Energy storage system, power supply system, and control method

Abstract

To provide an energy storage system capable of preventing the inability to discharge during a power outage while avoiding electricity generated by a solar power generation system from going to waste, a power supply system, and a control method.SOLUTION: The energy storage system includes a storage battery, and a control unit that controls the discharge of the storage battery. The control unit is configured so as to, when the power supply is cut off from the grid, execute a first mode to discharge the storage battery to output power equal to or below a first upper limit value or a second mode to discharge the storage battery to output power equal to or below a second upper limit value which is lower than the first upper limit value, and switch between the first mode and the second mode depending on a predetermined condition.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a power storage system, a power supply system, and a control method.

Background Art

[0002] There are known a hybrid power storage system having a power conversion device that converts DC power generated by a solar panel (hereinafter referred to as a PV (Photovoltaic) panel) into AC power, and a single-function power storage system that does not have such a power conversion device. The single-function power storage system includes an all-load type power storage system and a specific-load type power storage system. The all-load type power storage system supplies single-phase three-wire 200 V and 100 V to all loads (i.e., electrical equipment) that can be supplied with power from the system at the location where the power storage system is installed when a power outage occurs in the commercial power system (hereinafter simply referred to as the "system") (see Patent Document 1 below). The specific-load type power storage system supplies single-phase two-wire 100 V to a specific load when a power outage occurs in the system (see Patent Document 2 and Patent Document 3 below).

[0003] Referring to Figure 1, the full-load type energy storage system 900 typically does not have auxiliary input terminals and is connected to the photovoltaic power generation system 920. The energy storage system 900 includes a battery 902, a DC / DC converter 904, a DC / AC converter 906, and a relay 908. The photovoltaic power generation system 920 includes PV panels 922 and a PCS (Power Conditioning System) 924. The DC / DC converter 904 boosts the DC voltage output from the battery 902 and outputs it to the DC / AC converter 906. The DC / AC converter 906 converts the input DC voltage into AC voltage and supplies power to loads 932 such as household appliances located indoors. When the relay 908 is turned on (i.e., short-circuited), the DC / AC converter 906 and the loads 932 are connected to the grid 930. Power supplied from the grid 930 is supplied to the loads 932. The DC / AC converter 906 and the DC / DC converter 904 are bidirectional power converters that convert AC power supplied from grid 930 into DC power to charge the battery 902.

[0004] The PV panel 922 generates electricity from sunlight and outputs DC power. The PCS 924 converts the DC power output from the PV panel 922 into AC power and supplies it to the load 932. The solar power generation system 920 is grid-connectable, and if power is supplied from grid 930, it connects to grid 930 and supplies the generated power to the load 932. If grid 930 is experiencing a power outage, the energy storage system 900 discharges the battery 902 to generate single-phase three-wire 200V and 100V, creating a pseudo-grid. Therefore, even when grid 930 is experiencing a power outage, the PCS 924 can connect to the pseudo-grid (i.e., the energy storage system 900) and output power, just as it would when grid 930 is operational.

[0005] Referring to Figure 2, the specific load type energy storage system 950 has an auxiliary input terminal 956 and is connected to the photovoltaic system 960 via the auxiliary input terminal 956. That is, the energy storage system 950 includes relays 952, 954, and the auxiliary input terminal 956 in addition to the configuration of the energy storage system 900. The photovoltaic system 960 includes PV panels 922 and a PCS 962. The general load 970 is supplied with power from the grid 930. When power is supplied from the grid 930, the specific load 972 is supplied with power from the grid 930 by turning on relays 908 and 952. If the grid 930 fails, the PCS 962 outputs the power generated by the PV panels 922 from its standalone output terminal 964 (for example, outputting single-phase two-wire 100V), and the specific load 972 is supplied with power from the photovoltaic system 960 via the auxiliary input terminal 956 by turning on relays 952 and 954. Furthermore, the power output from the standalone output terminal 964 is also supplied to the battery 902 by the DC / AC converter 906 and the DC / DC converter 904, and the battery 902 is charged by the surplus power from the solar power generation system 960. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-110755 [Patent Document 2] Japanese Patent Publication No. 2008-253033 [Patent Document 3] Japanese Patent Publication No. 2015-61429 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the full-load type energy storage system 900, during a power outage in the grid 930, when solar radiation conditions are poor (e.g., cloudy), resulting in low power generation from the photovoltaic power generation system 920 and high power consumption from the load 932, the insufficient power is supplied by discharging the battery 902. If this condition persists, the battery level of the battery 902 decreases and eventually reaches the lower limit of its output range. When the battery level of the battery 902 reaches the lower limit, the energy storage system 900 is unable to output AC power and ceases to function as a pseudo-grid. Subsequently, even when solar radiation conditions allow the PV panels 922 to generate sufficient power, the photovoltaic power generation system 920 remains unable to connect to the grid because there is no pseudo-grid. Even if the photovoltaic power generation system 920 has an independent output terminal and can output power from it, the energy storage system 900 cannot charge the battery 902 because it does not receive power from the photovoltaic power generation system 920. Therefore, in order for the energy storage system 900 to operate again (i.e., discharge), it has no choice but to wait for the power outage on grid 930 to be resolved and for power to be supplied from grid 930. As a result, the electricity generated by the solar power generation system 920 is wasted.

[0008] Therefore, the purpose of this disclosure is to provide an energy storage system, a power supply system, and a control method that can avoid the inability to discharge during grid power outages and suppress the waste of power generated by a solar power generation system. [Means for solving the problem]

[0009] A power storage system relating to a certain aspect of this disclosure includes a battery and a control unit that controls the discharge of the battery, wherein the control unit, upon receiving a loss of power supply from the grid, executes a first mode in which it discharges the battery to output power below a first upper limit, or a second mode in which it discharges the battery to output power below a second upper limit that is smaller than the first upper limit, and switches between the first mode and the second mode according to predetermined conditions. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide an energy storage system, a power supply system, and a control method that can avoid the inability to discharge during grid power outages and suppress the waste of electricity generated by a solar power generation system. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing the configuration of a full-load type energy storage system. [Figure 2] Figure 2 is a block diagram showing the configuration of a specific load type energy storage system. [Figure 3] Figure 3 is a block diagram showing the configuration of an energy storage system according to an embodiment. [Figure 4] Figure 4 is a flowchart showing the operation of the control unit shown in Figure 3. [Figure 5] Figure 5 is a schematic diagram showing an example of the screen displayed on the remote control when switching to low power consumption mode. [Figure 6] Figure 6 is a schematic diagram showing an example of the screen displayed on the remote control when returning to normal mode. [Figure 7] Figure 7 is a flowchart showing the operation of the remote control shown in Figure 3. [Figure 8] Figure 8 is a flowchart showing the operation of the control unit of the modified energy storage system. [Figure 9] Figure 9 is a graph showing the relationship between the remaining battery charge of the storage battery and the remaining battery charge for the display. [Modes for carrying out the invention]

[0012] [Description of Embodiments in this Disclosure] The embodiments of this disclosure are listed and described below. At least some of the embodiments described below may be combined in any way.

[0013] (1) The power storage system according to the first aspect of the present disclosure includes a storage battery and a control unit that controls the discharge of the storage battery. The control unit, upon receiving that power supply from the grid has stopped, executes a first mode in which the storage battery is discharged so as to output power not exceeding a first upper limit value, or a second mode in which the storage battery is discharged so as to output power not exceeding a second upper limit value smaller than the first upper limit value, and switches between the first mode and the second mode according to a predetermined condition. This can avoid the situation where power cannot be discharged from the power storage system during a power outage of the grid and suppress the waste of generated power by the solar power generation system.

[0014] (2) In the above (1), the predetermined condition can include a condition related to the remaining battery level of the storage battery. The control unit can switch from the first mode to the second mode upon receiving that the remaining battery level has become not more than a first threshold value during the execution of the first mode. This can further avoid the situation where power cannot be discharged from the power storage system during a power outage of the grid.

[0015] (3) In the above (2), the control unit may charge the storage battery with surplus power supplied from the solar power generation system. During the execution of the second mode, upon receiving that the remaining battery level has become not less than a second threshold value greater than the first threshold value due to charging with surplus power, the control unit may switch from the second mode to the first mode. This can avoid the situation where the remaining battery level of the storage battery immediately decreases and shifts to the second mode after the solar power generation system starts generating power and the storage battery is charged with surplus power and returns to the first mode.

[0016] (4) In the above (2) or (3), the power storage system may further include a remote controller. The remote controller receives an input of a lower limit remaining battery level for the storage battery, which is a lower limit value of the remaining battery level of the storage battery for restricting discharge in a state where power is supplied from the grid, and may set the input value as the lower limit remaining battery level for discharge upon receiving that a value greater than the first threshold value has been input. This can extend the period during which the second mode can be maintained during a power outage of the grid.

[0017] (5) In the above (4), when switching from the first mode to the second mode, the remote controller may be caused to present a message prompting reduction of power consumption. Thereby, it can be expected that the user stops a device with high power consumption, and the period during which the second mode can be maintained during a power outage in the system can be made longer.

[0018] (6) In the above (4) or (5), the control unit may cause the remote controller to display a numerical value corresponding to the remaining battery level of the storage battery, and during execution of the second mode, the numerical value may be made smaller than the remaining battery level. Thereby, in the second mode, it is possible to prevent dissatisfaction of the user with respect to the imbalance between the power supplied from the power storage system and the remaining battery level that may occur when the remaining battery level of the storage battery is displayed as it is.

[0019] (7) The power supply system according to the second aspect of the present disclosure includes the power storage system according to any one of the above (1) to (6) and a solar power generation system, and the control unit charges the storage battery with surplus power of the solar power generation system. Thereby, it is possible to avoid the situation where the power storage system cannot discharge during a power outage in the system, and it is possible to suppress the waste of the generated power by the solar power generation system.

[0020] (8) The control method according to the third aspect of the present disclosure is a control method for a power storage system having a storage battery, and includes a control step of controlling the discharge of the storage battery. The control step includes a first mode in which the storage battery is discharged so as to output power not exceeding a first upper limit value, or a second mode in which the storage battery is discharged so as to output power not exceeding a second upper limit value smaller than the first upper limit value, in response to the power supply from the system being stopped, and a step of switching between the first mode and the second mode according to a predetermined condition. Thereby, it is possible to avoid the situation where the power storage system cannot discharge during a power outage in the system, and it is possible to suppress the waste of the generated power by the solar power generation system.

[0021] [Details of Embodiments of the Present Disclosure] In the following embodiments, identical parts are assigned the same reference numeral. Their names and functions are also identical. Therefore, detailed descriptions of them will not be repeated.

[0022] (System Configuration) Referring to Figure 3, a power supply system according to an embodiment of the present disclosure includes a battery storage system 100, a solar power generation system 120, and a remote control 134. The power supply system is installed, for example, in a house. The battery storage system 100 includes a battery 102, a DC / DC converter 104, a DC / AC converter 106, a relay 108, and a control unit 110.

[0023] The battery 102 is a rechargeable battery such as a lithium-ion secondary battery. The battery 102 functions as a DC power source. The DC / DC converter 104, under the control of the control unit 110, boosts the DC voltage output from the battery 102 and outputs it to the DC / AC converter 106. The DC / AC converter 106, under the control of the control unit 110, converts the DC voltage from the DC / DC converter 104 into an AC voltage and supplies power to loads 132 such as household appliances located indoors.

[0024] When relay 108 is turned on (i.e., short-circuited) under the control of control unit 110, the DC / AC converter 106 and load 132 are connected to grid 130. Power supplied from grid 130 is supplied to load 132. The energy storage system 100 and the solar power generation system 120 are interconnected with grid 130 and supply power to load 132. DC / AC converter 106 and DC / DC converter 104 are bidirectional power converters that convert AC power supplied from grid 130 to DC power and charge the battery 102.

[0025] The PV panel 122 consists of multiple solar cells connected in series, arranged on a plane and sealed with reinforced glass or the like. The PV panel 122 functions as a DC power source. The PCS 124 converts the DC power output from the PV panel 122 into AC power and supplies it to the load 132. As described above, the photovoltaic power generation system 120 is grid-connectable, and if power is supplied from the grid 130, it connects to the grid 130 and supplies the generated power to the load 132.

[0026] The control unit 110 includes, for example, a CPU (Central Processing Unit) and memory. The functions of the control unit 110 are realized by the CPU executing a program stored in memory. The control unit 110 controls the DC / DC converter 104, the DC / AC converter 106, and the relay 108. The control unit 110 controls the power conversion functions of the DC / DC converter 104 and the DC / AC converter 106, i.e., the input and output voltages and currents, by outputting control signals (e.g., gate signals) for the switching elements (e.g., FETs) that constitute each of them.

[0027] The control unit 110 monitors the power supply status from the grid 130 to the relay 108 using a current sensor (not shown) or the like, and detects when a power outage occurs in the grid 130. When a power outage occurs in the grid 130 and power is no longer supplied from the grid 130, the control unit 110 turns off (i.e., opens) the relay 108. As a result, the energy storage system 100, the solar power generation system 120, and the load 132 are disconnected from the grid 130. The control unit 110 obtains the State of Charge (SOC) of the battery 102 from the battery 102 and, depending on the SOC, switches between two modes as described later. In each mode, the control unit 110 controls the DC / DC converter 104 and the DC / AC converter 106 to supply the discharge power of the battery 102 to the load 132. During a power outage in grid 130, the control unit 110 acts as a pseudo-grid, allowing the solar power generation system 120 to supply the grid-connected output from the energy storage system 100, which acts as the pseudo-grid, to the load 132.

[0028] The remote control 134 is located indoors and includes a display device and an operating device (neither of which are shown). The remote control 134 includes a CPU and memory. The functions of the remote control 134 are realized by the CPU executing a program stored in memory. The remote control 134 is connected to the control unit 110 and displays messages, etc., in response to instructions from the control unit 110. The display device and operating device may be, for example, an integrated device in which a touch panel is superimposed on a liquid crystal panel.

[0029] (Operation of the energy storage system) The operation of the energy storage system 100 will be explained with reference to Figure 4. The process shown in Figure 4 is initiated when a power outage occurs in the grid 130 and power is no longer supplied from the grid 130. The CPU inside the control unit 110 reads a program stored in the memory inside the control unit 110 and executes it.

[0030] In step 300, the control unit 110 starts the charge / discharge control program and executes the first mode (hereinafter also referred to as the normal mode). That is, it sets both the upper limit of the discharge power and the upper limit of the charge power of the battery 102 to the first upper limit (for example, the rated value of the energy storage system 100 (for example, 6kW)) and executes the charge / discharge control program that controls the DC / DC converter 104 and the DC / AC converter 106. The charge / discharge control program is executed in parallel with this program. As a result, during a power outage in the grid 130, power is supplied from the energy storage system 100 to the load 132 in normal mode.

[0031] In step 302, the control unit 110 obtains the State of Charge (SOC) (%) representing the remaining charge of the battery 102 from the battery 102 and determines whether the obtained SOC is less than or equal to the first threshold Th1. If it is determined that the SOC is less than or equal to the first threshold Th1 (SOC ≤ Th1), the control proceeds to step 304. Otherwise (SOC > Th1), the control proceeds to step 316. The first threshold Th1 is, for example, Th1 = 15 (%). The first threshold Th1 can be stored in the memory of the control unit 110 in advance.

[0032] In step 304, the control unit 110 shifts the power storage system 100 to a second mode different from the first mode (hereinafter also referred to as the low power consumption mode). Specifically, the control unit 110 sets the upper limit value of the discharge power used by the charge-discharge control program to a second upper limit value (for example, several tens of W) smaller than the rated value. Thereafter, the control proceeds to step 306. Thereby, the output power from the power storage system 100 is limited to be below the second upper limit value. Note that the upper limit value of the charging power remains the first upper limit value.

[0033] In step 306, the control unit 110 instructs the remote controller 134 to present a message (hereinafter referred to as a transition message) indicating that the low power consumption mode has been entered. For example, the control unit 110 reads out the transition message from the internal memory and transmits it to the remote controller 134. If the transition message is stored in the memory of the remote controller 134, the control unit 110 may transmit a predetermined code (hereinafter referred to as a transition code) for instructing the display of the transition message to the remote controller 134. In response to this, the remote controller 134 displays a screen as shown in FIG. 5 on the display unit 136. On the display unit 136, it is displayed that the discharge of the storage battery 102 is restricted and that the power consumption of the load 132 is to be suppressed. Thereafter, the control proceeds to step 308. Note that the transition message is preferably displayed while the low power consumption mode is being executed, but may be erased after a predetermined time has elapsed.

[0034] In step 308, the control unit 110 acquires the SOC (%) representing the remaining battery level of the storage battery 102 from the storage battery 102, and determines whether or not the acquired SOC is equal to or greater than a second threshold value Th2. If it is determined that the SOC is equal to or greater than the second threshold value Th2 (SOC≥Th2), the control proceeds to step 312. Otherwise (SOC<Th2), the control proceeds to step 310. The second threshold value Th2 is a value greater than the first threshold value Th1, and for example, Th2 = 30 (%) is used. The second threshold value Th2 may be stored in advance in the memory of the control unit 110.

[0035] In step 310, the control unit 110 determines whether to terminate or not. If it is determined to terminate, the program terminates. Otherwise, control returns to step 308, and the process in step 308 is repeated. This maintains the low power consumption mode. For example, it is determined to terminate when the power outage on grid 130 is resolved and power is supplied again from grid 130.

[0036] In step 312, the control unit 110 switches the energy storage system 100 to normal mode (i.e., first mode). Specifically, the control unit 110 returns the upper limit of the discharge power used by the charge / discharge control program to the first upper limit. Then, the control moves to step 314. As a result, the output power from the energy storage system 100 is limited to the first upper limit (for example, the rated value of the energy storage system 100 (e.g., 6kW)).

[0037] In step 314, the control unit 110 instructs the remote control 134 to display a message indicating that the system has returned to normal mode (hereinafter referred to as the "recovery message"). For example, the control unit 110 reads the recovery message from its internal memory and transmits it to the remote control 134. If the recovery message is stored in the memory of the remote control 134, the control unit 110 only needs to transmit a predetermined code (hereinafter referred to as the "recovery code") to the remote control 134 that instructs the display of the recovery message. In response, the remote control 134 displays a screen on the display unit 136 as shown in Figure 6. 138 indicates that the discharge restriction on the battery 102 has been released. After that, the control proceeds to step 316. Preferably, the recovery message is erased after a predetermined time has elapsed.

[0038] In step 316, the control unit 110 determines whether to terminate, similar to step 310. If it determines to terminate, the program terminates. Otherwise, control returns to step 302, and the above process is repeated.

[0039] (Remote control operation)

[0040] Referring to Figure 7, the operation of the remote control 134 corresponding to the operation of the energy storage system 100 shown in Figure 4 will be explained. The process shown in Figure 7 is achieved by the CPU inside the remote control 134 reading and executing a program stored in the memory inside the remote control 134. Here, it is assumed that the transition message and return message described above are stored in the internal memory of the remote control 134.

[0041] In step 400, the remote control 134 determines whether the energy storage system 100 has received a transition code. If it is determined that it has received the code, the control proceeds to step 402. Otherwise, the control proceeds to step 404. If a transition message is sent from the control unit 110, the remote control 134 only needs to determine whether or not it has received the transition message.

[0042] In step 402, the remote control 134 displays a transition message. For example, the screen shown in Figure 5 is displayed on the display unit 136 of the remote control 134. If the remote control 134 has a speaker, it may also display (i.e., play) an audio message.

[0043] In step 404, the remote control 134 determines whether the energy storage system 100 has received a reset code. If it is determined that it has received one, the control proceeds to step 406. Otherwise, the control proceeds to step 408. If a reset message is sent from the control unit 110, the remote control 134 only needs to determine whether or not it has received the reset message.

[0044] In step 406, the remote control 134 displays a recovery message. For example, the screen shown in Figure 6 is displayed on the display unit 136 of the remote control 134. If the remote control 134 has a speaker, it may also display an audible message (i.e., play).

[0045] In step 408, the remote control 134 determines whether to terminate or not. If it determines to terminate, the program ends. Otherwise, control returns to step 400, and the above process is repeated.

[0046] As described above, when a power outage occurs in the grid 130 and power is no longer supplied from the grid 130, the energy storage system 100 discharges the battery 102 and supplies power to the load 132 in normal mode (i.e., first mode). Subsequently, when the battery charge of the battery 102 decreases and falls below the second threshold Th1 (e.g., 15%), the energy storage system 100 switches to low-power consumption mode (i.e., second mode). The upper limit of the discharge power of the battery 102 is set to a second upper limit (e.g., several tens of watts), which is smaller than the first upper limit (e.g., 6 kW) in normal mode. This suppresses the decrease in the battery charge of the battery 102 and prevents the energy storage system 100 from being unable to discharge during a grid power outage. Therefore, since the energy storage system 100 functions as a pseudo-grid, the solar power generation system 120 can connect to the grid and output power, and the wasted power generated by the solar power generation system 120 can be suppressed.

[0047] As described above, by setting the second threshold Th2 to a value greater than the first threshold Th1, it is possible to prevent the system from switching back to low-power mode within a short period of time after returning from low-power mode to normal mode. In other words, it is possible to prevent repeated switching between normal mode and low-power mode in a short period of time.

[0048] Typically, energy storage systems have a minimum discharge limit set to ensure that power is available from the system in the event of a power outage in the grid. The minimum discharge limit is the lower limit of the battery charge when power is supplied from the grid. The minimum discharge limit can be changed, for example, by operating a remote control. For example, the minimum discharge limit can be set to be adjustable by the user within the range of 0% to 50%. In order for the energy storage system 100 to perform the low power consumption mode as described above, the minimum discharge limit of the battery 102 must be at a certain value. In the energy storage system 100, it is preferable to limit the minimum discharge limit, which can be changed by operating the remote control 134, to a value greater than the first threshold Th1. For example, in the energy storage system 100, the minimum discharge limit of the battery 102 can be changed within the range of the second threshold Th2 (e.g., 30%) to 50%. This allows for a longer period during a power outage on grid 130, during which the low-power consumption mode (i.e., mode 2) can be maintained.

[0049] In low-power consumption mode, the power supply from the energy storage system 100 is limited (for example, by several tens of watts). Therefore, if the power consumption of the load 132 is the same as before the mode switch (i.e., normal mode), the energy storage system 100 will not be able to maintain its output voltage (e.g., single-phase three-wire 200V and 100V), and the voltage will drop. In that case, the energy storage system 100 will shut down due to its own protection function, and a power outage will occur indoors. As described above, when the energy storage system 100 transitions from normal mode (i.e., first mode) to low-power consumption mode (i.e., second mode), it causes the remote control 134 to display a message encouraging the user to reduce power consumption indoors. This is expected to encourage the user to shut down high-power devices, thereby reducing the power consumption of the load 132. Therefore, the period during which the energy storage system 100 can maintain low-power consumption mode (i.e., second mode) during a power outage in the grid 130 can be extended.

[0050] The above describes a case where a second upper limit is set as the upper limit of the discharge power of the battery 102 during a power outage in grid 130, but it is not limited to this. The second upper limit may also be set as the upper limit of the output power of the energy storage system 100 (i.e., the output power of the DC / AC converter 106). The second upper limit is not limited to the tens of watts mentioned above. The second upper limit may be a value greater than 0 and less than the first upper limit, and may be a value of 100 watts or more. Furthermore, the first and second upper limits may not only be set by active power (unit: kW), but may also be set by apparent power (unit: kVA).

[0051] The above describes a case where the operating mode of the energy storage system 100, namely normal mode and low power consumption mode, is switched according to the State of Charge (SOC) of the battery 102, i.e., the remaining battery charge, but is not limited to this. For example, the normal mode and low power consumption mode may be switched according to the time of day or the amount of power generated by the solar power generation system 120. In this case as well, the decrease in the remaining battery charge of the battery 102 can be suppressed, and the inability to discharge from the energy storage system 100 during a grid power outage can be avoided. Therefore, since the energy storage system 100 functions as a pseudo-grid, the solar power generation system 120 can output power to the grid, and the wasted power generated by the solar power generation system 120 can be suppressed.

[0052] In addition, auxiliary input terminals can be provided in the energy storage system 100. However, in that case, the number of components will increase, and the manufacturing cost and size of the energy storage system 100 will increase. On the other hand, in this embodiment, the above-mentioned effects can be obtained regardless of whether or not auxiliary input terminals are provided. Therefore, if the energy storage system does not have auxiliary input terminals, the above-mentioned problems that would arise from providing auxiliary input terminals, namely the increase in the number of components, the increase in manufacturing costs, and the increase in the size of the equipment, can be suppressed.

[0053] (modified version) In energy storage systems, the remaining battery level is usually displayed on a remote control or similar device located indoors. As mentioned above, if the system switches to a low-power consumption mode and limits the output power to several tens of watts when the battery level falls below 15%, for example, the user may become dissatisfied with the imbalance between the power supplied by the energy storage system and the remaining battery level. The modified version is intended to prevent such dissatisfaction from the user. The power supply system related to the modified version is configured similarly to Figure 3 and includes an energy storage system 100, a solar power generation system 120, and a remote control 134. The following explanation will refer to the configuration shown in Figure 3.

[0054] Referring to Figure 8, the operation of the modified energy storage system will be explained. The process shown in Figure 8 is achieved when a power outage occurs in grid 130 and power is no longer supplied from grid 130, by the CPU inside the control unit 110 reading and executing a program stored in the memory inside the control unit 110. The flowchart shown in Figure 8 is the same as the flowchart in Figure 4, but with steps 330 to 334 added between steps 300 and 302, and step 336 added between steps 306 and 308. In Figure 8, the processing of steps with the same reference numerals as in Figure 4 is the same as in Figure 4. Therefore, without repeating redundant explanations, we will mainly explain the differences.

[0055] In step 300, the charge / discharge control program is started and power supply begins in normal mode. Then, in step 330, the control unit 110 obtains the State of Charge (SOC) (%) representing the remaining battery charge from the storage battery 102 and determines whether the obtained SOC is less than or equal to the third threshold Th3. If it is determined that the SOC is less than or equal to the third threshold Th3 (SOC ≤ Th3), the control proceeds to step 334. Otherwise (SOC > Th3), the control proceeds to step 332. The third threshold Th3 is, for example, Th3 = 30 (%). The third threshold Th3 can be stored in the memory of the control unit 110 beforehand.

[0056] In step 332, the control unit 110 transmits the SOC (i.e., battery level) acquired in step 330 to the remote control. The remote control 134, upon receiving the SOC, displays the received SOC as the battery level of the storage battery 102 on the display unit 136. After that, the control proceeds to step 302.

[0057] On the other hand, if SOC ≤ Th3, in step 334, the control unit 110 corrects the SOC (i.e., battery level) obtained in step 330 to a smaller value (hereinafter referred to as the display battery level) and transmits it to the remote control. The remote control 134, upon receiving the display battery level, displays the received display battery level as the battery level of the storage battery 102 on the display unit 136. After that, the control proceeds to step 302.

[0058] Referring to Figure 9, the displayed battery level is set according to the State of Charge (SOC) (i.e., battery level) of the storage battery 102, as shown by the dashed line. Specifically, if the battery level of storage battery 102 is greater than 30%, the displayed battery level is set to the same value as the battery level of storage battery 102. When the battery level of storage battery 102 is between 30% and 15%, the displayed battery level is set to decrease from 30% in proportion to the battery level. For example, if the battery level and the displayed battery level are represented by positive integer values, when the battery level of storage battery 102 is between 30% and 16% (including the extremes of 30% and 16%), the displayed battery level b (%) is calculated from the actual battery level a (%) using the formula b = 2 × a - 30 (%). That is, the displayed battery level b is set to a value smaller than the actual battery level a of storage battery 102. When the battery level of the storage battery 102 falls below 15%, the displayed battery level is set to a constant value (for example, 1%) until it reaches 1%. Furthermore, as the battery level of the storage battery 102 decreases, the displayed battery level is reset to the same value as the battery level of the storage battery 102.

[0059] Subsequently, in step 306, the remote control 134 is instructed to display a transition message. Then, in step 336, the control unit 110 transmits a certain display battery level (for example, 1%) to the remote control 134 as the battery level of the storage battery 102. As a result, the remote control 134 displays the received display battery level as the battery level of the storage battery 102 on the display unit 136. For example, the words "Battery level: 1%" are displayed on a part of the screen shown in Figure 5 as the battery level of the storage battery 102.

[0060] This reduces the likelihood of users becoming dissatisfied with an imbalance between the power supplied by the energy storage system 100 (e.g., tens of watts) and the remaining battery capacity, as the display will show a much smaller value (e.g., 1%) than the actual remaining battery capacity of the battery storage system 102 when the energy storage system 100 switches to low power consumption mode.

[0061] The relationship between the battery level and the displayed battery level is not limited to the case shown in Figure 9. In low-power mode, it is sufficient for the displayed battery level to be less than the actual battery level. For example, in normal mode, the displayed battery level may be equal to the battery level, and when the battery level drops below 15% and the system switches to low-power mode, the displayed battery level may be set to 1%.

[0062] As shown in Figure 9, if the battery level is displayed as 1% immediately after the battery level drops below 15% and the device switches to low power consumption mode, without changing the displayed battery level, the battery level displayed on the remote control 134 will suddenly drop from 15% to 1%, which may cause the user to feel uneasy. In contrast, as shown in Figure 9, while the battery level of the storage battery 102 is between 30% and 15%, the displayed battery level is linearly reduced from 30% in proportion to the battery level, so that the user does not feel uneasy.

[0063] The remaining battery level for the display in low power consumption mode is not limited to the 1% mentioned above. The remaining battery level for the display in low power consumption mode may be greater than 1% or 0%. Also, the third threshold Th3 is not limited to 30%. It may be greater than or less than 30%. In the above, the case where the third threshold Th3 and the second threshold Th2 are equal (specifically both are 30%) was described, but it is not limited to this. The third threshold Th3 may be greater than the first threshold Th1 and may be different from the second threshold Th2.

[0064] The present disclosure has been described above by describing embodiments, but the embodiments described above are illustrative and the present disclosure is not limited to the embodiments described above. The scope of the present disclosure is given by the claims, with reference to the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wording contained herein. [Explanation of symbols]

[0065] 100, 900, 950 energy storage systems 102, 902 storage batteries 104, 904 DC / DC converter 106, 906 DC / AC converter 108, 908, 952, 954 Relays 110 Control Unit 120, 920, 960 Solar Power Generation Systems 122,922 PV panels 124,924,962 PCS 130, 930 lines 132,932 load 134 Remote control 136 Display section 300, 302, 304, 306, 308, 310, 312, 314, 316, 330, 332, 334, 336, 400, 402, 404, 406, 408 956 Auxiliary input terminal 964 Standalone output terminal 970 General load 972 Specific Load

Claims

1. Storage batteries and A power storage system including a control unit that controls the discharge of the battery, The control unit, In response to the loss of power supply from the grid, the system executes a first mode in which the battery is discharged to output power below a first upper limit to an external load of the energy storage system, or a second mode in which the battery is discharged to output power below a second upper limit, which is smaller than the first upper limit, to the external load. Depending on predetermined conditions, the first mode and the second mode are switched. The predetermined conditions include conditions relating to the remaining battery capacity of the storage battery, in this energy storage system.

2. The aforementioned predetermined conditions include conditions relating to the remaining battery charge of the storage battery, The energy storage system according to claim 1, wherein the control unit switches from the first mode to the second mode when the remaining battery charge falls below a first threshold while the first mode is being executed.

3. The control unit, The storage battery is charged with surplus electricity supplied from the solar power generation system. The energy storage system according to claim 2, wherein, while the second mode is being executed, the system switches from the second mode to the first mode when the remaining battery charge becomes greater than or equal to a second threshold, which is greater than the first threshold, due to charging with the surplus power.

4. The remote control is also included. The aforementioned remote control is The system accepts an input for the discharge limit battery level, which is the lower limit of the remaining battery capacity of the storage battery, in order to limit the discharge of the storage battery when power is supplied from the aforementioned system. The energy storage system according to claim 2 or 3, wherein, upon receiving an input value greater than the first threshold, the system sets the input value as the lower limit of battery discharge.

5. A storage battery, A control unit for controlling the discharge of the storage battery, Including the remote control, The control unit, In response to the loss of power supply from the grid, the system executes a first mode in which the battery is discharged to output power below a first upper limit, or a second mode in which the battery is discharged to output power below a second upper limit, which is smaller than the first upper limit. Depending on predetermined conditions, the first mode and the second mode are switched. A power storage system that, when switching from the first mode to the second mode, displays a message on the remote control encouraging a reduction in power consumption.

6. A storage battery, A control unit for controlling the discharge of the storage battery, Including the remote control, The control unit, In response to the loss of power supply from the grid, the system executes a first mode in which the battery is discharged to output power below a first upper limit, or a second mode in which the battery is discharged to output power below a second upper limit, which is smaller than the first upper limit. Depending on predetermined conditions, the first mode and the second mode are switched. The remote control displays a numerical value corresponding to the remaining battery level of the storage battery. A power storage system that, while the second mode is in operation, makes the value less than the remaining battery charge.

7. A power storage system according to any one of claims 1 to 3, 5 and 6, Including a solar power generation system, The control unit is a power supply system that charges the storage battery with surplus power from the solar power generation system.

8. A method for controlling an energy storage system having a battery, This includes a control step for controlling the discharge of the storage battery, The control step is, The process involves, in response to the loss of power supply from the grid, executing a first mode in which the battery is discharged to output power below a first upper limit to an external load of the energy storage system, or a second mode in which the battery is discharged to output power below a second upper limit, which is smaller than the first upper limit, to the external load; The process includes a step of switching between the first mode and the second mode according to predetermined conditions, A control method in which the predetermined conditions include conditions relating to the remaining battery capacity of the storage battery.

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