JP7776296B2 - Power Supply System - Google Patents

Description

The present invention relates to technology for a power supply system equipped with a storage battery that can charge and discharge power.

Technology for power supply systems that include a storage battery connected between a grid power supply and a load and control the charging and discharging of the storage battery is well known. For example, see Patent Document 1.

Patent Document 1 describes a battery storage system in which a battery is connected to an electrical circuit connecting a commercial grid to a load. With this configuration, a relatively large amount of power stored in the battery can be supplied to the load as needed.

In such battery storage systems, electricity charges are collected for the electricity purchased from the commercial grid. One of the terms of the electricity rate contract is the demand charge system. The demand charge system determines the monthly contract power based on the greater of the maximum demand value (maximum power demand) for that month or the maximum power demand over the past 11 months. Here, the demand value refers to the average power usage within a 30-minute period (demand time limit), and the maximum value of this demand value is called the maximum demand value. Therefore, in order to reduce electricity charges under the demand charge system, it is desirable to find ways to lower the maximum demand value.

JP 2012-44733 A

The present invention was made in consideration of the above situation, and the problem it aims to solve is to provide a power supply system that can reduce electricity charges by lowering the maximum demand value.

The above is the problem that this invention aims to solve, and next we will explain the means for solving this problem.

That is, in claim 1, there is provided a power supply system for supplying power to a load connected to a grid power source, the power supply system comprising: a storage battery connected between the grid power source and the load and capable of charging and discharging power from a predetermined supply source; and a control unit for controlling charging and discharging of the storage battery, wherein a remaining charge lower limit value indicating a lower limit value of power that can be discharged under normal circumstances out of a remaining charge amount is set for the storage battery, and when the control unit predicts that a demand value for each demand time limit will exceed a first reference value during the demand time limit, it calculates an emergency discharge permission number which is the number of the storage batteries that need to start discharging in order to prevent the demand value from exceeding the first reference value, and issues an emergency discharge instruction to discharge from the storage batteries determined based on the emergency discharge permission number, and when the control unit predicts that the remaining charge amount of the determined storage batteries will exceed the remaining charge amount, the control unit calculates ... If there is a storage battery whose remaining charge is below the lower limit, the remaining charge lower limit of that storage battery is lowered before the emergency discharge instruction is given, and if the emergency discharge instruction is cancelled, the lower remaining charge limit is raised to the original remaining charge lower limit, and after the emergency discharge instruction is cancelled, if it is predicted that the demand value of that demand time period will not exceed a second reference value that is smaller than the first reference value during each demand time period, a number of storage batteries permitted for priority charging is calculated, which is the number of storage batteries whose demand value will not exceed the second reference value even when charged, and the storage batteries to be charged are determined based on the number of storage batteries permitted for priority charging, and if there is a storage battery among the determined storage batteries whose remaining charge is less than the original lower limit, a priority charge instruction is given to charge that storage battery until its remaining charge reaches the original lower limit .

In claim 2, the control unit is capable of acquiring the amount of power used from the grid power source, and determines whether the demand value for the demand time limit exceeds the first reference value based on the actual value of the amount of power used up to the present time during the demand time limit and the predicted value of the amount of power used for the remaining time during the demand time limit.

In claim 3, the control unit calculates a predicted value of the amount of electricity used for the remaining time based on the amount of electricity used during the most recent predetermined period.

In claim 4, a plurality of the storage batteries are provided, and the control unit issues the emergency discharge instruction to the storage batteries in order of the remaining charge, starting with the storage battery with the greatest remaining charge.

In claim 5, if the control unit predicts that the demand value for the demand time limit will not exceed the first reference value or the second reference value after issuing the emergency discharge instruction, it calculates the number of emergency discharge cancellations, which is the number of storage batteries whose remaining capacity lower limit values have been lowered and whose demand values will not exceed the second reference value even if the remaining capacity lower limit values are raised, and cancels the emergency discharge instruction for the storage batteries determined based on the number of emergency discharge cancellations .

In claim 6 , a plurality of the storage batteries are provided, and when there are a plurality of storage batteries whose remaining charge is less than the increased lower limit value, the control unit issues the priority charging instruction to the storage batteries in order of the least remaining charge.

The effects of the present invention are as follows:

In claim 1, the maximum demand value can be lowered to reduce electricity charges. Furthermore, the unnecessary use of power reserved for emergencies such as power outages can be further suppressed. Furthermore, power reserved for emergencies such as power outages can be stored in a storage battery.

In claim 2, demand values can be predicted with high accuracy.

In claim 3, demand values can be predicted with greater accuracy.

In claim 4, the maximum demand value can be efficiently reduced.

Claim 5 makes it possible to prevent unnecessary use of power reserved for emergencies such as power outages.

In the sixth aspect, the storage battery can be efficiently charged.

1 is a block diagram showing the configuration of a power supply system according to an embodiment of the present invention; FIG. 4 is a block diagram showing an example of a power supply mode when a charge/discharge mode is executed. FIG. 10 is a block diagram showing an example of a power supply mode when the remaining charge of the storage battery decreases and reaches a remaining charge lower limit value when the charge/discharge mode is executed. 4 is a flowchart showing a flow relating to a power supply mode. 10 is a flowchart showing an emergency discharge flow. FIG. 6 is a continuation of FIG. 5 . 10 is a flowchart showing a priority discharge flow. FIG. 10 is a block diagram showing an example of a power supply mode when a demand value excess suppression function is executed. FIG. 10 is a block diagram showing the configuration of another example of a power supply system according to an embodiment of the present invention.

The following describes a power supply system 1 according to one embodiment of the present invention.

The power supply system 1 shown in FIG. 1 supplies power from a power grid S or power generated using solar power to a load H. The power supply system 1 according to this embodiment is installed in an office T. Electrical devices (load group H) that consume power are installed in the office T. In this embodiment, three load groups HA, HB, and HC are installed in the office T. The load group H is connected to the power grid S.

In office T, the power purchased from the grid power supply S can be used to power the load group H. When power is purchased from the grid power supply S, an electricity fee for the purchased power is collected from the electric power company. In this embodiment, it is assumed that the office's electricity contract uses a demand-based pricing system.

As mentioned above, the demand pricing system is a system in which the contracted power for each month is determined based on the greater of the maximum demand value (maximum power demand) for that month or the maximum power demand for the past 11 months. Demand value refers to the average power usage within a 30-minute period (demand time limit), and the maximum value of this demand value is called the maximum demand value.

The power supply system 1 according to this embodiment aims to reduce electricity charges under a demand-based pricing system by reducing the maximum demand value. The power supply system 1 includes a power distribution line 10, a smart meter 20, a power storage system 30, and a control unit 40.

The distribution line 10 connects a system power source S and three load groups H. Specifically, one end of the distribution line 10 is connected to the system power source S. The other end of the distribution line 10 branches into three, and each branched end is connected to a load group H. Note that, below, the one end of the distribution line 10 (the system power source S side) may be referred to as the "upstream side," and the other end (the load group H side) may be referred to as the "downstream side."

The smart meter 20 is capable of measuring power. The smart meter 20 is installed midway along the power distribution line 10 (near the grid power source S). The smart meter 20 is connected to the control unit 40 (described below) and can transmit measurement results to the control unit 40.

The power storage system 30 is capable of generating electricity using sunlight and charging and discharging power. The power storage system 30 includes a solar power generation unit 31, a storage battery 32, a power measurement unit 33, and a power conditioner 34.

The solar power generation unit 31 is a device that generates electricity using sunlight. The solar power generation unit 31 is composed of solar cell panels, etc. The solar power generation unit 31 is installed in a sunny location, such as on the roof of office T. The solar power generation unit 31 is connected to the power conditioner 34, which will be described later.

The storage battery 32 is capable of charging and discharging power. The storage battery 32 is composed of, for example, a lithium-ion battery. The storage battery 32 is connected to the power conditioner 34, which will be described later. The storage battery 32 has three operating modes: a discharge mode, a charge mode, a standby mode, and a charge/discharge mode. These modes will be described in detail later.

In this embodiment, the maximum discharge power of the storage battery 32 is assumed to be 2 kW. Also, the maximum charge power of the storage battery 32 is assumed to be 2 kW.

In addition, a predetermined remaining charge (hereinafter referred to as the "remaining charge lower limit") is set for the storage battery 32 as the remaining charge to ensure power in emergencies such as power outages. In other words, the remaining charge lower limit of the storage battery 32 indicates the minimum remaining charge that is always ensured under normal circumstances. The set remaining charge lower limit can be automatically changed when the demand value exceedance suppression function described below is executed. In this embodiment, the initial value of the remaining charge lower limit of the storage battery 32 (the value before change in the emergency discharge flow described below) is set to 50% of the storage capacity (maximum capacity). The remaining charge lower limit can be reduced in 10% increments.

In addition, a predetermined remaining charge (hereinafter referred to as the "minimum remaining charge") is set for the storage battery 32 as the remaining charge required to maintain the operating state of the storage battery 32. When the remaining charge reaches the minimum remaining charge, the storage battery 32 enters charging mode to maintain (protect) the operating state, and charging is forcibly performed. Unlike the lower limit value of the remaining charge, the minimum remaining charge cannot be changed. In this embodiment, the minimum remaining charge is set to 5% of the storage capacity (maximum capacity).

The power measurement unit 33 is capable of measuring power. The power measurement unit 33 is installed on the distribution line 10 immediately upstream of the connection between the power conditioner 34 (described below) and the distribution line 10. More specifically, the power measurement unit 33 is installed on the distribution line 10 so that no other electric wires or electrical devices are connected between the connection (between the power conditioner 34 and the distribution line 10) and the power measurement unit 33. The power measurement unit 33 is connected to the power conditioner 34 and can transmit measurement results to the power conditioner 34.

The power conditioner 34 is a hybrid power conditioner that can convert power appropriately. As described above, the power conditioner 34 is connected to the solar power generation unit 31 and the storage battery 32. The power conditioner 34 is also connected to a midpoint of the distribution line 10. In this way, the power conditioner 34 is provided between the solar power generation unit 31, the storage battery 32, and the distribution line 10.

As a result, the power generated by the solar power generation unit 31 can be output to the distribution line 10 via the inverter 34. The power generated by the solar power generation unit 31 can also be charged to the storage battery 32 via the inverter 34. The discharged power of the storage battery 32 can also be output to the distribution line 10 via the inverter 34. The power flowing through the distribution line 10 (power from the system power source S) can also be charged to the storage battery 32 via the inverter 34.

The power conditioner 34 is also connected to the power measurement unit 33 as described above. The power conditioner 34 can acquire information regarding the magnitude and direction (upstream or downstream) of the power flowing through the location where the power measurement unit 33 is installed. The power conditioner 34 can control the charging and discharging of the storage battery 32 based on the information acquired from the power measurement unit 33.

In this way, the power storage system 30 can output the power generated by the solar power generation unit 31 and the power discharged from the storage battery 32 to the power distribution line 10 via the power conditioner 34. The power storage system 30 can also charge the storage battery 32 via the power conditioner 34 with the power generated by the solar power generation unit 31 and the power from the grid power source S.

In this embodiment, three power storage systems 30 are provided. The three power storage systems 30 (more specifically, the power conditioners 34 of the power storage systems 30) are each connected to the power distribution line 10. Specifically, the three power storage systems 30 are connected one by one in sequence (series) in the direction of power flow between the smart meter 20 on the power distribution line 10 and the load group H.

The control unit 40 controls the operation of the power storage systems 30, thereby controlling the power supply mode in the power supply system 1. The control unit 40 is connected to the power conditioners 34 of each of the three power storage systems 30.

The control unit 40 can control the storage battery 32 via the power conditioner 34. Specifically, the control unit 40 can switch the operating mode of the storage battery 32. The control unit 40 can also change the lower limit of the remaining charge of the storage battery 32.

The control unit 40 can also obtain information about the power storage system 30 via the inverter 34. Specifically, the control unit 40 can obtain information about the remaining charge of the storage battery 32. The control unit 40 can also obtain information about the operating mode currently being performed by the storage battery 32.

The control unit 40 is also connected to the smart meter 20. The control unit 40 can acquire information related to measurement results from the smart meter 20. Specifically, the control unit 40 can acquire information related to the power received from the system power source S into the distribution line 10.

The control unit 40 can also perform various functions, including a demand value exceedance suppression function. A detailed explanation of the demand value exceedance suppression function will be provided later.

The control unit 40 can also execute a flow related to the power supply mode. As described below, the flow related to the power supply mode is composed of multiple flows (an emergency discharge flow, a priority charge flow, and a normal flow) that are executed sequentially. In the emergency discharge flow, priority charge flow, and normal flow, an appropriate mode is executed from the operating modes of the storage battery 32 as described above.

The following describes the operating modes of the storage battery 32 (discharge mode, charge mode, standby mode, and charge/discharge mode).

In this embodiment, as described above, three power storage systems 30 (i.e., three storage batteries 32) are provided, but the operating modes of each storage battery 32 are the same.

Discharge mode is a mode in which the storage battery 32 is discharged through load following operation. When discharge mode is executed, the storage battery 32 enters a state in which it can discharge according to the measurement results of the power measurement unit 33. Specifically, when the power measurement unit 33 measures the power flowing downstream, the storage battery 32 discharges the power corresponding to the measured power and enters a discharged state.

When the power measurement unit 33 measures the power flowing downstream, it is assumed that (when the solar power generation unit 31 is generating power) the power generated by the solar power generation unit 31 is being output to the distribution line 10, but is insufficient compared to the total power of the load group H.

Furthermore, when the discharge mode is executed, even if the power measurement unit 33 measures the power flowing downstream, if the remaining charge of the storage battery 32 is not sufficient to allow discharge (for example, if the remaining charge is at the lower limit or the minimum remaining amount), the storage battery 32 cannot be discharged and is switched to the standby mode described below.

Charging mode is a mode in which the storage battery 32 is charged. When charging mode is executed, the storage battery 32 is charged with the power generated by the solar power generation unit 31, prioritizing power from the grid power source S. Furthermore, when the power generated by the solar power generation unit 31 is less than the maximum charging power of the storage battery 32 or when the solar power generation unit 31 is not generating power, the storage battery 32 also charges with power from the grid power source S. Note that when part of the power generated by the solar power generation unit 31 is charged to the storage battery 32, the remainder of the generated power is output to the power distribution line 10.

Even if the charging mode is activated, if the storage battery 32 is fully charged, it cannot be charged and is switched to standby mode, which will be described later. In this case, all of the power generated by the solar power generation unit 31 is output to the power distribution line 10.

Standby mode is a mode in which the storage battery 32 is on standby. When standby mode is activated, the storage battery 32 remains in operation and does not charge or discharge.

The charge/discharge mode is a mode in which the storage battery 32 is charged and discharged through load following operation. When the charge/discharge mode is executed, the storage battery 32 is in a state in which it can be charged or discharged according to the measurement results of the power measurement unit 33.

Specifically, similar to the discharge mode, when the power measurement unit 33 measures the power flowing downstream, the storage battery 32 discharges the power corresponding to the measured power and enters a discharged state.

When the power measurement unit 33 measures the power flowing downstream, it is assumed that (when the solar power generation unit 31 is generating power) the power generated by the solar power generation unit 31 is being output to the distribution line 10, but is insufficient compared to the total power of the load group H.

Furthermore, when the charge/discharge mode is executed, even if the power measurement unit 33 measures the power flowing downstream, if the remaining charge of the storage battery 32 is not sufficient to allow discharge (for example, if the remaining charge is at the lower limit or the minimum remaining amount), the storage battery 32 cannot be discharged and is switched to standby mode.

Furthermore, when the charge/discharge mode is executed, if the power measurement unit 33 measures the power flowing upstream, the storage battery 32 is charged with power corresponding to the measured power and enters a charging state. Here, when the power measurement unit 33 measures the power flowing upstream, it is assumed that the power generated by the solar power generation unit 31 is output to the distribution line 10 and is in surplus to the load group H. In other words, if the power generated by the solar power generation unit 31 is in surplus to the load group H, the storage battery 32 charges only the surplus amount of the generated power.

Furthermore, when the charge/discharge mode is executed, even if the power generated by the solar power generation unit 31 is in excess of the load group H, the storage battery 32 cannot be charged if it is fully charged. In this case, the storage battery 32 remains in the charge/discharge mode and enters a standby state in which no charging or discharging takes place. In this case, all of the power generated by the solar power generation unit 31 is output to the power distribution line 10.

Furthermore, when the charge/discharge mode is executed, if the power measurement unit 33 does not measure the power flowing upstream or downstream, the storage battery 32 enters a standby state in which it maintains the charge/discharge mode but does not charge or discharge. A case in which the power measurement unit 33 does not measure the power flowing upstream or downstream is assumed to be, for example, a case in which the power generated by the solar power generation unit 31 is output to the distribution line 10 and is neither in surplus nor deficiency with respect to the load group H (a balanced state).

In this way, in the discharge mode or charge/discharge mode, the power output from the storage system 30 to the distribution line 10 (specifically, the power generated by the solar power generation unit 31 or the power discharged from the storage battery 32) is supplied to the load group H if there is no surplus power for the load group H.

In addition, in the discharge mode or charge/discharge mode, if the power output from the power storage system 30 to the power distribution line 10 (specifically, the power generated by the solar power generation unit 31) is in excess of the load group H, it is reverse-flowed to the grid power source S.

The process for switching the operating mode of the storage battery 32 is defined in the flow related to the power supply mode executed by the control unit 40. The flow related to the power supply mode will be explained later.

Below, an example of how power is supplied when the charge/discharge mode is executed is explained using Figures 2 and 3.

The block diagrams in Figures 2 and 3 show an example of the power supply mode when the charge/discharge mode is executed. The total power consumption of the load group H is assumed to be 50 kW. For the sake of convenience, in the explanation using the block diagrams in Figure 2 and subsequent figures, it is assumed that the solar power generation unit 31 is not generating power. For the sake of convenience, the control unit 40 and other components are not shown in Figure 3.

In the block diagrams that follow, the memory (four rectangular boxes) inside the storage battery 32 represents the remaining charge of the storage battery 32. Specifically, the number of colored boxes among the four rectangular boxes indicates the approximate ratio of the remaining charge to the maximum capacity. Black boxes indicate that the remaining charge is a dischargeable amount. Light black boxes indicate that the remaining charge is an amount that does not allow discharge (when the remaining charge is at the lower limit). That is, in Figure 2, all storage batteries 32 have a dischargeable remaining charge.

As shown in Figure 2, if the total load power of load group H is 50 kW, even if the three storage batteries 32 discharge their maximum discharge power (2 kW), this will still be insufficient for the total load power of load group H. Therefore, the power (44 kW) that makes up the shortfall in the discharge power of the three storage batteries 32 is received from the system power source S into the distribution line 10. In this way, the discharge power of the three storage batteries 32 and the power from the system power source S are supplied to load group H.

In a demand pricing system, electricity rates are determined based on the maximum demand value. Therefore, in order to reduce electricity rates, it is necessary to reduce the maximum demand value. Therefore, in this embodiment, the upper limit of the target demand value (hereinafter referred to as the "demand upper limit") is set to 45 kW. In the example shown in Figure 2, the power from the grid power source S (44 kW) is less than the demand upper limit (45 kW).

However, for example, if the remaining charge of the storage battery 32 decreases and reaches a lower limit as a result of continued discharging of the storage battery 32, the storage battery 32 will no longer be able to discharge. In this case, the amount of power received by the distribution line 10 from the system power source S will increase.

Figure 3 shows an example of the power supply state when the remaining charge of all storage batteries 32 decreases from the state shown in Figure 2 and reaches the remaining charge lower limit.

In this case, as shown in Figure 3, the three storage batteries 32 cannot discharge, so the power received by the distribution line 10 from the system power source S increases from 44 kW shown in Figure 2 to 50 kW. If this state of increased power received by the distribution line 10 continues, the demand value will exceed the demand upper limit (45 kW), resulting in a problem of relatively high electricity rates under the demand pricing system.

In contrast, the power supply system 1 according to this embodiment has a function for suppressing the maximum demand value (demand value suppression function). The demand value suppression function is executed by processing (emergency discharge flow) of the control unit 40.

The following explains the flow of power supply using the flowchart in Figure 4.

The flow relating to the power supply mode is repeatedly executed at a predetermined timing by the control unit 40. Note that the flow relating to the power supply mode is executed every minute during each demand time period (30 minutes).

In step S101, the control unit 40 calculates an expected demand value. Here, the "expected demand value" is a predicted value of the amount of power used (integrated value of power used) for the demand time period (hereinafter referred to as the "demand time period") to which the current time (the time of processing in step S101) belongs. The expected demand value is calculated using the following equation 1.
Estimated demand value = (demand time limit integrated value + maximum one-minute integrated value in the last n minutes × remaining time) × 2 (Equation 1)

Here, the "cumulative value of the demand time limit" is the cumulative value of the power from the grid power source S that has already been used by the load group H from the start of the demand time limit to the present time (power usage from the grid power source S). In other words, the "cumulative value of the demand time limit" is the actual value of the amount of power usage up to the present time during the demand time limit.

In this specification, "m-minute integrated value" refers to the integrated value (amount of power used) of power used from the grid power source S over m minutes. In other words, "the maximum value of the 1-minute integrated value in the last n minutes" refers to the largest value among the integrated values of power used over one minute over the last n minutes (e.g., 3 minutes). Furthermore, "remaining time" refers to the time from the current time to the end of the demand time limit. In other words, "the maximum value of the 1-minute integrated value in the last n minutes x the remaining time" refers to the (maximum) integrated value of power predicted to be used from the current time to the end of the demand time limit. Note that "the last n minutes" is not limited to the demand time limit in question, but may extend to the demand time limit before the demand time limit in question. Furthermore, multiplying by "2" is done to convert the 30-minute integrated value into a demand value.

After performing the processing of step S101, the control unit 40 proceeds to step S102.

In step S102, the control unit 40 executes an emergency discharge flow. The emergency discharge flow is a flow for executing the demand value excess suppression function. The emergency discharge flow will be described in detail later. After performing the processing of step S102, the control unit 40 proceeds to step S103.

In step S103, the control unit 40 determines whether emergency discharge is in progress. In this process, the control unit 40 makes this determination based on whether the emergency flag is ON. The emergency flag is a flag that indicates that the lower limit value of the remaining charge of the storage battery 32 has been lowered from its initial value. If the control unit 40 determines that emergency discharge is not in progress (the emergency flag is OFF) ("NO" in step S103), it proceeds to step S104. On the other hand, if the control unit 40 determines that emergency discharge is in progress (the emergency flag is ON) ("YES" in step S103), it temporarily ends the flow related to the power supply mode.

In step S104, the control unit 40 determines whether there are any storage batteries 32 whose remaining charge is less than a set value. This set value can be any value, for example, the initial value of the remaining charge lower limit (50%).

If the control unit 40 determines that there is a storage battery 32 whose remaining charge is less than the set value ("YES" in step S104), it proceeds to step S105. On the other hand, if the control unit 40 determines that there is no storage battery 32 whose remaining charge is less than the set value ("NO" in step S104), it proceeds to step S106.

In step S105, the control unit 40 executes a priority charging flow. The priority charging flow is a flow for preferentially charging storage batteries 32 whose remaining charge is less than a set value. A detailed description of the priority charging flow will be provided later. After performing the processing of step S105, the control unit 40 temporarily ends the flow related to the power supply mode.

In step S106, the control unit 40 executes the normal control flow. In the normal control flow, the control unit 40 executes the charge/discharge mode as the operating mode of the three storage batteries 32. In other words, when the normal control flow is executed, the three storage batteries 32 are ready to be charged or discharged according to the measurement results of the power measurement unit 33 (see Figure 2). After performing the process of step S106, the control unit 40 temporarily ends the flow related to the power supply mode.

The emergency discharge flow is explained in detail below using the flowcharts in Figures 5 and 6.

The emergency discharge flow occurs when the demand value is about to exceed the demand upper limit, and when the remaining charge reaches the lower limit and there is a storage battery 32 that cannot be discharged. This lower limit is changed (lowered) to enable the storage battery 32 to discharge again.

The emergency discharge flow consists of the process of lowering the remaining capacity lower limit of the storage battery 32 and discharging from the storage battery 32 (steps S201 to S211) as described above, and the process of raising (returning to the original value) the lower remaining capacity lower limit of the storage battery 32 and stopping discharging from the storage battery 32 (steps S301 to S312). This is explained in detail below.

First, we will explain the process (steps S201 to S211) for lowering the remaining charge lower limit of the storage battery 32 and discharging the storage battery 32.

In step S201, the control unit 40 determines whether the expected demand value is equal to or greater than the emergency discharge instruction condition multiplied by the safety factor. The expected demand value is the value calculated in step S101 of Figure 4. The "emergency discharge instruction condition" is the standard for determining whether to perform steps S209 and S210 (emergency discharge), which will be described later, and is set to the demand upper limit value (45 kW). In addition, to allow for a margin in case the demand value exceeds the limit, the emergency discharge instruction condition is multiplied by the safety factor. The safety factor is set to, for example, 0.8.

If the control unit 40 determines that the expected demand value is equal to or greater than the emergency discharge instruction condition multiplied by the safety factor (YES in step S201), the control unit 40 proceeds to step S202. On the other hand, if the control unit 40 determines that the expected demand value is less than the emergency discharge instruction condition multiplied by the safety factor (NO in step S201), the control unit 40 proceeds to step S301 shown in FIG. 6.

In step S202, the control unit 40 sets the emergency flag to ON. The control unit 40 also sets the normal flag to OFF. In this way, when the emergency flag is ON, the normal flag is OFF. The normal flag is a flag that indicates whether or not to execute the normal control flow. In other words, when the remaining charge lower limit value of the storage battery 32 is lowered from the initial value, the normal control flow of step S104 is not executed (see Figure 4). After performing the processing of step S202, the control unit 40 proceeds to step S203.

In step S203, the control unit 40 calculates the number of units for which emergency discharge is permitted. The number of units for which emergency discharge is permitted means the number of storage batteries 32 for which discharge needs to be initiated in order to prevent the demand value from exceeding the demand upper limit. In other words, the number of units for which emergency discharge is permitted means the number of storage batteries 32 for which the remaining charge lower limit needs to be changed (lowered) when there are storage batteries 32 for which the remaining charge amount has reached the remaining charge lower limit and discharge is not possible. The number of units for which emergency discharge is permitted is calculated using the following equation 2. The number of units for which emergency discharge is permitted is calculated by rounding up the decimal point of the value calculated using the following equation 2.
Number of units permitted to undergo emergency discharge=[{(expected demand value−emergency discharge instruction condition×safety factor)/2}/(remaining time−control lag)]/(discharge performance/60) (Equation 2)

Here, "expected demand value - emergency discharge instruction conditions x safety factor" means the extent to which the expected demand value exceeds the emergency discharge instruction conditions x safety factor, and by dividing this by 2, the one-hour integrated value is converted into a 30-minute integrated value. Note that "control lag" refers to the time lag between when an instruction is issued by the control unit 40 and when the storage battery 32 actually operates. Also, "discharge performance" refers to the maximum discharge power of the storage battery 32 (2 kW in this embodiment), and by dividing this by 60, the instantaneous value is converted into a one-minute integrated value. Note that the number of units permitted to discharge emergency is updated (decremented by 1) by the processing of step S209 described below, and the number of units permitted to discharge emergency calculated in step S203 is treated as the initial value for the number of units permitted to discharge emergency.

After performing the processing of step S203, the control unit 40 proceeds to step S204.

In step S204, the control unit 40 calculates the emergency discharge instruction priority. The emergency discharge instruction priority refers to the criteria for determining which of the three storage batteries 32 should have its remaining charge lower limit lowered first when it is necessary to lower the remaining charge lower limit of the storage batteries 32. The emergency discharge instruction priority is set by comparing the remaining charge levels of the three storage batteries 32 and giving the highest priority to the storage battery 32 with the highest remaining charge level.

Specifically, the battery 32 with the highest remaining charge among the three batteries 32 is calculated to have the highest priority for emergency discharge instruction. Furthermore, the battery 32 with the second highest remaining charge among the three batteries 32 is calculated to have the second highest priority for emergency discharge instruction. Furthermore, the battery 32 with the third highest remaining charge among the three batteries 32 is calculated to have the third highest priority for emergency discharge instruction.

After performing the process of step S204, the control unit 40 proceeds to step S205. When the control unit 40 proceeds from step S204 to step S205, it repeats the process from step S205 to step S211 the number of times (three times in this embodiment) for each storage battery 32, in accordance with the emergency discharge instruction priority calculated (set) in the process of step S204. That is, the control unit 40 focuses on the storage battery 32 ranked first, second, and third in the emergency discharge instruction priority order, in that order, and repeats the process from step S205 to step S211 for each storage battery 32 that has been focused on.

In step S205, the control unit 40 determines whether the number of units permitted to discharge emergency is greater than 0. Here, if this is the first time step S205 is executed after transitioning from step S204 to step S205, the initial value of the number of units permitted to discharge emergency calculated in step S203 is used as the number of units permitted to discharge emergency. Furthermore, if this is the second or subsequent time step S205 is executed, the updated value of the number of units permitted to discharge emergency calculated in step S211, which will be described later, is used.

If the control unit 40 determines that the number of units permitted to discharge emergency is greater than 0 ("YES" in step S205), it proceeds to step S206. On the other hand, if the control unit 40 determines that the number of units permitted to discharge emergency is not greater than 0 (i.e., is 0) ("NO" in step S205), it temporarily terminates the emergency discharge flow and proceeds to step S103 of the flow related to the power supply mode.

In step S206, the control unit 40 determines whether the remaining charge of the storage battery 32 (i.e., the storage battery 32 that was the target of steps S205 to S211 among the three storage batteries 32) is greater than the minimum remaining charge. If the control unit 40 determines that the remaining charge of the storage battery 32 is greater than the minimum remaining charge (YES in step S206), the control unit 40 proceeds to step S207. On the other hand, if the control unit 40 determines that the remaining charge of the storage battery 32 is not greater than the minimum remaining charge (i.e., is equal to or less than the minimum remaining charge) (NO in step S206), the control unit 40 performs the processes of steps S205 to S211 on the next storage battery 32 that is one rank lower than the storage battery 32. Note that if the storage battery 32 is the lowest-ranked storage battery 32, the control unit 40 temporarily terminates the emergency discharge flow and proceeds to step S103 of the flow related to the power supply mode.

In step S207, the control unit 40 determines whether the operating state of the storage battery 32 is in a discharging state (i.e., discharging). If the control unit 40 determines that the operating state of the storage battery 32 is not in a discharging state ("NO" in step S207), the control unit 40 proceeds to step S208. On the other hand, if the control unit 40 determines that the operating state of the storage battery 32 is in a discharging state ("YES" in step S207), the control unit 40 performs the processes from step S205 to step S211 on the next storage battery 32 that is one rank lower than the storage battery 32 in question. Note that if the storage battery 32 in question is the lowest-ranked storage battery 32, the control unit 40 temporarily terminates the emergency discharge flow and proceeds to step S103 of the flow related to the power supply mode.

In step S208, the control unit 40 determines whether the remaining charge of the storage battery 32 is greater than the remaining charge lower limit. If the control unit 40 determines that the remaining charge of the storage battery 32 is not greater than the remaining charge lower limit (i.e., is equal to or less than the remaining charge lower limit) ("NO" in step S208), the control unit 40 proceeds to step S209. On the other hand, if the control unit 40 determines that the remaining charge of the storage battery 32 is greater than the remaining charge lower limit ("YES" in step S208), the control unit 40 proceeds to step S210.

In step S209, the control unit 40 changes the current remaining lower limit to a new remaining lower limit (a remaining lower limit smaller than the current remaining lower limit). If this is the first processing of step S209 after moving from step S204 to step S205, the control unit 40 changes the initial value of the remaining lower limit (e.g., 50%), which is the current remaining lower limit, to a new remaining lower limit (e.g., 40%). The control unit 40 then issues a discharge instruction to the storage battery 32. Specifically, the control unit 40 switches the operating mode of the storage battery 32 to the discharge mode.

On the other hand, in step S210, the control unit 40 issues a discharge command to the storage battery 32. Specifically, the control unit 40 switches the operation mode of the storage battery 32 to a discharge mode.

After performing the processing of step S209 or step S210, the control unit 40 proceeds to step S211.

In step S211, the control unit 40 calculates an updated value of the number of units permitted to discharge emergency energy using the following equation 3.
Updated number of units permitted to discharge emergency electricity = current number of units permitted to discharge emergency electricity - 1 (Equation 3)

Here, "the current number of units permitted to discharge emergency" refers to the initial value of the number of units permitted to discharge emergency calculated in the processing of step S203 if this is the first processing of step S211 after transitioning from step S204 to step S205. Furthermore, if this is the second or subsequent processing of step S211, it refers to the updated value of the number of units permitted to discharge emergency calculated in the processing of the previous step S211.

After performing the process of step S211, the control unit 40 performs the processes from step S205 to step S211 on the storage battery 32 that is next in rank to the storage battery 32 in question. Note that if the storage battery 32 in question is the storage battery 32 with the lowest rank, the control unit 40 temporarily terminates the contract capacity excess prevention flow and proceeds to step S103 of the flow related to the power supply mode.

In this way, processing (steps S201 to S211) is executed to lower the remaining charge lower limit of the storage battery 32 and discharge the storage battery 32.

In other words, if the expected demand value for the demand time limit is equal to or greater than the emergency discharge instruction condition x safety factor ("YES" in step S201), it means that there is a high possibility that the demand value for the demand time limit will exceed the demand upper limit.

Therefore, in such a case, a discharge command is issued and the operating mode of the storage battery 32 is switched to discharge mode (step S210), thereby reducing the power received from the grid power source S into the distribution line 10 and preventing the demand value for that demand time limit from exceeding the demand upper limit. However, if the remaining charge of the storage battery 32 is below the remaining charge lower limit, the storage battery 32 cannot be discharged. Therefore, if the remaining charge of the storage battery 32 is below the remaining charge lower limit ("NO" in step S208), the current remaining charge lower limit is changed to a new remaining charge lower limit, and a discharge command is issued (step S209). This allows the storage battery 32, which was previously unable to discharge, to be discharged.

Figure 8 shows an example of the power supply state when the demand value exceedance suppression function is executed. Specifically, Figure 8 shows an example of the power supply state before the state shown in Figure 3 is reached, i.e., when the demand value is about to exceed the demand upper limit value (45 kW) and the remaining capacity lower limit value of all storage batteries 32 is lowered from the initial value (50%) to 40%.

As shown in Figure 8, when the remaining charge lower limit is lowered, the three power storage systems 30 can be discharged, which prevents the amount of power received from the grid power source S onto the distribution line 10 from increasing. In other words, the demand value for the demand time limit can be prevented from exceeding the demand upper limit (45 kW).

In the processing of step S203, the number of units permitted to discharge emergency electricity is calculated by rounding up the decimal point of the value calculated using Equation 2 above. This makes it possible to prevent a shortage of power, which is necessary to prevent the demand value from exceeding the upper demand limit. In this way, it is possible to effectively prevent the maximum demand value from increasing.

Furthermore, in processing such as step S204, the remaining charge lower limit is lowered in order, starting with the storage battery 32 with the most remaining charge. This prevents the storage battery 32 with the lower limit lowered from immediately running out of charge (the storage battery 32 immediately becoming unable to discharge) if, for example, the lower limit of the remaining charge of a storage battery 32 with a low remaining charge is lowered while the lower limit of the remaining charge of a storage battery 32 with a high remaining charge remains unchanged. In other words, it is possible to prevent the need to immediately lower the lower limit of the remaining charge of another storage battery 32 from occurring, and ultimately to efficiently prevent the maximum demand value from increasing.

Furthermore, in the processing of step S206, it is determined whether the remaining charge of the storage battery 32 is greater than the minimum remaining charge, and the lower limit value of the remaining charge is prevented from being lowered for storage batteries 32 whose remaining charge is less than the minimum remaining charge. This prevents the storage battery 32 from starting to discharge even though its remaining charge is less than the minimum remaining charge, resulting in forced charging (which would further increase the amount of power received from the system power source S into the distribution line 10).

Next, we will explain the process (steps S301 to S313) for raising (restoring) the lower remaining capacity limit value of the storage battery 32 that has been lowered.

In step S301, which follows step S201 (NO in step S201) as described above, the control unit 40 determines whether the emergency flag is ON. If the control unit 40 determines that the emergency flag is ON (YES in step S301), the control unit 40 proceeds to step S303. On the other hand, if the control unit 40 determines that the emergency flag is not ON (OFF) (NO in step S301), the control unit 40 proceeds to step S302.

In step S302, the control unit 40 sets the normal flag to ON. After performing the processing of step S302, the control unit 40 temporarily ends the emergency discharge flow and proceeds to step S103 of the flow related to the power supply mode.

In step S303, the control unit 40 calculates the number of units for which emergency discharge is to be released. Note that the number of units for which emergency discharge is to be released means the number of storage batteries 32 for which the lower limit value of remaining capacity is to be raised (raising the lower limit value is acceptable) when there are storage batteries 32 for which the lower limit value of remaining capacity has been lowered from the initial value. The number of units for which emergency discharge is to be released is calculated using the following equation 4. Note that the value calculated using the following equation 4 is rounded down to the nearest integer and used as the number of units for which emergency discharge is to be released.
Number of units for which emergency discharge is released=[{(emergency discharge release condition×safety factor−expected demand value)/2}/(remaining time−control lag)]/(discharge performance/60) (Equation 4)

Here, the emergency discharge release condition is a power value that is set lower than the emergency discharge instruction condition. For example, in this embodiment, the emergency discharge release condition is set to 35 kW, which is lower than the emergency discharge instruction condition (45 kW). Furthermore, "emergency discharge release condition x safety factor - expected demand value" means how much margin the expected demand value has relative to the emergency discharge release condition x safety factor, and by dividing this by 2, the 1-hour integrated value is converted to a 30-minute integrated value.

After performing the processing of step S303, the control unit 40 proceeds to step S304.

In step S304, the control unit 40 calculates the emergency discharge release order. The emergency discharge release order refers to the criteria for determining which of the three storage batteries 32 should be given priority when raising the lower limit of the remaining charge of the storage batteries 32. The emergency discharge release order is set by comparing the remaining charge levels of the three storage batteries 32 and ranking the storage battery 32 with the lowest remaining charge level first.

Specifically, the battery 32 with the lowest remaining charge among the three storage batteries 32 is calculated to be first in the order for emergency discharge cancellation. Furthermore, the battery 32 with the second lowest remaining charge among the three storage batteries 32 is calculated to be second in the order for emergency discharge cancellation. Furthermore, the battery 32 with the third lowest remaining charge among the three storage batteries 32 is calculated to be third in the order for emergency discharge cancellation.

After performing the process of step S304, the control unit 40 proceeds to step S305. When the control unit 40 proceeds from step S304 to step S305, it repeats the process from step S305 to step S309 the number of times (three times in this embodiment) for the number of storage batteries 32, in accordance with the emergency discharge release priority calculated (set) in the process of step S304. That is, the control unit 40 focuses on the storage battery 32 ranked first, second, and third in the emergency discharge release priority order, in that order, and repeats the process from step S305 to step S309 for each storage battery 32 that has been focused on.

In step S305, the control unit 40 determines whether the operating state of the storage battery 32 is in a discharging state (i.e., discharging). If the control unit 40 determines that the operating state of the storage battery 32 is not in a discharging state ("NO" in step S305), the control unit 40 proceeds to step S309. On the other hand, if the control unit 40 determines that the operating state of the storage battery 32 is in a discharging state ("YES" in step S305), the control unit 40 proceeds to step S306.

In step S306, the control unit 40 determines whether the number of emergency discharge release units is greater than 0. Here, as the number of emergency discharge release units in step S306, if the processing of step S308 has not yet been executed after transition from step S304 to step S305, the initial value of the number of emergency discharge release units calculated in the processing of step S303 is used. Also, if the processing of step S308 has already been executed after transition from step S304 to step S305, the updated value of the number of emergency discharge release units calculated in the processing of step S308 is used. If the control unit 40 determines that the number of emergency discharge release units is greater than 0 (YES in step S306), it proceeds to step S308. On the other hand, if the control unit 40 determines that the number of emergency discharge release units is not greater than 0 (i.e., is 0) (NO in step S306), it proceeds to step S307.

In step S307, the control unit 40 sets the continuation flag to ON. The continuation flag is a flag that serves as the criterion for determining whether to set the emergency flag to OFF after performing the processes from step S305 to step S309. After performing the process of step S307, the control unit 40 performs the processes from step S305 to step S309 on the storage battery 32 that is one rank lower than the storage battery 32 in question. If the storage battery 32 in question is the lowest-ranked storage battery 32, the control unit 40 proceeds to step S310.

In step S308, the control unit 40 calculates an updated value of the number of units for which emergency discharge has been cancelled, using the following Equation 5.
Updated number of units for which emergency discharge has been released = current number of units for which emergency discharge has been released - 1 (Equation 5)

Here, "the current number of units for which emergency discharge has been released" refers to the initial value of the number of units for which emergency discharge has been released calculated in the processing of step S303 if this is the first processing of step S308 after transitioning from step S304 to step S305. Furthermore, if this is the second or subsequent processing of step S308, it refers to the updated value of the number of units for which emergency discharge has been released calculated in the processing of the previous step S308.

After performing the processing of step S308, the control unit 40 proceeds to step S309.

In step S309, the control unit 40 changes the current remaining charge lower limit value to the initial value. Then, the control unit 40 issues a standby instruction to the storage battery 32. Specifically, the control unit 40 switches the operating mode of the storage battery 32 to standby mode. After performing the process of step S309, the control unit 40 performs the processes of steps S305 to S309 on the storage battery 32 that is next ranked lower than the storage battery 32 in question. Note that if the storage battery 32 in question is the lowest-ranked storage battery 32, the control unit 40 proceeds to step S310.

In step S310, the control unit 40 determines whether the continuation flag is OFF. If the control unit 40 determines that the continuation flag is OFF ("YES" in step S310), the control unit 40 proceeds to step S312. On the other hand, if the control unit 40 determines that the continuation flag is not OFF (is ON) ("NO" in step S310), the control unit 40 proceeds to step S311.

In step S311, the control unit 40 sets the continuation flag to OFF. After performing the processing of step S311, the control unit 40 temporarily ends the emergency discharge flow and proceeds to step S103 of the flow related to the power supply mode.

In step S312, the control unit 40 sets the emergency flag to OFF. After performing the processing of step S312, the control unit 40 temporarily ends the emergency discharge flow and proceeds to step S103 of the flow related to the power supply mode.

In this way, processing (steps S301 to S312) is executed to raise (restore) the lower remaining capacity limit of the storage battery 32 and stop discharge from the storage battery 32.

In other words, when there is almost no possibility that the demand value will exceed the demand upper limit value ("NO" in step S201), rather than continuing to discharge the storage battery 32 with the remaining charge lower limit value lowered from the initial value, the storage battery 32's remaining charge lower limit value is returned to the initial value and discharge is stopped ("YES" in step S305, see step S309, etc.). In this way, when there is almost no possibility that the demand value will exceed the demand upper limit value, it is possible to prevent unnecessary use of the power of the storage battery 32 that can be used in emergencies such as power outages.

In addition, before step S303, a step may be provided to determine whether the expected demand value is smaller than the emergency discharge cancellation condition (set smaller than the emergency discharge instruction condition (see step S201)), and if the expected demand value is smaller than the emergency discharge cancellation condition, the process may proceed to step S303. This makes it possible to prevent the lower limit value of the remaining capacity of the storage battery 32 from being frequently and alternately lowered and raised.

In addition, in the processing of step S303, the number of units for which emergency discharge is to be released is calculated using equation 4 above, with the decimal point rounded down. This makes it possible to prevent the demand value from exceeding the limit due to stopping discharge from the storage battery 32. In this way, it is possible to effectively prevent the maximum demand value from increasing.

Furthermore, in processing such as step S304, the remaining charge lower limit is raised in order, starting with the storage battery 32 with the least remaining charge. This prevents the storage battery 32 with the remaining charge lower limit left unchanged, for example, while raising the remaining charge lower limit of a storage battery 32 with a large remaining charge, resulting in an immediate shortage of remaining charge (the storage battery 32 becoming unable to discharge immediately). In other words, it is possible to prevent the need to immediately lower the remaining charge lower limit of another storage battery 32 from occurring, and ultimately to prevent the remaining charge lower limit of a storage battery 32 from being frequently and alternately lowered and raised.

The priority charging flow is explained in detail below using the flowchart in Figure 7.

The priority charging flow is a flow in which, after an emergency discharge instruction is released, a charging instruction is issued to the storage battery 32 when it is deemed that charging the storage battery 32 will not result in exceeding the demand value, in preparation for a subsequent emergency discharge instruction (and in an emergency).

In step S401, the control unit 40 determines whether the expected demand value is smaller than the emergency discharge cancellation condition. Here, the emergency discharge cancellation condition is, as described above, a power value set smaller than the emergency discharge instruction condition (e.g., 45 kW), and is set to, for example, 35 kW.

If the control unit 40 determines that the expected demand value is not smaller than the emergency discharge cancellation condition (i.e., is equal to or greater than the emergency discharge cancellation condition) ("YES" in step S401), the control unit 40 proceeds to step S408. On the other hand, if the control unit 40 determines that the expected demand value is smaller than the emergency discharge cancellation condition ("NO" in step S401), the control unit 40 proceeds to step S402.

In step S402, the control unit 40 calculates the number of vehicles for which priority charging is permitted. The number of vehicles for which priority charging is permitted means the number of storage batteries 32 for which charging needs to be started in order to ensure the remaining charge of the storage batteries 32. The number of vehicles for which priority charging is permitted is calculated using the following equation 6. The number of vehicles for which priority charging is permitted is calculated by rounding down the decimal point of the value calculated using the following equation 6.
Number of vehicles permitted to charge with priority=[{(emergency discharge release condition×safety factor−expected demand value)/2}/(remaining time−control lag)]/(charging performance/60) (Equation 6)

Here, "emergency discharge release condition x safety factor - expected demand value" means a predicted value of how much margin the expected demand value has relative to the emergency discharge release condition x safety factor, and by dividing this by 2, the 1-hour integrated value is converted into a 30-minute integrated value. Furthermore, "charging performance" means the maximum charging power of the storage battery 32 (2 kW in this embodiment), and by dividing this by 60, the instantaneous value is converted into a 1-minute integrated value.

After performing the processing of step S402, the control unit 40 proceeds to step S403.

In step S403, the control unit 40 calculates a priority charging instruction order. The priority charging instruction order refers to the criteria for determining which of the three storage batteries 32 should be given priority charging when priority charging of the storage batteries 32 is required. The priority charging instruction order is set by comparing the remaining charge levels of the three storage batteries 32 and giving the battery 32 with the lowest remaining charge the highest priority.

Specifically, the battery 32 with the lowest remaining charge among the three batteries 32 is calculated to have the highest priority for charging instructions. Furthermore, the battery 32 with the second lowest remaining charge among the three batteries 32 is calculated to have the second highest priority for charging instructions. Furthermore, the battery 32 with the third lowest remaining charge among the three batteries 32 is calculated to have the third highest priority for charging instructions.

After performing the process of step S403, the control unit 40 proceeds to step S404. When the control unit 40 proceeds from step S403 to step S404, it repeats the processes of steps S404 to S409 the number of times (three times in this embodiment) for the number of storage batteries 32, in accordance with the priority charging instruction order calculated (set) in the process of step S403. That is, the control unit 40 focuses on the storage battery 32 with the first priority charging instruction order, the second priority charging instruction order, and the third priority charging instruction order in that order, and repeats the processes of steps S404 to S409 for the storage battery 32 that has been focused on.

In step S404, the control unit 40 determines whether the remaining charge of the storage battery 32 (i.e., the storage battery 32 that was the subject of the processing from step S404 to step S408 among the three storage batteries 32) is less than the (initial value of) the lower limit value. If the control unit 40 determines that the remaining charge of the storage battery 32 is less than the lower limit value ("YES" in step S404), it proceeds to step S405. On the other hand, if the control unit 40 determines that the remaining charge of the storage battery 32 is not less than the lower limit value (i.e., is equal to or greater than the lower limit value) ("NO" in step S404), it proceeds to step S408. Note that if the remaining charge of the storage battery 32 is equal to or greater than the lower limit value, it is considered that the remaining charge of the storage battery 32 that is lower in rank than the storage battery 32 is also equal to or greater than the lower limit value. Therefore, there is no need to repeat steps S404 to S409 for storage batteries 32 with a lower priority than the storage battery 32 in question.

In step S405, the control unit 40 determines whether the operating state of the storage battery 32 is other than the charging state (i.e., discharging or standby). If the control unit 40 determines that the operating state of the storage battery 32 is other than the charging state (YES in step S405), the control unit 40 proceeds to step S406. On the other hand, if the control unit 40 determines that the operating state of the storage battery 32 is other than the charging state (NO in step S405), the control unit 40 performs the processes from step S404 to step S409 on the next storage battery 32 that is one rank lower than the storage battery 32. Note that if the storage battery 32 is the lowest-ranked storage battery 32, the control unit 40 temporarily terminates the priority charging flow and also temporarily terminates the flow related to the power supply mode.

In step S406, the control unit 40 determines whether the number of vehicles permitted to charge with priority is greater than 0. If the control unit 40 determines that the number of vehicles permitted to charge with priority is greater than 0 ("YES" in step S406), the control unit 40 proceeds to step S407. On the other hand, if the control unit 40 determines that the number of vehicles permitted to charge with priority is not greater than 0 (i.e., it is 0) ("NO" in step S406), the control unit 40 proceeds to step S408.

In step S407, the control unit 40 issues a charge instruction to the storage battery 32. Specifically, the control unit 40 switches the operating mode of the storage battery 32 to the charge mode. The storage battery 32 is charged until the remaining charge reaches the lower limit (50% of the maximum capacity). Note that the remaining charge after charging is not limited to this and can be any value; for example, it may be charged to 100% of the maximum capacity.

After performing the processing of step S407, the control unit 40 proceeds to step S409.

In step S409, the control unit 40 calculates an updated value of the number of vehicles for which priority charging is permitted. The updated value of the number of vehicles for which priority charging is permitted is calculated using the following Equation 7.
Updated number of priority charging permitted units = current number of emergency discharging permitted units - 1 (Equation 7)

After performing the process of step S409, the control unit 40 performs the processes of steps S404 to S409 on the storage battery 32 that is next in rank to the storage battery 32 in question. If the storage battery 32 in question is the storage battery 32 with the lowest rank, the control unit 40 temporarily terminates the priority charging flow and also temporarily terminates the flow related to the power supply mode.

On the other hand, in step S408, the control unit 40 issues a standby instruction to the storage battery 32. The control unit 40 switches the operation mode of the storage battery 32 to standby mode.

After performing the processing of step S408, the control unit 40 temporarily ends the priority charging flow and also temporarily ends the flow related to the power supply mode.

In this way, after the emergency discharge instruction is released, if it is deemed that charging the storage battery 32 will not result in exceeding the demand value, a charge instruction is issued to the storage battery 32. This ensures that the remaining charge in the storage battery 32 is secured in preparation for future emergency discharge instructions and emergencies such as power outages.

As described above, the power supply system 1 according to this embodiment has the following features:
A power supply system that supplies power to a group of loads H connected to a power system S,
a storage battery 32 connected between the power system S and the load group H and capable of charging and discharging power from a predetermined supply source (the power system S and the solar power generation unit 31);
a control unit 40 for controlling charging and discharging of the storage battery 32;
Equipped with
The storage battery 32 is
A remaining charge lower limit value is set, which indicates the lower limit value of the power that can be discharged normally from the remaining charge amount,
The control unit 40
During each demand time period, if it is predicted that the demand value (anticipated demand value) of the demand time period will exceed the first reference value (emergency discharge instruction condition × safety factor) ("YES" in step S201 of FIG. 5), an emergency discharge instruction is issued to enable discharge from the storage battery 32 (steps S209 and S210 of FIG. 5),
If there is a storage battery 32 whose remaining charge is less than the lower limit value ("NO" in step S208 of Figure 5), the lower limit value of the remaining charge of that storage battery 32 can be lowered (step S209 of Figure 5) before issuing the emergency discharge instruction.

With this configuration, it is possible to reduce the maximum demand value and thereby reduce the electricity bill.
Specifically, during each demand time period, the demand value for that demand time period is predicted, i.e., in real time (every minute), and if this predicted value (expected demand value) is likely to exceed the demand upper limit value, a discharge command is issued to the storage battery 32, thereby enabling the maximum demand value to be accurately suppressed.
However, even if a discharge command is issued to the storage battery 32, if the remaining charge of the storage battery 32 is equal to or less than the remaining charge lower limit, the storage battery 32 cannot be discharged. Therefore, if the remaining charge of the storage battery 32 is equal to or less than the remaining charge lower limit, the current remaining charge lower limit is changed to a new remaining charge lower limit before issuing a discharge command. This makes it possible for the storage battery 32 that was previously unable to be discharged to be discharged.
Furthermore, since the demand value for the demand time limit is predicted without using external information such as weather information or past power data, it is possible to reduce running costs associated with maintaining and purchasing such data.

In addition, in the power supply system 1,
The control unit 40
The amount of power used from the power system S can be acquired,
Based on the actual value of the amount of electricity used up to the present time during the demand time limit and the predicted value of the amount of electricity used for the remaining time during the demand time limit, it is determined whether the demand value for the demand time limit exceeds the first reference value (step S201 in Figure 5).

This configuration allows for accurate prediction of demand values.

In addition, in the power supply system 1,
The control unit 40
The predicted value of the amount of power usage for the remaining time is calculated based on the amount of power usage for the most recent predetermined period (for example, three minutes).

This configuration allows for more accurate prediction of demand values.

In addition, in the power supply system 1,
A plurality of the storage batteries 32 are provided,
The control unit 40
The emergency discharge instruction is issued to the storage batteries 32 in order of the remaining charge amount, starting from the storage battery 32 with the most remaining charge amount (step S204 in FIG. 3).

With this configuration, the maximum demand value can be reduced efficiently.
Specifically, for example, discharging a storage battery 32 that has a lower remaining charge than the others can prevent the remaining charge available for discharge from quickly running out (the storage battery 32 quickly becoming unable to discharge).

In addition, in the power supply system 1,
The control unit 40
After the emergency discharge instruction is given, if it is predicted that the demand value for the demand time limit will not exceed the first reference value or a second reference value (emergency discharge release condition x safety factor) that is smaller than the first reference value, the emergency discharge instruction can be released (step S309 in Figure 6).

This configuration helps prevent unnecessary use of power reserved for emergencies such as power outages.

In addition, in the power supply system 1,
The control unit 40
When the emergency discharge instruction is cancelled, the lower limit value of the remaining capacity (for example, 40% of the maximum capacity) can be raised to the original lower limit value of the remaining capacity (for example, 50% of the maximum capacity) (step S309 in FIG. 6).

This configuration further reduces the unnecessary use of power reserved for emergencies such as power outages.

In addition, in the power supply system 1,
The control unit 40
After the emergency discharge instruction is released, if there is a storage battery 32 whose remaining charge is less than the increased remaining charge lower limit (YES in step S404 in Figure 7), a priority charging instruction is issued to enable charging of that storage battery 32 (step S407 in Figure 7).

This configuration allows power to be stored in the storage battery 32 for emergencies such as power outages.

In addition, in the power supply system 1,
A plurality of the storage batteries 32 are provided,
The control unit 40
When there are a plurality of storage batteries 32 whose remaining charge amounts are less than the increased remaining charge lower limit, the priority charging instruction is given to the storage batteries 32 in order, starting with the storage battery 32 with the least remaining charge amount.

With this configuration, the storage battery 32 can be charged efficiently.
Specifically, for example, charging the storage battery 32 with a larger remaining charge amount than the others can be started first, which can prevent imbalances in the remaining charge amount from occurring.

The above describes an embodiment of the present invention, but the present invention is not limited to the above configuration, and various modifications are possible within the scope of the invention described in the claims.

For example, in this embodiment, the power supply system 1 is installed in an office T, but it may also be installed in any location or building, such as a factory, apartment building, home, or hospital.

In addition, in this embodiment, three power storage systems 30 are provided, but this is not limited to this and the number may be, for example, two or one. In addition, in this embodiment, the power storage systems 30 are arranged in series on the power distribution line 10, but they may also be arranged in parallel, as shown in FIG. 9.

Furthermore, while the power storage system 30 is configured to include a solar power generation unit 31, it does not have to include a solar power generation unit 31. Furthermore, in addition to (or instead of) the solar power generation unit 31, it may also include other power supply sources (for example, fuel cells, or hydroelectric power generation units or wind power generation units that generate electricity using natural energy other than sunlight).

In addition, in this embodiment, the control unit 40 is configured to be provided outside the power storage system 30, but it may also be configured to be provided inside the power storage system 30, such as being incorporated into the storage battery 32, and the configuration is not limited thereto.

Furthermore, in this embodiment, the emergency discharge instruction condition is set to 45 kW, but is not limited to this. Further, in this embodiment, the emergency discharge release condition is set to 35 kW, but is not limited to this. However, the emergency discharge release condition needs to be set to a value lower than the emergency discharge instruction condition.

In addition, in this embodiment, the lower limit of the remaining charge of the storage battery 32 can be reduced in increments of 10% of the storage capacity (maximum capacity), but the reduction amount can be any value. Furthermore, when increasing the lower limit of the remaining charge of the storage battery 32, the lower limit can be increased in stages (rather than immediately returning it to the initial value).

In addition, in this embodiment, the minimum remaining amount is set to 5% of the storage capacity (maximum capacity), but this is not limited to this. However, the minimum remaining amount must be set to be smaller than the initial value of the remaining amount lower limit.

REFERENCE SIGNS LIST 1 Power supply system 31 Photovoltaic power generation unit 32 Storage battery 40 Control unit S System power supply H Load group

Claims (6)

A power supply system that supplies power to a load connected to a system power supply,
a storage battery connected between a system power supply and the load and capable of charging and discharging power from a predetermined supply source;
a control unit that controls charging and discharging of the storage battery;
Equipped with
The storage battery is
A remaining charge lower limit value is set, which indicates the lower limit value of the power that can be discharged normally from the remaining charge amount,
The control unit
During each demand time limit, when it is predicted that the demand value of the demand time limit will exceed a first reference value, an emergency discharge permission number is calculated, which is the number of the storage batteries that need to start discharging in order to prevent the demand value from exceeding the first reference value, and an emergency discharge instruction is given to discharge from the storage batteries determined based on the emergency discharge permission number;
If there is a battery among the determined storage batteries with a remaining charge amount equal to or less than the remaining charge lower limit value, the remaining charge lower limit value of the battery is lowered before issuing the emergency discharge instruction;
When the emergency discharge instruction is cancelled, the lower limit value of the remaining capacity is raised to the original lower limit value of the remaining capacity.
After canceling the emergency discharge instruction, if it is predicted that the demand value of each demand time limit will not exceed a second reference value that is smaller than the first reference value, calculate a number of storage batteries permitted for priority charging, which is the number of storage batteries whose demand value will not exceed the second reference value even when charged, determine the storage batteries to be charged based on the number of storage batteries permitted for priority charging, and if there is a storage battery among the determined storage batteries whose remaining charge amount is less than the original remaining charge lower limit value, issue a priority charge instruction to charge the storage battery until its remaining charge amount reaches the original remaining charge lower limit value.
Power supply system. The control unit
The amount of power used from the power grid can be acquired,
determining whether or not the demand value for the demand time limit exceeds the first reference value based on the actual value of the amount of power used up to the present time during the demand time limit and the predicted value of the amount of power used for the remaining time during the demand time limit;
The power supply system according to claim 1 . The control unit
calculating a predicted value of the amount of power usage for the remaining time based on the amount of power usage for a most recent predetermined period;
The power supply system according to claim 2 . A plurality of the storage batteries are provided,
The control unit
the emergency discharge instruction is issued to the storage batteries in order of the remaining charge amount, starting from the storage battery with the largest remaining charge amount;
The power supply system according to any one of claims 1 to 3. The control unit
After issuing the emergency discharge instruction, if it is predicted that the demand value of the demand time limit will not exceed the first reference value or the second reference value, calculate an emergency discharge release number, which is the number of storage batteries whose demand value does not exceed the second reference value even if the remaining lower limit value is raised among the storage batteries whose remaining lower limit value has been lowered, and release the emergency discharge instruction for the storage batteries determined based on the emergency discharge release number .
The power supply system according to any one of claims 1 to 4. A plurality of the storage batteries are provided,
The control unit
When there are a plurality of storage batteries whose remaining charge amounts are less than the increased remaining charge lower limit, the priority charging instruction is given to the storage batteries in order starting from the storage battery with the least remaining charge amount.
The power supply system according to any one of claims 1 to 5.