JP7233279B2 - Grid connection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a grid connection device that connects a power supply device to a power grid.

In Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-262468), a plurality of distributed power supply equipment (power generation equipment 2) and information transmission and reception via a communication line between the plurality of distributed power supply equipment A distributed power management system is described comprising a server device (51) capable of The system described in Patent Literature 1 is used for the purpose of remotely monitoring the operating state of distributed power supply equipment by a server device and quickly detecting an abnormality or the like.

Distributed power supply facilities also include systems configured to supply power to the power system (reverse power flow). However, when many distributed power supply facilities are connected to the power system and the power supplied from the distributed power supply facilities to the power system increases, the system voltage of the power system rises.

In view of such a problem, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2013-172495), a distributed power supply facility detects a reverse power flow of power based on a comparison between the system voltage and a predetermined threshold voltage. It is described that control is performed to stop or reduce reverse power flow. In Patent Literature 2, an attempt is made to suppress an increase in system voltage by such voltage increase suppression control.

JP 2010-262468 A JP 2013-172495 A

As in the system described in Patent Document 2, when the distributed power supply equipment performs control to stop the reverse power flow of power or to reduce the power that flows in the reverse power flow, the operator of the distributed power supply equipment sells power You will not be able to obtain the economic benefits that you could have obtained. Moreover, in order to perform such control, it is necessary to lower the output power of the power supply device, for example, below the rated power. In other words, since the power supply cannot be operated in a highly efficient state, high energy saving cannot be obtained.

It should be noted that the system voltage in the power system on the secondary side of the same transformer fluctuates depending on, for example, the power supply and demand balance in the power system on the secondary side of the transformer. Therefore, even if one distributed power supply facility stops reverse power flow as described in Patent Document 2, other distributed power supply systems connected to the power system on the secondary side of the same transformer Depending on the power supplied by the power supply facility and the load power of other loads, the system voltage may be maintained at a high value without dropping.

In addition, the system voltage in the power system on the secondary side of the same transformer is not the same at all points in the power system. There is a possibility that the system voltage will be locally high in such areas, and that the system voltage will be locally low in areas where distributed power supply facilities are rarely interconnected. Therefore, even if one distributed power supply facility stops reverse power flow, the system voltage in other areas does not rise so much, and other distributed power supply facilities connected to those areas There is also the possibility that the reverse power flow has not been stopped.

As described above, even if one distributed power supply facility stops reverse power flow, the high system voltage cannot be resolved, and the power quality of the power system cannot be maintained satisfactorily. In addition, the need to keep power quality such as system voltage in good condition is a common problem for all distributed power supply facilities that are connected to the power system on the secondary side of the same transformer. In spite of this, there is also the problem that only a small number of distributed power supply facilities stop the reverse power flow of electric power, and thus economic benefits cannot be obtained.

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 grid interconnection device capable of maintaining good power quality of a power system.

A feature configuration of a grid interconnection device according to the present invention for achieving the above object is a grid interconnection device that connects a power supply device to a power system,
a power conversion unit that converts the output power output by the power supply device into a predetermined power;
A connection state between a single-phase three-wire AC line having a first voltage line, a second voltage line, and a neutral line connected to the electric power system and the power conversion unit is defined as a state of connection between the first voltage line and the neutral line. a first connection state in which the power conversion unit is connected to a line and is not connected to the second voltage line; and a first connection state in which the second voltage line, the neutral line and the power conversion unit are connected and the first voltage line a connection state switching unit capable of switching between a second connection state in which connection is not made to the
The connection state switching unit performs a switching process of switching to a randomly determined one of the first connection state and the second connection state at a predetermined timing.

According to the above-described characteristic configuration, the connection state switching unit can change the supply destination of the power supplied from the power supply device to the first voltage line or the second voltage line as needed. In other words, the power supplied from the power supply device is not configured to be fixedly supplied to any one of the voltage lines. As a result, for example, even if the voltage of one of the first voltage line and the second voltage line becomes high, such a high voltage situation can be improved by operating the connection state switching unit. . Moreover, since the high voltage condition of the electric power system can be improved, it is possible to obtain an economic merit by continuing the operation of the power supply device.

In addition, according to the above characteristic configuration, the connection state switching unit does not fix the supply destination of the power supply of the power supply device, but randomly changes it at a predetermined timing. As a result, for example, even if a situation occurs in which the voltage of one of the first voltage line and the second voltage line becomes high, such a high voltage situation can be fixed by operating the connection state switching unit. can be avoided.

1 is a diagram showing a configuration of a distributed power supply system provided with a grid connection device; FIG. 9 is a flowchart for explaining switching processing of a connection state switching unit; 9 is a flowchart for explaining another switching process of the connection state switching unit; 9 is a flowchart for explaining another switching process of the connection state switching unit;

A distributed power supply system according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of a distributed power supply system provided with a grid interconnection device 20. As shown in FIG. As illustrated, in the distributed power supply system, a power supply device 8 is interconnected to the power system 1 via a grid interconnection device 20 . The grid interconnection device 20 includes a power conversion unit 7 and a connection state switching unit 6 .

A single-phase three-wire AC line 2 having a first voltage line 2a, a second voltage line 2b, and a neutral line 2c is connected to a power system 1 . A power consumption device 3 as a 100V load is connected to the first voltage line 2a to consume the power supplied to the first voltage line 2a. A power consumption device 4 as a 100V load is connected to the second voltage line 2b to consume the power supplied to the second voltage line 2b.

The power supply device 8 is configured using a power generation device, a charge/discharge device, or the like. For example, as the power generation device, various devices such as a device including a fuel cell and a device including an engine and a generator driven by the engine can be used. As the charging/discharging device, various devices such as a storage battery (chemical battery) such as a lithium ion battery, a nickel metal hydride battery, and a lead battery, a capacitor, and a flywheel can be used.

In the example shown in FIG. 1 , the power supply device 8 is connected to the AC line 2 via the power conversion section 7 , the connection state switching section 6 and the switch 5 . The control unit 9 controls the operations of the power supply device 8 , the power conversion unit 7 , the connection state switching unit 6 and the switch 5 .

The power conversion unit 7 is realized using a circuit such as an inverter that converts the output power output from the power supply device 8 into predetermined power, for example, power of desired voltage, frequency, and phase. In the present embodiment, the power converter 7 converts the output power of the power supply device 8 into power of AC 100V and outputs the power to the connection state switching unit 6 .

The switch 5 switches between an open operation and a closed operation to switch between a state in which the power supply device 8 and the power conversion unit 7 are connected to the AC line 2 and a state in which the power supply device 8 and the power conversion unit 7 are not connected to the AC line 2. You can switch between states.

The distributed power supply system shown in FIG. 1 includes a first voltage measuring unit 10 that measures the voltage of the first voltage line 2a and a second voltage measuring unit 11 that measures the voltage of the second voltage line 2b. . The measurement results of the first voltage measurement section 10 and the second voltage measurement section 11 are transmitted to the control section 9 .

The connection state switching unit 6 changes the connection state between the single-phase three-wire AC line 2 having the first voltage line 2a, the second voltage line 2b, and the neutral line 2c connected to the electric power system 1 and the power conversion unit 7. a first connection state in which the power conversion unit 7 is connected to the first voltage line 2a and the neutral line 2c but not connected to the second voltage line 2b; It is possible to switch between a second connection state in which the portion 7 is connected and not connected to the first voltage line 2a.

The connection state switching unit 6 of this embodiment has a switching device 6a. In the switch 6a, a common contact C connected to the power converter 7 is connected to a contact A connected to the first voltage line 2a or a contact B connected to the second voltage line 2b. Also, in the connection state switching unit 6 , the neutral wire 2 c of the AC line 2 is connected to the power conversion unit 7 . Therefore, when the common contact C is connected to the contact A in the switch 6a, the AC 100V output of the power converter 7 is supplied to the first voltage line 2a and the neutral line 2c of the AC line 2. Further, when the common contact C is connected to the contact B in the switch 6a, the AC 100V output of the power converter 7 is supplied to the second voltage line 2b of the AC line 2 and the neutral line 2c.

Next, switching processing of the connection state switching unit 6 performed by the control unit 9 will be described.
FIG. 2 is a flowchart for explaining switching processing (switching processing A) of the connection state switching unit 6. As shown in FIG. In FIG. 2, the connection state switching unit 6 performs a switching process of switching to a randomly determined one of the first connection state and the second connection state at a predetermined timing. Specifically, in step #10, the control section 9 determines whether or not it is time to switch the connection state switching section 6 to perform switching processing.
For example, the control unit 9 determines that it is time to switch when the power supply device 8 starts operating.
Alternatively, when the elapsed time from the previous switching process reaches the set period, the control unit 9 determines that it is the switching timing to perform this switching process.
Alternatively, when the voltage of the first voltage line 2a measured by the first voltage measuring unit 10 or the voltage of the second voltage line 2b measured by the second voltage measuring unit 11 reaches or exceeds the set value, It is determined that it is time to switch to perform this switching process. The set value in this case can be set to, for example, a voltage value at which voltage rise suppression control is started, or a voltage value lower than that.

Then, when the control unit 9 determines that it is time to switch in step #10 (“Yes” in step #10), the control unit 9 proceeds to step #11 to select one of the first connection state and the second connection state. , switching processing is performed to switch to the randomly determined connection state.
On the other hand, when the control unit 9 determines that it is not the switching timing in step #10 ("No" in step #10), it returns to the beginning of this flow chart.

In this way, when the switching process A shown in FIG. 2 is performed, the power supply destination of the power supply device 8 is not fixed, but randomly changed at a predetermined timing. As a result, for example, even if a situation occurs in which the voltage of one of the first voltage line 2a and the second voltage line 2b becomes high, such a high voltage situation is fixed by the operation of the connection state switching unit 6. can be avoided.

FIG. 3 is a flowchart for explaining another switching process (switching process B) of the connection state switching unit 6. As shown in FIG. At a predetermined timing, the connection state switching unit 6 performs switching processing to switch to a different connection state between the first connection state and the second connection state. The unit 9 determines whether or not it is time to switch the connection state switching unit 6 to perform the switching process. The content of determination as to whether or not it is the switching timing is the same as described above.

Then, when the control unit 9 determines that it is time to switch in step #20, the control unit 9 proceeds to step #21 and switches to the connection state that is different from the first connection state or the second connection state. Perform switching processing.
On the other hand, when the control unit 9 determines that it is not the switching timing in step #20, it returns to the beginning of this flow chart.

As described above, when the switching process B shown in FIG. 3 is performed, the power supply destination of the power supply device 8 is not fixed, and is switched to a different connection state at a predetermined timing. As a result, for example, even if a situation occurs in which the voltage of one of the first voltage line 2a and the second voltage line 2b becomes high, such a high voltage situation is fixed by the operation of the connection state switching unit 6. can be avoided.

FIG. 4 is a flowchart for explaining another switching process (switching process C) of the connection state switching unit 6. As shown in FIG. The connection state switching unit 6 switches to the first connection state at a predetermined timing when the voltage of the first voltage line 2a is lower than the voltage of the second voltage line 2b, and changes the voltage of the second voltage line 2b to the first voltage line. When the voltage is lower than the voltage of the voltage line 2a, the switching process to switch to the second connection state is performed. Specifically, in step #30, the control unit 9 performs the switching process of the connection state switching unit 6 at the switching timing. Determine whether or not The content of determination as to whether or not it is the switching timing is the same as described above.

When the controller 9 determines in step #30 that it is time to switch, the controller 9 proceeds to step #31, and if the voltage of the first voltage line 2a is lower than the voltage of the second voltage line 2b, When the voltage of the second voltage line 2b is lower than the voltage of the first voltage line 2a, switching processing is performed to switch to the second connection state. By performing this switching process, when switching to the first connection state, the output of the power supply device 8 is supplied to the first voltage line 2a having a relatively low voltage, and when switching to the second connection state, the relatively The output of the power supply device 8 is supplied to the second voltage line 2b, which has a low voltage.
On the other hand, when the control unit 9 determines that it is not the switching timing in step #30, it returns to the beginning of this flow chart.

In this way, when the switching process C shown in FIG. 4 is performed, the connection state switching unit 6 does not fix the supply destination of the power supplied from the power supply device 8, and switches to a different one at a predetermined timing. Switch to connected state. As a result, for example, even if a situation occurs in which the voltage of one of the first voltage line 2a and the second voltage line 2b becomes high, such a high voltage situation is fixed by the operation of the connection state switching unit 6. can be avoided.

As described above, in the grid interconnection device 20 of the present embodiment, the connection state switching unit 6 switches the power supply destination of the power supply device 8 to the first voltage line 2a or the second voltage line 2b as necessary. can be changed. In other words, the power supplied from the power supply device 8 is not configured to be fixedly supplied to any one of the voltage lines. As a result, for example, even if a situation occurs in which the voltage of one of the first voltage line 2a and the second voltage line 2b becomes high, such a high voltage situation can be improved by operating the connection state switching unit 6. be able to. In addition, since the high voltage condition of the power system 1 can be improved, the economic merit of continuing the operation of the power supply device 8 can be obtained.

<Another embodiment>
<1>
Although the configuration of the system interconnection device 20 of the present invention has been described with a specific example in the above-described embodiment, the configuration can be changed as appropriate.
For example, the configuration of the connection state switching unit 6 is not limited to that described in the above embodiment, and can be changed as appropriate.

<2>
In the above embodiment, any one of switching processing A, switching processing B, and switching processing C may be performed at each switching timing. Alternatively, any two or three of the switching process A, the switching process B, and the switching process C may be sequentially performed at each switching timing.

<3>
The configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments unless there is a contradiction, and the configurations disclosed in this specification The embodiments are exemplifications, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the scope of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be used for a system interconnection device capable of maintaining good power quality in a power system.

1 Power system 2 AC line 2a First voltage line 2b Second voltage line 2c Neutral line 3 Power consumption device 4 Power consumption device 5 Switch 6 Connection state switching unit 7 Power conversion unit 8 Power supply device 9 Control unit 10 First voltage Measurement unit 11 Second voltage measurement unit

Claims (1)

A system interconnection device that connects a power supply device to a power system,
a power conversion unit that converts the output power output by the power supply device into a predetermined power;
A connection state between a single-phase three-wire AC line having a first voltage line, a second voltage line, and a neutral line connected to the electric power system and the power conversion unit is defined as a state of connection between the first voltage line and the neutral line. a first connection state in which the power conversion unit is connected to a line and is not connected to the second voltage line; and a first connection state in which the second voltage line, the neutral line and the power conversion unit are connected and the first voltage line a connection state switching unit capable of switching between a second connection state in which connection is not made to the
The connection state switching unit is a system interconnection device that performs switching processing to switch to a randomly determined connection state of the first connection state and the second connection state at a predetermined timing.

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