Uninterruptible power supply system

Abstract

This system provides an uninterruptible power supply (UPS) capable of accurately determining the amount of surplus power in a power storage device. [Solution] Each controller 7 of at least one uninterruptible power supply 100 controls to one of a plurality of operating modes, including a first operating mode (normal mode) and a second operating mode, in accordance with control commands from a monitoring device 200 that monitors at least one uninterruptible power supply 100. Each controller 7 of at least one uninterruptible power supply 100 transmits to the monitoring device 200 information indicating the surplus amount of power stored in the energy storage device 51 that can be supplied to the load 8 or grid power supply 1 in the second operating mode (peak cut mode or regenerative mode).

Description

Technical Field

[0001] The present invention relates to an uninterruptible power supply system.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2007-60796 (Patent Document 1) discloses a power buffer device system including an uninterruptible power supply unit. The power buffer device system further includes a load leveling unit that charges the overnight power into a sustainable power buffer, supplies the charged power to normal loads and emergency loads during the morning hours, and feeds the excess power back to the commercial power system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the power buffer device system disclosed in Patent Document 1, in the morning hours, when a power outage occurs during power supply from a power storage device such as a sustainable power buffer, there is a risk that the amount of power that should be supplied by the power storage device during the power outage (the compensation for the power that the uninterruptible power supply device should ensure) is insufficient.

[0005] When supplying power from the power storage device, it is necessary to supply power within the range of the surplus amount of the power storage device excluding the compensation for the power required during a power outage among the power stored in the power storage device. If this surplus amount can be accurately grasped, a monitoring device that monitors the uninterruptible power supply device at a higher level can accurately issue commands (peak cut commands for supplying to loads, regeneration commands for supplying to the system power supply) to supply the power stored in the power storage device to loads or the system power supply within the range of the surplus amount.

[0006] Therefore, the primary purpose of this disclosure is to provide an uninterruptible power supply system that can accurately grasp the surplus power amount of an energy storage device. [Means for solving the problem]

[0007] According to one aspect of the present invention, an uninterruptible power supply system is a system comprising at least one uninterruptible power supply unit. Each of the at least one uninterruptible power supply units comprises a converter, a power storage unit, an inverter, and a control device. The converter converts alternating current power supplied from the grid power supply into direct current power. The power storage unit stores the direct current power generated by the converter. The inverter is configured to convert the direct current power from the converter and the direct current power stored in the power storage unit into alternating current power that can be supplied to a load. The control device controls the converter, the inverter, and the power storage unit. The control device of each of the at least one uninterruptible power supply units controls to one of a plurality of operating modes, including a first operating mode in which power supplied from the grid power supply is supplied to the load without supplying power stored in the power storage unit, and a second operating mode in which power stored in the power storage unit is supplied to the load or the grid power supply, in accordance with control commands from a monitoring device that monitors the at least one uninterruptible power supply unit. Each control unit of at least one uninterruptible power supply transmits information to the monitoring unit indicating the surplus amount of power stored in the energy storage unit that can be supplied to the load or grid power in the second operating mode.

[0008] Preferably, each control unit of at least one uninterruptible power supply calculates the surplus amount using the capacity that can be stored in the energy storage device and the storage rate.

[0009] Preferably, each control unit of at least one uninterruptible power supply calculates the surplus amount using a compensation time determined to allow power supply from the energy storage device to the load to continue in the event of a power outage from the grid.

[0010] Preferably, the uninterruptible power supply system further includes a monitoring device. The monitoring device uses information on the surplus amount received from each of the control devices of at least one uninterruptible power supply to determine that control to the second operating mode is possible, and transmits a control command to each of the control devices of at least one uninterruptible power supply to the control device of at least one uninterruptible power supply. Each of the control devices of at least one uninterruptible power supply controls itself to the second operating mode when it receives a control command to the second operating mode from the monitoring device.

[0011] Preferably, each control unit of at least one uninterruptible power supply unit controls the supply of power stored in the energy storage unit and power supplied from the grid power supply to the load in the second operating mode. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an uninterruptible power supply system that can accurately grasp the surplus power amount of an energy storage device. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram schematically shows the configuration of an uninterruptible power supply system according to the first embodiment. [Figure 2] Figure 1 is a schematic circuit block diagram showing the configuration of the uninterruptible power supply (UPS). [Figure 3] Figure 2 is a diagram illustrating signal transmission in the energy storage device and controller shown. [Figure 4] This is a diagram illustrating the method for calculating the surplus amount. [Figure 5] This is a conceptual diagram illustrating the power supply path from the grid power source to the load in normal mode. [Figure 6] This is a conceptual diagram illustrating the power supply path from the grid power source and energy storage device to the load in peak-cut mode. [Figure 7] This is a conceptual diagram illustrating the power supply path from the energy storage device to the grid power supply in regenerative mode. [Figure 8]This is a flowchart showing the process for switching the operation mode in an uninterruptible power supply system. [Figure 9] This is a diagram schematically showing the configuration of the uninterruptible power supply system according to the second embodiment. [Figure 10] This is a flowchart showing the process for switching the operation mode in an uninterruptible power supply system.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figures, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0015] [First Embodiment] FIG. 1 is a diagram schematically showing the configuration of an uninterruptible power supply system 300 according to the first embodiment. The uninterruptible power supply system 300 is a system including at least one uninterruptible power supply device 100 and a monitoring device 200 that monitors and gives commands to the at least one uninterruptible power supply device 100. In the first embodiment, the uninterruptible power supply system 300 includes one uninterruptible power supply device 100.

[0016] The utility power supply 1 supplies AC power to the uninterruptible power supply device 100. The uninterruptible power supply device 100 supplies AC power to the load 8. The load 8 is not particularly limited as long as it is an electrical device that consumes AC power.

[0017] The controller 201 included in the monitoring device 2 controls the monitoring device 200. The monitoring device obtains, from the uninterruptible power supply device 100, measurement information measured by the uninterruptible power supply device 100 and information on the surplus amount described later. Based on the obtained measurement information and information on the surplus amount, the monitoring device generates a regeneration command or a peak cut command described later and transmits it to the uninterruptible power supply device 100. The uninterruptible power supply device 100 operates by switching the operation mode according to these commands.

[0018] <000009X>FIG. 2 is a circuit block diagram schematically showing the configuration of the uninterruptible power supply device 100 shown in FIG. 1. FIG. 3 is a diagram for explaining signal transmission in the power storage device 51 and the controller 7 shown in FIG. 2.

[0019] The uninterruptible power supply device 100 is assumed to include one uninterruptible power supply module 101 and a controller (control unit) 7. The controller 7 controls the uninterruptible power supply module 101. Note that the uninterruptible power supply device 100 may include a plurality of uninterruptible power supply modules. In this case, the uninterruptible power supply device 100 includes the uninterruptible power supply modules 101 connected in parallel and the controller 7. The controller 7 controls each of the plurality of uninterruptible power supply modules 101.

[0020] The uninterruptible power supply module 101 includes a converter 21, an inverter 31, a buck-boost chopper circuit 41, and a power storage device (battery) 51. The power storage device 51 includes a lithium-ion battery such as SCiB (registered trademark).

[0021] The power storage device 51 stores the DC power generated by the converter 21. The power storage device 51 includes a plurality of cells 5 connected in series and a BMU (Battery Management Unit) 61. In addition, although not shown in any of them, the power storage device 51 is provided with an ammeter for detecting the charge / discharge current I, a voltmeter for detecting the voltage V of each cell, and a thermometer for detecting the temperature T of each cell. The BMU 61 monitors the abnormality of the power storage device 51 based on the charge / discharge current I, the voltage V, and the temperature T, and calculates the charge rate (battery charge rate) of the power storage device 51. The BMU 61 outputs a signal SOC1 including the charge rate of the power storage device 51 to the controller 7. Note that, as a method for calculating the charge rate, various known methods such as the current integration method can be adopted.

[0022] The controller 7 controls the converter 21, the inverter 31, the step-up / step-down chopper circuit 41, and the energy storage device 51. The controller 7 includes a timer 71. Based on the time measured by the timer 71 and the signal SOC1 received from the BMU 61, the controller 7 outputs control signals CTRL21, CTRL31, and CTRL41. Each of the control signals CTRL21, CTRL31, and CTRL41 is a signal containing, for example, a current command value or a voltage command value, or a stop signal. The controller 7 may also obtain the time from outside the uninterruptible power supply 100.

[0023] The converter 21 converts AC power from the grid power supply 1 into DC power based on the control signal CTRL 21 from the controller 7. This DC power is supplied to the inverter 31 and the step-up / step-down chopper circuit 41.

[0024] The converter 21 has a function to limit the power supplied to it from the grid power supply 1. The value of the limited power is given to the converter 21 by the control signal CTRL21 from the controller 7.

[0025] Based on the control signal CTRL41 from the controller 7, the buck-boost chopper circuit 41 steps down the DC power generated by the converter 21 when the energy storage device 51 is being charged and supplies that DC power to the energy storage device 51. On the other hand, when the energy storage device 51 is being discharged, the buck-boost chopper circuit 41 steps up the DC voltage discharged from the energy storage device 51 and supplies that DC power to the inverter 31. The buck-boost chopper circuit 41 can also step up the DC voltage discharged from the energy storage device 51 when the energy storage device 51 is being discharged and supply that DC power to the converter 21 (regenerative mode, described later). Alternatively, if the energy storage device 51 is not being charged or discharged, the buck-boost chopper circuit 41 stops based on the control signal CTRL41.

[0026] The inverter 31 is configured to convert the DC power from the converter 21 and the DC power stored in the energy storage device 51 into AC power and supply it to the load 8. Based on the control signal CTRL 31 from the controller 7, the inverter 31 converts the DC power from the converter 21 and the step-up / step-down chopper circuit 41 into AC power and supplies that AC power to the load 8.

[0027] Figure 4 is a diagram illustrating the method for calculating the surplus amount. The surplus amount represents the amount of power stored in the energy storage device 51 that can be supplied to the load 8 or grid power supply 1 in the second operating mode (peak cut mode or regenerative mode) described later.

[0028] The surplus amount is calculated using the following formula. In the following formula, "battery" refers to the energy storage device (battery) 51. Surplus amount [Ah] = Battery remaining amount [Ah] - Compensation amount [Ah]. Battery remaining amount indicates the current remaining amount of the energy storage device 51. Compensation amount indicates the amount that the energy storage device 51 compensates for the power supply to the load 8 when the power supply from the grid power source 1 stops (the compensation amount that needs to be secured as an uninterruptible power supply 100). The surplus amount is the amount obtained by subtracting the compensation amount that the energy storage device 51 should compensate from the battery remaining amount. The uninterruptible power supply 100 can supply power to the load 8 or the grid power source 1 in the peak cut mode or regenerative mode described later, up to the amount of the surplus amount.

[0029] Battery charge [Ah] = Battery capacity [Ah] × Battery charge rate [%]. Also, compensation amount [Ah] = ((Load voltage [V] × Load current [A] × Load power factor [Φ] / Device efficiency [%]) / Battery voltage [V]) × (Compensation time [min] / 60 [min]). In the above formula, "load" refers to load 8.

[0030] The compensation time is the period of time that allows power to continue to be supplied from the energy storage device 51 to the load 8 if the power supply from the grid power source 1 is interrupted. In this embodiment, the compensation time is set to 10 minutes. In this case, if the power supply from the grid power source 1 is interrupted, the uninterruptible power supply 100 will compensate for the power supply to the load 8 for the following 10 minutes.

[0031] In this way, the controller 7 calculates the surplus amount using the capacity that can be stored in the energy storage device 51 (battery capacity), the storage rate (battery charge rate), and the compensation time.

[0032] For example, suppose the battery voltage of the energy storage device 51 is 500V, the battery capacity is 400Ah, the battery charge level is 100%, the load voltage of load 8 is 400V, the load current is 200A, the compensation time is 10 minutes, the load power factor is 1, and the device efficiency is 100%. In this case, the remaining battery capacity is 400Ah, and the compensation amount is (400 × 200 × 1 / 1) / (500) × (10 / 60) = 26.7Ah. The surplus amount is 400 - 26.7 = 373.3Ah.

[0033] Figures 5 to 7 illustrate the control of the components of the uninterruptible power supply 100 in each operating mode. The controller 7 of the uninterruptible power supply 100 controls it to one of several operating modes according to control commands from the monitoring device 200. The multiple operating modes include a first operating mode and a second operating mode.

[0034] The first operating mode is also called the normal mode. The first operating mode (normal mode) is a mode in which power supplied from the grid power supply 1 is supplied to the load 8 without supplying power stored in the energy storage device 51. The second operating mode is a mode in which power stored in the energy storage device 51 is supplied to the load 8 or the grid power supply 1. The second operating mode is the peak cut mode or regenerative mode, which will be described below.

[0035] In normal mode or pick-cut mode, the power supply from grid power 1 can be limited by specifying a power value. Switching between operating modes is controlled by the monitoring device 200. The power supply in each operating mode is described below.

[0036] Figure 5 is a conceptual diagram illustrating the power supply path from grid power source 1 to load 8 in normal mode. In normal mode, power is supplied from grid power source 1 to load 8. Grid power source 1 can also supply power to the energy storage device 51. The controller 7 can also control the step-up / step-down chopper circuit 41 to limit the power supply to the energy storage device 51.

[0037] Figure 6 is a conceptual diagram illustrating the power supply path from the grid power source 1 and the energy storage device 51 to the load 8 in peak cut mode. In peak cut mode, which is one of the second operating modes, the controller 7 controls the supply of power stored in the energy storage device 51 and power supplied from the grid power source 1 to the load 8.

[0038] In peak-cut mode, the controller 7 controls the step-up / step-down chopper circuit 41 to increase its voltage using the control signal CTRL 41, thereby supplying power stored in the energy storage device 51 to the load 8. On the other hand, the controller 7 outputs a control signal CTRL 21 to the converter 21, instructing it to limit the power supplied. As a result, the converter 21 limits the power supplied from the grid power supply 1 to the converter 21 based on the control signal CTRL 21. With power supplied from both the energy storage device 51 and the grid power supply 1, sufficient power can be supplied to the load 8. In this way, in peak-cut mode, the power supplied from the grid power supply 1 can be reduced by utilizing the power stored in the energy storage device 51.

[0039] By controlling the system to peak-cut mode, the power supplied from grid power source 1 can be reduced during daytime hours when electricity demand is high. For example, by activating peak-cut mode and controlling the power supply from grid power source 1 so that it does not exceed the contracted power, electricity costs can be reduced.

[0040] However, if the peak cut mode consumes all of the surplus power of the energy storage device 51, it is necessary to terminate the control to peak cut mode and return to normal mode. Since the monitoring device 200 is aware of the surplus power information of the uninterruptible power supply 100, it can accurately control the system to peak cut mode to ensure that the energy storage device 51 does not consume more power than the surplus power while securing the compensation amount for the energy storage device 51.

[0041] Figure 7 is a conceptual diagram illustrating the power supply path from the energy storage device 51 to the grid power supply 1 in regenerative mode. In this embodiment, it is possible to supply power from the energy storage device 51 to the grid power supply 1. In regenerative mode, the controller 7 controls the supply of power from the energy storage device 51 to the grid power supply 1 using a control signal CTRL41 for the step-up / step-down chopper circuit 41 and a control signal CTRL21 for the converter 21.

[0042] Since the monitoring device 200 is aware of the surplus amount in the uninterruptible power supply 100, it can control the power consumption of the energy storage device 51 to prevent it from consuming more power than the surplus amount, even in regenerative mode, while ensuring that the compensation amount for the energy storage device 51 is secured.

[0043] Figure 8 is a flowchart showing the process for switching the operating mode in the uninterruptible power supply system 300. This process is initiated periodically. Hereafter, the steps will also be simply referred to as "S".

[0044] When this process begins, the uninterruptible power supply (UPS) 100 calculates the surplus amount in S10 using the method described with reference to Figure 4. In S11, the UPS 100 transmits the calculated surplus amount information, along with measurement information from various sensors equipped in the UPS 100, to the monitoring device 200. The measurement information may include the various values ​​used in calculating the surplus amount.

[0045] In S21, the monitoring device 200 receives measurement information and surplus power information transmitted by the uninterruptible power supply 100. In S22, the monitoring device 200 generates a control command for the uninterruptible power supply 100 based on the received measurement information and surplus amount information.

[0046] Specifically, the monitoring device 200 uses the measurement information and surplus amount information received from the uninterruptible power supply 100 to determine that control to the second operating mode (peak cut command or regeneration command) is possible, and then transmits a control command to the uninterruptible power supply 100 to switch to the second operating mode.

[0047] The monitoring device 200 operates the uninterruptible power supply 100 in peak cut mode or regenerative mode using the surplus energy in the energy storage device 51 (surplus energy > 0). When the surplus energy is no longer available (surplus energy = 0), the monitoring device 200 stops controlling the system to peak cut mode or regenerative mode and returns it to normal mode.

[0048] In S23, the monitoring device 200 transmits the generated control command to the monitoring device 200 and terminates its processing. In S12, the uninterruptible power supply 100 receives the control command from the monitoring device 200.

[0049] The uninterruptible power supply (UPS) 100 controls itself to the second operating mode when it receives a control command (peak cut command or regeneration command) from the monitoring device 200. Specifically, if the received control command is a peak cut command (YES in S13), the UPS 100 controls itself to the peak cut mode (S14) and terminates this process. On the other hand, if the received control command is not a peak cut command (NO in S13), the UPS 100 proceeds to S15.

[0050] If the received control command is a regenerative command (YES in S15), the uninterruptible power supply 100 controls the system to regenerative mode (S16) and terminates this process. On the other hand, if the received control command is not a regenerative command (NO in S15), the uninterruptible power supply 100 proceeds to S17. In S17, the uninterruptible power supply 100 controls the system to normal mode and terminates this process.

[0051] The monitoring device 200 may determine the control time to switch to peak cut mode or regenerative mode based on the received surplus amount. In this case, the uninterruptible power supply 100 should be controlled to peak cut mode or regenerative mode for the determined control time based on the command from the monitoring device 200.

[0052] As described above, in this embodiment, the uninterruptible power supply system 300 is a system comprising at least one uninterruptible power supply unit 100. Each of the at least one uninterruptible power supply unit 100 comprises a converter 21, a power storage device 51, an inverter 31, and a controller 7 which is a control device. The converter 21 converts AC power supplied from the grid power supply 1 into DC power. The power storage device 51 stores the DC power generated by the converter 21. The inverter 31 is configured to convert the DC power from the converter 21 and the DC power stored in the power storage device 51 into AC power that can be supplied to the load 8. The controller 7 controls the converter 21, the inverter 31, and the power storage device 51. Each controller 7 of at least one uninterruptible power supply (UPS) 100 controls the UPS to one of several operating modes, including a first operating mode (normal mode) in which power supplied from the grid power supply 1 is supplied to the load 8 without supplying power stored in the energy storage device 51, and a second operating mode in which power stored in the energy storage device 51 is supplied to the load 8 or the grid power supply 1, in accordance with control commands from a monitoring device 200 that monitors at least one UPS 100. Each controller 7 of at least one UPS 100 transmits to the monitoring device 200 information indicating the surplus amount of power stored in the energy storage device 51 that can be supplied to the load 8 or the grid power supply 1 in the second operating mode (peak cut mode or regenerative mode).

[0053] Conventional uninterruptible power supplies (UPS) estimated surplus power based on input / output information (system power side and load side) and load information, without using the UPS's internal information, and issued peak cut commands, etc. In this case, because information acquired outside the UPS was used, measurement and estimation errors were large, and there were problems with the accuracy of the estimated surplus power. In this embodiment, each controller 7 of the multiple UPS units 100 transmits surplus power information held internally by the UPS unit 100 to the monitoring device 200. This allows the monitoring device 200 to be notified of more accurate information. Furthermore, compared to a configuration in which a sensor device is separately installed outside the UPS unit 100 and the input / output information to the UPS unit 100 is detected by the sensor device and transmitted to the monitoring device 200, it is possible to reduce the installation cost of the sensor device. Thus, in the UPS system 300 of this embodiment, the monitoring device 200 can accurately grasp the surplus power amount of the energy storage device 51.

[0054] Each controller 7 of at least one uninterruptible power supply (UPS) 100 calculates the surplus amount using the storage capacity and storage rate of the energy storage device 51. By calculating the surplus amount using the storage rate and storage capacity of the energy storage device 51, which are internal information of the UPS 100, the monitoring device 200 can grasp the amount of surplus power with greater accuracy.

[0055] Each controller 7 of at least one uninterruptible power supply (UPS) 100 calculates a surplus using a compensation time that is set to ensure that power supply from the energy storage device 51 to the load 8 can continue in the event of a power outage from the grid power supply 1. By calculating the surplus using this compensation time, the energy storage device 51 can reliably secure the amount of power it should compensate for during a power outage, and then execute the second operating mode (peak cut mode or regenerative mode). This ensures that the second operating mode does not overuse the power of the energy storage device 51, and that power can be utilized to the maximum extent possible.

[0056] The uninterruptible power supply system 300 further includes a monitoring device 200. The monitoring device 200, using information on the surplus amount received from each controller 7 of at least one uninterruptible power supply 100, determines that control to the second operating mode is possible and transmits a control command to each controller 7 of at least one uninterruptible power supply 100 to the controller 7 of the at least one uninterruptible power supply 100. Each controller 7 of at least one uninterruptible power supply 100 controls itself to the second operating mode when it receives a control command to the second operating mode from the monitoring device 200. As a result, the monitoring device 200 can receive accurate information on the surplus amount held internally by the uninterruptible power supply 100, and the uninterruptible power supply 100 can control itself to the second operating mode based on appropriate instructions from the monitoring device 200.

[0057] Each controller 7 of at least one uninterruptible power supply 100 controls the supply of power stored in the energy storage device 51 and power supplied from the grid power supply 1 to the load 8 in the second operating mode (peak cut mode). This ensures that the energy storage device 51 has secured the amount of power to be compensated for during a power outage, and that the peak cut mode is executed appropriately.

[0058] [Second Embodiment] Figure 9 is a schematic diagram showing the configuration of the uninterruptible power supply system 300 according to the second embodiment. In the second embodiment, the uninterruptible power supply system 300 is a system comprising two uninterruptible power supply units 100 connected in parallel. Each of the two uninterruptible power supply units 100 comprises a converter 21, an energy storage device 51, an inverter 31, and a controller 7 which is a control device (see Figure 2).

[0059] The monitoring device 200 monitors the two uninterruptible power supplies 100. Each controller 7 of the two uninterruptible power supplies 100 controls itself to one of several operating modes, including a first operating mode (normal mode) and a second operating mode (peak cut mode or regenerative mode), according to control commands from the monitoring device 200.

[0060] Each controller 7 of the two uninterruptible power supplies 100 transmits surplus information to the monitoring device 200. Each controller 7 of the two uninterruptible power supplies 100 calculates the surplus amount. The monitoring device 200, using the measurement information and surplus amount information received from each controller 7 of the two uninterruptible power supplies 100, determines that control to the second operating mode is possible and transmits a control command to each controller 7 of the two uninterruptible power supplies 100 to switch to the second operating mode. Each controller 7 of the two uninterruptible power supplies 100 switches to the second operating mode when it receives a control command to the second operating mode from the monitoring device 200.

[0061] Figure 10 is a flowchart showing the process for switching the operating mode in the uninterruptible power supply system 300. The process is almost the same as the flowchart described in Figure 8, except that there are now two uninterruptible power supplies 100. The process for "Uninterruptible Power Supply 1" refers to the process of one of the uninterruptible power supplies 100 shown in Figure 9, and the process for "Uninterruptible Power Supply 2" refers to the process of the other uninterruptible power supply 100 shown in Figure 9.

[0062] When this process begins, each of the two uninterruptible power supply units 100 calculates the surplus amount and transmits the surplus amount information along with the measurement information to the monitoring device 200 (S10, S11, S30, S31).

[0063] In S21, the monitoring device 200 receives measurement information and surplus power information transmitted by the two uninterruptible power supplies 100. Based on the received measurement information and surplus power information, the monitoring device 200 generates a control command for each of the two uninterruptible power supplies 100 and transmits the generated control command to each of the uninterruptible power supplies 100 (S22, S23).

[0064] Each of the two uninterruptible power supplies 100 receives a control command and controls itself to peak cut mode if it receives a peak cut command, to regenerative mode if it receives a regenerative command, and to normal mode otherwise (S12-S17, S32-S37).

[0065] By configuring the system as described above, the monitoring device 200 can accurately determine the amount of surplus power in the energy storage device 51, even in an uninterruptible power supply system 300 equipped with two uninterruptible power supply units 100.

[0066] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0067] 1 power supply, 200 monitoring devices, 201 controllers, 21 converters, 300 uninterruptible power supply systems, 31 inverters, 41 buck-boost chopper circuits, 5 cells, 51 energy storage devices, 61 BMUs, 7 controllers, 8 loads, 100 uninterruptible power supplies, 101 uninterruptible power supply modules.

Claims

1. An uninterruptible power supply system comprising at least one uninterruptible power supply unit, Each of the at least one uninterruptible power supply units is: A converter that converts AC power supplied from the grid into DC power, A power storage device that stores DC power generated by the converter, An inverter configured to convert the DC power from the converter and the DC power stored in the energy storage device into AC power and supply it to the load, The system comprises the converter, the inverter, and a control device for controlling the energy storage device, Each of the control devices of the at least one uninterruptible power supply is In accordance with a control command from a monitoring device that monitors the at least one uninterruptible power supply, the device is controlled to one of a plurality of operating modes, including a first operating mode in which power supplied from the grid power supply is supplied to the load without supplying power stored in the energy storage device, and a second operating mode in which power stored in the energy storage device is supplied to the load or the grid power supply. An uninterruptible power supply system that transmits to the monitoring device information regarding the amount of surplus power stored in the energy storage device that can be supplied to the load or the grid power supply in the second operating mode.

2. The uninterruptible power supply system according to claim 1, wherein the control device of each of the at least one uninterruptible power supply devices calculates the surplus amount using the capacity that can be stored in the energy storage device and the energy storage rate of the energy storage device.

3. The uninterruptible power supply system according to claim 2, wherein the control device of each of the at least one uninterruptible power supply devices calculates the surplus amount using a compensation time determined so that power supply from the energy storage device to the load can continue when the power supply from the grid power supply is interrupted.

4. The monitoring device further comprises, The monitoring device, using the information on the surplus amount received from each of the control devices of the at least one uninterruptible power supply, determines that control to the second operating mode is possible, and transmits a control command to the second operating mode to each of the control devices of the at least one uninterruptible power supply. The uninterruptible power supply system according to any one of claims 1 to 3, wherein each of the control devices of the at least one uninterruptible power supply unit controls to the second operating mode when it receives a control command to the second operating mode from the monitoring device.

5. The uninterruptible power supply system according to claim 4, wherein each of the control devices of the at least one uninterruptible power supply device controls the supply of power stored in the energy storage device and power supplied from the grid power supply to the load in the second operating mode.

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