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

Abstract

On the basis of a predicted value of power demand and a predicted value of the generated power of a power generation system using a natural energy, this power system control device determines the generated power of a fuel cell system in the future so that the sum of the fluctuation of the generated power of the fuel cell system, the purchased power from a power grid, and the reverse power flow power to the power grid becomes the minimum region, and outputs a command for controlling the fuel cell system so as to output the determined generated power.

Description

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

[0001] The present disclosure relates to a technique for controlling a power system that supplies electric power.

[0002] For example, Patent Document 1 discloses a power supply system that supplies electric power. The power supply system includes a fuel cell that can generate electricity using fuel and supply the generated electricity to a load connected to a grid power supply, a power storage system that has a storage battery that can be charged and discharged according to the power demand of the load after the power generated by the fuel cell has been supplied, and a power generation unit that can generate electricity using natural energy and charge the generated electricity to the storage battery, and a control unit that can control the operation of the fuel cell. The control unit can suppress the generated electricity of the fuel cell when predetermined conditions set according to the power purchase and sale are met.

[0003] However, the above-mentioned conventional technology does not take into consideration the operation of a fuel cell in a manner that suppresses reverse flow power and purchased power while suppressing deterioration of the fuel cell, and further improvements are needed.

[0004] Japanese Patent Application Laid-Open No. 2021-58027

[0005] The present disclosure has been made to solve the above problems, and aims to provide a technology that can operate a fuel cell so as to suppress reverse flow power and purchased power while suppressing fuel cell degradation.

[0006] The power system control method according to the present disclosure is a power system control method in a computer, and includes determining the future power generation power of the fuel cell system based on a predicted value of power demand and a predicted value of power generation power of a power generation system that uses natural energy, so that the sum of fluctuations in the power generation power of the fuel cell system, power purchased from the power grid, and reverse flow power to the power grid is minimized.

[0007] According to the present disclosure, it is possible to operate a fuel cell so as to suppress reverse flow power and purchased power while suppressing deterioration of the fuel cell.

[0008] Fig. 1 is a diagram illustrating an example of the overall configuration of a power control system according to the present embodiment. Fig. 2 is a diagram illustrating the configuration of a control device according to the present embodiment. Fig. 3 is a flowchart illustrating control processing of a power system by a control device according to an embodiment of the present disclosure. Fig. 4 is a flowchart illustrating control processing of a power system by a control device according to a modified example of an embodiment of the present disclosure.

[0009] (Knowledge forming the basis of the present disclosure) There has been a desire to satisfy power demand by controlling a fuel cell system, a solar power generation system, and a storage battery. The power supply system of the above-mentioned Patent Document 1 includes a fuel cell, a storage battery, a power generation unit capable of generating power using natural energy, and a control unit capable of controlling the operation of the fuel cell, and the control unit switches the fuel cell from a power generation state to a standby state when predetermined conditions set in accordance with the power purchase and sale are met. The predetermined conditions include whether the storage battery is in a discharging state, whether the power generation cost of the fuel cell is lower than the power purchase cost of the grid power supply, whether the storage battery has a remaining charge sufficient to allow discharge, and whether the power generated by the power generation unit sold to the grid power supply is greater than the power generated by the fuel cell.

[0010] Frequent standby and restart cycles of a fuel cell place excessive strain on the stack, and therefore, repeated restarts of a fuel cell are undesirable from the standpoint of durability of the fuel cell. Conventional power supply systems are set to limit restarts of a fuel cell to once a day.

[0011] In this way, conventional technology suppresses fuel cell degradation by limiting the number of times the fuel cell is restarted, but does not take into consideration the suppression of reverse flow power and purchased power, making it difficult to solve the problem of operating a fuel cell in a way that suppresses reverse flow power and purchased power while suppressing fuel cell degradation.

[0012] In order to solve the above problems, the following techniques are disclosed.

[0013] (1) A control method for a power system according to one aspect of the present disclosure is a control method for a power system in a computer, and includes determining the future power generation power of the fuel cell system based on a predicted value of power demand and a predicted value of power generation power of a power generation system that uses natural energy, so that the sum of fluctuations in the power generation power of the fuel cell system, power purchased from the power grid, and reverse flow power to the power grid is minimized.

[0014] With this configuration, the future power generation of the fuel cell system is determined so that the sum of fluctuations in the power generation of the fuel cell system, the power purchased from the power grid, and the reverse flow power to the power grid is minimized. This minimizes fluctuations in the power generation of the fuel cell system, thereby suppressing fuel cell degradation. Furthermore, since the reverse flow power to the power grid is minimized and the power purchased from the power grid is also minimized, the reverse flow power and purchased power can be suppressed. Therefore, the fuel cell can be operated to suppress reverse flow power and purchased power while suppressing fuel cell degradation.

[0015] (2) The power system control method described in (1) above may further include acquiring an actual value of the power demand during a first period and an actual value of the power generated by the power generation system, and calculating a predicted value of the power demand during a second period after the first period based on the actual value of the power demand during the first period, and calculating a predicted value of the power generated by the power generation system during the second period based on the actual value of the power generated by the power generation system during the first period, wherein determining the generated power may include determining the power generated by the fuel cell system during the second period.

[0016] With this configuration, a predicted value of power demand for a second period after the first period can be calculated based on the actual value of power demand for the first period, and a predicted value of power generation by the power generation system for the second period can be calculated based on the actual value of power generation by the power generation system for the first period.

[0017] (3) In the power system control method described in (1) or (2) above, the determination of the generated power may include multiplying at least one of the fluctuation in the generated power of the fuel cell system, the purchased power from the power grid, and the reverse flow power to the power grid by a coefficient.

[0018] According to this configuration, for example, by multiplying the fluctuations in the power generated by the fuel cell system by a positive coefficient smaller than 1, it is possible to determine the power generated by the fuel cell system in the second period by prioritizing suppression of purchased power and reverse flow power over suppression of deterioration of the fuel cell system. Also, by multiplying the fluctuations in the power generated by the fuel cell system by a positive coefficient greater than 1, it is possible to determine the power generated by the fuel cell system in the second period by prioritizing suppression of deterioration of the fuel cell system over suppression of purchased power and reverse flow power.

[0019] (4) In the power system control method described in any one of (1) to (3) above, the determination of the generated power may further include summing up the storage capacities of the battery storage systems.

[0020] If the actual power generated by the photovoltaic power generation system is greater than the predicted value, the storage capacity of the storage battery may become fully charged, which may increase the reverse flow power. Therefore, by reducing the storage capacity of the storage battery system, even if the actual power generated by the photovoltaic power generation system is greater than the predicted value, the surplus generated power is charged to the storage battery, thereby preventing an increase in reverse flow power.

[0021] (5) In the power system control method described in (4) above, the determination of the generated power may include multiplying the storage capacity of the battery system by a coefficient.

[0022] With this configuration, the power generated by the fuel cell system during the second period can be determined by taking into consideration the balance between the storage capacity of the battery system, fluctuations in the power generated by the fuel cell system, power purchased from the power grid, and reverse flow power to the power grid.

[0023] (6) In the control method for a power system described in any one of (1) to (5) above, the determination of the generated power may include satisfying a constraint that the purchased power from the power grid is equal to or greater than the value obtained by multiplying the predicted value of the power demand by a power purchase target rate.

[0024] With this configuration, a predetermined percentage of the power demand is covered by the power purchased from the power grid. As a result, even if the actual power generated by the photovoltaic power generation system is greater than the predicted value, the power purchased can be reduced so that the surplus power generated can be consumed by the load, preventing an increase in reverse flow power.

[0025] (7) The power system control method described in (6) above may further include acquiring an actual value of the reverse flow power to the power grid during a first period, and changing the target power purchase rate according to the actual value of the reverse flow power.

[0026] According to this configuration, the target power purchase rate is changed in accordance with the actual value of the backward flow power in the first period, so that the backward flow power can be suppressed more reliably.

[0027] (8) In the control method for a power system described in (7) above, changing the target power purchase rate may include increasing the target power purchase rate when the actual value of the reverse flow power is equal to or greater than a threshold value, and decreasing the target power purchase rate when the actual value of the reverse flow power is smaller than the threshold value.

[0028] According to this configuration, when the actual value of the reverse flow power increases, the target power purchase rate is also increased, thereby making it possible to suppress the reverse flow power in the second period. When the actual value of the reverse flow power decreases, the target power purchase rate is also decreased, thereby making it possible to suppress the power purchase in the second period.

[0029] (9) The power system control method described in any one of (1) to (8) above may further include outputting a command to control the fuel cell system so as to output the determined generated power.

[0030] According to this configuration, the fuel cell system can be controlled so as to output the determined generated power.

[0031] (10) In the power system control method described in any one of (1) to (9) above, the power generation system may be a solar power generation system.

[0032] According to this configuration, a solar power generation system can be used as a power generation system that utilizes natural energy.

[0033] Furthermore, the present disclosure can be realized not only as a power system control method that executes the above-described characteristic processes, but also as a power system control device or the like that has a characteristic configuration corresponding to the characteristic processes executed by the power system control method. Furthermore, the present disclosure can also be realized as a computer program that causes a computer to execute the characteristic processes included in such a power system control method. Therefore, the following other aspects can also achieve the same effects as the above-described power system control method.

[0034] (11) A control device for a power system according to another aspect of the present disclosure includes a determination unit that determines the future power generation power of the fuel cell system based on a predicted value of power demand and a predicted value of power generation power of a power generation system that uses natural energy, so that the sum of fluctuations in the power generation power of the fuel cell system, power purchased from the power grid, and reverse flow power to the power grid is minimized.

[0035] (12) A control program for a power system according to another aspect of the present disclosure causes a computer to function to determine the future power generation of the fuel cell system based on a predicted value of power demand and a predicted value of power generation of a power generation system that uses natural energy, so that the sum of fluctuations in the power generation of the fuel cell system, power purchased from the power grid, and reverse flow power to the power grid is minimized.

[0036] (13) A non-transitory computer-readable recording medium according to another aspect of the present disclosure records a control program for a power system, and the control program causes a computer to function to determine the future power generation of the fuel cell system based on a predicted value of power demand and a predicted value of power generation of a power generation system that uses natural energy, so that the sum of fluctuations in the power generation of the fuel cell system, power purchased from the power grid, and reverse flow power to the power grid is minimized.

[0037] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. The numerical values, shapes, components, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept are described as optional components. Furthermore, in all embodiments, the respective contents can be combined.

[0038] 1 is a diagram showing an example of the overall configuration of a power control system according to the present embodiment. In FIG. 1, power lines are shown by solid lines, and communication lines are shown by dashed lines.

[0039] The power control system in this embodiment includes a power system 200 and a control device 10 that controls the power system 200 .

[0040] The power system 200 in this embodiment is connected to the power grid 100 and the load 301 via power lines. The power system 200 supplies power to the load 301. The power grid 100 has a function of supplying system power, and is connected to the load 301 via power lines.

[0041] Grid power is also called commercial power, and is, for example, 50 Hz or 60 Hz AC power. Therefore, if the power supplied from the power system 200 is insufficient for the power consumed by the load 301, the power system 100 supplies the shortfall to the load 301. In other words, the shortfall is purchased as purchased power. On the other hand, if the power supplied from the power system 200 is in excess of the power consumed by the load 301, the surplus power is taken over by the power system 100, that is, the surplus power is sold as reverse flow power. In this embodiment, the load 301 is made up of one or more appliances or devices that consume power. The power consumed by the load 301 is also called power demand. A power consumer such as a factory or facility is provided with the load 301.

[0042] The power system 200 includes a solar power generation system 201 , a fuel cell system 202 , and a storage battery system 203 .

[0043] The solar power generation system 201 includes a first controller 210, a solar power generation device 211, a first PCS (Power Conditioning System) 212, and a first wattmeter 213. The solar power generation system 201 is an example of a power generation system that uses natural energy.

[0044] The photovoltaic power generation device 211 has, for example, one or more photovoltaic power generation units, and converts sunlight into electrical power through photoelectric conversion and outputs the electrical power. The photovoltaic power generation units are, for example, photovoltaic power generation panels. Hereinafter, the photovoltaic power generation device 211 will also be simply referred to as a solar cell. The first PCS 212 converts the electrical power output from the photovoltaic power generation device 211 into electrical power of the same quality as grid power and outputs the electrical power. The first wattmeter 213 measures the electrical power output from the photovoltaic power generation device 211 via the first PCS 212, i.e., the grid power, and outputs a signal indicating the measured electrical power to the control device 10. The first controller 210 controls the photovoltaic power generation device 211 and the first PCS 212. For example, the first controller 210 controls the photovoltaic power generation device 211 and the first PCS 212 in response to a command from the control device 10.

[0045] The fuel cell system 202 includes a second controller 220 , a fuel cell power generation device 221 , a second PCS 222 , and a second power meter 223 .

[0046] The fuel cell power generation system 221 has, for example, one or more fuel cell units and generates electricity by chemically reacting hydrogen and oxygen. The hydrogen source used for power generation is, for example, a hydrogen storage tank or a hydrogen infrastructure. The fuel cell unit is, for example, a fuel cell stack device. Note that the fuel cell power generation system 221 will also be simply referred to as a fuel cell hereinafter. The second PCS 222 converts the power output by the fuel cell power generation system 221 into power of the same quality as grid power and outputs the converted power. The second power meter 223 measures the power output from the fuel cell power generation system 221 via the second PCS 222, i.e., grid power, and outputs a signal indicating the measured power to the control device 10. The second controller 220 controls the fuel cell power generation system 221 and the second PCS 222. For example, the second controller 220 adjusts the power output from the fuel cell power generation system 221 and the second PCS 222 in response to commands from the control device 10.

[0047] The storage battery system 203 includes a third controller 230 , a storage battery device 231 , a third PCS 232 , and a third wattmeter 233 .

[0048] The storage battery equipment 231 has, for example, one or more storage battery units and performs charging or discharging. The storage battery units are, for example, storage battery packs. The storage battery equipment 231 will also be simply referred to as a storage battery hereinafter. The third PCS 232 converts power output by discharging the storage battery equipment 231 into power of the same quality as grid power and outputs the power. Alternatively, the third PCS 232 converts grid power and charges the storage battery equipment 231. The third wattmeter 233 measures the power output from the storage battery equipment 231 via the third PCS 232, i.e., grid power, and outputs a signal indicating the measured power to the control device 10. The third wattmeter 233 also measures the power output from the solar power generation equipment 211 or the fuel cell power generation equipment 221 and charged to the storage battery equipment 231, and outputs a signal indicating the measured power to the control device 10. The third controller 230 controls the storage battery equipment 231 and the third PCS 232. For example, the third controller 230 adjusts the power discharged from the storage battery device 231 or the power charged to the storage battery device 231 in response to a command from the control device 10 .

[0049] The control device 10 in this embodiment is a control device for the power system 200, and is connected to the fourth power meter 303, the power system 200, and the database 20 via communication lines. That is, the control device 10 communicates with each of the fourth power meter 303, the power system 200, and the database 20 via the communication lines. Note that in this embodiment, the power that is notified, transmitted, instructed, acquired, or received via the communication lines is not the power itself, but data indicating the magnitude of the power, for example, wattage. Furthermore, the fourth power meter 303 measures the power consumption of the load 301.

[0050] The control device 10 receives, from each of the first wattmeter 213, the second wattmeter 223, the third wattmeter 233, and the fourth wattmeter 303, a signal indicating the power measured by that wattmeter at each sampling period. The control device 10 then writes the power indicated by these signals into the database 20. Furthermore, the control device 10 receives, from the third controller 230, a signal indicating the SOC (State of Charge) of the storage battery device 231 at each sampling period, and writes the SOC into the database 20. Specific examples of the sampling period include, but are not limited to, 30 seconds or 1 minute. The SOC of the storage battery device 231 is the charge capacity of the storage battery device 231 and is hereinafter also referred to as the storage battery SOC.

[0051] The database 20 is a recording medium for recording the actual power values, the storage battery SOC, and the like. The recording medium is a hard disk drive, a RAM (Random Access Memory), a ROM (Read Only Memory), a semiconductor memory, or the like. The recording medium may be volatile or non-volatile. In the present embodiment, the database 20 is not provided in the control device 10, but may be provided in the control device 10.

[0052] The power consumption of the load 301 is the power measured by the fourth power meter 303. The power generated by the solar power generation device 211 is the power output from the solar power generation device 211 via the first PCS 212 and is measured by the first power meter 213. Such power generated by the solar power generation device 211 can also be said to be the output of the solar power generation system 201 or the solar power generation device 211. Similarly, the power generated by the fuel cell power generation device 221 is the power output from the fuel cell power generation device 221 via the second PCS 222 and is measured by the second power meter 223. Such power generated by the fuel cell power generation device 221 can also be said to be the output of the fuel cell system 202 or the fuel cell power generation device 221.

[0053] When reverse flow power occurs, it is assumed that surplus power is generated by the photovoltaic power generation system 201 and that this surplus power is flowing back into the power grid. In such a case, it may be desirable to reduce the power generated by the fuel cell system 202 from the viewpoint of improving the self-consumption rate of the power generated by the photovoltaic power generation system 201.

[0054] Furthermore, if the power generated by the fuel cell system 202 is reduced, there is a possibility that power will be purchased from the power grid 100. In this way, if power is purchased from the power grid 100 as a result of reducing the power generated by the fuel cell system 202, this is undesirable from the perspective of utility costs.

[0055] FIG. 2 is a diagram showing the configuration of the control device 10 in this embodiment.

[0056] The control device 10 includes at least a computer system including, for example, a control program, a processing circuit such as a processor or logic circuit that executes the control program, and a recording device such as an internal memory or an accessible external memory that stores the control program. Note that the control device 10 may be realized, for example, by hardware implementation using the processing circuit, or by execution of a software program stored in the memory by the processing circuit or distributed from an external server, or by a combination of these hardware and software implementations.

[0057] The control device 10 includes a data acquisition unit 11 , a performance value acquisition unit 12 , a prediction unit 13 , a determination unit 14 , and an output unit 15 .

[0058] The data acquisition unit 11 acquires signals indicating four power levels from the fourth power meter 303, the first power meter 213, the second power meter 223, and the third power meter 233 at each sampling period. The data acquisition unit 11 then writes the numerical values ​​of each of the four power levels into the database 20 as actual values. The four power levels are the power consumption (power demand) of the load 301, the power generated by the solar power generation system 211, the power generated by the fuel cell power generation system 221, and the discharge power or charge power of the storage battery system 231. The discharge power and charge power are collectively referred to as charge / discharge power. Furthermore, the data acquisition unit 11 acquires a signal indicating the storage battery SOC from the third controller 230 at each sampling period, along with the signals indicating the four power levels. The data acquisition unit 11 then writes the storage battery SOC into the database 20 as an actual value.

[0059] In this embodiment, the discharge power of the storage battery device 231 is the power discharged from the storage battery device 231 via the third PCS 232 and is the power measured by the third wattmeter 233. Similarly, the charge power of the storage battery device 231 in this embodiment is the power charged to the storage battery device 231 via the third PCS 232 from the solar power generation device 211, the fuel cell power generation device 221, or the like and is the power measured by the third wattmeter 233.

[0060] The actual value acquiring unit 12 acquires the actual value of the power demand and the actual value of the power generated by the photovoltaic power generation system 201 during the first period.

[0061] The actual value acquiring unit 12 acquires actual values ​​for each of a plurality of unit times that divide the first period. The first period is a period during which the actual value acquiring unit 12 acquires actual values ​​of power demand and actual values ​​of power generated by the photovoltaic power generation system 201. The first period is, for example, 24 hours. However, this is just an example, and an appropriate value such as 48 hours, 12 hours, or 36 hours can be used for the first period. A unit time is a time obtained by dividing the first period into predetermined time intervals. Examples of a unit time are 1 hour, 2 hours, or 30 minutes. Therefore, if the unit time is 1 hour, actual values ​​are acquired for each hour.

[0062] The actual value acquiring unit 12 reads out the actual value of the power demand for each unit time in the first period from the database 20. The actual value acquiring unit 12 also reads out the actual value of the power generated by the photovoltaic power generation system 201 for each unit time in the first period from the database 20.

[0063] The prediction unit 13 calculates a predicted value of power demand in a second period after the first period based on an actual value of power demand in the first period. The prediction unit 13 also calculates a predicted value of power generation by the photovoltaic power generation system 201 in the second period based on an actual value of power generation by the photovoltaic power generation system 201 in the first period.

[0064] The prediction unit 13 calculates a predicted value for each of a plurality of unit times that divide the second period. The second period is a period during which the prediction unit 13 predicts a predicted value of power demand and a predicted value of power generation by the photovoltaic power generation system 201. The second period is, for example, 24 hours. However, this is just one example, and an appropriate value such as 48 hours, 12 hours, or 36 hours can be used for the second period. A unit time is a time obtained by dividing the second period into predetermined time intervals. Examples of a unit time are 1 hour, 2 hours, or 30 minutes. Therefore, if the unit time is 1 hour, a predicted value is calculated for each hour.

[0065] The actual value acquiring unit 12 may further acquire days of the week in the second period and forecast values ​​of weather information for each unit time in the second period. The weather information includes at least one of temperature, humidity, precipitation, and weather around the power consumer. The actual value acquiring unit 12 may acquire the forecast values ​​of weather information from a weather information server connected via a network, for example.

[0066] The prediction unit 13 pre-stores a first prediction model for predicting the power demand in the second period, and pre-stores a second prediction model for predicting the power generated by the solar power generation system 201 in the second period.

[0067] The prediction unit 13 calculates a predicted value of power demand per unit time in the second period by inputting the actual value of power demand per unit time in the first period and the day of the week in the second period into a first prediction model.

[0068] The first prediction model is a model obtained by machine learning learning data in which the actual value of power demand before the reference time point and the day of the week after the reference time point are used as explanatory variables, and the actual value of power demand after the reference time point corresponding to the explanatory variables is used as the objective variable. The reference time point refers to the point in time that is the starting point of the second period set during learning. The actual value of power demand after the reference time point corresponding to the explanatory variables is the actual value of power demand during the second period set during learning. The first prediction model is machine-learned to minimize the error between the predicted value of power demand per unit time that is output when the explanatory variables are input and the actual value of power demand per unit time during the second period, which is the objective variable corresponding to the input explanatory variables.

[0069] In addition, the prediction unit 13 calculates a predicted value of the power generated by the solar power generation system 201 for each unit time in the second period by inputting the actual value of the power generated by the solar power generation system 201 for each unit time in the first period and the forecast value of the weather information for each unit time in the second period into a second prediction model.

[0070] The second prediction model is a model obtained by machine learning learning data in which the actual value of the power generated by the photovoltaic power generation system before the reference time point and the forecast value of weather information after the reference time point are used as explanatory variables, and the actual value of the power generated by the photovoltaic power generation system after the reference time point corresponding to the explanatory variables is used as the objective variable. The reference time point refers to the point in time that is the starting point of the second period set during learning. The actual value of the power generated by the photovoltaic power generation system after the reference time point corresponding to the explanatory variables is the actual value of the power generated by the photovoltaic power generation system during the second period set during learning. The second prediction model is machine-learned to minimize the error between the predicted value of the power generated by the photovoltaic power generation system per unit time that is output when the explanatory variables are input and the actual value of the power generated by the photovoltaic power generation system per unit time during the second period, which is the objective variable corresponding to the input explanatory variables.

[0071] The machine learning models used by the first prediction model and the second prediction model may be any appropriate model, such as a random forest, a LightGBM, or a deep neural network.

[0072] The determination unit 14 determines the future power generation power of the fuel cell system 202 based on the predicted value of power demand and the predicted value of power generation by the photovoltaic power generation system 201 so that the sum of fluctuations in the power generation power of the fuel cell system 202, the power purchased from the power grid 100, and the reverse flow power to the power grid 100 is in a minimum range (in other words, so that the sum is a value within an allowable range including the minimum value). The minimum range is a range near the minimum value including the minimum value of the sum, and if the sum is a value within this minimum range, fluctuations in the power purchased, the reverse flow power, and the power generation power of the fuel cell are suppressed. Furthermore, the minimum range is, for example, a range including the minimum value and approximately 10% above the minimum value.

[0073] The determination unit 14 determines the power generated by the fuel cell system 202 per unit time in the second period based on the predicted value of power demand per unit time in the second period and the predicted value of power generated by the solar power generation system 201 per unit time in the second period so that the sum of the fluctuation in the power generated by the fuel cell system 202 per unit time in the second period, the power purchased from the power system 100 per unit time in the second period, and the reverse flow power to the power system 100 per unit time in the second period is within a minimum range.

[0074] The determination unit 14 uses a mixed integer programming solver to solve an optimization problem, thereby determining the power generation amount of the fuel cell system 202. The determination unit 14 may also use a local search such as a hill climbing method, a simulated annealing method, or a genetic algorithm.

[0075] The constraints of the optimization problem are expressed by the following equations (1) to (8).

[0076] bt ｉ +fc ｉ +gr ｉ ｉｎ -gr ｉ ｏｕｔ = d ｉ ... (1) -BTPOWMAX≦bt ｉ ≦BTPOWMAX...(2) 0≦gr ｉ ｉｎ , gr ｉ ｏｕｔ , fc ｉ , gｉ ... (3) fc ｉ ≦FCMAX (4) 0≦soc ｉ ≦BTCAPMAX...(5) -g ｉ ≦f.c. ｉ -fc ｉ－１ ≦g ｉ where i = 2, ..., 24... (6) -g １ ≦f.c. １ -FCINIT≦g １ ... (7)

[0077]

[0078] The objective function of the optimization problem is expressed by the following equation (9).

[0079]

[0080] i is an index for identifying a unit time in the second period. For example, if the second period is 24 hours and the unit time is 1 hour, i is 1, . . . , 24.

[0081] d ｉ represents the value obtained by subtracting the predicted value (kW) of the power generation power of the photovoltaic power generation system 201 from the predicted value (kW) of the power demand. ｉ is a value per unit time in the second period.

[0082] BTCAPMAX represents the maximum storage capacity (kWh) of the storage battery system 203. BTCAPINIT represents the initial storage capacity (kWh) of the storage battery system 203. BTPOWMAX represents the maximum discharge power (kW) of the storage battery system 203. FCMAX represents the maximum generated power (kW) of the fuel cell system 202. FCINIT represents the initial generated power (kW) of the fuel cell system 202. The maximum storage capacity BTCAPMAX, the initial storage capacity BTCAPINIT, the maximum discharge power BTPOWMAX, the maximum generated power FCMAX, and the initial generated power FCINIT are stored in the database 20. In addition, a plurality of variables, a plurality of constraints, and an objective function are stored in the database 20.

[0083] bt ｉis a variable representing the discharge power (kW) of the battery system 203. ｉ is a variable representing the power generation (kW) of the fuel cell system 202. ｉ ｉｎ is a variable representing the purchased power (kW) supplied from the power grid 100. ｉ ｏｕｔ is a variable representing the reverse flow power (kW) supplied to the power system 100. ｉ is a variable representing the storage capacity (kWh) of the battery system 203. ｉ is a variable that represents the fluctuation (kWh) of the power generated by the fuel cell system 202 from the previous unit time (g ｉ = fc ｉ -fc ｉ－１ ).

[0084] The constraint equation (1) specifies that the balance between the supply and demand of electric power must be satisfied. That is, the value d obtained by subtracting the predicted value of the power generated by the photovoltaic power generation system 201 from the predicted value of the power demand is ｉ is the discharge power bt of the storage battery system 203 ｉ and the power generated by the fuel cell system 202 fc ｉ and the purchased power gr supplied from the power system 100 ｉ ｉｎ The reverse flow power gr supplied to the power system 100 is calculated from the sum of ｉ ｏｕｔ must be equal to the value obtained by subtracting

[0085] Furthermore, the constraint equation (2) is the discharge power bt ｉ In other words, the upper limit (BTPOWMAX) and lower limit (-BTPOWMAX) of the discharge power bt ｉ must be in the range between the lower limit (-BTPOWMAX) and the upper limit (BTPOWMAX).

[0086] Furthermore, the constraint equation (3) is the purchased power gr ｉ ｉｎ , reverse flow power gr ｉ ｏｕｔ , the power generated by the fuel cell system 202 fc ｉ, and fluctuation g of the power generated by the fuel cell system 202 ｉ is a positive value. ｉ ｉｎ , reverse flow power gr ｉ ｏｕｔ , the power generated by the fuel cell system 202 fc ｉ , and fluctuation g of the power generated by the fuel cell system 202 ｉ must be a positive value.

[0087] Furthermore, the constraint equation (4) is the power generation fc of the fuel cell system 202. ｉ In other words, the upper limit value (FCMAX) of the power generation power fc of the fuel cell system 202 is defined. ｉ must be equal to or less than the upper limit (FCMAX).

[0088] Furthermore, the constraint equation (5) is the storage capacity soc of the storage battery system 203. ｉ is defined to be in the range from 0 to the maximum storage capacity. ｉ must be in the range between 0 and the maximum storage capacity.

[0089] Furthermore, the constraint equation (6) is the fluctuation g when the unit time i is 2, ..., 24. ｉ The constraint equation (7) defines the fluctuation g when the unit time i is 1. １ That is, when the unit time i is 2 to 24, the fluctuation g ｉ is the power generated by the fuel cell system 202 in unit time i, fc ｉ From the previous unit time i-1, the power generation power fc ｉ－１ In addition, when the unit time i is 1, the fluctuation g １ is the power generated by the fuel cell system 202 fc １ The value must be obtained by subtracting the initial power generation power (FCINIT) of the fuel cell system 202 from the above.

[0090] Furthermore, the constraint equation (8) is the storage capacity soc of the storage battery system 203. ｉis the discharge power bt from the initial storage capacity (BTCAPINIT) at each unit time i ｉ That is, the storage capacity soc of the storage battery system 203 is specified to be a value obtained by subtracting the sum of ｉ is the discharge power bt from the initial storage capacity (BTCAPINIT) at each unit time i ｉ The value must be the sum of the above.

[0091] The objective function is the purchased power gr ｉ ｉｎ and reverse flow power gr ｉ ｏｕｔ and fluctuation g of the power generated by the fuel cell system 202 ｉ is a function that minimizes the sum of

[0092] The determination unit 14 inputs the above-described multiple variables, multiple constraint conditions, and objective function into the mixed integer programming solver to calculate values ​​of the multiple variables that satisfy the multiple constraint conditions and minimize the objective function. As a result, the determination unit 14 calculates the power generation fc of the fuel cell system 202 per unit time in the second period. ｉ From the above, the power generation amount of the fuel cell system 202 is planned.

[0093] The output unit 15 outputs a command to the power system 200 to control the fuel cell system 202 so as to output the generated power determined by the determination unit 14. The output unit 15 outputs the generated power fc per unit time in the second period. ｉ When the command is input from the control device 10, the second controller 220 of the fuel cell system 202 outputs a command to the fuel cell system 202 of the power system 200 to control the fuel cell system 202 to output the generated power fc １ The fuel cell power generation device 221 is controlled so that the power generated is:

[0094] The output unit 15 outputs a command to the second controller 220 via a communication line to control the power generation of the fuel cell. The second controller 220 controls the fuel cell power generation device 221 and the second PCS 222 in accordance with the command from the output unit 15.

[0095] The control device 10 controls the fuel cell power generator 221 and the second PCS 222 via the second controller 220 so that the determined power generated by the fuel cell power generator 221 is output during the second period.

[0096] Furthermore, when the fuel cell power generation system 221 is generating the determined power during the second period, the control device 10 controls the storage battery device 231 and the third PCS 232 via the third controller 230. Specifically, when the sum of the power generated by the solar power generation system 211 and the power generated by the fuel cell power generation system 221 is greater than the power consumption of the load 301, the control device 10 causes the storage battery device 231 to charge. On the other hand, when the sum is smaller than the power consumption, the control device 10 causes the storage battery device 231 to discharge so as to satisfy the power consumption D.

[0097] Next, a control process of the power system 200 performed by the control device 10 according to the embodiment of the present disclosure will be described.

[0098] 3 is a flowchart illustrating the control process of the power system 200 by the control device 10 according to the embodiment of the present disclosure. This flowchart is started, for example, at a predetermined planning point in time. For example, the planning point in time may be midnight, and the control process may be executed at midnight every day. In this case, the period from midnight to the time 24 hours ago may be defined as a first period, and the period from midnight to the time 24 hours later may be defined as a second period, and the power generated by the fuel cell system 202 for the second period may be determined. This flowchart may be executed every 24 hours. Alternatively, this flowchart may be executed every hour.

[0099] First, in step S1, the actual value acquiring unit 12 acquires the actual value of the power demand and the actual value of the power generated by the photovoltaic power generation system 201 in a first period.

[0100] Next, in step S2, the prediction unit 13 calculates a predicted value of power demand in the second period based on the actual value of power demand in the first period, and calculates a predicted value of power generation by the solar power generation system 201 in the second period based on the actual value of power generation by the solar power generation system 201 in the first period.

[0101] Next, in step S3, the determination unit 14 determines the power generated by the fuel cell system 202 in the second period based on the predicted value of the power demand and the predicted value of the power generated by the photovoltaic power generation system 201 so that the sum of the fluctuation in the power generated by the fuel cell system 202, the power purchased from the power grid 100, and the reverse flow power to the power grid 100 is in a minimum range. At this time, the determination unit 14 determines the power generated by the fuel cell system 202 per unit time in the second period fc so that the constraint conditions shown in equations (1) to (8) are satisfied and the objective function shown in equation (9) is in a minimum range. ｉ Determine.

[0102] Next, in step S4 , the output unit 15 outputs to the power system 200 a command to control the fuel cell system 202 so as to output the generated power for the second period determined by the determination unit 14 .

[0103] In this way, the power generated by the fuel cell system 202 in the second period is determined so that the sum of the fluctuations in the power generated by the fuel cell system 202, the power purchased from the power grid 100, and the reverse flow power to the power grid 100 is in a minimum range. As a result, the fluctuations in the power generated by the fuel cell system 202 are in a minimum range, and deterioration of the fuel cell can be suppressed. Furthermore, the reverse flow power to the power grid 100 is in a minimum range, and the power purchased from the power grid 100 is also in a minimum range, so that the reverse flow power and purchased power can be suppressed. Therefore, the fuel cell can be operated so as to suppress the reverse flow power and purchased power while suppressing deterioration of the fuel cell.

[0104] In this embodiment, the determination unit 14 determines the fluctuation g of the power generated by the fuel cell system 202. ｉ and purchased power gr from the power grid 100 ｉ ｉｎand the reverse flow power gr to the power system 100 ｉ ｏｕｔ In other words, the determination unit 14 may multiply at least one of the fluctuation g of the power generated by the fuel cell system 202 per unit time in the second period by a coefficient. ｉ The value obtained by multiplying this by the first coefficient and the purchased power gr from the power system 100 per unit time in the second period ｉ ｉｎ and the reverse flow power gr to the power system 100 per unit time in the second period ｉ ｏｕｔ The power generation power of the fuel cell system 202 in the second period may be determined so that the sum of is in a minimum range (in other words, so that the sum is within an allowable range including the minimum value). The minimum range is, for example, a range including the minimum value and about 10% above the minimum value. The first coefficient is, for example, 0.01. In this case, the objective function is expressed by the following equation (10).

[0105]

[0106] A positive first coefficient smaller than 1 is a fluctuation g of the power generated by the fuel cell system 202. ｉ By multiplying this by the purchased power gr ｉ ｉｎ and reverse flow power gr ｉ ｏｕｔ In addition, the first coefficient, which is positive and greater than 1, can be used to determine the power generated by the fuel cell system 202 by placing more importance on suppressing the fluctuation g ｉ By multiplying the power generation amount by , it is possible to determine the power generation amount of the fuel cell system 202 with greater emphasis on suppressing deterioration of the fuel cell system 202.

[0107] In the formula (10), the first coefficient is the fluctuation g of the power generated by the fuel cell system 202. ｉ However, the present disclosure is not particularly limited to this, and the first coefficient is multiplied by the purchased power gr ｉ ｉｎ and reverse flow power gr ｉ ｏｕｔ The first coefficient may be a positive value smaller than 1 or may be a positive value equal to or greater than 1.

[0108] The first coefficient is the fluctuation g of the power generated by the fuel cell system 202. ｉ , purchased power gr ｉ ｉｎ , and reverse flow power gr ｉ ｏｕｔ In this case, the first coefficients by which each of the above is multiplied may all be the same, may all be different, or may be partly the same.

[0109] The determination unit 14 may further sum up the storage capacities of the storage battery systems 203. That is, the determination unit 14 may further sum up the fluctuation g of the power generated by the fuel cell system 202 per unit time during the second period. ｉ and the purchased power gr from the power system 100 per unit time in the second period ｉ ｉｎ and the reverse flow power gr to the power system 100 per unit time in the second period ｉ ｏｕｔ and the storage capacity soc of the storage battery system 203 per unit time during the second period ｉ The power generation amount of the fuel cell system 202 per unit time in the second time period may be determined so that the sum of (a) and (b) is within a minimum range (in other words, so that the sum is within an allowable range including the minimum value). The minimum range is, for example, a range including the minimum value and about 10% above the minimum value.

[0110] The determination unit 14 may also multiply the storage capacity of the battery system 203 by a coefficient. That is, the determination unit 14 determines the fluctuation g of the power generated by the fuel cell system 202 per unit time in the second period. ｉ and the purchased power gr from the power system 100 per unit time in the second period ｉ ｉｎ and the reverse flow power gr to the power system 100 per unit time in the second period ｉ ｏｕｔ and the storage capacity soc of the storage battery system 203 per unit time during the second period ｉThe power generation power of the fuel cell system 202 per unit time in the second period may be determined so that the sum of the value obtained by multiplying the first coefficient by the second coefficient falls within a minimum range (in other words, so that the sum falls within an allowable range including the minimum value). The minimum range is, for example, a range including the minimum value and approximately 10% above the minimum value. The second coefficient is, for example, 0.00001. In this case, the objective function is expressed by the following equation (11):

[0111]

[0112] In the above equation (11), the first coefficient is the fluctuation g of the power generated by the fuel cell system 202. ｉ It is hung on.

[0113] If the actual power generated by the photovoltaic power generation system 201 becomes greater than the predicted value, the storage capacity of the storage battery may become fully charged, which may result in an increase in reverse flow power. Therefore, by setting the storage capacity of the storage battery system 203 to the minimum range, even if the actual power generated by the photovoltaic power generation system 201 becomes greater than the predicted value, the surplus generated power is charged to the storage battery, thereby preventing an increase in reverse flow power. Note that the second coefficient may be any value as long as it is a positive value smaller than 1.

[0114] Furthermore, in this embodiment, the determination unit 14 may further add a constraint that the amount of power purchased from the power grid 100 is equal to or greater than the value obtained by multiplying the predicted value of power demand by the target power purchase rate. That is, the constraints of the optimization problem may further include a constraint expressed by the following equation (12).

[0115] gr ｉ ｉｎ ≧Electricity demand ｉ *β (12) β represents the target power purchase rate by which the predicted value of power demand is multiplied. The target power purchase rate is a positive value smaller than 1. The constraint equation (12) is ｉ ｉｎ is specified to be equal to or greater than a predetermined percentage of the predicted value of the power demand. ｉ ｉｎ must be equal to or greater than the value obtained by multiplying the predicted value of the power demand for unit time i by the target power purchase rate β.

[0116] In this way, a predetermined proportion of the power demand is met by the power purchased from the power grid 100. As a result, even if the actual power generation of the photovoltaic power generation system 201 becomes greater than the predicted value, the surplus power generation can be consumed by the load 301 by reducing the power purchased, thereby preventing an increase in the reverse flow power.

[0117] Furthermore, in a modification of the present embodiment, the actual value acquiring unit 12 may acquire an actual value of the backward flow power to the power system 100 during the first time period. The actual value acquiring unit 12 may acquire an actual value of the backward flow power per unit time during the first time period. The control device 10 may further include a changing unit. The changing unit may change the power purchase target rate β according to the actual value of the backward flow power during the first time period.

[0118] More specifically, the change unit may increase the target power purchase rate β when the actual value of the backward flow power is equal to or greater than a threshold, and may decrease the target power purchase rate β when the actual value of the backward flow power is smaller than the threshold. ｉ ｏｕｔ is equal to or greater than the threshold, the current target power purchase rate β may be changed to the smaller value of β+0.1 or βmax, where βmax is the upper limit of the target power purchase rate β. ｉ ｏｕｔ is smaller than the threshold value, the current target power purchase rate β may be changed to the larger of β-0.1 and βmin. βmin is the lower limit of the target power purchase rate β. Note that the value to be added to or subtracted from the target power purchase rate β is not limited to 0.1, and may be any positive value smaller than 1.

[0119] FIG. 4 is a flowchart for illustrating a control process of the power system 200 by the control device 10 according to the modified example of the embodiment of the present disclosure.

[0120] First, in step S11, the actual value acquiring unit 12 acquires the actual value of the power demand, the actual value of the power generated by the photovoltaic power generation system 201, and the actual value of the backward flow power to the power grid 100 during the first period.

[0121] Next, in step S12, the change unit changes the target power purchase rate β for the second time period in accordance with the actual value of the backward flow power for the first time period. Note that the change unit changes the target power purchase rate β for each unit time for the second time period in accordance with the actual value of the backward flow power for each unit time for the first time period.

[0122] Next, in step S13, the prediction unit 13 calculates a predicted value of power demand in the second period based on the actual value of power demand in the first period, and calculates a predicted value of power generation by the solar power generation system 201 in the second period based on the actual value of power generation by the solar power generation system 201 in the first period.

[0123] Next, in step S14, the determination unit 14 determines the power generation power of the fuel cell system 202 in the second period based on the predicted value of the power demand and the predicted value of the power generation power of the photovoltaic power generation system 201 so that the sum of the fluctuation in the power generation power of the fuel cell system 202, the power purchased from the power grid 100, and the reverse flow power to the power grid 100 is in a minimum range. At this time, the determination unit 14 determines the power generation power fc of the fuel cell system 202 per unit time in the second period so that the constraints shown in equations (1) to (8) and (12) are satisfied and the objective function shown in equation (9) is in a minimum range. ｉ Determine.

[0124] Next, in step S15 , the output unit 15 outputs to the power system 200 a command to control the fuel cell system 202 so as to output the generated power for the second period determined by the determination unit 14 .

[0125] In this way, the target power purchase rate β is changed in accordance with the actual value of the backward flow power in the first period, so that the backward flow power can be suppressed more reliably.

[0126] The determination unit 14 may use charging or discharging of the storage battery to reduce the sum of fluctuations in the power generated by the fuel cell system, the power purchased from the power grid, and the reverse flow power to the power grid. For example, the determination unit 14 may use charging or discharging of the storage battery system to suppress fluctuations in the power generated by the fuel cell system. Specifically, when the difference between the predicted value of power demand and the predicted value of power generated by the power generation system using renewable energy fluctuates, the determination unit 14 may control the storage battery system to cover at least a portion of this fluctuation by charging or discharging. This suppresses fluctuations in the power generated by the fuel cell system.

[0127] Note that the control of covering at least a part of the fluctuation by charging or discharging the battery system is limited depending on the SOC of the storage battery. For example, when the SOC of the storage battery is higher than an upper limit that is lower than 100%, the control of covering at least a part of the fluctuation by charging the battery system is limited, and when the SOC of the storage battery is lower than a lower limit that is higher than 0%, the control of covering at least a part of the fluctuation by discharging the battery system is limited.

[0128] In each of the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. Furthermore, the program may be executed by another independent computer system by recording the program on a recording medium and transferring it, or by transferring the program via a network.

[0129] Some or all of the functions of the device according to the embodiment of the present disclosure are typically realized as an LSI (Large Scale Integration), which is an integrated circuit. These may be individually integrated into a single chip, or some or all of them may be integrated into a single chip. Furthermore, the integrated circuit is not limited to an LSI, and may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use an FPGA (Field Programmable Gate Array), which can be programmed after LSI manufacturing, or a reconfigurable processor, which can reconfigure the connections and settings of circuit cells within an LSI.

[0130] Furthermore, some or all of the functions of the device according to the embodiment of the present disclosure may be realized by a processor such as a CPU executing a program.

[0131] Furthermore, all the numbers used above are merely examples to specifically explain the present disclosure, and the present disclosure is not limited to the numbers used as examples.

[0132] The order in which the steps are executed in the above flowchart is merely an example for specifically explaining the present disclosure, and other orders may be used as long as similar effects are obtained. Also, some of the steps may be executed simultaneously (in parallel) with other steps.

[0133] The technology disclosed herein is useful as a technology for controlling a power system that supplies power, because it can operate a fuel cell so as to suppress reverse flow power and purchased power while suppressing deterioration of the fuel cell.

Claims

1. A method for controlling an electric power system in a computer, comprising determining the future power generation of a fuel cell system based on a predicted value of power demand and a predicted value of the power generation of a power generation system that utilizes natural energy, so that the sum of the fluctuations in the power generation of the fuel cell system, the power purchased from the power grid, and the reverse flow power to the power grid is minimized.

2. The method of controlling a power system as described in claim 1, further comprising: acquiring an actual value of the power demand during a first period and an actual value of the generated power of the power generation system; and calculating a predicted value of the power demand during a second period after the first period based on the actual value of the power demand during the first period, and calculating a predicted value of the generated power of the power generation system during the second period based on the actual value of the generated power of the power generation system during the first period, wherein determining the generated power includes determining the generated power of the fuel cell system during the second period.

3. The method of controlling a power system according to claim 1 or 2, wherein the determination of the generated power includes multiplying at least one of the fluctuation in the generated power of the fuel cell system, the purchased power from the power grid, and the reverse flow power to the power grid by a coefficient.

4. The method of controlling a power system according to claim 1 or 2, wherein the determination of the generated power further includes summing up the storage capacities of battery storage systems.

5. The method of controlling a power system according to claim 4, wherein the determination of the generated power includes multiplying the storage capacity of the battery storage system by a coefficient.

6. The method of controlling a power system according to claim 1 or 2, wherein the determination of the generated power includes satisfying a constraint that the purchased power from the power grid is equal to or greater than the predicted value of the power demand multiplied by a target power purchase rate.

7. The method for controlling a power system according to claim 6, further comprising: acquiring an actual value of the reverse flow power to the power grid in a first period; and changing the target power purchase rate in accordance with the actual value of the reverse flow power.

8. The control method for a power system according to claim 7, wherein changing the target power purchase rate includes increasing the target power purchase rate when the actual value of the reverse flow power is equal to or greater than a threshold value, and decreasing the target power purchase rate when the actual value of the reverse flow power is smaller than the threshold value.

9. The power system control method according to claim 1 or 2, further comprising outputting a command for controlling said fuel cell system so as to output said determined generated power.

10. The method of controlling a power system according to claim 1 or 2, wherein the power generation system is a solar power generation system.

11. A control device for a power system, comprising a determination unit that determines the future power generation of a fuel cell system based on a predicted value of power demand and a predicted value of the power generation of a power generation system that utilizes natural energy, so that the sum of the fluctuations in the power generation of the fuel cell system, the power purchased from the power grid, and the reverse flow power to the power grid is minimized.

12. A power system control program that causes a computer to determine the future power generation of a fuel cell system based on a predicted value of power demand and a predicted value of the power generation of a power generation system that utilizes natural energy, so that the sum of the fluctuations in the power generation of the fuel cell system, the power purchased from the power grid, and the reverse flow power to the power grid is minimized.