Power conditioner device and power supply system including the same

Abstract

To provide a power conditioner device in which tripping of an ampere breaker is less likely to occur than before.SOLUTION: A power conditioner device 10A includes a power conversion unit 11 capable of performing a discharge operation of converting DC power supplied from a power storage device 30 into predetermined AC power and supplying the AC power to a first customer power distribution line 2, and a control unit 12 for controlling the power conversion unit 11. When the remaining amount of stored power in the power storage device 30 falls below a predetermined first lower limit value while the controller 12 is causing the power converter 11 to perform the discharging operation, the controller 12 determines whether or not the ampere breaker 4 trips due to the stopping of the discharging operation, (1) causes the power converter 11 to continue the discharging operation when the controller 12 determines that the ampere breaker 4 trips, and (2) causes the power converter 11 to stop the discharging operation when the controller 12 determines that the ampere breaker 4 does not trip.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conditioner device capable of supplying power stored in a power storage device to a consumer load, and a power supply system including the device. [Background technology]

[0002] Conventionally, power supply systems have been known that include a photovoltaic power generation device, a power storage device, and a power conditioner connected to them. Some power supply systems have a function of always storing a certain amount of power in the power storage device in preparation for a power outage in the commercial power grid, in other words, a function of preventing further discharge when the remaining amount of stored power falls below a lower limit (e.g., 30%) predetermined by the user (see, for example, "Emergency Safety Settings" on page 26 of Non-Patent Document 1). Some power supply systems also have a function of preventing tripping by discharging the power storage device and supplying the discharged power to the consumer load when the difference between the current consumed by the consumer load and the current (contracted amperes) at which the ampere breaker trips becomes small (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-005332 [Non-patent literature]

[0004] [Non-Patent Document 1] "Nichicon Power Conditioner and Battery Unit Instruction Manual", [online], Nichicon Corporation, [Searched June 1, 2024], Internet<URL:https: / / www.nichicon.co.jp / products / ess / pdf / t1_torisetsu_42830-13.pdf> Summary of the Invention [Problem to be solved by the invention]

[0005] In some cases, users set the contracted amperes to the minimum necessary in order to save on electricity bills paid to electric power companies. In this case, in a power supply system having the above-mentioned two functions, if the current consumption of a consumer load temporarily becomes higher than the expected value, the remaining amount of stored electricity in the power storage device falls to a lower limit value, and the discharged power of the power storage device is no longer supplied to the consumer load (i.e., the assist by the power storage device is lost), the current flowing through the ampere breaker may exceed the contracted ampere, causing the ampere breaker to trip.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power conditioner device in which ampere breaker tripping is less likely than in the past, and a power supply system including the device. [Means for solving the problem]

[0007] In order to solve the above problem, the power conditioner device of the present invention is a device connected to a consumer's distribution line that supplies AC power supplied from a commercial power system via an ampere breaker to a consumer load, and to a power storage device, and is equipped with a power conversion unit that can perform a discharging operation to convert DC power supplied from the power storage device into a predetermined AC power and supply it to the consumer's distribution line, and a control unit that controls the power conversion unit, and when the remaining storage capacity of the power storage device falls below a predetermined first lower limit value while the power conversion unit is performing a discharging operation, the control unit determines whether the ampere breaker will trip by stopping the discharging operation, and (1) if it is determined that the ampere breaker will trip, it causes the power conversion unit to continue the discharging operation, and (2) if it is determined that the ampere breaker will not trip, it causes the power conversion unit to stop the discharging operation.

[0008] In this configuration, even after the remaining amount of stored electricity in the power storage device falls below the first lower limit, the discharging operation of the power storage device continues if it is deemed necessary to prevent the ampere breaker from tripping. Therefore, with this configuration, the discharging operation of the power storage device stops as soon as the remaining amount of stored electricity in the power storage device falls below the first lower limit, thereby preventing the ampere breaker from tripping.

[0009] It is preferable that the control unit of the power conditioner device is configured to, when it determines that a trip will occur, cause the power conversion unit to continue discharging until the remaining amount of stored electricity falls below a predetermined second lower limit value (where the second lower limit value is less than the first lower limit value), or until the decrease in the remaining amount of stored electricity from the time of the determination exceeds a predetermined upper limit value.

[0010] According to this configuration, a certain amount of power can be left in the power storage device in preparation for a power outage in the commercial power grid.

[0011] It is preferable that the control unit of the power conditioner device is configured to stop the power conversion unit from performing a subsequent discharge operation when the subsequent discharge operation becomes unnecessary while the power conversion unit is performing the subsequent discharge operation.

[0012] This configuration allows more power to remain in the power storage device when the power consumption of the consumer load decreases, etc. In other words, this configuration makes it possible to prevent the remaining amount of stored power in the power storage device from falling significantly below the first lower limit value.

[0013] It is preferable that the control unit of the power conditioner device is configured to cause the power conversion unit to perform the subsequent discharge operation if the subsequent discharge operation becomes necessary after the power conversion unit has stopped the subsequent discharge operation.

[0014] This configuration can prevent the ampere breaker from tripping if the power consumption of the consumer load increases after it has been determined that it is okay to stop the discharge operation.

[0015] The control unit of the power conditioner device is preferably configured to, when it is determined that a trip will occur, cause the power conversion unit to continue the discharging operation and execute predetermined notification control.

[0016] According to this configuration, it is possible to make the user aware that the remaining amount of stored power in the power storage device has fallen below the first lower limit. If the user who notices that the remaining amount of stored power is below the first lower limit stops the operation of the consumer load (general load) connected to the consumer's distribution line, the ampere breaker will not trip even if the discharging operation is stopped. It can be said that the notification control has the effect of preventing the remaining amount of stored power in the power storage device from falling significantly below the first lower limit.

[0017] In order to solve the above problem, the power supply system of the present invention is a system comprising a consumer-premises distribution line that supplies AC power supplied from a commercial power system via an ampere breaker to a consumer load, a storage device, and a power conditioner device connected to the consumer-premises distribution line and the storage device, wherein the power conditioner device comprises a power conversion unit that can perform a discharging operation to convert DC power supplied from the storage device into a predetermined AC power and supply it to the consumer-premises distribution line, and a control unit that controls the power conversion unit, and when the remaining storage capacity of the storage device falls below a predetermined first lower limit value while the power conversion unit is performing a discharging operation, the control unit determines whether the ampere breaker will trip by stopping the discharging operation, and (1) if it is determined that the ampere breaker will trip, it causes the power conversion unit to continue the discharging operation, and (2) if it is determined that the ampere breaker will not trip, it causes the power conversion unit to stop the discharging operation. A power supply system characterized by:

[0018] In this configuration, even after the remaining amount of stored electricity in the power storage device falls below the first lower limit, the discharging operation of the power storage device continues if it is deemed necessary to prevent the ampere breaker from tripping. Therefore, with this configuration, the discharging operation of the power storage device stops as soon as the remaining amount of stored electricity in the power storage device falls below the first lower limit, thereby preventing the ampere breaker from tripping. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a power conditioner device in which tripping of an ampere breaker is less likely than in the past, and a power supply system including the device. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram showing a schematic configuration of a power supply system according to an embodiment of the present invention; [Figure 2] FIG. 3 is a flowchart showing the operation of the power supply system according to the embodiment of the present invention. [Figure 3] FIG. 10 is a diagram showing a schematic configuration of a power supply system according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of a power supply system and a power conditioner device according to the present invention will be described with reference to the accompanying drawings.

[0022] [Example] FIG. 1 shows a power supply system 1A according to an embodiment of the present invention. As shown in the figure, the power supply system 1A includes consumer-premises distribution lines 2 and 3 that supply commercial AC power, supplied from a commercial power system G via an ampere breaker 4, to consumer loads L1 and L2, an operation device 20, a power storage device 30, a solar power generation device 40, and a power conditioner device 10A connected to these. The consumer load L1 is a general load installed within the consumer premises. The consumer load L2 is an important load installed within the consumer premises that must continue to operate even when an abnormality, such as a power outage, occurs in the commercial power system G.

[0023] The solar power generation device 40 includes a solar panel and a power conversion unit (not shown). The power conversion unit has an input terminal and an output terminal. The input terminal is connected to the solar panel, and the output terminal is connected to the first consumer distribution line 2 via a second parallel-off relay 6. The output terminal is also connected to the power conditioner device 10A.

[0024] The second parallel-off relay 6 is configured to be in an open state when an abnormality such as a power outage occurs in the commercial power system G, and to be in a closed state at other times.

[0025] When the second parallel-off relay 6 is in the closed state (i.e., when the photovoltaic power generation device 40 is not parallel-off), the power conversion unit of the photovoltaic power generation device 40 can convert the power generated by the photovoltaic panel into AC power equivalent to commercial AC power and supply it to the first consumer power distribution line 2. On the other hand, when the second parallel-off relay 6 is in the open state (i.e., when the photovoltaic power generation device 40 is parallel-off), the power conversion unit of the photovoltaic power generation device 40 can convert the power generated by the photovoltaic panel into AC power or DC power equivalent to commercial AC power and supply it to the power conditioner device 10A.

[0026] The operation device 20 is a remote control with a touch panel display installed in the consumer's premises. The operation device 20 can present the operation status of the power storage device 30, the solar power generation device 40, etc. to the user in a highly visible manner based on the operation status information received from the power conditioner device 10A. The operation device 20 can also transmit command information input by the user to the power conditioner device 10A.

[0027] The power storage device 30 includes a lithium-ion battery and a battery management system (BMS) that monitors the battery. The power storage device 30 may be configured by connecting a plurality of power storage units in a daisy chain. An example of the capacity of the power storage device 30 is 4 kWh.

[0028] The power conditioner device 10A includes a power conversion unit 11, a control unit 12, and a storage unit 13.

[0029] The power conversion unit 11 is a bidirectional power conversion circuit and has DC input / output terminals and AC input / output terminals. The DC input / output terminals are connected to the power storage device 30, and the AC input / output terminals are connected to the first consumer's distribution line 2 via a first parallel-off relay 5. The AC input / output terminals are also connected to the output terminals of the power conversion unit constituting the solar power generation device 40. The AC input / output terminals can also be connected to the second consumer's distribution line 3 via a path switch 7.

[0030] Like the second parallel-off relay 6, the first parallel-off relay 5 is configured to be in an open state when an abnormality such as a power outage occurs in the commercial power system G, and to be in a closed state at other times.

[0031] The path switch 7 is configured to connect the second consumer distribution line 3 to the power conditioner device 10A (the AC side input / output terminal of the power conversion unit 11) except in special cases such as maintenance.

[0032] The power conversion unit 11 can perform a discharging operation of converting DC power (discharge power) supplied from the power storage device 30 into AC power equivalent to commercial AC power and supplying it to the first consumer power distribution line 2 or the second consumer power distribution line 3.

[0033] More specifically, when the first parallel-off relay 5 is in a closed state (i.e., when the power conditioner device 10A is not parallel-off), the power conversion unit 11 supplies discharged power to the first consumer power distribution line 2 (general load L1) and the second consumer power distribution line 3 (important load L2). The commercial AC power supplied from the first consumer power distribution line 2 to the power conditioner device 10A may be directly supplied to the second consumer power distribution line 3 (important load L2).

[0034] On the other hand, when the first parallel-off relay 5 is in the open state (i.e., when the power conditioner device 10A is parallel-off), the power conversion unit 11 supplies discharged power to the second consumer power distribution line 3 (important load L2). At this time, power generated by the solar power generation device 40 is also supplied to the second consumer power distribution line 3.

[0035] When the first parallel-off relay 5 is in a closed state, the power conversion unit 11 can also perform a charging operation in which the commercial AC power supplied from the first consumer distribution line 2 is converted into a predetermined DC power and supplied to the storage device 30.

[0036] The control unit 12 controls the discharging operation and the charging operation of the power conversion unit 11. The control unit 12 controls the power conversion unit 11 while referring to the detection result of the grid current detector 8 provided on the first consumer distribution line 2, the detection result of the charge / discharge current detector 31 provided between the power conditioner device 10A and the power storage device 30, various information provided from the BMS of the power storage device 30, and various setting information stored in the memory unit 13.

[0037] The storage unit 13 stores various setting information. In this embodiment, the storage unit 13 stores the contract ampere (40 A in this embodiment), a first lower limit value (30% in this embodiment), and a second lower limit value (20% in this embodiment). These are stored by the user via the operation device 20. The first lower limit value corresponds to the lower limit value set by the emergency safety setting (see, for example, Non-Patent Document 1).

[0038] Next, how the control unit 12 controls the discharge operation of the power conversion unit 11 will be described in more detail with reference to FIG.

[0039] In step S1, the control unit 12 causes the power conversion unit 11 to start a discharge operation. Typically, the control unit 12 executes step S1 so as to reduce the purchased power (so that the purchased power becomes zero) when the remaining amount of stored power in the power storage device 30 is sufficient and the amount of power supplied from the commercial power grid G ​​(hereinafter referred to as "purchased power") is relatively large. The control unit 12 can acquire the remaining amount of stored power from the BMS of the power storage device 30. The control unit 12 can also calculate the purchased power from the detection result of the grid current detector 8.

[0040] In step S2, which is executed following step S1, the control unit 12 determines whether the remaining amount of stored power is below the first lower limit (30%) stored in the memory unit 13. If it is determined that the remaining amount of stored power is not below the first lower limit, the control unit 12 continues the discharging operation (step S3). The control unit 12 repeatedly executes steps S2 and S3 until the remaining amount of stored power falls below the first lower limit. Naturally, the control unit 12 stops the discharging operation when it is no longer necessary to continue the discharging operation during this repetition (for example, when the current consumption of the general load L1 and the important load L2 approaches zero).

[0041] In step S4, which is executed when it is determined in step S2 that the remaining amount of stored electricity is below the first lower limit, the control unit 12 determines whether or not stopping the discharging operation will trip the ampere breaker 4. In this embodiment, the control unit 12 makes this determination based on the contracted ampere (40 A) stored in the memory unit 13, the detection result of the grid current detector 8, and the detection result of the charge / discharge current detector 31.

[0042] If the detection result of the grid current detector 8 (current flowing from the commercial power grid G ​​toward the first consumer distribution line 2) is 15 A and the detection result of the charge / discharge current detector 31 (current flowing from the power storage device 30 toward the power conditioner device 10A) is 30 A, the control unit 12 determines to "trip" because it is predicted that the current flowing through the ampere breaker 4 will increase from 15 A to 45 A (>contract amperes) when the discharging operation is stopped.Also, if the detection result of the grid current detector 8 is 15 A and the detection result of the charge / discharge current detector 31 is 20 A, it is predicted that the current flowing through the ampere breaker 4 will not reach the contract amperes even when the discharging operation is stopped, so it determines to "not trip."

[0043] In step S8, which is executed when it is determined in step S4 that "tripping will not occur," control unit 12 stops the discharging operation, thereby leaving power storage device 30 with a level of power slightly below the first lower limit (30%).

[0044] On the other hand, in step S5, which is executed when it is determined in step S4 that "tripping will occur," the control unit 12 continues the discharging operation. This can prevent the ampere breaker 4 from tripping. However, the remaining amount of electricity stored in the electricity storage device 30 will be further reduced compared to when step S4 was executed.

[0045] In step S6, which is executed after step S5, the control unit 12 determines whether the remaining amount of stored power is below the second lower limit (20%) stored in the storage unit 13 or not.

[0046] If the control unit 12 determines in step S6 that the remaining amount of stored power is below the second lower limit, it stops the discharging operation (step S8), leaving the power storage device 30 with a power level slightly below the second lower limit (20%).

[0047] On the other hand, if the control unit 12 determines in step S6 that the remaining amount of stored power is not below the second lower limit, it determines whether or not a discharging operation is necessary (step S7). In this embodiment, the control unit 12 determines that a discharging operation is "necessary" if the purchased power exceeds a predetermined threshold, and determines that a discharging operation is "not necessary" if the purchased power does not exceed a predetermined threshold. This threshold is a value set lower than the contracted amperes and is stored in the memory unit 13, for example. Note that this threshold may be the same as or different from the threshold at which a discharging operation from the power storage device 30 is started (see the description of step S1).

[0048] If the control unit 12 determines in step S7 that the discharging operation is "necessary," it continues the discharging operation (step S5). The control unit 12 repeatedly executes steps S5, S6, and S7 until the remaining amount of stored power falls below the second lower limit or the discharging operation becomes unnecessary.

[0049] On the other hand, if the control unit 12 determines in step S7 that the discharge is "unnecessary," the control unit 12 stops the discharge (step S8).

[0050] In this way, the power supply system 1A and power conditioner device 10A according to this embodiment are configured to continue the discharging operation until the remaining amount of stored electricity falls below the second lower limit (where the second lower limit<the first lower limit) only when it is determined that the discharging operation is necessary to prevent tripping of the ampere breaker 4, even after the remaining amount of stored electricity falls below the first lower limit. Therefore, the power supply system 1A and power conditioner device 10A according to this embodiment can suppress tripping of the ampere breaker more than conventionally.

[0051] [Variations] Although the embodiments of the power supply system and the power conditioner device according to the present invention have been described above, the present invention is not limited to these.

[0052] For example, the power conditioner device according to the present invention may be configured to be connected to a V2H (Vehicle to Home) device 50 that charges and discharges an on-board battery of an electric vehicle 60, such as an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV), as in the case of power conditioner device 10B shown in Fig. 3. The power conditioner device according to the present invention may also be configured to be connected to a solar panel and to process power generated by the solar panel. Hereinafter, for convenience, such a power conditioner device will be referred to as power conditioner device 10C.

[0053] Furthermore, when it is determined in step S4 that "tripping will occur," the control unit 12 of the power conditioner apparatuses 10A, 10B, and 10C may be configured to execute predetermined notification control for notifying the user that the remaining amount of stored electricity has fallen below the first lower limit. An example of the notification control is, but is not limited to, displaying a message on the touch panel display of the operation device 20.

[0054] Furthermore, the storage unit 13 of the power conditioner devices 10A, 10B, and 10C may store an upper limit (e.g., 10%) of the decrease in the remaining amount of stored electricity instead of the second lower limit. In this case, the control unit 12 determines in step S6 whether the decrease in the remaining amount of stored electricity from the time when the determination of "tripping" was made in step S4 (i.e., the time when the remaining amount of stored electricity fell below the first lower limit (30%)) has exceeded the upper limit (10%). This determination is synonymous with determining whether the remaining amount of stored electricity has fallen below the second lower limit (20%).

[0055] Furthermore, the control unit 12 of the power conditioner apparatuses 10A, 10B, 10C may make the determination in step S7 (determine whether or not a discharge operation is necessary) based on information other than the purchased power.

[0056] Furthermore, the control unit 12 of the power conditioner devices 10A, 10B, 10C may execute step S5 (restart the discharging operation) if a situation in which the discharging operation is "necessary" is observed after determining in step S7 that the discharging operation is "unnecessary" and stopping the discharging operation (step S8). An example of a situation in which the discharging operation is "necessary" is a situation in which the purchased power exceeds a predetermined threshold, but is not limited to this.

[0057] Furthermore, the operation device 20 is not limited to being installed in the consumer's premises, and may be, for example, a mobile terminal such as a smartphone carried by a user. In this case, the mobile terminal needs to have a dedicated application or a general-purpose web browser installed therein for accessing information provided by the power conditioner 10A.

[0058] The charge / discharge current detector 31 may be included in the power conditioner devices 10A, 10B, and 10C or the power storage device 30.

[0059] Furthermore, the power storage device 30 is not limited to a device dedicated to storing power. For example, the power storage device 30 may be a combination of a V2H device and an electric vehicle connected to it. In this case, the control unit 12 controls the discharge of the large-capacity storage battery based on the contract ampere, the first lower limit, the second lower limit, and the remaining amount of power stored in the large-capacity storage battery mounted on the electric vehicle.

[0060] Furthermore, the path switch 7 may be configured to connect the second consumer power distribution line 3 to the power conditioners 10A, 10B, and 10C (the AC input / output terminals of the power conversion unit 11) when an abnormality such as a power outage occurs in the commercial power system G, and to connect the second consumer power distribution line 3 to the first consumer power distribution line 2 at other times. The power conversion unit 11 can supply discharged power to the first consumer power distribution line 2 (general load L1) and the second consumer power distribution line 3 (important load L2) when the first parallel-off relay 5 is in a closed state (i.e., when the power conditioners 10A, 10B, and 10C are not parallel-off; at this time, the path switch 7 connects the second consumer power distribution line 3 to the first consumer power distribution line 2). Furthermore, the power conversion unit 11 can supply the discharged power to the second consumer power distribution line 3 (important load L2) when the first parallel-off relay 5 is in the open state (i.e., when the power conditioner devices 10A, 10B, and 10C are parallel-off. At this time, the path switcher 7 connects the second consumer power distribution line 3 to the power conditioner devices 10A, 10B, and 10C). The power conversion unit 11 can also supply the power generated by the solar power generation device 40 to the first consumer power distribution line 2 (general load L1) and the second consumer power distribution line 3 (important load L2) together with the discharged power.

[0061] In addition, the contracted amperes, the first lower limit value, the second lower limit value and the upper limit value may be stored in a distributed manner in the memory units 13 of the power conditioner devices 10A, 10B, 10C and the operating device 20, or may be stored only in the operating device 20. [Explanation of symbols]

[0062] 1A, 1B Power Supply System 2 Distribution line within the first customer 3 2nd consumer power distribution line 4 amp breaker 5. 1st parallel-off relay 6 Second parallel-off relay 7 Route Switcher 8 System Current Detector 10A, 10B, 10C Power conditioner device 11 Power conversion section 12 Control Unit 13 Storage section 20 Operating device 30 Electricity storage device 31 Charge / discharge current detector 40 Solar power generation equipment 50 V2H equipment 60 electric vehicle L1 General load (customer load) L2 Important load (customer load)

Claims

1. A power conditioner device connected to a consumer distribution line that supplies AC power supplied from a commercial power system via an ampere breaker to a consumer load and to a power storage device, a power conversion unit that can perform a discharging operation of converting DC power supplied from the power storage device into predetermined AC power and supplying the AC power to the customer's power distribution line; a control unit that controls the power conversion unit; Equipped with When the remaining amount of stored electricity of the power storage device falls below a predetermined first lower limit value while the control unit is causing the power conversion unit to perform the discharging operation, the control unit determines whether the ampere breaker will trip due to the stop of the discharging operation, and (1) if it is determined that the ampere breaker will trip, causes the power conversion unit to continue the discharging operation, and (2) if it is determined that the ampere breaker will not trip, causes the power conversion unit to stop the discharging operation. A power conditioner device characterized by the above.

2. When the control unit determines that a trip will occur, the control unit causes the power conversion unit to continue the discharging operation only until the remaining amount of stored electricity falls below a predetermined second lower limit value (wherein the second lower limit value is smaller than the first lower limit value) or until the amount of decrease in the remaining amount of stored electricity from the time of the determination exceeds a predetermined upper limit value. The power conditioner device according to claim 1 .

3. When the control unit is causing the power conversion unit to perform a subsequent discharging operation and the subsequent discharging operation becomes unnecessary, the control unit causes the power conversion unit to stop the subsequent discharging operation. The power conditioner device according to claim 2 .

4. When the subsequent discharging operation becomes necessary after the control unit has stopped the subsequent discharging operation, the control unit causes the power conversion unit to perform the subsequent discharging operation. The power conditioner device according to claim 3 .

5. When it is determined that a trip will occur, the control unit causes the power conversion unit to continue the discharging operation and executes a predetermined notification control. The power conditioner device according to any one of claims 1 to 4.

6. A power supply system including: a consumer-side distribution line that supplies AC power supplied from a commercial power system via an ampere breaker to a consumer load; a power storage device; and a power conditioner device connected to the consumer-side distribution line and the power storage device, The power conditioner device is a power conversion unit that can perform a discharging operation of converting DC power supplied from the power storage device into predetermined AC power and supplying the AC power to the customer's power distribution line; a control unit that controls the power conversion unit; Equipped with When the remaining amount of stored electricity of the power storage device falls below a predetermined first lower limit value while the control unit is causing the power conversion unit to perform the discharging operation, the control unit determines whether the ampere breaker will trip due to the stop of the discharging operation, and (1) if it is determined that the ampere breaker will trip, causes the power conversion unit to continue the discharging operation, and (2) if it is determined that the ampere breaker will not trip, causes the power conversion unit to stop the discharging operation. A power supply system characterized by:

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