JP7481706B2 - ENERGY SUPPLY SYSTEM, CONTROL DEVICE FOR ENERGY SUPPLY SYSTEM, AND CONTROL METHOD FOR ENERGY SUPPLY SYSTEM - Google Patents

Description

The present invention relates to an energy supply system and its control device and control method.

In recent years, renewable energy (natural energy) such as solar, wind, hydroelectric, biomass, and geothermal energy has been attracting attention as an energy source that produces less carbon dioxide during the generation process. As part of the use of renewable energy, energy supply systems that transmit electricity generated using renewable energy to the power grid are being considered.

It is known that the amount of power generated by renewable energy power generation devices varies greatly depending on weather conditions. For example, solar power generation devices can generate power during the day but not after sunset. As a result, the amount of power generated varies from zero to a maximum over the course of a day. Furthermore, with solar power generation devices, the amount of power generated can vary over time intervals of a few minutes to a few hours depending on changes in the weather. Furthermore, with wind power generation devices, power can be generated day or night as long as the wind blows. However, the amount of power generated can vary over time intervals of a few seconds to a few hours depending on changes in the strength of the wind.

Fluctuations in the amount of power generated by renewable energy power generation equipment lead to fluctuations in the amount of power transmitted to the power grid. Fluctuations in the amount of power transmitted to the power grid can cause problems such as unstable power grid frequency. For this reason, power transmission and distribution companies impose limits on the range of fluctuations in the amount of power transmitted to the power grid. In response to this, for example, Patent Document 1 discloses a power supply system that combines a renewable energy power generation equipment with a storage battery, a water electrolyzer, and a fuel cell. In this system, a portion of the power generated by renewable energy is charged into a storage battery, and another portion of that power is used to produce hydrogen in a water electrolyzer. Fluctuations in the amount of power transmitted are then mitigated by charging and discharging the storage battery and generating electricity in a fuel cell using hydrogen.

International Publication No. 2017/013751

After extensive research into energy supply systems using renewable energy power generation equipment, the inventors discovered a technology that can more reliably mitigate fluctuations in the amount of electricity sent to the power grid.

The present invention was made in consideration of these circumstances, and one of its objectives is to provide technology for more reliably mitigating fluctuations in the amount of electricity transmitted in an energy supply system that uses renewable energy power generation equipment.

One aspect of the present invention is an energy supply system. This system includes a renewable energy power generation device that transmits at least a portion of the power generated by using renewable energy to a power grid, a storage battery that can be charged with the power generated by the renewable energy power generation device and transmits at least a portion of the charged power to the power grid, and a control unit that controls the storage battery so that the rate of change in the amount of power transmitted to the power grid does not exceed a preset allowable rate of change, calculates a required SoC (State of Charge) of the storage battery that is required to maintain the rate of change below the allowable rate of change by transmitting power from the storage battery when power generation by the renewable energy power generation device stops and the amount of power transmitted to the power grid drops to zero, and controls the storage battery so that the amount of power transmitted is reduced when the required SoC exceeds the current SoC of the storage battery.

Another aspect of the present invention is a control device for an energy supply system including a renewable energy power generation device that transmits at least a portion of the power generated by using renewable energy to a power grid, and a storage battery that can be charged with the power generated by the renewable energy power generation device and transmits at least a portion of the charged power to the power grid. The control device controls the storage battery so that the rate of change in the amount of power transmitted to the power grid does not exceed a preset allowable rate of change, and includes a control unit that calculates a required SoC, which is the state of charge (SoC) of the storage battery required to maintain the rate of change below the allowable rate of change by transmitting power from the storage battery when power generation by the renewable energy power generation device stops and the amount of power transmitted to the power grid drops to zero, and controls the storage battery so that the amount of power transmitted is reduced when the required SoC exceeds the current SoC of the storage battery.

Another aspect of the present invention is a control method for an energy supply system including a renewable energy power generation device that transmits at least a portion of the power generated by using renewable energy to a power grid, and a storage battery that can be charged with the power generated by the renewable energy power generation device and transmits at least a portion of the charged power to the power grid. This control method includes controlling the storage battery so that the rate of change in the amount of power transmitted to the power grid does not exceed a preset allowable rate of change, calculating a required SoC, which is the state of charge (SoC) of the storage battery required to maintain the rate of change below the allowable rate of change by transmitting power from the storage battery when power generation by the renewable energy power generation device stops and the amount of power transmitted to the power grid drops to zero, and controlling the storage battery so that the amount of power transmitted is reduced when the required SoC exceeds the current SoC of the storage battery.

Any combination of the above components, and any conversion of the expressions of this disclosure between methods, devices, systems, etc., are also valid aspects of this disclosure.

The present invention makes it possible to more reliably mitigate fluctuations in the amount of electricity transmitted in an energy supply system that uses renewable energy power generation equipment.

1 is a schematic diagram of an energy supply system according to an embodiment. 13 is a flowchart showing an example of fluctuation stabilization control. FIG. 13 is a diagram for explaining guarantee control for fluctuation stabilization. 13 is a flowchart showing an example of guarantee control for fluctuation stabilization. FIG. 13 is a diagram for explaining profit comparison control. 13 is a flowchart showing an example of profit comparison control. FIG. 11 is a diagram showing the relationship between the capacity of a storage battery, the maximum power consumption of a hydrogen production device, and the monthly profit amount.

The present invention will be described below with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention. The same or equivalent components, members, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The scale and shape of each part shown in each drawing are set for convenience to facilitate explanation, and are not to be interpreted as being limiting unless otherwise specified. In addition, when terms such as "first" and "second" are used in this specification or claims, these terms do not indicate any order or importance, but are intended to distinguish one configuration from another. In addition, some of the members that are not important for explaining the embodiment are omitted in each drawing.

Figure 1 is a schematic diagram of an energy supply system 1 according to an embodiment. The energy supply system 1 of this embodiment includes a renewable energy power generation device 2, a storage battery 4, a hydrogen production device 6, and a control device 8.

The renewable energy power generation device 2 generates power using renewable energy. For example, the renewable energy power generation device 2 includes a solar power generation device 10 that uses sunlight, a wind power generation device 12 that uses wind power, and the like. Note that the renewable energy power generation device 2 may also include power generation devices that use renewable energy other than sunlight and wind power, such as geothermal power generation devices, wave power generation devices, temperature difference power generation devices, and biomass power generation devices. In addition, the number of renewable energy power generation devices 2 is not limited.

The renewable energy power generation device 2 is connected to a power transmission line 14 via a transformer (not shown) or the like. The power transmission line 14 is connected to a power grid 16. At least a part of the power generated by the renewable energy power generation device 2 is transmitted to the power grid 16 via the power transmission line 14. A first power meter 18 and a second power meter 20 are connected to the power transmission line 14. The first power meter 18 repeatedly measures the power generation amount P _vre of the renewable energy power generation device 2 at predetermined time intervals (e.g., every second) and sends the measurement value to the control device 8. The second power meter 20 repeatedly measures the power transmission amount P _grid from the energy supply system 1 to the power grid 16 at predetermined time intervals (e.g., every second) and sends the measurement value to the control device 8.

The power generation amount P _vre of the renewable energy power generation device 2 fluctuates depending on weather conditions and the like. Fluctuations in the power generation amount P _vre include short-term fluctuations of several seconds to tens of seconds, medium-term fluctuations of several minutes to tens of minutes, and long-term fluctuations of several hours or more. When the ratio of power originating from the renewable energy power generation device 2 to the total power transmission amount P _grid to the power grid 16 increases, the influence of fluctuations in the power generation amount P _vre on the power grid 16 becomes greater. In response to this, the energy supply system 1 stabilizes the power transmission amount P _grid to the power grid 16 by mitigating fluctuations in the power generation amount P _vre of the renewable energy power generation device 2 using at least one of the storage battery 4 and the hydrogen production device 6.

A known storage battery such as a lithium-ion battery can be used as the storage battery 4. The storage battery 4 is connected to the renewable energy power generation device 2 and the power grid 16 via a power transmission line 14. This allows the storage battery 4 to be charged with electricity generated by the renewable energy power generation device 2, and to transmit at least a portion of the charged electricity to the power grid 16. The storage battery 4 can also supply at least a portion of the charged electricity to the hydrogen production device 6.

The storage battery 4 is connected to the power transmission line 14 via a PCS 22 (power conditioner). The PCS 22 is a device that performs AC/DC conversion and voltage conversion, or one of the two conversions. Therefore, the power generated by the renewable energy power generation device 2 is adjusted by the PCS 22 before being supplied to the storage battery 4. The power discharged from the storage battery 4 is adjusted by the PCS 22 before being supplied to the power grid 16 or the hydrogen production device 6. The storage battery 4 has a sensor (not shown) that measures the SoC (State of Charge) that indicates the remaining capacity, the current value during charging and discharging, etc. The storage battery 4 repeatedly measures the SoC, etc. at a predetermined time interval (for example, every second) and sends the measured value to the control device 8. The storage battery 4 also has a control unit (not shown) that receives commands from the control device 8 and controls the charging and discharging of the storage battery 4.

A known hydrogen production device such as a water electrolyzer can be used as the hydrogen production device 6. The hydrogen production device 6 is connected to the renewable energy power generation device 2 and the storage battery 4 via a power transmission line 14. This allows the hydrogen production device 6 to produce hydrogen using at least one of the power generated by the renewable energy power generation device 2 and the power discharged from the storage battery 4.

The hydrogen production device 6 is connected to the power transmission line 14 via the PCS 24. The PCS 24 is a device that performs AC/DC conversion and voltage conversion, or one of the two conversions. Therefore, the power generated by the renewable energy power generation device 2 and the power discharged by the storage battery 4 are adjusted by the PCS 24 and then supplied to the hydrogen production device 6. The hydrogen production device 6 also has a sensor (not shown) that measures the amount of power consumption, etc. The hydrogen production device 6 repeatedly measures the amount of power consumption, etc. at predetermined time intervals (for example, every second) and sends the measurement value to the control device 8. The amount of power consumption in the hydrogen production device 6 correlates with the operation amount of the hydrogen production device 6, in other words, the amount of hydrogen produced in the hydrogen production device 6. The hydrogen production device 6 also has a control unit (not shown) that receives commands from the control device 8 and controls the operation of the hydrogen production device 6.

The hydrogen produced by the hydrogen production device 6 is consumed in the hydrogen utilization facility 26. Examples of the hydrogen utilization facility 26 include, but are not limited to, a hydrogen station, an oil refinery, a chemical plant, and the like. A hydrogen station is a facility that supplies hydrogen to fuel cell vehicles and the like that use hydrogen as fuel. When the hydrogen utilization facility 26 is an oil refinery or a chemical plant, the hydrogen is utilized in a hydrorefining device, a hydrocracking device, and the like. The hydrorefining device may include a device that removes impurities such as sulfur, nitrogen, and oxygen from the substrate to be treated, and a device that performs a hydrogen treatment on the substrate. The hydrocracking device may include, for example, a device that hydrocrackers heavy fractions to convert them into light fractions, and the like.

In this embodiment, the hydrogen produced by the hydrogen production device 6 is not used to generate electricity for transmission to the power grid 16. However, this is not limited to the above, and the hydrogen produced by the hydrogen production device 6 may be used to generate electricity in a fuel cell or the like, and the obtained electricity may be transmitted to the power grid 16 or charged into the storage battery 4. The hydrogen produced by the hydrogen production device 6 may be supplied to the hydrogen utilization facility 26 in the form of an organic hydride such as methylcyclohexane, a hydrogen storage alloy, or the like. The hydrogen produced by the hydrogen production device 6 may be stored in a hydrogen tank before being supplied to the hydrogen utilization facility 26.

The charging and discharging of the storage battery 4 and the hydrogen production in the hydrogen production device 6 are controlled by a control device 8. The control device 8 has a recording unit 28 and a control unit 30. In FIG. 1, the recording unit 28 and the control unit 30 are depicted as functional blocks. These functional blocks are realized as hardware configurations using elements and circuits including a computer's CPU and memory, and as software configurations using computer programs, etc. It will be understood by those skilled in the art that these functional blocks can be realized in various ways by combining hardware and software.

The recording unit 28 receives measurement values from the first power meter 18 and records the power generation amount P _vre of the renewable energy power generation device 2 over time. The recording unit 28 also receives measurement values from the second power meter 20 and records the power transmission amount P _grid to the power grid 16 over time. The power transmission amount P _grid measured by the second power meter 20 may include the amount of power transmitted directly from the renewable energy power generation device 2 to the power grid 16 and the amount of power transmitted from the storage battery 4 to the power grid 16. The recording unit 28 also receives measurement values from the storage battery 4 and records the SoC, etc. of the storage battery 4 over time. The recording unit 28 also receives measurement values from the hydrogen production device 6 and records the amount of power consumed in the hydrogen production device 6 (amount of hydrogen production) over time.

The control unit 30 controls the storage battery 4 and the hydrogen production device 6 based on various information recorded in the recording unit 28. For example, when the power generation amount P _vre of the renewable energy power generation device 2 increases suddenly, the control unit 30 controls the storage battery 4 to charge the power generated by the renewable energy power generation device 2 or to suppress discharging from the storage battery 4, thereby suppressing an increase in the power transmission amount P _grid to the power grid 16. Furthermore, when the power generation amount P _vre of the renewable energy power generation device 2 decreases suddenly, the control unit 30 controls the storage battery 4 to discharge the stored power or to suppress charging, thereby suppressing a decrease in the power transmission amount P _grid to the power grid 16.

Furthermore, when the power generation amount _Pvre of the renewable energy power generation device 2 increases suddenly, the control unit 30 controls the hydrogen production device 6 to increase the amount of power consumption, thereby suppressing an increase in the amount of power transmission Pgrid to the power _grid 16. Furthermore, when the power generation amount _Pvre of the renewable energy power generation device 2 decreases suddenly, the control unit 30 controls the hydrogen production device 6 to decrease the amount of power consumption, thereby suppressing a decrease in the amount of power transmission _Pgrid to the power grid 16.

(Fluctuation stabilization control)
In a contract between the power transmission and distribution company and the power generation company, an allowable rate of change ΔP _grid of the amount of power transmitted to the power grid 16 is set in advance in the energy supply system 1. The set allowable rate of change ΔP _grid is recorded in the recording unit 28. The allowable rate of change ΔP _{grid is} an allowable value of the amount of change per unit time (kW/s) of the amount of power transmitted P _grid , that is, the maximum amount of power transmitted that is allowed to change in one second. For this reason, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 as fluctuation stabilization control so that the rate of change (kW/s) of the amount of power transmitted to the power _grid 16 does not exceed the allowable rate of change ΔP _grid .

For example, the allowable rate of change ΔP _grid is determined by multiplying the maximum amount of power transmission P _grid,max that can be transmitted from the energy supply system 1 to the power grid 16 by a predetermined coefficient M. The maximum amount of power transmission P grid _,max and the coefficient M are determined by a contract between the power transmission and distribution company and the power generation company. As an example, the coefficient M is 1%/60s. In other words, a fluctuation of 1% of the maximum amount of power transmission P _grid,max is allowed in one minute. In this case, the control unit 30 controls the amount of power transmission P _grid to the power grid 16 so that the amount of power transmission P _grid one minute from now falls within a range having an upper limit of a value obtained by adding 1% of the maximum power transmission amount P _{grid ,max} to the current amount of power transmission P _grid and a lower limit of a value obtained by subtracting 1% of the maximum power transmission amount P grid,max from the current amount of power transmission P _grid (naturally, the amount of power transmission P _grid from the present to one minute from now must also fall within this range).

2 is a flowchart showing an example of fluctuation stabilization control. This flow is repeatedly executed at a predetermined timing by the control unit 30. In this example of fluctuation stabilization control, first, the control unit 30 acquires the power generation amount P _vre (t) of the renewable energy power generation device 2 at time t (present) from the recording unit 28 (S101). Then, the control unit 30 determines whether the power generation amount P _vre (t) has increased from the power generation amount P _vre (t-1) at time t-1 recorded immediately before time t (S102).

When the power generation amount _Pvre (t) increases (Y in S102), the control unit 30 judges whether the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1) exceeds a threshold value (S103). The threshold value is a power generation change amount corresponding to the allowable change rate _ΔPgrid , and is recorded in advance in the recording unit 28. When the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1) exceeds the threshold value (Y in S103), the control unit 30 executes a process of suppressing an increase in the power transmission amount _Pgrid (t) at time t (S104), and ends this routine.

In the increase suppression process, the control unit 30 executes at least one of a command to increase charging power to the storage battery 4, a command to decrease discharging power to the storage battery 4, and a command to increase hydrogen production to the hydrogen production device 6. The command to increase charging power includes starting charging. The command to decrease discharging power includes stopping discharging. The command to increase hydrogen production includes operating the hydrogen production device 6 that is currently stopped. This makes it possible to keep the rate of change of the amount of power transmission P _grid from time t-1 to time t, that is, the difference between the amount of power transmission P _grid (t-1) and the amount of power transmission P _grid (t), below the allowable rate of change ΔP _grid .

If the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1) is equal to or less than the threshold value (N in S103), the control unit 30 ends this routine without executing the increase suppression process. In this case, since the charge/discharge power of the storage battery 4 and the amount of hydrogen produced in the hydrogen production device 6 are the same at time t and time t-1, the amount of power transmitted to the power grid 16 _Pgrid (t) can increase by the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1).

If the power generation amount _Pvre (t) is not increased compared to the power generation amount _Pvre (t-1) (N in S102), the control unit 30 judges whether the power generation amount _Pvre (t) is decreased compared to the power generation amount _Pvre (t-1) (S105). If the power generation amount _Pvre (t) is decreased (Y in S105), the control unit 30 judges whether the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1) exceeds a threshold value (S106). If the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1) exceeds a threshold value (Y in S106), the control unit 30 executes a process of suppressing a decrease in the power transmission amount _Pgrid (t) (S107) and ends this routine.

In the decrease suppression process, the control unit 30 executes at least one of a command to increase discharge power to the storage battery 4, a command to decrease charge power to the storage battery 4, and a command to decrease hydrogen production to the hydrogen production device 6. The command to increase discharge power includes starting discharge. The command to decrease charge power includes stopping charging. The command to decrease hydrogen production includes stopping the operation of the hydrogen production device 6. This makes it possible to keep the rate of change of the amount of power transmission P _grid from time t-1 to time t equal to or less than the allowable rate of change ΔP _grid .

If the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1) is equal to or less than the threshold value (N in S106), the control unit 30 ends this routine without executing the decrease suppression process. In this case, since the charge/discharge power of the storage battery 4 and the amount of hydrogen produced in the hydrogen production device 6 are the same at time t and time t-1, the amount of power transmitted to the power grid 16 _Pgrid (t) can decrease by the difference between the power generation amount _Pvre (t) and the power generation amount _Pvre (t-1).

If the power generation amount P _vre (t) is not decreased below the power generation amount P _vre (t-1) (N in S105), the control unit 30 judges whether the power generation amount P _vre (t) is zero (S108). If the power generation amount P _vre (t) is not zero (N in S108), the control unit 30 ends this routine without performing either the increase suppression process or the decrease suppression process. If the power generation amount P _vre (t) is zero (Y in S108), the control unit 30 judges whether the power transmission amount P _grid (t-1) at time t-1 is equal to or less than the allowable change rate ΔP _grid , that is, equal to or less than the power transmission amount corresponding to the maximum allowable change amount per unit time (S109). If the power transmission amount P _grid is equal to or less than the allowable change rate ΔP _grid (Y in S109), the control unit 30 ends this routine without performing either the increase suppression process or the decrease suppression process. If the amount of transmitted power P _grid (t-1) is not equal to or less than the allowable rate of change ΔP _grid (N in S109), the control unit 30 executes a process for suppressing a decrease in the amount of transmitted power P _grid (t) (S110), and ends this routine.

The flow of the fluctuation stabilization control is not limited to the above. For example, the control may be such that the differential power P _res between the power generation amount P _vre (t-1) and the power transmission amount P _grid (t-1) is calculated, the smaller value of P _res and ΔP _grid is compared with −ΔP _grid , and the larger value is added to the power transmission amount P _grid (t-1) to calculate the power transmission amount P _grid (t). As a result, when the absolute value of the differential power P _res is less than the allowable change rate ΔP _grid , the power transmission amount P _grid (t) can be increased or decreased by the differential power P _res , and when the absolute value of the differential power P _res is equal to or greater than the allowable change rate ΔP _grid , the power transmission amount P _grid (t) can be increased or decreased by the allowable change rate ΔP _grid . In addition, a control that takes into account the SoC of the storage battery 4 may be added to the above control.

(Guaranteed control for fluctuation stabilization)
Furthermore, the control unit 30 executes the following guarantee control for fluctuation stabilization to more reliably prevent the rate of change of the amount of transmitted power P _grid from exceeding the allowable rate of change ΔP _grid . FIG. 3 is a diagram for explaining the guarantee control for fluctuation stabilization. This control is a control for adjusting the balance between the amount of transmitted power P grid and the SoC of the storage battery 4 so that the rate of decrease of the amount of transmitted power P _grid due to discharge from the storage battery 4 can be suppressed to the allowable rate of change ΔP _grid or less until the amount of transmitted power P _grid reaches 0 when power generation in the renewable energy power generation device 2 _suddenly stops. The guarantee control for fluctuation stabilization is mainly executed during power generation by the renewable energy power generation device 2.

In the guarantee control, first, the control unit 30 calculates a required SoC (SoC _required ) according to the current amount of power transmission P _grid,0 recorded in the recording unit 28. The required SoC is the SoC of the storage battery 4 required for maintaining the rate of change of the amount of power transmission P _grid by power transmission from the storage battery 4 at or below the allowable rate of change ΔP _grid when power generation by the renewable energy power generation device 2 stops and the amount of power transmission P _grid to the power grid 16 drops from the current amount to zero.

As shown in Fig. 3, when the amount of power transmission P _grid is gradually reduced at an allowable change rate ΔP _grid (i.e., the maximum allowable change) from the amount of power transmission P _grid,0 immediately before the power generation of the renewable energy power generation device 2 stops, the amount of power transmission P _grid reaches 0 after T seconds. The gradual reduction of the amount of power transmission P _grid is realized by covering the amount of power transmission P _grid by discharging the storage battery 4.

The amount of transmitted power P _grid (t) after t seconds (t≦T) is calculated based on the formula (1).

By substituting time T and the amount of transmitted power P _grid (T)=0 at time T into formula (1), time T is expressed as formula (2).

Furthermore, the amount of discharge Q from the storage battery 4 from the time when the renewable energy power generation device 2 stops generating electricity until time T is expressed as in equation (3) using equation (2).

If the capacity of the storage battery 4 is _CBT (kWh), the required SoC for the amount of power transmission Pgrid _,0 just before power generation is stopped is expressed as in formula (4). The capacity of the storage battery 4 _CBT , the maximum amount of power transmission Pgrid _,max , and formula (4) are recorded in advance in the recording unit 28.

For example, when the capacity C _BT of the storage battery 4 is 21 kWh, the maximum power transmission amount P _grid,max is 18 kW, the coefficient M is 1%/60s, and the allowable change rate ΔP _grid is 0.003 kW/s (18×0.01/60=18/6000=0.003), the required SoC is P _grid,0 ² /453.6. Therefore, the control unit 30 can use the information recorded in the recording unit 28 to calculate the required SoC according to the power transmission amount P _grid,0 immediately before the power generation is stopped, in other words, the required SoC according to the current power transmission amount P _grid . For example, when the power transmission amount P _grid,0 immediately before the power generation is stopped is 18 kW, the required SoC is about 71.4%.

The required SoC may be a value including a predetermined margin constant N. That is, the required SoC can be expressed as SoC _required = (Q/3600C _BT ) + N. Equation (4) corresponds to the case where the margin constant N is zero. The margin constant N can be appropriately set by the designer based on experiments and simulations, and is, for example, 1 to 5%.

When the required SoC exceeds the current SoC of the storage battery 4, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 so as to reduce the amount of power transmission _Pgrid within a range in which the rate of change of the amount of power transmission _Pgrid is equal to or less than the allowable rate of change _ΔPgrid . As a process for reducing the amount of power transmission _Pgrid , the control unit 30 executes at least one of a command to increase charging power to the storage battery 4, a command to decrease discharging power to the storage battery 4, and a command to increase hydrogen production to the hydrogen production device 6. This makes it possible to reduce the amount of power transmission _Pgrid , and therefore to lower the required SoC to a level equal to or less than the current SoC.

By adjusting the amount of power transmission P _grid so that the required SoC is equal to or less than the current SoC, when power generation by the renewable energy power generation device 2 suddenly stops (the amount of power transmission P _grid at this time becomes the amount of power transmission P _grid,0 immediately before the power generation is stopped), the amount of power transmission P _grid can be reduced from the current amount to zero while maintaining the rate of change of the amount of power transmission P _{grid equal to or less than the allowable rate of change ΔP grid only} by discharging from the storage battery 4. In other words, fluctuation stabilization control can be realized only by the storage battery 4. Therefore, fluctuation stabilization of the amount of power transmission P _grid can be guaranteed.

In addition, when the amount of power transmission P _grid is reduced by charging the storage battery 4, the SoC of the storage battery 4 may increase. In this case, the required SoC can be made equal to or lower than the current SoC by the synergistic effect of the reduction in the amount of power transmission P _grid and the increase in the SoC. In addition, the control unit 30 can execute the fluctuation stabilization control and the guarantee control in parallel. When the control contents to be executed in the two controls are contradictory, the adjustment of the amount of power transmission P _grid based on the guarantee control is executed with priority. In addition, the guarantee control is a control that reduces the amount of power transmission P _grid while keeping the rate of change of the amount of power transmission P _grid equal to or lower than the allowable rate of change ΔP _grid . For this reason, the guarantee control can be interpreted as a part of the fluctuation stabilization control in a broad sense. In addition, the fluctuation stabilization control and the guarantee control can be realized by charging and discharging the storage battery 4 even if the energy supply system 1 does not have the hydrogen production device 6.

4 is a flowchart showing an example of the guarantee control for fluctuation stabilization. This flow is repeatedly executed at a predetermined timing by the control unit 30. In this example of the guarantee control for fluctuation stabilization, the control unit 30 first obtains the current amount of power transmission _Pgrid recorded in the recording unit 28 and calculates the required SoC (S201). The control unit 30 then obtains the current SoC recorded in the recording unit 28 and determines whether the required SoC exceeds the current SoC (S202).

If the required SoC is greater than the current SoC (Y in S202), the control unit 30 executes a process to reduce the amount of power transmission P _grid (S203) and ends this routine. If the required SoC is equal to or less than the current SoC (N in S202), the control unit 30 ends this routine without executing the reduction process.

(Profit Comparison Control)
The control unit 30 executes the profit comparison control described below in addition to the fluctuation stabilization control and the guarantee control. Fig. 5 is a diagram for explaining the profit comparison control. In the profit comparison control, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 based on the preset electricity price and hydrogen price. Furthermore, the control unit 30 in this embodiment controls the storage battery 4 and the hydrogen production device 6 based on the power loss (charge and discharge efficiency) accompanying the charging and discharging of the storage battery 4 and the hydrogen production efficiency of the hydrogen production device 6 (the amount of hydrogen produced per amount of electricity consumed, also called the hydrogen production unit) in addition to the electricity price and hydrogen price.

The electricity price is, for example, a market price, and the trading price (spot price) every 30 minutes is determined the day before. The hydrogen price is, for example, the selling price of hydrogen at a hydrogen station, and is set by each business operator. Furthermore, the hydrogen price may be the market price when a hydrogen market is established. The power loss associated with charging and discharging the storage battery 4 is determined according to the characteristics of the storage battery 4 and the PCS 22. The hydrogen production efficiency of the hydrogen production device 6 is determined according to the characteristics of the hydrogen production device 6 and the PCS 24. The electricity price, hydrogen price, power loss, and hydrogen production efficiency are recorded in advance in the recording unit 28. The electricity price and hydrogen price may be provided via a telecommunications line, etc.

When electricity generated by the renewable energy power generation device 2 is transmitted to the power grid 16, a profit according to the price of electricity is obtained. On the other hand, when hydrogen is produced by the hydrogen production device 6 using electricity generated by the renewable energy power generation device 2, a profit according to the hydrogen price and the hydrogen production efficiency is obtained. When the profit obtained by transmitting electricity to the power grid 16 (electricity transmission profit) exceeds the profit obtained when hydrogen is produced with the same amount of electricity (hydrogen production profit), transmission to the power grid 16 is prioritized, and when the hydrogen production profit exceeds the electricity transmission profit, hydrogen production is prioritized, thereby increasing the profitability of the energy supply system 1.

Furthermore, by charging the storage battery 4 with the electricity generated by the renewable energy power generation device 2 and allocating the charged electricity to electricity transmission or hydrogen production, profitability can be further improved. On the other hand, charging and discharging the storage battery 4 involves power loss. For this reason, the profitability of the energy supply system 1 can be further improved by switching the supply destination of the electricity charged in the storage battery 4 while taking into account the loss of profit due to the power loss. Note that if the control content to be executed in the profit comparison control conflicts with the control content to be executed in the fluctuation stabilization control or the guarantee control, the control based on the fluctuation stabilization control or the guarantee control is executed with priority. Profit comparison control can also be considered as control that switches the control algorithm of the fluctuation stabilization control (priority of the supply destination of electricity) based on the results of the profit comparison.

In this embodiment, the first profit amount EP1, the second profit amount EP2, the third profit amount HP3, and the fourth profit amount HP4 are set in advance and recorded in the recording unit 28. The first profit amount EP1 is the profit amount, determined at least based on the electricity price, when the unit power generated by the renewable energy power generation device 2 is transmitted to the power grid 16 via the storage battery 4. The second profit amount EP2 is the profit amount, determined at least based on the electricity price and the electricity loss, when the unit power generated by the renewable energy power generation device 2 is transmitted to the power grid 16 via the storage battery 4. The third profit amount HP3 is the profit amount, determined at least based on the hydrogen price and the hydrogen production efficiency, when the unit power generated by the renewable energy power generation device 2 is supplied to the hydrogen production device 6 via the storage battery 4 to produce hydrogen. The fourth profit amount HP4 is determined based on at least the hydrogen price, hydrogen production efficiency, and power loss, and is the profit amount when hydrogen is produced by supplying the unit power generated by the renewable energy power generation device 2 to the hydrogen production device 6 via the storage battery 4.

As described above, the price of electricity, as an example, fluctuates every 30 minutes. Therefore, the first profit amount EP1 and the second profit amount EP2 are repeatedly updated at a predetermined time interval. On the other hand, the hydrogen price fluctuates less frequently than the electricity price, for example, fluctuating every few weeks to several months. Furthermore, the power loss is specific to the storage battery 4 and the PCS 22, and does not fluctuate substantially. Furthermore, the hydrogen production efficiency is specific to the hydrogen production device 6 and the PCS 24, and does not fluctuate substantially. Therefore, although the third profit amount HP3 is updated when the hydrogen price is revised and at least one of the hydrogen production device 6 and the PCS 24 is replaced, and the fourth profit amount HP4 is updated when the hydrogen price is revised and at least one of the storage battery 4, the PCS 22, the hydrogen production device 6, and the PCS 24 is replaced, in one example of control, the third profit amount HP3 and the fourth profit amount HP4 can be considered as fixed values. Therefore, the magnitude relationship of each profit amount changes with fluctuations in the electricity price. Naturally, the first profit amount EP1 is higher than the second profit amount EP2, and the third profit amount HP3 is higher than the fourth profit amount HP4.

5, in the case of category A where the first profit amount EP1 and the second profit amount EP2 are higher than the third profit amount HP3, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the first target state. The first target state is a state where the direct power amount α1, which is the amount of power transmitted P _grid from the renewable energy power generation device 2 to the power grid 16 without passing through the storage battery 4, is greater than the amount of power supplied α2 to the storage battery 4 and the amount of power supplied α3 to the hydrogen production device 6, and the amount of power supplied α2 to the storage battery 4 is greater than the amount of power supplied α3 to the hydrogen production device 6.

That is, in category A, direct electricity from the renewable energy power generation device 2 to the power grid 16 is the most profitable. Therefore, profitability can be increased by making the amount of direct electricity α1 greater than the amounts of electricity supplied α2, α3 to the storage battery 4 and the hydrogen production device 6. Also, in category A, the profit (EP2) obtained from selling electricity accompanied by power loss due to charging and discharging the storage battery 4 is higher than the profit (HP3) obtained from hydrogen production without such power loss. Therefore, profitability can be improved by making the amount of electricity supplied α2 to the storage battery 4 greater than the amount of electricity supplied α3 to the hydrogen production device 6. The electricity charged in the storage battery 4 is transmitted to the power grid 16 when the amount of direct electricity α1 is less than the maximum amount of electricity transmission P _grid,max .

The control unit 30 can increase the power supply amount α2 by controlling the storage battery 4 to increase the charging power (including starting charging). Also, the control unit 30 can decrease the power supply amount α2 by controlling the storage battery 4 to decrease the charging power (including stopping charging). Also, the control unit 30 can increase the power supply amount α3 by controlling the hydrogen production device 6 to increase the amount of hydrogen production (including starting hydrogen production). Also, the control unit 30 can decrease the power supply amount α3 by controlling the hydrogen production device 6 to decrease the amount of hydrogen production (including stopping hydrogen production). Also, the control unit 30 can increase or decrease the direct power amount α1 by increasing or decreasing at least one of the power supply amount α2 and the power supply amount α3.

Ideally, the proportion of the direct power amount α1 in the power generation amount P _vre of the renewable energy power generation device 2 is controlled to approach 100%. Then, when the power generation amount P _vre exceeds the maximum power transmission amount P _grid,max and surplus power occurs, this surplus power is preferentially supplied to the storage battery 4 rather than the hydrogen production device 6. However, since the above-mentioned fluctuation stabilization control and guarantee control take precedence over the profit comparison control, when the power generation amount P _vre increases suddenly, even if the direct power amount α1 is less than the maximum power transmission amount P _grid,max , the power supply amount α2 to the storage battery 4 can be increased so that the change rate of the direct power amount α1 satisfies the allowable change rate ΔP _grid . Also, when the power generation amount P _vre of the renewable energy power generation device 2 decreases suddenly, the power supply amount α2 can be reduced. Also, power can be transmitted from the storage battery 4 to the power grid 16 as necessary.

For example, when the power generation amount P _vre (t) of the renewable energy power generation device 2 at time t (present) is greater than the power transmission amount P _grid (t-1) at time t-1, the control unit 30 increases the power transmission amount P _grid (t) at time t, that is, the direct power amount α1, within a range not exceeding the maximum power transmission amount P _grid,max . When the power generation amount P _vre (t) is smaller than the power transmission amount P _grid (t-1), the control unit 30 decreases the direct power amount α1. If the control unit 30 does not change the power supply amounts α2 and α3, the difference between the power generation amount P _vre (t) and the power transmission amount P _grid (t-1) is the increase or decrease amount of the direct power amount α1.

Furthermore, when the power generation amount P _vre (t) exceeds the maximum power transmission amount P _grid,max and surplus power occurs, the control unit 30 increases the power supply amount α2 to the storage battery 4. When the surplus power decreases, the power supply amount α2 is decreased accordingly. Moreover, as an example, the power supply amount α3 to the hydrogen production device 6 is set to zero. However, it is desirable to maintain the SoC of the storage battery 4 at or below a predetermined threshold value. This is to ensure that the storage battery 4 has a sufficient free capacity and to minimize the leakage of surplus power. Therefore, when the SoC of the storage battery 4 exceeds the threshold value, the control unit 30 may increase the power supply amount α3 to the hydrogen production device 6.

In addition, when there is no surplus power, control may be implemented to supply part of the power generated by the renewable energy power generation device 2 to the storage battery 4. In this case, when the SoC of the storage battery 4 exceeds a threshold value, the increase in the SoC may be suppressed by combining an increase in the amount of power supply α3 and an increase in the amount of direct power α1. As an example, the increase in the amount of direct power α1 is implemented before the increase in the amount of power supply α3.

In the case of category B, where the first profit amount EP1 is higher than the third profit amount HP3 and the second profit amount EP2 is lower than the third profit amount HP3, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the second target state. The second target state is a state in which the direct electricity amount α1 is greater than the power supply amounts α2 and α3 to the storage battery 4 and the hydrogen production device 6, and the power supply amount α3 to the hydrogen production device 6 is greater than the power supply amount α2 to the storage battery 4.

That is, in category B, direct power from the renewable energy power generation device 2 to the power grid 16 is the most profitable. For this reason, profitability can be increased by making the amount of direct power α1 greater than the amounts of power supply α2, α3 to the storage battery 4 and the hydrogen production device 6. Also, in category B, the profit (HP3) obtained from hydrogen production without power loss due to charging and discharging the storage battery 4 is higher than the profit (EP2) obtained from selling the power with the power loss. For this reason, profitability can be increased by making the amount of power supply α3 to the hydrogen production device 6 greater than the amount of power supply α2 to the storage battery 4. The power charged in the storage battery 4 is transmitted to the power grid 16 when the amount of direct power α1 is less than the maximum power transmission amount P _grid,max .

Ideally, the proportion of the direct power amount α1 in the power generation amount P _vre of the renewable energy power generation device 2 is controlled to approach 100%. Then, when the power generation amount P _vre of the renewable energy power generation device 2 exceeds the maximum power transmission amount P _grid,max and surplus power is generated, this surplus power is supplied preferentially to the hydrogen production device 6 rather than the storage battery 4. However, the point that the fluctuation stabilization control and the guarantee control are given priority is the same as the control in category A.

For example, when the power generation amount P _vre (t) is greater than the power transmission amount P _grid (t-1), the control unit 30 increases the direct power amount α1 at time t within a range not exceeding the maximum power transmission amount P _grid,max . When the power generation amount P _vre (t) is smaller than the power transmission amount P _grid (t-1), the control unit 30 decreases the direct power amount α1 at time t. When the power generation amount P _vre (t) exceeds the maximum power transmission amount P _grid,max and surplus power is generated, the control unit 30 increases the power supply amount α3 to the hydrogen production device 6. When the surplus power decreases, the power supply amount α3 is decreased accordingly. As an example, the power supply amount α2 to the storage battery 4 is set to zero as far as it is allowed by the fluctuation stabilization control and the guarantee control. The control for maintaining the SoC is the same as in the case of category A, but as an example, the increase in the power supply amount α3 is performed before the increase in the direct power amount α1.

In the case of category C, where the third profit amount HP3 is higher than the first profit amount EP1 and the fourth profit amount HP4 is lower than the first profit amount EP1, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the third target state. The third target state is a state in which the amount of power supplied α3 to the hydrogen production device 6 is greater than the amount of direct power α1 and the amount of power supplied α2 to the storage battery 4, and the amount of direct power α1 is greater than the amount of power supplied α2 to the storage battery 4.

That is, in category C, it is most profitable to produce hydrogen by directly supplying power from the renewable energy power generation device 2 to the hydrogen production device 6. For this reason, profitability can be increased by making the amount of power supply α3 to the hydrogen production device 6 greater than the amount of direct power supply α1 and the amount of power supply α2 to the storage battery 4. Also, in category C, the profit (EP1) obtained by selling electricity without power loss due to charging and discharging the storage battery 4 is higher than the profit (HP4) obtained by hydrogen production with such power loss. For this reason, profitability can be increased by making the amount of direct power supply α1 greater than the amount of power supply α2 to the storage battery 4. The power charged in the storage battery 4 is supplied to the hydrogen production device 6 when the power generation amount P _vre of the renewable energy power generation device 2 is insufficient for the power required for hydrogen production by the hydrogen production device 6.

Ideally, the proportion of the power supply amount α3 in the power generation amount _Pvre of the renewable energy power generation device 2 is controlled to approach 100%. Then, when the power generation amount _Pvre of the renewable energy power generation device 2 exceeds the maximum power supply amount _α3max required for the upper limit amount of hydrogen production in the hydrogen production device 6 and surplus power is generated, this surplus power is supplied preferentially to the power grid 16 rather than the storage battery 4. However, the point that the fluctuation stabilization control and guarantee control are given priority is the same as in the control in categories A and B.

For example, when the power generation amount P _vre (t) is greater than the power supply amount α3 to the hydrogen production device 6 at time t-1, the control unit 30 increases the power supply amount α3 at time t. When the power generation amount P _vre (t) is smaller than the power supply amount α3 at time t-1, the control unit 30 decreases the power supply amount α3 at time t. In addition, when the power generation amount P _vre (t) exceeds the maximum power supply amount α3 _max and surplus power occurs, the control unit 30 increases the direct power amount α1 by decreasing the power supply amount α2 to the storage battery 4. When the surplus power decreases, the direct power amount α1 naturally decreases accordingly. As an example, the power supply amount α2 to the storage battery 4 is set to zero as far as it is allowed by the fluctuation stabilization control and the guarantee control. The control for maintaining the SoC is the same as in the cases of categories A and B, but as an example, the increase in the direct power amount α1 is performed before the increase in the power supply amount α3.

In the case of category D, where the third profit amount HP3 and the fourth profit amount HP4 are higher than the first profit amount EP1, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the fourth target state. The fourth target state is a state in which the amount of power supplied α3 to the hydrogen production device 6 is greater than the amount of direct power α1 and the amount of power supplied α2 to the storage battery 4, and the amount of power supplied α2 to the storage battery 4 is greater than the amount of direct power α1.

That is, in category D, it is most profitable to produce hydrogen by directly supplying power from the renewable energy power generation device 2 to the hydrogen production device 6. For this reason, profitability can be improved by making the amount of power supply α3 to the hydrogen production device 6 greater than the amount of direct power α1 and the amount of power supply α2 to the storage battery 4. Also, in category D, the profit (HP4) obtained from hydrogen production accompanied by power loss due to charging and discharging the storage battery 4 is higher than the profit (EP1) obtained from selling electricity without such power loss. For this reason, profitability can be improved by making the amount of power supply α2 to the storage battery 4 greater than the amount of direct power α1. The power charged in the storage battery 4 is supplied to the hydrogen production device 6 when the power generation amount P _vre of the renewable energy power generation device 2 is insufficient for the power required for hydrogen production by the hydrogen production device 6.

Ideally, the proportion of the power supply amount α3 in the power generation amount P _vre of the renewable energy power generation device 2 is controlled to approach 100%. Then, when the power generation amount P _vre of the renewable energy power generation device 2 exceeds the power supply amount α3 _max and surplus power is generated, this surplus power is supplied preferentially to the storage battery 4 rather than to the power grid 16. However, the point that the fluctuation stabilization control and the guarantee control are given priority is the same as the control in the sections A to C.

For example, when the power generation amount P _vre (t) is greater than the power supply amount α3 at time t-1, the control unit 30 increases the power supply amount α3 at time t. When the power generation amount P _vre (t) is smaller than the power supply amount α3 at time t-1, the control unit 30 decreases the power supply amount α3 at time t. Furthermore, when the power generation amount P _vre (t) exceeds the maximum power supply amount α3 _max and surplus power is generated, the control unit 30 increases the power supply amount α2 to the storage battery 4. This decreases the direct delivery power amount α1. When the surplus power decreases, the power supply amount α2 is decreased accordingly. As an example, the direct delivery power amount α1 is set to zero. The control for maintaining the SoC is similar to the cases of categories A to C, but as an example, the increase in the power supply amount α3 is performed before the increase in the direct delivery power amount α1.

When the second profit amount EP2 and the third profit amount HP3 are the same (EP2=HP3), the control unit 30 executes either the control of category A or the control of category B. Similarly, when the first profit amount EP1 and the third profit amount HP3 are the same (EP1=HP3), the control unit 30 executes either the control of category B or the control of category C. When the first profit amount EP1 and the third profit amount HP3 are the same, the second profit amount EP2 and the fourth profit amount HP4 are also the same (EP2=HP4). When the first profit amount EP1 and the fourth profit amount HP4 are the same (EP1=HP4), the control unit 30 executes either the control of category C or the control of category D.

Figure 6 is a flow chart showing an example of profit comparison control. This flow is repeatedly executed at a predetermined timing by the control unit 30. In the example described below, if the second profit amount EP2 and the third profit amount HP3 are the same amount, the control unit 30 executes control of category A. If the first profit amount EP1 and the third profit amount HP3 are the same amount, the control unit 30 executes control of category B. If the first profit amount EP1 and the fourth profit amount HP4 are the same amount, the control unit 30 executes control of category C.

In one example of profit comparison control, the control unit 30 first acquires the first profit amount EP1 to the fourth profit amount HP4 from the recording unit 28 (S301). The control unit 30 then determines whether the first profit amount EP1 is higher than the third profit amount HP3 and whether the second profit amount EP2 is equal to or greater than the third profit amount HP3 (S302). If the determination condition of step S302 is met (Y in S302), the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the first target state (S303), and ends this routine.

If the judgment condition of step S302 is not met (N in S302), the control unit 30 judges whether the first profit amount EP1 is equal to or greater than the third profit amount HP3 and whether the second profit amount EP2 is lower than the third profit amount HP3 (S304). If the judgment condition of step S304 is met (Y in S304), the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the second target state (S305), and ends this routine.

If the judgment condition of step S304 is not met (N in S304), the control unit 30 judges whether the third profit amount HP3 is higher than the first profit amount EP1 and whether the fourth profit amount HP4 is equal to or less than the first profit amount EP1 (S306). If the judgment condition of step S306 is met (Y in S306), the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the third target state (S307), and ends this routine.

If the judgment condition of step S306 is not met (N in S306), this means that the third profit amount HP3 and the fourth profit amount HP4 are higher than the first profit amount EP1, so the control unit 30 controls the storage battery 4 and the hydrogen production device 6 to approach the fourth target state (S308), and ends this routine.

Figure 7 is a diagram showing the relationship between the capacity of the storage battery 4, the maximum power consumption of the hydrogen production device 6, and the monthly profit amount. In Figure 7, the number displayed in the box for each combination of the capacity of the storage battery 4 (also called the size of the storage battery 4) and the maximum power consumption of the hydrogen production device 6 (also called the size of the hydrogen production device 6) is the profit amount obtained from that combination. The maximum power consumption of the hydrogen production device 6 means the maximum amount of electricity consumed by the hydrogen production device 6 per unit time, and indicates the scale of hydrogen production volume.

The inventors calculated the monthly profit amount obtained when the fluctuation stabilization control, the fluctuation stabilization guarantee control, and the profit comparison control were executed by simulation, using the capacity of the storage battery 4 and the maximum power consumption of the hydrogen production device 6 as variables. As a result, as shown in FIG. 7, it was found that the monthly profit amount changes depending on the combination of the capacity of the storage battery 4 and the maximum power consumption of the hydrogen production device 6. It was also found that the profit amount is maximized in a predetermined combination, specifically, a storage battery of 35 kW x a hydrogen production device of 15 kW. In addition, the combination corresponding to the white squares (squares without profit amount) in FIG. 7 could not satisfy the allowable rate of change ΔP _grid , which is a requirement of the fluctuation stabilization control. Therefore, by determining the combination of the capacity of the storage battery 4 and the maximum power consumption of the hydrogen production device 6 according to at least the allowable rate of change ΔP _grid , it is possible to maximize profitability while suppressing the fluctuation of the amount of power transmitted to the power system 16 P _grid to be equal to or less than the allowable rate of change ΔP _grid .

As described above, the energy supply system 1 according to the present embodiment includes the renewable energy power generation device 2 that transmits at least a portion of the power generated by utilizing renewable energy to the power grid 16, the storage battery 4 that can be charged with the power generated by the renewable energy power generation device 2 and can transmit at least a portion of the charged power to the power grid 16, and the control unit 30 that controls charging and discharging of the storage battery 4. The control unit 30 controls the storage battery 4 so that the rate of change of the amount of power transmitted to the power grid 16 P _grid does not exceed a preset allowable rate of change ΔP _grid . The control unit 30 also calculates a required SoC (State of Charge) of the storage battery 4. The required SoC is a SoC required to maintain the rate of change of the amount of power transmitted P _grid by the power transmission from the storage battery 4 at or below the allowable rate of change ΔP _grid when the power generation of the renewable energy power generation device 2 stops and the amount of power transmitted to the power grid 16 P _grid drops from the current amount to zero. Then, when the required SoC exceeds the current SoC of the storage battery 4, the control unit 30 controls the storage battery 4 so as to reduce the amount of transmitted power _Pgrid .

In this way, by adjusting the amount of power transmission P _grid so that the required SoC does not exceed the current SoC, even if the power generation of the renewable energy power generation device 2 suddenly stops, the rate of change of the amount of power transmission P _grid can be suppressed to the allowable change rate ΔP _grid or less by only discharging from the storage battery 4. Therefore, the fluctuation of the amount of power transmission P _grid in the energy supply system 1 can be more reliably mitigated. In addition, the guarantee of the stabilization of the fluctuation of the amount of power transmission P _grid can be realized by increasing the current SoC to the required SoC or more while maintaining the amount of power transmission P _grid , that is, without changing the required SoC. However, in this case, the storage battery 4 needs to have a large capacity, which may lead to an increase in the cost of the energy supply system 1. In contrast, by reducing the amount of power transmission P _grid to reduce the required SoC, the stabilization of the fluctuation of the amount of power transmission P _grid can be guaranteed by the storage battery 4 while avoiding the increase in the capacity of the storage battery 4. Therefore, according to this embodiment, the increase in the manufacturing cost of the energy supply system 1 can be suppressed.

Moreover, the energy supply system 1 of the present embodiment includes a hydrogen production device 6 that produces hydrogen using at least one of the power generated by the renewable energy power generation device 2 and the power discharged from the storage battery 4. The control unit 30 controls the storage battery 4 and the hydrogen production device 6 so that the rate of change in the amount of power transmission P _grid does not exceed the allowable rate of change ΔP _grid , and controls the storage battery 4 and the hydrogen production device 6 so that the amount of power transmission P _grid decreases when the required SoC exceeds the current SoC.

In this way, by adjusting the power transmission amount P _grid by combining the storage battery 4 and the hydrogen production device 6, it is possible to more easily mitigate the fluctuation of the power transmission amount P _grid compared to the case of using only the storage battery 4. Furthermore, even if there is a large difference between the maximum power generation amount of the renewable energy power generation device 2 and the maximum power transmission amount P _grid,max that can be transmitted to the power grid 16, such as when the size of the power transmission line 14 or the inter-regional interconnection line is insufficient for the scale of the renewable energy power generation device 2, the surplus power generated by this difference can be consumed by the hydrogen production device 6. This makes it possible to increase the degree of freedom of the combination of the energy supply system 1 and the power grid 16. Furthermore, it is possible to more reliably or more simply ensure that the power transmission amount P _grid from the energy supply system 1 does not exceed the maximum power transmission amount P _grid,max .

The control unit 30 also controls the storage battery 4 and the hydrogen production device 6 based on preset electricity prices and hydrogen prices. This type of control allows more electricity to be supplied to the one that can provide the higher profits, either by transmitting electricity to the power grid 16 or by producing hydrogen in the hydrogen production device 6, thereby increasing the profitability of the energy supply system 1.

As an example, the profit amount when the unit power generated by the renewable energy power generation device 2 is transmitted to the power grid 16 via the storage battery 4 is set as the first profit amount EP1, which is determined at least based on the power price. The profit amount when the unit power generated by the renewable energy power generation device 2 is transmitted to the power grid 16 via the storage battery 4 is set as the second profit amount EP2, which is determined at least based on the power price and the power loss associated with the charging and discharging of the storage battery 4. The profit amount when the unit power generated by the renewable energy power generation device 2 is supplied to the hydrogen production device 6 via the storage battery 4 to produce hydrogen is set as the third profit amount HP3, which is determined at least based on the hydrogen price and the hydrogen production efficiency of the hydrogen production device 6. The profit amount when the unit power generated by the renewable energy power generation device 2 is supplied to the hydrogen production device 6 via the storage battery 4 to produce hydrogen is set as the fourth profit amount HP4, which is determined at least based on the hydrogen price, the hydrogen production efficiency, and the power loss. The first profit amount EP1 is higher than the second profit amount EP2, and the third profit amount HP3 is higher than the fourth profit amount HP4.

In this case, when the first profit amount EP1 and the second profit amount EP2 are higher than the third profit amount HP3, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 so as to approach a first target state in which the direct power amount α1, which is the amount of power transmitted P _grid from the renewable energy power generation device 2 to the power grid 16 without passing through the storage battery 4, is greater than the power supplies α2, α3 to the storage battery 4 and the hydrogen production device 6, and the power supply amount α2 to the storage battery 4 is greater than the power supply amount α3 to the hydrogen production device 6. In addition, when the first profit amount EP1 is higher than the third profit amount HP3 and the second profit amount EP2 is lower than the third profit amount HP3, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 so as to approach a second target state in which the direct power amount α1 is greater than the power supplies α2, α3 to the storage battery 4 and the hydrogen production device 6, and the power supply amount α3 to the hydrogen production device 6 is greater than the power supply amount α2 to the storage battery 4.

When the third profit amount HP3 is higher than the first profit amount EP1 and the fourth profit amount HP4 is lower than the first profit amount EP1, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 so as to approach a third target state in which the amount of power supplied to the hydrogen production device 6 is greater than the amount of direct power supplied to the storage battery 4 and the amount of power supplied to the storage battery 4, and the amount of direct power supplied to the storage battery 4 is greater than the amount of direct power supplied to the storage battery 4. When the third profit amount HP3 and the fourth profit amount HP4 are higher than the first profit amount EP1, the control unit 30 controls the storage battery 4 and the hydrogen production device 6 so as to approach a fourth target state in which the amount of power supplied to the hydrogen production device 6 is greater than the amount of direct power supplied to the storage battery 4 and the amount of power supplied to the storage battery 4 is greater than the amount of direct power supplied to the storage battery 4.

In the present embodiment, the combination of the capacity of the storage battery 4 and the maximum power consumption of the hydrogen production device 6 is determined according to the allowable rate of change ΔP _grid . This makes it possible to further increase the profitability of the energy supply system 1 while suppressing fluctuations in the amount of power transmission P _grid .

Above, the embodiments of the present invention have been described in detail. The above-mentioned embodiments merely show specific examples of implementing the present invention. The contents of the embodiments do not limit the technical scope of the present invention, and many design changes such as changing, adding, and deleting components are possible within the scope of the idea of the invention defined in the claims. A new embodiment with design changes has the effects of both the combined embodiment and modification. In the above-mentioned embodiments, the contents for which such design changes are possible are emphasized by adding notations such as "in this embodiment" and "in this embodiment", but design changes are permitted even in contents without such notations. Any combination of the above-mentioned components is also valid as an aspect of the present invention.

The embodiment may be specified by the items described below.
[Item 1]
A control device (8) for an energy supply system (1) including a renewable energy power generation device (2) that transmits at least a portion of electricity generated by utilizing renewable energy to a power grid (16), and a storage battery (4) capable of charging electricity generated by the renewable energy power generation device (2) and transmitting at least a portion of the charged electricity to the power grid (16),
a control unit (30) that controls the storage battery (4) so that a rate of change of an amount of power transmitted to the power grid (16) (P _grid ) does not exceed a preset allowable rate of change (ΔP _grid ), calculates a required SoC, which is a State of Charge ( _SoC ) of the storage battery (4) required to maintain the rate of change at or below the allowable rate of change (ΔP _grid ) by transmitting power from the storage battery (4) when power generation by the renewable energy power generation device (2) stops and the amount of power transmitted to the power grid (16) (P grid ) falls to zero, and controls the storage battery (4) so that the amount of power transmitted (P _grid ) is reduced when the required SoC exceeds a current SoC of the storage battery (4);
A control device (8) for an energy supply system (1).
[Item 2]
A control method for an energy supply system (1) including a renewable energy power generation device (2) that transmits at least a portion of electric power generated by utilizing renewable energy to a power grid (16), and a storage battery (4) capable of charging electric power generated by the renewable energy power generation device (2) and transmitting at least a portion of the charged electric power to the power grid (16), comprising:
The method includes controlling the storage battery (4) so that the rate of change of the amount of power transmitted to the power grid (16) (P _grid ) does not exceed a preset allowable rate of change (ΔP _grid ), calculating a required SoC, which is the State of Charge (SoC) of the storage battery (4) required to maintain the rate of change at or below the allowable rate of change (ΔP _grid ) by transmitting power from the storage battery (4) when power generation by the renewable energy power generation device (2) stops and the amount of power _transmitted to the power grid (16) (P grid ) falls to zero, and controlling the storage battery (4) so that the amount of power transmitted (P _grid ) is reduced when the required SoC exceeds the current SoC of the storage battery (4).
A method for controlling an energy supply system (1).

1 Energy supply system, 2 Renewable energy power generation device, 4 Storage battery, 6 Hydrogen production device, 8 Control device, 16 Power system, 28 Recording unit, 30 Control unit.

Claims (7)

A renewable energy power generation device that transmits at least a portion of electric power generated by utilizing renewable energy to a power grid;
A storage battery capable of storing the power generated by the renewable energy power generation device and transmitting at least a portion of the stored power to a power grid;
a control unit that controls the storage battery so that a rate of change in the amount of power transmitted to the power grid does not exceed a preset allowable rate of change, calculates a required SoC, which is a State of Charge (SoC) of the storage battery necessary to maintain the rate of change at or below the allowable rate of change by transmitting power from the storage battery when power generation by the renewable energy power generation device stops and the amount of power transmitted to the power grid drops to zero, and controls the storage battery so that the amount of power transmitted is reduced when the required SoC exceeds a current SoC of the storage battery.
Energy supply system. a hydrogen production device that produces hydrogen using at least one of the electric power generated by the renewable energy power generation device and the electric power discharged from the storage battery;
the control unit controls the storage battery and the hydrogen production device so that the rate of change in the amount of transmitted power does not exceed the allowable rate of change, and controls the storage battery and the hydrogen production device so that the amount of transmitted power is reduced when the required SoC exceeds the current SoC.
The energy supply system according to claim 1 . The control unit controls the storage battery and the hydrogen production device based on a preset electricity price and a preset hydrogen price.
The energy supply system according to claim 2 . A first profit amount is a profit amount determined based on at least the electricity price when a unit power generated by the renewable energy power generation device is transmitted to a power grid not via a storage battery;
a second profit amount is a profit amount when a unit power generated by the renewable energy power generation device is transmitted to a power grid via a storage battery, the profit amount being determined based on at least the power price and a power loss accompanying charging and discharging of the storage battery;
a third profit amount is a profit amount when hydrogen is produced by supplying unit power generated by the renewable energy power generation device to the hydrogen production device not via a storage battery, the profit amount being determined based on at least the hydrogen price and the hydrogen production efficiency of the hydrogen production device;
When the profit amount when the unit power generated by the renewable energy power generation device is supplied to the hydrogen production device via a storage battery to produce hydrogen, the profit amount is determined based on at least the hydrogen price, the hydrogen production efficiency, and the power loss, and the fourth profit amount is:
the first profit amount is greater than the second profit amount, the third profit amount is greater than the fourth profit amount,
The control unit is
When the first profit amount and the second profit amount are higher than the third profit amount, the storage battery and the hydrogen production device are controlled so as to approach a first target state in which a direct power amount, which is an amount of power transmitted from the renewable energy power generation device to a power grid not via a storage battery, is greater than an amount of power supplied to the storage battery and the hydrogen production device, and an amount of power supplied to the storage battery is greater than an amount of power supplied to the hydrogen production device;
When the first profit amount is higher than the third profit amount and the second profit amount is lower than the third profit amount, the storage battery and the hydrogen production device are controlled so as to approach a second target state in which the amount of direct electricity is greater than the amount of electricity supplied to the storage battery and the hydrogen production device, and the amount of electricity supplied to the hydrogen production device is greater than the amount of electricity supplied to the storage battery;
When the third profit amount is higher than the first profit amount and the fourth profit amount is lower than the first profit amount, the storage battery and the hydrogen production device are controlled so as to approach a third target state in which the amount of power supplied to the hydrogen production device is greater than the amount of direct delivery power and the amount of power supplied to the storage battery, and the amount of direct delivery power is greater than the amount of power supplied to the storage battery;
When the third profit amount and the fourth profit amount are higher than the first profit amount, the storage battery and the hydrogen production device are controlled so as to approach a fourth target state in which the amount of power supplied to the hydrogen production device is greater than the amount of direct power supply and the amount of power supplied to the storage battery, and the amount of power supplied to the storage battery is greater than the amount of direct power supply.
The energy supply system according to claim 3. A combination of the capacity of the storage battery and the maximum power consumption of the hydrogen production device is determined according to the allowable change rate.
The energy supply system according to any one of claims 2 to 4. A control device for an energy supply system including a renewable energy power generation device that transmits at least a portion of electric power generated by utilizing renewable energy to a power grid, and a storage battery that is capable of charging the electric power generated by the renewable energy power generation device and transmitting at least a portion of the charged electric power to the power grid,
a control unit that controls the storage battery so that a rate of change in the amount of power transmitted to the power grid does not exceed a preset allowable rate of change, calculates a required SoC, which is a State of Charge (SoC) of the storage battery necessary to maintain the rate of change at or below the allowable rate of change by transmitting power from the storage battery when power generation by the renewable energy power generation device is stopped and the amount of power transmitted to the power grid drops to zero, and controls the storage battery so that the amount of power transmitted is reduced when the required SoC exceeds a current SoC of the storage battery.
Control device for energy supply system. A control method for an energy supply system including a renewable energy power generation device that transmits at least a portion of electric power generated by utilizing renewable energy to a power grid, and a storage battery that can be charged with electric power generated by the renewable energy power generation device and can transmit at least a portion of the charged electric power to the power grid, comprising:
controlling the storage battery so that a rate of change in the amount of power transmitted to the power grid does not exceed a preset allowable rate of change, and calculating a required SoC, which is a State of Charge (SoC) of the storage battery necessary to maintain the rate of change at or below the allowable rate of change by transmitting power from the storage battery when power generation by the renewable energy power generation device stops and the amount of power transmitted to the power grid drops to zero, and controlling the storage battery so that the amount of power transmitted is reduced when the required SoC exceeds a current SoC of the storage battery.
A method for controlling an energy supply system.

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