JP7424195B2 - Power conversion device, power conversion system, power supply system, and connection method for power conversion device - Google Patents

Description

The present disclosure relates to a power conversion device, a power conversion system, a power supply system, and a method for connecting power conversion devices.

With the spread of solar power generation, many ordinary households have already installed solar power generation systems. Consumers equipped with solar power generation systems have solar power generation panels installed on their roofs, as well as power conditioners (power conversion devices) installed indoors or outdoors. In recent years, systems that use storage batteries in combination with solar power generation have been proposed (see, for example, Patent Documents 1 to 4).

Patent Document 1 describes a hybrid type power conditioner that can be connected to both a solar power generation panel and a storage battery. Patent Document 2 describes a power storage power conditioner to which a transformer including a DC/DC conversion circuit for a solar power generation panel is externally attached.

Additionally, in recent years, there has been an increasing need to retrofit storage batteries to existing solar power generation systems. When retrofitting a storage battery, the power conditioner of the existing solar power generation system and the power conditioner of the storage battery will be installed separately. In a system with such a configuration, a storage battery is normally charged from a solar power generation panel via an AC power distribution line connected to a commercial power system. In this case, a problem arises in that the storage battery cannot be charged if a power outage occurs in the commercial power system.

The techniques described in Patent Documents 3 and 4 both aim to eliminate such inconveniences. Specifically, Patent Documents 3 and 4 disclose a system in which a storage battery is retrofitted to an existing solar power generation system, in which a route other than the commercial power system is separately provided to connect the power conditioner of the solar power generation system and the storage battery. By doing so, we propose a technology that allows storage batteries to be charged even during a power outage in the commercial power system.

JP2012-222908A JP 2019-103198 Publication Japanese Patent Application Publication No. 2017-135889 JP2019-198223A

If the power conditioner of the existing solar power generation system still has sufficient service life, why not replace it with a hybrid type power conditioner like the one described in Patent Document 1 just because a storage battery is newly installed? This creates a sense of ``waste'' on the user side. If an existing power conditioner and a hybrid type power conditioner are used together, the functions of the DC/DC conversion circuits will be duplicated, resulting in unnecessary functions.

On the other hand, the technology described in Patent Document 2 solves the problem of duplication of DC/AC conversion circuits between the power conditioner of the existing solar power generation system and the power conditioner of the storage battery when a storage battery is retrofitted. With the goal. For this reason, in Patent Document 2, the externally attached transformer is not provided with a DC/AC conversion circuit. However, the power conditioner of the existing solar power generation system is already provided with a DC/AC conversion circuit. Therefore, if the electricity storage power conditioner of Patent Document 2 is retrofitted to an existing solar power generation system, the above object cannot be achieved. From this, it can be said that the technology described in Patent Document 2 is a technology that assumes that a solar power generation system will be newly installed together with a storage battery. The same applies to the power conditioner of Patent Document 1.

In this way, Patent Documents 1 and 2 assume that a solar power generation system will be newly installed together with a storage battery, and Patent Documents 3 and 4 assume that a power conditioner exists in the existing solar power generation system. . That is, conventionally, a storage battery system (power conditioner) was selected depending on whether a solar power generation system was already installed or not. However, the appropriate selection may not be easy. In such a case, the power conditioners of Patent Documents 1 to 4 have a problem in that appropriate installation is hindered depending on whether a solar power generation system is already installed.

Therefore, the present disclosure provides a power conversion device, a power conversion system, a power supply system, and a power conversion system that can be introduced universally and without waste, regardless of whether a consumer already has an existing solar power generation system or is installing a new one together with a storage battery. , an object of the present invention is to provide a method for connecting power converters.

This disclosure includes the following inventions. However, the present invention is defined by the scope of the claims.

《Power converter》
The power conversion device of the present disclosure includes:
A power conversion device provided between a storage battery and a first AC line,
a DC/DC conversion circuit provided between the storage battery and the DC bus;
a DC/AC conversion circuit provided between the DC bus and the first AC line;
an AC auxiliary terminal for connection to a second AC line different from the first AC line;
an AC/DC conversion circuit provided between the AC auxiliary terminal and the DC bus;
a DC auxiliary terminal connected to the DC bus;
the DC/DC conversion circuit, the DC/AC conversion circuit, and a control unit that controls the AC/DC conversion circuit;
This is a power converter equipped with:

《Power conversion system》
Further, a power conversion system including the power conversion device as a first power conversion device and a second power conversion device connected to a solar power generation panel,
(a) The second AC power line is a power conversion system that is an independent output AC power line in the second power conversion device, or
(b) The DC auxiliary terminal is a power conversion system connected to the DC output circuit of the second power conversion device.

《Power system》
On the other hand, the present disclosure provides a power supply system including a storage battery and a power conversion device provided between the storage battery and a first AC line, the power conversion device comprising:
a DC/DC conversion circuit provided between the storage battery and the DC bus;
a DC/AC conversion circuit provided between the DC bus and the first AC line;
an AC auxiliary terminal for connection to a second AC line different from the first AC line;
an AC/DC conversion circuit provided between the AC auxiliary terminal and the DC bus;
a DC auxiliary terminal connected to the DC bus;
the DC/DC conversion circuit, the DC/AC conversion circuit, and a control unit that controls the AC/DC conversion circuit;
It is a power system equipped with

《How to connect the power converter》
The present disclosure provides a DC/DC conversion circuit provided between a storage battery and a DC bus, a DC/AC conversion circuit provided between the DC bus and a first AC line, and a DC/AC conversion circuit provided between the DC bus and a first AC line. is a power converter comprising: an AC/DC conversion circuit provided between the DC bus and an AC auxiliary terminal for connection with another second AC power line; and a DC auxiliary terminal connected to the DC bus. A method of connecting the device,
If AC power can be supplied from a source other than the commercial power system, AC power is supplied to the AC auxiliary terminal, and if DC power can be supplied from a DC power supply, DC power is supplied to the DC auxiliary terminal. This is the connection method.

According to the present disclosure, it is possible to provide a power conversion device, a power conversion system, a power supply system, and a method for connecting the power conversion device that can be introduced for general purpose and without waste, regardless of whether a solar power generation system is already installed or newly installed. .

FIG. 1 is a single-line connection diagram showing an example of an existing solar power generation system. FIG. 2 is a single-line connection diagram showing an example in which a power supply system using a storage battery is added to the existing solar power generation system shown in FIG. 1 as a retrofit. FIG. 3 is an example of a flowchart showing the operation of the power conversion device by the control unit. FIG. 4 is a single-line connection diagram showing an example of a newly installed two-DC power supply system including a solar power generation system and a storage battery power supply system. FIG. 5 is an example of a flowchart showing the operation of the power converter by the control unit at the time of starting operation. FIG. 6 is an example of a flowchart showing the operation of the DC/AC conversion circuit during grid-connected operation of the power conversion device. FIG. 7 is an example of a flowchart showing the operation of the DC/DC conversion circuit during grid-connected operation of the power conversion device. FIG. 8 is a single-line connection diagram showing an example of a power supply system with two DC power supplies and one AC power supply, including a solar power generation system, a power supply system using a storage battery, and a fuel cell system.

[Description of embodiments of the present disclosure]
The embodiment of the present disclosure includes at least the following as its gist.

(1) What is disclosed is a power conversion device provided between a storage battery and a first AC line, which includes a DC/DC conversion circuit provided between the storage battery and a DC bus, and a DC/DC conversion circuit provided between the storage battery and a DC bus. A DC/AC conversion circuit provided between the first AC power line, an AC auxiliary terminal provided for connection to a second AC power line different from the first AC power line, and a DC/AC conversion circuit provided between the AC auxiliary terminal and the AC power line. an AC/DC conversion circuit provided between the DC bus, a DC auxiliary terminal connected to the DC bus, the DC/DC conversion circuit, the DC/AC conversion circuit, and the AC/DC conversion circuit. and a control unit for controlling.

In the power conversion device as described above, power can be converted bidirectionally between the storage battery and the AC line, and additionally, it can be connected to another external AC line or DC line. For example, a consumer who has already installed a solar power generation system can take in independent AC output from the power conversion device of the solar power generation system. In the case of a customer who also installs a new solar power generation system at the same time, it is sufficient to take in the normal DC output from the DC/DC conversion circuit of the solar power generation system. In this way, it is possible to provide a versatile power conversion device that can handle both alternating current and direct current as auxiliary input (or output). Therefore, it is possible to provide a power conversion device that can be introduced for general purpose without waste.

(2) In the power converter according to (1), a first connection state in which AC power is supplied to the AC auxiliary terminal from the outside and DC power is not supplied to the DC auxiliary terminal from the outside; DC power is supplied from the outside to the AC auxiliary terminal, and the AC auxiliary terminal is in a second connection state in which AC power can be supplied to the outside. A third connection state in which AC power is supplied from good.
In this case, when installing the power conversion device, a desired connection state can be easily set according to the conditions of existing or newly installed related equipment.

(3) The power conversion system is a power conversion system that includes the power conversion device of (1) above as a first power conversion device and a second power conversion device connected to a solar power generation panel. The second AC line is an independent output AC line in the second power converter.
In this case, independent output can be effectively utilized.

(4) Another power conversion system includes the power conversion device of (1) above as a first power conversion device, and a second power conversion device connected to a solar power generation panel, and The auxiliary terminal is connected to the DC output circuit of the second power converter.
In this case, the DC/AC conversion circuit (inverter circuit) can be omitted in the second power conversion device.

(5) In yet another power conversion system, in (4) above, the AC/DC conversion circuit is capable of bidirectional power conversion, and the control unit is configured to convert the AC/DC conversion circuit from direct current to alternating current. The AC auxiliary output is controlled to be provided to the AC auxiliary terminal by performing power conversion to the AC auxiliary terminal.
In this case, AC power can be provided from the AC auxiliary terminal to the outside.

(6) This is also a power supply system including a storage battery and a power conversion device provided between the storage battery and a first AC line, wherein the power conversion device connects the storage battery and a DC bus. a DC/AC conversion circuit provided between the DC bus and the first AC line, and a second AC line separate from the first AC line. an AC auxiliary terminal provided for connection with the AC auxiliary terminal, an AC/DC conversion circuit provided between the AC auxiliary terminal and the DC bus, a DC auxiliary terminal connected to the DC bus, and the DC/DC conversion circuit; The DC/AC conversion circuit and a control section that controls the AC/DC conversion circuit are provided.

The power conversion device of the power supply system described above can perform bidirectional power conversion between the storage battery and the AC line, and can also be supplementarily connected to other external AC or DC lines. can. For example, a consumer who has already installed a solar power generation system can take in independent AC output from the power conversion device of the solar power generation system. In the case of a customer who also installs a new solar power generation system at the same time, it is sufficient to take in the normal DC output from the DC/DC conversion circuit of the solar power generation system. In this way, it is possible to provide a versatile power conversion device that can handle both alternating current and direct current as auxiliary input (or output). Therefore, a power supply system can be configured using a power conversion device that can be introduced for general purpose without waste.

(7) The power supply system of (6) above includes a fuel cell system that supplies AC power to the AC auxiliary terminal, and a power conversion device for solar power generation that supplies DC power to the DC auxiliary terminal. It's okay.
In this case, both auxiliary AC and DC inputs can be obtained.

(8) From the viewpoint of the method, a DC/DC conversion circuit provided between the storage battery and the DC bus, a DC/AC conversion circuit provided between the DC bus and the first AC line, and the first an AC/DC conversion circuit provided between the DC bus and an AC auxiliary terminal for connection to a second AC line different from the first AC line; a DC auxiliary terminal connected to the DC bus; The connection method for a power converter equipped with a , a method for connecting a power conversion device, which supplies DC power to the DC auxiliary terminal.

In the connection method of the power conversion device as described above, in addition to being able to perform bidirectional power conversion between the storage battery and the AC line, it is also possible to connect to another external AC line or DC line as an auxiliary. can. For example, a consumer who has already installed a solar power generation system can take in independent AC output from the power conversion device of the solar power generation system. In the case of a customer who also installs a new solar power generation system at the same time, it is sufficient to take in the normal DC output from the DC/DC conversion circuit of the solar power generation system. In this way, it is possible to provide a versatile connection method that can support both alternating current and direct current as auxiliary input (or output) when connecting the power converter. Therefore, it is possible to provide a method for connecting a power conversion device that can be introduced for general purpose use without waste.

(9) In the method for connecting a power converter according to (8) above, in addition to the AC output from the DC/AC conversion circuit, the AC/DC conversion circuit converts power from DC to AC to output an AC auxiliary output. may be provided to the load.
In this case, AC power can also be provided to the load from the AC auxiliary terminal.

[Details of embodiments of the present disclosure]
Hereinafter, specific examples of the power conversion device, power conversion system, and power supply system of the present disclosure will be described with reference to the drawings.

《First embodiment》
FIG. 1 is a single-line connection diagram showing an example of an existing solar power generation system 100. In the figure, a power conversion device 1 is provided between a photovoltaic power generation panel 2 that outputs DC power and an AC line 4 connected to a commercial power system 3. The power conversion device 1 includes a DC/DC conversion circuit 11 , a DC/AC conversion circuit 12 , a control section 13 , a grid connection relay 14 , and an independent output relay 15 . A consumer load 5 is connected to the AC line 4. The output end side of the independent output relay 15 may be open, but here it is assumed that the load 6 is connected. The control unit 13 includes, for example, a computer, and implements necessary control functions by the computer executing software (computer program). The software is stored in a storage device (not shown) of the control unit 13.

The control unit 13 uses the DC/DC conversion circuit 11 to boost the output voltage of the solar power generation panel 2 to a predetermined voltage, and also performs MPPT (Maximum Power Point Tracking) to draw the maximum power at that time from the solar power generation panel 2. ) control. The DC/AC conversion circuit 12 converts the power output by the DC/DC conversion circuit 11 from direct current to alternating current and outputs the same.

In the power conversion device 1 that is in grid-connected operation with the commercial power grid 3, the grid-connected relay 14 is closed and the independent output relay 15 is opened. The voltage of the AC line 4 during grid-connected operation is determined by the commercial power grid 3, and is, for example, 202 VAC. The DC/AC conversion circuit 12 performs current control. In the power converter 1 during self-sustaining output operation, the grid interconnection relay 14 is open and the self-sustaining output relay 15 is closed. The DC/AC conversion circuit 12 in this case performs voltage control, and the output voltage is, for example, AC101V. This output voltage is supplied to the load 6.

FIG. 2 is a single-line connection diagram showing an example in which a power supply system 200 using a storage battery is added to the existing solar power generation system 100 shown in FIG. 1 as a retrofit. In the figure, the configuration of the solar power generation system 100 is the same as that in FIG. 1, so the same reference numerals are given and the explanation will be omitted. Further, a load 5 is connected to the AC line 4 , and the load 6 is connected to the independent output side of the power converter 7 . The two power conversion devices 1 and 7 constitute a power conversion system 31.

In a power supply system 200 attached to a solar power generation system 100, a power conversion device 7 is provided between a storage battery 8 and an AC line 4 connected to a commercial power system 3. The power conversion device 7 includes a DC/DC conversion circuit 71, a DC/AC conversion circuit 72, a control section 73, a grid connection relay 74, an independent output relay 75, an AC/DC conversion circuit 76, and a setting section 77. There is. The control unit 73 includes, for example, a computer, and implements necessary control functions by the computer executing software (computer program). The software is stored in a storage device (not shown) of the control unit 73. The DC/DC conversion circuit 71, the DC/AC conversion circuit 72, and the AC/DC conversion circuit 76 are controlled by the control section 73.

The DC/DC conversion circuit 71, the DC/AC conversion circuit 72, and the AC/DC conversion circuit 76 are all connected to a DC bus 78. DC/DC conversion circuit 71 is provided between storage battery 8 and DC bus 78. The DC/AC conversion circuit 72 is provided between the DC bus 78 and the AC line 4.

When discharging the storage battery 8 , the DC/DC conversion circuit 71 boosts the output voltage of the storage battery 8 and sends it to the DC bus 78 . The DC/AC conversion circuit 72 converts the voltage of the DC bus 78 into an alternating current voltage and outputs it. In the case of grid-connected output, for example, 202 VAC is output, and in the case of independent output, for example, 101 VAC is output.
The DC/AC conversion circuit 72 when charging the storage battery 8 converts the voltage of the AC line 4 into a DC voltage and supplies it to the DC bus 78 . The DC/DC conversion circuit 71 steps down the voltage of the DC bus 78 to a voltage suitable for charging the storage battery 8, and charges the storage battery 8.

An AC auxiliary terminal _TAC is provided on the AC side of the AC/DC conversion circuit 76. Therefore, the AC/DC conversion circuit 76 is provided between the _AC auxiliary terminal TAC and the DC bus 78. For example, if the AC line 4 is referred to as a "first AC line 4," the AC auxiliary terminal _TAC is connected to the second AC line 9. The AC line 9 is an electric line that can supply independent output from the power conversion device 1 in the solar power generation system 100. Further, a DC auxiliary terminal _TDC is connected to the DC bus 78, to which an external DC circuit can be connected. However, in the state shown in FIG. 2, the _DC auxiliary terminal TDC is open and not connected to an external DC circuit.

The operator who installed the power supply system 200 operates the setting section 77 to cause the control section 73 to recognize that the connection state as shown in FIG. 2 is established. The connection state shown in FIG. 2 is a state in which AC power is supplied from the outside to _{the AC} auxiliary terminal TAC via the AC line 9, and no DC power is supplied from the outside to the _DC auxiliary terminal TDC (the first connection status).

In the power converter 7 that is in grid-connected operation with the commercial power grid 3, the grid-connected relay 74 is closed and the independent output relay 75 is opened. When the power conversion device 1 of the solar power generation system 100 is also performing grid-connected operation, the two power conversion devices 1 and 7 are connected in parallel to the AC power line 4 . The power conversion device 1 of the solar power generation system 100 performs only one-way operation of supplying power to the AC line 4. The power conversion device 7 of the power supply system 200 is capable of both supplying power to the AC line 4 and charging the storage battery 8 based on the power of the AC line 4 . In this way, it is possible to realize a power supply system 300 that uses the existing solar power generation system 100 together with the power supply system 200 based on the storage battery 8.

On the other hand, in the power converter 7 during the independent output operation, the grid interconnection relay 74 is open and the independent output relay 75 is closed. The DC/AC conversion circuit 72 in this case performs voltage control, and the output voltage is, for example, AC101V. This output voltage is supplied to the load 6. Further, at this time, the power converter 1 is also performing independent output operation. The independent output of the power converter 1 is given to the AC auxiliary terminal TAC of the power converter 7 via the _AC line 9. The AC/DC conversion circuit 76 converts the input independent output AC voltage into a DC voltage and provides it to the DC bus 78 . In this way, also regarding self-sustaining operation, it is possible to realize a power supply system 300 that uses the existing solar power generation system 100 together with the power supply system 200 based on the storage battery 8.

FIG. 3 is an example of a flowchart showing the operation of the power conversion device 7 by the control unit 73. The power conversion device 7 that has received the operation start command starts a control operation, and determines whether or not the voltage of the storage battery 8 is normal using a voltage sensor built in the DC/DC conversion circuit 71 (step S1). If normal, the power conversion device 7 starts a boost operation in the DC/DC conversion circuit 71 (step S2).

Next, the power conversion device 7 determines whether the commercial power grid 3 is normal (power outage) using the voltage sensor built into the DC/AC conversion circuit 72 with the grid connection relay 74 open (step S3). If normal, the power conversion device 7 executes grid-connected operation (step S4).

If the commercial power system 3 is not in a normal state, the determination in step S3 is "NO". In this case, the power conversion device 7 determines a power outage in the system, and when a power outage is confirmed, starts independent operation (step S5). After starting the self-sustaining operation, the power conversion device 7 determines whether the voltage of the auxiliary input to the _AC auxiliary terminal TAC is equal to or higher than the threshold value using the voltage sensor built into the AC/DC conversion circuit 76 (step S6). If the voltage is equal to or higher than the threshold value, the power conversion device 7 operates the AC/DC conversion circuit 76 to charge the DC bus 78 by outputting a DC voltage (step S7). If the voltage is less than the threshold value, the power conversion device 7 does not operate the AC/DC conversion circuit 76 (step S8).

Note that in step S1, when the voltage of the storage battery is not normal, the power conversion device 7 determines that the storage battery is abnormal, and stops the operation (step S9).

《Second embodiment》
FIG. 4 is a single-line connection diagram showing an example of a newly installed two-DC power supply system 400 including a solar power generation system 100 and a power supply system 200 using a storage battery. In the figure, a power conversion device 1A is connected to a solar power generation panel 2 that outputs DC power. The power conversion device 1A includes a DC/DC conversion circuit 11 and a control section 13. The control unit 13 includes, for example, a computer, and implements necessary control functions by the computer executing software (computer program). The software is stored in a storage device (not shown) of the control unit 13.

The control unit 13 uses the DC/DC conversion circuit 11 to boost the output voltage of the solar power generation panel 2 to a predetermined voltage, and performs MPPT control to draw the maximum power at that time from the solar power generation panel 2. The power conversion device 1A does not perform AC output by itself, but supplies DC output to the output terminal T _out . Therefore, the power conversion device 1A does not require a DC/AC conversion circuit (inverter circuit).

In FIG. 4, the configuration of the power supply system 200 is the same as that in FIG. 2, so the same reference numerals are given and the explanation will be omitted. Further, a load 5 is connected to the AC line 4, and a load 6 is connected to the independent output end side. The power supply system 200 is different from FIG. 2 in that the _DC auxiliary terminal TDC and the output terminal _Tout of the power converter 1A are connected to each other via the DC line 10, and the _AC auxiliary terminal TAC is the auxiliary output. This is a useful point. For example, a load 20 can be connected to the _AC auxiliary terminal TAC. The two power conversion devices 1A and 7 constitute a power conversion system 32.

The operator who installed the power supply system 400 operates the setting section 77 to cause the control section 73 to recognize that the connection state as shown in FIG. 4 is established. The connection state shown in FIG. 4 means that DC power is supplied from the outside to the _DC auxiliary terminal TDC via the DC line 10, and _AC auxiliary terminal TAC can supply AC power to the outside via the AC line 9. state (second connection state).

When discharging the storage battery 8 , the DC/DC conversion circuit 71 boosts the output voltage of the storage battery 8 and sends it to the DC bus 78 . The output of the power conversion device 1A is also provided to the DC bus 78. The DC/AC conversion circuit 72 converts the voltage of the DC bus 78 into an alternating current voltage and outputs it. In the case of grid-connected output, for example, 202 VAC is output, and in the case of independent output, for example, 101 VAC is output.
The DC/AC conversion circuit 72 when charging the storage battery 8 converts the voltage of the AC line 4 into a DC voltage and supplies it to the DC bus 78 . The DC/DC conversion circuit 71 steps down the voltage of the DC bus 78 to a voltage suitable for charging the storage battery 8, and charges the storage battery 8. Furthermore, the storage battery 8 can also be charged based on the DC output from the power conversion device 1A without depending on the AC line 4.

In the power converter 7 that is in grid-connected operation with the commercial power grid 3, the grid-connected relay 74 is closed and the independent output relay 75 is opened. When the power conversion device 1A of the solar power generation system 100 also provides DC output, two systems of the solar power generation panel 2 and the DC/DC conversion circuit 11, and the storage battery 8 and the DC/DC conversion circuit 71 are provided. The DC power supply is connected in parallel to the DC bus 78. The power conversion device 1A of the solar power generation system 100 performs only one-way operation of supplying power to the DC bus 78 with direct current. The power conversion device 7 of the power supply system 200 supplies power to the AC power line 4 and charges the storage battery 8 based on the power of the AC power line 4 or based on the power sent from the power conversion device 1A. Both operations are possible. In this way, a power supply system 400 that uses both the solar power generation system 100 and the power supply system 200 based on the storage battery 8 can be realized.

On the other hand, in the power converter 7 during the independent output operation, the grid interconnection relay 74 is open and the independent output relay 75 is closed. The DC/AC conversion circuit 72 in this case performs voltage control, and the output voltage is, for example, AC101V. This output voltage is supplied to the load 6. Further, at this time, if solar power generation is being performed, the output of the power conversion device 1A is given to the DC bus 78 from _{the DC} auxiliary terminal TDC. In this way, it is possible to realize a power supply system 400 that uses both the solar power generation system 100 and the power supply system 200 based on the storage battery 8 in terms of self-sustaining operation.

(Operation at start of operation)
FIG. 5 is an example of a flowchart showing the operation of the power conversion device 7 by the control unit 73 at the time of starting operation. The power conversion device 7 that has received the operation start command starts a control operation, and determines whether the voltage of the storage battery 8 is normal using the voltage sensor built in the DC/DC conversion circuit 71 (step S11). If normal, the power conversion device 7 starts a boost operation in the DC/DC conversion circuit 71 (step S12).

Next, the power conversion device 7 determines whether the commercial power grid 3 is normal (power outage) using the voltage sensor built into the DC/AC conversion circuit 72 with the grid connection relay 74 open (step S13). If normal, the power conversion device 7 executes grid-connected operation (step S14).

If the commercial power system 3 is not in a normal state, the determination in step S13 is "NO". In this case, the power conversion device 7 determines a power outage in the grid, and if a power outage is confirmed, starts independent operation (step S15).

Note that, in step S11, if the voltage of the storage battery becomes abnormal, the power conversion device 7 determines that the storage battery is abnormal, and stops the operation (step S16).

(Operation during grid-connected operation)
FIG. 6 is an example of a flowchart showing the operation of the DC/AC conversion circuit 72 during grid-connected operation of the power conversion device 7. After starting the grid-connected operation, the power conversion device 7 performs DC bus voltage stabilization control using the DC/AC conversion circuit 72 so that the voltage of the DC bus 78 is kept constant (step S21). The power from the power converter 1A is input to the _DC auxiliary terminal TDC, but the power generated by the photovoltaic panel 2 (PV) varies depending on the sunlight conditions, and increases or decreases (step S22). When the power input from the power conversion device 1A fluctuates, the voltage of the DC bus 78 also fluctuates.

Therefore, the power conversion device 7 determines whether the voltage of the DC bus 78 has changed (step S23). If it is determined that the voltage has fluctuated, the power conversion device 7 increases or decreases (current control) the output current of the DC/AC conversion circuit 72 to stabilize the DC bus voltage (step S24). The DC/AC conversion circuit 72 has an upper limit value of output current (output power) due to the capabilities of switching elements and reactors. When the power generated by the solar power generation panel 2 is large and the output current of the DC/AC conversion circuit 72 reaches the upper limit value, the power generated can be prevented from being wasted by charging the storage battery 8. However, when the output current of the DC/AC conversion circuit 72 reaches the upper limit value and the charging current of the storage battery 8 also reaches the upper limit value, there is no place for the generated power to go, and there is no choice but to suppress the power generation. Particularly, in the case of so-called overloading in which the power generated by the solar power generation panel 2 exceeds the maximum output of the power conversion device 7, such a state may occur.

Therefore, the power conversion device 7 determines whether the output current of the DC/AC conversion circuit 72 is at least the upper limit value and whether the charging current of the storage battery 8 is also at least the upper limit value (step S25). If "YES" here, the power conversion device 7 causes the AC/DC conversion circuit 76 to convert from DC to AC (reverse conversion), and transfers the AC from the AC auxiliary terminal T _AC to the load 20. A state is set in which power can be output (step S6). In this way, the power generated by the solar power generation panel 2 can be fully utilized.

On the other hand, if the determination in step S25 is "NO", the power generated by the solar power generation panel 2 is being used without wastage by supplying power to the load 5 and charging the storage battery 8, so no special operation is performed (step S27). Further, if no particular fluctuation is observed in the DC bus voltage in step S23, the power conversion device 7 holds the output current of the DC/AC conversion circuit 72 constant (step S28).

FIG. 7 is an example of a flowchart showing the operation of the DC/DC conversion circuit 71 during grid-connected operation of the power conversion device 7. After starting grid-connected operation, the power conversion device 7 uses the DC/DC conversion circuit 71 to determine a target value of power to be output to the AC power line 4, and performs EMS (Energy Management System) control to output power in accordance with the target value. Step S31).

The power from the power conversion device 1A is input to the _DC auxiliary terminal TDC, but the power generated by the photovoltaic panel 2 (PV) varies depending on the sunlight conditions, and increases or decreases (step S32). When the power input from the power conversion device 1A fluctuates, the output current of the DC/AC conversion circuit 72 also fluctuates.

Therefore, the power conversion device 7 determines whether the output current of the DC/AC conversion circuit 72 has changed (step S33). If it is determined that the power has changed, the power conversion device 7 updates the power target value of the DC/DC conversion circuit 71 (step S34). Here, similarly to step S25 in FIG. 6, the power conversion device 7 determines whether the output current of the DC/AC conversion circuit 72 is at least the upper limit value and the charging current of the storage battery 8 is also at least the upper limit value. , is determined (step S35). If "YES" here, the power conversion device 7 causes the AC/DC conversion circuit 76 to convert from DC to AC (reverse conversion), and transfers the AC from the AC auxiliary terminal T _AC to the load 20. The state is set so that electric power can be output (step S36). In this way, the power generated by the solar power generation panel 2 can be fully utilized.

On the other hand, if the determination in step S35 is "NO", the power generated by the solar power generation panel 2 is being used without wastage by supplying power to the load 5 and charging the storage battery 8, so no special operation is performed (step S37). Further, if no particular fluctuation is observed in the output current of the DC/AC conversion circuit 72 in step S33, the power conversion device 7 holds the power target value of the DC/DC conversion circuit 71 constant (step S38).

In the above case, the DC/DC conversion circuit 71 performs EMS control and the DC/AC conversion circuit 72 performs DC bus voltage stabilization control, but the DC/AC conversion circuit 72 performs EMS control and DC It is also possible for the /DC conversion circuit 71 to perform DC bus voltage stabilization control.

In this way, a power supply system 400 that uses both the solar power generation system 100 and the power supply system 200 based on the storage battery 8 can be realized.

《Third embodiment》
FIG. 8 is a single-line connection diagram showing an example of a power supply system 500 with two DC power supplies and one AC power supply, including a solar power generation system 100, a power supply system 200 using a storage battery, and a fuel cell system 21. Components common to those in FIG. 4 are given the same reference numerals and descriptions thereof will be omitted. The difference from FIG. 4 is that the fuel cell system (including the power converter) 21 is connected to the _AC auxiliary terminal TAC of the power converter 7. Unlike FIG. 4, the AC/DC conversion circuit 76 receives auxiliary input from the fuel cell system 21 and performs conversion from alternating current to direct current.

The operator who installed the power supply system 500 operates the setting section 77 to cause the control section 73 to recognize that the connection state as shown in FIG. 8 is established. The connection state shown in FIG. 8 means that DC power is supplied from the outside to the _DC auxiliary terminal TDC via the DC line 10, and AC power is also supplied to the _AC auxiliary terminal TAC from the outside via the AC line 9. (third connection state).

When discharging the storage battery 8 , the DC/DC conversion circuit 71 boosts the output voltage of the storage battery 8 and sends it to the DC bus 78 . The DC bus 78 is also provided with the output of the power converter 1A. Furthermore, with the auxiliary input from the fuel cell system 21, the AC/DC conversion circuit 76 performs conversion from alternating current to direct current, and sends power to the DC bus 78. The DC/AC conversion circuit 72 converts the voltage of the DC bus 78 into an alternating current voltage and outputs it. In the case of grid-connected output, for example, 202V AC is output, and in the case of independent output, for example, 101V AC is output.

The DC/AC conversion circuit 72 when charging the storage battery 8 converts the voltage of the AC line 4 into a DC voltage and supplies it to the DC bus 78 . The DC/DC conversion circuit 71 steps down the voltage of the DC bus 78 to a voltage suitable for charging the storage battery 8, and charges the storage battery 8. Furthermore, the storage battery 8 can be charged based on the DC output from the power conversion device 1A or the auxiliary input from the fuel cell system 21 without depending on the AC line 4.

In the power converter 7 that is in grid-connected operation with the commercial power grid 3, the grid-connected relay 74 is closed and the independent output relay 75 is opened. The power converter 1A of the solar power generation system 100 also provides a DC output, and if an auxiliary input from the fuel cell system 21 is provided, the solar power generation panel 2, the DC/DC conversion circuit 11, and the storage battery 8 A total of three DC power sources are connected in parallel to the DC bus 78: the DC/DC conversion circuit 71, and the auxiliary input from the fuel cell system 21 converted to DC by the AC/DC conversion circuit 76. This is a connected relationship.

The power conversion device 1A of the solar power generation system 100 performs only one-way operation of supplying power to the DC bus 78 with direct current. The AC/DC conversion circuit 76 that receives auxiliary input from the fuel cell system 21 also performs only a conversion operation from alternating current to direct current. The power conversion device 7 of the power supply system 200 charges the storage battery 8 based on the operation of supplying power to the AC line 4 and the power sent from the AC line 4, the power conversion device 1A, or the fuel cell system 21. Both operations are possible. In this way, it is possible to realize a power supply system 500 that uses the solar power generation system 100, the power supply system 200 based on the storage battery 8, and the auxiliary input from the fuel cell system 21 in combination.

On the other hand, in the power converter 7 during the independent output operation, the grid interconnection relay 74 is open and the independent output relay 75 is closed. The DC/AC conversion circuit 72 in this case performs voltage control, and the output voltage is, for example, AC101V. This output voltage is supplied to the load 6. Further, at this time, if solar power generation is being performed, the output of the power conversion device 1A is given to the DC bus 78 from _{the DC} auxiliary terminal TDC. The auxiliary input of the fuel cell system 21 is also provided to the DC bus 78 via the AC/DC conversion circuit 76 . In this way, also regarding self-sustaining operation, it is possible to realize a power supply system 500 that uses the solar power generation system 100, the power supply system 200 based on the storage battery 8, and the auxiliary input from the fuel cell system 21 in combination.

《Summary of disclosure》
A power conversion device 7 of the present disclosure is provided between a storage battery 8 and a first AC line 4, and a DC/DC conversion circuit 71 is provided between the storage battery 8 and a DC bus 78. A DC/AC conversion circuit 72 is provided between the AC line 4 and the first AC line 4, respectively. Then, an AC auxiliary terminal TAC provided for connection with the second AC power line 9, an AC/DC conversion circuit 76 provided between _{the AC auxiliary} terminal TAC and the DC bus 78, and an AC/DC conversion circuit 76 connected to the DC bus 78. It is equipped with a _DC auxiliary terminal TDC.

Such a power conversion device 7 can perform bidirectional power conversion between the storage battery 8 and the AC line 4, and can also be supplementarily connected to another external AC line 9 or a DC line 10. Can be done. A customer who has already installed the solar power generation system 100 can take in independent AC output from the power conversion device 1 of the solar power generation system 100. In the case of a consumer who is also installing a new solar power generation system 100 at the same time, the normal DC output may be taken in from the DC/DC conversion circuit 11 in the power conversion device 1A of the solar power generation system 100. In this way, it is possible to provide a versatile power converter device 7 that can handle both alternating current and direct current as auxiliary input (or output). Although the power conversion device 7 has a common circuit configuration, it exhibits versatility. That is, it is applicable to any of the following: installation in an existing solar power generation system 100, new installation together with the solar power generation system 100, and three power supply systems including a fuel cell system. Therefore, it is possible to provide the power conversion device 7 that can be introduced for general purpose use without waste.

《Addendum》
It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present invention is indicated by the claims, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1,1A power converter 2 solar power generation panel 3 commercial power system 4 (first) AC line 5,6 load 7 power converter 8 storage battery 9 (second) AC line 10 DC line 11 DC/DC conversion circuit 12 DC/AC conversion circuit 13 Control unit 14 Grid connection relay 15 Independent output relay 20 Load 21 Fuel cell system 31, 32 Power conversion system 71 DC/DC conversion circuit 72 DC/AC conversion circuit 73 Control unit 74 Grid connection relay 75 Independent output relay 76 AC/DC conversion circuit 77 Setting unit 78 DC bus 100 Solar power generation system 200 Power supply system 300 Power supply system 400 Power supply system 500 Power supply system T _{AC AC} auxiliary terminal T _{DC DC} auxiliary terminal T _out output terminal

Claims (9)

A grid-interconnectable power conversion device provided between a storage battery and a first AC line,
a DC/DC conversion circuit provided between the storage battery and the DC bus;
a DC/AC conversion circuit provided between the DC bus and the first AC line;
an AC auxiliary terminal for connection to a second AC power line that is separate from the first AC power line and is not connected to the first AC power line during grid-connected operation ;
an AC/DC conversion circuit provided between the AC auxiliary terminal and the DC bus;
a DC auxiliary terminal connected to the DC bus;
the DC/DC conversion circuit, the DC/AC conversion circuit, and a control unit that controls the AC/DC conversion circuit;
A power converter equipped with a first connection state in which the AC auxiliary terminal is supplied with AC power from the outside and the DC auxiliary terminal is not supplied with DC power from the outside; and a first connection state in which the DC auxiliary terminal is supplied with DC power from the outside and the AC auxiliary terminal is A second connection state in which AC power can be supplied to the outside, and a third connection state in which DC power is supplied to the DC auxiliary terminal from the outside, and AC power is supplied to the AC auxiliary terminal from the outside. , and includes a setting section for selectively selecting .
The power converter device according to claim 1, wherein the control unit executes control based on the selection in the setting unit. A power conversion system comprising the power conversion device according to claim 1 as a first power conversion device and a second power conversion device connected to a solar power generation panel,
The second AC power line is a power conversion system that is an independent output AC power line in the second power conversion device. A power conversion system comprising the power conversion device according to claim 1 as a first power conversion device and a second power conversion device connected to a solar power generation panel,
A power conversion system in which the DC auxiliary terminal is connected to a DC output circuit of the second power conversion device. The AC/DC conversion circuit is capable of bidirectional power conversion,
The power conversion system according to claim 4, wherein the control unit controls the AC/DC conversion circuit to provide an AC auxiliary output to the AC auxiliary terminal by converting power from DC to AC. A power supply system including a storage battery and a grid-connectable power conversion device provided between the storage battery and a first AC line, the power conversion device comprising:
a DC/DC conversion circuit provided between the storage battery and the DC bus;
a DC/AC conversion circuit provided between the DC bus and the first AC line;
an AC auxiliary terminal for connection to a second AC power line that is separate from the first AC power line and is not connected to the first AC power line during grid-connected operation ;
an AC/DC conversion circuit provided between the AC auxiliary terminal and the DC bus;
a DC auxiliary terminal connected to the DC bus;
the DC/DC conversion circuit, the DC/AC conversion circuit, and a control unit that controls the AC/DC conversion circuit;
Power system equipped with. a fuel cell system that supplies AC power to the AC auxiliary terminal;
The power supply system according to claim 6, further comprising: a power conversion device for solar power generation that supplies DC power to the DC auxiliary terminal. A DC/DC conversion circuit provided between a storage battery and a DC bus, a DC/AC conversion circuit provided between the DC bus and a first AC line, and an AC line other than the first AC line. an AC/DC conversion circuit provided between the DC bus and an AC auxiliary terminal for connection to a second AC line that is not connected to the first AC line during interconnection operation; A method for connecting a grid -interconnectable power converter equipped with a DC auxiliary terminal connected to a DC bus,
If AC power can be supplied from a source other than the commercial power system, AC power is supplied to the AC auxiliary terminal, and if DC power can be supplied from a DC power supply, DC power is supplied to the DC auxiliary terminal. Connection method. The power conversion device according to claim 8, wherein in addition to the AC output by the DC/AC conversion circuit, the AC/DC conversion circuit provides an AC auxiliary output to the load by converting power from DC to AC. Connection method.

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