JP6629694B2 - POWER CONTROL DEVICE AND ITS CONTROL METHOD - Google Patents

Description

  The present invention relates to a power control device and a control method thereof.

  In recent years, installing a distributed power supply in a customer facility is becoming widespread. Further, with the diversification of distributed power sources, various distributed power sources such as solar cells, storage batteries, fuel cells, and gas generators may be installed in customer facilities. In this case, it is required in the customer facility to efficiently control various distributed power sources. Therefore, a power control device that centrally manages and operates various distributed power sources is known (Patent Document 1).

JP 2014-212656 A

  An object of the present invention made in view of such a point is to provide a power control device and a control method thereof capable of efficiently controlling various distributed power sources.

  A power control device according to one embodiment of the present invention includes a converter connected to a storage battery, an inverter that converts DC power supplied from the converter into AC power, and loads AC power from the inverter during autonomous operation. And a terminal to which the output power of the power generator is supplied when charging the storage battery, and a control unit for controlling the converter and the inverter. The controller reduces the DC link voltage, which is a voltage between the converter and the inverter, to a predetermined value when the storage battery is fully charged during the self-sustaining operation.

  In addition, the control method of the power control device according to one embodiment of the present invention includes a converter connected to a storage battery, an inverter that converts DC power supplied from the converter to AC power, A control method for a power control device, comprising: a terminal to which an output power of a power generation device is supplied when the AC power is supplied to a load and the storage battery is charged; and a control unit that controls the converter and the inverter. The control method of the power control device determines whether or not the storage battery is fully charged during a self-sustaining operation, and when the storage battery is fully charged, a DC link that is a voltage between the converter and the inverter. The voltage is reduced to a predetermined value.

  According to the power control device and the control method thereof according to the embodiment of the present invention, various distributed power sources can be efficiently controlled.

It is a figure showing the schematic structure of the power control system concerning one embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a DC link voltage waveform when the DC link voltage is not reduced. FIG. 6 is a diagram illustrating an example of a DC link voltage waveform when the DC link voltage is reduced. It is a flowchart which shows an example of the operation | movement at the time of the independent operation | movement of the electric power control apparatus which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, the "power generation device" in the claims will be described as a fuel cell, but may be other than a fuel cell. For example, the "power generation device" may be a gas generator, a gas turbine generator, a wind power generator, or the like.

[System configuration]
In FIG. 1, a solid line connecting each functional block indicates a power line, and a broken line indicates a control line and a signal line. The connection indicated by the control line and the signal line may be a wired connection or a wireless connection. In the power control device 20, illustration of the connections indicated by the control lines and the signal lines is omitted.

  The power control system 1 is installed in a customer facility. The power control system 1 is connected to a commercial power system (hereinafter abbreviated as “power system”) 100 and supplies power to a load 200 of a customer facility. The power control system 1 includes a solar cell 10, a storage battery 11, a power control device 20, a current sensor 30, a pseudo current circuit 40, a distribution board 50, and a fuel cell 60.

  The solar cell 10 generates DC power from the energy of sunlight. The solar cell 10 supplies the generated DC power to the power control device 20.

  The storage battery 11 supplies DC power to the power control device 20 by the discharged power. Further, storage battery 11 is charged by DC power supplied from power control device 20.

  The power control device 20 normally performs an interconnection operation with the power system 100. The power control device 20 supplies the power supplied from the power system 100 and the power supplied from the solar cell 10 and the storage battery 11 to the load 200 via the distribution board 50 during the interconnection operation. In addition, the power control device 20 performs an independent operation when the power system 100 loses power. The power control device 20 supplies the power supplied from the solar cell 10 and the storage battery 11 to the load 200 via the distribution board 50 during the self-sustaining operation.

  The power control device 20 charges the storage battery 11 with power supplied from the power system 100, the solar cell 10, and the fuel cell 60. Details of the configuration of the power control device 20 will be described later.

  The current sensor 30 detects a current value flowing between the power control device 20 and the distribution board 50, and transmits the detected current value to the fuel cell 60. The current sensor 30 is provided for the fuel cell 60 to control the output power. For example, depending on the contract between the customer facility and the power company (power system 100), the reverse flow of the output power of the fuel cell 60 to the power system 100 may be restricted. At this time, the fuel cell 60 controls the output power of the fuel cell 60 based on the value obtained from the current sensor 30 so that the output power of the fuel cell 60 does not flow backward. Further, when the fuel cell 60 performs the load following operation, the output power of the fuel cell 60 is controlled according to the magnitude of the forward flow detected by the current sensor 30.

  The pseudo current circuit 40 is a circuit that supplies a pseudo current in the same direction as the forward power flow to the current sensor 30 using, for example, a current supplied from the power control device 20. As described above, for example, the reverse flow of the output power of the fuel cell 60 to the power system 100 may be limited depending on the contract between the customer facility and the power company (power system 100). At this time, when the fuel cell 60 is operated during the self-sustaining operation and the storage battery 11 is to be charged with the output power of the fuel cell 60, the output power of the fuel cell 60 is detected by the current sensor 30 as a reverse power flow, and the storage battery 11 is discharged. It may not be able to charge. Therefore, in such a case, the pseudo current circuit 40 is turned on, and a pseudo current in the same direction as the forward current flows to the current sensor 30. As a result, the reverse power flow is canceled, and the storage battery 11 can be charged with the output power of the fuel cell 60.

  The distribution board 50 distributes the power supplied from the power control device 20 and the fuel cell 60 to the load 200. The load 200 is an arbitrary number of electric devices and the like, and consumes power supplied from the power control device 20 and the fuel cell 60.

  The fuel cell 60 is, for example, a solid oxide fuel cell device (SOFC: Solid Oxide Fuel Cell) or a polymer electrolyte fuel cell device (PEFC: Polymer Electrolyte Fuel Cell). The fuel cell 60 generates power by an electrochemical reaction of a fuel (for example, gas, air and reformed water mixed at a predetermined ratio). The fuel cell 60 includes an inverter and the like, and converts DC power generated by the inverter and the like into AC power. The fuel cell 60 supplies the converted AC power to the distribution board 50.

  Further, the fuel cell 60 controls the output power of the fuel cell 60 based on the value obtained from the current sensor 30 as described above. For example, when the reverse flow of the output power of the fuel cell 60 to the power system 100 is restricted, the fuel cell 60 outputs the output power of the fuel cell 60 to the power system 100 based on the value acquired from the current sensor 30. The output power of the fuel cell 60 is controlled so as to prevent power flow. Further, when the fuel cell 60 performs the load following operation, the output power of the fuel cell 60 is controlled according to the magnitude of the forward flow detected by the current sensor 30.

  Subsequently, details of the configuration of the power control device 20 will be described. The power control device 20 includes a DC / DC converter 21, a DC / DC converter (converter) 22, an inverter 23, switches SW1, SW2, SW3, an interconnection terminal 24, a terminal 25, a communication unit 26, A storage unit 27 and a control unit 28 are provided.

  DC / DC converter 21 is connected to solar cell 10. The DC / DC converter 21 converts a DC voltage supplied from the solar cell 10 into a predetermined voltage (DC link voltage) under the control of the control unit 28. The DC / DC converter 21 supplies the converted DC voltage to the inverter 23.

  DC / DC converter 22 is connected to storage battery 11. The DC / DC converter 22 converts a DC voltage supplied from the storage battery 11 into a predetermined voltage (DC link voltage) under the control of the control unit 28. The DC / DC converter 22 supplies the converted DC voltage to the inverter 23.

  The DC / DC converter 22 converts the DC voltage supplied from the inverter 23 into a predetermined voltage when charging the storage battery 11 with the power of the power system 100 or the fuel cell 60 based on the control of the control unit 28. , And supplies the converted DC voltage to the storage battery 11. In addition, the DC / DC converter 22 converts the DC voltage supplied from the DC / DC converter 21 into a predetermined voltage when charging the storage battery 11 with the power of the solar cell 10 based on the control of the control unit 28. , And supplies the converted DC voltage to the storage battery 11.

  The inverter 23 collectively converts the DC voltage supplied from the DC / DC converters 21 and 22 into an AC voltage based on the control of the control unit 28. Inverter 23 supplies the converted AC voltage to load 200 via terminal 25.

  The inverter 23 converts an AC voltage supplied from the power system 100 or the fuel cell 60 into a DC voltage when charging the storage battery 11 with the power of the power system 100 or the fuel cell 60 based on the control of the control unit 28. Then, the converted DC voltage is supplied to the DC / DC converter 22.

  The power of the power system 100 is supplied to the interconnection terminal 24 during the interconnection operation. Further, the AC power of the inverter 23 is supplied to the terminal 25 during the interconnection operation and the self-sustaining operation. Further, the output power of the fuel cell 60 is supplied to the terminal 25 when the storage battery 11 is charged.

  The switch SW1 is an interconnection switch, and is provided between the inverter 23 and the interconnection terminal 24. The switch SW1 includes a switch, a relay, and the like, and is turned on / off under the control of the control unit 28. For example, the switch SW1 is turned on during the interconnection operation. Further, for example, the switch SW1 is turned off in order to disconnect the solar cell 10 and the storage battery 11 from the power system 100 during the self-sustaining operation.

  The switch SW2 is a system bypass switch, and is provided between the interconnection terminal 24 and the terminal 25. The switch SW2 includes a switch, a relay, and the like, and is turned on / off under the control of the control unit 28. For example, the switch SW2 is turned on when supplying power from the power system 100 to the load 200 during the interconnection operation.

  The switch SW3 is a self-standing switch, and is provided between the inverter 23 and the terminal 25. The switch SW3 includes a switch, a relay, and the like, and is turned on / off under the control of the control unit 28. For example, the switch SW3 is turned off during the interconnection operation. Further, for example, the switch SW3 is turned on during the self-sustained operation to enable the power from the solar cell 10 and the storage battery 11 to be supplied to the load 200.

  The communication unit 26 communicates with a device or the like disposed outside the power control device 20. The communication unit 26 communicates with the current sensor 30 and the pseudo current circuit 40, for example.

  The storage unit 27 stores information necessary for processing of the power control device 20 and a program describing processing contents for realizing each function of the power control device 20. The storage unit 27 stores, for example, a predetermined value and a predetermined threshold described below.

  The control unit 28 controls and manages the entire power control device 20, and is, for example, a processor. The control unit 28 controls the DC / DC converters 21 and 22 and the inverter 23. The control unit 28 controls the on / off state of the switches SW1 to SW3.

  Further, when charging the storage battery 11 with the output power of the fuel cell 60, the control unit 28 controls the pseudo current circuit 40 via the communication unit 26 so that the pseudo current flows in the current sensor 30 in the same direction as the forward current. Is turned on. Further, when the storage battery 11 is fully charged, the control unit 28 turns off the pseudo current circuit 40 to stop the pseudo current. The full charge is, for example, a state in which the storage amount of the storage battery 11 has reached a preset upper limit of the usable storage amount of the storage battery 11. It should be noted that the charged amount of the storage battery 11 that is lower than a preset upper limit of the usable charged amount may be fully charged in accordance with the aging of the storage battery 11, the use temperature, and the like. The control unit 28 determines that the storage battery 11 is fully charged, for example, when the storage amount of the storage battery 11 exceeds a preset threshold.

  When the storage battery 11 is fully charged during the self-sustaining operation, the control unit 28 reduces the DC link voltage, which is the voltage of the DC link unit a between the DC / DC converters 21 and 22 and the inverter 23, to a predetermined value. Control to lower. Hereinafter, the mechanism of this control will be described.

  In the self-sustaining operation, when the fuel cell 60 is performing the load following operation and the storage battery 11 is fully charged, the output power of the fuel cell 60 has no place other than the load 200. Therefore, when the power consumption of the load 200 decreases, the fuel cell 60 consumes surplus power by the internal load in order to prevent reverse power flow. However, for example, when the power consumption of the load 200 decreases rapidly and the surplus power still occurs due to the power consumption by the internal load, the output power of the fuel cell 60 momentarily reverse flows and the DC link voltage instantaneously reverses. May go up. Further, in this case, when the DC link voltage exceeds the upper limit (for example, set as the upper limit of the guaranteed voltage value), the DC / DC converters 21 and 22 and the inverter 23 and the like stop abnormally. This situation will be described with reference to FIG. In the example of FIG. 2, the storage battery 11 is fully charged at time t1. Therefore, after time t1, the output power of the fuel cell 60 has nowhere to go except for the load 200. For this reason, at time t2, the power consumption of the load 200 sharply decreases, and the output power of the fuel cell 60 instantaneously reverse flows, so that the DC link voltage exceeds the upper limit value of 380V.

  In order to prevent this, in the present embodiment, when the storage battery 11 is fully charged during the self-sustaining operation, the DC link voltage between the DC / DC converters 21 and 22 and the inverter 23 is reduced to a predetermined value. To control. This situation will be described with reference to FIG. In the example of FIG. 3, the storage battery 11 is fully charged at time t3. Therefore, in the present embodiment, the control unit 28 reduces the DC link voltage to a predetermined value. In the example of FIG. 3, the control unit 28 continuously decreases the DC link voltage to a predetermined value of 300 V over a time T1 (between time t3 and time t4). Thus, at time t5, the output power of the fuel cell 60 instantaneously reverse flows, so that even if the DC link voltage rises momentarily, the DC link voltage does not exceed the upper limit value of 380V. Therefore, in the present embodiment, the DC / DC converters 21 and 22 and the inverter 23 do not need to be abnormally stopped during the self-sustaining operation. When the DC link voltage is reduced, the control unit 28 controls the inverter 23 to increase the corresponding voltage value.

  Furthermore, the predetermined value of 300 V and the time T1 for continuously lowering the DC link voltage to the predetermined value shown in FIG. 3 may be changed according to the power consumption of the load 200. For example, the smaller the power consumption of the load 200 is, the smaller the generated power of the fuel cell 60 is. Therefore, the power generation state of the fuel cell 60 becomes unstable, and the output power of the fuel cell 60 tends to flow backward. Therefore, in this case, the control unit 28 controls the DC link voltage to decrease faster when the power consumption of the load 200 is lower than the predetermined threshold value than when the power consumption of the load 200 is equal to or higher than the predetermined threshold value. Is also good. This control is realized by controlling the time T1 to be shorter in the example of FIG. Further, in this case, the control unit 28 may control the predetermined value to be lower when the power consumption of the load 200 is lower than the predetermined threshold than when the power consumption of the load 200 is equal to or higher than the predetermined threshold. . This control is realized by controlling the predetermined value to be lower than 300 V in the example of FIG.

  In addition, after reducing the DC link voltage when the storage battery 11 is fully charged, the control unit 28 cancels the reduction in the DC link voltage when the storage battery 11 becomes rechargeable, and reduces the reduced DC link voltage. Control is performed to return the link voltage to the original value. In the example of FIG. 3, the storage battery 11 can be charged at time t6. Therefore, at time t7, the control unit 28 returns the DC link voltage to the original value of 350V.

[System operation]
Hereinafter, the operation of the power control device 20 according to the present embodiment during the self-sustaining operation will be described with reference to FIG.

  First, the control unit 28 determines whether the storage battery 11 is fully charged (Step S101). When the control unit 28 determines that the storage battery 11 is fully charged (step S101: Yes), the process proceeds to step S102. On the other hand, when the control unit 28 determines that the storage battery 11 is not fully charged (Step S101: No), the process proceeds to Step S105.

  In the process of step S102, the control unit 28 determines whether the power consumption of the load 200 is lower than a predetermined threshold. The control unit 28 calculates the power consumption of the load 200 by multiplying the current value acquired from the current sensor 30 via the communication unit 26 by a predetermined voltage, for example. When the control unit 28 determines that the power consumption of the load 200 does not fall below the predetermined threshold value (Step S102: No), the process proceeds to Step S103. On the other hand, when determining that the power consumption of the load 200 is lower than the predetermined threshold (Step S102: Yes), the control unit 28 proceeds to the process of Step S104.

  In the process of step S103, the control unit 28 controls the DC link voltage to decrease to a predetermined value.

  By performing the processing of steps S101 to S103 in this manner, when the storage battery 11 is fully charged, the power control device 20 reduces the DC link voltage to a predetermined value. As a result, in the power control device 20, the DC link voltage exceeds the upper limit value due to the instantaneous reverse flow of the output power of the fuel cell 60, and the DC / DC converters 21 and 22 and the inverter 23 stop abnormally. Can be prevented. Therefore, according to the power control device 20, continuous operation becomes possible during the self-sustaining operation.

  In the process of step S104, the control unit 28 controls the DC link voltage to decrease to a predetermined value faster than when the DC link voltage is decreased in the process of step S103. At this time, the control unit 28 may perform control so that the predetermined value is lower than when the DC link voltage is reduced in the process of step S103.

  By performing the processing of steps S102 and S104 in this manner, when the power consumption of the load 200 is smaller than the predetermined threshold, the power control device 20 controls the DC link voltage to decrease quickly. As a result, according to the power control device 20, appropriate control of the DC link voltage according to the power consumption of the load 200 becomes possible.

  In the processing of step S105, when the DC link voltage is reduced in the processing of steps S103 and S104, the control unit 28 cancels the reduction of the DC link voltage and returns the reduced DC link voltage to the original value. Control.

  As described above, in the power control device 20 according to the present embodiment, when the storage battery 11 is fully charged during the self-sustaining operation, the DC link voltage that is the voltage between the DC / DC converters 21 and 22 and the inverter 23 is used. Is controlled to decrease to a predetermined value. As a result, in the power control device 20, the DC link voltage exceeds the upper limit value due to the instantaneous reverse flow of the output power of the fuel cell 60, and the DC / DC converters 21 and 22 and the inverter 23 stop abnormally. Can be prevented. Therefore, in the power control device 20, continuous operation becomes possible during the self-sustaining operation. Therefore, the power control device 20 can efficiently control various distributed power sources such as the fuel cell 60 and the storage battery 11.

  Although the present invention has been described with reference to the drawings and embodiments, it should be noted that those skilled in the art can easily make various changes and modifications based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions included in each component, each step, and the like can be rearranged so as not to be logically inconsistent, and a plurality of components, steps, and the like can be combined into one or divided. It is. Further, although the present invention has been described centering on the device, the present invention can be realized as a method executed by a processor included in the device, a program, or a storage medium storing the program. Should be understood to include these.

DESCRIPTION OF SYMBOLS 1 Power control system 10 Solar cell 11 Storage battery 20 Power control device 21 DC / DC converter 22 DC / DC converter (converter)
Reference Signs List 23 inverter 24 interconnection terminal 25 terminal 26 communication unit 27 storage unit 28 control unit SW1, SW2, SW3 switch 30 current sensor 40 pseudo current circuit 50 distribution board 60 fuel cell (power generation device)
100 Power system 200 Load

Claims (5)

A converter connected to the storage battery;
An inverter for converting DC power supplied from the converter to AC power,
During self-sustaining operation, a terminal to which AC power from the inverter is supplied to a load and output power of a power generator is supplied when charging the storage battery;
A control unit for controlling the converter and the inverter,
The power control device, wherein the control unit reduces a DC link voltage, which is a voltage between the converter and the inverter, to a predetermined value when the storage battery is fully charged during the self-sustaining operation. The power control device according to claim 1,
When the storage battery is fully charged and the power consumption of the load is lower than a predetermined threshold during the self-sustaining operation, the control unit may control the DC link voltage more than when the power consumption of the load is equal to or higher than a predetermined threshold. Power control device that quickly reduces the power to a predetermined value. The power control device according to claim 1 or 2,
The control unit, when the self-sustaining operation, the storage battery is fully charged, and when the power consumption of the load is less than a predetermined threshold, than when the power consumption of the load is equal to or more than a predetermined threshold, Power control device to lower. The power control device according to any one of claims 1 to 3,
When the storage battery is fully charged, the control unit lowers the DC link voltage when the storage battery is fully charged, and then reduces the DC link voltage to the original value when the storage battery becomes chargeable. Return to the power control device. A converter connected to the storage battery;
An inverter for converting DC power supplied from the converter to AC power,
During self-sustaining operation, a terminal to which AC power from the inverter is supplied to a load and output power of a power generator is supplied when charging the storage battery;
A control unit for controlling the converter and the inverter, and a control method of a power control device including:
During autonomous operation, determine whether the storage battery is fully charged,
When the storage battery is fully charged, a control method of a power control device that reduces a DC link voltage, which is a voltage between the converter and the inverter, to a predetermined value.

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