Power conversion device and power conversion method

Abstract

To enable an inverter for a solar cell to be used for discharging a secondary battery including a storage battery provided in an electric vehicle.SOLUTION: A power conversion device 1 is provided between a secondary battery 2 and an inverter 3 corresponding to the power supplied from a current source, and includes an acquisition unit 142 that acquires characteristic information indicating the current-voltage characteristics corresponding to the inverter 3, a voltage identification unit 143 that identifies the operating voltage set by the inverter 3, which is the voltage to be output from the power conversion device 1, a setting unit 144 that sets the current corresponding to the identified operating voltage based on the current-voltage characteristics indicated by the acquired characteristic information, to an output current to be output from the power conversion device 1, and a conversion unit 15 that converts the power output from the secondary battery 2 into power corresponding to the output current set by the setting unit 144 and the identified operating voltage, and outputs the power to the inverter 3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power conversion device and a power conversion method. [Background technology]

[0002] BACKGROUND ART Conventionally, a dedicated device has been proposed for realizing V2H (Vehicle to Home) in which power is supplied to a load in a home from a secondary battery provided in an electric vehicle (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-134318 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional devices have the problem of being expensive because they are dedicated to V2H. For this reason, it is desirable to use existing inverters to discharge electricity from secondary batteries installed in electric vehicles instead of dedicated V2H devices. Existing inverters include inverters for secondary batteries and inverters for solar cells.

[0005] In order to discharge a secondary battery installed in an electric vehicle using a secondary battery inverter, the inverter must be compatible with the output voltage of the secondary battery and the communication protocol of the secondary battery, which limits the types of secondary battery inverters that can be used to discharge electric vehicles.

[0006] On the other hand, inverters for solar cells do not have the same limitations as inverters for secondary batteries. However, inverters for solar cells are designed to correspond to the output power characteristics of solar cells, which are characteristics as a current source. In contrast, secondary batteries in electric vehicles function as voltage sources, and their output power characteristics are significantly different from those of solar cells, so there was a problem that inverters for solar cells could not be used directly for discharging electric vehicles.

[0007] The present invention has been made in consideration of these points, and aims to make it possible to use an inverter for a solar cell to discharge a secondary battery, including a storage battery, installed in an electric vehicle. [Means for solving the problem]

[0008] A power conversion device according to a first aspect of the present invention is a power conversion device provided between a secondary battery and an inverter corresponding to power supplied from a current source, and includes: an acquisition unit that acquires characteristic information indicating current-voltage characteristics corresponding to the inverter; a voltage identification unit that identifies an operating voltage set by the inverter, which is a voltage to be output from the power conversion device; a setting unit that sets a current corresponding to the operating voltage identified by the voltage identification unit to an output current to be output from the power conversion device based on the current-voltage characteristics indicated by the characteristic information acquired by the acquisition unit; and a conversion unit that converts the power output from the secondary battery into power corresponding to the output current set by the setting unit and the operating voltage identified by the voltage identification unit, and outputs the power to the inverter.

[0009] The power conversion device may further have a power identification unit that identifies a target power, which is a target value of the power to be output from the power conversion device, and the acquisition unit may acquire the characteristic information that indicates the current-voltage characteristic corresponding to the target power identified by the power identification unit.

[0010] The power conversion device may further include a memory unit that stores generation information for generating the characteristic information corresponding to each of a plurality of powers that can be output from the power conversion device, and the acquisition unit may identify the target operating voltage corresponding to the target power identified by the power identification unit as a power-voltage characteristic that indicates the relationship between power and voltage, wherein the power at a maximum power point in the power-voltage characteristic is the target power, and may acquire the characteristic information that indicates the current-voltage characteristic where the output power at the maximum power point matches the target power based on the identified target operating voltage, a target operating current that is a current corresponding to the target power and the target operating voltage, and the generation information stored in the memory unit.

[0011] The acquisition unit may acquire characteristic information corresponding to the changed target power in response to a change in the target power identified by the power identification unit, and the setting unit may change the output current in response to a change in the target power identified by the power identification unit based on the characteristic information corresponding to the changed target power acquired by the acquisition unit and the operating voltage identified by the voltage identification unit.

[0012] The acquisition unit may acquire, as the current-voltage characteristics corresponding to the inverter, characteristic information indicating current-voltage characteristics corresponding to a solar cell serving as a predetermined current source.

[0013] The current-voltage characteristic may be a current-voltage characteristic set based on the maximum current and maximum voltage that the solar cell can output when the solar cell outputs the target power, a target operating voltage that is the voltage of the maximum power point in the power-voltage characteristic where the power of the maximum power point becomes the target power, and a target operating current corresponding to the target power and the target operating voltage.

[0014] After identifying the target operating voltage corresponding to the target power, the acquisition unit may identify a convergence value of the operating voltage based on the multiple operating voltages identified by the voltage identification unit at multiple times for the target power, update the target operating voltage to the convergence value, and acquire the characteristic information based on the updated target operating voltage, the target operating current corresponding to the target power and the updated target operating voltage, and generation information stored in the memory unit.

[0015] A power conversion method according to a second aspect of the present invention is performed by a power conversion device that is provided between a secondary battery and an inverter corresponding to the power supplied from a current source and has a conversion unit that converts power, and includes the steps of acquiring characteristic information indicating current-voltage characteristics corresponding to the inverter, identifying an operating voltage that is set by the inverter and is the voltage to be output from the power conversion device, setting a current corresponding to the identified operating voltage as the output current to be output from the power conversion device based on the current-voltage characteristics indicated by the acquired characteristic information, and causing the conversion unit to convert the power output from the secondary battery into power corresponding to the set output current and the identified operating voltage. [Effects of the Invention]

[0016] According to the present invention, an inverter for a solar cell can be used to discharge a secondary battery including a storage battery provided in an electric vehicle. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating an outline of a power conversion device according to a first embodiment. [Figure 2] 1 is a diagram illustrating a functional configuration of a power conversion device according to a first embodiment. [Figure 3] 3 is a diagram showing power-voltage characteristics showing the relationship between the power and voltage output by the power conversion device; FIG. [Figure 4] 10 is a diagram illustrating an example of current-voltage characteristics indicated by characteristic information generated by an acquisition unit. FIG. [Figure 5] 4 is a flowchart illustrating an example of a processing flow in a power conversion device. [Figure 6] FIG. 10 is a diagram illustrating an outline of a power conversion device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] First Embodiment [Outline of power conversion device 1] 1 is a diagram illustrating an overview of a power conversion device 1 according to a first embodiment. The power conversion device 1 is a device that converts power and is provided between a secondary battery 2 and an inverter 3 provided in an electric vehicle EV.

[0019] The secondary battery 2 provided in the electric vehicle EV is a storage battery that can be electrically connected to a battery ECU (Electronic Control Unit) provided in the electric vehicle EV via a connector dedicated to electric vehicles, and can be charged and discharged in accordance with the charging and discharging standard for electric vehicles. The charging and discharging standard will be described as being, for example, the CHAdeMO protocol, but the charging standard is not limited to this and may be another charging and discharging standard for electric vehicles. The secondary battery 2 functions as a voltage source and supplies power to the power conversion device 1 connected to it. Hereinafter, the secondary battery 2 provided in the electric vehicle EV will be simply referred to as the secondary battery 2.

[0020] The inverter 3 is a DC / AC inverter that corresponds to the power supplied from a current source. The inverter 3 is, for example, an inverter for a solar cell designed in accordance with the output power characteristics of the solar cell, and performs maximum power point tracking control. The inverter 3 is connected to the power conversion device 1 and receives power from the power conversion device 1. As described above, the secondary battery 2 functions as a voltage source and has significantly different output power characteristics from the solar cell. This poses a problem in that the inverter 3 cannot be used as is for discharging power from the secondary battery 2.

[0021] In response to this, the power conversion device 1 identifies the operating voltage set by the inverter 3, which is the voltage to be output from the power conversion device 1, and sets a current corresponding to the operating voltage as the output current to be output from the power conversion device 1 based on the current-voltage characteristics corresponding to the inverter 3. Then, the power conversion device 1 converts the power output from the secondary battery 2 into power corresponding to the set output current and the identified operating voltage, and outputs it to the inverter 3.

[0022] In this way, the power conversion device 1 can convert the power output from the secondary battery 2 into power corresponding to the current-voltage characteristics of the solar cell, in accordance with the operating voltage set by the inverter 3 performing maximum power point tracking control, and output the converted power. The solar cell inverter 3 can be used to discharge secondary batteries, including storage batteries, provided in electric vehicles EV.

[0023] [Configuration of power conversion device 1] Next, a description will be given of the configuration of the power conversion device 1. Fig. 2 is a diagram showing the functional configuration of the power conversion device 1 according to the first embodiment. As shown in Fig. 2, the power conversion device 1 has a communication unit 11, a voltmeter 12, a storage unit 13, a control unit 14, and a conversion unit 15.

[0024] The communication unit 11 is an interface for the power conversion device 1 to communicate with a communication device (not shown) provided in the distribution board 4. The voltmeter 12 measures the voltage at a terminal (not shown) of the power conversion device 1 to which the inverter 3 is connected as an operating voltage, which is a voltage set by the inverter 3 and output from the power conversion device 1. The voltmeter 12 outputs voltage information indicating the measured operating voltage to the control unit 14.

[0025] The storage unit 13 is, for example, a random access memory (RAM) or a read only memory (ROM). The storage unit 13 stores programs that cause the control unit 14 to function as a power specifying unit 141, an acquisition unit 142, a voltage specifying unit 143, and a setting unit 144.

[0026] Furthermore, the storage unit 13 stores generation information for generating characteristic information indicating current-voltage characteristics corresponding to each of a plurality of powers that can be output from the power conversion device 1, the characteristic information indicating current-voltage characteristics corresponding to the inverter 3. For example, the generation information is a program for calculating a function simulating the characteristics of a solar cell that passes through a target operating current and a target operating voltage corresponding to a target power that is a target value for the power output by the power conversion device 1, and that maximizes the power at the target operating current and the target operating voltage. The function simulating the characteristics of a solar cell is, for example, an exponential function, but is not limited to this and may be another function, such as a function that expresses the characteristics of a solar cell with a plurality of straight lines.

[0027] The control unit 14 is, for example, a microprocessor. The control unit 14 executes a program stored in the storage unit 13 to function as a power specifying unit 141, an acquisition unit 142, a voltage specifying unit 143, and a setting unit 144.

[0028] The power specifying unit 141 specifies target power, which is a target value of power to be output from the power conversion device 1. For example, the power specifying unit 141 receives, via the communication unit 11, supply power information indicating the supply power measured at the power receiving point and supplied to the load 6 from the power system 5, from a communication device provided in the distribution board 4. Then, the power specifying unit 141 specifies the supply power indicated by the supply power information as the target power. In other words, the power specifying unit 141 specifies the target power so that the supply power at the power receiving point becomes zero.

[0029] The acquiring unit 142 acquires characteristic information indicating the current-voltage characteristics corresponding to the solar cell as the predetermined current source as the current-voltage characteristics corresponding to the inverter 3. Specifically, the acquiring unit 142 acquires characteristic information indicating the current-voltage characteristics corresponding to the target power identified by the power identifying unit 141.

[0030] More specifically, the acquisition unit 142 identifies the target operating voltage corresponding to the target power identified by the power identifying unit 141 as a voltage that matches the voltage at the maximum power point in a power-voltage characteristic that indicates the relationship between power and voltage, where the power at the maximum power point is the target power. For example, the storage unit 13 stores information indicating the target operating voltage corresponding to the target power identified by the power identifying unit 141, and the acquisition unit 142 identifies the target operating voltage by referring to the storage unit 13. The target operating voltage is assumed to be common to each of the multiple target powers, but is not limited to this and may be different for each of the multiple target powers. The acquisition unit 142 then identifies a target operating current, which is a current corresponding to the target power and the target operating voltage. The acquisition unit 142 identifies the target operating current by dividing the target power by the target operating voltage.

[0031] 3 is a diagram showing power-voltage characteristics indicating the relationship between the power and voltage output by the power conversion device 1. The example shown in FIG. 3 shows power-voltage characteristics in which the power at the maximum power point varies. For example, when the target power identified by the power identifying unit 141 is Pmp, the acquiring unit 142 identifies the voltage corresponding to the maximum power point on the characteristic curve C, which indicates a power-voltage characteristic in which the power at the maximum power point is equal to the target power Pmp, as the target operating voltage Vmp. Furthermore, the acquiring unit 142 identifies the target operating current Imp as Pmp / Vmp.

[0032] Acquiring unit 142 acquires characteristic information indicating the current-voltage characteristics corresponding to the target power by generating characteristic information indicating the current-voltage characteristics whereby the output power at the maximum power point coincides with the target power, based on the identified target operating voltage, target operating current, and generation information stored in memory unit 13. Acquiring unit 142 generates, as characteristic information, a function that passes through the output current Isc in a short-circuit state and the output voltage Vop in an open state and indicates the current-voltage characteristics whereby the output power at the maximum power point coincides with the target power, based on the target operating voltage, target operating current, and generation information.

[0033] That is, the current-voltage characteristic is set based on the maximum current (output current Isc in a short-circuit state) and maximum voltage (output voltage Vop in an open state) that the solar cell can output when the solar cell outputs the target power, the target operating voltage Vmp, which is the voltage of the maximum power point in the power-voltage characteristic where the power of the maximum power point is the target power Pmp, and the target operating current Imp corresponding to the target power Pmp and the target operating voltage Vmp.

[0034] Fig. 4 is a diagram showing an example of the current-voltage characteristics indicated by the characteristic information generated by the acquisition unit 142. From Fig. 3 and Fig. 4, it can be seen that when the voltage is the target operating voltage Vmp and the current is the target operating current Imp, the target power Pmp is reached, which is the maximum power point in the power-voltage characteristics.

[0035] Furthermore, in response to a change in the target power identified by power identifying unit 141, acquiring unit 142 acquires characteristic information corresponding to the changed target power. For example, in response to a change in the target power, acquiring unit 142 identifies a target operating voltage corresponding to the changed target power as a voltage that matches the voltage of the maximum power point in the power-voltage characteristics, and identifies a target current based on the target power and the target operating voltage. Then, acquiring unit 142 generates characteristic information based on the target operating voltage corresponding to the changed target power, the target operating current, and the generation information.

[0036] The voltage identifying unit 143 identifies the operating voltage, which is the voltage set by the inverter 3 and output from the power conversion device 1. For example, the voltage identifying unit 143 identifies the operating voltage by acquiring voltage information indicating the operating voltage measured by the voltmeter 12.

[0037] Based on the current-voltage characteristics indicated by the characteristic information acquired by the acquisition unit 142, the setting unit 144 sets the current corresponding to the operating voltage identified by the voltage identification unit 143 as the output current to be output from the power conversion device 1. For example, by inputting the operating power into a function as the characteristic information, the setting unit 144 sets the value obtained from the function as the current value of the output current to be output from the power conversion device 1.

[0038] Furthermore, in response to a change in the target power identified by the power identifying unit 141, the setting unit 144 changes the output current based on the characteristic information corresponding to the changed target power acquired by the acquiring unit 142 and the operating voltage identified by the voltage identifying unit 143. As a result, the setting unit 144 causes the conversion unit 15 to convert the power output from the secondary battery 2 into power corresponding to the output current set by the setting unit 144 itself and the operating voltage identified by the voltage identifying unit 143.

[0039] The conversion unit 15 is, for example, a conversion circuit connected to the secondary battery 2 and the inverter 3, and converts the power output from the secondary battery 2. The conversion unit 15 converts the power output from the secondary battery 2 into power corresponding to the output current set by the setting unit 144 and the operating voltage identified by the voltage identification unit 143, and outputs the converted power to the inverter 3.

[0040] [Operation flow] Next, we will explain the flow of processing in the power conversion device 1. Fig. 5 is a flowchart showing an example of the flow of processing in the power conversion device 1. For example, the power conversion device 1 is provided with a switch (not shown) that switches whether to start or stop the power conversion device 1, and when the switch is operated to start the power conversion device 1, the flowchart shown in Fig. 5 is assumed to start.

[0041] First, the power specifying unit 141 specifies a target power, which is a target value of the power to be output from the power electronics device 1 (S1). Next, acquisition unit 142 identifies a target operating voltage corresponding to the latest target power identified by power identification unit 141 (S2). Next, acquisition unit 142 identifies a target operating current based on the target power and target operating voltage (S3). Acquisition unit 142 acquires characteristic information indicating the current-voltage characteristic corresponding to the latest target power identified by power identification unit 141 based on the identified target operating voltage, target operating current, and generation information stored in storage unit 13 (S4).

[0042] Next, the voltage specifying unit 143 specifies the operating voltage set by the inverter 3 (S5). Next, the setting unit 144 sets the current corresponding to the operating voltage identified by the voltage identification unit 143 as the output current to be output from the power conversion device 1 based on the current-voltage characteristics indicated by the characteristic information acquired by the acquisition unit 142 in S4 (S6).

[0043] Next, the conversion unit 15 converts the power output from the secondary battery 2 into power corresponding to the output current set by the setting unit 144 and the operating voltage identified by the voltage identification unit 143, and outputs it to the inverter 3 (S7).

[0044] Next, the control unit 14 determines whether to terminate the operation of the power conversion device 1 (S8). For example, when an operation to terminate the shutdown of the power conversion device 1 is performed using a switch provided in the power conversion device 1 that switches between starting and stopping the power conversion device 1, the control unit 14 determines to terminate the operation of the power conversion device 1 (YES in S8) and terminates the processing related to this flowchart. When the control unit 14 determines not to terminate the operation of the power conversion device 1 (NO in S8), the processing proceeds to S9.

[0045] Next, the power specifying unit 141 specifies the target power (S9). Next, the acquisition unit 142 determines whether the target power newly determined by the power determination unit 141 has changed from the previously determined target power (S10). If the acquisition unit 142 determines that the target power has changed (YES in S10), the process proceeds to S3, where the acquisition unit 142 determines the target operating current corresponding to the changed target power. On the other hand, if the acquisition unit 142 determines that the target power has not changed (NO in S10), the process proceeds to S5.

[0046] <Effects of the First Embodiment> As described above, the power conversion device 1 according to the first embodiment identifies the operating voltage set by the inverter 3, which is the voltage to be output from the power conversion device 1, acquires characteristic information indicating the current-voltage characteristics corresponding to the inverter 3, and sets the current corresponding to the identified operating voltage as the output current to be output from the power conversion device 1 based on the current-voltage characteristics indicated by the characteristic information. Then, the power conversion device 1 converts the power output from the secondary battery 2 into power corresponding to the set output current and the identified operating voltage, and outputs the power to the inverter 3. In this way, the power conversion device 1 can use the solar cell inverter 3 to discharge secondary batteries, including storage batteries, provided in electric vehicles.

[0047] <Second embodiment> Next, a second embodiment will be described. Fig. 6 is a diagram illustrating an overview of a power conversion device 1 according to the second embodiment. As shown in Fig. 6, when a solar cell 7 is connected to the inverter 3 in addition to the power conversion device 1, the inverter 3 also performs maximum power point tracking control on the solar cell 7. When the inverter 3 is a type of inverter that determines the operating voltage by adding up the output powers of the multiple solar cells 7 connected to it, the operating voltage set by the inverter 3 for the power conversion device 1 is set based on the operating voltage of the solar cell 7, and this may result in the operating voltage converging to an operating voltage different from the voltage corresponding to the maximum power point indicated by the current-voltage characteristic indicated by the characteristic information acquired by the acquisition unit 142.

[0048] In contrast, the power conversion device 1 differs from the first embodiment in that it corrects the characteristic information so that the maximum power point becomes the operating voltage corresponding to the solar cell 7 connected to the inverter 3. The power conversion device 1 according to the second embodiment will be described below. Note that the description of the same parts as those in the first embodiment will be omitted as appropriate.

[0049] Acquiring unit 142 according to the second embodiment identifies a target operating voltage corresponding to the target power identified by power identifying unit 141, and then identifies a convergence value of the operating voltage based on multiple operating voltages identified at multiple times by voltage identifying unit 143 for the target power. For example, acquiring unit 142 identifies the operating voltage that appears most frequently among the multiple operating voltages identified at multiple times by voltage identifying unit 143 as the convergence value of the operating voltage.

[0050] Acquisition unit 142 updates the target operating voltage to the specified convergence value and specifies a target operating current corresponding to the updated target operating voltage and target power. Acquisition unit 142 acquires characteristic information based on the updated target operating voltage, the specified target operating current, and the generation information stored in storage unit 13. Acquisition unit 142 may update the target operating voltage stored in storage unit 13 to the updated target operating voltage. In this way, power conversion device 1 can adjust the target operating voltage corresponding to the maximum power point in accordance with fluctuations in the operating voltage of solar cell 7 connected to inverter 3, and can operate in coordination with solar cell 7 based on the current-voltage characteristic corresponding to the target operating voltage.

[0051] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0052] 1 Power conversion device 11 Communications Department 12 Voltmeter 13 Storage section 14 Control Unit 15 Conversion unit 141 Electricity Specification Department 142 Acquisition Department 143 Voltage identification part 144 Settings 2 Secondary battery 3 inverters 4 Distribution board 5 Power system 6 Load 7. Solar Cells

Claims

1. A power conversion device provided between a secondary battery and an inverter that corresponds to power supplied from a current source, an acquisition unit that acquires characteristic information indicating current-voltage characteristics corresponding to the inverter; a voltage specifying unit that specifies an operating voltage set by the inverter, the operating voltage being a voltage output from the power conversion device; a setting unit that sets a current corresponding to the operating voltage identified by the voltage identifying unit to an output current to be output from the power conversion device based on the current-voltage characteristic indicated by the characteristic information acquired by the acquiring unit; a conversion unit that converts the power output from the secondary battery into power corresponding to the output current set by the setting unit and the operating voltage specified by the voltage specifying unit, and outputs the power to the inverter; A power conversion device having:

2. a power specifying unit that specifies a target power that is a target value of power to be output from the power conversion device; the acquiring unit acquires the characteristic information indicating the current-voltage characteristic corresponding to the target power identified by the power identifying unit. The power conversion device according to claim 1 .

3. a storage unit configured to store generation information for generating the characteristic information corresponding to each of a plurality of powers that can be output from the power conversion device; the acquisition unit acquires the characteristic information indicating the current-voltage characteristic corresponding to the target power by generating characteristic information indicating the current-voltage characteristic in which the output power at the maximum power point coincides with the target power based on the specified target operating voltage, a target operating current which is a current corresponding to the target power and the target operating voltage, and information for generation stored in the storage unit; The power conversion device according to claim 2 .

4. the acquiring unit acquires characteristic information corresponding to the changed target power in response to a change in the target power identified by the power identifying unit; the setting unit changes the output current based on the characteristic information corresponding to the changed target power acquired by the acquisition unit and the operating voltage identified by the voltage identifying unit, in response to a change in the target power identified by the power identifying unit. The power conversion device according to claim 2 .

5. the acquisition unit acquires characteristic information indicating a current-voltage characteristic corresponding to a solar cell as a predetermined current source as the current-voltage characteristic corresponding to the inverter. The power conversion device according to claim 2 .

6. the current-voltage characteristics are current-voltage characteristics set based on a maximum current and a maximum voltage that can be output by the solar cell when the solar cell outputs the target power, a target operating voltage that is the voltage of the maximum power point in a power-voltage characteristic in which the power of the maximum power point becomes the target power, and a target operating current corresponding to the target power and the target operating voltage. The power conversion device according to claim 5 .

7. the acquisition unit identifies the target operating voltage corresponding to the target power, then identifies a convergence value of the operating voltage based on the multiple operating voltages identified at multiple times by the voltage identification unit for the target power, updates the target operating voltage to the convergence value, and acquires the characteristic information based on the updated target operating voltage, the target operating current corresponding to the target power and the updated target operating voltage, and information for generation stored in the storage unit. The power conversion device according to claim 3 .

8. a power conversion device provided between the secondary battery and an inverter that converts power from a current source, the power conversion device having a conversion unit that converts power; acquiring characteristic information indicating current-voltage characteristics corresponding to the inverter; Identifying an operating voltage set by the inverter, which is a voltage output from the power conversion device; setting a current corresponding to the specified operating voltage as an output current to be output from the power conversion device based on the current-voltage characteristic indicated by the acquired characteristic information; causing the conversion unit to convert the power output from the secondary battery into power corresponding to the set output current and the specified operating voltage; A power conversion method comprising:

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