Power storage system, power storage device, and operation method for power storage device

The present invention generally relates to an operation method of a power storage system, a power storage device, and a power storage device, and more particularly, an operation method of a power storage system, a power storage device, and a power storage device for operating a plurality of power storage devices in parallel.

Conventionally, there is a system in which a plurality of power storage devices are operated in parallel to supply electric power to a load.

For example, the technique described in Patent Document 1 includes a second power storage circuit using an electric double layer capacitor in addition to a first power storage circuit using a storage battery. When the power consumption of the external load increases momentarily, the power is supplied from the second power storage circuit and then the power is supplied from the first power storage circuit.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2002-110210</text></patcit></p>

<p> Conventionally, there is a power storage system in which a plurality of power storage devices are operated in parallel.</p><p> In such a power storage system, the power storage device outputs 2-wire power, but some users are required to use single-phase 3-wire power. Furthermore, with a simple system configuration, single-phase 3-wire power is required. It is also required to increase the power capacity of the system.</p><p> The present invention has been made in view of the above reasons, and an object of the present invention is to allow a plurality of power storage devices to be operated in parallel to supply single-phase three-wire power, and to have a simple system configuration. It is an object of the present invention to provide a power storage system, a power storage device, and an operation method of the power storage device that can easily increase the power capacity of a single-phase three-wire system.</p>

<p> The power storage system of the present invention has a storage battery and a power conditioner that converts the DC power of the storage battery into 2-wire AC power and outputs it, and can switch between interconnection operation with the power system and independent operation. It is provided with a plurality of power storage devices capable of being capable of, a primary winding to which a 2-wire AC voltage is applied, and a transformer having a secondary winding connected to a single-phase 3-wire electric path to which a load is connected. The single-phase three-wire electric current is composed of a first voltage line, a second voltage line, and a neutral line, and the power conditioner of any one of the plurality of power storage devices is self-supporting. A two-wire AC voltage output during operation is applied to the primary winding, and the power conditioner of another power storage device is connected to the first voltage line and the second voltage line during the self-sustaining operation. When each of the plurality of power storage devices performs the self-sustaining operation, any one of the plurality of power storage devices is a master device, and a power storage device other than the master device is a slave device. The power conditioner of the master device performs voltage control for controlling the AC voltage output during the self-sustaining operation to the target voltage, and the slave device performs the first current flowing through the first voltage line and the second voltage line. The power conditioner of the slave device is based on the measurement data of the first current and the second current during the self-sustaining operation. It is characterized in that current control is performed to control the output current to the target current determined by the above.</p><p> The power storage device of the present invention is characterized in that it is used in the above-mentioned power storage system.</p><p> The operation method of the power storage device of the present invention has a storage battery and a power conditioner that converts the DC power of the storage battery into a 2-wire AC power and outputs it, and enables interconnection operation with the power system and independent operation. It is equipped with a plurality of power storage devices that can be switched, a primary winding to which a 2-wire AC voltage is applied, and a transformer having a secondary winding connected to a single-phase 3-wire electric circuit to which a load is connected. The single-phase three-wire type electric circuit is a method of operating a power storage device used in a power storage system composed of a first voltage line, a second voltage line, and a neutral line, and is a method of operating the power storage device of the plurality of power storage devices. The power conditioner of any one of the power storage devices applies a two-wire AC voltage output to the primary winding during the self-sustaining operation, and the power conditioner of the other power storage device is the first during the self-sustaining operation. When the output is connected to the 1 voltage line and the 2nd voltage line and each of the plurality of power storage devices performs the self-sustaining operation, any one of the plurality of power storage devices is the master device. The power storage device other than the master device is a slave device, and the power conditioner of the master device performs voltage control for controlling the AC voltage output during the self-sustaining operation to the target voltage, and the power conditioner of the slave device is It is characterized by performing current control for controlling the output current to a target current determined based on the measurement data of the first current flowing through the first voltage line and the second current flowing through the second voltage line. And.</p>

<p> As described above, in the present invention, a plurality of power storage devices can be operated in parallel to supply single-phase three-wire power, and a simple system configuration can provide single-phase three-wire power capacity. It has the effect of being easily increased.</p>

<figref num="1">It is a block diagram which shows the structure of the power storage system of embodiment.</figref><figref num="2">It is a block diagram which shows the structure of the power storage device of embodiment.</figref><figref num="3">It is a schematic diagram which shows the connection form of a plurality of power storage devices which perform self-sustaining operation of embodiment, and a self-sustaining load.</figref><figref num="4">Each of FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D is a waveform diagram showing current waveforms of each part when independent output control different from that of the present embodiment is performed.</figref><figref num="5">Each of FIG. 5A, FIG. 5B, FIG. 5C, and FIG. 5D is a waveform diagram showing a current waveform of each part when the independent output control of this embodiment is performed.</figref>

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment) The power storage system of this embodiment has the configuration shown in FIG. 1, and is used in each dwelling unit, detached house, factory, office, or other building of an apartment house to which commercial power is supplied from an electric power company. Used. This system mainly includes a plurality of power storage devices 2 and a transformer 5. In addition, this system also has a distribution board 1, switching boards 31, 32, and a controller 4. When distinguishing a plurality of power storage devices 2, each of the plurality of power storage devices 2 is referred to as a power storage device 21, 22, 23, ....

The main line 81 drawn into the building is connected to the distribution board 1, and the commercial power 9 of the electric power company supplies single-phase three-wire 200V / 100V commercial power via the main line 81. The main electric circuit 81 is composed of two voltage lines and one grounded neutral line. The distribution board 1 houses a main power breaker 1a, a branch breaker 1b, and a distributed power breaker 1c. The main electric circuit 81 is connected to each of a plurality of branch breakers 1b and a distributed power supply breaker 1c via a main power supply breaker 1a.

Then, the main electric circuit 81 branches into a plurality of branch electric circuits 82 via each branch breaker 1b. System loads 71 of lighting equipment, air conditioning equipment, home appliances, etc. are connected to each of the branch electric lines 82, and 200V or 100V AC power is supplied to these system loads 71. However, one of the plurality of branch electric lines 82a is connected to the switching board 31. This branch electric circuit 82a supplies single-phase three-wire 200V / 100V AC power.

This power storage system includes a plurality of power storage devices 2, and any one of the power storage devices 2 in the power storage system serves as a master device, and the remaining power storage devices 2 in the system serve as slave devices. In the present embodiment, an operation unit such as a switch for switching to the master device or the slave device is provided in the power storage device 2, and the power storage device 2 is set in the master device or the slave device according to the operation of the operation unit. That is, it is assumed that the same power storage device 2 is used for the master device and the slave device. Alternatively, although different from the present embodiment, a power storage device dedicated to the master device and a power storage device dedicated to the slave device may be used.

Hereinafter, it is assumed that the power storage device 21 is a master device and the power storage devices 22 and 23 are slave devices.

As shown in FIG. 2, each of the plurality of power storage devices 2 (master device 21, slave device 22, 23) has a storage battery 2a, a power conditioner 2b, a communication unit 2c, a control unit 2d, and a data acquisition unit. Equipped with 2e.

The storage battery 2a is composed of a secondary battery such as a lithium ion battery, and is connected to the power conditioner 2b. The power conditioner 2b has an AC / DC conversion function that converts AC power into DC power to charge the storage battery 2a, and a DC / AC conversion function that converts the DC power of the storage battery 2a into AC power and outputs it.

The interconnection connection 2f of the power conditioner 2b receives commercial power from the commercial power supply 9 via the breaker 1c for distributed power supply and the AC electric line 83, and the power conditioner 2b converts the received commercial power into DC power. The storage battery 2a can be charged.

The discharge power of the storage battery 2a is supplied to the power conditioner 2b, and is converted into 2-wire 200V (line voltage 200V) AC power by the power conditioner 2b. This power conditioner 2b operates so as to be able to switch between interconnection operation and independent operation. By detecting the AC voltage input to the interconnection connection 2f, the power conditioner 2b stops the supply of commercial power from the commercial power supply 9 during normal operation when the commercial power supply 9 is supplying commercial power and when the commercial power supply 9 stops supplying commercial power. Determine when there is a power outage.

Specifically, the power conditioner 2b performs interconnection operation when the commercial power supply 9 is energized, and operates independently when the commercial power supply 9 has a power failure. Then, the power conditioner 2b interconnects with the commercial power supply 9 (commercial power system) during the interconnection operation, and transfers the 2-wire 200V AC power generated from the discharge power of the storage battery 2a from the interconnection connection 2f. Output. In addition, the power conditioner 2b outputs 2-wire 200V AC power generated from the discharge power of the storage battery 2a from the self-sustaining connection unit 2g without being connected to the commercial power system during self-sustaining operation.

The AC power output from the interconnection connection 2f is called the interconnection output, and the AC power output from the self-supporting connection 2g is called the self-sustaining output.

The interconnection connection portion 2f is connected to the AC electric circuit 83, and the interconnection output is supplied from the AC electric circuit 83 to the main electric circuit 81 via the distributed power breaker 1c of the distribution board 1. Thus, the interconnection output is supplied from the main circuit 81 to the branch circuit 82 via the branch breaker 1b. The power conditioner 2b has a grid interconnection function that coordinates the interconnection output with the commercial power supplied by the commercial power source 9. Here, the AC electric circuit 83 is a two-wire electric circuit that transmits AC power of a two-wire type 200V, and the two voltage lines of the AC electric circuit 83 are connected to the two voltage lines of the main electric circuit 81.

Further, the self-supporting connection portion 2g of the master device 21 is connected to the 2-wire AC electric circuit 84, and the self-sustaining output of the master device 21 is output to the AC electric circuit 84. The two-wire AC electric line 84 is electrically connected to the three-wire AC electric line 85 via the transformer 5. Transformer 5 is an isolation transformer that converts 2-wire 200V AC power into single-phase 3-wire 200V / 100V AC power. This transformer 5 includes a primary winding 51 and a secondary winding 52, a 2-wire AC electric line 84 is connected to the primary winding 51, and a 3-wire AC electric line 85 is connected to the secondary winding 52. Be connected. Then, the switching board 32 switches the connection state between the three-wire AC electric circuit 85 and the three-wire AC electric circuit 86 to conduction or disconnection. The switching board 31 switches the connection destination of the three-wire self-supporting electric line 87 to either the branch electric line 82a or the AC electric line 86. The self-supporting electric circuit 87 is composed of a first voltage line and a second voltage line, and one grounded neutral wire. The self-sustaining electric circuit 87 is self-supporting for lighting equipment, air conditioning equipment, home appliances, and the like. Load 72 is connected.

Here, the main electric circuit 81 is a three-wire electric circuit that transmits a single-phase three-wire 200V / 100V AC power, and the branch electric circuit 82 transmits a single-phase three-wire 200V / 100V AC power 3 It is a wire type electric circuit, or a two-wire type electric circuit that transmits AC power of two-wire type 200V and two-wire type 100V. However, the branch electric circuit 82a is a three-wire electric circuit that transmits AC power of a single-phase three-wire system 200V / 100V. AC electric lines 83 and 84 are two-wire electric lines that transmit AC power of two-wire type 200V. The AC electric lines 85 and 86 and the self-supporting electric line 87 are three-wire electric lines that transmit AC power of single-phase three-wire 200V / 100V.

In addition, the independent connection part 2g of the slave devices 22 and 23 is connected to the 3-wire AC electric circuit 85, and each independent output of the slave devices 22 and 23 is the AC electric circuit 85, the switching board 32, the AC electric circuit 86, and the switching. It is output to the self-supporting electric circuit 87 via the board 31. Here, the independent outputs of the slave devices 22 and 23 are connected to two voltage lines of the three-wire AC electric circuit 85.

Then, each connection state of the switching boards 31 and 32 is switched and controlled by the controller 4. The controller 4 detects the voltage on the primary side of the main power breaker 1a, for example, during normal times when the commercial power supply 9 is supplying commercial power and during a power failure when the supply of commercial power from the commercial power supply 9 is stopped. Is determined. When the controller 4 determines that it is in the normal state, it switches and controls the switching board 31, connects the self-supporting electric line 87 to the branch electric line 82a, and further controls the switching board 32 to be off. If the controller 4 determines that a power failure has occurred, the switching board 31 is switched and controlled to connect the self-supporting electric circuit 87 to the AC electric circuit 86, and the switching board 32 is turned on after all the power storage devices 2 are activated. It is controlled to conduct the AC electric circuit 85 and the AC electric circuit 86.

Normally, since the independent electric circuit 87 is connected to the branch electric circuit 82a by the switching board 31, the electric circuit from the branch electric circuit 82a to the independent electric circuit 87 is conducted, and the electric power of the main electric circuit 81 (sum of commercial power and interconnection output). Is supplied to the self-sustaining electric circuit 87. Furthermore, in normal times, the main line 81 and the independent connection parts 2g of the slave devices 22 and 23 are cut off, and power is not supplied to the independent connection parts 2g from the outside, so safety should be ensured. Can be done.

Further, in the event of a power failure, the self-supporting electric circuit 87 is connected to the AC electric circuit 86 by the switching board 31, and the AC electric circuit 86 is connected to the AC electric circuit 85 by the switching board 32. Therefore, the electric path from the independent connection portion 2g of the master device 21 and the slave devices 22 and 23 to the independent electric path 87 is conducted, and the independent output of the master device 21 and the slave devices 22 and 23 is supplied to the independent electric path 87.

In this system, the system load 71 connected to the branch electric circuit 82 is a load to which power is supplied only during the normal time when the commercial power source 9 is energized. On the other hand, the self-sustaining load 72 connected to the self-supporting electric line 87 is a load to which power is supplied both in the normal state when the commercial power supply 9 is energized and in the power failure of the commercial power supply 9.

The self-sustaining electric circuit 87 to which the self-sustaining load 72 is electrically connected is composed of two voltage lines and one grounded neutral wire, and the self-sustaining electric circuit 87 has current sensors 61 to 64. It is provided. The current sensors 61 to 64 measure the load current flowing through each voltage line of the self-supporting electric circuit 87. The current sensor 61 measures the load current (first current) of the first voltage line, outputs this measurement data to the slave device 22, and the current sensor 62 measures the load current (second current) of the second voltage line. Then, this measurement data is output to the slave device 22. Further, the current sensor 63 measures the load current (first current) of the first voltage line and outputs this measurement data to the slave device 23, and the current sensor 64 measures the load current (second current) of the second voltage line. Is measured, and this measurement data is output to the slave device 23. Each of the current sensors 61 to 64 generates and outputs measurement data for each sampling period.

Each of the data acquisition units 2e of the slave devices 22 and 23 receives the measurement data transmitted to the own device and delivers the measurement data to the control unit 2d.

Further, the communication unit 2c of the power storage device 2 can perform wired or wireless communication with the communication unit 2c of the other power storage device 2, and the control unit 2d controls the communication of the communication unit 2c.

Hereinafter, the self-sustaining operation of the power storage device 2 in the event of a power failure will be described with reference to FIG. FIG. 3 is a schematic view showing only the connection form between the plurality of power storage devices 2 that perform self-sustaining operation and the self-sustaining load 72.

The AC electric circuit 84 connected to the self-supporting connection portion 2g of the master device 21 is two lines of voltage lines L1 and L2, and the voltage line L1 is connected to one end of the primary winding 51 of the transformer 5 and is connected to the voltage line L2. Is connected to the other end of the primary winding 51 of the transformer 5. The transformer 5 includes a secondary winding 52, one end of the secondary winding 52 is connected to the voltage line L11 of the AC electric circuit 85, and the other end of the secondary winding 52 is the voltage line L12 of the AC electric circuit 85. Is connected to. Further, the neutral point of the secondary winding 52 is connected to the neutral wire L10 of the AC electric circuit 85.

That is, the transformer 5 converts the 2-wire 200V AC power supplied from the AC electric circuit 84 into the single-phase 3-wire 200V / 100V AC power and outputs it to the AC electric circuit 85. In this case, the line voltage between the voltage line L11 and the voltage line L12 is 200V, the line voltage between the voltage line L11 and the neutral line L10 is 100V, and the line voltage between the voltage line L12 and the neutral line L10 is It becomes 100V.

Further, the independent connection portions 2g of the slave devices 22 and 23 are connected to the voltage lines L11 and L12 of the AC electric circuit 85.

Then, the voltage line L11, the voltage line L12, and the neutral line L10 of the AC electric circuit 85 pass through the switching board 32, the AC electric circuit 86, and the switching board 31, respectively, and the first voltage line L31 and the second voltage of the self-supporting electric circuit 87. Electrically connect to each of wire L32 and neutral wire L30. That is, the line voltage between the first voltage line L31 and the second voltage line L32 is 200V, the line voltage between the first voltage line L31 and the neutral line L30 is 100V, and the second voltage line L32-neutral line is 100V. The line voltage between L30 is 100V.

That is, the independent outputs of the power conditioners 2b of the master device 21, the slave devices 22, and 23 are connected in parallel to the first voltage line L31 and the second voltage line L32 of the independent electric circuit 87 during the independent operation. .. In other words, the master device 21, the slave devices 22, and 23 are operating in parallel.

The control units 2d of the master device 21, the slave devices 22, and 23 are connected to the other power storage device 2 via the communication unit 2c during both the interconnection operation and the independent operation, for example, a survival signal, etc. Send and receive signals on a regular basis. The control unit 2d can recognize the number of power storage devices 2 in the system based on the signal received from the other power storage device 2, and holds the data of the number of power storage devices 2 in the system.

Then, when each of the master device 21, the slave devices 22, and 23 starts the self-sustaining operation, in the master device 21, the control unit 2d instructs the power conditioner 2b to perform the constant voltage operation. Specifically, the control unit 2d of the master device 21 notifies the power conditioner 2b of the target voltage. The power conditioner 2b instructed to operate at a constant voltage controls the voltage so that the voltage of the self-sustaining output matches the target voltage. The target voltage is set to the nominal voltage of commercial power, which is set to 200V here.

In each of the slave devices 22 and 23 that have started the self-sustaining operation, the control unit 2d instructs the power conditioner 2b to perform a constant current operation. Specifically, each control unit 2d of the slave devices 22 and 23 notifies the power conditioner 2b of the target current. The power conditioner 2b instructed to operate at a constant current controls the current so that the self-sustaining output current matches the target current. In the power conditioner 2b instructed to operate at a constant current, the voltage of the self-supporting output is close to the nominal voltage of 200V for commercial power.

When the master device 21 and the slave devices 22 and 23 communicate with each other, the master device 21 starts the self-sustaining operation and performs voltage control, and then each of the slave devices 22 and 23 starts the self-sustaining operation. And control the current. Alternatively, the master device 21, the slave devices 22, and 23 can communicate with each other to synchronize the self-sustaining output.

Specifically, the control units 2d of the slave devices 22 and 23 consume each of the independent loads 72 from the measurement data of the load current I11 of the first voltage line L31 and the load current I12 of the second voltage line L32. The total power consumption (total power consumption) can be derived. In this case, the load current I11 of the first voltage line L31 corresponds to the load current of the 100V system composed of the first voltage line L31 and the neutral line L30. The load current I12 of the second voltage line L32 corresponds to the load current of the 100V system composed of the second voltage line L32 and the neutral line L30. Therefore, the total power consumption = {load current I11 + load current I12} × 100. Each control unit 2d of the slave devices 22 and 23 uses the value obtained by dividing the total power consumption by the self-sustained output voltage of 200 V as the converted current. The converted current is periodically updated every sampling cycle of the current sensors 61 to 64. The load current I11 and the load current I12 are positive in the direction of the arrow in FIG.

This converted current is a current obtained by converting the measurement data of the load current I11 and the load current I12 into a current corresponding to the line voltage 200V between the first voltage line L31 and the second voltage line L32. That is, the converted current is a current capable of supplying the power (total power consumption) required by the independent load 72 in a 2-wire electric circuit (200V system) having a line voltage of 200V. The control unit 2d of each of the slave devices 22 and 23 sets the target current as the value obtained by dividing this converted current by the number of power storage devices 2 (3 in this case).

Alternatively, each control unit 2d of the slave devices 22 and 23 may derive the converted current according to the equation "converted current = {load current I11 + load current I12} / 2".

That is, each of the slave devices 22 and 23 sets the target current so that each of the power storage devices 2 in the system equally divides and bears the total load power. Therefore, the current values and waveforms of the independent outputs of the slave devices 22 and 23 are the same as each other, and the independent outputs of the master device 21 that controls the voltage are also the same as the independent outputs of the slave devices 22 and 23 as a result. It becomes the current value and the waveform.

4A, 4B, 4C, and 4D show the current waveforms of each part when the master device 21 performs voltage control and the slave devices 22 and 23 each perform current control different from that of the present embodiment. The current control performed by each of the slave devices 22 and 23 is different from the current control of the present embodiment in that the current waveform of the independent output is a sine wave.

FIG. 4A shows the waveform of the converted current I0, FIG. 4B shows the waveform of the independent output current (independent current) I1 of the master device 21, and FIG. 4C shows the waveform of the independent current I2 of the slave device 22. FIG. 4D shows the waveform of the self-supporting current I3 of the slave device 23. The converted current I0 is the current required when the total load power is covered by the 200V system, and is the sum of the independent currents I1, I2, and I3 of the master device 21, the slave devices 22, and 23.

In this case, the self-sustaining load 72 includes a capacitive load (for example, a capacitor input type load), and the converted current I0 rapidly increases in the vicinity of the voltage peak, and the waveform is distorted. Then, when each of the slave devices 22 and 23 performs current control in which the current waveform of the self-sustaining output is a sine wave, the master device 21 bears most of this waveform distortion component, and the master device 21, the slave device 22, Output bias can occur between 23. For example, as shown in FIG. 4B, when the independent current I1 of the master device 21 bears most of the waveform distortion components of the converted current I0, the independent current I1 is distorted and becomes an overcurrent state (region X1 in FIG. 4B), and the master The operation of the device 21 becomes unstable. In addition, the self-sustaining current I1 of the master device 21 may be in a charging mode having the opposite polarity to the converted current I0 (region X2 in FIG. 4B), which may affect the safety of the system.

Therefore, in the present embodiment, as described above, the master device 21 performs voltage control, and each of the slave devices 22 and 23 performs current control in which the converted current I0 is evenly divided and borne.

5A, 5B, 5C, and 5D show each part when the master device 21 performs voltage control and the slave devices 22 and 23 each perform current control in which the converted current I0 is evenly divided and borne. The current waveform is shown. FIG. 5A shows the waveform of the converted current I0, FIG. 5B shows the waveform of the independent current I1 of the master device 21, FIG. 5C shows the waveform of the independent current I2 of the slave device 22, and FIG. 5D shows the waveform of the independent current I2 of the slave device. The waveform of the independent current I3 of 23 is shown.

In this case as well, the self-supporting load 72 includes a capacitive load, and the converted current I0 rapidly increases in the vicinity of the voltage peak, and the waveform is distorted. However, the master device 21 performs the above-mentioned voltage control, and each of the slave devices 22 and 23 performs the current control in which the above-mentioned conversion current I0 is evenly divided and borne, so that the master device 21 and the slave devices 22, 23 The current values and waveforms of the independent currents I1, I2, and I3 are almost the same, and the independent currents I1, I2, and I3 are almost unbiased. That is, each of the slave devices 22 and 23 sets the target current so that each of the power storage devices 2 in the system bears the converted current I0 evenly divided.

Therefore, the waveform distortion component of the converted current I0 is also borne by the independent currents I1, I2, and I3 almost evenly, and the occurrence of the charging mode having the opposite polarity to the converted current I0 is suppressed. That is, in the power storage system of the present embodiment, when a plurality of self-operating power storage devices 2 are operating in parallel, it is possible to suppress a bias in the degree of burden on each of the plurality of power storage devices 2.

Further, even in the normal state, the master device 21 performs the interconnection operation by the voltage control described above, and each of the slave devices 22 and 23 performs the interconnection operation by the current control described above. Alternatively, in the normal state, not only the slave devices 22 and 23 but also the master device 21 may perform the interconnection operation by the above-mentioned current control. In this case, the master device 21 can also acquire the measurement data of the load current I11 of the first voltage line L31 and the load current I12 of the second voltage line L32.

The power storage device 2 connected to the primary side of the transformer 5 is not limited to the master device 21, but may be a slave device 22 or 23. At this time, the master device 21 is connected to the secondary side of the transformer 5. In this case as well, the same effect as described above can be obtained by performing the voltage control by the master device 21 and the current control by the slave devices 22 and 23 in the same manner as described above.

The above-mentioned power storage system includes a plurality of power storage devices 2 and a transformer 5. Each of the plurality of power storage devices 2 has a power conditioner 2b that converts the DC power of the storage battery 2a and the storage battery 2a into 2-wire AC power and outputs the power conditioner 2b. Can be switched. The transformer 5 has a primary winding 51 and a secondary winding 52. A two-wire AC voltage is applied to the primary winding 51. The secondary winding 52 is connected to a single-phase three-wire self-supporting electric circuit 87 (electric circuit) to which an independent load 72 (load) is connected. The self-supporting electric circuit 87 is composed of a first voltage line L31, a second voltage line L32, and a neutral line L30.

Then, the power conditioner 2b of any one of the plurality of power storage devices 2 applies a two-wire AC voltage output during self-sustaining operation to the primary winding 51. The power conditioner 2b of the other power storage device 2 has its output connected to the first voltage line L31 and the second voltage line L32 during independent operation. When each of the plurality of power storage devices 2 operates independently, one of the plurality of power storage devices 2 is the master device, and the power storage device 2 other than the master device is the slave device. The power conditioner 2b of the master device performs voltage control that controls the AC voltage output during independent operation to the target voltage. The slave device further includes a data acquisition unit 2e. The data acquisition unit 2e acquires measurement data of the load current I11 (first current) flowing through the first voltage line L31 and the load current I12 (second current) flowing through the second voltage line L32. The power conditioner 2b of the slave device performs current control for controlling the output current to a target current determined based on the measurement data of the load current I11 and the load current I12 during self-sustaining operation.

That is, the power storage system of the present embodiment includes a transformer 5 that converts 2-wire power into single-phase 3-wire power, and the self-sustaining output of one power storage device 2 is on the primary side of the transformer 5. It is input and converted to single-phase three-wire power by transformer 5. Further, the independent output of the other power storage device 2 is connected to the secondary side of the transformer 5 and directly supplies the independent output to the single-phase three-wire electric circuit.

On the other hand, it is also conceivable to connect each independent output of all the power storage devices 2 to the primary side of one transformer and convert all the independent outputs of all the power storage devices 2 into single-phase three-wire power by the transformer. .. However, in this case, the capacity of the transformer needs to correspond to the total of all the self-sustaining outputs of all the power storage devices 2, which causes an increase in the size and cost of the transformer.

In the present embodiment, only the independent output of one power storage device 2 is connected to the primary side of the transformer 5, and the self-sustaining output of the other power storage device 2 is connected to the secondary side of the transformer 5. Therefore, the transformer 5 only needs to have a capacity corresponding to the self-sustaining output of one power storage device 2, and a simple system configuration can be realized by reducing the size and cost of the transformer 5. Furthermore, since a plurality of power storage devices 2 are operated in parallel with this simple system configuration, it is possible to increase the capacity of single-phase three-wire power.

That is, the power storage system can supply a single-phase three-wire system power by operating a plurality of power storage devices 2 in parallel, and further, a simple system configuration can easily increase the power capacity of the single-phase three-wire system. be able to.

Further, the power conditioner 2b of the master device 21 preferably applies a two-wire AC voltage output during independent operation to the primary winding 51. Further, it is preferable that the power conditioners 2b of the slave devices 22 and 23 have their outputs connected to the first voltage line L31 and the second voltage line L32 during self-sustaining operation.

In this case, the self-sustaining output of the master device 21 is input to the primary side of the transformer 5 and converted into single-phase three-wire power by the transformer 5. Further, the independent outputs of the slave devices 22 and 23 are connected to the secondary side of the transformer 5 to directly supply the independent outputs to the single-phase three-wire electric circuit. That is, only the independent output of the master device 21 is connected to the primary side of the transformer 5, and the independent outputs of the slave devices 22 and 23 are connected to the secondary side of the transformer 5. Therefore, the transformer 5 only needs to have a capacity corresponding to the self-sustaining output of the master device 21, and a simple system configuration can be realized by reducing the size and cost of the transformer 5. Furthermore, since a plurality of power storage devices 2 are operated in parallel with this simple system configuration, it is possible to increase the capacity of single-phase three-wire power.

Further, the slave devices 22 and 23 further include a control unit 2d. The control unit 2d converts the measurement data of the load current I11 and the load current I12 into a conversion current which is a current corresponding to the line voltage 200V between the first voltage line L31 and the second voltage line L32, and converts the conversion current into a conversion current. It is preferable to set the divided value as the target current.

Therefore, in the power storage system of the present embodiment, the target currents of the slave devices 22 and 23 can be appropriately set based on the converted current.

Further, the control unit 2d preferably sets the value obtained by dividing the converted current by the number of the plurality of power storage devices 2 as the target current.

That is, the target current is evenly determined based on the converted current and the number of power storage devices 2, and the slave devices 22 and 23 perform current control for controlling the output current to the target current. Therefore, the current values and waveforms of the independent outputs of the plurality of power storage devices 2 are substantially the same, and the independent outputs of the plurality of power storage devices 2 are in a state of being substantially unbiased.

Further, each control unit 2d of the slave devices 22 and 23 can communicate with the master device 21 via the communication unit 2c, and periodically transmits the remaining capacity data to the master device 21. The remaining capacity data represents the charge level of the storage battery 2a, and the control unit 2d of the master device 21 can know the current remaining capacity (charge level) of the slave devices 22 and 23. Therefore, the control unit 2d of the master device 21 derives a weighting coefficient for weighting each target current of the slave devices 22 and 23 based on the remaining capacitance data of the own device and the slave devices 22 and 23.

Specifically, the control unit 2d of the master device 21 determines the ratio of the remaining capacity of the slave devices 22 and 23 to the remaining capacity of the own device based on the remaining capacity data of the own device and the slave devices 22 and 23 [slave device]. The remaining capacity of the master device / the remaining capacity of the master device] is obtained as the weighting coefficient α. That is, the weighting coefficient α2 of the slave device 22 is [remaining capacity of the slave device 22 / remaining capacity of the master device 21]. The weighting coefficient α3 of the slave device 23 is [remaining capacity of the slave device 23 / remaining capacity of the master device 21]. Then, the control unit 2d of the master device 21 transmits the data of the weighting coefficient α2 to the slave device 22, and transmits the data of the weighting coefficient α3 to the slave device 23.

The control unit 2d of the slave device 22 sets the target current as the result of multiplying the value obtained by dividing the converted current by the number of power storage devices 2 by the weighting coefficient α2. Further, the control unit 2d of the slave device 23 sets the target current as the result of multiplying the value obtained by dividing the converted current by the number of power storage devices 2 by the weighting coefficient α3.

That is, each of the plurality of power storage devices 2 further includes a communication unit 2c capable of communicating with another power storage device 2. The slave devices 22 and 23 transmit the remaining capacity data, which is the data related to the remaining capacity of the storage battery 2a of the own device, to the master device 21. Based on the remaining capacity data of the slave devices 22 and 23 and the remaining capacity data of the own device, the master device 21 sets a coefficient α for each power storage device 2, which becomes a higher value as the remaining capacity increases, and the slave device 22 The data of the coefficient α corresponding to each of 23 and 23 is transmitted. The slave devices 22 and 23 convert the measurement data of the load current I11 and the load current I12 into a conversion current which is a current corresponding to the line voltage 200V between the first voltage line L31 and the second voltage line L32. Is further equipped. Then, the control unit 2d of the slave devices 22 and 23 sets the value obtained by multiplying the value obtained by dividing the converted current by the number of the plurality of power storage devices 2 by the coefficient α as the target current.

That is, the self-sustaining current supplied from the power storage device 2 having a large remaining capacity increases, and the self-sustaining current supplied from the power storage device 2 having a small remaining capacity decreases. Therefore, the power storage system can suppress the bias of the AC power output by each of the plurality of power storage devices 2, and the remaining capacity of the storage battery 2a of each power storage device 2 is set as the current burden according to the remaining capacity of each power storage device 2. Equalization can be achieved.

Further, the above-mentioned power storage device 2 is characterized in that it is used in the power storage system of the present embodiment. Therefore, by using the above-mentioned power storage device 2 in the power storage system, it is possible to operate a plurality of power storage devices 2 in parallel to supply single-phase three-wire power, and further, with a simple system configuration, the single-phase 3 The linear power capacity can be easily increased.

Further, the above-mentioned operation method of the power storage device is a method of operating the power storage device used in the power storage system including the plurality of power storage devices 2 and the transformer 5. The power storage device 2 has a power conditioner 2b that converts the DC power of the storage battery 2a and the storage battery 2a into 2-wire AC power and outputs it, and can switch between interconnection operation with the power system and independent operation. it can. The transformer 5 has a primary winding 51 and a secondary winding 52. A two-wire AC voltage is applied to the primary winding 51. The secondary winding 52 is connected to a single-phase three-wire self-supporting electric circuit 87 (electric circuit) to which an independent load 72 (load) is connected. The self-supporting electric circuit 87 is composed of a first voltage line L31, a second voltage line L32, and a neutral line L30.

Then, the power conditioner 2b of any one of the plurality of power storage devices 2 applies a two-wire AC voltage output during self-sustaining operation to the primary winding 51. The power conditioner 2b of the other power storage device 2 has its output connected to the first voltage line L31 and the second voltage line L32 during independent operation. When each of the plurality of power storage devices 2 operates independently, one of the plurality of power storage devices 2 is the master device, and the power storage device 2 other than the master device is the slave device. The power conditioner 2b of the master device performs voltage control that controls the AC voltage output during independent operation to the target voltage. The power conditioner 2b of the slave device is based on the measurement data of the load current I11 (first current) flowing through the first voltage line L31 and the load current I12 (second current) flowing through the second voltage line L32. Current control is performed to control the output current to the determined target current.

Therefore, in the operation method of this power storage device, a plurality of power storage devices 2 can be operated in parallel to supply single-phase three-wire power, and a simple system configuration can be used to supply single-phase three-wire power capacity. Can be easily increased.

Further, the power storage device 2 is equipped with a computer, and the function of the control unit 2d of the power storage device 2 described above is realized by executing the program by the computer. A computer is mainly composed of a device having a processor for executing a program, a device for an interface for exchanging data between other devices, and a device for storing data. Be prepared. The device provided with the processor may be either a CPU (Central Processing Unit) or MPU (Micro Processing Unit), which is separate from the semiconductor memory, or a microcomputer having the semiconductor memory integrally. As the storage device, a storage device having a short access time such as a semiconductor memory and a large-capacity storage device such as a hard disk device are used in combination.

Programs are provided in a form in which a computer-readable ROM (Read Only Memory), a form in which the program is stored in advance in a recording medium such as an optical disk, a form in which the program is supplied to the recording medium via a wide area communication network including the Internet, etc. There is.

The above-described embodiment is an example of the present invention. Therefore, the present invention is not limited to the above-described embodiment, and even if it is not the embodiment, it varies depending on the design and the like as long as it does not deviate from the technical idea of the present invention. Of course, it is possible to change.

1 Distribution board 2 Power storage device 21 Master device 22, 23 Slave device 2a Storage battery 2b Power conditioner 2c Communication unit 2d Control unit 2e Data acquisition unit 2f Interconnection connection unit 2g Independent connection unit 31,32 Switching board 4 Controller 5 Transformer 51 Primary winding 52 Secondary winding 61 ~ 64 Current sensor 71 System load 72 Independent load 81 Main line 82 Branch line 82a Branch line 83 ~ 86 AC line 87 Independent line