Power procurement device

Abstract

To provide a power procurement device capable of suppressing occurrence of imbalance.SOLUTION: A power procurement device performs power procurement by supplying power from a plurality of power suppliers to a power system. Each of the plurality of power suppliers comprises a fuel cell device and a power consumption device. Surplus power obtained by subtracting consumed power of the power consumption device from output of the fuel cell device can be supplied to the power system as inverse tide power. In a case where a total of inverse tide power from the plurality of power suppliers to the power system can be changed at a predetermined maximum total change speed, on the assumption that the total of the inverse tide power from the plurality of power suppliers to the power system at an end time point of a predetermined target time zone is defined as predetermined end time total inverse tide power, regarding a total inverse tide power amount supplied from the plurality of power suppliers to the power system in the target time zone, it is determined whether or not a difference between the total inverse tide power amount and a predetermined target total inverse tide power amount can be a value within a predetermined range from the target total inverse tide power amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a power procurement device that procures power by causing a plurality of power suppliers to supply power to a power grid. [Background technology]

[0002] In addition to conventional large-scale power plants, power supply devices such as power generation devices and charge / discharge devices installed in facilities such as homes and offices are also connected to the power system. In addition, power consumption devices installed in the facilities are also connected to the power system. In recent years, under the concept of a virtual power plant (VPP), attempts have been made for power generation companies to control the operation of consumer-side energy resources such as the above-mentioned power supply devices and power consumption devices installed in consumer facilities.

[0003] For example, when a power generation company procures power from multiple power suppliers who own power supply devices, the total value of surplus power, which is the value obtained by subtracting the power consumption of power consumption devices from the output power of the power supply devices at each facility of the multiple power suppliers, for the multiple facilities becomes the procured power from the multiple power suppliers. For example, as shown in Figure 8, in the case of four 30-minute frames from 12:00 to 14:00, the power generation company calculates the total reverse flow power of the multiple power suppliers as a specified power x m By remotely controlling each power supplier to operate in such a way that the total reverse flow power shown in the figure can be generated in each 30-minute frame, and reverse flow can be provided to the power grid.

[0004] In addition, since power generation companies can procure power from other power procurement sources, such as the power trading market, in a specific 30-minute block, when the power procurement unit price for procuring power from another power procurement source is cheaper than the power procurement unit price for purchasing surplus power (i.e., reverse flow power) from a power supplier, it is economically preferable to procure power from another power procurement source. FIG. 9 shows an example of a case where a power generation company procures power from the power trading market in a 30-minute block of the target time slot between 12:30 and 13:00. In this case, the power generation company calculates the total reverse flow power to the power grid from multiple power suppliers until 12:30 as power x m During the target time period between 12:30 and 13:00, the total reverse power flow to the power grid from multiple power suppliers is controlled to x t As a result, during the target time period from 12:30 to 13:00, the amount of reverse flow power shown in the figure is supplied to the power grid.

[0005] In this way, for example, if the electricity procurement price from a specific electricity supplier becomes cheaper, a power generation company can change its procurement method to procure electricity from that specific electricity supplier, enabling it to procure electricity more economically.

[0006] With regard to the electricity procured by power generation companies, it is necessary to match the planned value of the amount of reverse flow power procured every 30 minutes with the actual value of the amount of reverse flow power within the framework of a power generation balancing group that includes power suppliers such as power plants and power trading markets, and multiple power suppliers equipped with the above-mentioned power supply devices.The power generation company is required to settle the difference between the planned and actual values ​​of the amount of reverse flow power.

[0007] Patent Document 1 (JP 2019-215693 A) describes an energy trading support device that aims to reduce imbalance penalties. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2019-215693 A Summary of the Invention [Problem to be solved by the invention]

[0009] In addition, when the power supply device of each power supplier is a fuel cell device, there is an upper limit to the rate of change of the output power (i.e., the rate of change of the reverse flow power). Therefore, as shown in FIG. 10, even if the reverse flow power starts to increase by starting to increase the output power of the fuel cell device from time 13:00, it takes a certain amount of time for the reverse flow power to actually reach a predetermined value. In other words, if the total reverse flow power of multiple power suppliers is power x t Power from x m It takes a certain amount of time for the power supply to reach the target value, and a power shortage occurs for that time. In other words, at the time of 13:00, that is, at the end of the target time period between 12:30 and 13:00, the total reverse power flow from multiple power suppliers is x m As a result, there is a possibility that an imbalance will occur in the time period between 13:00 and 13:30, in which the actual value of the total amount of reverse power flow by the multiple power suppliers will not match the planned value of the total amount of reverse power flow by the multiple power suppliers that was planned in advance.

[0010] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a power procurement device that can suppress the occurrence of imbalance. [Means for solving the problem]

[0011] A characteristic configuration of a power procurement device according to the present invention for achieving the above object is a power procurement device that procures power by supplying power from a plurality of power suppliers to a power grid, Each of the plurality of power suppliers includes a fuel cell device and a power consuming device, and is capable of supplying surplus power obtained by subtracting the power consumption of the power consuming device from the output of the fuel cell device as reverse flow power to the power grid; The point is that, when the total of the reverse flow power to the power system by the multiple power suppliers can be changed at a predetermined maximum total change rate, on the premise that the total of the reverse flow power at the end of a predetermined target time period is set to a predetermined total reverse flow power at the end, it is determined whether the total amount of reverse flow power supplied by the multiple power suppliers to the power system during the target time period can be set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power.

[0012] According to the above characteristic configuration, by setting the total reverse flow power to the power grid by multiple power suppliers at the end of the target time period to a predetermined total reverse flow power at the end (for example, the total reverse flow power to the power grid by multiple power suppliers at the start of the time period next to the target time period), it is possible to prevent imbalance from occurring in the time period next to the target time period.

[0013] In addition, setting the sum of reverse flow power to the power grid by multiple power suppliers at the end of a target time slot to a predetermined total reverse flow power at the end also leads to the generation of unnecessary reverse flow power in the target time slot. Therefore, the amount of reverse flow power in the target time slot increases, and an imbalance may occur in the target time slot. However, in this characteristic configuration, it is determined whether the total amount of reverse flow power supplied to the power grid by multiple power suppliers in the target time slot can be set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power. In other words, if an imbalance is prevented from occurring in the time slot next to a specific target time slot, it is possible to verify in advance whether an imbalance may occur in the specific target time slot. Therefore, it is possible to provide a power procurement device that can suppress the occurrence of imbalance.

[0014] Another characteristic configuration of the power procurement device of the present invention is that the target total reverse flow power amount is set to a value obtained by subtracting from the maximum total reverse flow power amount, which is the maximum value of the total reverse flow power amount that multiple power suppliers can supply to the power system during the target time period, the amount of power that can be procured from the power trading market within a range that does not exceed the maximum total reverse flow power amount.

[0015] If the unit price of procuring electricity from the energy trading market during the target time period is lower than the unit price of purchasing reverse flow electricity from the electricity supplier, a plan may be made to procure from the energy trading market a portion of the amount of reverse flow electricity that the electricity supplier had planned to supply to the power grid during the target time period. In this case, in this characteristic configuration, the target total reverse flow power is set to a value obtained by subtracting the amount of power that can be procured from the power trading market within a range not exceeding the maximum total reverse flow power from the maximum total reverse flow power, which is the maximum value of the total reverse flow power that multiple power suppliers can supply to the power grid during the target time period. Then, it is possible to determine whether the total reverse flow power supplied by multiple power suppliers to the power grid during the target time period can be set to a value such that the difference between the total reverse flow power and the target total reverse flow power falls within a predetermined range from the target total reverse flow power.

[0016] Another characteristic configuration of the power procurement device according to the present invention is a configuration in which, on the premise that the total of the reverse flow power is set to a constant assumed value from the start point of the target time period to a transition point in the middle of the target time period, and the total of the reverse flow power is changed from the assumed value to the end total reverse flow power at the maximum total change rate from the transition point to the end point, The point is that the total amount of backward flow power is determined as the value obtained by integrating the sum of the backward flow power at each time point in the target time period over the target time period.

[0017] According to the above characteristic configuration, the total amount of reverse flow power can be derived by setting the total reverse flow power from multiple power suppliers to a constant assumed value from the start of a target time period to a transitional point in the middle of the target time period, and changing the total reverse flow power from the assumed value to the total reverse flow power at the maximum total change rate from the transitional point to the end of the target time period. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing a configuration of a system in which a power procurement device is provided. [Diagram 2] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Diagram 3] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Figure 4] A flowchart for explaining a process for determining a target total amount of reverse flow power [Diagram 5] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Figure 6] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Figure 7] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Figure 8] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Figure 9] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. [Figure 10] FIG. 11 is a diagram showing an example of a transition of the total reverse flow power of a plurality of power suppliers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a power procurement device 4 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a system in which a power procurement device 4 is provided. As shown in the figure, a power supplier 10 and a power supply facility 2 connected to a power system 1 are set as a balancing group G. The power procurement device 4 is configured to be able to communicate with the power supplier 10, the power supply facility 2, the power trading market 3, and the like via information and communication lines. Although three power suppliers 10 are depicted in FIG. 1, the number of power suppliers 10 can be changed as appropriate. Each power supplier 10 includes a fuel cell device 11 and a power consumption device 12. The power supply facility 2 is, for example, a thermal power generation facility, a wind power generation facility, a solar power generation facility, or the like. Each of the multiple power suppliers 10 can supply surplus power, which is obtained by subtracting the power consumption of the power consumption device 12 from the output power of the fuel cell device 11, to the power system 1 as reverse flow power.

[0020] The power procurement device 4 determines the power supplied by the multiple power suppliers 10 and the power supply facilities 2. In other words, the power procurement device 4 procures power by causing a balancing group G including the multiple power suppliers 10 and the power supply facilities 2 to supply power to the power system 1.

[0021] For example, as shown in Fig. 8, the power procurement device 4 of the power generation company determines the total amount of reverse flow power that multiple power suppliers 10 supply to the power system 1. Then, the power procurement device 4 distributes the total amount of reverse flow power to be supplied to the power system 1 by each of the multiple power suppliers 10, and transmits the distribution to each power supplier 10. Note that since the power generation company can also procure power from another power procurement source, such as the power trading market 3, it is economically preferable to procure power from another power procurement source during a specific 30-minute frame (i.e., a target 30-minute time period) when the power procurement unit price for procuring power from another power procurement source is lower than the power procurement unit price for purchasing surplus power from the power supplier 10.

[0022] Fig. 2 shows an example in which a power generation company procures power from the power trading market 3 as another power procurement source during a target time period between 12:30 and 13:00. Note that what is shown in Fig. 2 and other figures is the total amount of reverse flow power from multiple power suppliers 10 included in a balancing group G.

[0023] The power generation company calculates the total reverse flow power of the multiple power suppliers 10 as power x between 12:30 and 13:00. m A command is given from a remote location to make the total of the reverse flow power of the multiple power suppliers 10 be equal to the power x t In addition, the power generation company procures power from the power trading market 3 as another power procurement source between the time 12:30 and the time 13:00.

[0024] In the energy trading market 3, a bidding unit for procuring electricity is set, so that of the amount of electricity that the power supplier 10 planned to supply between 12:30 and 13:00, an integer multiple of that bidding unit will be the amount of electricity to be procured from the energy trading market 3, and the remaining amount of electricity must be covered by the amount of reverse flow electricity from multiple power suppliers 10.

[0025] As shown in FIG. 3, the total of the reverse flow powers from the multiple power suppliers 10 is changed at a predetermined maximum total change rate, and the total of the reverse flow powers from the multiple power suppliers 10 at the end of a predetermined target time period is calculated as the total reverse flow power at the end of the predetermined time period x m Otherwise, as shown in Fig. 10, the total amount of reverse flow power from the multiple power suppliers 10 to the power grid 1 between the time 13:00 and the time 13:30 will decrease by the amount of the power shortage shown in the figure, resulting in a difference between the planned value of the total amount of reverse flow power and the actual value of the total amount of reverse flow power.

[0026] However, the total reverse flow power of the multiple power suppliers 10 at the end of the target time period is the total reverse flow power at the end of the target time period x m In other words, the total amount of reverse flow power from the multiple power suppliers 10 during the target time period increases, which may cause an imbalance during the target time period.

[0027] Therefore, the power procurement device 4 determines whether or not the total amount of reverse flow power supplied by the multiple power suppliers 10 to the power system 1 in a target time period can be set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power. In other words, when imbalance is prevented from occurring in the time period next to a specific target time period, it is verified in advance whether imbalance may occur in the specific target time period.

[0028] Specifically, when the power procurement device 4 can change the total output power of the fuel cell devices 11 of the multiple power suppliers 10 at a predetermined maximum total change rate, that is, when the power procurement device 4 can change the total reverse flow power of the multiple power suppliers 10 at a predetermined maximum total change rate (maximum reverse flow increase rate), the power procurement device 4 calculates the total reverse flow power of the multiple power suppliers 10 to the power grid 1 at the end of a predetermined target time period as the predetermined end total reverse flow power x m On the premise that the total amount of reverse flow power supplied to the power grid 1 by the multiple power suppliers 10 during the target time period ("total amount of reverse flow power" shown in FIG. 3) is calculated by multiplying the total amount of reverse flow power by a predetermined target amount of reverse flow power (target total amount of reverse flow power shown in FIG. 2: 30x t It is determined whether the difference between the target total backward flow power amount (kWm) and the target total backward flow power amount (kWm) can be set to a value that is within a predetermined range from the target total backward flow power amount.

[0029] Next, a procedure for determining the target total amount of backward flow power in a target time period will be described. 4 is a flowchart explaining a process for determining a target total amount of reverse flow power. When the unit price of the amount of reverse flow power procured from the power supplier 10 during the target time period is higher than the unit price of the amount of power procured from other power procurement sources, the power procurement device 4 executes this flowchart before the target time period.

[0030] In step #10, the power procurement device 4 provisionally determines a target total amount of reverse flow power. In this case, as shown in Fig. 2, the target total amount of reverse flow power is set to a value obtained by subtracting the amount of power that can be procured from the power trading market 3 within a range not exceeding the maximum total amount of reverse flow power from the maximum total amount of reverse flow power, which is the maximum value of the total amount of reverse flow power that multiple power suppliers 10 can supply to the power system 1 during the target time period.

[0031] More specifically, since the unit of the amount of power that can be bid on is fixed in the energy trading market 3, the amount of power that can be procured from the energy trading market 3 is an integer multiple of that unit amount of power. Therefore, the power procurement device 4 can determine the maximum amount of procured power, which is the maximum amount of power (however, an integer multiple of the unit amount of power) that can be procured from the energy trading market 3 without exceeding the maximum total amount of reverse flow power. The power procurement device 4 then provisionally determines the value obtained by subtracting the maximum amount of procured power from the maximum total amount of reverse flow power as the target total amount of reverse flow power.

[0032] Next, in step #11, when the total of the reverse flow power from the multiple power suppliers 10 can be changed at a predetermined maximum total change rate (maximum reverse flow increase rate), the power procurement device 4 calculates the total of the reverse flow power from the multiple power suppliers 10 to the power system 1 at the end of the predetermined target time period as the predetermined end time total reverse flow power x m On the premise that the total amount of reverse flow power supplied by multiple power suppliers 10 to the power system 1 during the target time period is set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range of the target total amount of reverse flow power.

[0033] As shown in FIG. 2, in the target time period between 12:30 and 13:00, the target total amount of reverse power flow by the multiple power suppliers 10 is 30×x t In reality, the total reverse flow power from the multiple power suppliers 10 at 13:00 is calculated as the end total reverse flow power x m In order to achieve this, it is necessary to change the total amount of reverse flow power from a plurality of power suppliers 10 during the target time period, as shown in FIG.

[0034] That is, as shown in FIG. 3, from the start time of the target time period (12:30) to the transient time point t1 in the middle of the target time period, the sum of the reverse power flows by the plurality of power suppliers 10 is set to a certain assumed value x t ’, and during the output increase period t’ from the transient time point t1 to the end time (13:00), the assumed value x t ’ to the total reverse power flow x at the end m It is assumed that the sum of the reverse power flows is changed at the maximum total change rate. The assumed value x in this case t ’ and the output increase period t’ (0 < t’ < 30) can be calculated as follows.

[0035] The target total reverse power amount 30 × x t [kWm] in FIG. 2 is equal to the total reverse power amount in FIG. 3, so the following equation (1) holds.

[0036]

Equation

[0037] The maximum total change rate R [kW / m] of the sum of the reverse power flows by the plurality of power suppliers 10 is represented by the following equation (2) because of the slope when increasing the reverse power flow.

Equation

[0038] Therefore, from equations (1) and (2) and x t ’ > 0, the following equations (3) and (4) hold.

Equation

[0039] Here, x tIf '>0, it is determined that no imbalance will occur. That is, the power procurement device 4 determines that the total amount of reverse flow power supplied by the multiple power suppliers 10 to the power system 1 in the target time period can be set to a value such that the difference between that total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power. Then, in step #12, the power procurement device 4 finally determines the target total amount of reverse flow power.

[0040] In addition, the total reverse flow power cannot be negative, so x t It is determined that an imbalance occurs if '<0. That is, in step #11, the power procurement device 4 determines that the total amount of reverse flow power supplied to the power system 1 by the multiple power suppliers 10 in the target time period cannot be set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power.

[0041] Furthermore, x t When '=0, it is sufficient that the imbalance that occurs is within a predetermined range from the target total reverse flow power amount. Here, as shown in FIG. 5, the target total reverse flow power amount is 30×x t As shown in Figure 6, t The total amount of reverse flow power when '=0 is expressed by the following equation (5).

number

[0042] Therefore, as shown in Figure 6, x t The imbalance that occurs when '=0 is expressed by the following equation (6).

[0043]

number

[0044] If the imbalance tolerance rate for the target total reverse flow power is α, the value of equation (6) is 30×x, which corresponds to a predetermined range from the target total reverse flow power. t×α[kWm] or less is sufficient.

[0045]

number

[0046] In this way, x t If '=0, then in step #11, power procurement device 4 determines that if the above formula (7) is satisfied, the total amount of reverse flow power supplied by multiple power suppliers 10 to power system 1 in the target time period can be set to a value such that the difference between that total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power. Then, in step #12, power procurement device 4 finally determines the target total amount of reverse flow power.

[0047] Then, the power procurement device 4 distributes and commands the target total amount of reverse flow power to the multiple power suppliers 10. How the target total amount of reverse flow power is distributed to the multiple power suppliers 10 can be set appropriately. Also, the power procurement device 4 sets the amount of power to be procured from the power trading market 3 in the target time period to a value obtained by subtracting the target total amount of reverse flow power from the maximum amount of reverse flow power, which is the maximum amount of reverse flow power that the power supplier 10 can supply to the power system 1 in the target time period, and procures that amount of power in the power trading market 3.

[0048] In contrast, if the power procurement device 4 determines in step #11 that the total amount of reverse flow power supplied to the power system 1 by multiple power suppliers 10 during the target time period cannot be set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range of the target total amount of reverse flow power, the power procurement device 4 proceeds to step #13.

[0049] In step #13, the power procurement apparatus 4 increases the target total amount of reverse flow power. Specifically, as shown in Fig. 7, the power procurement apparatus 4 increases the target total amount of reverse flow power by a bidding unit (e.g., one bidding unit) to the power trading market 3, and sets the increased value as a provisional target total amount of reverse flow power. Then, the power procurement apparatus 4 performs the judgment in step #11 again.

[0050] As described above, by setting the total reverse flow power to the power system 1 from multiple power suppliers 10 at the end of the target time period to a predetermined total reverse flow power at the end (for example, the total reverse flow power to the power system 1 from multiple power suppliers 10 at the start of the next time period after the target time period), it is possible to prevent imbalance from occurring in the time period after the target time period.

[0051] Furthermore, the power procurement device 4 determines whether the total amount of reverse flow power supplied by the multiple power suppliers 10 to the power system 1 during the target time period can be set to a value such that the difference between the total amount of reverse flow power and a predetermined target total amount of reverse flow power falls within a predetermined range from the target total amount of reverse flow power. In other words, if imbalance is prevented from occurring in the time period next to a specific target time period, it is possible to verify in advance whether imbalance may occur in the specific target time period. Then, it is possible to determine the target total amount of reverse flow power at which imbalance will not occur.

[0052] <Another embodiment> In the above embodiment, the configuration of the system provided with the power procurement device 4 has been illustrated, but the configuration can be changed as appropriate. For example, in the above embodiment, an example is described in which the power procurement device 4 issues a command value corresponding to the target total amount of reverse flow power to the power supplier 10, but the configuration may also be such that a system other than the power procurement device 4 transmits a command value corresponding to the target total amount of reverse flow power to the power supplier 10.

[0053] In the above embodiment, an example has been described in which the power procurement apparatus 4 increases the target total amount of reverse flow power from the multiple power suppliers 10 in step #13 when the result of the determination in step #11 is "No." However, the power procurement apparatus 4 may perform another process. For example, as shown in FIG. 10, the total amount of reverse flow power from the multiple power suppliers 10 during the target time period between 12:30 and 13:00 may be increased by a constant value x t The total reverse flow power of the multiple power suppliers 10 during the next time period (between 13:00 and 13:30) is set to a constant value x tAnother power from x m It may be changed to.

[0054] In other words, when the power procurement unit price for purchasing surplus power from the power supplier 10 during a specific target time period is higher than the power procurement unit price for procuring power from another power procurement source such as the power trading market 3, the power procurement device 4 may set the target total amount of reverse flow power of the power supplier 10 during that target time period to a value obtained by subtracting from the maximum reverse flow power amount, which is the maximum amount of reverse flow power that the power supplier 10 can supply to the power system 1 during that target time period, the amount of power that can be procured from the power trading market 3 within a range not exceeding the maximum reverse flow power amount (i.e., the maximum procurement amount of power). Also, the power procurement device 4 may set the amount of power procured from the power trading market 3 during that target time period to the above-mentioned maximum procurement amount of power, and procure that amount of power from the power trading market 3.

[0055] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided that no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0056] The present invention can be used in a power procurement device that can suppress the occurrence of imbalance. [Explanation of symbols]

[0057] 1 Power system 2 Power equipment 3. Electricity trading market 4. Power procurement equipment 10 Electricity supplier 11 Fuel cell device 12 Power consumption equipment

Claims

1. A power procurement device that procures power by supplying power from a plurality of power suppliers to a power grid, Each of the plurality of power suppliers includes a fuel cell device and a power consuming device, and is capable of supplying surplus power obtained by subtracting the power consumption of the power consuming device from the output of the fuel cell device as reverse flow power to the power grid; A power procurement device that determines whether a total amount of reverse flow power supplied by a plurality of power suppliers to the power system during a specified target time period can be set to a value such that a difference between the total amount of reverse flow power and a specified target total amount of reverse flow power falls within a specified range of the target total amount of reverse flow power, when the total amount of reverse flow power supplied to the power system by a plurality of power suppliers can be changed at a specified maximum total change rate, on the premise that the total amount of reverse flow power at the end of a specified target time period will be set to a specified total amount of reverse flow power at the end.

2. 2. The power procurement device according to claim 1, wherein the target total amount of reverse flow power is set to a value obtained by subtracting from a maximum total amount of reverse flow power, which is a maximum value of the total amount of reverse flow power that can be supplied to the power system by the multiple power suppliers during the target time period, an amount of power that can be procured from the power trading market within a range not exceeding the maximum total amount of reverse flow power.

3. on the premise that, from a start point of the target time period to a transition point in the middle of the target time period, the total of the reverse flow power is set to a constant assumed value, and, from the transition point to the end point, the total of the reverse flow power is changed at the maximum total change rate from the assumed value to the end total reverse flow power, The power procurement device according to claim 1 or 2, wherein a value obtained by integrating a sum of the reverse flow power at each time point in the target time period over the target time period is determined as the total reverse flow power amount.

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