JP2018019506A - Power control device and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently control various distributed power supplies.SOLUTION: A power control device comprises: a converter connected with an accumulator battery; an inverter that converts a DC power supplied from the converter into an AC power; a terminal that supplies to a load the AC power from the inverter at an autonomous operation and that is supplied with an output power of a power generation device when the accumulator battery is charged; and a controller that controls the converter and the inverter. The controller reduces a DC link voltage that is a voltage between the converter and the inverter to a predetermined value at the autonomous operation in a case where the accumulator battery is fully charged.SELECTED DRAWING: Figure 1

Description

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

  In recent years, it has become widespread to install distributed power sources in customer facilities. In addition, with the diversification of distributed power sources, various distributed power sources such as solar cells, storage batteries, fuel cells, gas generators, and the like may be installed in customer facilities. In this case, it is required to efficiently control various distributed power sources in the customer facility. Therefore, a power control apparatus 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 apparatus and a control method thereof capable of efficiently controlling various distributed power sources.

  A power control apparatus according to an 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 independent operation. And a control unit that controls the converter and the inverter. The terminal is supplied with output power when the storage battery is charged. 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 independent operation.

  Moreover, the control method of the power control device according to an 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, It is a control method of a power control apparatus provided with the terminal which supplies the output power of a power generator when supplying the alternating current power of a load to the load, and charging the storage battery, and the control part which controls the converter and the inverter. The control method of the power control apparatus determines whether or not the storage battery is fully charged during self-sustained 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 controlled efficiently.

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

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following description, the “power generation device” in the claims is 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 connections indicated by control lines and 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 sunlight energy. The solar cell 10 supplies the generated DC power to the power control device 20.

  The storage battery 11 supplies direct-current power to the power control apparatus 20 by discharged power. In addition, the storage battery 11 is charged with DC power supplied from the power control device 20.

  The power control device 20 performs a linked operation with the power system 100 during normal times. 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 grid operation. In addition, the power control device 20 performs a self-sustained operation when the power system 100 is powered down. The power control device 20 supplies 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.

  In addition, 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 apparatus 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 contents of 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 acquired 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 current to the current sensor 30 using, for example, a current supplied from the power control device 20. As described above, for example, the reverse power flow of the output power of the fuel cell 60 to the power system 100 may be limited depending on the contract contents between the customer facility and the power company (power system 100). At this time, if the fuel cell 60 is operated during the self-sustained operation and the storage battery 11 is charged by the output power of the fuel cell 60, the output power of the fuel cell 60 is detected as a reverse power flow by the current sensor 30, and the storage battery 11 is You 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 flow is supplied to the current sensor 30. Thereby, the reverse power flow is canceled and the storage battery 11 can be charged by 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) or a polymer electrolyte fuel cell (PEFC). The fuel cell 60 generates power by an electrochemical reaction of fuel (for example, gas, air, and reformed water blended at a predetermined ratio). The fuel cell 60 includes an inverter or the like, and converts the generated DC power into AC power by the inverter or the like. 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 acquired 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 uses the value acquired from the current sensor 30 to reverse the output power of the fuel cell 60 to the power system 100. The output power of the fuel cell 60 is controlled so as not to 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.

  Next, details of the configuration of the power control apparatus 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, and SW3, a connection terminal 24, a terminal 25, a communication unit 26, A storage unit 27 and a control unit 28 are provided.

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

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

  Further, 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 electric 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 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 battery 10 based on the control of the control unit 28. Then, the converted DC voltage is supplied 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. The inverter 23 supplies the converted AC voltage to the load 200 via the terminal 25.

  Further, the inverter 23 converts the 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 independent operation. Further, when the storage battery 11 is charged, the output power of the fuel cell 60 is supplied to the terminal 25.

  The switch SW <b> 1 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 based on the control of the control unit 28. For example, the switch SW1 is turned on during the interconnection operation. Further, for example, the switch SW <b> 1 is turned off in order to disconnect the solar battery 10 and the storage battery 11 from the power system 100 during the independent 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 based on the control of the control unit 28. For example, the switch SW2 is turned on when power from the power system 100 is supplied to the load 200 during the grid operation.

  The switch SW3 is a self-supporting 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 based on the control of the control unit 28. For example, the switch SW3 is turned off during the interconnected operation. Further, for example, the switch SW3 is turned on in order to enable the power from the solar cell 10 and the storage battery 11 to be supplied to the load 200 during the independent operation.

  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 a program describing information necessary for processing of the power control device 20 and 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 later.

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

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

  Further, when the storage battery 11 is fully charged during the self-sustained operation, the control unit 28 sets 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.

  When the fuel cell 60 is performing the load following operation during the self-supporting 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 surplus power is still generated due to the power consumption by the internal load, the output power of the fuel cell 60 instantaneously reversely flows and the DC link voltage instantaneously May go up. Further, in this case, when the DC link voltage exceeds an upper limit value (for example, set as an upper limit of the guaranteed voltage value), the DC / DC converters 21 and 22 and the inverter 23 are abnormally stopped. This 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 no place other than the load 200. For this reason, at time t2, the power consumption of the load 200 rapidly decreases, and the output power of the fuel cell 60 instantaneously reversely flows, so that the DC link voltage exceeds the upper limit value of 380V.

  In order to prevent this, in this embodiment, when the storage battery 11 is fully charged during the self-sustained operation, the DC link voltage between the DC / DC converters 21 and 22 and the inverter 23 is decreased to a predetermined value. To control. This 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 this 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 time T1 (between time t3 and time t4). As a result, the output power of the fuel cell 60 instantaneously reversely flows at time t5, so even if the DC link voltage rises momentarily, the DC link voltage does not exceed the upper limit value of 380V. Therefore, in this embodiment, it is not necessary to abnormally stop the DC / DC converters 21 and 22 and the inverter 23 during the self-sustaining operation. Note that when the DC link voltage is lowered, the control unit 28 controls the inverter 23 to boost the voltage value by that amount.

  Furthermore, the time T1 required for continuously reducing the predetermined value of 300V and the DC link voltage shown in FIG. 3 to the predetermined value may be changed according to the power consumption of the load 200. For example, as the power consumption of the load 200 is smaller, it is necessary to reduce the generated power of the fuel cell 60. Therefore, the power generation state in the fuel cell 60 becomes unstable, and the output power of the fuel cell 60 tends to flow backward. Therefore, in this case, when the power consumption of the load 200 is lower than the predetermined threshold, the control unit 28 performs control so that the DC link voltage is decreased faster than when the power consumption of the load 200 is equal to or higher than the predetermined threshold. Also good. In the example of FIG. 3, this control is realized by performing control so as to shorten the time T1. 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 value than when the power consumption of the load 200 is equal to or higher than the predetermined threshold value. . In the example of FIG. 3, this control is realized by controlling the predetermined value to be lower than 300V.

  In addition, when the storage battery 11 is fully charged, the control unit 28 cancels the decrease in the DC link voltage when the storage battery 11 can be charged after the DC link voltage is reduced. Control 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, the DC link voltage is returned to the original value of 350 V by the control unit 28 at time t7.

[System operation]
Hereinafter, the operation | movement at the time of the independent operation of the power control apparatus 20 which concerns on this embodiment is demonstrated using FIG.

  First, the control unit 28 determines whether or not the storage battery 11 is fully charged (step S101). When it determines with the storage battery 11 being fully charged (step S101: Yes), the control part 28 progresses to the process of step S102. On the other hand, when it determines with the storage battery 11 not being fully charged (step S101: No), the control part 28 progresses to the process of step S105.

  In the process of step S102, the control unit 28 determines whether the power consumption of the load 200 is below a predetermined threshold value. For example, the control unit 28 multiplies the current value acquired from the current sensor 30 via the communication unit 26 by a predetermined voltage to calculate the power consumption of the load 200. When the control unit 28 determines that the power consumption of the load 200 does not fall below the predetermined threshold (step S102: No), the control unit 28 proceeds to the process of step S103. On the other hand, when it determines with the power consumption of the load 200 falling below a predetermined threshold value (step S102: Yes), the control part 28 progresses to the process of step S104.

  In the process of step S103, the control unit 28 performs control so that the DC link voltage is reduced to a predetermined value.

  As described above, when the storage battery 11 is fully charged by performing the processes of steps S101 to S103, the power control device 20 reduces the DC link voltage to a predetermined value. As a result, in the power control apparatus 20, the DC link voltage exceeds the upper limit due to the instantaneous reverse flow of the output power of the fuel cell 60, and the DC / DC converters 21, 22 and the inverter 23 are abnormally stopped. Can be prevented. Therefore, according to the power control device 20, continuous operation is possible during the independent operation.

  In the process of step S104, the control unit 28 controls the DC link voltage to be decreased 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 control the predetermined value to be lower than when the DC link voltage is decreased in the process of step S103.

  By performing the processing of steps S102 and S104 in this way, when the power consumption of the load 200 is smaller than the predetermined threshold, the power control device 20 is controlled so that the DC link voltage decreases quickly. Thereby, according to the power control device 20, it is possible to appropriately control the DC link voltage according to the power consumption of the load 200.

  In the process of step S105, when the DC link voltage is decreased in the processes of steps S103 and S104, the control unit 28 cancels the decrease in the DC link voltage and returns the decreased DC link voltage to the original value. To control.

  As described above, in the power control device 20 according to the present embodiment, the DC link voltage that is the voltage between the DC / DC converters 21 and 22 and the inverter 23 when the storage battery 11 is fully charged during the independent operation. Is controlled to decrease to a predetermined value. As a result, in the power control apparatus 20, the DC link voltage exceeds the upper limit due to the instantaneous reverse flow of the output power of the fuel cell 60, and the DC / DC converters 21, 22 and the inverter 23 are abnormally stopped. Can be prevented. Therefore, the power control device 20 can be continuously operated during the independent 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 based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections 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, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and multiple components, steps, etc. can be combined or divided into one It is. Further, although the present invention has been described mainly with respect to the apparatus, the present invention can also be realized as a method, a program executed by a processor included in the apparatus, or a storage medium storing the program, and is within the scope of the present invention. It should be understood that these are also included.

DESCRIPTION OF SYMBOLS 1 Power control system 10 Solar cell 11 Storage battery 20 Power control apparatus 21 DC / DC converter 22 DC / DC converter (converter)
DESCRIPTION OF SYMBOLS 23 Inverter 24 Connection terminal 25 Terminal 26 Communication part 27 Memory | storage part 28 Control part 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 that converts DC power supplied from the converter into AC power;
At the time of self-sustained operation, a terminal to which the AC power from the inverter is supplied to the load and the output power of the power generator is supplied when charging the storage battery,
A controller for controlling the converter and the inverter,
The said control part is an electric power control apparatus which reduces the DC link voltage which is a voltage between the said converter and the said inverter to a predetermined value, when the said storage battery is a full charge at the time of self-sustained operation. The power control apparatus according to claim 1,
When the storage unit is fully charged and the power consumption of the load is lower than a predetermined threshold during self-sustained operation, the control unit is more likely to have the DC link voltage than the case where the power consumption of the load is equal to or higher than the predetermined threshold. A power control device that quickly reduces the power to a predetermined value. The power control apparatus according to claim 1 or 2,
When the storage battery is fully charged and the power consumption of the load is lower than a predetermined threshold during the self-sustained operation, the control unit sets the predetermined value more than the case where the power consumption of the load is equal to or higher than the predetermined threshold. Low power control device. In the power control device according to any one of claims 1 to 3,
In the self-sustained operation, the control unit reduces 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 that converts DC power supplied from the converter into AC power;
At the time of self-sustained operation, a terminal to which the AC power from the inverter is supplied to the load and the output power of the 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 comprising:
During independent operation, determine whether the storage battery is fully charged,
When the storage battery is fully charged, the control method of the power control apparatus that reduces a DC link voltage, which is a voltage between the converter and the inverter, to a predetermined value.

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