Uninterruptible power supply device

Abstract

The non-outage power supply device comprises a semiconductor switch (1) and an inverter (8), the semiconductor switch (1) is connected between a bypass AC power supply (11) and a load (14), and the semiconductor switch (1) is turned on when the bypass AC power supply does not fail and is turned off when the bypass AC power supply is powered off, and the inverter (8) is turned off when the bypass AC power supply is powered off. A DC power supplied from an AC power supply (12) or a battery (13) is converted into an AC power and supplied to a load, and when a load current (IL) is greater than a threshold current (Ith) during non-failure of the bypass AC power supply, an auxiliary current (Ia) corresponding to the difference between the load current and the threshold current is supplied to the load. Therefore, even if the load current increases due to load variation, the current flowing through the semiconductor switch can be maintained to be equal to or less than the threshold current.

Description

Technical Field

[0001] The present application relates to an uninterruptible power supply device, and more particularly to an uninterruptible power supply device including a semiconductor switch and an inverter. Background Art

[0002] For example, International Publication No. 2017 / 009998 (Patent Document 1) discloses an uninterruptible power supply device having a bypass switch, a small semiconductor switch, and a power converter connected in parallel between an AC power source and a load. The power converter includes a rectifier that converts AC power supplied from an AC power source into DC power, and an inverter that converts DC power into AC power and supplies the AC power to the load.

[0003] When the AC power supply is not faulty, the inverter power supply mode is executed, and the bypass switch and the semiconductor switch are turned off. In addition, the rectifier converts the AC power from the AC power supply into DC power. The DC power is stored in the battery and supplied to the inverter. The inverter converts the DC power into AC power and supplies it to the load.

[0004] In the event of an inverter failure, the bypass power supply mode is executed, the operation of the power converter is stopped, and the bypass switch and the semiconductor switch are turned on. In order to prevent the semiconductor switch from overheating due to the current, the semiconductor switch is turned off after a specified time. AC power is supplied from the AC power supply to the load via the bypass switch.

[0005] In the event of an AC power outage, the battery power supply mode is executed, the rectifier stops operating, and the inverter converts the battery's DC power into AC power and supplies it to the load. Therefore, even in the event of an AC power outage, the load can continue to operate while DC power is stored in the battery.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2017 / 009998 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] However, in the above-mentioned uninterruptible power supply device, loss mainly occurs in the power converter, and there is a problem that the efficiency is as low as about 96%. As a countermeasure, an uninterruptible power supply device with a bypass ECO power supply mode has attracted attention. This uninterruptible power supply device has a large semiconductor switch and a power converter connected in parallel between the AC power supply and the load.

[0011] When the AC power supply is not faulty, the bypass ECO power supply mode is executed, the semiconductor switch is turned on, and the AC power from the AC power supply is supplied to the load via the semiconductor switch. In the event of an AC power outage, the battery power supply mode is executed, the semiconductor switch is turned off, and the inverter included in the power converter converts the DC power of the battery into AC power and supplies it to the load. In this uninterruptible power supply device, losses are mainly generated in the semiconductor switch, but since the losses of the semiconductor switch are smaller than the losses of the power converter, it is possible to obtain an efficiency of up to 99%.

[0012] In the uninterruptible power supply device, a semiconductor switch of a required capacity is usually used to supply the rated current of the load. However, when the load current increases compared to the specified current due to load fluctuation, there is a problem that the semiconductor switch is turned off after a specified time to prevent overheating of the semiconductor switch, and the operation of the load stops.

[0013] As a countermeasure, a method of using a large-capacity semiconductor switch capable of supplying a current sufficiently larger than the rated current of the load may be considered, but this method has the problem of increasing the size of the device and the cost.

[0014] Therefore, the main object of the present application is to provide an uninterruptible power supply device that is strong in coping with load fluctuations and is small and low-priced.

[0015] Means for solving technical problems

[0016] The uninterruptible power supply device of the present application comprises a semiconductor switch and an inverter. The semiconductor switch is connected between a first AC power supply and a load, and is turned on when the first AC power supply is not faulty, and is turned off when the first AC power supply is out of power. When the first AC power supply is out of power, the inverter converts the DC power supplied from the DC power supply into AC power and supplies it to the load, and when the load current is greater than the threshold current when the first AC power supply is not faulty, the inverter supplies an auxiliary current equal to the difference between the load current and the threshold current to the load.

[0017] Effects of the Invention

[0018] In the uninterruptible power supply device of the present application, when the load current is larger than the threshold current when the first AC power supply is not faulty, an auxiliary current equal to the difference between the load current and the threshold current is supplied from the inverter to the load. Therefore, even when the load current increases due to load fluctuations, the current flowing in the semiconductor switch can be maintained below the threshold current, and overheating of the semiconductor switch can be prevented. Therefore, it is possible to prevent the semiconductor switch from being disconnected and the operation of the load from stopping, and an uninterruptible power supply device that can cope with strong load fluctuations can be realized. In addition, since there is no need to use a large-capacity semiconductor switch to increase the load current, the device can be miniaturized and cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a circuit block diagram showing the configuration of an uninterruptible power supply device according to one embodiment of the present application.

[0020] Figure 2 Yes means Figure 1 A block diagram of the main parts of the control device is shown.

[0021] Figure 3 Yes means Figure 2 1 is a block diagram showing the configuration of a portion of a control circuit related to control of a semiconductor switch.

[0022] Figure 4 Yes means Figure 3 The timing diagram of the operation of the control unit shown.

[0023] Figure 5 Yes means Figure 2 1 is a block diagram showing the configuration of a portion of the control circuit related to inverter control.

[0024] Figure 6 Yes means Figure 1 to Figure 5 The flowchart of the operation of the uninterruptible power supply device is shown.

[0025] Figure 7 This is a circuit block diagram for explaining the operation of the uninterruptible power supply device in the inverter auxiliary power supply mode.

[0026] Figure 8 This is a circuit block diagram for explaining the operation of the uninterruptible power supply device in the battery power supply mode.

[0027] Fig. 9 This is a circuit block diagram for explaining the operation of the comparative example.

[0028] Fig.10 This is a circuit block diagram for explaining other operations of the comparative example.

[0029] Fig.11 It is a diagram for explaining the effects of the embodiment.

[0030] Fig.12 This is a circuit block diagram showing a modified example of the embodiment. DETAILED DESCRIPTION

[0031] Figure 1 1 is a circuit block diagram showing the structure of an uninterruptible power supply device according to one embodiment of the present application. Figure 1In the uninterruptible power supply device, there is a bypass input terminal T1, an input terminal T2, a DC terminal T3, an output terminal T4, a semiconductor switch 1, switches S1~S3, a rectifier 4, current detectors CD1~CD4, a DC line 5, a capacitor 6, a bidirectional chopper 7, an inverter 8, an operating unit 9, and a control device 10.

[0032] The bypass input terminal T1 receives AC power of a predetermined frequency (e.g., commercial frequency) from the bypass AC power source 11 (first AC power source). The input terminal T2 receives AC power of a predetermined frequency (e.g., commercial frequency) from the AC power source 12 (second AC power source). Each of the AC power sources 11 and 12 may be a commercial AC power source or a generator. The AC power sources 11 and 12 may also both be commercial AC power sources.

[0033] The DC terminal T3 is connected to a battery 13. The battery 13 (power storage device) stores DC power. A capacitor may be connected instead of the battery 13. The output terminal T4 is connected to a load 14. The load 14 is driven by AC power of a predetermined frequency (for example, a commercial frequency) supplied from the uninterruptible power supply device.

[0034] The semiconductor switch 1 is connected between the input terminal T1 and the output terminal T4 . The semiconductor switch 1 includes a pair of thyristors 2 and 3 connected in anti-parallel to each other, and is controlled by a control device 10 .

[0035] When AC power is normally supplied from the bypass AC power source 11 (when the bypass AC power source 11 is not faulty), the semiconductor switch 1 is turned on, and AC power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1 .

[0036] When the bypass AC power source 11 is not normally supplied with AC power (when the bypass AC power source 11 is powered off), the semiconductor switch 1 is turned off, and the bypass AC power source 11 and the load 14 are disconnected.

[0037] The instantaneous value of the AC input voltage VI supplied from the bypass AC power source 11 is detected by the control device 10. The control device 10 determines whether the AC voltage VI is normally supplied from the bypass AC power source 11 based on the instantaneous value of the AC input voltage VI.

[0038] The switch S1 is connected between the input terminal T2 and the AC node of the rectifier 4, and is controlled by the control device 10. When the AC power is normally supplied from the AC power source 12 (when the AC power source 12 is not faulty), the switch S1 is turned on, and the AC power is supplied from the AC power source 12 to the rectifier 4 via the switch S1. When the AC power is not normally supplied from the AC power source 12 (when the AC power source 12 is powered off), the switch S1 is turned off, and the connection between the AC power source 12 and the rectifier 4 is cut off.

[0039] The instantaneous value of the AC input voltage Vi supplied from the AC power source 12 is detected by the control device 10. Based on the instantaneous value of the AC input voltage Vi, the control device 10 determines whether the AC voltage Vi is normally supplied from the AC power source 12. The current detector CD1 detects the AC input current Ii flowing between the AC power source 12 and the rectifier 4, and provides the control device 10 with a signal Iif indicating the detection value thereof.

[0040] The rectifier 4 (converter) is controlled by the control device 10, and when the AC power source 12 is not faulty, it converts the AC power from the AC power source 12 into DC power and outputs it to the DC line 5. The rectifier 4 is a well-known device including a plurality of IGBTs (Insulated Gate Bipolar Transistors) and diodes.

[0041] The capacitor 6 is connected to the DC line 5 to smooth and stabilize the DC voltage VD of the DC line 5. The instantaneous value of the DC voltage VD of the DC line 5 is detected by the control device 10.

[0042] When the AC power source 12 is not faulty, the control device 10 controls the rectifier 4 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. When the AC power source 12 fails, the control device 10 stops the operation of the rectifier 4.

[0043] The DC line 5 is connected to the DC terminal T3 via the bidirectional chopper 7 and the switch S2. The switch S2 is controlled by the control device 10. When the uninterruptible power supply device is used, the switch S2 is turned on. When the battery 13 and the bidirectional chopper 7 are maintained, the switch S2 is turned off.

[0044] The instantaneous value of the voltage VB between the terminals of the battery 13 is detected by the control device 10. The current detector CD2 detects the DC current IB flowing between the battery 13 and the bidirectional chopper 7, and supplies the control device 10 with a signal IBf indicating the detected value.

[0045] The bidirectional chopper 7 is controlled by the control device 10, and receives and / or outputs direct current between the direct current line 5 and the battery 13. The bidirectional chopper 7 is a well-known device including a plurality of sets of IGBTs and diodes, and a reactor.

[0046] When the AC power source 12 is not faulty, the control device 10 controls the bidirectional chopper 7 so that the battery voltage VB becomes the reference DC voltage VBR. When the AC power source 12 fails, the control device 10 controls the bidirectional chopper 7 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. The rectifier 4, the bidirectional chopper 7, and the battery 13 constitute an embodiment of a "DC power source" that supplies DC power to the inverter 8.

[0047] Furthermore, the DC line 5 is connected to a DC node of the inverter 8 , and the AC node of the inverter 8 is connected to a node N1 between the semiconductor switch 1 and the output terminal T4 via the switch S3 .

[0048] The switch S3 is controlled by the control device 10. When the uninterruptible power supply device is used, the switch S3 is turned on. When the inverter 8 is maintained, the switch S3 is turned off.

[0049] The current detector CD3 detects the AC output current IO of the inverter 8, and provides a signal IOf indicating the detection value thereof to the control device 10. The current detector CD4 detects the load current IL flowing from the node N1 to the load 14, and provides a signal ILf indicating the detection value thereof to the control device 10. In addition, the instantaneous value of the AC output voltage VO applied to the load 14 is detected by the control device 10.

[0050] The inverter 8 is controlled by the control device 10, converts the DC power supplied from the rectifier 4 and the bidirectional chopper 7 via the DC line 5 into AC power of a predetermined frequency (for example, a commercial frequency), and supplies the AC power to the load 14. The inverter 8 is a well-known device including a plurality of IGBTs and diodes.

[0051] When the bypass AC power source 11 fails, the inverter 8 converts the DC power supplied from the rectifier 4 or the bidirectional chopper 7 into AC power and supplies it to the load 14. At this time, the control device 10 controls the inverter 8 so that the AC output voltage VO maintains the AC input voltage VI before the power failure.

[0052] When the load current IL of the bypass AC power source 11 is below the threshold current Ith during non-fault conditions, the inverter 8 enters a standby state in which it does not receive or output current from the bypass AC power source 11 and the load 14. The threshold current Ith is, for example, the rated current of the semiconductor switch 1. At this time, the control device 10 controls the inverter 8 so that the AC output current IO of the inverter 8 becomes 0A.

[0053] When the load current IL of the bypass AC power source 11 is greater than the threshold current Ith during non-fault conditions, the inverter 8 supplies the auxiliary current Ia=IL-Ith, which is the difference between the load current IL and the threshold current Ith, to the load 14. At this time, the control device 10 controls the inverter 8 so that the AC output current IO becomes the auxiliary current Ia.

[0054] The operation unit 9 includes a plurality of buttons, a plurality of switches, and an image display unit. The user of the uninterruptible power supply device can turn on and off the power supply of the uninterruptible power supply device, automatically operate the uninterruptible power supply device or manually operate the uninterruptible power supply device, or set the threshold current Ith to a desired value by operating the operation unit 9. The operation unit 9 outputs signals and information indicating the contents of the operation by the user to the control device 10.

[0055] The control device 10 controls the semiconductor switch 1, switches S1 to S3, the rectifier 4, the bidirectional chopper 7, and the inverter 8 based on the signal from the operating unit 9, the AC input voltages VI, Vi, the AC output voltage VO, the DC voltage VD, the battery voltage VB, the AC input current Ii, the battery current IB, the AC output current IO, and the load current IL.

[0056] Figure 2 is a block diagram showing the main parts of the control device 10. Figure 2 In the embodiment, the control device 10 includes voltage detectors 21 to 25 , power failure detectors 26 and 27 , a synchronization detector 28 , and a control circuit 29 .

[0057] The voltage detector 21 detects the instantaneous value of the AC input voltage VI supplied from the bypass AC power supply 11, and outputs a signal VIf indicating the detected value to the power failure detector 26 and the control circuit 29. The voltage detector 22 detects the instantaneous value of the AC input voltage Vi supplied from the AC power supply 12, and outputs a signal Vif indicating the detected value to the power failure detector 27 and the control circuit 29. The voltage detector 23 detects the instantaneous value of the AC output voltage VO applied to the load 14, and outputs a signal VOf indicating the detected value to the control circuit 29.

[0058] The voltage detector 24 detects the instantaneous value of the DC voltage VD of the DC line 5, and outputs a signal VDf indicating the detected value to the control circuit 29. The voltage detector 25 detects the instantaneous value of the voltage VB between the terminals of the battery 13, and outputs a signal VBf indicating the detected value to the control circuit 29. Figure 1 )'s output signals Iif, IBf, IOf, ILf are provided to the control circuit 29.

[0059] The power failure detector 26 detects whether a power failure has occurred in the bypass AC power supply 11 based on the output signal VIf of the voltage detector 21, and outputs a power failure detection signal φ26 indicating the detection result to the control circuit 29. When the bypass AC power supply 11 is not faulty, the power failure detection signal φ26 becomes an inactive level "H" level. When a power failure has occurred in the bypass AC power supply 11, the power failure detection signal φ26 becomes an active level "L" level.

[0060] For example, when the AC input voltage VI is higher than the lower limit value, the power failure detector 26 determines that the bypass AC power supply 11 is not at fault, and sets the power failure detection signal φ26 to the "H" level of the inactive level. In addition, when the AC input voltage VI is lower than the lower limit value, the power failure detector 26 determines that the bypass AC power supply 11 has a power failure, and sets the power failure detection signal φ26 to the "L" level of the active level.

[0061] The power failure detector 27 detects whether a power failure occurs in the AC power supply 12 based on the output signal Vif of the voltage detector 22, and outputs a power failure detection signal φ27 indicating the detection result to the control circuit 29. When the AC power supply 12 is not faulty, the power failure detection signal φ27 becomes an inactive level "H" level. When a power failure occurs in the AC power supply 12, the power failure detection signal φ27 becomes an active level "L" level.

[0062] For example, when the AC input voltage Vi is higher than the lower limit value, the power failure detector 27 determines that the AC power supply 12 is not faulty and sets the power failure detection signal φ27 to the "H" level, which is an inactive level. In addition, when the AC input voltage Vi is lower than the lower limit value, the power failure detector 27 determines that a power failure has occurred in the AC power supply 12 and sets the power failure detection signal φ27 to the "L" level, which is an active level.

[0063] The synchronous detector 28 determines whether the frequency and phase of the AC input voltage VI match the frequency and phase of the AC output voltage VO, and outputs a signal φ28 indicating the determination result. When the frequency and phase of the AC input voltage VI match the frequency and phase of the AC output voltage VO, the signal φ28 becomes an "H" level, and when they do not match, the signal φ28 becomes an "L" level.

[0064] The control circuit 29 controls the uninterruptible power supply device as a whole based on the output signals VIf, Vif, VOf, VDf, VBf of the voltage detectors 21 to 25, the output signals Iif, IBf, IOf, ILf of the current detectors CD1 to CD4, the signals φ26, φ27, φ28, and the signal from the operating unit 9.

[0065] That is, when the AC power supplies 11 and 12 are not in a faulty state (φ26=H, φ27=H), the control circuit 29 turns on the semiconductor switch 1 and switches S1~S3, and controls the rectifier 4 in such a way that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR, and controls the bidirectional chopper 7 in such a way that the battery voltage VB becomes the reference DC voltage VBR.

[0066] When the load current IL is less than the threshold current Ith, the control circuit 29 executes the bypass power supply mode and sets the inverter 8 to the standby state. In this case, AC power is supplied from the bypass AC power supply 11 to the load 14 via the semiconductor switch 1, and the load 14 is operated.

[0067] When the load current IL is larger than the threshold current Ith, the control circuit 29 executes the inverter auxiliary power supply mode and controls the inverter 8 so that the AC output current IO of the inverter 8 becomes the auxiliary current Ia=IL-Ith.

[0068] In this case, a threshold current Ith is supplied from the bypass AC power supply 11 to the load 14 via the semiconductor switch 1, and an auxiliary current Ia is supplied from the inverter 8 to the load 14, and the load 14 is operated by a load current IL=Ith+Ia which is the sum of the threshold current Ith and the auxiliary current Ia.

[0069] Therefore, even when the load current IL increases due to load fluctuation, the current flowing in the semiconductor switch 1 is maintained below the threshold current Ith, so there is no need to turn off the semiconductor switch 1 to prevent overheating of the semiconductor switch 1. Therefore, an uninterruptible power supply device that can cope with strong load fluctuations can be realized. In addition, since there is no need to use a large-capacity semiconductor switch 1 due to the increase in the load current IL, the device can be miniaturized and cost-effective.

[0070] When the bypass AC power source 11 fails (φ26=L), the control circuit 29 executes the battery power supply mode, turns off the semiconductor switch 1, and controls the inverter 8 in such a way that the AC output voltage VO of the inverter 8 maintains the AC input voltage VI before the power failure. In this case, the load current IL is supplied from the inverter 8 to the load 14, so that the load 14 operates. Therefore, even when the bypass AC power source 11 fails, the operation of the load 14 can continue when the AC power source 12 is not faulty.

[0071] When the bypass AC power supply 11 recovers from the power failure state and becomes a non-fault state, the control circuit 29 synchronizes the AC output voltage VO of the inverter 8 with the AC input voltage VI from the bypass AC power supply 11. When the frequency and phase of the AC output voltage VO match the frequency and phase of the AC input voltage VI and the output signal φ28 of the synchronization detector 28 becomes an "H" level, the control circuit 29 turns on the semiconductor switch 1.

[0072] When a power outage occurs in the AC power source 12 (φ27=L), the control circuit 29 turns off the switch S1, stops the operation of the rectifier 4, and controls the bidirectional chopper 7 in such a way that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. Therefore, even when a power outage occurs in the AC power source 11 or the AC power source 12, the operation of the load 14 can be continued while the DC power is stored in the battery 13.

[0073] When the AC power supply 12 recovers from a power outage and becomes a non-fault state (φ27=L), the control circuit 29 turns on the switch S1 to start the operation of the rectifier 4, controls the rectifier 4 in such a way that the DC voltage VD of the DC line 5 becomes a reference DC voltage VDR, and controls the bidirectional chopper 7 in such a way that the battery voltage VB becomes a reference DC voltage VBR.

[0074] Figure 3 2 is a block diagram showing a portion of the control circuit 29 related to the control of the semiconductor switch 1. Figure 3 In the embodiment, the control circuit 29 includes a control unit 31. The control unit 31 is based on the power failure detector 26 ( Figure 2 ) output signal φ26, the output signal φ28 of the synchronous detector 28, and the output signal VIf of the voltage detector 21, control the semiconductor switch 1, and generate a control signal φ31.

[0075] That is, the control unit 31 bypasses the AC power supply 11 ( Figure 1 ) is not a fault (φ26 = H), the thyristors 2 and 3 are controlled synchronously with the AC input voltage VI represented by the output signal VIf of the voltage detector 21, so that the semiconductor switch 1 is turned on. If the bypass AC power supply 11 ( Figure 1 )When a power outage occurs (φ26=L), the control unit 31 turns off the semiconductor switch 1.

[0076] If the bypass AC power supply 11 recovers from the power outage state to the non-fault state (φ26=H), and the frequency and phase of the AC output voltage VO of the inverter 8 are consistent with the frequency and phase of the AC input voltage VI from the bypass AC power supply 11 (φ28=H), the control unit 31 turns on the semiconductor switch 1.

[0077] The control signal φ31 is a signal indicating the state of the semiconductor switch 1. When the semiconductor switch 1 is off, the control signal φ31 becomes an "H" level. When the semiconductor switch 1 is on, the control signal φ31 becomes an "L" level. The control signal φ31 will be described later.

[0078] Figure 4 (A) to (C) are timing diagrams showing the operation of the control unit 31. Figure 4 , (A) shows a power failure detector 26 ( Figure 2 ) shows the waveform of the output signal φ26 of the synchronous detector 28 ( Figure 2 ) shows the waveform of the output signal φ28, and (C) shows the waveform of the control signal φ31.

[0079] At a certain time t0, it is assumed that the bypass AC power supply 11 is not faulty, and the semiconductor switch 1 is turned on. At this time, the output signal φ26 of the power failure detector 26 becomes "H" level. In addition, since the semiconductor switch 1 is turned on, the frequency and phase of the AC input voltage VI coincide with the frequency and phase of the AC output voltage VO, and the output signal φ28 of the synchronous detector 28 becomes "H" level. In addition, since the semiconductor switch 1 is turned on, the control signal φ31 becomes "L" level.

[0080] Next, when a power failure occurs in the bypass AC power source 11 at time t1, both the signals φ26 and φ28 drop from the “H” level to the “L” level, the semiconductor switch 1 is turned off, and the control signal φ31 rises to the “H” level.

[0081] Next, if the bypass AC power source 11 recovers from the power failure state to the non-fault state at time t2, the signal φ26 rises from the "L" level to the "H" level. Next, if the frequency and phase of the AC output voltage VO of the inverter 8 match the frequency and phase of the AC input voltage VI from the bypass AC power source 11 at time t3, the signal φ28 rises from the "L" level to the "H" level. As a result, the semiconductor switch 1 is turned on, and the control signal φ31 drops from the "H" level to the "L" level.

[0082] Figure 5 2 is a block diagram showing a portion of the control circuit 29 related to the control of the inverter 8. Figure 5 The control circuit 29 includes a phase synchronization control unit 40 , a voltage command unit 41 , current control units 42 , 53 , a PWM (Pulse Width Modulation) control unit 44 , 54 , a selector 45 , a calculation unit 50 , and a current command unit 51 .

[0083] When the bypass AC power source 11 is not in failure (φ26 = H), the phase synchronization control unit 40 is connected to the voltage detector 21 ( Figure 2 )'s output signal VIf represents an AC input voltage VI with the same frequency and outputting an AC signal vac with the same phase.

[0084] If a power outage occurs in the bypass AC power source 11 (φ26=L), the phase synchronization control unit 40 continues to output the AC signal vac before the power outage occurs. If the bypass AC power source 11 recovers from the power outage state to the non-fault state, the phase synchronization control unit 40 controls the frequency and phase of the AC signal vac so that the frequency and phase of the AC signal vac are consistent with the frequency and phase of the AC input voltage VI.

[0085] The voltage command unit 41 outputs a voltage command value Vc with the same frequency and the same phase as the AC signal vac. The current control unit 42 obtains the voltage command value Vc and the current command value Vc obtained by the voltage detector 23 ( Figure 2 )'s output signal VOf represents a deviation ΔV=Vc-VO of the AC output voltage VO, and generates a current control value Ic in such a way that the deviation ΔV is eliminated.

[0086] The voltage control unit 43 obtains the current control value Ic from the current control unit 42 and the current control value Ic from the current detector CD3 ( Figure 1 )'s output signal IOf represents a deviation ΔI=Ic-IO of the AC output current IO, and generates a voltage control value Vc1 in such a way that the deviation ΔI is eliminated.

[0087] The selector 45 controls the signal φ31 ( Figure 3 , Figure 4 ) is at the “H” level, the PWM control unit 44 is coupled to the inverter 8, and when the control signal φ31 is at the “L” level, the PWM control unit 54 is coupled to the inverter 8.

[0088] When the control signal φ31 is at the “H” level, the PWM control unit 44 is coupled to the inverter 8 via the selector 45. The PWM control unit 44 generates a PWM signal based on the voltage control value Vc1, and controls the inverter 8 with the PWM signal.

[0089] The calculation unit 50 compares the load current IL represented by the output signal ILf of the current detector CD4 and the threshold current Ith. When IL>Ith, the calculation unit 50 subtracts the threshold current Ith from the load current IL to obtain the auxiliary current Ia=IL-Ith, and outputs the signal Iaf representing the auxiliary current Ia to the current command unit 51. When IL≤Ith, the calculation unit 50 sets the auxiliary current Ia to 0A, and outputs the signal Iaf indicating that the auxiliary current Ia is 0A to the current command unit 51.

[0090] The current command unit 51 generates a current command value Ic1 having a value corresponding to the auxiliary current Ia indicated by the signal Iaf. The current command value Ic1 is a sinusoidal wave signal having the same frequency and phase as the load current IL.

[0091] The voltage control unit 52 obtains a deviation ΔI=Ic1-IO between the current command value Ic1 from the current command unit 51 and the AC output current IO of the inverter 8 indicated by the output signal Iof of the current detector CD3, and generates a voltage control value Vc2 so that the deviation ΔI is eliminated.

[0092] The current control unit 53 obtains the voltage control value Vc2 and compares it with the voltage detector 23 ( Figure 2 )'s output signal VOf represents a deviation ΔV of the AC output voltage VO = Vc2 - VO, and generates a current control value Ic2 in such a way that the deviation ΔV is eliminated.

[0093] When the control signal φ31 is at the "L" level, the PWM control unit 54 is coupled to the inverter 8 via the selector 45. The PWM control unit 54 generates a PWM signal based on the current command value Ic2, and controls the inverter 8 with the PWM signal.

[0094] Here, yes Figure 5 The operation of the control circuit 29 shown in FIG. Figure 3 ) When the semiconductor switch 1 is turned on and the control signal φ31 becomes “L” level, the PWM control unit 54 is coupled to the inverter 8 through the selector 45.

[0095] The calculation unit 50 compares the load current IL with the threshold current Ith, and generates a signal Iaf indicating that the auxiliary current Ia=IL-Ith when IL>Ith, and generates a signal Iaf indicating that the auxiliary current Ia is 0A when IL≤Ith.

[0096] The current command value Ic1 of the value corresponding to the auxiliary current Ia is generated by the current command unit 51, and the voltage command value Vc2 of the value corresponding to the deviation ΔI=Ic1-IO between the current command value Ic1 and the output current IO of the inverter 8 is generated by the voltage control unit 52. In addition, the current command value Ic2 of the value corresponding to the deviation ΔV=Vc2-VO between the voltage command value Vc2 and the AC output voltage VO is generated by the current control unit 53. The PWM control unit 54 controls the output current IO of the inverter 8 according to the current command value Ic2. As a result, the auxiliary current Ia is supplied from the inverter 8 to the load 14.

[0097] In addition, by the control unit 31 ( Figure 3 ) When the semiconductor switch 1 is turned off and the control signal φ31 becomes “H” level, the PWM control unit 44 is coupled to the inverter 8 through the selector 45.

[0098] The phase synchronization control unit 40 generates an AC signal vac with the same phase and frequency as the AC input voltage VI, and the voltage command unit 41 generates a voltage command value Vc with the same phase and frequency as the AC signal vac.

[0099] In addition, the current control unit 42 generates a current command value Ic corresponding to a deviation ΔV=Vc-VO between the voltage command value Vc and the AC output voltage VO. The voltage control unit 43 generates a voltage command value Vc1 corresponding to a deviation ΔI=Ic-IO between the current command value Ic and the output current IO of the inverter 8. The PWM control unit 44 controls the output voltage VO of the inverter 8 based on the voltage command value Vc1. Thus, even when the bypass AC power supply 11 fails, the AC voltage VO is supplied from the inverter 8 to the load 14, and the operation of the load 14 continues.

[0100] Figure 6 Yes means Figure 1 to Figure 5 However, in order to simplify the description, both AC power sources 11 and 12 are commercial AC power sources.

[0101] When the uninterruptible power supply is turned on using the operating unit 9 when the bypass AC power supply 11 is not faulty, the inverter auxiliary power supply mode is executed in step ST1. That is, the semiconductor switch 1 is turned on, the rectifier 4 is controlled so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR, and the bidirectional chopper 7 is controlled so that the battery voltage VB becomes the reference DC voltage VBR.

[0102] When the load current IL is equal to or lower than the threshold current Ith, the inverter 8 enters the standby state. When the load current IL exceeds the threshold current Ith, the inverter 8 supplies the auxiliary current Ia=IL-Ith to the load 14 .

[0103] In step ST2, it is determined whether a power failure has occurred in the bypass AC power supply 11, that is, whether the power failure detection signal φ26 is at the "L" level. If the signal φ26 is not at the "L" level, the inverter auxiliary power supply mode is continued in step ST1.

[0104] When the signal φ26 is at the "L" level, the battery power supply mode is executed in step ST3. That is, the semiconductor switch 1 is turned off, the switch S1 is turned off, and the operation of the rectifier 4 is stopped. In addition, the bidirectional chopper 7 is controlled so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR, and the AC voltage VO is supplied from the inverter 8 to the load 14 to operate the load 14.

[0105] In step ST4, it is determined whether the bypass AC power supply 11 has returned to a non-fault state, that is, whether the power failure detection signal φ26 is at an "H" level. If the signal φ26 is not at an "H" level, the battery power supply mode is continued in step ST3. If the signal φ26 is at an "H" level, the inverter auxiliary power supply mode is executed in step ST1.

[0106] Figure 7 This is a circuit block diagram for explaining the operation of the uninterruptible power supply device in the inverter auxiliary power supply mode. Figure 7 In order to simplify the drawings and description, the terminals T1 to T4, the current detectors CD1 to CD4, the operation unit 9, and the control device 10 are omitted. Figure 1 ). Figure 7 In FIG. 1 , arrows show the path of power supply.

[0107] In the inverter auxiliary power supply mode, the semiconductor switch 1 is turned on, and AC power is supplied from the bypass AC power supply 11 to the load 14 via the semiconductor switch 1. In addition, the switches S1 to S3 are turned on, and the AC power supplied from the AC power supply 12 is converted into DC power by the rectifier 4, and the DC power is stored in the battery 13 by the bidirectional chopper 7 and supplied to the inverter 8.

[0108] When load current IL is lower than threshold current Ith, inverter 8 enters standby mode and AC output current IO of inverter 8 is maintained at 0 A. When load current IL exceeds threshold current Ith, inverter 8 supplies auxiliary current Ia=IL-Ith corresponding to the excess to load 14.

[0109] Here, the capacity of the semiconductor switch 1, the capacity of the rectifier 4, the capacity of the bidirectional chopper 7, and the capacity of the inverter 8 are set to the same value. In addition, the power that can be supplied by the semiconductor switch 1, the rectifier 4, the bidirectional chopper 7, and the inverter 8 is set to 100%, and the power consumption of the load 14 is set to vary from 100% to 200%.

[0110] When the power consumption of the load 14 is 100%, 100% of the power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1. In this case, the power supplied from the inverter 8 to the load 14 is maintained at 0%.

[0111] If the power consumption of the load 14 fluctuates and exceeds 100%, 100% of the power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1 , and the excess power is supplied from the inverter 8 to the load 14 .

[0112] exist Figure 7, a case where the power consumption of the load 14 increases by 200% is shown. In this case, 100% of the power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1, and 100% of the power is supplied from the AC power source 12 to the inverter 8 via the rectifier 4, and 100% of the power is supplied from the inverter 8 to the load 14. It is assumed that the battery 13 is fully charged and the current flowing in the battery 13 is sufficiently small.

[0113] Figure 8 This is a circuit block diagram for explaining the operation of the uninterruptible power supply device in battery power supply mode. Figure 7 The battery power supply mode is executed when the AC power sources 11 and 12 are out of power.

[0114] In this case, the semiconductor switch 1 is turned off, the bypass AC power source 11 and the load 14 are disconnected, and the switch S1 is turned off, the AC power source 12 and the rectifier 4 are disconnected, and the operation of the rectifier 4 is stopped. In addition, 100% of the power is supplied from the battery 13 to the inverter 8 via the bidirectional chopper 7, and 100% of the power is supplied from the inverter 8 to the load 14.

[0115] Here, in order to clarify the effects of the present embodiment, a conventional uninterruptible power supply device will be described as a comparative example. Fig. 9 is a circuit block diagram for explaining the operation of the comparative example. Figure 7 Figure for comparison. Fig. 9 The difference between the comparative example and the present embodiment is that the semiconductor switch 1 is removed.

[0116] When the AC power supply 12 is not faulty, the inverter power supply mode is executed, switches S1 to S3 are turned on, and the AC power supplied from the AC power supply 12 is converted into DC power by the converter 4. The DC power is stored in the battery 13 by the bidirectional chopper 7, and is converted into AC power by the inverter 8 and supplied to the load 14.

[0117] exist Fig. 9 , the case where the power consumption of the load 14 is 100% is shown. In this case, 100% of the power is supplied from the AC power supply 12 to the inverter 8 via the rectifier 4, and 100% of the power is supplied from the inverter 8 to the load 14. It is assumed that the battery 13 is fully charged and the current flowing in the battery 13 is sufficiently small.

[0118] Fig.10 is a circuit block diagram for explaining other operations of the comparative example. Fig. 9 For comparison, see Figure 2. Fig.10In the embodiment, when the AC power source 12 fails, the battery power supply mode is executed. In this case, the switch S1 is turned off, the AC power source 12 is disconnected from the rectifier 4, and the operation of the rectifier 4 is stopped. In addition, direct current is supplied from the battery 13 to the inverter 8 via the bidirectional chopper 7, and the direct current is converted into alternating current by the inverter 8 and supplied to the load 14.

[0119] exist Fig.10 , the case where the power consumption of the load 14 is 100% is shown. In this case, 100% of the power is supplied from the battery 13 to the inverter 8 via the bidirectional chopper 7, and 100% of the power is supplied from the inverter 8 to the load 14.

[0120] Fig.11 FIG. 2 is a diagram for explaining the effect of this embodiment. Fig.11 In the figure, (A) is a graph showing the performance of the comparative example, and (B) is a graph showing the performance of the present embodiment. Fig.11 As shown in (A), the inverter power supply mode is executed when the AC power source 12 is not faulty. When the power consumption of the load 14 is 100%, that is, when the load factor is 100%, the load 14 can be stably operated (0 mark).

[0121] However, when the load factor increases to 125%, the temperature of the inverter 8 rises, and reaches the upper limit temperature within 10 minutes, for example. Therefore, the operation of the inverter 8 needs to be stopped, and the load 14 can only be operated for 10 minutes (△ mark). When the load factor increases to 150%, for example, since the temperature of the inverter 8 reaches the upper limit temperature within 1 minute, the load 14 can only be operated for 1 minute (△ mark). When the load factor increases to 200%, overcurrent is detected and the operation of the inverter 8 is stopped, and the power supply to the load 14 is stopped (× mark).

[0122] In addition, in the comparative example, the battery power supply mode is executed when the AC power source 12 fails. When the power consumption of the load 14 is 100%, that is, when the load factor is 100%, the operation of the load 14 can continue (0 mark). If the load factor exceeds 125%, an overcurrent is detected and the operation of the inverter 8 is stopped, and the power supply to the load 14 is stopped (× mark).

[0123] In contrast, in this embodiment, if Fig.11 As shown in (B), the inverter auxiliary power supply mode is executed when there is no fault in the AC power sources 11 and 12. When the load factor is 100%, since 100% of the power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1, the load 14 can be operated stably (0 mark).

[0124] In addition, when the load factor is 100-200%, 100% of the power is supplied from the bypass AC power supply 11 to the load 14 via the semiconductor switch 1, and the excess power of 0-100% is supplied from the AC power supply 12 to the load 14 via the rectifier 4 and the inverter 8, so that the load 14 can be operated stably (0 mark).

[0125] In addition, in the present embodiment, when the AC power sources 11 and 12 are powered off, the battery power supply mode is executed. When the load factor is 100%, the operation of the load 14 can continue (0 mark). If the load factor exceeds 125%, an overcurrent is detected and the operation of the inverter 8 is stopped, and the power supply to the load 14 is stopped (× mark). This point is the same as the comparative example.

[0126] As described above, in the present embodiment, when the load current IL of the bypass AC power source 11 is larger than the threshold current Ith during non-fault conditions, the auxiliary current Ia=IL-Ith, which is the difference between the load current IL and the threshold current Ith, is supplied from the inverter 8 to the load 14. Therefore, even when the load current IL increases due to load fluctuations, the current flowing in the semiconductor switch 1 can be maintained below the threshold current Ith, and overheating of the semiconductor switch 1 can be prevented. Therefore, it is possible to prevent the semiconductor switch 1 from being disconnected and the operation of the load 14 from being stopped, and an uninterruptible power supply device that can cope with strong load fluctuations can be realized. In addition, since it is not necessary to use a large-capacity semiconductor switch 1 in order to increase the load current IL, the device can be miniaturized and cost-effective.

[0127] Fig.12 is a circuit block diagram showing a modified example of the embodiment, and is Figure 7 Figure for comparison. Fig.12 This modification example is different from the embodiment in that rectifier 4A replaces rectifier 4. The capacity (i.e., size) of rectifier 4A is reduced to X% of the capacity (i.e., size) of rectifier 4, where X is a real number greater than 0 and less than 100. Fig.12 , the case where X=50 is shown.

[0128] exist Fig.12 In the inverter auxiliary power supply mode, when the AC power sources 11 and 12 are not faulty, the inverter auxiliary power supply mode is executed. When the load factor is 100%, 100% of the power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1. In addition, when the load factor increases to 150%, 100% of the power is supplied from the bypass AC power source 11 to the load 14 via the semiconductor switch 1, and the excess 50% of the power is supplied from the AC power source 12 to the load 14 via the rectifier 4 and the inverter 8.

[0129] In this modification, the size of the rectifier can be reduced compared to the embodiment, and the size of the device can be reduced.

[0130] The embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0131] Description of Reference Numerals

[0132] T1 bypass input terminal, T2 input terminal, T3 DC terminal, T4 output terminal, 1 semiconductor switch, 2, 3 thyristors, S1~S3 switches, 4 rectifiers, CD1~CD4 current detectors, 5 DC line, 6 capacitors, 7 bidirectional choppers, 8 inverters, 9 operating units, 10 control devices, 11 bypass AC power supply, 12 AC power supply, 13 batteries, 14 loads, 21~25 voltage detectors, 26, 27 power failure detectors, 28 synchronization detectors, 29 control circuits, 31 control units, 40 phase synchronization control units, 41 voltage command units, 42, 53 current control units, 43, 52 voltage control units, 44, 54 PWM control units, 45 selectors, 50 calculation units, 51 current command units.

Claims

1. An uninterruptible power supply device, comprising: a semiconductor switch connected between the first AC power source and the load, turned on when the first AC power source is not faulty, and turned off when the first AC power source is faulty; and The inverter converts the DC power supplied from the DC power supply into AC power and supplies it to the load when the first AC power supply fails, and supplies an auxiliary current equal to the difference between the load current and the threshold current to the load when the load current is greater than a threshold current when the first AC power supply is not faulty.

2. The uninterruptible power supply device according to claim 1, wherein: The threshold current is set to be less than or equal to a rated current of the semiconductor switch.

3. The uninterruptible power supply device according to claim 1, wherein: When the load current is smaller than the threshold current when the first AC power source is not faulty, the inverter enters a standby state in which the inverter does not receive or output current to or from the first AC power source and the load.

4. The uninterruptible power supply device according to claim 3, wherein: The DC power supply comprises: a rectifier for converting the AC power supplied from the second AC power source into DC power; and Power storage device, storing direct current, When the load current is smaller than the threshold current when the first AC power source and the second AC power source are not faulty, the DC power generated by the rectifier is stored in the power storage device, and the inverter enters the standby state. When the load current is larger than the threshold current when the first AC power source and the second AC power source are not faulty, the inverter generates the auxiliary current based on the DC power generated by the rectifier. When the first AC power source and the second AC power source fail, the DC power of the power storage device is converted into AC power by the inverter and supplied to the load.

5. The uninterruptible power supply device according to claim 4, wherein: The capacity of the rectifier is set smaller than the capacity of the inverter.

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