Control device, power control system, control method, and program

Abstract

This control device carries out connection control in a power distribution network in which a solar cell and a plurality of loads are connected and power from the solar cell is distributed in direct current, wherein the control device comprises: an information acquiring unit that acquires information via the power distribution network from a load connected to the solar cell; and a control unit that, on the basis of load-side power and solar-cell-side voltage obtained from the information, selects a load to be connected to the solar cell so that the load-side power will become greater, and controls the power distribution network so as to connect the selected load and the solar cell.

Description

[Technical Field]

[0001] The present invention relates to a technique for efficiently utilizing the power of solar cells. [Background technology]

[0002] Photovoltaic power generation using solar cells that convert sunlight into electricity is becoming widespread. The electricity converted from sunlight is used to charge a storage battery, for example.

[0003] In the past, it was common to convert direct current from solar cells to alternating current, and then convert the alternating current back into direct current to charge a storage battery. However, as shown in Non-Patent Document 1, in recent years, a technology has been used in which direct current from solar cells is directly charged into a storage battery.

[0004] As with the technology disclosed in Non-Patent Document 1, by charging a storage battery with direct current from a solar cell as is, the number of conversion stages is reduced, and the power generated by the solar cell can be used efficiently. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] https: / / www.itmedia.co.jp / smartjapan / articles / 1502 / 27 / news062.html, retrieved March 11, 2022 Summary of the Invention [Problem to be solved by the invention]

[0006] It is known that solar power generation has a characteristic in which the power that can be extracted varies depending on the voltage of a load such as a storage battery. However, conventional technologies such as Non-Patent Document 1 have not been able to maximize the power generated by solar cells by taking this characteristic into consideration. In other words, the power generated by solar cells has not been able to be used efficiently.

[0007] The present invention has been made in view of the above-mentioned points, and has an object to provide a technique for efficiently utilizing the power generated by a solar cell. [Means for solving the problem]

[0008] According to the disclosed technology, there is provided a control device that performs connection control in a power distribution network to which a solar cell and a plurality of loads are connected and which distributes power from the solar cell as direct current, the control device comprising: an information acquisition unit that acquires information from a load connected to the solar cell via the power distribution network; a control unit that selects a load to be connected to the solar cell so that the load-side power is increased based on the load-side power and the solar cell-side voltage obtained from the information, and controls the power distribution network to connect the selected load and the solar cell; The control unit In a voltage raising operation for selecting a load so as to increase the solar cell side voltage, a load with the largest load side power is selected as the load to be connected to the solar cell from among one or more loads whose solar cell side voltage becomes higher than the current solar cell side voltage. A control device is provided. [Effects of the Invention]

[0009] According to the disclosed technology, it is possible to efficiently utilize the power generated by the solar cell. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 illustrates an example of a solar cell and a battery connected to a DC grid. [Figure 2] FIG. 1 is a diagram showing an example of voltage-power characteristics of a solar cell. [Figure 3] FIG. 1 is a diagram illustrating an example of the configuration of a power control system. [Figure 4] FIG. 1 is a diagram illustrating an example of the configuration of a power control system. [Figure 5] FIG. 2 is a diagram illustrating an example of the configuration of a control device. [Figure 6] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device. [Figure 7] 4 is a flowchart illustrating the operation of the control device. [Figure 8]FIG. 10 is a diagram for explaining a specific example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0012] In the following embodiment, a storage battery is used as a load to which power is supplied from a solar cell, but this is just an example, and a load other than a storage battery may also be used. The power charged to the storage battery may also be called load-side power.

[0013] (Outline of the embodiment) In this embodiment, as shown in Fig. 1, a system in which a solar cell 200 and a plurality of storage batteries are connected via a DC grid is targeted. Here, the term "DC grid" is used to mean a power distribution network that distributes the output from the solar cell 200, which is a DC power source, to the storage batteries as DC without converting it to AC. The "power distribution network" may also be called a "power grid," "power transmission and distribution network," "power transmission network," etc. "Power distribution" may also be called "power transmission."

[0014] 1, a solar cell 200 and a plurality of storage batteries are connected via a power router 300. The power router 300 is a device capable of switching the distribution path of the power output from the solar cell 200, and may also be called a "path switching device," a "connection switching device," a "path selection device," or the like.

[0015] As mentioned above, with solar power generation, the amount of power that can be extracted varies depending on the load voltage. An example of this variation is shown in Figure 2. In Figure 2, the voltage at which peak power is obtained also varies depending on the solar power generation conditions (weather, etc.). In other words, the curve in the graph shown in Figure 2 fluctuates.

[0016] In this embodiment, the power router 300 switches the connection so that power is distributed to the storage battery that outputs the most power from the solar cell 200, thereby maximizing the power generated by the solar cell.

[0017] Although MPPT (Maximum Power Point Tracking) has been known for some time, which controls the power from a solar cell to maximize it, there has not been a technology for maximizing the power of a solar cell by switching the storage battery to which the power is distributed, as in the present embodiment. Note that in the present embodiment, for convenience, the control of switching the storage battery may be referred to as "pseudo MPPT."

[0018] The technology according to this embodiment has the advantage of reducing power conversion loss by not using a power conversion device such as a DC / AC converter, and also of maximizing the power generated by the solar cell through pseudo-MPPT control.

[0019] (System configuration example) Fig. 3 shows an example of the configuration of a power control system according to this embodiment. As shown in Fig. 3, a solar cell 200 and a plurality of storage batteries are connected via a power distribution network, and the power distribution network has a configuration in which a plurality of power routers 300 are connected by power lines. Furthermore, each storage battery is connected to one of the power routers 300 by a power line. Note that the "power line" may also be called a "distribution line," "transmission line," or the like.

[0020] As shown in Fig. 3, a control server 100 is connected to each storage battery and each power router 300. The control server 100 instructs the power router 300 to perform path control based on information acquired from each storage battery. In this embodiment, one storage battery is connected to a solar cell 200 at a certain time. The control server 100 may also be called a control device.

[0021] In this embodiment, pseudo-stepped MPPT control is performed by switching between optimal storage batteries to maximize power generation based on information on storage battery capacity, wiring length, etc., taking into account the characteristics of solar cell 200 as shown in Fig. 2. A detailed control flow will be described later. In the following description, "power," "current," and "voltage" may also be referred to as "power value," "current value," and "voltage value," respectively.

[0022] FIG. 3 shows the situation of storage batteries A, C, and D as an example. For example, in storage battery A, the wiring length between the storage battery A and the solar cell 200 is short. Therefore, the resistance is small and the voltage drop is small. Also, because the battery capacity is 50%, the voltage (bus voltage) is low. Therefore, the voltage of storage battery A is the lowest compared to the others.

[0023] (Detailed configuration) Fig. 4 is a diagram showing in more detail the configuration of the power control system according to this embodiment. For convenience of illustration, Fig. 4 shows two storage batteries and one power router.

[0024] As shown in Figure 4, this power control system has a solar cell 200, a power router 300, a BMU 410, a storage battery 420, a BMU 510, a storage battery 520, and a control server 100. Each device other than the control server 100 is connected by a power line as shown in the figure. The control server 100 is connected to the power router 300 and each BMU by a communication line. An overview of the functions of each part is as follows.

[0025] The solar cell 200 converts sunlight into electric power. The power router 300 changes the route of the power line (switches the connection) based on a command from the control server 100. The power router 300 may have any mechanism that can change the route of the power line (switches the connection), but for example, it has a switching mechanism made up of multiple circuit breakers or relays.

[0026] The BMUs (Battery Management Units) 410 and 510 measure the voltage and current of the storage batteries and transmit the measured values ​​to the control server 100. The storage batteries 420 and 520 are devices that store power.

[0027] The control server 100 selects the storage battery that can extract the most power from the storage battery voltage and current obtained from the BMU, and issues a route formation command to the power router 300 to connect the selected storage battery to the solar cell.

[0028] (Configuration example of control server 100) 5 shows an example of the functional configuration of the control server 100. As shown in FIG. 5, the control server 100 includes an information acquisition unit 110, a calculation unit 120, a control unit 130, and a data storage unit 140.

[0029] The information acquisition unit 110 acquires the voltage and current of the storage battery from the BMU. The voltage of the storage battery is the voltage of the bus (between two power lines) that charges / discharges the storage battery, and the current is the current that flows through that bus. Note that acquiring the voltage and current from the BMU may also be expressed as "acquiring the voltage and current from the storage battery."

[0030] The calculation unit 120 calculates the storage battery charging power and the solar cell side voltage using the information acquired by the information acquisition unit 110 and the information read from the data storage unit 140. The control unit 130 uses the calculation results by the calculation unit 120 to control the operation of the power router 300.

[0031] The data storage unit 140 stores information (fixed information) used in calculations by the calculation unit 120, such as the resistance value of the wiring between the solar cell 200 and each storage battery. The data storage unit 140 also stores information acquired by the information acquisition unit 110 and calculation results calculated by the calculation unit 120. When the control unit 130 performs control, past calculation results are read out from the data storage unit 140 and used as appropriate.

[0032] (Example of hardware configuration) The control server 100 can be realized, for example, by causing a computer to execute a program. This computer may be a physical computer or a virtual machine on the cloud.

[0033] That is, the control server 100 can be realized by using hardware resources such as a CPU and memory built into a computer to execute a program corresponding to the processing performed by the control server 100. The program can be recorded on a computer-readable recording medium (such as a portable memory) and can be saved or distributed. The program can also be provided via a network such as the Internet or email.

[0034] Fig. 6 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 6 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, and the like, all of which are interconnected via a bus BS.

[0035] A program for realizing processing on the computer is provided by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0036] The memory device 1003 reads and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 realizes functions related to the control server 100 in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network (communication line). The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, mouse, buttons, a touch panel, or the like, and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0037] (Example of operation of control server 100) An example of the operation of the control server 100 having the functional configuration shown in Fig. 5 will be described with reference to the flowchart of Fig. 7. First, the processing content based on the flow will be described, and then a specific example will be described.

[0038] In S1, the information acquisition unit 110 acquires information. Specifically, under the control of the control unit 130, the solar cell 200 is connected in order to each of a plurality of storage batteries in the power distribution network (DC grid) that is the control target of the present proposed technology, and the information acquisition unit 110 acquires the measured values ​​of the voltage and current of the storage batteries at the time of connection.

[0039] In S2, the calculation unit 120 calculates the storage battery charging power and the solar cell side voltage for each storage battery from the measurement values ​​acquired in S1 and the resistance values ​​of each path read from the data storage unit 140. Each path is the path between the solar cell 200 and the storage battery for each storage battery.

[0040] Regarding the storage battery x (when the storage battery x is connected to the solar cell 200), the storage battery charging power is P x and the battery voltage is Vb x and the battery current is I x Then, the calculation unit 120 calculates P x =Vb x ×I x Therefore, the battery charging power Px Calculate.

[0041] Regarding the storage battery x (when the storage battery x is connected to the solar cell 200), the solar cell side voltage is Vp x and the battery voltage is Vb x and the resistance of the wiring is R x Let the battery current (solar cell current) be I x Then, the calculation unit 120 calculates Vp x =Vb x +R x ×I x Therefore, the solar cell side voltage Vp x Calculate.

[0042] In S3, the control unit 130 forms a route by instructing the power router 300 to first connect the storage battery with the highest storage battery power to the solar cell 200 based on the calculation result in S2. After the route is formed (changed), charging is performed for a fixed time T1. In the subsequent processes, after the route is formed (changed), charging is also performed for a fixed time T1.

[0043] During charging (for example, near the end of period T1), information acquisition unit 110 acquires measured values ​​of current and voltage from the storage battery connected to solar cell 200. Then, pseudo-MPPT control is executed for each T1.

[0044] The processes of S4 to S9 described below are pseudo-MPPT control. Note that in this embodiment, the control starts with a voltage increase operation, but this is an example. The control may start with a voltage decrease operation.

[0045] In S4, the control server 100 performs a voltage increase operation. Specifically, the control unit 130 selects, based on the information stored in the data storage unit 140, the route with the largest past battery charge power from among routes with a solar cell side voltage higher than the solar cell side voltage calculated from the current current value and voltage value, and performs the route change.

[0046] The past storage battery charging power is the most recent past storage battery charging power in the loop control of S4 to S9. Note that, in the initial stage, for a storage battery that has not been connected to the solar cell 200 in the loop control of S4 to S9, the value calculated in S1 and S2 may be used.

[0047] In S5, the information acquisition unit 110 acquires the storage battery voltage and storage battery current for the route changed in S4, and the calculation unit 120 uses these to calculate the storage battery charging power and the solar cell side voltage.

[0048] In S6, the control unit 130 compares the storage battery charging power before and after the route change, and determines whether the storage battery charging power after the route change is greater than the storage battery charging power before the route change.

[0049] If the determination in S6 is Yes (increase), the process returns to S4 and executes the process from S4 again. If the determination in S6 is No (decrease), the process proceeds to S7.

[0050] In S7, the control server 100 performs a voltage reduction operation. Specifically, based on the information stored in the data storage unit 140, the control unit 130 selects the route with the largest past battery charge power from among routes having a solar cell side voltage lower than the solar cell side voltage calculated in the most recent S5, and performs the route change.

[0051] In S8, the information acquisition unit 110 acquires the storage battery voltage and storage battery current for the route changed in S7, and the calculation unit 120 uses these to calculate the storage battery charging power and the solar cell side voltage.

[0052] In S9, the control unit 130 compares the storage battery charging power before and after the route change, and determines whether the storage battery charging power after the route change is greater than the storage battery charging power before the route change.

[0053] If the determination in S9 is Yes (increase), the process returns to S7 and executes the process from S7 again. If the determination in S9 is No (decrease), the process proceeds to S4 and executes the process from S4 again.

[0054] (Example) Next, a specific example of processing based on the flow shown in Fig. 7 will be described. Here, it is assumed that the voltage-power characteristics of the solar cell 200 have the shape shown in Fig. 8. Also, it is assumed that the solar cell side voltages for storage battery A, storage battery B, storage battery C, and storage battery D are A, B, C, and D on the horizontal axis of Fig. 8, respectively.

[0055] 7 shows the battery charge power and wiring loss for each of storage batteries A, B, C, and D. As shown in FIG. 7, "storage battery charge power + wiring loss" is the power output by solar cell 200. Storage batteries A, C, and D correspond to storage batteries A, C, and D shown in FIG. 3.

[0056] In the following description, the route from storage battery A to solar cell 200 is referred to as route A, the route from storage battery B to solar cell 200 is referred to as route B, the route from storage battery C to solar cell 200 is referred to as route C, and the route from storage battery D to solar cell 200 is referred to as route D.

[0057] In S3 of FIG. 7, the control unit 130 instructs the power router 300 to connect the storage battery B, which has the largest storage battery power, to the solar battery 200, thereby forming the route B as the initial route.

[0058] In S4, based on the information stored in the data storage unit 140, the control unit 130 selects route D as the route with the greatest past battery charging power from among routes C and D, which have a solar cell side voltage higher than the solar cell side voltage of route B, and performs a change to route D.

[0059] In S5, the information acquisition unit 110 acquires the storage battery voltage and storage battery current for route D changed in S4, and the calculation unit 120 calculates the storage battery charging power and solar cell side voltage for route D using these.

[0060] In S6, the control unit 130 compares the storage battery charging power before and after the route change, and determines whether the storage battery charging power after the route change is greater than the storage battery charging power before the route change.

[0061] As shown in FIG. 8, the battery charge power of route D is lower than the battery charge power of route B, so the process proceeds to S7.

[0062] In S7, based on the information stored in the data storage unit 140, the control unit 130 selects route B as the route with the greatest past battery charging power from among the routes (A, B, C) having a solar cell side voltage lower than the solar cell side voltage (D) calculated in the most recent S5, and changes to route B.

[0063] In S8, the information acquisition unit 110 acquires the storage battery voltage and storage battery current for route B changed in S7, and the calculation unit 120 uses these to calculate the storage battery charging power and the solar cell side voltage.

[0064] In S9, the control unit 130 determines whether the charging power of the storage battery after the route change is greater than the charging power of the storage battery before the route change.

[0065] 8, the battery charge power of route B is greater than the battery charge power of route D, so the process returns to S7. Then, route A is selected.

[0066] The process continues as described above. In the above explanation, for the sake of convenience, the storage battery charging power and the solar cell side voltage are assumed to be fixed values ​​as shown in Fig. 8, but in reality, they change each time a measurement is made.

[0067] In addition, in the flow of Figure 7, when selecting the route to change to, the route with the greatest past battery charging power is selected from among the routes with a solar cell side voltage higher or lower than the current solar cell side voltage, but this is just an example.

[0068] In the voltage increasing operation, when selecting a route to change to, the route having the closest solar cell side voltage to the current solar cell side voltage may be selected from among routes having a solar cell side voltage higher than the current solar cell side voltage.In the voltage decreasing operation, when selecting a route to change to, the route having the closest solar cell side voltage to the current solar cell side voltage may be selected from among routes having a solar cell side voltage lower than the current solar cell side voltage.

[0069] In addition, in the flow of Figure 7, the control server 100 calculates the storage battery charging power and the solar cell side voltage based on the measurement values, but the storage battery charging power and the solar cell side voltage may be calculated from the measurement values ​​on the load side, and the information acquisition unit 110 may acquire the storage battery charging power and the solar cell side voltage from the load side.

[0070] (Effects of the embodiment) The technology described above makes it possible to maximize the power generated by a solar cell in a DC grid in which the solar cell and a plurality of loads (such as storage batteries) are connected.

[0071] (Addendum) The following additional clauses are disclosed in relation to the above-described embodiment. (Additional note 1) A control device that performs connection control in a power distribution network to which a solar cell and a plurality of loads are connected and which distributes power from the solar cell as direct current, Memory and at least one processor coupled to said memory; Including, The processor: acquiring information from a load connected to the solar cell via the power distribution network; Based on the load-side power and the solar cell-side voltage obtained from the information, a load to be connected to the solar cell is selected so that the load-side power becomes large, and the power distribution network is controlled so as to connect the selected load and the solar cell. Control device. (Additional note 2) The processor: In a voltage raising operation of selecting a load so as to increase the solar cell side voltage, a load that will have the largest load side power is selected as a load to be connected to the solar cell from among one or more loads whose solar cell side voltage will be higher than the current solar cell side voltage; In a voltage reduction operation of selecting a load so as to reduce the solar cell side voltage, a load with the largest load side power is selected as the load to be connected to the solar cell from among one or more loads whose solar cell side voltage is lower than the current solar cell side voltage. Item 1. The control device according to item 1. (Additional note 3) When the load connected to the solar cell is changed, The processor continues the voltage increase operation or the voltage decrease operation when the load side power increases after the change, and changes from the voltage increase operation to the voltage decrease operation or from the voltage decrease operation to the voltage increase operation when the load side power decreases after the change. The control device according to claim 2. (Additional note 4) The processor: Acquiring a voltage value and a current value from a load connected to the solar cell; The load-side power of the load is calculated from the voltage value and the current value, and the solar cell-side voltage is calculated from the voltage value, the current value, and the resistance value between the solar cell and the load. Item 1. The control device according to item 1. (Additional note 5) A power control system comprising the control device according to any one of appended items 1 to 4 and the solar cell. (Additional note 6) A control method by a computer used as a control device that performs connection control in a power distribution network in which a solar cell and a plurality of loads are connected and power from the solar cell is distributed as direct current, comprising: an information acquisition step of acquiring information from a load connected to the solar cell via the power distribution network; a control step of selecting a load to be connected to the solar cell so that the load-side power is increased based on the load-side power and the solar cell-side voltage obtained from the information, and controlling the power distribution network to connect the selected load and the solar cell; A control method comprising: (Additional note 7) A non-transitory storage medium storing a program for causing a computer to function as each unit in the control device described in any one of appendixes 1 to 4.

[0072] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0073] 100 Control Server 110 Information Acquisition Department 120 Calculation Department 130 Control Unit 140 Data storage unit 200 solar cells 300 Power Router 410 BMU 420 Battery 510 BMU 520 Battery 1000 Drive Device 1001 Recording media 1002 Auxiliary storage device 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input Device 1008 Output Device

Claims

1. A control device that performs connection control in a power distribution network to which a solar cell and a plurality of loads are connected and which distributes power from the solar cell as direct current, an information acquisition unit that acquires information from a load connected to the solar cell via the power distribution network; a control unit that selects a load to be connected to the solar cell so that the load-side power is increased based on the load-side power and the solar cell-side voltage obtained from the information, and controls the power distribution network to connect the selected load and the solar cell; The control unit In a voltage raising operation for selecting a load so as to increase the solar cell side voltage, a load with the largest load side power is selected as the load to be connected to the solar cell from among one or more loads whose solar cell side voltage becomes higher than the current solar cell side voltage. Control device.

2. A control device that performs connection control in a power distribution network to which a solar cell and a plurality of loads are connected and which distributes power from the solar cell as direct current, an information acquisition unit that acquires information from a load connected to the solar cell via the power distribution network; a control unit that selects a load to be connected to the solar cell so that the load-side power is increased based on the load-side power and the solar cell-side voltage obtained from the information, and controls the power distribution network to connect the selected load and the solar cell; The control unit In a voltage reduction operation for selecting a load so as to reduce the solar cell side voltage, a load with the largest load side power is selected as the load to be connected to the solar cell from among one or more loads whose solar cell side voltage will be lower than the current solar cell side voltage. Control device.

3. When the load connected to the solar cell is changed, The control unit continues the voltage increase operation when the load side power increases before and after the change, and when the load side power decreases before and after the change, changes from the voltage increase operation to a voltage decrease operation that selects a load so as to decrease the solar cell side voltage. The control device according to claim 1 .

4. When the load connected to the solar cell is changed, The control unit continues the voltage reduction operation when the load-side power increases before and after the change, and when the load-side power decreases before and after the change, changes from the voltage reduction operation to a voltage increase operation that selects a load so as to increase the solar cell-side voltage. The control device according to claim 2 .

5. A power control system comprising the control device according to claim 1 and the solar cell.

6. A control method by a control device that performs connection control in a power distribution network in which a solar cell and a plurality of loads are connected and power from the solar cell is distributed as direct current, comprising: an information acquisition step of acquiring information from a load connected to the solar cell via the power distribution network; a control step of selecting a load to be connected to the solar cell so that the load-side power is increased based on the load-side power and the solar cell-side voltage obtained from the information, and controlling the power distribution network to connect the selected load and the solar cell; In the control step, the control device In a voltage raising operation for selecting a load so as to increase the solar cell side voltage, a load with the largest load side power is selected as the load to be connected to the solar cell from among one or more loads whose solar cell side voltage becomes higher than the current solar cell side voltage. Control method.

7. A control method by a control device that performs connection control in a power distribution network in which a solar cell and a plurality of loads are connected and power from the solar cell is distributed as direct current, comprising: an information acquisition step of acquiring information from a load connected to the solar cell via the power distribution network; a control step of selecting a load to be connected to the solar cell so that the load-side power is increased based on the load-side power and the solar cell-side voltage obtained from the information, and controlling the power distribution network to connect the selected load and the solar cell; In the control step, the control device In a voltage reduction operation for selecting a load so as to reduce the solar cell side voltage, a load with the largest load side power is selected as the load to be connected to the solar cell from among one or more loads whose solar cell side voltage will be lower than the current solar cell side voltage. Control method.

8. A program for causing a computer to function as each unit in the control device according to any one of claims 1 to 4.

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