
1a to 11c, each inverter unit 11
In a to 11c, the address data included in the received status request command is compared with its own address data, and if they match, the status data indicating the current operation status is transmitted to the grid connection protection unit 15 by the grid connection. It is returned to the protection unit 15. Similarly, from the grid connection protection unit 15 to the inverter unit 11
When the status request command including the address data of b and 11c is output to the inverter units 11a to 11c, each of the inverter units 11a to 11c compares the address data included in the received status request command with its own address data. If they match, status data indicating the current operating state is returned to the grid interconnection protection unit 15. As described above, bidirectional communication is performed between the system interconnection protection unit 15 and each of the inverter units 11a to 11c, and state data indicating an operation state from each of the inverter units 11a to 11c to the system interconnection protection unit 15. Is returned, the system interconnection protection unit 15 can easily grasp the current operation state of the inverter units 11a to 11c.

In the above-described embodiment, the system interconnection protection unit 1
5 and a communication line for connecting the inverter units 11a to 11c, the active fluctuation data, the operation stop command and the state data are transmitted and received using the communication line. As shown in FIG. Interconnection protection unit 15 and inverter units 11a to
The signal transmission may be performed by a power line carrier system in which a signal line is superimposed on the power line 17 connecting to the power line 11c. Since there is no need to wire a communication line separately from the power line 17, cost reduction can be achieved. it can.

[0029]

As described above, according to the first aspect of the present invention, a plurality of DC power supply units for generating DC power, and a DC power generated by the plurality of DC power supply units are converted into AC power, respectively. A plurality of inverter sections that supply AC power to a load in conjunction with the inverter, an active fluctuation creating section that outputs active fluctuation data for varying the output of the plurality of inverter sections, An islanding operation determining unit that determines that the commercial power system has stopped and the inverter unit is in an islanding operation state based on the voltage at the interconnection point with the power system, and that the commercial power system has stopped and a plurality of inverter units are in the islanding operation state. When the islanding operation determination unit determines that the power supply has become inactive, the system includes a plurality of inverter units and a commercial power system, and a system interconnection protection unit that stops the plurality of inverter units. It is characterized by outputting the same active fluctuation data to the inverter units, and each DC power supply unit is provided with an inverter unit that converts DC power to AC power, so that it is suitable for the output characteristics of each DC power supply unit. Since each inverter unit can be operated, there is an effect that even when the output characteristics of each DC power supply unit are different, it is possible to prevent the overall power generation efficiency from lowering. In addition, since the active fluctuation creating section outputs the same active fluctuation data to a plurality of inverter sections, the outputs of the plurality of inverter sections can have the same fluctuation, and the outputs of the plurality of inverter sections can be output. Due to the interference of the given fluctuations, the detection result of the voltage detection unit does not change even though the commercial power system is stopped, and the islanding operation determination unit cannot detect the islanding operation state of the inverter unit. When the system shifts to isolated operation, the grid interconnection protection section separates the multiple inverter sections from the commercial power system and stops the multiple inverter sections, thereby preventing the spread of accidents and electric shock accidents by workers. This has the effect that it can be reliably prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, one-way communication is performed between the active variation creating section and the plurality of inverter sections, and the active variation creating section is connected to the plurality of inverter sections. The active fluctuation generator outputs the same active fluctuation data to a plurality of inverters simultaneously, so that the active fluctuation generator and the plurality of inverters are simultaneously output. All the inverters can receive the same active fluctuation data at the same timing without delaying the communication time between the inverters, and the same fluctuation can be given to the outputs of multiple inverters at the same timing. Since the fluctuations given to the outputs of the plurality of inverters interfere with each other, the detection result of the voltage detection unit does not change even when the commercial power system is stopped. Isolated operation determination unit there is an effect that from becoming undetectable islanding operation state of the inverter unit can be prevented reliably.

According to a third aspect of the present invention, in the first or second aspect of the present invention, when the independent operation determination unit determines that the commercial power system is stopped and the plurality of inverter units are in the independent operation state, the system connection is established. The system protection unit outputs an operation stop command for stopping the operation of the inverter unit to a plurality of inverter units simultaneously, and when the isolated operation determination unit detects the isolated operation state of the plurality of inverter units, the system interconnection is performed. Since the protection unit outputs operation stop commands to multiple inverters at the same time, the operation of multiple inverters can be stopped reliably, and the expansion of accidents and electric shock accidents of workers can be reliably prevented. There is an effect that can be.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the active variation generating section outputs the active variation data to the plurality of inverters at a constant cycle, and the active variation creating section outputs the active variation data longer than the constant cycle. When time active fluctuation data cannot be received, the inverter unit stops operating,
If the active fluctuation data cannot be received for a certain period of time longer than the predetermined period in which the active fluctuation data is transmitted, the inverter unit has stopped its operation, so a communication line connecting between the active fluctuation creating unit and the plurality of inverter units. In the event of disconnection of the inverter, the inverter unit can be automatically stopped.When the inverter unit enters the stand-alone operation state when the communication line is disconnected, the inverter unit cannot receive the operation stop command from the grid connection protection unit. There is an effect that the operation state can be prevented from continuing.

According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, individual address data is assigned to the plurality of inverters, and the address data is transmitted from the system interconnection protection unit to each inverter unit. When the status request command including the status request command is transmitted, the inverter unit whose address data matches returns status data indicating the current operation state to the grid interconnection protection unit. By outputting a state request command including address data to the sections, status data indicating the current operation state can be received from each inverter section, and there is an effect that the current operation state of each inverter section can be grasped. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a distributed power supply device according to a first embodiment.

FIG. 2 is a time chart for explaining the operation of the above.

FIG. 3 is a time chart for explaining another operation of the above.

FIG. 4 is a time chart for explaining another operation of the above.

FIG. 5 is a time chart for explaining still another operation of the above.

FIG. 6 is a time chart for explaining still another operation of the above.

FIG. 7 is a block diagram of another distributed power supply device according to the first embodiment;

FIG. 8 is a block diagram of a conventional distributed power supply device.

[Explanation of symbols]

 1a to 1c DC power supply unit 11a to 11c Inverter unit 12 Active fluctuation creation unit 14 Single operation determination unit 15 Grid connection protection unit 20 Commercial power system 30 Load

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Yoshitake 1048 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. F-term (reference) 5G066 HA11 HB03 HB05 5H007 BB07 DA03 DA06 DC05

Claims (5)

[Claims] 1. A plurality of DC power supply units for generating DC power,
DC power generated by multiple DC power supplies is converted to AC power, and multiple inverters are connected to the commercial power system to supply AC power to the load. An active fluctuation creating unit that outputs active fluctuation data for causing the power supply system to stop, and determines from the voltage at the interconnection point between the plurality of inverter units and the commercial power system that the commercial power system has stopped and the inverter unit is in an isolated operation state. When the isolated operation determination unit determines that the commercial power system is stopped and the plurality of inverter units are in the isolated operation state, the plurality of inverter units and the commercial power system are disconnected, and the And a system interconnection protection unit for stopping the power supply unit, wherein the active fluctuation generation unit outputs the same active fluctuation data to a plurality of inverter units. 2. One-way communication is performed between an active fluctuation creating section and a plurality of inverter sections, and the active fluctuation creating section outputs the same active fluctuation data to a plurality of inverter sections simultaneously. The distributed power supply according to claim 1, wherein: 3. An operation stop command for causing the system interconnection protection unit to stop operation of the inverter unit when the islanding operation determination unit determines that the commercial power system is stopped and the plurality of inverter units are in the island operation state. 3 is output simultaneously to a plurality of inverter units. 4. An active fluctuation generating section outputs active fluctuation data to a plurality of inverter sections at a fixed cycle. If the active fluctuation data cannot be received for a fixed time longer than the fixed cycle, the inverter section operates. 4. The distributed power supply according to claim 1, wherein the power supply is stopped. 5. A method according to claim 1, wherein individual address data is assigned to the plurality of inverters, and when a status request command including the address data is transmitted from the grid interconnection protection unit to each inverter, the inverters having the same address data are transmitted. The distributed power supply device according to claim 1, wherein the unit returns status data indicating a current operation state to the system interconnection protection unit.