Uninterruptible power supply

Abstract

To enhance the reliability of load power supply in an uninterruptible power supply equipped with an auto-retransfer function.SOLUTION: When an overload condition is resolved, if an inverter output voltage is not synchronized with a bypass input voltage, a control unit executes an operating mode selected by a selection unit. If a first operating mode is selected, when a time during which the bypass input voltage and inverter output voltage are asynchronous reaches a first time period, an alarm indicating that a bypass power supply mode is continuing is output. When a second operating mode is selected, upon reaching a second time period during which the bypass input voltage and inverter output voltage remain asynchronous, a switch is turned off, switching to an inverter power supply mode. When a third operating mode is selected, upon reaching a third time period during which the bypass input voltage and inverter output voltage remain asynchronous, an uninterruptible power supply unit's operation is stopped.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to an uninterruptible power supply with an automatic transfer function. [Background technology]

[0002] For example, Japanese Patent Application Laid-Open No. 2004-15919 (Patent Document 1) discloses an uninterruptible power supply device that includes an inverter power supply circuit for supplying the output of an inverter to a load, and a bypass power supply circuit consisting of a bypass power supply switch including a parallel circuit of a thyristor switch and an AC switch.

[0003] When the AC power supply is normal, power is supplied to the load by the inverter power supply circuit. When the current detection means of the inverter power supply circuit detects an overload state, it immediately turns on the thyristor switch of the bypass power supply switch, turns off the output switch of the inverter power supply circuit, turns on the AC switch, and turns off the thyristor switch, thereby switching from the inverter power supply circuit to the bypass power supply circuit without momentary interruption, and power is supplied to the load from the bypass power supply circuit.

[0004] When the overload of the inverter power supply circuit is avoided, the synchronization state between the output voltage of the inverter power supply circuit and the bypass power supply circuit is confirmed, and the output switch of the inverter power supply circuit is turned on and the AC switch of the bypass power supply switch is turned off, thereby restoring power supply from the inverter power supply circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-15919 Summary of the Invention [Problem to be solved by the invention]

[0006] The function described above, which automatically switches from the inverter power supply circuit to the bypass power supply circuit when an overload occurs while power is being supplied from the inverter power supply circuit and then returns to power supply from the inverter power supply circuit after the overload is resolved, is also called the "auto-transfer function." The auto-transfer function protects the inverter from overcurrent.

[0007] However, with this auto-transfer function, there are cases where, for some reason, the output voltage of the inverter power supply circuit and the bypass power supply circuit are not synchronized after the inverter 10 is restarted while power is being supplied by the bypass power supply circuit. In such cases, even though the overload has been resolved, the uninterruptible power supply continues to supply power from the bypass power supply circuit until the output voltage of the inverter power supply circuit and the bypass power supply circuit are synchronized again.

[0008] However, if a power outage or other abnormality occurs in the AC power supply while power is being supplied through this bypass power supply circuit, the uninterruptible power supply will be unable to supply power to the load, and as a result, the load will no longer be able to operate. However, with conventional uninterruptible power supplies, as long as the load is operating normally, the user of the uninterruptible power supply is unable to grasp this situation. This creates the problem of being unable to take appropriate measures to maintain the reliability of the power supply to the load.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to improve the reliability of load power supply of an uninterruptible power supply device with an automatic transfer function. [Means for solving the problem]

[0010] An uninterruptible power supply according to the present disclosure includes a converter that converts AC power supplied from an AC power source into DC power, an inverter that converts the DC power supplied from the converter into AC power and supplies the converted AC power to a load, a switch having a first terminal receiving AC power from the AC power source and a second terminal connected to the load, a current detector that detects an output current of the uninterruptible power supply, and a control device that controls the inverter and the switch. When a detected value of the current detector exceeds an allowable current range in an inverter power supply mode in which AC power generated by the inverter is supplied to the load, the control device stops operation of the inverter and turns on the switch to switch to a bypass power supply mode in which AC power from the AC power source is supplied to the load. The control device is further configured to restart the inverter in the bypass power supply mode and control the inverter to synchronize an AC output voltage output from the inverter with an AC input voltage input to the switch, and when the detected value of the current detector returns to the allowable current range, turn off the switch in response to the AC output voltage being synchronized with the AC input voltage.

[0011] The uninterruptible power supply further includes a selection unit for selecting one of first to third operation modes. When the detection value of the current detector returns to within the allowable current range and the AC output voltage is not synchronized with the AC input voltage, the control device is further configured to execute the operation mode selected by the selection unit. If the first operation mode is selected by the selection unit, a warning indicating that the bypass power supply mode is continuing is output when the time during which the AC input voltage and the AC output voltage are out of sync reaches a first time. If the second operation mode is selected by the selection unit, a switch is turned off and the control device switches to the inverter power supply mode when the time during which the AC input voltage and the AC output voltage are out of sync reaches a second time. If the third operation mode is selected by the selection unit, the control device switches to power supply by the standby uninterruptible power supply and stops operation of the uninterruptible power supply when the time during which the AC input voltage and the AC output voltage are out of sync reaches a third time. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to improve the reliability of load power supply of an uninterruptible power supply device with an automatic transfer function. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a circuit block diagram showing a configuration of an uninterruptible power supply according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram illustrating an example of a hardware configuration of a control device. [Figure 3] 10 is a time chart for explaining an auto-retransfer function. [Figure 4] 4 is a time chart for explaining a first operation mode. [Figure 5] 10 is a time chart for explaining a second operation mode. [Figure 6] FIG. 10 is a block diagram showing a configuration example of an uninterruptible power supply system to which a third operation mode is applied. [Figure 7] 10 is a time chart for explaining a third operation mode. [Figure 8] 3 is a flowchart showing the operation of the uninterruptible power supply. [Figure 9] 3 is a flowchart showing the operation of the uninterruptible power supply. DETAILED DESCRIPTION OF THE INVENTION

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

[0015] <Configuration of uninterruptible power supply> Figure 1 is a circuit block diagram showing the configuration of an uninterruptible power supply according to an embodiment of the present disclosure. Uninterruptible power supply 1 first converts three-phase AC power from a commercial AC power supply 21 into DC power, and then converts the DC power back into three-phase AC power to supply to a load 24. To simplify the drawing and explanation, Figure 1 shows only a portion of the circuit corresponding to one phase (e.g., U phase) of the three phases (U phase, V phase, W phase).

[0016] 1, the uninterruptible power supply 1 includes an AC input terminal T1, a bypass input terminal T2, a battery terminal T3, and an AC output terminal T4. The AC input terminal T1 receives AC power at a commercial frequency from a commercial AC power supply 21. The bypass input terminal T2 receives AC power at a commercial frequency from a bypass AC power supply 22. The bypass AC power supply 22 may be a commercial AC power supply or a generator.

[0017] Battery terminal T3 is connected to battery 23, which corresponds to an example of a "power storage device" that stores DC power. An electric double layer capacitor or a flywheel may be connected instead of battery 23. AC output terminal T4 is connected to load 24. Load 24 is driven by AC power supplied from uninterruptible power supply 1. In the example of FIG. 1, AC output terminal T4 is connected to multiple loads 24, but the number of loads 24 may be one or more.

[0018] The uninterruptible power supply 1 further includes switches 2, 8, 14, and 16, current detectors 3 and 11, capacitors 4, 9, and 13, reactors 5 and 12, a converter 6, a bidirectional chopper 7, an inverter 10, a semiconductor switch 15, an operation unit 17, and a control device 18.

[0019] The switch 2 and the reactor 5 are connected in series between the AC input terminal T1 and the AC node of the converter 6. The switch 2 is controlled by a control device 18. When AC power is being supplied normally from the commercial AC power supply 21 (when the commercial AC power supply 21 is operating normally), the switch 2 is turned on. When AC power is no longer being supplied normally from the commercial AC power supply 21 (when the commercial AC power supply 21 experiences a power outage), the switch 2 is turned off. The current detector 3 detects the AC input current Ii flowing between the commercial AC power supply 21 and the converter 6, and provides a signal Iif indicating the detected value to the control device 18.

[0020] The instantaneous value of the AC input voltage Vi appearing at a node N1 between the switch 2 and the reactor 5 is detected by the control device 18. Based on the detected value of the AC input voltage Vi, the control device 18 determines whether or not a power outage has occurred in the commercial AC power supply 21. The control device 18 also controls the converter 6 and the like in synchronization with the AC input voltage Vi.

[0021] Capacitor 4 is connected to node N1. Capacitor 4 and reactor 5 form a low-pass filter that passes commercial frequency AC power from commercial AC power supply 21 to converter 6 and prevents a switching frequency signal generated in converter 6 from passing to commercial AC power supply 21.

[0022] The converter 6 is controlled by the control device 18, and when the commercial AC power supply 21 is normal, converts AC power into DC power and outputs it to the DC line L1. The output voltage of the converter 6 can be controlled to a desired value.

[0023] In the event of a power outage in the commercial AC power supply 21, the operation of the converter 6 is stopped. The capacitor 9 is connected to the DC line L1 and smooths the voltage of the DC line L1. The instantaneous value of the DC voltage VDC appearing on the DC line L1 is detected by the control device 18. When the commercial AC power supply 21 is functioning normally, the control device 18 controls the converter 6 so that the DC voltage VDC on the DC line L1 becomes equal to the reference DC voltage VDCr.

[0024] The DC line L1 is connected to a high-voltage side node of a bidirectional chopper 7, and the low-voltage side node of the bidirectional chopper 7 is connected to a battery terminal T3 via a switch 8. The switch 8 is turned on when the uninterruptible power supply 1 is in use, and turned off, for example, during maintenance of the uninterruptible power supply 1 and the battery 23. The instantaneous value of the voltage VB across the terminals of the battery 23 that appears at the battery terminal T3 is detected by a control device 18.

[0025] The bidirectional chopper 7 is controlled by the control device 18, and when the commercial AC power supply 21 is normal, the bidirectional chopper 7 stores the DC power generated by the converter 6 in the battery 23. When the commercial AC power supply 21 experiences a power outage, the bidirectional chopper 7 supplies the DC power of the battery 23 to the inverter 10 via the DC line L1. The instantaneous value of the terminal voltage VB of the battery 23 appearing at the battery terminal T3 is detected by the control device 18.

[0026] The control device 18 controls the bidirectional chopper 7 so that the battery voltage VB becomes equal to the reference DC voltage VBr when the commercial AC power supply 21 is normal, and controls the bidirectional chopper 7 so that the DC voltage VDC of the DC line L1 becomes equal to the reference DC voltage VDCr when the commercial AC power supply 21 is in a power outage. The DC line L1 is connected to a DC node of the inverter 10.

[0027] The inverter 10 is controlled by a control device 18. The inverter 10 converts DC power supplied from the converter 6 or the bidirectional chopper 7 via a DC line L1 into AC power of a commercial frequency and outputs the AC power to an output node 10a.

[0028] That is, when the commercial AC power supply 21 is operating normally, the inverter 10 converts DC power supplied from the converter 6 via the DC line L1 into AC power, and when the commercial AC power supply 21 experiences a power outage, it converts DC power supplied from the battery 23 via the bidirectional chopper 7 into AC power. The output voltage of the inverter 10 can be controlled to a desired value.

[0029] An output node 10a of the inverter 10 is connected to a first terminal (node ​​N2) of a switch 14 via a reactor 12, and a second terminal of the switch 14 is connected to an AC output terminal T4. A capacitor 13 is connected to the node N2. The reactor 12 and the capacitor 13 form a low-pass filter that passes AC power of the commercial frequency generated by the inverter 10 to the AC output terminal T4 and prevents a signal of the switching frequency generated by the inverter 10 from passing to the AC output terminal T4.

[0030] The switch 14 is controlled by the control device 18, and is turned on in an inverter power supply mode in which AC power generated by the inverter 10 is supplied to the load 24. If the inverter 10 fails or an overload occurs in the inverter power supply mode, the switch 14 is turned off. Furthermore, the switch 14 is turned off in a bypass power supply mode in which AC power from the bypass AC power supply 22 is supplied to the load 24. The switch 14 corresponds to one example of a "first switch."

[0031] The instantaneous value of the AC output voltage Vo appearing at node N2 is detected by the control device 18. The current detector 11 detects the current Io flowing between the uninterruptible power supply 1 and the load 24, and provides the control device 18 with a signal Iof indicating the detected value. The output current Io of the uninterruptible power supply 1 corresponds to the load current. The control device 18 controls the inverter 10 so that the AC output voltage Vo becomes a sinusoidal reference AC voltage Vor.

[0032] The semiconductor switch 15 includes a pair of thyristors connected in anti-parallel to each other and is connected between the bypass input terminal T2 and the AC output terminal T4. The semiconductor switch 15 is controlled by the control device 18 and is turned off in the inverter power supply mode. In the inverter power supply mode, if the inverter 10 fails or an overload occurs, the semiconductor switch 15 is instantly turned on for a predetermined time. The reason for turning on the semiconductor switch 15 for only a predetermined time is to prevent the semiconductor switch 15 from being damaged by heat generated by the current.

[0033] Switch 16 is connected in parallel to semiconductor switch 15. Switch 16 is turned off in inverter power supply mode. If inverter 10 fails or an overload occurs in inverter power supply mode, switch 16 is turned on. Switch 16 is turned on in bypass power supply mode. Switch 16 corresponds to one embodiment of a "second switch." The parallel circuit of semiconductor switch 15 and switch 16 constitutes a "bypass circuit."

[0034] The instantaneous value of the AC input voltage Vc appearing at a node N3 between the bypass input terminal T2 and the parallel circuit of the switch 16 and the semiconductor switch 15 is detected by the control device 18.

[0035] The operation unit 17 includes a plurality of buttons operated by the user of the uninterruptible power supply 1, an image display unit that displays various information, and the like. By operating the operation unit 17, the user can turn the power supply of the uninterruptible power supply 1 on and off, and select either the inverter power supply mode or the bypass power supply mode. In addition, by operating the operation unit 17, the user can select the operating mode of the uninterruptible power supply 1 when the auto-transfer function described below does not operate normally. The operation unit 17 corresponds to one embodiment of the "selection unit."

[0036] The control device 18 controls the entire uninterruptible power supply 1 based on the AC input voltages Vi, Vc, the AC input current Ii, the DC voltage VDC, the terminal voltage VB of the battery 23, the AC output voltage Vo, the AC current (load current) Io, and signals from the operation unit 17.

[0037] 2 is a block diagram showing an example of the hardware configuration of the control device 18. Typically, the control device 18 can be configured by a microcomputer in which a predetermined program is stored in advance.

[0038] 2, the control device 18 includes a CPU (Central Processing Unit) 102, a memory 104, and an input / output (I / O) circuit 106. The CPU 102, the memory 104, and the I / O circuit 106 can exchange data with one another via a bus 108. Programs are stored in a partial area of ​​the memory 104, and the CPU 102 executes these programs to realize various functions described below. The I / O circuit 106 inputs and outputs signals and data to and from the outside of the control device 18.

[0039] 2, at least a part of the control device 18 can be configured using a circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).Furthermore, at least a part of the control device 18 can be configured using an analog circuit.

[0040] <Auto transfer function> The uninterruptible power supply 1 according to this embodiment has an automatic transfer function. In this specification, the "automatic transfer function" refers to a function that automatically switches the inverter power supply mode to the bypass power supply mode when an overload occurs in the inverter power supply mode, and automatically returns to the inverter power supply mode after the overload is resolved.

[0041] Fig. 3 is a time chart for explaining the auto-transfer function. Fig. 3 shows changes over time in AC output voltage Vo, AC input voltage Vc, switches 14 and 16, and semiconductor switch 15. In the following description, AC output voltage Vo may be referred to as the "inverter output voltage Vo," and AC input voltage Vc may be referred to as the "bypass input voltage Vc."

[0042] As shown in Fig. 3, at time t0, the inverter power supply mode is selected in the uninterruptible power supply 1. In the inverter power supply mode, switch 14 is turned on, and semiconductor switch 15 and switch 16 are turned off. In this case, AC power supplied from commercial AC power supply 21 via switch 2 is converted into DC power by converter 6. The DC power generated by converter 6 is stored in battery 23 by bidirectional chopper 7, and is also converted into AC power by inverter 10 and supplied to load 24 via switch 14.

[0043] In the inverter power supply mode, the control device 18 controls the inverter 10 so as to synchronize the inverter output voltage Vo with the bypass input voltage Vc. Specifically, the control device 18 compares the amplitude and phase of the bypass input voltage Vc with that of the inverter output voltage Vo, and, based on the comparison result, adjusts the amplitude and phase of the inverter output voltage Vo so that it is synchronized with the amplitude and phase of the bypass input voltage Vc. By synchronizing the bypass input voltage Vc with the inverter output voltage Vo in this way, it is possible to switch between the inverter power supply mode and the bypass power supply mode without momentary interruption.

[0044] In the inverter power supply mode, a short circuit may occur in the load 24, causing an overcurrent to flow in the uninterruptible power supply 1. Alternatively, a load 24 with a large inrush current may be turned on, causing an overcurrent to flow in the uninterruptible power supply 1. At time t1, when the output signal of the current detector 11 detects that the output current (load current) Io of the inverter 10 has exceeded a predetermined allowable current range, the control device 18 determines that an overload has occurred and stops the operation of the inverter 10.

[0045] Furthermore, control device 18 switches uninterruptible power supply 1 from inverter power supply mode to bypass power supply mode using switches 14 and 16 and semiconductor switch 15. Specifically, control device 18 instantly turns on semiconductor switch 15 at time t1 to supply bypass input voltage Vc to load 24. Thereafter, switch 14 is turned off at time t2, and switch 16 is turned on at the following time t3, completing uninterruptible switching. Semiconductor switch 15 is turned off at time t4 after switch 16 is turned on.

[0046] In the bypass power supply mode, at time t5, a fixed time after time t4, the control device 18 restarts the inverter 10 and puts the inverter 10 into a no-load operation standby state. After time t5, the control device 18 controls the inverter 10 so that the inverter output voltage Vo is synchronized with the bypass input voltage Vc.

[0047] In the bypass power supply mode, the control device 18 determines whether the overload has been resolved based on the output signal of the current detector 11. Specifically, the control device 18 determines that the overload has been resolved when it is confirmed from the output signal of the current detector 11 that the output current (load current) Io of the inverter 10 has returned to within the allowable current range.

[0048] For example, if it is determined that the overload has been resolved at time t6 due to the short-circuit fault on the load 24 side being resolved, the control device 18 compares the output voltage Vo of the inverter 10, which is in a no-load operation standby state, with the bypass input voltage Vc to determine whether synchronization between the inverter output voltage Vo and the bypass input voltage Vc has been restored.

[0049] When it is determined at time t7 that synchronization between the inverter output voltage Vo and the bypass input voltage Vc has been restored, the control device 18 switches from the bypass power supply mode to the inverter power supply mode using the switches 14 and 16 and the semiconductor switch 15, thereby restoring the uninterruptible power supply 1 to a normal operating state. Specifically, the control device 18 instantly turns on the semiconductor switch 15 at time t7 to supply the inverter output voltage Vo to the load 24. Thereafter, the switch 16 is turned off at time t8, and the switch 14 is turned on at the following time t9, completing uninterruptible switching. The semiconductor switch 15 is turned off at time t10 after the switch 14 is turned on.

[0050] However, in the above-described automatic transfer function, there are cases where, for some reason, synchronization between the inverter output voltage Vo and the bypass input voltage Vc is not restored after restarting the inverter 10 in the bypass power supply mode. In such a case, even though the overload has been resolved, the uninterruptible power supply 1 continues in the bypass power supply mode until synchronization between the inverter output voltage Vo and the bypass input voltage Vc is restored.

[0051] However, in the event of a power outage or other abnormality occurring in the bypass AC power supply 22 during this bypass power supply mode, the uninterruptible power supply 1 will be unable to supply power to the load 24, and as a result, the load 24 will be unable to operate. However, with conventional uninterruptible power supplies, as long as the load 24 is operating normally, the user of the uninterruptible power supply is unable to grasp such a situation. This poses a problem in that it is not possible to take appropriate measures to maintain the reliability of the power supply to the load 24.

[0052] Therefore, in this embodiment, a plurality of operation modes are provided to cope with such a case where the automatic transfer function does not operate normally, and the user of the uninterruptible power supply 1 is configured to select one of the operation modes. Note that this operation mode selection can be performed, for example, by the operation unit 17.

[0053] In this configuration, if a situation occurs in which the automatic transfer function does not operate normally during operation of the uninterruptible power supply 1, the control device 18 executes the selected operation mode. The multiple operation modes include first to third operation modes. Each operation mode will be described below.

[0054] (First operating mode) Fig. 4 is a time chart for explaining the first operating mode. The time chart shown in Fig. 4 differs from the time chart shown in Fig. 3 in that synchronization between the inverter output voltage Vo and the bypass input voltage Vc is not restored even after time t6 when the overload is resolved. For this reason, the uninterruptible power supply 1 continues in the bypass power supply mode even after time t6.

[0055] When the first operating mode is selected, if the control device 18 determines that the inverter output voltage Vo and the bypass input voltage Vc are not synchronized at time t6 when the overload is eliminated, the control device 18 uses a timer to measure the time during which the inverter output voltage Vo and the bypass input voltage Vc are out of sync. If the inverter output voltage Vo and the bypass input voltage Vc are synchronized again during the measurement, the timer's measurement value is reset.

[0056] When, at time t11, the time measured by the timer reaches a preset first time, the control device 18 outputs an alarm indicating that the auto-transfer function is not operating normally, i.e., that the uninterruptible power supply 1 is continuing in the bypass power supply mode. In one aspect, the control device 18 outputs a sound notifying the alarm from the operation unit 17 and / or displays a message notifying the alarm on the display of the operation unit 17. In another aspect, the control device 18 transmits an alarm via the I / O circuit 106 to a management device that remotely manages the uninterruptible power supply 1.

[0057] According to the first operation mode, it is possible to continue supplying power to the load 24 in the bypass power supply mode, while informing the user of the uninterruptible power supply 1 that the automatic transfer function is not operating normally.

[0058] (Second operating mode) Fig. 5 is a time chart for explaining the second operation mode. The time chart shown in Fig. 5 differs from the time chart shown in Fig. 3 in that synchronization between the inverter output voltage Vo and the bypass input voltage Vc is not restored even after time t6 when the overload is resolved. For this reason, the uninterruptible power supply 1 continues in the bypass power supply mode even after time t6.

[0059] When the second operating mode is selected, if the control device 18 determines that the inverter output voltage Vo and the bypass input voltage Vc are not synchronized at time t6 when the overload is eliminated, the control device 18 uses a timer to measure the time during which the inverter output voltage Vo and the bypass input voltage Vc are out of sync. If the inverter output voltage Vo and the bypass input voltage Vc are synchronized again during the measurement, the timer's measurement value is reset.

[0060] If, at time t12, the time measured by the timer reaches a preset second time, the control device 18 determines that the automatic transfer function is not operating normally. In this case, the control device 18 performs a momentary interruption switch from the bypass power supply mode to the inverter power supply mode using the switches 14 and 16. Specifically, at time t12, the control device turns off the switch 16 to stop the supply of the bypass input voltage Vc. At the following time t13, the control device 18 turns on the switch 14 to supply the inverter output voltage Vo to the load 24.

[0061] In the second operating mode, switching from the bypass power supply mode to the inverter power supply mode after a momentary power interruption can automatically return to the inverter power supply mode. Switching the power supply after a momentary power interruption can also prevent current from flowing between the bypass circuit and the inverter due to a phase difference between the bypass input voltage Vc and the inverter output voltage Vo.

[0062] However, in the second operation mode, a momentary interruption in the load power supply (time t12 to t13) occurs, which may affect the load 24. Therefore, it is necessary to determine which loads 24 can be used in the second operation mode.

[0063] (Third operating mode) Fig. 6 is a block diagram showing an example of the configuration of an uninterruptible power supply system to which the third operation mode is applied. As shown in Fig. 6, the uninterruptible power supply system includes a plurality of (two in Fig. 6) uninterruptible power supply devices 1, 1P, a switching circuit 40, and a main control device 30.

[0064] The uninterruptible power supplies 1 and 1P have the same configuration as the uninterruptible power supply 1 shown in Fig. 1. However, the uninterruptible power supply 1 is used as a regular uninterruptible power supply (hereinafter also referred to as a regular UPS) that supplies AC power to a load 24. The uninterruptible power supply 1P is used as a backup uninterruptible power supply (hereinafter also referred to as a backup UPS) that supplies AC power to a load 24 in the event of a failure of the regular uninterruptible power supply 1.

[0065] The control device 18 of the uninterruptible power supply 1 and the control device 18 of the uninterruptible power supply 1P are connected to the main control device 30 by a communication line. The control device 18 of the uninterruptible power supply 1, the control device 18 of the uninterruptible power supply 1P, and the main control device 30 exchange various information via the communication line.

[0066] The switching circuit 40 is connected between the AC output terminals T4 of the uninterruptible power supply 1 and the uninterruptible power supply 1P and the load 24. The switching circuit 40 includes a switch 42 connected between the AC output terminal T4 of the uninterruptible power supply 1 and the load 24, and a switch 44 connected between the AC output terminal T4 of the uninterruptible power supply 1P and the load 24. The switching circuit 40 is, for example, a static transfer switch (STS). The switches 42 and 44 are, for example, semiconductor switches.

[0067] The switches 42 and 44 of the switching circuit 40 can be controlled by the main control device 30. When the uninterruptible power supply 1 is normal, the switch 42 is turned on and the switch 44 is turned off, and AC power is supplied from the uninterruptible power supply 1 to the load 24. When the uninterruptible power supply 1 fails, the switch 42 is turned off and the switch 44 is turned on, and AC power is supplied from the uninterruptible power supply 1P to the load 24. The switching circuit 40 switches the output of the uninterruptible power supplies 1 and 1P without or with momentary interruption, so as to continue the power supply from one of the uninterruptible power supplies to the load 24. The switches 42 and 44 of the switching circuit 40 may also be operated manually.

[0068] In each of the uninterruptible power supplies 1, 1P, the control device 18 compares the amplitude and phase of the bypass input voltage Vc with that of the inverter output voltage Vo, and, based on the comparison result, adjusts the amplitude and phase of the inverter output voltage Vo so that it is synchronized with the amplitude and phase of the bypass input voltage Vc. This allows the output voltage of the uninterruptible power supply 1 to be synchronized with the output voltage of the uninterruptible power supply 1P, making it possible to switch between the uninterruptible power supplies 1, 1P without momentary interruption.

[0069] Fig. 7 is a time chart for explaining the third operation mode. The time chart shown in Fig. 7 differs from the time chart shown in Fig. 3 in that synchronization between the inverter output voltage Vo and the bypass input voltage Vc is not restored even after time t6 when the overload is resolved. For this reason, the uninterruptible power supply 1 continues in the bypass power supply mode even after time t6.

[0070] When the third operating mode is selected, if the control device 18 determines that the inverter output voltage Vo and the bypass input voltage Vc have not regained synchronization at time t6 when the overload is eliminated, the control device 18 uses a timer to measure the time during which the inverter output voltage Vo and the bypass input voltage Vc are out of synchronization. The control device 18 transmits the timer measurement value to the main control device 30.

[0071] If, at time t14, the time measured by the timer reaches a preset third time, main control device 30 determines that the automatic transfer function is not operating normally. In this case, main control device 30 uses switching circuit 40 to switch the load power supply from uninterruptible power supply 1 to uninterruptible power supply 1P. Because the output voltage (bypass input voltage Vc) of uninterruptible power supply 1 operating in bypass power supply mode and the output voltage (inverter output voltage Vo) of uninterruptible power supply 1P operating in inverter power supply mode are synchronized, uninterruptible power supplies 1 and 1P can be switched without interruption. Control device 18 stops operation of uninterruptible power supply 1 in response to this power supply switch.

[0072] According to the third operation mode, the uninterruptible power supply 1P supplies power to the load 24 instead of the uninterruptible power supply 1 operating in the bypass power supply mode, so that the reliability of power supply to the load 24 can be improved.

[0073] 8 and 9 are flowcharts showing the operation of the uninterruptible power supply 1. The processes shown in FIGS.

[0074] 8, in step S01, controller 18 determines whether or not inverter power supply mode is selected. If inverter power supply mode is not selected, that is, if bypass power supply mode is selected (NO in S01), controller 18 skips the processing from step S02 onwards.

[0075] If the inverter power supply mode is selected (YES in S01), the control device 18 controls the inverter 10 in step S02 so as to synchronize the AC output voltage (inverter output voltage) Vo with the AC input voltage (bypass input voltage) Vc.

[0076] In step S03, the control device 18 detects whether the output current (load current) Io of the inverter 10 has exceeded a predetermined allowable current range based on the output signal of the current detector 11. If the output current Io of the inverter 10 has exceeded the allowable current range, the control device 18 detects an overload (YES in S03) and stops the operation of the inverter 10 in step S04.

[0077] Furthermore, in step S05, the control device 18 switches the uninterruptible power supply 1 from the inverter power supply mode to the bypass power supply mode using the switches 14 and 16 and the semiconductor switch 15 without momentary interruption.

[0078] In response to the lapse of a certain time period after switching to the bypass power supply mode, the control device 18 restarts the inverter 10 in step S06 and places the inverter 10 in a no-load operation standby state. In step S07, the control device 18 controls the inverter 10 so as to synchronize the inverter output voltage Vo with the bypass input voltage Vc.

[0079] In step S08, the control device 18 determines whether the overload has been resolved based on the output signal of the current detector 11. If the output current Io of the inverter 10 exceeds the allowable current range, the control device 18 determines that the overload has not been resolved (NO in S08) and continues the processing of step S07.

[0080] If it is confirmed from the output signal of the current detector 11 that the output current Io of the inverter 10 has returned to within the allowable current range, the control device 18 determines that the overload has been resolved (YES in S08), and in step S09, compares the output voltage Vo of the inverter 10, which is in a no-load operation standby state, with the bypass input voltage Vc to determine whether synchronization between the inverter output voltage Vo and the bypass input voltage Vc has been restored.

[0081] When it is determined that synchronization between the inverter output voltage Vo and the bypass input voltage Vc has been restored (YES determination in step S09), the control device 18 proceeds to step S10, and switches from the bypass power supply mode to the inverter power supply mode without momentary interruption using the switches 14, 16 and the semiconductor switch 15, thereby restoring the uninterruptible power supply 1 to a normal operating state.

[0082] On the other hand, if it is determined that synchronization between the inverter output voltage Vo and the bypass input voltage Vc has not been restored (NO in step S09), the control device 18 determines that there is a possibility that the auto-transfer function cannot operate normally, and executes the processing of steps S11 to S20.

[0083] Specifically, in step S11, the control device 18 determines whether the first operating mode has been selected by the user of the uninterruptible power supply 1. If the first operating mode has been selected (YES in S11), the control device 18 uses a timer to measure the time during which the inverter output voltage Vo and the bypass input voltage Vc are out of sync. The timer measurement value is reset when the inverter output voltage Vo and the bypass input voltage Vc are restored to synchronization.

[0084] If the time measured by the timer from the point in time when the overload was eliminated reaches a preset first time (YES in S12), the control device 18 outputs an alarm in step S13 indicating that the auto-transfer function is not operating normally, i.e., indicating that the uninterruptible power supply 1 is continuing in the bypass power supply mode. For example, the control device 18 outputs a sound notifying the alarm from the operation unit 17 and / or displays a message notifying the alarm on the display of the operation unit 17. Alternatively, the control device 18 transmits an alarm via the I / O circuit 106 to a management device that remotely manages the uninterruptible power supply 1.

[0085] If the first operation mode is not selected in step S11 (determined as NO in S11), the control device 18 determines in step S14 whether the second operation mode has been selected by the user of the uninterruptible power supply 1. If the second operation mode has been selected (determined as YES in S14), the control device 18 uses a timer to measure the time during which the inverter output voltage Vo and the bypass input voltage Vc are in an asynchronous state.

[0086] If the time measured by the timer from the time the overload was eliminated reaches a preset second time (YES in S15), the control device 18 proceeds to step S16 and performs a momentary interruption switch from the bypass power supply mode to the inverter power supply mode using the switches 14 and 16.

[0087] If the second operating mode is not selected in step S14 (determination of NO in S14), the control device 18 determines in step S17 whether the user of the uninterruptible power supply 1 has selected the third operating mode. If the third operating mode is selected (determination of YES in S17), the control device 18 uses a timer to measure the time during which the inverter output voltage Vo and the bypass input voltage Vc are out of sync. The control device 18 transmits the timer measurement value to the main control device 30.

[0088] If the time measured by the timer from the time the overload was eliminated reaches a preset third time (YES in S18), main control device 30 proceeds to step S19 and switches the load power supply from uninterruptible power supply 1 (main uninterruptible power supply) to uninterruptible power supply 1P (standby uninterruptible power supply) using switching circuit 40. Control device 18 stops operation of uninterruptible power supply 1 (main uninterruptible power supply) in step S20.

[0089] As described above, according to this embodiment, multiple operating modes are provided to deal with cases where the auto-transfer function does not operate normally. Therefore, the user of the uninterruptible power supply 1 can select one of the multiple operating modes depending on the load 24's tolerance to voltage fluctuations, the importance of the load 24, and other factors. For example, the first operating mode can be selected if the load 24 includes a load that is highly sensitive to power supply fluctuations, and the second operating mode can be selected if the load 24 does not include a load that is highly sensitive to power supply fluctuations. Furthermore, if a standby uninterruptible power supply 1P is provided to back up the uninterruptible power supply 1, the third operating mode can be selected. This can avoid a situation in which the bypass power supply mode continues, and can take appropriate measures depending on the load 24, thereby improving the power supply reliability of the uninterruptible power supply 1.

[0090] At least two of the first to third operating modes may be combined. For example, when the first operating mode is combined with the second operating mode, an alarm is output to indicate that the automatic transfer function is not operating normally, and a momentary power interruption occurs, switching from the bypass power supply mode to the inverter power supply mode. When the first operating mode is combined with the third operating mode, an alarm is output to indicate that the automatic transfer function is not operating normally, and the load power supply is switched from the uninterruptible power supply 1 to the standby uninterruptible power supply 1P. In this case, the user of the uninterruptible power supply 1 may manually switch the switching circuit 40.

[0091] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0092] 1,1P uninterruptible power supply, 2,8,14,16,42,44 switch, 3,11 current detector, 4,9,13 capacitor, 5,12 reactor, 6 converter, 7 bidirectional chopper, 10 inverter, 15 semiconductor switch, 17 operation unit, 18 control device, 21 commercial AC power supply, 22 bypass AC power supply, 23 battery, 24 load, 30 main control device, 40 switching circuit, 102 CPU, 104 memory, 106 I / O circuit, 108 bus, T1 AC input terminal, T2 bypass input terminal, T3 battery terminal, T4 AC output terminal.

Claims

1. An uninterruptible power supply, a converter that converts AC power supplied from an AC power source into DC power; an inverter that converts DC power supplied from the converter into AC power and supplies the AC power to a load; a switch having a first terminal for receiving AC power from the AC power supply and a second terminal for connecting to the load; a current detector for detecting an output current of the uninterruptible power supply; a control device that controls the inverter and the switch, When the detected value of the current detector exceeds an allowable current range during an inverter power supply mode in which the AC power generated by the inverter is supplied to the load, the control device by stopping the operation of the inverter and turning on the switch, switching to a bypass power supply mode in which AC power from the AC power supply is supplied to the load; In the bypass power supply mode, the inverter is restarted, and the inverter is controlled so as to synchronize an AC output voltage output from the inverter with an AC input voltage input to the switch, and when a detection value of the current detector returns to within the allowable current range, the switch is turned off in response to the AC output voltage being synchronized with the AC input voltage, and the mode is switched to the inverter power supply mode, further comprising a selection unit for selecting one of the first to third operation modes; when the AC output voltage is not synchronized with the AC input voltage when the detection value of the current detector has returned to within the allowable current range, the control device is further configured to execute the operation mode selected by the selection unit; The control device when the first operation mode is selected by the selection unit, when a time during which the AC input voltage and the AC output voltage are in an asynchronous state reaches a first time, an alarm is output indicating that the bypass power supply mode is continuing; when the second operation mode is selected by the selection unit, when a time during which the AC input voltage and the AC output voltage are in an asynchronous state reaches a second time, turning off the switch and switching to the inverter power supply mode; When the third operating mode is selected by the selection unit, when the time during which the AC input voltage and the AC output voltage are asynchronous reaches a third time, the uninterruptible power supply switches to power supply from a standby uninterruptible power supply and stops operation of the uninterruptible power supply.

2. a first switch connected between an output node of the inverter and the second terminal of the switch; the switch includes a semiconductor switch and a second switch connected in parallel to the semiconductor switch; In the bypass power supply mode, the control device turning off the first switch and turning on the second switch; when the detection value of the current detector returns to within the allowable current range and the AC output voltage is synchronized with the AC input voltage, the semiconductor switch is turned on for a predetermined time, and during the predetermined time, the second switch is turned off and the first switch is turned on, thereby switching to the inverter power supply mode without momentary interruption; 2. The uninterruptible power supply according to claim 1, wherein, when the second operation mode is selected by the selection unit, the control device switches to the inverter power supply mode with a momentary power interruption by turning off the second switch and turning on the first switch when the time during which the AC input voltage and the AC output voltage are asynchronous reaches the second time period.

3. a switching circuit for connecting either the uninterruptible power supply or the standby uninterruptible power supply to the load, 2. The uninterruptible power supply according to claim 1, wherein, when the third operating mode is selected by the selection unit, the switching circuit connects the standby uninterruptible power supply to the load when the time during which the AC input voltage and the AC output voltage are asynchronous reaches the third time.

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