JP2020043748A - Power conversion system - Google Patents

Abstract

To provide a power conversion system capable of reducing a loss in a low output state.SOLUTION: A power conversion system includes: a storage battery 2; a three-phase system interconnection inverter 3 including a filter connected in parallel to the storage battery 2; a single-phase inverter 4 including a filter having a smaller current capacity than that of the three-phase system interconnection inverter 3; and a control unit 5 for controlling the three-phase interconnection inverter 3 on the basis of a state of a power system connected to the three-phase interconnection inverter 3 and controlling the single-phase inverter 4 on the basis of a state of an independent power supply connected to the single-phase inverter.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a power conversion system.

  In recent years, with the expansion of renewable energies such as solar power generation and wind power generation, and the introduction of systems including storage batteries, power supply systems in the event of disasters and power conversion systems mainly using VPP (virtual power plant) have increased. I have. Such a power conversion system supplies power from a power source such as a photovoltaic power generator or a storage battery to a customer when power is cut off from a power grid during a normal power peak cut or a disaster.

  The power conversion system as described above is generally a system in which a power supply and a power conversion device that converts DC to AC are combined, and supplies power to a load. This power conversion system is operated in connection with a power system during normal operation. On the other hand, when the power conversion system is disconnected from the power system due to a disaster or the like, the power conversion system performs an independent operation of supplying power of a power supply to a load. For example, in Patent Document 1, a photovoltaic power generation and a storage battery are used as power supplies, each power supply is connected to DC / DC, and is configured by DC / AC that outputs three-phase power or single-phase power.

Japanese Patent No. 6200123

  According to the prior art, the output of the power converter generally has the capacity of the three-phase grid-connected power converter when supplying single-phase power in the three-phase grid-connected power converter. In comparison, the required single-phase power is often low. Further, a transformer for converting a three-phase output to a single-phase output is required. Therefore, the loss increases regardless of the normal operation and the self-sustaining operation. Therefore, it is possible to reduce the loss in the low output state by switching a plurality of inverters having different capacities depending on the configuration of the apparatus. However, a converter using a photovoltaic power generation or a storage battery as a power source is connected to each power source. In addition, since the same capacity as that of the three-phase output is required, there is a possibility that the device efficiency may be reduced in a low output state such as an independent operation.

  The present embodiment has been proposed to solve the above-described problems of the related art. An object of the present embodiment is to provide a power conversion system capable of reducing a loss in a low output state.

  The power conversion system according to this embodiment includes a storage battery, a plurality of inverters having different capacities including a filter connected to the storage battery, and a state of a power system connected to at least one of the plurality of inverters. A control unit for controlling the plurality of inverters.

  According to the present embodiment, it is possible to provide a power conversion system capable of reducing a loss in a low output state.

FIG. 1 is a block diagram showing a configuration of a power conversion system according to a first embodiment. FIG. 6 is a block diagram showing a configuration of a power conversion system according to a second embodiment. FIG. 9 is a block diagram showing a configuration of a power conversion system according to a third embodiment. FIG. 13 is a block diagram showing a configuration of a power conversion system according to a fourth embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments do not limit the present invention.

(1st Embodiment)
FIG. 1 is a block diagram illustrating a configuration of a power conversion system 1 according to the first embodiment. As shown in FIG. 1, a power conversion system 1 according to the present embodiment includes a storage battery 2, a three-phase system interconnection inverter 3, a single-phase inverter 4, an interconnection switch 11, and a three-phase load switch 12. , An independent power switch 21, a single-phase load switch 22, and the control unit 5 for controlling them.

  The storage battery 2 corresponds to a power supply that supplies power to the three-phase load 200 or the single-phase load 400 via the three-phase system interconnection inverter 3. The three-phase load 200 corresponds to, for example, a three-phase 200V electric product. The single-phase load 400 corresponds to, for example, a single-phase 100V electric appliance. The capacity of the storage battery 2 is several tens of kWh.

  The three-phase system interconnection inverter 3 converts the AC voltage output from the power system 100 into a DC voltage having a predetermined value, and charges the storage battery 2. Further, the DC voltage output from the storage battery 2 is converted into an AC voltage having a predetermined value, and is connected to the power system 100 and supplies power to the three-phase load 200.

  Single-phase inverter 4 converts the AC voltage output from independent power supply 300 into a DC voltage having a predetermined value, and charges storage battery 2. When there is no output from the independent power supply 300, it is also possible to supply the single-phase load 400 with the DC voltage output from the storage battery 2.

  The control unit 5 controls the three-phase system interconnection inverter 3 and the single-phase inverter 4 based on the state of the power system 100. As the control unit 5, for example, a CPU (Central Processing Unit) that executes various control operations based on a predetermined program can be used.

(Operation of First Embodiment)
Hereinafter, the operation of the power conversion system 1 according to the present embodiment will be described with reference to FIG. Here, the normal operation and the independent operation will be described.

  In the normal operation, first, the control unit 5 turns on the interconnection switch 11, the three-phase load switch 12, and the single-phase load switch 22, and turns off the independent power switch 21. Next, the control unit 5 drives the three-phase system interconnection inverter 3. Thereby, the DC power of the storage battery 2 is converted into AC power via the three-phase system interconnection inverter 3. At this time, the three-phase system interconnection inverter 3 is controlled by the control unit 5 to output three-phase AC power. At the same time, the control unit 5 drives the single-phase inverter. Thereby, the DC power of storage battery 2 is converted to AC power via single-phase inverter 4. At this time, the single-phase inverter 4 is controlled by the control unit 5 to output single-phase AC power.

  In normal operation, the power conversion system 1 is operated by the control unit 5 according to a predetermined power schedule. The storage battery 2 is discharged during a time period when the power consumption of the three-phase load 200 is large, and power is supplied to the three-phase load 200, and the storage battery 2 is charged from the power system during a time period when the power consumption of the three-phase load 200 is small. In addition, the single-phase inverter supplies power to the single-phase load 400 by the control unit 5.

  In the present embodiment, the control unit 5 detects an AC voltage input from the power system 100 to the three-phase system interconnection inverter 3. When this detection voltage becomes smaller than the threshold value, the control unit 5 switches from normal operation to independent operation. In the independent operation, the storage battery 2 functions as a power supply that supplies power to the three-phase load 200 and the single-phase load 400.

  First, the control unit 5 turns off the interconnection switch 11 and the independent power supply switch 21 and turns on the three-phase load switch 12 and the single-phase load switch 22. Next, the control unit 5 controls the three-phase system interconnection inverter 3 to output three-phase AC power, and controls the single-phase inverter 4 to output single-phase AC power. As a result, three-phase AC power is supplied from the three-phase system interconnection inverter 3 to the three-phase load 200, and single-phase AC power is supplied from the single-phase inverter 4 to the single-phase load 400.

  Further, the control unit 5 detects an AC voltage input from the independent power supply 300 to the single-phase inverter 4. When this detection voltage becomes larger than the threshold value, the independent power switch 21 is turned on. Thereby, the control unit 5 performs control so that single-phase AC power can be input based on the state of the independent power supply 300. As a result, power is supplied from the independent power supply 300 to the storage battery 2 via the single-phase inverter 4. The independent power supply 300 is, for example, a single-phase 100 V output during the self-sustaining operation of the solar power generation system. In general, the independent power supply 300 has a lower capacity than the three-phase system interconnection inverter 3, and therefore, the single-phase inverter 4 may have a capacity as low as the independent power supply 300.

(Effect of First Embodiment)
According to the present embodiment, for the power supply to the single-phase load 400 in the power conversion system 1, during normal operation, the single-phase AC power is supplied by the single-phase inverter 4 without passing through the three-phase interconnection inverter 3. Since power can be supplied to the single-phase load 400, it can be operated efficiently. Similarly, during the self-sustaining operation, the single-phase inverter 4 can efficiently charge the storage battery 2 with the single-phase power generated by the independent power supply 300 without passing through the three-phase system interconnection inverter 3. Therefore, the time during which power can be supplied to the three-phase load 200 via the storage battery 2 can be lengthened.

(2nd Embodiment)
FIG. 2 is a block diagram illustrating a configuration of a power conversion system 1A according to the second embodiment. The same components as those of the power conversion system 1 according to the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

  The configuration of the power conversion system 1A will be described. In power conversion system 1A, first DC / DC converter 6 is provided between storage battery 2 and three-phase system interconnection inverter 3, and second DC / DC converter 7 is provided between storage battery 2 and single-phase inverter 4. . The second DC / DC converter 7 has a smaller power capacity than the first DC / DC converter 6. The first DC / DC converter 6 and the second DC / DC converter 7 are controlled by the control unit 5 to output DC power.

(Operation of Second Embodiment)
Next, the operation of the power conversion system 1A will be described. The first DC / DC converter 6 converts a DC voltage output from the storage battery 2 into a predetermined DC voltage. The three-phase system interconnection inverter 3 converts the DC voltage output from the first DC / DC converter 6 into an AC voltage having a predetermined value. At this time, the DC voltage output from the first DC / DC converter 6 can be determined according to the capacity of the three-phase inverter. Similarly, the second DC / DC converter 7 converts a DC voltage output from the storage battery 2 into a predetermined DC voltage. Single-phase inverter 4 converts the DC voltage output from second DC / DC converter 7 into an AC voltage having a predetermined value. At this time, the DC voltage output from the second DC / DC converter 7 can be determined according to the capacity of the single-phase inverter 4, and the DC voltage output differs between the first DC / DC converter 6 and the second DC / DC converter 7. You may. The other configuration is the same as that of the power conversion system 1 according to the first embodiment, and thus the description thereof is omitted.

(Effect of Second Embodiment)
According to the present embodiment, even when the output voltage of the storage battery 2 is different from the input voltage range of the three-phase system interconnection inverter 3 and the single-phase inverter 4, a predetermined DC voltage is output by the DC / DC converter. It becomes possible to drive. Further, even when the input voltage ranges of the three-phase grid-connected inverter 3 and the single-phase inverter 4 are different, one of the voltage between the storage battery 2 and the three-phase grid-connected inverter 3 and between the storage battery 2 and the single-phase inverter 4 or Operation is possible by using a DC / DC converter for both. As described above, the specifications of the storage battery 2, the three-phase system interconnection inverter 3, and the single-phase inverter 4 in the power conversion system 1A can be diversified, and the system can be easily configured. Furthermore, since the DC / DC converter to be connected is connected to only one inverter, the capacity can be the same as that of the inverter. Further, the inverter can be determined to have an optimum capacity depending on the load, so that an efficient configuration is required. Becomes possible.

(Third embodiment)
FIG. 3 is a block diagram illustrating a configuration of a power conversion system 1B according to the third embodiment. The same components as those of the power conversion system 1 according to the above-described first embodiment and the power conversion system 1A according to the second embodiment are denoted by the same reference numerals, and detailed description will be omitted.

  The configuration of the power conversion system 1B will be described. In the power conversion system 1B, the operation display unit 8 is connected to the control unit 5.

(Operation of Third Embodiment)
Next, the operation of the power conversion system 1B will be described. In the power conversion system 1B, the operation display unit 8 automatically shifts to normal operation from a normal operation to a self-sustained operation in the event of a power outage by a user's operation, or waits and manually shifts to the independent operation by the operation display unit. Can be determined. In addition, when the power system is restored, whether to shift from the independent operation to the normal operation, the operation is automatically shifted by the user operation, or the independent operation is continued, and the operation is switched to the interconnected operation by the user operation. Can be determined. The operation display unit 8 can also set and change the power schedule in normal operation, and check the input / output voltage value, current value, power value, and failure history of the device. Other configurations are the same as those of the power conversion system 1 according to the first embodiment and the power conversion system 1A according to the second embodiment, and thus description thereof will be omitted.

(Effect of Third Embodiment)
According to the present embodiment, since the operation of the power conversion system 1B can be determined according to the usage of the user, the power of the storage battery 2 can be effectively used.

(Fourth embodiment)
FIG. 4 is a block diagram illustrating a configuration of a power conversion system 1C according to the fourth embodiment. The same components as those of the power conversion system 1 according to the first embodiment, the power conversion system 1A according to the second embodiment, and the power conversion system 1B according to the third embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Description is omitted.

  The configuration of the power conversion system 1C will be described. In the power conversion system 1C, connection with the external communication control unit 500 is enabled.

(Operation of Fourth Embodiment)
Next, the operation of the power conversion system 1C will be described. In the power conversion system 1C, an operation similar to that of the operation display unit 8 in the power conversion system 1C can be performed by communication in response to a command from the external communication control unit 500. It is also possible to control a plurality of power conversion systems 1C.

(Effect of Fourth Embodiment)
According to the present embodiment, even when the power conversion system 1C is installed in a distant place, the system can be controlled, so that the convenience is improved. Further, since it becomes possible to control a plurality of power conversion systems, it is possible to cope with a large-capacity power supply.

  Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 ... Power conversion system 2 ... Storage battery 3 ... Three-phase system interconnection inverter 4 ... Single-phase inverter 5 ... Control part 6 ... 1st DC / DC converter 7 ... 2nd DC / DC converter 8 Operation display unit 11 Interconnection switch 12 Three-phase load switch 21 Independent power switch 22 Single-phase load switch 100 Power system 200: three-phase load 300: independent power supply 400: single-phase load 500: communication control unit

Claims (5)

  A storage battery, a plurality of inverters having different capacities including a filter connected to the storage battery, and a control unit that controls the plurality of inverters based on a state of a power system connected to at least one of the plurality of inverters, A power conversion system comprising:   The plurality of inverters includes a three-phase grid-connected inverter and a single-phase inverter having a smaller current capacity than the three-phase grid-connected inverter, and the control unit includes a power system connected to the three-phase grid-connected inverter. The power conversion system according to claim 1, wherein the three-phase interconnection inverter is controlled based on a state, and the single-phase inverter is controlled based on a state of an independent power supply connected to the single-phase inverter.   A bidirectional DC / DC converter that boosts the DC power of the storage battery, and is connected between at least one of the storage battery and the three-phase inverter and between the storage battery and the single-phase inverter. The power conversion system according to claim 2, wherein   The power conversion system according to any one of claims 1 to 3, further comprising an operation display unit connected to the control unit, wherein the operation display unit displays a command and a state to the control unit. .   5. The power conversion system according to claim 1, wherein the control unit is connected to a communication control unit, and performs control according to a communication command from the communication control unit. 6.

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