Distributed power system

Abstract

To provide a distributed power supply system which can supply normal voltage to a three-wire load when three-wire power is supplied to the three-wire load by combining a plurality of pieces of single-phase power to be individually output.SOLUTION: A distributed power supply system comprises: a power supply device which supplies DC power; a plurality of power conditioners which convert the DC power input from the power supply device into single-phase AC; and an output terminal connected with a single-phase load which is a power supply object and a commercial power system, and supplies power to the load by predetermined output voltage. The plurality of power conditioners are connected in parallel with one another, and power is supplied to the same single-phase load in a linkage operation with the commercial power system, and power by three-wire voltage is supplied to the three-wire load by blocking connection with the single-phase load and combining output with different phases of the plurality of power conditioners to simultaneously supply power to the three-wire load in an autonomous operation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a distributed power system including a plurality of inverters.

Background Art

[0002] Conventionally, a distributed power system has been proposed in which distributed power sources such as storage batteries and solar cells are installed, and normally, the distributed power sources are connected to a commercial power system to supply power to a single-phase load, and when the power supply from the commercial power system stops due to a power outage or the like, power can be supplied from a plurality of distributed power sources to a three-phase load (see, for example, Patent Document 1).

[0003] However, when supplying three-phase power through three lines by combining a plurality of distributed power sources in this way, there has been a problem that appropriate three-phase power cannot be obtained if the power of each phase is output separately.

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 system that can supply a normal voltage to a three-wire load when combining a plurality of single-phase powers output individually to supply three-wire power to a three-wire load.

Means for Solving the Problems

[0006] In order to solve the above problems, the present invention is A distributed power system comprising a power supply device that supplies DC power, a plurality of power conditioners that convert the DC power input from the power supply device into single-phase AC, and an output terminal connected to a single-phase load that is a power supply target and a commercial power system, and supplying power to the single-phase load with a predetermined output voltage, During grid-connected operation with the commercial power system, the plurality of power conditioners are connected in parallel and power is supplied to the same single-phase load, During stand-alone operation, the connection to the single-phase load is cut off, and by combining outputs with different phases of the plurality of power conditioners and simultaneously supplying power to a three-phase load, power with a three-phase voltage is supplied to the three-phase load. It is characterized by this.

[0007] According to this, in a distributed power system that supplies a three-phase voltage generated by combining outputs with different phases of a plurality of power conditioners to a three-phase load, the outputs of the respective power conditioners are simultaneously supplied to the three-phase load. Therefore, it is possible to supply a normal three-phase voltage with all phases present to the three-phase load without supplying an abnormal three-phase voltage such as a lack of voltage in some phases to the three-phase load. As the power supply device, various distributed power sources such as storage batteries, solar cells, and fuel cells can be applied.

[0008] Also, in the present invention, It may be provided with a circuit opening / closing unit that simultaneously connects the circuits connecting the plurality of power conditioners and the three-phase load.

[0009] According to this, by connecting the circuit opening / closing unit, it is possible to simultaneously supply outputs with different phases of the plurality of power conditioners to the three-phase load, so that a normal three-phase voltage can be supplied to the three-phase load. Such a circuit opening / closing unit may be provided outside the plurality of power conditioners or inside the plurality of power conditioners.

[0010] Also, in the present invention, Each of the plurality of power conditioners may supply power to the three-wire load by the three-wire voltage based on information indicating the timing for supplying outputs having different phases.

[0011] In this way, since each of the plurality of power conditioners supplies power to the three-wire load by the three-wire voltage based on the information indicating the timing for supplying outputs having different phases, the three-wire voltage can be supplied to the three-wire load simultaneously. Therefore, a normal three-wire voltage can be supplied to the three-wire load. In the power supply by the three-wire voltage to the three-wire load, three-phase three-wire power supply is possible by outputting a phase difference of the three-wire voltage as 120°, but single-phase three-wire power supply can also be realized with a similar configuration by outputting a phase difference of two wires as 180°.

Advantages of the Invention

[0012] According to the present invention, there can be provided a distributed power supply system capable of supplying a normal voltage to a three-wire load when combining a plurality of single-phase powers output individually to supply three-wire power to the three-wire load.

Brief Description of the Drawings

[0013]

Figure 1

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Mode for Carrying Out the Invention

[0014] 〔Application Example〕 Hereinafter, application examples of the present invention will be described with reference to the drawings.

[0015] 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 7a and 7b respectively 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, when the system is interconnected, the outputs of the first inverter 10a and the second inverter 10b are connected by relays 5a, 5b and relays 5c, 5d, and the power generated by the single-phase voltages of the first inverter 10a and the second inverter 10b is supplied to the customer loads 2 and 3. On the other hand, during independent operation, the relays 9a, 9b, and 9c of the external relay 9 are connected, and the relays SW6a, 6b, and 6c are connected to the power conditioner 20a and 20b sides, so that the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase independent operation load 8.

[0016] During independent operation, a three-phase voltage is generated by providing a 120-degree phase difference between the output voltages of the first inverter 10a and the second inverter 10b, and three-phase three-wire power is supplied.

[0017] When voltages with different phases are output from the two power conditioners in this way, there is a possibility that the three-phase voltage will not be output normally. For this reason, in the distributed power system 1, an external relay 9 is provided, and the output timing of the three-phase voltage from the two power conditioners as shown in FIG. 3 is controlled. Note that it is obvious that a single-phase three-wire voltage output is achieved by providing a phase difference of 180 degrees between the output voltages of the first inverter 10a and the second inverter 10b.

[0018] First, the first inverter 10a and the second inverter 10b start preparing for independent operation (step S1), and the first inverter 10a starts independent operation output (step S2). The second inverter 10b waits for synchronization with the independent operation output of the first inverter 10a to be completed (step S3). At this stage, the relays SW6a, 6b, and 6c are connected to the side of the power converters 20a and 20b, but the relays 9a, 9b, and 9c of the external relay 9 are not connected.

[0019] Next, the first inverter 10a starts independent operation output (step S2), and the second inverter 10b waits for synchronization with the independent operation output of the first inverter 10a to be completed (step S3). Then, when the synchronization of the second inverter 10b to the first inverter 10a is completed, the second inverter 10b starts independent operation output (step S4). At this stage, the second inverter 10b transmits a relay drive signal to the external relay 9 and connects the relays 9a, 9b, and 9c (step S5), and simultaneously applies the three-phase voltage generated by the first inverter 10a and the second inverter 10b to the independent operation load 8 (step S6).

[0020] In this way, in the distributed power system 1, after the outputs of the first inverter 10a and the second inverter 10b are synchronized and a normal three-phase voltage can be generated, the external relay 9 is operated to apply the three-phase voltage to the independent operation load 8, thereby preventing improper voltage application.

[0021] [Embodiment 1] Hereinafter, the distributed power system 1 according to Embodiment 1 of the present invention will be described in more detail with reference to the drawings.

[0022] In the distributed power system 1 in this embodiment, two single-phase first power conditioners 20a and second power conditioners 20b, which are examples of power supply devices, are provided and are respectively connected to two storage batteries 7a and 7b. 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, the outputs of the first inverter 10a and the second inverter 10b are connected to a single-phase commercial power system 1a and single-phase consumer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5a, 5b and relays 5c, 5d. Further, relays SW6a, 6b, and 6c are connected to the grid side, so that the output from the three-phase commercial power system 1b is connected to the three-phase self-operating load 8. Also, the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase self-operating load 8 as a three-phase load via relays 9a, 9b, and 9c of an external relay 9 provided outside the first inverter 10a and the second inverter 10b and relays SW6a, 6b, and 6c. Then, when the relays 5a, 5b and the relays 5c, 5d are connected, the power generated by the single-phase voltages of the first inverter 10a and the second inverter 10b is supplied to the consumer loads 2 and 3. On the other hand, when the relays 9a, 9b, and 9c are connected and the relays SW6a, 6b, and 6c are connected to the power conditioner 20a, 20b side, the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase self-operating load 8. That is, relays 9a, 9b, and 9c of the external relay 9, which is an example of a circuit opening / closing unit, are provided in the circuit that connects the first inverter 10a, the second inverter 10b, and the self-operating load 8. The relays 9a, 9b, and 9c of the external relay 9 are connected or disconnected by an external relay drive signal transmitted from the second inverter 10b. The external relay 9 can be installed, for example, in a distribution board. In the circuit connecting the first inverter 10a, the second inverter 10b and the self-operating load 8, relays 9a, 9b, and 9c of an external relay 9, which is an example of a circuit opening / closing unit, are provided. The relays 9a, 9b, and 9c of the external relay 9 are connected or disconnected by an external relay drive signal transmitted from the second inverter 10b. The external relay 9 can be installed, for example, in a distribution board.

[0023] During the grid-connected operation with the commercial power system, when relays 5a, 5b and relays 5c, 5d are connected, the power generated by the single-phase voltages of the first inverter 10a and the second inverter 10b is supplied to the customer loads 2 and 3. On the other hand, during the stand-alone operation, when relays 9a, 9b, 9c are connected and relays SW6a, 6b, 6c are connected to the power converter side, the power generated by the output voltages of the first inverter 10a and the second inverter 10b is supplied to the stand-alone operation load 8. In this embodiment, during this stand-alone operation, by providing a phase difference of 120 degrees between the output voltages of the first inverter 10a and the second inverter 10b, a three-phase voltage is generated and three-phase three-wire power is supplied. Note that by providing a phase difference of 180 degrees between the output voltages of the first inverter 10a and the second inverter 10b, a single-phase three-wire voltage output is obtained (the same applies to Embodiment 2 and Embodiment 3).

[0024] Figure 2 shows the relationship diagram of the three-phase voltage. As shown in Figure 2(A), in this embodiment, the first inverter 10a outputs the first-phase output voltage V1, and the second inverter 10b outputs the second-phase output voltage V2 that lags behind the first inverter 10a and the second inverter 10b by 120 degrees. For the output of the third phase, by outputting an output voltage of V3 = -(V1 + V2), an output voltage that lags behind V2 by another 120 degrees can be generated.

[0025] In the distributed power system 1, the output voltage from the first inverter 10a is input to the second inverter 10b and its value is measured. In the second inverter 10b, based on the measured value, an output voltage V2 that lags behind the output voltage V1 from the first inverter 10a by 120 degrees is generated and output. With such a configuration, the single-phase voltages of the two first inverters 10a and the second inverter 10b are combined and synchronized to generate a three-phase voltage, and power is supplied to the three-phase stand-alone operation load 8 during the stand-alone operation.

[0026] Figure 3 shows the procedure of the three-phase output timing control in the distributed power system 1. First, by detecting the interruption of grid power or receiving an instruction for independent operation from a higher-level device, the first inverter 10a and the second inverter 10b start preparing for independent operation (step S1). At this stage, the relays SW6a, 6b, and 6c are connected to the side of the power converters 20a and 20b, but the relays 9a, 9b, and 9c of the external relay 9 are not connected.

[0027] Next, the first inverter 10a starts independent operation output (step S2). As described above, since the relays 9a, 9b, and 9c of the external relay 9 are not connected, the independent operation output of the first inverter 10a is not supplied to the independent operation load 8.

[0028] Next, the second inverter 10b waits for synchronization with the independent operation output of the first inverter 10a to be completed (step S3). As described above, since the output voltage from the first inverter 10a is input to the second inverter 10b, the second inverter 10b can determine whether synchronization with the independent operation output of the first inverter 10a has been completed.

[0029] When the synchronization of the second inverter 10b with the first inverter 10a is completed, the second inverter 10b starts independent operation output (step S4).

[0030] Then, the second inverter 10b transmits a relay drive signal to the external relay 9 to connect the relays 9a, 9b, and 9c (step S5). As a result, the three-phase voltages generated by the first inverter 10a and the second inverter 10b are simultaneously applied to the independent operation load 8 (step S6).

[0031] In this way, in the distributed power system 1, after the outputs of the first inverter 10a and the second inverter 10b are synchronized and a normal three-phase voltage can be generated, the external relay 9 is operated to apply a three-phase voltage to the independent operation load 8, thereby preventing an improper voltage application and supplying power with a normal three-phase voltage to the independent operation load 8.

[0032] [Example 2] Hereinafter, the distributed power system 11 according to Example 2 of the present invention will be described. FIG. 4 shows a schematic configuration of the distributed power system 11. For the same configuration as that of the distributed power system 1 according to Example 1, detailed description will be omitted by using the same reference numerals.

[0033] In the distributed power system 11, a synchronization signal is transmitted from the first inverter 10a to the second inverter 10b, and communication is performed between the first inverter 10a and the second inverter 10b.

[0034] Referring to FIG. 5, a three-phase output timing control method in the distributed power system 11 will be described. In FIG. 5, the output voltage V1 from the first inverter 10a is shown by a solid line, the output voltage V2 from the second inverter 10b is shown by a broken line, and the output voltage V3 generated by -(V1 + V2) is shown by a dashed-dotted line. Here, the first inverter 10a transmits the output voltage V1 and a synchronization signal (a pulse signal that turns on at the timing when V1 becomes 0) to the second inverter 10b. Based on the synchronization signal, after the phases of the output of the output voltage V2 of the second inverter 10b and the output of the output voltage V1 of the first inverter 10a are synchronized, the first inverter 10a transmits information on the output start timing to the second inverter 10b by communication. Assuming that the time shown by the dotted line in FIG. 5 is the output start timing, based on this information on the output start timing, the first inverter 10a and the second inverter 10b start output simultaneously. Thereby, three-phase voltages can be simultaneously applied to the self-operating load 8, and power can be supplied to the self-operating load 8 with a normal three-phase voltage.

[0035] Here, the information on the output start timing is an example of information indicating the timing for supplying outputs with different phases. Such information on the output start timing is not limited to being transmitted from the first inverter 10a to the second inverter 10b as described above, and may be transmitted from a host device such as a controller of the first inverter 10a and the second inverter 10b to the first inverter 10a and the second inverter 10b.

[0036] 〔Example 3〕 Hereinafter, the distributed power system 21 according to Example 3 of the present invention will be described. FIG. 6 shows a schematic configuration of the distributed power system 21. For the configuration similar to that of the distributed power system 1 according to Example 1, the same reference numerals are used and the detailed description is omitted.

[0037] In the distributed power system 21, the first inverter 10a and the second inverter 10b each include an internal relay 12 and an internal relay 13. That is, in the distributed power system 21, the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase self-operating load 8 via relays 12a, 12b provided inside the first inverter 10a, relays 13a, 13b provided inside the second inverter 10b, and relays SW6a, 6b, 6c. Therefore, when the relays 12a, 12b and the relays 13a, 13b are connected and the relays SW6a, 6b, 6c are connected to the power conditioner 20a, 20b side, the outputs of the first inverter 10a and the second inverter 10b are connected to the three-phase self-operating load 8. That is, in the circuit connecting the first inverter 10a, the second inverter 10b and the self-operating load 8, internal relays 12, relays 12a, 12b and internal relay 13 relays 13a, 13b of are provided.

[0038] Also, in the distributed power system 21, similar to the distributed power system 11 according to Example 2, a synchronization signal is transmitted from the first inverter 10a to the second inverter 10b, and communication is performed between the first inverter 10a and the second inverter 10b.

[0039] FIG. 7 shows the procedure of three-phase output timing control in the distributed power system 21. For the processing similar to the procedure of three-phase output timing control in the distributed power system 1, the same reference numerals are used and the description is omitted. First, similar to the distributed power system 1, in the distributed power system 21, the preparation for autonomous operation is also started (step S1). At this stage, the relays SW6a, 6b, and 6c are connected to the side of the power conditioners 20a and 20b, but the relays 12a, 12b of the internal relay 12 and the relays 12a, 12b of the internal relay 13 are not connected.

[0040] Steps S2 and S4 of the three-phase output timing control are the same as those in the distributed power system 1. However, in the distributed power system 21, when waiting for the synchronization completion of the second inverter 10b in step S13, based on the synchronization signal transmitted from the first inverter 10a as described above, the phase of the output voltage of the second inverter 10b is synchronized with the phase of the output voltage of the first inverter 10a.

[0041] When the autonomous operation output of the second inverter 10b is started (step S4), the first inverter 10a transmits the information on the on-timing of the internal relay 13 to the second inverter 10b by communication. Then, based on this information on the internal relay on-timing, the internal relay 12 and the internal relay 13 are turned on simultaneously (step S15). As a result, the three-phase voltages by the first inverter 10a and the second inverter 10b are simultaneously applied to the autonomous operation load 8 (step S6).

[0042] In this way, in the distributed power system 21, after the outputs of the first inverter 10a and the second inverter 10b are synchronized and a normal three-phase voltage can be generated, the internal relay 12 and the internal relay 13 are operated to apply the three-phase voltage to the autonomous operation load 8, thereby preventing an improper voltage application and supplying power with a normal three-phase voltage to the autonomous operation load 8.

[0043] <Appendix 1> A distributed power system (1) comprising a power supply device (7a, 7b) for supplying DC power, a plurality of power conditioners (20a, 20b) for converting the DC power input from the power supply device into single-phase AC, and output terminals (17, 18, 19) connected to a single-phase load (2, 3) to be powered and a commercial power system, and supplying power to the load at a predetermined output voltage, During grid-connected operation with the commercial power system, the plurality of power conditioners (20a, 20b) are connected in parallel and power is supplied to the same single-phase load (2, 3), During stand-alone operation, the connection to the single-phase load (2, 3) is cut off, and the outputs of the plurality of power conditioners (20a, 20b) with different phases are combined to simultaneously supply power to a three-phase load (8), thereby supplying power to the three-phase load at a three-phase voltage. A distributed power system characterized by this.

Explanation of symbols

[0044] 1: Distributed power system 2, 3: Single-phase load 7a, 7b: Battery 8: Stand-alone operation load 17, 18, 19: Output terminal 20a, 20b: Power conditioner

Claims

1. A distributed power system comprising a power supply device that supplies direct current power, a plurality of power conditioners that convert the direct current power input from the power supply device into single-phase alternating current, and an output terminal connected to a single-phase load that is a power supply target and a commercial power system, and supplying power to the single-phase load with a predetermined output voltage, wherein during grid-connected operation with the commercial power system, the plurality of power conditioners are connected in parallel and power is supplied to the same single-phase load, during stand-alone operation, the connection to the single-phase load is cut off, and after synchronization of outputs with different phases of the plurality of power conditioners is completed, the outputs with different phases of the plurality of power conditioners are combined to simultaneously supply power to a three-wire load, thereby supplying power with a three-wire voltage to the three-wire load. A distributed power system characterized by this.

2. The distributed power system according to claim 1, further comprising a circuit opening / closing unit that simultaneously connects circuits connecting the plurality of power conditioners and the three-wire load.

3. The distributed power system according to claim 2, wherein the circuit opening / closing unit is provided outside the plurality of power conditioners.

4. The distributed power system according to claim 2, wherein the circuit opening / closing unit is provided inside the plurality of power conditioners.

5. The distributed power system according to claim 1, wherein each of the plurality of power conditioners supplies power with a three-wire voltage to the three-wire load based on information indicating the timing of supplying outputs with different phases.

6. The distributed power system according to any one of claims 1 to 5, wherein the power supply with a three-wire voltage to the three-wire load is by a three-phase three-wire system.

7. The power supply with a three-wire voltage to the three-wire load is by a single-phase three-wire system, characterizing the distributed power system according to any one of claims 1 to 5.

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