Charge / discharge control method for charging / discharging element and charge / discharge control device for charging / discharging element

Abstract

In peak-cut control, electric power discharged from a plurality of charging / discharging elements (EV1, EV2) is supplied to a load (5), thereby suppressing a peak of electric power to be supplied from the load (5) to an electric power system (10). In renewable energy surplus control, renewable electric power exceeding the electric power demand of the load (5) is charged in the plurality of charging / discharging elements (EV1, EV2). A charge / discharge control method according to the present invention comprises determining whether a control mode is the peak-cut control or the renewable energy surplus control, setting an index value for allowing the plurality of charging / discharging elements (EV1, EV2) to control charge / discharge electric power on the basis of a determination result of the control mode, and transmitting the set index value to each of the plurality of charging / discharging elements (EV1, EV2). A charge / discharge control device according to the present invention performs discharge restriction for changing, according to the renewable energy surplus control or the peak-cut control, a minimum value that the index value can take.

Description

Charge and Discharge Control Method for Charge and Discharge Elements and Charge and Discharge Control Device for Charge and Discharge Elements

[0001] The present invention relates to a charge and discharge control method for charge and discharge elements and a charge and discharge control device for charge and discharge elements.

[0002] Patent Document 1 discloses a power system that supplies power from a power grid and renewable power generated from renewable energy to a load that consumes power and a plurality of charge and discharge elements. In this power system, a peak cut mode in which a plurality of charge and discharge elements are discharged to suppress the peak of the power supplied from the power grid to the load, and a renewable energy utilization mode in which renewable power exceeding the required power of the load is charged to the plurality of charge and discharge elements are switched.

[0003] Japanese Patent Application Laid-Open No. 2024-36884

[0004] However, in the method disclosed in Patent Document 1, in the renewable energy utilization mode, a situation occurs in which a plurality of charge and discharge elements discharge prior to charging of the renewable power. Since the charge and discharge elements that are planned to be used also discharge, there is a problem that the stored power of the charge and discharge elements decreases when the charge and discharge elements are used.

[0005] [[ID=I5]] An object of the present invention is to provide a charge and discharge control method for charge and discharge elements and a charge and discharge control device for charge and discharge elements that can suppress a decrease in the stored power of any of the plurality of charge and discharge elements.

[0006] The charge and discharge control method according to one aspect of the present invention includes determining whether the control mode is peak cut control or renewable energy surplus control, determining an index value for controlling the charge and discharge power of a plurality of charge and discharge elements based on the determination result of the control mode, and transmitting the set index value to each of the plurality of charge and discharge elements. The charge and discharge control device performs a discharge restriction that changes the minimum value that the index value can take between renewable energy surplus control and peak cut control.

[0007] According to one aspect of the present invention, it is possible to suppress a decrease in the stored power of any of the plurality of charge and discharge elements.

[0008] Figure 1 is a schematic diagram showing the configuration of the power system according to this embodiment. Figure 2 is a diagram illustrating peak cut control. Figure 3 is a diagram illustrating renewable energy surplus control. Figure 4 is a diagram illustrating time-of-day energy management. Figure 5 is a diagram illustrating the occurrence of charge and discharge losses. Figure 6 is a diagram illustrating the discharge index threshold. Figure 7 is a flowchart of the charge and discharge control method according to this embodiment. Figure 8 is a flowchart of the method for determining the charge index threshold and the discharge index threshold. Figure 9 is a diagram showing the charge index threshold and the discharge index threshold. Figure 10 is a flowchart of charge and discharge control in individual electric vehicles.

[0009] The following describes a power system equipped with a charge / discharge control device according to this embodiment, and a method for controlling the charge and discharge of charge / discharge elements, with reference to the drawings.

[0010] As shown in Figure 1, the power system 100 is a system that manages the supply and demand of electricity for commercial facilities, factories, etc. The power system 100 comprises a control server 1, a power grid 10, first and second power receiving devices 3A and 3B, first and second electric vehicles EV1 and EV2, a load 5, and renewable energy supply equipment 7. The power system 100 is a system that supplies electricity from the power grid 10 and renewable electricity generated from renewable energy sources to the power-consuming load 5 and the first and second electric vehicles EV1 and EV2. In this embodiment, the first and second electric vehicles EV1 and EV2 are exemplified, but there may be three or more electric vehicles. Similarly, the first and second power receiving devices 3A and 3B are exemplified, but there may be three or more power receiving devices.

[0011] The power system 10 is a system that can control the flow of electricity from both the supply and demand sides and optimize the flow of electricity. The power system 10 is a concept that includes smart grids, smart communities, and microgrids or MEMS (Mansion Energy Management Systems) that manage energy from the supply source to the consumption part via a communication network within a limited area such as a business office or factory. The power system 10 includes a power grid 11, power lines 12, transformers 14, and multiple current measuring devices 15A, 15B.

[0012] The power grid 11 includes various power plants such as thermal, nuclear, and hydroelectric power plants, as well as substations that transform voltages from several hundred thousand volts to several thousand volts. The power lines 12 are connected to the power grid 11 via transformers 14 and current measuring devices 15A. The power lines 12 are also connected to the first and second power receiving and supply devices 3A and 3B via current measuring devices 15B, and are also connected to the load 5 and the renewable energy supply equipment 7. An example of a transformer 14 is a pole-mounted transformer (pole transformer) that changes the voltage applied to high-voltage distribution lines to the voltage used in homes and offices.

[0013] Multiple current measuring devices 15A and 15B measure the current flowing through the power line 12 and calculate the grid power supplied via the power line 12 based on the measured current and the voltage of the power line 12. For example, current measuring device 15A calculates the grid power supplied from the power system 10, and current measuring device 15B calculates the charge / discharge power being charged by the first and second electric vehicles EV1 and EV2 or being discharged by the first and second electric vehicles EV1 and EV2. Each current measuring device 15A and 15B transmits the calculated power to the control server 1.

[0014] The control server 1 is a server that supplies power from the power grid 10 and renewable power to the load 5 and the first and second electric vehicles EV1 and EV2, and controls the charging and discharging of the first and second electric vehicles EV1 and EV2. The control server 1 communicates with a plurality of current measuring devices 15A and 15B to obtain grid power and the charging and discharging power of the first and second electric vehicles EV1 and EV2. The control server 1 also communicates with the first and second electric vehicles EV1 and EV2 to control the charging and discharging of the electric vehicles EV1 and EV2.

[0015] The control server 1 comprises a charge / discharge control device 21, a transmission processing unit 23a, and a transmission device 23b.

[0016] The charge / discharge control device 21 is a controller composed of a general-purpose electronic circuit including a CPU and peripheral devices such as memory. The charge / discharge control device 21 has computer programs installed to execute various functions related to charge / discharge control. Each function executed by the charge / discharge control device 21 can be implemented by one or more processing circuits.

[0017] The charge / discharge control device 21 includes two switchable control modes: peak cut control and renewable energy surplus control. Details of peak cut control and renewable energy surplus control will be described later. The charge / discharge control device 21 determines an index value for controlling the charge / discharge power of the first and second electric vehicles EV1 and EV2, according to the control mode.

[0018] The transmission processing unit 23a uses the transmission device 23b to broadcast the index value generated by the charge / discharge control device 21 to all electric vehicles EV1 and EV2. Wireless communication technologies such as wireless LAN (Local Area Network) and Bluetooth® can be used as the method of broadcasting.

[0019] The first and second power receiving devices 3A and 3B charge and discharge the first and second electric vehicles EV1 and EV2. The first and second power receiving devices 3A and 3B are connected to the electric wire 12, respectively. The first and second power receiving devices 3A and 3B are also connected to the first and second electric vehicles EV1 and EV2, respectively, for example, by power connectors. Each power receiving device 3A and 3B charges the electric vehicles EV1 and EV2 connected to them. Each power receiving device 3A and 3B also discharges power from the electric vehicles EV1 and EV2 connected to them. Note that the power receiving devices 3A and 3B may be installed outside the vehicle bodies of the electric vehicles EV1 and EV2, or they may be located inside the electric vehicles EV1 and EV2.

[0020] Load 5 is a facility that consumes electricity, such as a commercial building or factory. Load 5 is supplied with the electricity it needs.

[0021] The renewable energy supply equipment 7 is equipment for generating electricity using renewable energy and supplying the generated renewable electricity. For example, the renewable energy supply equipment 7 is a solar power generation system equipped with solar panels. The renewable energy supply equipment 7 supplies renewable electricity to load 5 and electric vehicles EV1 and EV2. However, the generation of electricity using renewable energy is not limited to solar power generation; other power generation methods that utilize renewable energy may also be used.

[0022] The first and second electric vehicles EV1 and EV2 are electrically connected to the power grid 11 via the first and second power receiving and supply devices 3A and 3B. Each electric vehicle EV1 and EV2 is equipped with a rechargeable battery. The electric vehicles EV1 and EV2 can receive power from the power grid 11 (charge) and transmit power to the power grid 11 (discharge). Each electric vehicle EV1 and EV2 autonomously controls charging and discharging according to an index value transmitted from the charge / discharge control device 21.

[0023] The charging and discharging units 25A and 25B determine their own priority, that is, the priority of the electric vehicles EV1 and EV2 on which they are installed. The priority increases as the amount of charge (SOC: state of charge) of the first electric vehicle EV1 decreases. The priority increases as the time until the first electric vehicle EV1 can be put into use decreases. The priority increases as the planned driving distance of the first electric vehicle EV1 increases. The charging and discharging unit 25A determines the priority by comprehensively considering factors such as the amount of charge of the first electric vehicle EV1, the time until the first electric vehicle EV1 can be put into use, and the planned driving distance of the first electric vehicle EV1.

[0024] Priority is a parameter that indicates the need for charging in electric vehicles EV1 and EV2. By following this priority, electric vehicles EV1 and EV2 with higher priority will be charged more often, and electric vehicles EV1 and EV2 with higher priority will have less discharge. In other words, electric vehicles EV1 and EV2 with higher priority will have more opportunities to be charged than electric vehicles EV1 and EV2 with lower priority, and electric vehicles EV1 and EV2 with higher priority will have fewer opportunities to be discharged than electric vehicles EV1 and EV2 with lower priority. Note that priority may also be based on the magnitude of the charge / discharge power rather than the frequency of charge / discharge opportunities.

[0025] The charge / discharge units 25A and 25B determine the charge / discharge power of the electric vehicles EV1 and EV2 based on the determined priority and the index value obtained from the charge / discharge control device 21. Based on the determined charge / discharge power, the charge / discharge units 25A and 25B perform charging and discharging of the electric vehicles EV1 and EV2. The charge / discharge units 25A and 25B may also be mounted on the power receiving and supply devices 3A and 3B.

[0026] In this embodiment, the "electric vehicle" is an example of a "charge / discharge element" that charges and discharges power via the electric wire 12. The charge / discharge element stores the received power in a battery (including secondary batteries, storage batteries, and rechargeable batteries). The "charge / discharge element" includes all equipment and devices equipped with batteries, such as vehicles (including electric vehicles, hybrid vehicles, construction machinery, and agricultural machinery), railway vehicles, playground equipment, tools, home appliances, and daily necessities. In this embodiment, an electric vehicle (EV) that runs using electricity as an energy source and a motor as a power source is given as an example of a charge / discharge element. However, the present invention is not intended to limit the charge / discharge element to electric vehicles (EVs).

[0027] The term "charge / discharge element" indicates the unit configuration of charge / discharge control by the charge / discharge control device 21 according to this embodiment. That is, charge / discharge control according to this embodiment is performed using the charge / discharge element as the unit. For example, charge / discharge control is performed independently and in parallel for each of the first and second electric vehicles EV1 and EV2.

[0028] Referring to Figures 2 and 3, the indicator values, as well as peak cut control and renewable energy surplus control, will be explained. In the following explanation, it is assumed that the first electric vehicle EV1 has a higher priority and the second electric vehicle EV2 has a lower priority. In Figures 2 and 3, "Pe" shows the trend of renewable electricity, and "Pd" shows the trend of the sum of the demand power of load 5 and the power charged to the first and second electric vehicles EV1 and EV2.

[0029] The index value is an index value that each electric vehicle (EV1, EV2) uses to determine its own charging and discharging power. The index value can take on a range from a predetermined reference index value to a maximum charging index value which is greater than the reference index value, and a range from the reference index value to a minimum discharging index value which is less than the reference index value.

[0030] In this embodiment, the reference index value is "0". The maximum charge index value is "100", and the minimum discharge index value is "-100". However, these values ​​are just examples, and the reference index value, maximum charge index value, and minimum discharge index value may be other numbers.

[0031] If the index value is greater than the reference index value, that index value instructs the first and second electric vehicles EV1 and EV2 to be charged. More specifically, as the index value moves from the reference index value towards the maximum charge index value, the range of vehicles to be charged expands from the high-priority electric vehicle EV1 to the low-priority electric vehicle EV2. In other words, when the index value is close to the reference index value, the high-priority electric vehicle EV1 is charged, and as the index value approaches the minimum discharge index value, both the high-priority electric vehicle EV1 and the low-priority electric vehicle EV2 are charged.

[0032] Conversely, if the index value is smaller than the reference index value, that index value instructs the first and second electric vehicles EV1 and EV2 to discharge. More specifically, as the index value moves from the reference index value towards the minimum discharge index value, the target of discharge expands from the low-priority electric vehicle EV2 to the high-priority electric vehicle EV1. In other words, the closer the index value is to the reference index value, the more the low-priority electric vehicle EV2 will discharge, and as the index value approaches the minimum discharge index value, the more the high-priority electric vehicle EV1 will discharge in addition to the low-priority electric vehicle EV2.

[0033] First, let's explain peak cut control with reference to Figure 2. Peak cut control is a control method that suppresses the peak of power supplied from the power system 10 to load 5 by discharging power from the first and second electric vehicles EV1 and EV2 and supplying the discharged power to load 5. A power peak refers to a state in which the power demand of load 5 exceeds a preset peak power threshold. In Figure 2, the period from 11:00 to 15:00 is shown as an example of a peak time period in which a power peak occurs.

[0034] The charge / discharge control device 21 increases the index value to the maximum charge index value before the peak time period arrives. This ensures that charging is performed in the first and second electric vehicles EV1 and EV2, thereby securing power to be supplied to the load 5 from the first and second electric vehicles EV1 and EV2 during the peak time period. When the peak time period begins, the charge / discharge control device 21 decreases the index value according to the peak cut power, which is calculated by subtracting the peak power threshold from the demand power of the load 5. If the peak cut power is large, the index value reaches the minimum discharge index value. As a result, power is discharged from the first and second electric vehicles EV1 and EV2, and power is supplied to the load 5 from the first and second electric vehicles EV1 and EV2. After the peak time period has passed, the charge / discharge control device 21 increases the index value to the maximum charge index value.

[0035] Referring to Figure 3, the renewable energy surplus control will be explained. Renewable energy surplus refers to a state in which the renewable electricity generated by the renewable energy supply equipment 7 is greater than the power demanded by the load 5. In this embodiment, a solar power generation system is assumed to be the renewable energy supply equipment 7, so in Figure 3, the period from 6:00 to 17:00 is depicted as a state of renewable energy surplus. Renewable energy surplus control is a control method that effectively utilizes renewable electricity by charging the first and second electric vehicles EV1 and EV2 with the surplus renewable electricity when there is a renewable energy surplus.

[0036] The charge / discharge control device 21 lowers the index value to the minimum discharge index value during the time period prior to the arrival of the energy surplus period when renewable energy surplus occurs. As a result, the power of the first and second electric vehicles EV1 and EV2 is discharged, and the amount of energy stored in the first and second electric vehicles EV1 and EV2 can be reduced in order to absorb renewable energy to the maximum extent. When the energy surplus period begins, the charge / discharge control device 21 increases the index value according to the surplus renewable energy. If the surplus renewable energy is large, the index value reaches the maximum charge index value. As a result, the first and second electric vehicles EV1 and EV2 are charged with renewable energy, and the surplus renewable energy can be absorbed. After the energy surplus period has passed, the charge / discharge control device 21 lowers the index value to the minimum discharge index value.

[0037] The charge / discharge control device 21 switches between peak cut control and renewable energy surplus control at appropriate timings based on a forecast of the trend of renewable electricity generated at the renewable energy supply facility 7 and a forecast of the trend of demand electricity from the load 5.

[0038] Incidentally, during periods when there is no surplus of renewable energy, the indicator value is the minimum discharge indicator value, so both the high-priority first electric vehicle EV1 and the low-priority second electric vehicle EV2 will discharge. In particular, if discharge occurs during the nighttime, it may result in a situation where, when trying to use the high-priority first electric vehicle EV1 the next morning, there is not enough charge remaining to use the first electric vehicle EV1.

[0039] Therefore, this embodiment introduces two features: (1) changing the minimum value of the indicator value, and (2) time-of-day energy management. These features will be explained with reference to Figures 4 to 6.

[0040] (Feature 1) "Changing the minimum value of the index value" is a concept that changes the minimum value that the index value can take in renewable energy surplus control and peak cut control. Specifically, the charge / discharge control device 21 sets a discharge index threshold in renewable energy surplus control. When the discharge index threshold is set, the minimum value that the index value can take is limited to the discharge index threshold (discharge limit). The discharge index threshold is a value that is smaller than the reference index value and larger than the minimum discharge index value. In renewable energy surplus control, since the discharge index threshold is set, the charge / discharge control device 21 determines the index value with the discharge index threshold as the lower limit. The discharge index threshold is applied to renewable energy surplus control but not to peak cut control. Therefore, in peak cut control, the charge / discharge control device 21 determines the index value with the minimum discharge index value as the lower limit.

[0041] Figure 5 shows a state where the index value is limited by the discharge index threshold between 0:00 and 6:00. In the example in Figure 5, "-50" is given as the discharge index threshold. When the index value is limited, the discharge of the high-priority first electric vehicle EV1 is suppressed, and the discharge of the low-priority second electric vehicle EV2 is permitted. Since the discharge of the first electric vehicle EV1 is suppressed, even when attempting to use the first electric vehicle EV1 the next morning, sufficient stored energy can be secured in the first electric vehicle EV1 for use. On the other hand, since the low-priority second electric vehicle EV2 discharges, it can be prepared to absorb the surplus of renewable energy.

[0042] (Feature 2) "Time-based energy management" is a concept in which a management time period is set before the time period in which discharge restrictions are implemented, and during this management time period, the first electric vehicle EV1, which has a high priority, is given priority for charging. Specifically, the charge / discharge control device 21 sets a charge index threshold during the management time period. When the charge index threshold is set, the maximum value that the index value can take is limited to the charge index threshold (charge restriction). The discharge index threshold is a value that is smaller than the reference index value and also smaller than the maximum charge index value. Since the charge index threshold is set during the management time period, the charge / discharge control device 21 determines the index value with the charge index threshold as the upper limit. The management time period is applied to both renewable energy surplus control and peak cut control.

[0043] Figure 5 shows a state in which the indicator value is limited by the charging indicator threshold during the management period from 18:00 to 0:00 the following day. In the example in Figure 5, "50" is given as the charging indicator threshold. When the indicator value is limited, charging of the high-priority first electric vehicle EV1 is permitted, and charging of the low-priority second electric vehicle EV2 is suppressed. Since charging is carried out in the first electric vehicle EV1, sufficient energy storage can be secured in the first electric vehicle EV1 when it is to be used the following morning. The management period and charging indicator threshold are applied not only to renewable energy surplus control but also to peak cut control, as shown in Figure 4. Since charging of the low-priority second electric vehicle EV2 is limited, preparations can be made for absorbing the renewable energy surplus.

[0044] For example, the management time period is set as follows. The start time of the management time period is determined based on the time when power generation becomes impossible in the renewable energy supply facility 7. On the other hand, the end time of the management time period is determined based on the time sufficient to fully charge a high-priority electric vehicle during the management time period and the time sufficient for a low-priority electric vehicle to fully discharge in anticipation of excess renewable energy. In the example shown in FIG. 5, the period from 18:00 to 0:00 the next day is set as the management time period. However, as long as it is determined according to the above concept, the management time period is not limited to this. For example, since the sunshine duration is long in summer, the start time of the management time period may be set to 19:00.

[0045] By the way, when performing time-zone energy management, the following problems may occur. As shown in FIG. 6, in the charging priority time zone, charging of the high-priority first electric vehicle EV1 is performed. When the charging priority time zone ends, the power storage amount of the first electric vehicle EV1 increases, so the priority of the first electric vehicle EV1 relatively decreases. For this reason, the first and second electric vehicles EV1 and EV2 have the same level of priority, and in the subsequent time zones, not only the first electric vehicle EV1 but also the second electric vehicle EV2 will perform discharging. As a result of discharging in anticipation of excess renewable energy in this way, charge and discharge are repeated in the first electric vehicle EV1, and charge and discharge losses occur.

[0046] Therefore, in the present embodiment, the charge index threshold value and the discharge index threshold value are appropriately determined. Thereby, as shown in FIG. 5, in the discharge process prior to the excess renewable energy, the index value is determined so that only the low-priority second electric vehicle EV2 performs discharging.

[0047] Hereinafter, referring to FIG. 7, a charge and discharge control method by the charge and discharge control device 21 will be described. First, the charge and discharge control device 21 determines whether the current time is included in the management time period (S10).

[0048] When the current time is included in the management time zone (S10: Yes), the charge / discharge control device 21 determines whether a power peak has occurred (S11). When a power peak has occurred (S11: Yes), the charge / discharge control device 21 decreases the index value so that the peak cut power can be covered by the discharge of the first and second electric vehicles EV1 and EV2 (S12). Since the index value has the discharge minimum index value as the lower limit, when the peak cut power is large, the index value reaches the discharge minimum index value. On the other hand, when no power peak has occurred (S11: No), the charge / discharge control device 21 increases the index value to the charge index threshold (S13). At this time, since the index value is limited to the charge index threshold, charging of the first electric vehicle EV1 with high priority is permitted, and charging of the second electric vehicle EV2 with low priority is restricted.

[0049] When the current time is not included in the management time zone (S10: No), the charge / discharge control device 21 determines whether the current control mode is peak cut control (S14). When the current control mode is peak cut control (S14: Yes), the charge / discharge control device 21 performs the process of step S15. When the current control mode is renewable energy surplus control (S14: No), the charge / discharge control device 21 performs the process of step S18.

[0050] The charge / discharge control device 21 determines whether a power peak has occurred (S15). When a power peak has occurred (S15: Yes), the charge / discharge control device 21 decreases the index value so that the peak cut power can be covered by the discharge of the first and second electric vehicles EV1 and EV2 (S16). Since the index value has the discharge minimum index value as the lower limit, when the peak cut power is large, the index value reaches the discharge minimum index value. On the other hand, when no power peak has occurred (S15: No), the charge / discharge control device 21 increases the index value to the charge maximum index value in preparation for the occurrence of a power peak (S17).

[0051] The charge / discharge control device 21 determines whether or not a surplus of renewable energy has occurred (S18). If a surplus of renewable energy has occurred (S18: Yes), the charge / discharge control device 21 increases the index value so that renewable power can be absorbed by charging the first and second electric vehicles EV1 and EV2 (S19). Since the index value is capped at the maximum charging index value, if the surplus power is large, the index value will reach the maximum charging index value. On the other hand, if there is no surplus of renewable energy (S18: Yes), the charge / discharge control device 21 increases the index value to the discharge index threshold (S20). Since the index value is limited to the discharge index threshold, the discharge of the high-priority first electric vehicle EV1 is restricted, and the discharge of the low-priority second electric vehicle EV2 is permitted.

[0052] Once the indicator value is determined in the charge / discharge control device 21, the transmission processing unit 23a transmits (broadcasts) the indicator value to all electric vehicles EV1 and EV2.

[0053] Referring to Figures 8 and 9, the process for determining the charge index threshold and discharge index threshold used in charge / discharge control will be explained. This process is performed when the power system 100 starts operation, but it may also be performed at regular intervals, such as seasonally or daily. In Figure 9, L1 and L2 are models showing the trajectories of the charge / discharge power of electric vehicles EV1 and EV2 in response to increases and decreases in index values. In this model, the higher the priority of electric vehicles EV1 and EV2, the further to the left it shifts, and the lower the priority of electric vehicles EV1 and EV2, the further to the right it shifts.

[0054] First, the charge / discharge control device 21 calculates the renewable energy surplus threshold (S30). Specifically, the charge / discharge control device 21 predicts the amount of renewable energy surplus by subtracting the predicted value of the power demand of load 5 from the predicted value of renewable power (S30a). The predicted value of renewable power and the predicted value of the power demand of load 5 are predicted in advance from past actual values ​​of renewable power and actual values ​​of the power demand of load 5. Next, the charge / discharge control device 21 calculates the number of electric vehicles required to absorb the renewable energy surplus, based on the discharge time that electric vehicles can discharge in renewable energy surplus control and the discharge output per electric vehicle (S30b). Then, the charge / discharge control device 21 determines the indicator value at which the number of electric vehicles required to discharge will discharge as the renewable energy surplus threshold (S30c). In Figure 9, the renewable energy surplus threshold is shown as "Th1".

[0055] The charge / discharge control device 21 records actual data related to charge / discharge control. The actual data includes an index value and the amount of discharged by the electric vehicles EV1 and EV2 at that index value. Based on the actual data, the charge / discharge control device 21 learns the expected discharge amount (expected discharge amount) for each day of the week and season. In the process of step S30 described above, the renewable energy surplus threshold is determined using the learned result of the expected discharge amount.

[0056] Next, the charge / discharge control device 21 calculates the discharge limit threshold (S31). The discharge limit threshold is an indicator value at which the highest priority electric vehicle begins to discharge. "L1" in Figure 9 shows the relationship between the indicator value and the charge / discharge power of the highest priority electric vehicle. In Figure 9, the discharge limit threshold is indicated by "Th2".

[0057] The charge / discharge control device 21 compares the regenerative energy surplus threshold and the discharge limit threshold, and determines the larger of the two values ​​as the discharge index threshold (S32). In Figure 9, the discharge index threshold is indicated as "Th4".

[0058] The charge / discharge control device 21 determines the threshold priority. This threshold priority is the priority for electric vehicles that will not start discharging until the discharge index threshold determined in step S32 is reached (S33). In other words, an electric vehicle with threshold priority is an electric vehicle that is excluded from being discharged during the time period when the minimum value that the index value can take is limited to the discharge index threshold, that is, during the time period when discharge restrictions are in place (an electric vehicle with a specific priority). "L2" in Figure 9 shows the relationship between the index value and the charge / discharge power of an electric vehicle with threshold priority.

[0059] Based on the threshold priority determined in step S33, the charge / discharge control device 21 determines the maximum index value at which the electric vehicle with the threshold priority does not charge as the charging index threshold. In Figure 9, the charging index threshold is indicated as "Th3".

[0060] Through this series of procedures, the charge index threshold and discharge index threshold are determined and used in the charge / discharge control shown in Figure 8 above.

[0061] Referring to Figure 10, the charge and discharge control in each electric vehicle EV1 and EV2 will be explained. The following explanation describes the process in the first electric vehicle EV1, but the process in the second electric vehicle EV2 is similar.

[0062] The charging / discharging unit 25A obtains an index value from the control server 1 (S40). The charging / discharging unit 25A calculates the priority of the first electric vehicle EV1 (S41).

[0063] The charging / discharging unit 25A determines whether charging / discharging is possible and, if so, the charging / discharging power, based on an index value and priority.

[0064] In this way, the power used for charging and discharging is determined for each electric vehicle EV1 and EV2. For example, if the index value is equal to the maximum charging index value, all electric vehicles EV1 and EV2, including the second electric vehicle EV2 with lower priority, will be charged. On the other hand, if the index value is equal to the charging index threshold, the first electric vehicle EV1 with higher priority will be charged, while the second electric vehicle EV2 with lower priority will not be charged.

[0065] Furthermore, if the indicator value is the minimum discharge indicator value, discharge will occur in all electric vehicles EV1 and EV2, including the high-priority first electric vehicle EV1. On the other hand, if the indicator value is the discharge indicator threshold, the low-priority second electric vehicle EV2 will discharge, while the high-priority first electric vehicle will not.

[0066] As described above, this embodiment changes the minimum value that the index value can take in renewable energy surplus control and peak cut control. This makes it possible to suppress the decrease in the amount of stored energy for any of the first and second electric vehicles EV1 and EV2.

[0067] According to this embodiment, in renewable energy surplus control, the minimum value that the index value can take is limited to a discharge index threshold that is greater than the minimum discharge index value. As a result, discharge to the first electric vehicle EV1, which has a higher priority than the first and second electric vehicles EV1 and EV2, is suppressed. Consequently, the decrease in the amount of stored energy in the first electric vehicle EV1, which has a higher priority, can be suppressed.

[0068] According to this embodiment, during the management period, the maximum value that the indicator value can take is limited to a charging indicator threshold that is smaller than the maximum charging indicator value. As a result, charging of the second electric vehicle EV2, which has a lower priority, is suppressed, while charging of the first electric vehicle EV1, which has a higher priority, is permitted. Consequently, the amount of stored energy in the first electric vehicle EV1, which has a higher priority, can be secured.

[0069] According to this embodiment, an index value at which electric vehicles of a specific priority do not charge during the management period is determined as the charging index threshold. Here, electric vehicles of a specific priority refer to electric vehicles that are excluded from being discharged during the period when the minimum value that the index value can take is limited to the discharge index threshold. With this method, even high-priority charge / discharge elements that have been charged during the management period will have their charging restricted, and a significant decrease in priority will be suppressed, thereby suppressing them from discharging during the subsequent period when discharge is restricted. This makes it possible to suppress the problem of repeated charging and discharging in the high-priority first electric vehicle EV1, which would otherwise result in charge / discharge losses.

[0070] As described above, embodiments of the present invention have been presented, but the statements and drawings that constitute part of this disclosure should not be understood as limiting the invention. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure.

[0071] 1: Control server 1, 10: Power system 10, 3A: Power receiving device, 3B: Power receiving device, EV1: First electric vehicle, EV2: Second electric vehicle, 5: Load 5, 7: Renewable energy supply equipment, 21: Charge / discharge control device, 23a: Transmission processing unit 23a, 23b: Transmission device

Claims

1. A power system that supplies power from a power grid and renewable power generated from renewable energy to a power-consuming load and a plurality of charge / discharge elements, wherein a charge / discharge control device that controls the charge / discharge of the plurality of charge / discharge elements performs a charge / discharge control method for the charge / discharge elements, wherein the charge / discharge control device includes, as switchable control modes: peak cut control, which suppresses the power peak supplied to the load from the power grid by supplying power discharged from the plurality of charge / discharge elements to the load; and renewable energy surplus control, which charges the plurality of charge / discharge elements with renewable power exceeding the load's demand power; the charge / discharge control method includes determining whether the control mode is the peak cut control or the renewable energy surplus control; determining an index value for controlling the charge / discharge power of the plurality of charge / discharge elements based on the determination result of the control mode; and transmitting the determined index value to each of the plurality of charge / discharge elements. The index value is a value that can take on a range from a reference index value to a maximum charge index value which is greater than the reference index value, and a range from the reference index value to a minimum discharge index value which is less than the reference index value, the index value indicates that as the value approaches the maximum charge index value from the reference index value, the target of charging expands from high-priority charge / discharge elements to low-priority charge / discharge elements which have a lower priority than the high-priority charge / discharge elements, the index value indicates that as the value approaches the minimum discharge index value from the reference index value, the target of discharging expands from low-priority charge / discharge elements which have a lower priority, the charge / discharge control device performs discharge limiting by changing the minimum value which the index value can take in terms of renewable energy surplus control and peak cut control, a method for controlling the charge / discharge of charge / discharge elements.

2. The charge-discharge control method for a charge-discharge element according to claim 1, wherein the discharge limiting restricts the minimum value that the index value can take in the renewable energy surplus control to a discharge index threshold that is greater than the minimum discharge index value, which is the minimum value that the index value can take in the peak cut control.

3. The charge / discharge control method for a charge / discharge element according to claim 2, wherein the charge / discharge control device sets a management time period before the time period in which the discharge limit is performed, and during the management time period, the charge / discharge control device performs a charge limit that restricts the maximum value that the index value can take to a charge index threshold that is smaller than the maximum charge index value.

4. The charge / discharge control method for a charge / discharge element according to claim 3, wherein the charge / discharge control device determines an index value at which the charge / discharge element of a specific priority does not perform charging during the management period is an index value at which the charge / discharge element of a specific priority does not perform charging during the management period, which is excluded from the target of discharge during the period in which the minimum value that the index value can take is limited to the discharge index threshold.

5. The charge / discharge control device predicts a renewable energy surplus amount in which the renewable power is greater than the power demanded by the load; determines the larger of the following two values ​​as the discharge index threshold: a renewable energy surplus threshold, which is the index value at which the number of charge / discharge elements necessary to absorb the renewable energy surplus amount begin to discharge, and a discharge limit threshold, which is the index value at which the highest priority charge / discharge element begins to discharge; determines the priority of the charge / discharge elements that do not begin to discharge up to the determined discharge index threshold as the threshold priority; and determines the maximum index value at which the charge / discharge element of the threshold priority does not charge, as the charge index threshold, according to claim 4.

6. In a power system that supplies power from a power grid and renewable power generated from renewable energy to a power-consuming load and a plurality of charge / discharge elements, a charge / discharge control device controls the charging and discharging of the charge / discharge elements, wherein the charge / discharge control device includes, as a switchable control mode, peak cut control which suppresses the power peak supplied to the load from the power grid by supplying the power discharged from the plurality of charge / discharge elements to the load, and renewable energy surplus control which charges the plurality of charge / discharge elements with the renewable power exceeding the load's demand power, the charge / discharge control device determines whether the control mode is the peak cut control or the renewable energy surplus control, determines an index value for controlling the charge / discharge power of the plurality of charge / discharge elements based on the determination result of the control mode, transmits the determined index value to each of the plurality of charge / discharge elements, and the index value is a value that can take a range from a reference index value to a maximum charge index value which is a value greater than the reference index value, and a range from the reference index value to a minimum discharge index value which is a value less than the reference index value. The index value indicates that as it moves from the reference index value towards the maximum charge index value, the targets of charging expand from high-priority charge / discharge elements to low-priority charge / discharge elements with a lower priority than the high-priority charge / discharge elements; the index value indicates that as it moves from the reference index value towards the minimum discharge index value, the targets of discharging expand from low-priority charge / discharge elements to high-priority charge / discharge elements; and the charge / discharge control device performs discharge limiting by changing the minimum value that the index value can take in the renewable energy surplus control and the peak cut control, thereby controlling the charge / discharge of charge / discharge elements.

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