Distributed power system

Abstract

To provide a distributed power supply system capable of supplying power to three-phase and single-phase loads during stand-alone operation.SOLUTION: A distributed power supply system is connected to a commercial power system and includes a distributed power supply capable of stand-alone operation. The distributed power supply system includes a power conversion device for converting power output from the distributed power supply to three-phase power to supply power to a three-phase load and a transformer provided between the power conversion device and a single-phase load. A primary side of the transformer is connected between three-phase power lines for supplying power on any two phases of three-phase power lines for supplying three-phase power from the power conversion device to the three-phase load. A secondary side of the transformer is connected to a single-phase power line for supplying single-phase power to the single-phase load.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a distributed power source system including a power conversion device that is connected to a commercial power system and can supply power from a distributed power source to a three-phase load during independent operation.

Background Art

[0002] Conventionally, a distributed power source system has been proposed in which a distributed power source such as a storage battery or a solar cell is installed and supplies power to a three-phase load in a three-phase three-wire system during connection to a commercial power system and during independent operation. In addition, for customers who desire power supply to a single-phase load during independent operation, a distributed power source system that supplies three-phase three-wire AC power during connection operation and supplies single-phase three-wire or single-phase two-wire AC power during independent operation has been proposed (see, for example, Patent Document 1).

[0003] However, in such a distributed power source system, there has been a problem that power can be supplied only to a three-phase load or a single-phase load during independent operation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a distributed power source system capable of supplying power to a three-phase load and a single-phase load during independent operation.

Means for Solving the Problems

[0006] The present invention for solving the above problems is A distributed power generation system that is connected to a commercial power system and includes a distributed power source capable of independent operation, During independent operation, a power conversion device that converts the power output from the distributed power source into three-phase power and supplies it to a three-phase load, A transformer provided between the power conversion device and a single-phase load, Comprising: During independent operation, the primary side of the transformer is connected between any two of the three-phase power lines that supply the three-phase power from the power conversion device to the three-phase load, and a single-phase power line that supplies single-phase power to the single-phase load is connected to the secondary side of the transformer.

[0007] According to this, in a distributed power generation system including a power conversion device that converts the power output from a distributed power source into three-phase power and supplies it to a three-phase load during independent operation, during independent operation, single-phase power can also be supplied to a single-phase load via a transformer connected to the three-phase power line. As the distributed power source, various power sources such as storage batteries, solar cells, and fuel cells can be applied.

[0008] Also, in the present invention, The power conversion device During the interconnected operation with the commercial power system, includes a plurality of power conversion devices that are connected in parallel and output single-phase power to the same single-phase load, During independent operation, the connection to the single-phase load may be cut off, and the three-phase power combined from the outputs with different phases of the plurality of power conversion devices may be supplied to the three-phase load.

[0009] In this way, in a distributed power generation system including a plurality of power conversion devices that output single-phase power to a single-phase load during system interconnection, three-phase power can be supplied to a three-phase load during independent operation.

[0010] Also, in the present invention, The three-phase power lines connected to the primary side may each be connected to different power conversion devices among the plurality of power conversion devices.

[0011] In this way, during independent operation, the power supplied to the single-phase load via the transformer is supplied from different power conversion devices among the plurality of power conversion devices. Therefore, not only can power be evenly supplied to the three-phase load from the plurality of power conversion devices, but also power can be evenly supplied to the single-phase load from different power conversion devices. Accordingly, the load does not become unbalanced between the power conversion devices.

[0012] Also, in the present invention, The three-phase power lines connected to the primary side may all be connected to any one of the power conversion devices among the plurality of power conversion devices.

[0013] In this way, in a distributed power supply system including a plurality of power conversion devices that convert the power output from the distributed power supply into three-phase power and supply it to a three-phase load, any of the three-phase power lines that supply two-phase power connected to the primary side of the transformer is connected to any one of the plurality of power conversion devices. Therefore, during independent operation, single-phase power can be supplied to the single-phase load via the transformer from one of the plurality of power conversion devices that supply three-phase power to the three-phase load.

[0014] Also, in the present invention, The distributed power supply is a storage battery, It has an AC power supply device that outputs single-phase AC power, The power conversion device to which the three-phase power line connected to the primary side is connected can charge and discharge the storage battery, The output terminal of the AC power supply device may be connected in parallel to the transformer on the three-phase power line connected to the primary side.

[0015] Among a plurality of power conversion devices, since power is supplied from the power conversion device to which the three-phase power line connected to the primary side is connected to a single-phase load, a storage battery that outputs power to the power conversion device that supplies power to the single-phase load via a transformer has a larger discharge power than a storage battery that outputs power to a power conversion device that supplies power only to a three-phase load, and the capacity of the storage battery decreases quickly. When the capacity of any of the storage batteries that supply power to the three-phase load decreases until it becomes impossible to discharge, even if there is a margin in the capacity of the other storage batteries, it becomes impossible to supply power to the three-phase load. Therefore, the load imbalance among the plurality of storage batteries is not preferable. At this time, an output terminal of an AC power supply device that outputs single-phase AC power is connected in parallel to a transformer to the three-phase power line connected to the primary side, and the storage battery is charged from the AC power supply device through the power conversion device to which this three-phase power line is connected. As a result, it is possible to supplement the power corresponding to the large discharge power, and thus the load imbalance can be eliminated. Here, the AC power supply device can be configured to include various distributed power sources that output DC power, such as solar cells, fuel cells, and storage batteries, and a power conversion device that converts DC power into single-phase AC power.

[0016] Also, in the present invention, the distributed power source is a storage battery, has a DC power supply device that outputs DC power, the power conversion device that supplies power to the primary side via the three-phase power line includes an inverter that converts DC power into AC power, a bidirectional converter that is provided between the inverter and the storage battery and can charge and discharge the storage battery, and a DC circuit that connects the inverter and the bidirectional converter. The output terminal of the DC power supply device may be connected in parallel to the inverter to the DC circuit.

[0017] Among a plurality of power conversion devices, since power is supplied from a power conversion device to which a three-phase power line connected to the primary side is connected to a single-phase load, a storage battery that outputs power to a power conversion device that supplies power to the single-phase load via a transformer has a larger discharge power than a storage battery that outputs power to a power conversion device that supplies power only to a three-phase load, and the capacity of the storage battery decreases quickly. When the capacity of any of the storage batteries that supply power to the three-phase load decreases until discharging becomes impossible, even if there is a margin in the capacity of the other storage batteries, power cannot be supplied to the three-phase load. Therefore, load imbalance among the plurality of storage batteries is not preferable. At this time, the output terminal of a DC power supply device that outputs DC power is connected in parallel to an inverter in a DC circuit that connects the inverter and the bidirectional converter of a power conversion device to which the three-phase power line connected to the primary side is connected. By charging the storage battery from the DC power supply device through the bidirectional converter connected to this DC circuit, it is possible to supplement the power corresponding to the large discharge power, so that the load imbalance can be eliminated. Here, the DC power supply device can be configured to include various distributed power sources that output DC power, such as solar cells, fuel cells, and storage batteries, and a converter that converts the DC voltage output from this distributed power source into an appropriate DC voltage.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a distributed power source system that can supply power to a three-phase load and a single-phase load during independent operation.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0020] 〔Application Example〕 Hereinafter, application examples of the present invention will be described with reference to the drawings.

[0021] FIG. 1 is a diagram showing a schematic configuration of a distributed power system 1 according to an application example of the present invention. In the distributed power system 1, two single-phase first power conditioners 20a and second power conditioners 20b connected to two storage batteries 11a and 11b respectively are provided. During parallel operation, single-phase three-wire AC power is supplied from the commercial power system 1a to single-phase consumer loads (single-phase loads) 2 and 3 through power lines 4a, 4b, and 4c. The power from the single-phase first inverter 10a of the first power conditioner 20a and the single-phase second inverter 10b of the second power conditioner 20b is supplied to the single-phase loads 2 and 3. Also, three-phase three-wire AC power is supplied from the commercial power system 1b to the three-phase load 9. On the other hand, during stand-alone operation, the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase load 9. By providing a phase difference of 120 degrees between the output voltages of the first inverter 10a and the second inverter 10b by a synchronization signal transmitted from the first inverter 10a to the second inverter 10b, a three-phase voltage is generated and three-phase three-wire power is supplied.

[0022] During independent operation, in addition to this, single-phase three-wire power is also supplied from the second inverter 10b to the single-phase loads 2 and 3. Here, between the relay 7c and the relay SW8c, a power line 104c branches off from the power line 103c connected to the output terminal 101c of the second inverter 10b. Also, between the relay 7d and the relay SW8b, a power line 104d branches off from the power line 103d connected to the output terminal 101d of the second inverter 10b. These power lines 104d and 104c are connected to the primary side of the transformer Tr. To the secondary side of the transformer Tr, three lines of the power line 105a and the power line 105c, and the power line 105b for drawing out the neutral point thereof are connected. Thereby, the 200V voltage output between the power lines 104c and 104d from the output terminals 101c and 101d of the second inverter 10b is transformed by the transformer Tr, and 100V AC voltages are output between the power lines 105a and 105b and between the power lines 105b and 105c, and a 200V AC voltage is output between the power lines 105a and 105c.

[0023] In this way, during independent operation, three-phase three-wire power can be supplied to the three-phase load 9 through the power lines 103a, 103b, 103d, and 103c, and at the same time, single-phase three-wire power can be supplied to the single-phase loads 2 and 3 through the power lines 105a, 105b, and 105c.

[0024] 〔Embodiment 1〕 Hereinafter, the distributed power supply system 1 according to Embodiment 1 of the present invention will be described in more detail with reference to the drawings.

[0025] FIG. 1 is a diagram showing a schematic configuration of the distributed power supply system 1 according to Embodiment 1 of the present invention. In the distributed power system 1, two single-phase first power conditioners 20a and second power conditioners 20b respectively connected to two storage batteries 11a and 11b are provided. The first power conditioner 20a and the second power conditioner 20b each have a single-phase first inverter 10a and a second inverter 10b. In this example, during the parallel operation, the relays 5a, 5b and the relays 5c, 5d are connected, and the relay switches 6a, 6b, 6c are connected to the grid side, so that the power generated by the single-phase voltages of the first inverter 10a and the second inverter 10b is supplied to the single-phase loads 2 and 3. That is, during the parallel operation, the first power conditioner 20a and the second power conditioner 20b as a plurality of power conversion devices are connected in parallel to supply single-phase power to the same single-phase loads 2 and 3. On the other hand, during the independent operation, the relays 5a, 5b, 5c, 5d on the side of the first inverter 10a and the second inverter 10b are disconnected, and the relays 7a, 7b, 7c, 7d are connected. Then, by connecting the relay switches 8a, 8b, 8c to the first power conditioner 20a and the second power conditioner 20b side, the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase load 9. Further, by connecting the relay switches 6a, 6b, 6c to the second inverter 10b side, the output of the second inverter 10b is also supplied to the single-phase loads 2 and 3. Here, the storage batteries 11a and 11b correspond to the distributed power sources of the present invention.

[0026] Here, single-phase three-wire AC power (single-phase power) is supplied from the commercial power system 1a to the single-phase loads 2 and 3 through the power lines 4a, 4b, 4c. That is, a voltage of 100V is applied between the power lines 4a and 4b, a voltage of 100V is applied between the power lines 4b and 4c, and a voltage of 200V is applied between the power lines 4a and 4c. The power lines 4a, 4b, 4c are respectively connected to the single-phase loads via the relay switches 6a, 6b, 6c It is connected to 2 and 3. During grid connection, the output terminals 101a and 101b of the first inverter 10a are connected to the power lines 4a, 4b, and 4c via the relays 5a and 5b. At this time, the power lines 102a and 102b connected to the output terminals 101a and 101b of the first inverter 10a are respectively connected to the power lines 4a and 4c, and the midpoint of the two capacitors connected in series between the power lines 102a and 102b respectively connected to the output terminals 101a and 101b is connected to the power line 4b. Also, during grid connection, the output terminals 101c and 101d of the second inverter 10b are connected to the power lines 4a, 4b, and 4c via the relays 5c and 5d. And the power lines 102c and 102d connected to the output terminals 101c and 101d of the second inverter 10b are respectively connected to the power lines 4a and 4c, and the midpoint of the two capacitors connected in series between the power lines 102c and 102d respectively connected to the output terminals 101c and 101d is connected to the power line 4b. Also, during grid-connected operation, three-phase three-wire AC power is supplied from the commercial power grid 1b to the three-phase load 9.

[0027] During independent operation, the relays 5a, 5b, 5c, and 5d on the side of the first inverter 10a and the second inverter 10b are disconnected, and the relays SW6a, 6b, and 6c are switched from the grid side to the transformer Tr side. As a result, the connection between the first inverter 10a and the second inverter 10b and the single-phase loads 2 and 3 via the power lines 102a, 102b, 102c, 102d and the power lines 4a, 4b, 4c during grid-connected operation is interrupted. Also, during autonomous driving, a synchronous signal transmitted from the first inverter 10a to the second inverter 10b is used to provide a 120-degree phase difference between the output voltages of the first inverter 10a and the second inverter 10b, thereby generating a three-phase voltage and supplying three-phase three-wire power. Here, the power line 103a connected to the output terminal 101a of the first inverter 10a is connected to the relay SW8a on the three-phase load 9 side via the relay 7a. The power line 103b connected to the output terminal 101b of the first inverter 10a is connected to the relay SW8b on the three-phase load 9 side via the relay 7b. Also, a power line connected to the output terminal 101d of the second inverter 10b is connected to the power line 103b connected to this relay SW8b via the relay 7d. And the power line 103c connected to the output terminal 101c of the second inverter 10b is connected to the relay SW8c on the three-phase load 9 side via the relay 7c. At this time, the output terminal 101b of the first inverter 10a and the output terminal 101d of the second inverter 10b are at the same potential, and a 120-degree phase difference is provided between the output voltage between the output terminal 101a of the first inverter 10a and the output terminals 101b of the first inverter 10a and 101d of the second inverter 10b, and the output voltage between the output terminals 101b of the first inverter 10a and 101d of the second inverter 10b and the output terminal 101c of the second inverter 10b, thereby supplying three-phase three-wire power to the three-phase load 9 through the power lines 103a, 103b and 103d, and the power line 103c. That is, three-phase power combining the outputs with different phases of the first power conditioner 20a and the second power conditioner 20b is supplied to the three-phase load 9. Here, the power lines 103a, 103b and 103d, and the power line 103c correspond to the three-phase power lines of the present invention.

[0028] As described above, during independent operation, three-phase power is supplied from the first inverter 10a and the second inverter 10b to the three-phase load 9. During independent operation, in addition to this, single-phase three-wire power is also supplied from the second inverter 10b to the single-phase loads 2 and 3. Here, between the relay 7c and the relay SW8c, a power line 104c branches off from the power line 103c connected to the output terminal 101c of the second inverter 10b. Also, between the relay 7d and the relay SW8b, a power line 104d branches off from the power line 103d connected to the output terminal 101d of the second inverter 10b. The primary side of the transformer Tr is connected between this power line 104d and the power line 104c. Here, among the power lines 103a to 103d corresponding to the three-phase power lines of the present invention, the power lines 103c and 103d correspond to the three-phase power lines that supply two-phase power of the present invention, and between the power line 103c and the power line 103d, the power line 104c and the power line 104 d are connected to the primary side of the transformer Tr via them.

[0029] Three wires, namely the power line 105a, the power line 105c, and the power line 105b that draws out their neutral point, are connected to the secondary side of the transformer Tr. The power lines 105a, 105b, and 105c are respectively connected to the relays SW6a, 6b, and 6c on the single-phase load 2, 3 side. As a result, the 200V voltage output between the power lines 104c and 104d from the output terminals 101c and 101d of the second inverter 10b is transformed by the transformer Tr, and an AC voltage of 100V is output between the power lines 105a and 105b and between the power lines 105b and 105c, and 200V is output between the power lines 105a and 105c. Here, the power lines 105a, 105b, and 105c correspond to the single-phase power lines of the present invention.

[0030] During autonomous operation, relays 5a, 5b of the first inverter 10a and 5c, 5d of the second inverter 10b are disconnected, and relays 7a, 7b of the first inverter 10a and 7c, 7d of the second inverter 10b are connected. Then, relays SW6a, 6b, 6c and relays SW8a, 8b, 8c are switched from the system side to the first inverter 10a and the second inverter 10b side. Thereby, three-phase three-wire power can be supplied to the three-phase load 9 through the power lines 103a, 103b, 103d, and 103c, and at the same time, single-phase three-wire power can be supplied to the single-phase loads 2 and 3 through the power lines 105a, 105b, and 105c.

[0031] 〔Embodiment 2〕 Hereinafter, the distributed power supply system 21 according to Embodiment 2 of the present invention will be described in more detail with reference to the drawings.

[0032] FIG. 2 is a diagram showing a schematic configuration of the distributed power supply system 21 according to Embodiment 2 of the present invention. For the configuration common to Embodiment 1, the detailed description will be omitted by using the same reference numerals. In the distributed power supply system 21 according to Embodiment 2, in addition to the two single-phase first power conditioners 20a and second power conditioners 20b respectively connected to the two storage batteries 11a and 11b, a single-phase PV power conditioner 20c connected to the solar cell (PV) panel 11c is provided. The PV power conditioner 20c has a PV inverter 10c.

[0033] The output of the PV inverter 10c is interrupted by relays 13a and 13b. The output terminals 101e and 101f of the PV inverter 10c are connected to relay SWs 14a, 14b, and 14c via relays 13a and 13b. Relay SW 14b is connected to the midpoint of two capacitors connected in series between output terminals 101e and 101f via relays 13a and 13b. Relay SWs 14a, 14b, and 14c are connected to the power line 102e, 102f, and 102g sides, respectively, during grid-connected operation and to the power line 103e, 103f, and 103g sides, respectively, during off-grid operation. And the power lines 102e, 102f, and 102g are connected to the power lines 4a, 4b, and 4c, respectively. Also, the power lines 103e, 103f, and 103g are connected to the power lines 103c, 105b, and 103d, respectively.

[0034] During grid connection, the operations of the first power conditioner 20a and the second power conditioner 20b and relays SW6a - 6c and 8a - 8c are the same as in the first embodiment, and the single-phase loads 2 and 3 are supplied with power from the first power conditioner 20a and the second power conditioner 20b. At this time, power is also supplied from the PV power conditioner 20c to the single-phase loads 2 and 3 through the power lines 102e, 102f, and 102g.

[0035] During off-grid operation, relay SWs 6a - 6c and 8a - 8c are switched from the grid side to the first power conditioner 20a and the second power conditioner 20b side. And the first In the power conditioner 20a and the second power conditioner 20b, the relays 5a, 5b, 5c, and 5d are disconnected, and the relays 7a, 7b, 7c, and 7d are connected. Thereby, a 120-degree phase difference is provided between the output voltage from the output terminal 101a of the first inverter 10a, the output voltage between the output terminal 101b of the first inverter 10a and the output terminal 101d of the second inverter 10b, and the output voltage between the output terminal 101b of the first inverter 10a and the output terminal 101d of the second inverter 10b and the output terminal 101c of the second inverter 10b, and three-phase three-wire power is supplied to the three-phase load 9 through the power lines 103a, 103b, 103d, and 103c.

[0036] In the second embodiment, during power supply, the relays 13a and 13b of the PV power conditioner 20c are connected. The relays SW14a, 14b, and 14c connected to the PV power conditioner 20c are connected to the power lines 102e, 102f, and 102g during grid connection and to the power lines 103e, 103f, and 103g during independent operation. Here, the AC power supply device of the present invention is configured including the PV panel 11c and the PV inverter 10c.

[0037] When power is not supplied from the storage battery 11a to the single-phase loads 2 and 3 and power is supplied only from the storage battery 11b, the discharge power of the storage battery 11b becomes larger by the amount of power consumed by the single-phase loads 2 and 3, and the battery capacity decreases faster. When the battery capacity of one storage battery decreases to a region where discharge is impossible, even if the battery capacity of the other storage battery remains, power cannot be supplied to the three-phase load 9, so load imbalance is not preferable. Therefore, in the second embodiment, by connecting the output of the PV inverter 10c to the independent operation output of the second power conditioner 20b connected to the transformer Tr and supplying power to the single-phase loads 2 and 3, the storage battery 17b can be charged from the PV power conditioner 20c during independent operation. In this way, since the portion with large discharge power can be replenished by charging from the PV panel 11c, load imbalance can be eliminated. In the example shown in Fig. 2, the power line 103e connected to the output terminal 101e of the PV inverter 10c during autonomous operation is connected between the power line 103c connected to the autonomous operation output terminal of the second power conditioner 20b and the power line 104c, but it may also be connected to 105c connected to the secondary side of the transformer Tr. Further, the power line 103g connected to the output terminal 101f of the PV inverter 10c during autonomous operation is connected between the power line 103d connected to the autonomous operation output terminal of the second power conditioner 20b and the power line 104d, but it may also be connected to 105a connected to the secondary side of the transformer Tr.

[0038] [Example 3] Hereinafter, the distributed power system 31 according to Example 3 of the present invention will be described in more detail with reference to the drawings.

[0039] Fig. 3 is a diagram showing a schematic configuration of a distributed power system 31 according to Example 3 of the present invention. For the configurations common to those in the first and second embodiments, detailed descriptions thereof will be omitted by using the same reference numerals.

[0040] In the distributed power system 31 according to Example 3, in addition to the two first power conditioners 20a and the second power conditioner 20b respectively connected to the two storage batteries 11a and 11b, a single-phase PV power conditioner 20c connected to the PV panel 11c is provided. Here, the first power conditioner 20a has a first converter 12a that converts a DC voltage and a first inverter 10a that converts a DC voltage into an AC voltage. The first converter 12a and the first inverter 10a are connected by DC links 120a and 120b, and a smoothing capacitor is connected between the DC links 120a and 120b. Further, the second power conditioner 20b has a second converter 12b that converts a DC voltage and a second inverter 10b that converts a DC voltage into an AC voltage. The second converter 12b and the second i It is connected to the number converter 10b by DC links 120c and 120d, and a smoothing capacitor is connected between the DC links 120c and 120d. Further, the PV power conditioner 20c has a PV converter 12c that converts the DC voltage output from the PV panel 11c. Power lines 120g and 120h respectively connected to the output terminals 120e and 120f of the PV converter 12c are respectively connected to the DC links 120c and 120d of the second power conditioner 20b. The second converter 12b is a converter that converts the DC voltage in both directions and can charge and discharge the storage battery 11b, and corresponds to the bidirectional converter of the present invention. Also, the DC links 120c and 120d correspond to the DC circuit of the present invention. And the DC power supply device of the present invention is configured including the PV panel 11c and the PV converter.

[0041] In the distributed power system 31, similar to the distributed power system 21 according to the second embodiment, during independent operation, only the output from the second power conditioner 20b is supplied to the single-phase loads 2 and 3 via the transformer Tr. For this reason, the discharge power of the storage battery 11b becomes larger by the amount of power consumed by the single-phase loads 2 and 3, and the battery capacity decreases quickly. As explained in the second embodiment, when the battery capacity of one storage battery decreases to a region where it cannot be discharged, even if the battery capacity of the other storage battery remains, it becomes impossible to supply power to the three-phase load 9, so the load imbalance is not preferable. Therefore, in the third embodiment, by connecting the output of the PV converter 12c to the DC links 120c and 120d provided on the input side of the second inverter 10b of the second power conditioner 20b that is connected to the transformer Tr and supplies power to the single-phase loads 2 and 3, during independent operation, charging of the storage battery 11b with the DC power output from the PV converter 12c connected to the PV panel 11c is enabled. In this way, since the part with large discharge power can be replenished by charging from the PV panel 11c, the load imbalance can be eliminated.

[0042] 〔Embodiment 4〕 Hereinafter, the distributed power system 41 according to the fourth embodiment of the present invention will be described in more detail with reference to the drawings.

[0043] FIG. 4 is a diagram showing a schematic configuration of a distributed power system 41 according to Embodiment 4 of the present invention. For the components common to Embodiment 1, the same reference numerals are used and detailed description thereof is omitted.

[0044] In the distributed power system 41 according to Embodiment 4, similar to Embodiment 1, two single-phase first power conditioners 20a and second power conditioners 20b respectively connected to two storage batteries 11a and 11b are provided. The first power conditioner 20a and the second power conditioner 20b each have a single-phase first inverter 10a and a second inverter 10b.

[0045] In the distributed power system 41, when connected to the grid, relays 5a, 5b and relays 5c, 5d are connected, and relays SW6a, 6b, 6c are connected to the grid side, so that the power generated by the single-phase voltages of the first inverter 10a and the second inverter 10b is supplied to single-phase loads 2 and 3. On the other hand, during self-operation, the relays 5a, 5b, 5c, 5d on the side of the first inverter 10a and the second inverter 10b are disconnected, and relays 7a, 7b, 7c, 7d are connected. Then, by connecting relays SW8a, 8b, 8c to the side of the first power conditioner 20a and the second power conditioner 20b, the outputs of the first inverter 10a and the second inverter 10b are connected to a three-phase load 9. Further, by connecting relays SW6a, 6b, 6c to the side of the first inverter 10a and the second inverter 10b, the outputs of the first inverter 10a and the second inverter 10b are also supplied to single-phase loads 2 and 3.

[0046] In the distributed power system 41, different from the distributed power system 1 according to Embodiment 1, self- During operation, power is supplied to single-phase loads 2 and 3 from both the storage battery 11a and the storage battery 11b via the transformer Tr. Specifically, a power line 104a branched from a power line 103a connected to the output terminal 101a of the first inverter 10a via a relay 7a is connected to the primary side of the transformer Tr. Also, similar to the distributed power system 1, a power line 104c branched from a power line 103c connected to the output terminal 101c of the second inverter 10b via a relay 7c is connected to the primary side of the transformer Tr. At this time, the power line 103d connected to the output terminal 101d of the second inverter 10b via a relay 7d is connected to the power line 103b without branching, and the power output from the output terminal 101d of the second inverter 10b is supplied to the three-phase load 9 via the relay SW8b together with the power output from the output terminal 101b of the first inverter 10a. In this way, among the outputs of the two single-phase first power conditioners 20a and second power conditioners 20b, output terminals different from the output terminal 101b and the output terminal 101d, which have a common potential by V connection, are connected to the transformer Tr. Here, among the power lines 103a to 103d corresponding to the three-phase power lines of the present invention, the power lines 103a and 103c correspond to the three-phase power lines that supply the two-phase power of the present invention, and the primary side of the transformer Tr is connected between the power line 103a and the power line 103c via the power lines 104a and 104c. At this time, the power lines 103a and 103c connected to the primary side of the transformer Tr via the power lines 104a and 104c are connected to different first power conditioners 20a and second power conditioners 20b, respectively.

[0047] In this way, in the distributed power system 41, during autonomous operation, not only the three-phase load 9 but also the single-phase loads 2 and 3 are evenly supplied with power from the two single-phase first power conditioners 20a and second power conditioners 20b, so the load does not become unbalanced between the two single-phase first power conditioners 20a and second power conditioners 20b.

[0048] <Appendix 1> A distributed power generation system (1, 21, 31, 41) that is connected to a commercial power system (1a, 1b) and includes a distributed power source (11a, 11b) capable of independent operation, During independent operation, a power conversion device (20a, 20b) that converts the power output from the distributed power source (11a, 11b) into three-phase power and supplies it to a three-phase load (9), A transformer (Tr) provided between the power conversion device (20a, 20b) and a single-phase load (2, 3), Comprising: During independent operation, the primary side of the transformer (Tr) is connected between any two phases of the three-phase power lines (103a, 103b, 103c, 103d) that supply the three-phase power from the power conversion device (20a, 20b) to the three-phase load (9), and single-phase power lines (105a, 105b) that supply single-phase power to the single-phase load (2, 3) are connected to the secondary side of the transformer (Tr). The distributed power generation system (1, 21, 31, 41) is characterized by this.

Description of Reference Numerals

[0049] 1, 21, 31, 41: Distributed power generation system 1a, 1b: Commercial power system 2, 3: Single-phase load 9: Three-phase load 10b: Second inverter 11a, 11b: Storage battery 11c: PV panel 12b: Second converter 12c: PV converter 103a~103d: Three-phase power lines 105a, 105b: Single-phase power lines 20a, 20b: Power conditioner Tr: Transformer

Claims

1. A distributed power generation system including a distributed power source that is connected to a commercial power system and capable of independent operation, During independent operation, a power conversion device that converts the power output from the distributed power source into three-phase power and supplies it to a three-phase load, A transformer provided between the power conversion device and a single-phase load, Comprising, The power conversion device, During the interconnected operation with the commercial power system, includes a plurality of power conversion devices that are connected in parallel and output single-phase power supplied to the same single-phase load, During independent operation, disconnects the connection with the single-phase load, supplies the three-phase power obtained by combining the outputs of the plurality of power conversion devices with different phases to the three-phase load, and the primary side of the transformer is connected between any two of the three-phase power lines that supply the three-phase power from the plurality of power conversion devices to the three-phase load, and a single-phase power line that supplies single-phase power to the single-phase load is connected to the secondary side of the transformer. A distributed power generation system characterized by this.

2. The distributed power generation system according to claim 1, wherein the three-phase power lines connected to the primary side are respectively connected to different power conversion devices among the plurality of power conversion devices.

3. The distributed power generation system according to claim 1, wherein all of the three-phase power lines connected to the primary side are connected to any one of the plurality of power conversion devices.

4. The distributed power source is a storage battery, Has an AC power supply device that outputs single-phase AC power, The power conversion device to which the three-phase power line connected to the primary side is connected can charge and discharge the storage battery, The distributed power generation system according to claim 3, characterized in that the output terminal of the AC power supply device is connected in parallel to the transformer on the three-phase power line connected to the primary side.

5. The distributed power source is a storage battery, Has a DC power supply device that outputs DC power, The power conversion device that supplies power to the primary side via the three-phase power line includes an inverter that converts DC power into AC power, a bidirectional converter provided between the inverter and the storage battery and capable of charging and discharging the storage battery, and a DC circuit that connects the inverter and the bidirectional converter, The distributed power generation system according to claim 3, characterized in that the output terminal of the DC power supply device is connected in parallel to the inverter in the DC circuit.

Images