Fuel Cell Management System

Abstract

A fuel cell management system is provided that can appropriately control reverse power flow from a facility to a power grid. [Solution] The management device 30 of the fuel cell management system is configured, when a power shortage condition is met, to determine the new target reverse flow power to be next commanded to the multiple facilities 20 to be a value greater than the current target reverse flow power by an amount of correction power determined by performing a predetermined correction process on the difference between the target reverse flow power and the actual reverse flow power, and, when a power surplus condition is met, to determine the new target reverse flow power to be next commanded to the multiple facilities 20 to be a value smaller than the current target reverse flow power by an amount of correction power determined by performing a correction process on the difference, and the correction process is performed so that the correction power is greater when the power shortage condition is met than when the power surplus condition is met.

Description

[Technical Field]

[0001] The present invention relates to a fuel cell management system that includes a fuel cell device that is installed in each of a plurality of facilities and is capable of supplying power to a power line connected to a power grid in each of the plurality of facilities, and a management device that is capable of communicating with the plurality of fuel cell devices from a remote location outside the facilities. [Background technology]

[0002] In addition to conventional large-scale power plants, power supply devices such as generators and charge / discharge devices installed in facilities such as homes and offices are also connected to the power grid. Power load devices installed in the facilities are also connected to the power grid. Using the power supply devices and power load devices to increase or decrease the power at the facility's receiving point can contribute to balancing the supply and demand of power in the power grid. In recent years, under the concept of a virtual power plant (VPP), attempts have been made to provide functionality equivalent to that of a power plant by controlling the operation of consumer-side energy resources, such as the power supply devices and power load devices installed in consumer facilities. The term "power at the receiving point of a facility" includes both the power received from the power grid to the facility and the reverse power flow from the facility to the power grid.

[0003] When fuel cell devices installed in a facility are used as consumer-side energy resources, for example, a management device capable of communicating with multiple fuel cell devices from a remote location outside the facility transmits output control commands to the multiple fuel cell devices that determine target reverse flow power, which is a target value for the reverse flow power to be supplied from the facility to the power grid. When the fuel cell devices receive the output control command from the management device, they control their output power so that power equal to the target reverse flow power is supplied from the facility to the power grid.

[0004] However, because fuel cell devices generate power by consuming supplied fuel such as hydrogen, they cannot increase their output power unless the fuel supply is increased. In contrast, fuel cell devices can easily decrease their output power. That is, in a fuel cell device, the rate at which the output power increases when the output power is increased is smaller than the rate at which the output power decreases when the output power is decreased. Therefore, when a fuel cell device installed in a facility is used as a consumer-side energy resource for a VPP, even if a management device sends an output control command to the fuel cell device to increase the target reverse flow power, the increase in the output power of the fuel cell device may be delayed, potentially preventing the facility from supplying appropriate reverse flow power to the power grid.

[0005] In addition, if the load power of the power load devices installed in the facility increases, the fuel cell device must increase its output power in response to the increase in load power in order to supply power equal to the target reverse flow power from the facility to the power grid. However, as mentioned above, if the increase in output power of the fuel cell device is delayed in response to the increase in load power, there is a risk that the appropriate reverse flow power cannot be supplied to the power grid.

[0006] Fig. 8 is a diagram showing the transitions of the output power output by the fuel cell device to the power line, the load power of the power load device, the target reverse flow power which is the reverse flow power that the facility aims to supply to the power grid, and the actual reverse flow power in the facility shown in Fig. 2. In Fig. 8, the horizontal axis represents time and the vertical axis represents power. The time range of the horizontal axis is shown as a range from 0 minutes (0:00:00) to 30 minutes (0:30:00).

[0007] As shown in Figure 8, the target reverse flow power is 200 (W). In other words, even if the load power increases or decreases, the fuel cell device only needs to adjust the output power so that the output power remains at [load power + 200 (W)]. In the example shown, the load power of the power load device alternately increases or decreases between 400 (W) and 100 (W), so the fuel cell device needs to increase or decrease the output power of the fuel cell unit in accordance with the increase or decrease in the load power.

[0008] However, in a fuel cell device, the rate at which output power is increased is smaller than the rate at which output power is decreased. As a result, the output power cannot be increased in line with the load power increase at the timing of that increase, and as shown in Figure 8, a time period occurs in which the actual reverse flow power is less than the target reverse flow power. Although not shown, even if the management device sends an output control command to the fuel cell device to increase the target reverse flow power, a delay in the increase in the output power of the fuel cell device will similarly cause a time period in which the actual reverse flow power is less than the target reverse flow power.

[0009] Patent Document 1 (JP 2018-207706 A) describes the use of fuel cell devices installed in facilities as consumer-side energy resources for VPPs, and attempts to control the operation of consumer-side energy resources using information about the rate of fluctuation in power in devices such as fuel cell devices. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018-207706 Summary of the Invention [Problem to be solved by the invention]

[0011] The management device cannot know the rate at which the output power of the fuel cell device increases or decreases, and therefore cannot determine the target reverse flow power to be supplied from the facility to the power grid while taking into account the rate at which the output power of the fuel cell device increases or decreases.

[0012] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a fuel cell management system that can appropriately control reverse flow power from a facility to a power grid. [Means for solving the problem]

[0013] A characteristic configuration of a fuel cell management system according to the present invention for achieving the above object is a fuel cell management system including a fuel cell device installed in each of a plurality of facilities and capable of supplying power to a power line connected to a power grid in each of the plurality of facilities, and a management device capable of communicating with the plurality of fuel cell devices from a remote location outside the facilities, the management device transmits to the plurality of fuel cell devices an output control command that determines a target reverse flow power, which is a target value of the reverse flow power that should be supplied from the facility to the power grid; when receiving the output control command from the management device, the fuel cell device controls the output power to be output to the power line so that power equal to the target reverse flow power is supplied from the facility to the power grid; The management device obtaining information about actual reverse flow power supplied to the power grid from a plurality of the facilities; when a predetermined power shortage condition is satisfied, the new target reverse flow power to be next commanded to the plurality of facilities is determined to be a value larger than the current target reverse flow power by an amount of correction power determined by performing a predetermined correction process on a difference between the current target reverse flow power being commanded to the plurality of facilities and the actual reverse flow power supplied from the plurality of facilities to the power grid; and when a predetermined power surplus condition is satisfied, the new target reverse flow power to be next commanded to the plurality of facilities is determined to be a value smaller than the current target reverse flow power by an amount of correction power determined by performing the correction process on the difference; In the correction process, if the difference is the same when the power shortage condition is satisfied and when the power surplus condition is satisfied, the correction power is larger when the power shortage condition is satisfied than when the power surplus condition is satisfied. Here, the management device may determine that the power shortage condition is satisfied when the sum of the actual amounts of reverse flow power supplied from the multiple facilities to the power system during a set period is smaller than the sum of the target amounts of reverse flow power from the multiple facilities during the set period that can be derived from the current target reverse flow power commanded to the multiple facilities, and may determine that the power surplus condition is satisfied when the sum of the actual amounts of reverse flow power supplied from the multiple facilities to the power system during the set period is greater than the sum of the target amounts of reverse flow power from the multiple facilities during the set period that can be derived from the current target reverse flow power commanded to the multiple facilities. Here, in the correction process, the management device may set the correction power to a value obtained by adding a predetermined correction value to the product of the difference and a predetermined coefficient, and set at least one of the coefficient and the correction value when determining that the new target reverse flow power to be commanded to the multiple facilities next is a value greater than the current target reverse flow power to a value greater than the coefficient and the correction value when determining that the new target reverse flow power to be commanded to the multiple facilities next is a value smaller than the current target reverse flow power.

[0014] According to the above characteristic configuration, when the power shortage condition is satisfied, the management device determines that the new target reverse flow power to be commanded to the multiple facilities next is a value larger than the current target reverse flow power by an amount of correction power determined by performing a predetermined correction process on the difference between the current target reverse flow power commanded to the multiple facilities and the actual reverse flow power supplied from the multiple facilities to the power grid, and when the power surplus condition is satisfied, the management device determines that the new target reverse flow power to be commanded to the multiple facilities next is a value smaller than the current target reverse flow power by an amount of correction power determined by performing the correction process on the difference.As a result, the actual amount of reverse flow power supplied from the multiple facilities to the power grid within a set period can be made to approach the amount of reverse flow power that needs to be supplied to the power grid. In particular, in this characteristic configuration, if the difference is the same when the power shortage condition is satisfied and when the power surplus condition is satisfied, the correction process is performed so that the correction power is larger when the power shortage condition is satisfied than when the power surplus condition is satisfied. In other words, the correction process is performed so that the change in the target reverse flow power is larger when the reverse flow power from the facility is increased (i.e., when the output power of the fuel cell device is increased) than when the reverse flow power from the facility is decreased (i.e., when the output power of the fuel cell device is decreased). As a result, even if the required reverse flow power cannot be temporarily supplied to the power grid because the output increase rate of the fuel cell device is slow, it is expected that the actual amount of reverse flow power supplied to the power grid from the multiple facilities within the subsequent set period will approach the amount of reverse flow power that needs to be supplied to the power grid. Therefore, it is possible to provide a fuel cell management system that can appropriately control the reverse flow of power from the facility to the power grid.

[0015] Another characteristic feature of the fuel cell management system of the present invention is that the management device acquires information about the actual reverse flow power supplied to the power system from multiple facilities and the output power of the fuel cell device, and determines that the time period is one in which output fluctuations are frequent if the number of times that the output power has decreased by a predetermined value or more within a specified period in the most recent past is equal to or greater than a set number, and determines that the time period is one in which output fluctuations are infrequent if the number of times that the output power has decreased by a predetermined value or more within the specified period is less than the set number, and in the correction process, the correction power is made larger during time periods in which output fluctuations are frequent than during time periods in which output fluctuations are infrequent.

[0016] When the frequency of output fluctuations in the output power of the fuel cell device is high (i.e., when the frequency of load power fluctuations of the power load device is high), there is a higher possibility that the changes in the output power of the fuel cell device will not be able to keep up with the load fluctuations compared to when the frequency of output fluctuations is low (i.e., when the frequency of load power fluctuations of the power load device is low).If the changes in the output power of the fuel cell device cannot keep up with the load fluctuations, the amount of power that can be supplied to the power grid within a set period is less than the amount of reverse flow power that needs to be supplied to the power grid. However, in this characteristic configuration, the correction process is performed so that the correction power is larger during time periods when the frequency of output fluctuations is high than during time periods when the frequency of output fluctuations is low. In other words, even if multiple fuel cell devices are temporarily unable to supply the necessary reverse flow power to the power grid, it is expected that the necessary amount of reverse flow power will be able to be supplied to the power grid from the multiple fuel cell devices thereafter. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram showing the relationship between facilities, a management device, and an aggregation coordinator. [Figure 2] FIG. 1 is a diagram illustrating an example of a facility configuration. [Figure 3] FIG. 2 is a diagram illustrating a control period and a non-control period. [Figure 4]10A and 10B are diagrams illustrating an example of changes in load power of a power load device, output power of a fuel cell device, and reverse flow power. [Figure 5] FIG. 10 is a diagram showing the transition of the cumulative error of the amount of reverse flow power. [Figure 6] FIG. 10 is a diagram illustrating an example of a transition of load power. [Figure 7] FIG. 10 is a diagram showing the transition of the cumulative error of the amount of reverse flow power. [Figure 8] FIG. 10 is a diagram showing changes in load power, output power, target reverse flow power, and reverse flow power. DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 is a diagram showing the relationship between facilities 20 in which fuel cell devices 10 and power load devices 4 are installed, a management device 30, and an aggregation coordinator 40. FIG. 2 is a diagram showing an example configuration of the facility 20. The fuel cell management system is installed in each of the multiple facilities 20 and includes a fuel cell device 10 capable of supplying power to a power line 2 connected to a power grid 1 in each of the multiple facilities 20, and a management device 30 capable of communicating with the multiple fuel cell devices 10 from a remote location outside the facility 20. Note that the number of management devices 30 and the number of facilities 20 shown in FIG. 1 can be changed as appropriate.

[0019] The management device 30 is also called a resource aggregator, and is an operator that controls consumer-side energy resources by transmitting control information to the fuel cell device 10 and the power load device 4 as consumer-side energy resources for the facility 20 that has concluded a VPP (Virtual Power Plant) service contract. The aggregation coordinator 40 is an operator that aggregates the amount of power controlled by each management device 30 and trades power with general power transmission and distribution companies and electricity retailers in the electricity trading market, etc.

[0020] The management device 30 sequentially collects and stores power information from multiple facilities 20, such as the output power of the fuel cell device 10, the load power of the power load devices 4, and the power receiving point power at the facilities 20 (i.e., the actual reverse flow power supplied from the facilities 20 to the power grid 1, and the received power supplied from the power grid 1 to the facilities 20). As will be described later, the fuel cell device 10 can determine the reverse flow power (an example of the power receiving point power) supplied from the facilities 20 to the power grid 1 by referring to the measurement results of the power measurement unit 8, and can transmit this reverse flow power (an example of the power receiving point power) to the management device 30 as one piece of the power information. In other words, the management device 30 can obtain information about the actual reverse flow power supplied from multiple facilities 20 to the power grid 1. In this embodiment, the term "load power of the power load devices 4" refers to the total load power of all the power load devices 4 installed in the facilities 20. The management device 30 then predicts the power that can be supplied from each facility 20 during a predetermined future time period and transmits this information to the aggregation coordinator 40. This available power is an adjustment margin, such as the ability to increase or decrease the power at the power receiving point of the facility 20. In this embodiment, "increasing the power receiving point power" means increasing the power received from the power grid 1 to the power line 2, or decreasing the reverse flow power from the power line 2 to the power grid 1, and "decreasing the power receiving point power" means decreasing the power received from the power grid 1 to the power line 2, or increasing the reverse flow power from the power line 2 to the power grid 1.

[0021] For example, in order to increase the power receiving point power of the facility 20, it is sufficient to at least either reduce the output power of the fuel cell device 10 or increase the load power of the power load device 4, so the upward adjustment margin when increasing the power receiving point power of the facility 20 indicates how much margin there is for reducing the output power of the fuel cell device 10, and how much margin there is for increasing the load power of the power load device 4. Also, in order to decrease the power receiving point power of the facility 20, it is sufficient to at least either increase the output power of the fuel cell device 10 or decrease the load power of the power load device 4, so the downward adjustment margin when decreasing the power receiving point power of the facility 20 indicates how much margin there is for increasing the output power of the fuel cell device 10, and how much margin there is for decreasing the load power of the power load device 4.

[0022] Furthermore, the management device 30 determines baseline power receiving point power for the multiple facilities 20 that it manages. This baseline power receiving point power corresponds to the total power receiving point power of each facility 20 predicted when each facility 20 does not provide adjustment capacity, etc. (i.e., including adjustment capacity provided to the electricity transmission and distribution company and supply capacity provided to the retailer, etc.).

[0023] The aggregation coordinator 40 aggregates the available power received from each management device 30 and trades power with general electricity transmission and distribution companies and electricity retailers by bidding on electricity trading markets such as the supply and demand adjustment market, the wholesale electricity market, and the capacity market. When the aggregation coordinator 40 receives a supply command for adjustment capacity or the like for a predetermined future control period from the general electricity transmission and distribution company or the electricity retailer with which it has traded, it distributes and transmits the adjustment capacity or the like specified in the supply command to each management device 30.

[0024] When the management device 30 receives a supply command from the aggregation coordinator 40, it distributes and transmits the adjustment capacity and the like specified in the supply command to each facility 20. As a result, in each facility 20, by controlling the fuel cell devices 10 and power load devices 4 as consumer-side energy resources during a predetermined future control period, adjustment capacity and the like are supplied, which increases or decreases the power at the receiving point of the facility 20 compared to when the control is not performed.

[0025] The facility 20 is provided with a fuel cell device 10 and a power load device 4. The fuel cell device 10 and the power load device 4 are connected to a power line 2 that is interconnected to a power grid 1. Although FIGS. 1 and 2 show an example in which one fuel cell device 10 is installed, the number of installed fuel cell devices 10 can be changed as appropriate.

[0026] The power load device 4 is a variety of devices such as a lighting device, an air conditioner, etc., and can receive power supply from at least one of the fuel cell device 10 installed in the facility 20 and the power system 1.

[0027] The fuel cell device 10 includes a fuel cell unit 12 connected to a power line 2 that is connected to a power grid 1, a power conversion unit 11 that converts the power generated by the fuel cell unit 12 into a predetermined voltage, frequency, and phase and supplies it to the power line 2, a fuel cell control unit 13 that controls the operation of the fuel cell unit 12 and the power conversion unit 11, and a memory unit 14 that stores information handled by the fuel cell device 10. The fuel cell device 10 may also include a fuel reformer that generates hydrogen, which is the fuel gas for the fuel cell unit 12.

[0028] The fuel cell control unit 13 can adjust the output power from the fuel cell device 10 to the power line 2 between a predetermined upper limit output power and a predetermined lower limit output power. For example, the fuel cell control unit 13 can maintain the output power of the fuel cell device 10 at the upper limit output power to allow continuous operation. The fuel cell control unit 13 can also operate the fuel cell device 10 so that the output power follows the load power of the power load device 4. For example, the fuel cell control unit 13 can operate the fuel cell device 10 so that the power measured by the power measurement unit 8 (i.e., the power supplied from the power grid 1) becomes zero or close to zero, thereby allowing the fuel cell device 10 to operate so that the output power follows the load power of the power load device 4. Alternatively, the fuel cell control unit 13 can adjust the output power of the fuel cell device 10 so that the power measured by the power measurement unit 8 becomes a predetermined negative power (i.e., a predetermined reverse flow power).

[0029] The fuel cell control unit 13 has information about the output power supplied from the power conversion unit 11 to the power line 2 and information about the power measured by the power measurement unit 8, and is therefore able to derive the load power (= output power + measured power) of the power load device 4. If the sign of the power measured by the power measurement unit 8 is positive, this means that the load power is greater than the output power of the fuel cell device 10, and if the sign of the power measured by the power measurement unit 8 is negative, this means that the output power of the fuel cell device 10 is greater than the load power (i.e., reverse flow power is being supplied from the facility 20 to the power grid 1).

[0030] The fuel cell device 10 is connected to a remote control 7 that is operated by users of the facility 20 when issuing commands to the fuel cell device 10. Information about the output power and load power of the fuel cell device 10 is transmitted to the management device 30 via the remote control 7 and the router 6. For example, information about the output power and load power of the fuel cell device 10 is transmitted to the management device 30 at a predetermined timing, such as every minute.

[0031] As described above, the management device 30 can transmit output control commands to the multiple fuel cell devices 10, which determine target reverse flow power, which is a target value of reverse flow power to be supplied from the facility 20 to the power grid 1. When the fuel cell devices 10 receive an output control command from the management device 30, they operate in a first operation mode that targets the supply of output power determined based on the output control command during a control period that is the target of the output control command, and operate in a second operation mode that is different from the first operation mode during a non-control period that is outside the control period.

[0032] The management device 30 then changes the target reverse flow power at a predetermined timing within the set period so that the total amount of reverse flow power supplied from the multiple facilities 20 to the power grid 1 during that set period becomes the target total amount of reverse flow power, and retransmits this to each fuel cell device 10. In this embodiment, the management device 30 commands the same target reverse flow power to the multiple facilities 20. In this way, the management device 30 actually commands target reverse flow power to the fuel cell devices 10 in the multiple facilities 20, but in the following example, the embodiment will be described taking as an example a case where a target reverse flow power is commanded to the fuel cell device 10 in one facility 20.

[0033] The second operating mode is an operating mode that is preset in the plurality of fuel cell devices 10. Alternatively, the management device 30 can transmit an operating mode control command that determines the second operating mode to the plurality of fuel cell devices 10, and the fuel cell devices 10 determine the second operating mode in accordance with the operating mode control command received from the management device 30.

[0034] Fig. 3 is a diagram illustrating a control period and a non-control period. In the example shown in Fig. 3, the control information (output control command) specifies the period from 12:00 to 15:00 as the control period. Therefore, the fuel cell device 10 operates in the first operation mode during the control period from 12:00 to 15:00, and operates in the second operation mode during the other non-control periods. A specific example of the first operation mode will be described below.

[0035] FIG. 4 is a diagram showing an example of changes in the output power (calculated value) of the fuel cell device 10, the load power of the power load device 4, the reverse flow power required from the facility 20 to the power grid 1, and the actual reverse flow power (calculated value). The output power (calculated value) and the actual reverse flow power (calculated value) of the fuel cell device 10 are derived assuming that the frequency of the target reverse flow power command from the management device 30 to the fuel cell device 10 is once per minute and the output increase rate of the fuel cell device 10 is 10 (W / sec). The method of deriving the target reverse flow power commanded from the management device 30 to the fuel cell device 10 will be described later. In FIG. 4, the horizontal axis represents time, and the vertical axis represents power. The time range of the horizontal axis ranges from 0 minutes (0:00:00) to 30 minutes (0:30:00).

[0036] As shown in the figure, the reverse flow power required by the management device 30 is set to 200 (W). Therefore, for example, the target reverse flow power that the management device 30 initially transmits to the fuel cell device 10 is set to 200 (W). When the fuel cell control unit 13 of the fuel cell device 10 receives an output control command from the management device 30 that specifies the target reverse flow power, it controls the output power that is output to the power line 2 so that power equal to the target reverse flow power is supplied from the facility 20 to the power system 1. Then, the fuel cell control unit 13 simply adjusts the output power so that 200 (W) of reverse flow power can be supplied from the facility 20 to the power system 1 even if the load power increases or decreases.

[0037] However, as described with reference to FIG. 8 , if the target reverse flow power instructed by the management device 30 to the fuel cell device 10 is left at 200 (W), a time period will occur in which the actual reverse flow power is less than the target reverse flow power (200 (W)). In this case, a power shortage condition is met in which the actual amount of reverse flow power (Wh) supplied from the facility 20 to the power grid 1 during the set period is smaller than the target amount of reverse flow power (Wh) from the facility 20 during the set period that can be derived from the current target reverse flow power (W) instructed to the facility 20. In other words, in terms of power (W) per unit time, the power shortage condition is met when the average value of the actual reverse flow power (W) supplied from the facility 20 to the power grid 1 during the set period is smaller than the current target reverse flow power (W) instructed to the facility 20 by the management device 30. Furthermore, if there are multiple facilities 20, the above-mentioned power shortage condition is met if the total of the actual reverse flow power amounts (Wh) supplied from the multiple facilities 20 to the power system 1 during the set period is smaller than the total of the target reverse flow power amounts (Wh) from the multiple facilities 20 during the set period that can be derived from the current target reverse flow power (W) commanded to the multiple facilities 20.

[0038] Conversely, there may be cases where the actual amount of backward flow power (Wh) supplied from the facilities 20 to the power grid 1 during the set period is greater than the target amount of backward flow power (Wh) from the facilities 20 during the set period that can be derived from the current target backward flow power (W) commanded to the facilities 20. In other words, in terms of power (W) per unit time, the excess power condition is satisfied when the average value of the actual backward flow power (W) supplied from the facilities 20 to the power grid 1 during the set period is greater than the current target backward flow power (W) commanded to the facilities 20 by the management device 30. In addition, if there are multiple facilities 20, the excess power condition is satisfied when the total amount of actual backward flow power (Wh) supplied from the multiple facilities 20 to the power grid 1 during the set period is greater than the total target backward flow power (Wh) from the multiple facilities 20 during the set period that can be derived from the current target backward flow power (W) commanded to the multiple facilities 20.

[0039] From the above, the management device 30 of this embodiment is configured so that, when the above-mentioned specified power shortage condition is met, the management device 30 determines the new target reverse flow power to be next commanded to the multiple facilities 20 to be a value larger than the current target reverse flow power by the amount of correction power determined by performing a specified correction process on the difference between the current target reverse flow power being commanded to the multiple facilities 20 and the actual reverse flow power supplied to the power system 1 from the multiple facilities 20, and when the above-mentioned specified power surplus condition is met, the management device 30 determines the new target reverse flow power to be next commanded to the multiple facilities 20 to be a value smaller than the current target reverse flow power by the amount of correction power determined by performing a correction process on the above-mentioned difference. The contents of the power shortage condition and the power surplus condition can be changed as appropriate.

[0040] Here, in the correction process, if the difference between when the power shortage condition is satisfied and when the power surplus condition is satisfied is the same, the management device 30 performs processing such that the correction power is larger when the power shortage condition is satisfied than when the power surplus condition is satisfied.

[0041] For example, the management device 30 compares the current target reverse flow power instructed to the facility 20 with the average reverse flow power over a set period of time in the past (e.g., five minutes) supplied from the facility 20 to the power grid 1, and determines whether the power shortage condition or the power surplus condition is met. In this embodiment, the management device 30 determines that the power shortage condition is met if "current target reverse flow power - average reverse flow power over the past five minutes > 0", and determines that the power surplus condition is met if "current target reverse flow power - average reverse flow power over the past five minutes < 0". The management device 30 then derives a new target reverse flow power as follows.

[0042] [When the power shortage condition is satisfied (when the amount of reverse flow power supplied from the facility 20 is less than the target value, and the new target reverse flow power is determined to be a value greater than the current target reverse flow power)] New target reverse flow power = Current target reverse flow power + Correction power (1) Corrected power = difference × coefficient + correction value (2) Difference = Current target reverse flow power - Average reverse flow power for the past 5 minutes (3)

[0043] [When the power surplus condition is satisfied (when the amount of reverse flow power supplied from the facility 20 is greater than the target value, and the new target reverse flow power is determined to be a value smaller than the current target reverse flow power)] New target reverse flow power = Current target reverse flow power + Correction power (4) Corrected power = difference × coefficient (5) Difference = Average reverse flow power over the past 5 minutes - Current target reverse flow power (6)

[0044] In the above formula (2), the correction value on the right side is a positive number. Also, although the correction value is not written in formula (5), it can be considered as 0. In this way, in the correction process, the management device 30 sets the value obtained by adding the predetermined correction value to the product of the difference and a predetermined coefficient as the corrected power.

[0045] 4, when the power shortage condition is satisfied (when the new target reverse flow power is determined to be a value larger than the current target reverse flow power), the coefficient for the correction power in equation (2) is 0.1 and the correction value is +35 (W). Also, when the power surplus condition is satisfied (when the new target reverse flow power is determined to be a value smaller than the current target reverse flow power), the coefficient for the correction power in equation (5) is 0.1.

[0046] In this way, in the correction process, assuming that the coefficients shown in formula (2) and formula (5) are the same and that the difference is the same when the power shortage condition is satisfied and when the power surplus condition is satisfied (i.e., assuming that the absolute value of "current target reverse flow power - average reverse flow power for the past five minutes" is the same), the correction power is processed so that it is larger when the power shortage condition is satisfied (formula (2)) than when the power surplus condition is satisfied (formula (5)). To this end, the management device 30 sets at least one of the coefficient and correction value when determining that the new target reverse flow power to be next commanded to the multiple facilities 20 is a value larger than the current target reverse flow power, to a value larger than the coefficient and correction value when determining that the new target reverse flow power to be next commanded to the multiple facilities 20 is a value smaller than the current target reverse flow power.

[0047] As is clear from Figure 4, when the load power increases, there is a time period when the actual reverse flow power is less than the required reverse flow power, but there is also a time period afterwards when the actual reverse flow power is greater than the required reverse flow power.

[0048] FIG. 5 is a diagram showing the transition of the cumulative error of the amount of reverse flow power. In FIG. 5, the horizontal axis represents time, and the time range of the horizontal axis is from 0 minutes (0:00:00) to 30 minutes (0:30:00). The vertical axis represents the cumulative error of the amount of reverse flow power (Wh) actually supplied by facility 20 to power grid 1 within the period from 0 minutes, relative to the amount of reverse flow power (Wh) that would be expected if the amount of reverse flow power actually supplied by facility 20 to power grid 1 were equal to the target reverse flow power. The solid line in FIG. 5 shows the transition of the cumulative error when the correction values ​​in equations (2) and (5) are set to +35 (W), and the dashed line in FIG. 5 shows the transition of the cumulative error when the correction values ​​in equations (2) and (5) are set to 0 (W).

[0049] As is clear from Figure 5, when the correction value was set to 0 (W), the cumulative error in the amount of reverse flow power fluctuated around -5%, and the cumulative error hardly approached 0% even over time. In contrast, when the correction value was set to +35 (W), the cumulative error in the amount of reverse flow power fluctuated around 0%, indicating that the reverse flow power from facility 20 to power grid 1 was appropriately controlled.

[0050] Next, another example in which the correction value is changed will be described. Fig. 6 is a diagram showing an example of the transition of the load power of the power load device 4. In Fig. 6, the horizontal axis represents time and the vertical axis represents power. The time range of the horizontal axis is shown as a range from 0 minutes (0:00:00) to 35 minutes (0:35:00).

[0051] FIG. 6 shows an example of a case where the frequency of load fluctuations is high and an example of a case where the frequency of load fluctuations is low. In this embodiment, the fuel cell control unit 13 of the fuel cell device 10 increases the output power output from the fuel cell device 10 to the power line 2 when the load power increases, so that power equal to the target reverse flow power commanded by the management device 30 is supplied from the facility 20 to the power system 1. When the load power decreases, the fuel cell control unit 13 decreases the output power output from the fuel cell device 10 to the power line 2. Therefore, the management device 30 acquires information about the actual reverse flow power supplied to the power system 1 from the multiple facilities 20 and the output power of the fuel cell device 10. If the number of times that the output power has decreased by a predetermined value or more within a predetermined period in the most recent past is equal to or greater than a set number, the management device 30 determines that the time period is a time period where the frequency of output fluctuations is high (i.e., a time period where the frequency of load fluctuations is high). If the number of times that the output power has decreased by a predetermined value or more within a predetermined period is less than the set number, the management device 30 determines that the time period is a time period where the frequency of output fluctuations is low (i.e., a time period where the frequency of load fluctuations is low). The predetermined period, predetermined value, and setting values ​​used to determine whether the frequency of load fluctuations is high can be set as appropriate.

[0052] Fig. 7 is a diagram showing the transition of the cumulative error in the amount of backward flow power from facility 20 to power grid 1 when the load power of power load device 4 exhibits the load fluctuations shown in Fig. 6. In Fig. 7, the horizontal axis represents time, and the time range of the horizontal axis is shown as a range from time 0 minute (0:00:00) to time 30 minutes (0:30:00). The vertical axis represents the cumulative error of the amount of backward flow power (Wh) actually supplied by facility 20 to power grid 1 within the period from time 0 minute, relative to the amount of backward flow power (Wh) that would be expected if the backward flow power actually supplied by facility 20 to power grid 1 were equal to the target backward flow power.

[0053] Figure 7 shows the transition of the cumulative error of the amount of reverse flow power when the correction value is set to +35 (W) and +15 (W) when the frequency of load changes is high (corresponding to the case where the frequency of load changes is high in Figure 6). Figure 7 also shows the transition of the cumulative error of the amount of reverse flow power when the correction value is set to +35 (W) and +15 (W) when the frequency of load changes is low (corresponding to the case where the frequency of load changes is low in Figure 6). The coefficients in the above formulas (2) and (5) are the same whether the frequency of load changes is high or low.

[0054] That is, in the correction process of the example shown in FIG. 7, the correction power is made larger in a time period when the frequency of load fluctuations is high than in a time period when the frequency of load fluctuations is low.

[0055] As shown in Figure 7, when the frequency of load fluctuations is high, the cumulative error of the amount of reverse flow power remains in a range closer to 0% when the correction value is set to +35 (W) than when it is set to +15 (W). Therefore, when the frequency of load fluctuations is high, it can be said that it is preferable to set the correction value to +35 (W).

[0056] Furthermore, as shown in Fig. 7, when the frequency of load fluctuations is low, the cumulative error of the amount of reverse flow power remains in a range closer to 0% when the correction value is set to +15 (W) than when it is set to +35 (W). Therefore, when the frequency of load fluctuations is low, it can be said that it is preferable to set the correction value to +15 (W).

[0057] As described above, when the frequency of load fluctuations is high, there is a higher possibility that the change in the output power of the fuel cell device 10 will not be able to keep up with the load fluctuations compared to when the frequency of load fluctuations is low. If the change in the output power of the fuel cell device 10 cannot keep up with the load fluctuations, the fuel cell device 10 will only be able to supply to the power grid 1 an amount of power that is less than the amount of reverse flow power that needs to be supplied to the power grid 1 within a set period. However, as shown in the example of FIG. 7, a correction process is performed so that the corrected power is larger during time periods when the frequency of load fluctuations is high than during time periods when the frequency of load fluctuations is low. In other words, even if the required reverse flow power cannot be temporarily supplied to the power grid 1, it is expected that the required amount of reverse flow power will be able to be supplied to the power grid 1 within the subsequent set period.

[0058] In the above embodiment, calculated values ​​such as the output power of the fuel cell device 10, the load power of the power load, and the actual reverse flow power in one facility 20 are shown, but the management device 30 actually commands a target reverse flow power to each fuel cell device 10 in multiple facilities 20. Furthermore, the management device 30 commands the same target reverse flow power to each of the multiple facilities 20. Therefore, "when the frequency of load fluctuations is high" can be interpreted as a time period when there are many facilities 20 that experience load fluctuations, and "when the frequency of load fluctuations is low" can be interpreted as a time period when there are few facilities 20 that experience load fluctuations.

[0059] <Another embodiment> In the above embodiment, a specific example of the configuration of the fuel cell device 10 has been described, but the configuration can be modified as appropriate.

[0060] In the above embodiment, specific numerical values ​​have been exemplified for the correction values ​​and coefficients shown in Equation (2) and Equation (5), but these numerical values ​​have been described for illustrative purposes and can be changed as appropriate. Furthermore, the trends in output power, load power, required reverse flow power, actual reverse flow power, etc. described in the above embodiment and drawings have been described for illustrative purposes and differ from actual numerical values.

[0061] Furthermore, 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, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0062] INDUSTRIAL APPLICABILITY The present invention can be used in a fuel cell management system that can appropriately control reverse power flow from a facility to a power grid. [Explanation of symbols]

[0063] 1: Power system 2: Power lines 4:Power load device 10:Fuel cell device 12:Fuel cell section 13: Fuel cell control unit

Claims

1. A fuel cell management system comprising: a fuel cell device installed in each of a plurality of facilities and capable of supplying power to a power line connected to a power grid in each of the plurality of facilities; and a management device capable of communicating with the plurality of fuel cell devices from a remote location outside the facilities, the management device transmits to the plurality of fuel cell devices an output control command that determines a target reverse flow power, which is a target value of the reverse flow power that should be supplied from the facility to the power grid; when receiving the output control command from the management device, the fuel cell device controls the output power to be output to the power line so that power equal to the target reverse flow power is supplied from the facility to the power grid; The management device obtaining information about actual reverse flow power supplied to the power grid from a plurality of the facilities; when a predetermined power shortage condition is satisfied, the new target reverse flow power to be next commanded to the plurality of facilities is determined to be a value larger than the current target reverse flow power by an amount of correction power determined by performing a predetermined correction process on a difference between the current target reverse flow power being commanded to the plurality of facilities and the actual reverse flow power supplied from the plurality of facilities to the power grid; and when a predetermined power surplus condition is satisfied, the new target reverse flow power to be next commanded to the plurality of facilities is determined to be a value smaller than the current target reverse flow power by an amount of correction power determined by performing the correction process on the difference; In the correction process, if the difference is the same when the power shortage condition is satisfied and when the power surplus condition is satisfied, the correction power is larger when the power shortage condition is satisfied than when the power surplus condition is satisfied.

2. The management device determining that the power shortage condition is satisfied when a total of actual amounts of backward flow power supplied from the plurality of facilities to the power grid during a set period is smaller than a total of target amounts of backward flow power from the plurality of facilities during the set period that can be derived from the current target backward flow power commanded to the plurality of facilities; 2. The fuel cell management system according to claim 1, wherein the power surplus condition is determined to be satisfied when a total of actual amounts of reverse flow power supplied from the plurality of facilities to the power grid during the set period is greater than a total of the target amounts of reverse flow power from the plurality of facilities during the set period that can be derived from the current target reverse flow power commanded to the plurality of facilities.

3. The management device acquiring information about actual reverse flow power supplied from a plurality of the facilities to the power grid and the output power of the fuel cell device; Regarding the output power, if the number of times that a decrease of a predetermined value or more occurs within a predetermined period in the most recent past is equal to or greater than a set number of times, it is determined that the time period is one in which the frequency of output fluctuations is high, and if the number of times that a decrease of the predetermined value or more occurs within the predetermined period is less than the set number of times, it is determined that the time period is one in which the frequency of output fluctuations is low, 3. The fuel cell management system according to claim 1, wherein the correction process is performed so that the correction power is larger during time periods when the frequency of output fluctuations is high than during time periods when the frequency of output fluctuations is low.

4. The management device In the correction process, a value obtained by adding a predetermined correction value to the product of the difference and a predetermined coefficient is set as the correction power, 3. The fuel cell management system according to claim 1, wherein at least one of the coefficient and the correction value when the new target reverse flow power to be commanded next to the plurality of facilities is determined to be a value greater than the current target reverse flow power is set to a value greater than the coefficient and the correction value when the new target reverse flow power to be commanded next to the plurality of facilities is determined to be a value smaller than the current target reverse flow power.

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