WO2017187553A1

WO2017187553A1 - Uninterruptible power supply apparatus

Info

Publication number: WO2017187553A1
Application number: PCT/JP2016/063194
Authority: WO
Inventors: 益永　博史; 一大日永田
Original assignee: 東芝三菱電機産業システム株式会社
Priority date: 2016-04-27
Filing date: 2016-04-27
Publication date: 2017-11-02
Also published as: CN109075605A; JP6585833B2; KR102118277B1; CN109075605B; KR20180132869A; JPWO2017187553A1

Abstract

A control circuit (14) of this uninterruptible power supply apparatus turns a contactor (10) ON, turns a thyristor switch (16) OFF, and performs controlling so as to cause an inverter (7) to supply a reactive current to a reactor (8) and a capacitor (9), and cause a load (54) to supply a driving current, in an inverter power supply mode. When the mode is shifted from the inverter power supply mode to a bypass power supply mode, the control circuit turns the thyristor switch ON, performs controlling so as to cause the inverter to stop supplying the reactive current to the capacitor, and turns the contactor OFF when the detection value by a current detector (CD 3) is greater than a threshold current (Ith).

Description

Uninterruptible power system

The present invention relates to an uninterruptible power supply, and more particularly to an uninterruptible power supply having an inverter power supply mode for supplying AC power generated by an inverter to a load and a bypass power supply mode for supplying AC power from an AC power supply to the load. .

Japanese Patent Application Laid-Open No. 11-4544 (Patent Document 1) discloses an inverter that converts DC power supplied from a DC power source into AC power, a first switch connected between the inverter and a load, an AC power source, An uninterruptible power supply comprising a second switch connected between loads is disclosed. In the inverter power supply mode, the first switch is turned on, and AC power is supplied from the inverter to the load via the first switch. In the bypass power supply mode, the second switch is turned on, and AC power is supplied from the AC power source to the load via the second switch. In the transition period in which the inverter power supply mode shifts to the bypass power supply mode, the first switch is turned off after the second switch is turned on in addition to the first switch.

Japanese Patent Laid-Open No. 11-4544

However, in Patent Document 1, when shifting from the inverter power supply mode to the bypass power supply mode, if the second switch fails and does not turn on, the AC power to the load is turned off when the first switch is turned off. There is a problem that the supply is stopped and the operation of the load is stopped.

As a countermeasure, a method may be considered in which a current detector for detecting the current flowing through the second switch is provided, and the first switch is turned off after confirming that the current has flowed through the second switch. However, with this method, when the load current is small, it is not possible to accurately and quickly determine whether or not current is flowing through the second switch, and it is possible to quickly shift from the inverter power supply mode to the bypass power supply mode. There is a problem that you can not.

Therefore, a main object of the present invention is to provide an uninterruptible power supply capable of quickly shifting from the inverter power supply mode to the bypass power supply mode even when the load current is small.

An uninterruptible power supply according to the present invention is an uninterruptible power supply that supplies AC power to a load using power supplied from a DC power supply or a first AC power supply, the DC power supplied from the DC power supply. An inverter for converting AC power into AC power, a reactor having one terminal connected to the output terminal of the inverter, a capacitor connected to the other terminal of the reactor, and a first connected between the other terminal of the reactor and the load A switch, a second switch connected between the first AC power source and the load, a current detector for detecting a current flowing through the second switch, an inverter based on a detection value of the current detector, 1 and a control circuit for controlling the second switch. In the inverter power supply mode in which AC power generated by the inverter is supplied to the load, the control circuit turns on the first switch, turns off the second switch, and controls the inverter to supply reactive current to the reactor and the capacitor. And a drive current is supplied to the load. In the bypass power supply mode in which AC power from the first AC power source is supplied to the load via the second switch, the control circuit turns off the first switch, turns on the second switch, and controls the inverter. To supply reactive current to the reactor and capacitor. In the transition period from the inverter power supply mode to the bypass power supply mode, the control circuit turns on the second switch, controls the inverter to reduce the reactive current supplied to the capacitor, and the detection value of the current detector is predetermined. In response to exceeding the threshold value, the first switch is turned off, and the inverter is controlled to increase the reactive current supplied to the capacitor.

In the uninterruptible power supply according to the present invention, the second switch is turned on during the transition period from the inverter power supply mode to the bypass power supply mode, and the reactive current supplied from the inverter to the capacitor is reduced. When the second switch is normal, a reactive current flows from the second AC power source to the capacitor via the second switch and the first switch, and from the second AC power source via the second switch. Drive current flows through the load. Therefore, since the reactive current to the capacitor and the drive current to the load flow through the second switch, it is possible to secure the current flowing through the second switch even when the load current is small. Therefore, it is possible to accurately and quickly determine whether or not current is flowing through the second switch, and it is possible to quickly shift from the inverter power supply mode to the bypass power supply mode.

It is a circuit block diagram which shows the structure of the uninterruptible power supply by one embodiment of this invention. 2 is a flowchart showing an operation of a control circuit 14 shown in FIG. It is a time chart which shows the specific example 1 of the transfer operation | movement from an inverter electric power feeding mode to a bypass electric power feeding mode. It is a time chart which shows the comparative example 1 of the transfer operation | movement from an inverter electric power feeding mode to a bypass electric power feeding mode. It is a time chart which shows the specific example 2 of the transfer operation | movement from an inverter electric power feeding mode to a bypass electric power feeding mode. It is a time chart which shows the comparative example 2 of the transfer operation | movement from inverter electric power feeding mode to bypass electric power feeding mode.

FIG. 1 is a circuit block diagram showing a configuration of an uninterruptible power supply according to an embodiment of the present invention. In FIG. 1, the uninterruptible power supply device includes an input terminal T1, a bypass terminal T2, a DC terminal T3, and an output terminal T4.

The input terminal T1 is connected to the AC power source 51. The AC power source 51 may be a commercial AC power source or a private generator. The AC power supply 51 supplies, for example, commercial frequency AC power to the uninterruptible power supply. The bypass terminal T2 is connected to the bypass AC power source 52. The bypass AC power source may be a commercial AC power source or a private generator. The bypass terminal T2 may be connected to the AC power source 51 together with the input terminal T1.

The DC terminal T3 is connected to the storage battery 53 (power storage device). The storage battery 53 stores DC power. The storage battery 53 is charged when AC power is normally supplied from the AC power source 51, and is discharged when AC power is not normally supplied from the AC power source 51 (for example, during a power failure). A capacitor may be connected instead of the storage battery 53. The storage battery 53 may be included in the uninterruptible power supply. The output terminal T4 is connected to the load 54. The load 54 is driven by, for example, commercial frequency AC power supplied from the uninterruptible power supply.

This uninterruptible power supply further includes

contactors

1, 10, 12, fuse 2,

reactors

3, 8, converter 4, DC bus 5, capacitors 6, 9, inverter 7, current detectors CD 1 -CD 3, bidirectional chopper 11 ,

Control circuits

13 and 14, an operation unit 15, and a thyristor switch 16.

Contactor 1, fuse 2, and reactor 3 are connected in series between input terminal T 1 and the input terminal of converter 4. The contactor 1 is turned on when the uninterruptible power supply is used, and is turned off during maintenance of the uninterruptible power supply, for example. The fuse 2 is blown when an overcurrent flows to protect the uninterruptible power supply. Reactor 3 allows commercial frequency AC power from AC power supply 51 to pass through converter 4 and prohibits the passage of switching frequency signals generated by converter 4.

Converter 4 receives AC power supplied from AC power supply 51 via contactor 1, fuse 2, and reactor 3. The converter 4 is controlled by the control circuit 13 and, when AC power is normally supplied from the AC power source 51, converts the AC power from the AC power source 51 into DC power and outputs it to the output terminal. When AC power is not normally supplied from AC power supply 51 (that is, during a power failure), operation of converter 4 is stopped.

The DC bus 5 is connected between the output terminal of the converter 4 and the input terminal of the inverter 7 to transmit DC power. Capacitor 6 is connected to DC bus 5 and stabilizes DC voltage VDC of DC bus 5. The capacitor 6 is connected between the DC bus 5 and, for example, a neutral point (or a reference voltage line). The inverter 7 is controlled by the control circuit 14 and converts the DC power received from the DC bus 5 into AC power and outputs it to the output terminal. The current detector CD1 detects the output current I1 of the inverter 7 and outputs a signal indicating the detected value to the control circuit 14.

The reactor 8 is connected between the output terminal of the inverter 7 and one terminal of the contactor 10. The capacitor 9 is connected between one terminal of the contactor 10 and, for example, a neutral point (or a reference voltage line). The other terminal of the contactor 10 is connected to the output terminal T4.

Reactor 8 and capacitor 9 constitute a low-pass filter, which passes, for example, commercial frequency AC power generated by inverter 7 and prohibits the passage of switching frequency signals generated by inverter 7. In other words, the reactor 8 and the capacitor 9 convert the rectangular wave AC voltage output from the inverter 7 into a sinusoidal AC voltage.

The contactor 10 is controlled by the control circuit 14 and is turned on in the inverter power supply mode for supplying AC power from the inverter 7 to the load 54, and supplies AC power from the bypass AC power source 52 to the load 54 via the thyristor switch 16. It is turned off in the bypass power supply mode. The contactor 10 constitutes a first switch. The current detector CD2 detects a current (that is, a load current) I2 flowing through the load 54, and outputs a signal indicating the detected value to the control circuit 14.

The bidirectional chopper 11 and the contactor 12 are connected in series between the DC bus 5 and the DC terminal T3. The contactor 12 is turned on when the uninterruptible power supply is used, and is turned off, for example, when the storage battery 53 is maintained. The bidirectional chopper 11 is controlled by the control circuit 13, and when the AC power is normally supplied from the AC power source 51, the DC power received from the DC bus 5 is stored in the storage battery 53, and the AC power is received from the AC power source 51. When not normally supplied (that is, at the time of a power failure), the DC power of the storage battery 53 is supplied to the DC bus 5. The bidirectional chopper 11 steps down the DC voltage VDC of the DC bus 5 and stores it in the storage battery 53, boosts the voltage between the terminals of the storage battery 53, and gives it to the DC bus 5.

The control circuit 13 controls the converter 4 and the bidirectional chopper 11 based on the AC voltage VAC supplied from the AC power source 51. For example, the control circuit 13 detects the voltage of the node between the fuse 2 and the reactor 3 as the AC voltage VAC.

When the AC voltage VAC is normal (that is, when AC power is normally supplied from the AC power supply 51), the control circuit 13 controls the converter 4 to convert AC power into DC power and The bidirectional chopper 11 is controlled so that a current flows from the bus 5 to the storage battery 53, and the storage battery 53 is charged.

When the AC voltage VAC is not normal (that is, when AC power is not normally supplied from the AC power supply 51), the control circuit 13 stops the operation of the converter 4 and directs DC from the storage battery 53 to the DC bus 5. The bidirectional chopper 11 is controlled so that a current flows, and the storage battery 53 is discharged.

The thyristor switch 16 is connected between the bypass terminal T2 and the other terminal of the contactor 10, and is controlled by the control circuit 14. The thyristor switch 16 includes two thyristors. The anode and cathode of one thyristor are connected to the bypass terminal T2 and the other terminal of the contactor 10, respectively, and the anode and cathode of the other thyristor are connected to the other terminal of the contactor 10 and the bypass terminal T2, respectively.

The thyristor switch 16 is turned on in the bypass power supply mode and turned off in the inverter power supply mode. Further, the thyristor switch 16 is instantly turned on when the inverter 7 fails. When the thyristor switch 16 is turned on, AC power is supplied from the bypass AC power supply 52 to the load 54 via the thyristor switch 16. The thyristor switch 16 constitutes a second switch. The current detector CD3 detects the current I3 flowing through the thyristor switch 16, and outputs a signal indicating the detected value to the control circuit 14.

The operation unit 15 includes a plurality of buttons operated by the user of the uninterruptible power supply. The user operates the operation unit 15 to start or stop the uninterruptible power supply, execute the inverter power supply mode, or execute the bypass power supply mode. The operation unit 15 outputs a signal indicating the operation result of the user to the control circuit 14.

The control circuit 14 controls the inverter 7, the contactor 10, and the thyristor switch 16 based on the output signal of the operation unit 15, the output signals of the current detectors CD1 to CD3, and the like. The control circuit 14 executes the power feeding mode selected using the operation unit 15 of the inverter power feeding mode and the bypass AC power source 52.

When the inverter power supply mode is selected using the operation unit 15 (that is, in the inverter power supply mode), the control circuit 14 turns on the contactor 10, turns off the thyristor switch 16, controls the inverter 7, and controls the reactor 8 In addition, the reactive current is supplied to the capacitor 9 and the driving current is supplied to the load 54.

When the bypass power supply mode is selected using the operation unit 15 (that is, in the bypass power supply mode), the control circuit 14 turns off the contactor 10, turns on the thyristor switch 16, controls the inverter 7, and controls the reactor 8 And the reactive current is supplied to the capacitor 9. In this case, the inverter 7 does not supply a drive current to the load 54.

The control circuit 14 turns on the thyristor switch 16 when the bypass power supply mode is selected using the operation unit 15 during the execution of the inverter power supply mode (that is, when shifting from the inverter power supply mode to the bypass power supply mode), The inverter 7 is controlled to stop the supply of reactive current to the capacitor 9. Further, the control circuit 14 turns off the contactor 10 in response to the detection value of the current detector CD3 exceeding a predetermined threshold value, and controls the inverter 7 to resume the supply of the reactive current to the capacitor 9. Let

FIG. 2 is a flowchart showing the operation of the control circuit 14 when shifting from the inverter power supply mode to the bypass power supply mode. In the inverter power supply mode, the thyristor switch 16 is turned off, the contactor 10 is turned on, and the inverter 7 passes the reactive current −jI8 to the reactor 8, passes the reactive current jI9 to the capacitor 9, and supplies the drive current IL to the load 54. It shall be. Therefore, the output current I1 of the inverter 7 is I1 = IL−jI8 + jI9.

In step S1, the control circuit 14 determines whether or not the bypass power supply mode is selected based on the signal from the operation unit 15, and waits until the bypass power supply mode is selected. When the bypass power supply mode is selected in step S1, the control circuit 14 outputs an on command signal φ16 to the thyristor switch 16 in step S2.

When the thyristor switch 16 is normal, the thyristor switch 16 is turned on in response to the on command signal φ16. In this case, the load current IL is supplied from the bypass AC power supply 52 to the load 54 via the thyristor switch 16, and the output current I1 of the inverter 7 decreases to -jI8 + jI9. At this time, the load current IL is detected by the current detector CD3. When the load current IL is small, the control circuit 14 accurately and quickly determines whether or not the load current IL has flown through the thyristor switch 16. There is a risk of not being able to.

When the thyristor switch 16 is out of order, the thyristor switch 16 is not turned on in response to the on command signal φ16. In this case, the output current I1 of the inverter 7 remains unchanged as I1 = IL−jI8 + jI9, and the load current IL is not detected by the current detector CD3.

In step S3, the control circuit 14 controls the inverter 7 to reduce the reactive current jI9 flowing through the capacitor 9 to 0 A and to reduce the output current I1 of the inverter 7 to IL-jI8. When the thyristor switch 16 is normally turned on, the load current IL is supplied from the bypass AC power supply 52 via the thyristor switch 16 to the load 54 and from the bypass AC power supply 52 via the thyristor switch 16 and the contactor 10. Thus, the reactive current jI9 is supplied to the capacitor 9.

Thereby, the current I3 flowing through the thyristor switch 16 increases to IL + jI9, and the output current I1 of the inverter 7 decreases to -jI8. Therefore, even when the load current IL is small, the amount of current flowing through the thyristor switch 16 can be ensured. Therefore, the control circuit 14 can accurately determine whether or not the load current IL and the reactive current jI9 have flowed through the thyristor switch 16. It is possible to quickly determine.

When the thyristor switch 16 is broken and turned off, the thyristor switch 16 is not turned on in response to the on command signal φ16. In this case, the output current I1 of the inverter 7 decreases to IL-jI8, and the load current IL is not detected by the current detector CD3.

In step S4, the control circuit 14 determines whether or not the current I3 flowing through the thyristor switch 16 is larger than the threshold current Ith based on the detection result of the current detector CD3. This threshold current Ith is set to a value smaller than the current I3 = IL + jI9 flowing through the thyristor switch 16 when the thyristor switch 16 is actually turned on and the reactive current jI9 is reduced from the output current I1 of the inverter 7. Yes. Therefore, when the thyristor switch 16 is normal (that is, when it is actually turned on), I3> Ith, and when the thyristor switch 16 is out of order (that is, when it is not turned on), I3 = 0 <Ith.

When I3> Ith in step S4 (that is, when the thyristor switch 16 is turned on), in step S5, the control circuit 14 controls the inverter 7 to increase the reactive current jI9 flowing through the capacitor 9 to a predetermined value jIR. Let In step S6, the control circuit 14 turns off the contactor 10. As a result, the load current IL is supplied from the bypass AC power supply 52 to the load 54 via the thyristor switch 16, and the load 54 is driven.

In step S7, the control circuit 14 outputs a signal for notifying the user of the uninterruptible power supply that the transition from the inverter power supply mode to the bypass power supply mode is completed, and ends the process. You may provide the apparatus which notifies the user of an uninterruptible power supply that the transition from inverter electric power feeding mode to bypass electric power feeding mode is completed using a sound, light, an image, etc., for example.

When I3> Ith is not satisfied in step S4 (that is, when the thyristor switch 16 is not turned on), in step S8, the control circuit 14 controls the inverter 7 to increase the reactive current jI9 flowing through the capacitor 9 to a predetermined value jIR. . Thereby, the inverter power supply mode is continued, and the operation of the load 54 is continued. In step S9, the control circuit 14 outputs a signal for notifying the user of the uninterruptible power supply that a failure has occurred in the thyristor switch 16, and ends the process. A device may be provided that notifies the user of the uninterruptible power supply that a failure has occurred in the thyristor switch 16 using, for example, sound, light, or an image.

[Specific Example 1]
3A to 3L are time charts showing a specific example 1 of the transition operation from the inverter power supply mode to the bypass power supply mode. In particular, FIG. 3A shows an ON command signal CON for turning on the thyristor switch 16, and FIG. 3B shows an ON determination signal DON that defines a period for determining whether or not the thyristor switch 16 is ON. FIG. 3C shows an off command signal COFF for turning off the contactor 10.

3D and 3E respectively show the effective current I3cosθ and the reactive current I3sinθ of the current I3 flowing through the thyristor switch 16. FIGS. 3F and 3G show the effective current I1 cos θ and the reactive current I1 sin θ, respectively, of the output current I1 of the inverter 7. 3 (h) and 3 (i) show the effective current I2cosθ and the reactive current I2sinθ, respectively, of the current I2 flowing through the load 54.

FIG. 3J shows a current vector I3v = I3cosθ + jI3sinθ flowing through the thyristor switch 16. FIG. 3K shows the output current vector I1v = I1cos θ + jI1sin θ of the inverter 7. FIG. 3 (l) shows the current vector I2v = I2cos θ + jI2sin θ flowing through the load 54.

3 (a) to 3 (l) show a case where only the effective current I2cosθ = IL flows through the load 54. FIG. In the inverter power supply mode, the thyristor switch 16 is turned off, the contactor 10 is turned on, and the inverter 7 supplies the reactor 8, the capacitor 9, and the load 54 with a reactive current (-jI8), a reactive current (jI9), and an effective current ( IL).

In the inverter power supply mode, the ON command signal CON, the ON determination signal DON, and the OFF command signal COFF are all set to the inactivation level “L” level (see FIGS. 3A to 3C). The flowing current I3 is 0 A (see FIGS. 3D, 3E, and 3J). The inverter 7 outputs an effective current (I1 cos θ = IL) and a reactive current (I1 sin θ = −jI8 + jI9) (FIGS. 3 (f) (g) (k)). Only an effective current (I2cos θ = IL) flows through the load 54, and a reactive current (I2sin θ = 0) does not flow (see FIGS. 3 (h), (i), and (l)).

In the transition period from the inverter power supply mode to the bypass power supply mode, the ON command signal CON is first set to the “H” level of the activation level, and the supply of the reactive current (jI9) from the inverter 7 to the capacitor 9 is stopped. (See FIGS. 3A and 3G).

When the thyristor switch 16 is normal, the thyristor switch 16 is actually turned on in response to the ON command signal CON. When the thyristor switch 16 is out of order, the thyristor switch 16 is not turned on in response to the ON command signal CON. 3A to 3L show a case where the thyristor switch 16 is normal.

When the thyristor switch 16 is turned on, a reactive current (I3sinθ = I9) flows from the bypass AC power supply 52 to the capacitor 9 via the thyristor switch 16 and the contactor 10 (see FIG. 3E). Furthermore, an effective current (I3 cos θ = IL) flows from the bypass AC power source 52 to the load 54 via the thyristor switch 16, and an effective current (I1 cos θ = IL) flowing from the inverter 7 to the load 54 decreases (FIG. 3D). (Refer to (f) (j) (k) (l)).

Next, the ON command signal CON is lowered to the “L” level of the inactivation level, and the ON determination signal DON is raised to the “H” level of the activation level, so that the thyristor switch 16 is turned on. Is determined (see FIGS. 3A and 3B). The control circuit 14 determines whether or not the current I3 = IL + jI9 detected by the current detector CD3 is larger than the threshold current Ith (see FIGS. 3B, 3D, and 3E).

Here, since I3> Ith, the ON determination signal DON is lowered to the “L” level of the inactivation level, and the OFF command signal COFF is raised to the “H” level of the activation level. Is turned off (see FIGS. 3B and 3C). When the contactor 10 is turned off, the supply of the reactive current (I1sinθ = I9) from the inverter 7 to the capacitor 9 is resumed, and the supply of the reactive current (I3sinθ = I9) from the bypass AC power supply 52 to the capacitor 9 is stopped. The transition to the bypass power supply mode is completed (see FIGS. 3 (e), (g), (j), (k), and (l)).

[Comparative Example 1]
4 (a) to 4 (l) are time charts showing a comparative example 1 of the transition operation from the inverter power supply mode to the bypass power supply mode, and are compared with FIGS. 3 (a) to 3 (l). . Referring to FIGS. 4A to 4L, the comparative example 1 is different from the specific example 1 of FIGS. 3A to 3I in that the reactive current (I9) is supplied from the inverter 7 to the capacitor 9. (See FIGS. 4G and 4K.) For this reason, if the load current IL flowing through the thyristor switch 16 is small during the ON determination period, it may not be possible to accurately and quickly determine whether or not the current is flowing through the thyristor switch 16 (FIG. 4 ( b) (d) (see e)).

In contrast, in the first specific example, the supply of the reactive current (I9) from the inverter 7 to the capacitor 9 is stopped during the transition period, and the reactive current (I9) is supplied from the bypass AC power supply 52 to the capacitor 9 via the thyristor switch 16. Therefore, even when the load current IL is small, it is possible to accurately and quickly determine whether or not a current is flowing through the thyristor switch 16 (see FIGS. 3B, 3D, and 3E).

[Specific Example 2]
FIGS. 5A to 5L are time charts showing another specific example 2 of the transition operation from the inverter power supply mode to the bypass power supply mode, and are compared with FIGS. 3A to 3L. It is. Referring to FIGS. 5A to 5L, Specific Example 2 is different from Specific Example 1 of FIGS. 3A to 3I in that effective current (IL) and reactive current (− IA) flows, and the sum (I9-IA) of the reactive current (-IA) flowing through the load 54 and the reactive current (I9) flowing through the capacitor 9 becomes substantially zero. In other words, the reactive current (IA) generated in the load 54 and the reactive current (I9) flowing through the capacitor 9 are substantially equal.

In the inverter power supply mode, the thyristor switch 16 is turned off, the contactor 10 is turned on, and the inverter 7 supplies a reactive current (−I8) and a reactive current (I9) to the reactor 8 and the capacitor 9, respectively, and is effective to the load 54. Supply current (IL) and reactive current (-IA).

In the inverter power supply mode, the ON command signal CON, the ON determination signal DON, and the OFF command signal COFF are all set to the inactivation level “L” level (see FIGS. 5A to 5C), and the thyristor switch 16 The flowing current I3 is 0 A (see FIGS. 5D, 5E, and 5J). The inverter 7 outputs an effective current (I1cosθ = IL) and a reactive current (I1sinθ = −I8 + I9−IA) (FIGS. 5 (f) (g) (k)). An effective current (I2 cos θ = IL) and a reactive current (I2 sin θ = −IA) flow through the load 54 (see FIGS. 5 (h), (i), and (l)).

In the transition period from the inverter power supply mode to the bypass power supply mode, the ON command signal CON is first set to the “H” level of the activation level, and the supply of the reactive current (jI9) from the inverter 7 to the capacitor 9 is stopped. (See FIGS. 5A and 5G).

When the thyristor switch 16 is normal, the thyristor switch 16 is actually turned on in response to the ON command signal CON. When the thyristor switch 16 is out of order, the thyristor switch 16 is not turned on in response to the ON command signal CON. 5A to 5L show a case where the thyristor switch 16 is normal.

When the thyristor switch 16 is turned on, a reactive current (I3sinθ = I9) flows from the bypass AC power supply 52 to the capacitor 9 via the thyristor switch 16 and the contactor 10 (see FIG. 5E). Further, an effective current (I3 cos θ = IL) flows from the bypass AC power source 52 to the load 54 via the thyristor switch 16, and an effective current (I1 cos θ = IL) flowing from the inverter 7 to the load 54 decreases (FIG. 5D). (Refer to (f) (j) (k) (l)).

Next, the ON command signal CON is lowered to the “L” level of the inactivation level, and the ON determination signal DON is raised to the “H” level of the activation level, so that the thyristor switch 16 is turned on. Is determined (see FIGS. 5A and 5B). The control circuit 14 determines whether or not the current I3 = IL + jI9 detected by the current detector CD3 is larger than the threshold current Ith (see FIGS. 5B, 5D, and 5E).

Here, since I3> Ith, the ON determination signal DON is lowered to the “L” level of the inactivation level, and the OFF command signal COFF is raised to the “H” level of the activation level. Is turned off (see FIGS. 5B and 5C). When the contactor 10 is turned off, the supply of the reactive current (I3sinθ = I9) from the bypass AC power supply 52 to the capacitor 9 is stopped, the supply of the reactive current (I1sinθ = I9) from the inverter 7 to the capacitor 9 is resumed, The transition to the bypass power supply mode is completed (see FIGS. 5 (e), (g), (j), (k), and (l)).

[Comparative Example 2]
FIGS. 6A to 6L are time charts showing a comparative example 2 of the transition operation from the inverter power supply mode to the bypass power supply mode, and are compared with FIGS. 5A to 5L. . With reference to FIGS. 6A to 6L, the comparative example 2 is different from the specific example 2 of FIGS. 5A to 5I in that the reactive current from the inverter 7 to the capacitor 9 is changed during the transition period. After the supply of (I9) is stopped, the supply of the reactive current (-IA) from the inverter 7 to the load 54 is further stopped (see FIGS. 6 (g) and (k)).

When the supply of the reactive current (I9-IA) from the inverter 7 to the capacitor 9 and the load 54 is stopped, the reactive current (I9-IA) is supplied from the bypass AC power source 52 to the capacitor 9 and the load 54. Here, since I9−IA≈0 A, only the effective current IL of the load current I3 flows through the thyristor switch 16. Therefore, if the load current IL flowing through the thyristor switch 16 is small during the ON determination period, it may not be possible to accurately and quickly determine whether or not the current is flowing through the thyristor switch 16 (FIG. 6 ( b) (d) (see e)).

In contrast, in the specific example 2, the supply of the reactive current (I9) from the inverter 7 to the capacitor 9 is stopped during the transition period, and the reactive current (I9) is supplied from the bypass AC power supply 52 to the capacitor 9 via the thyristor switch 16. Therefore, even when I9≈IA and the load current IL is small, it is possible to accurately and quickly determine whether or not current is flowing through the thyristor switch 16 (FIGS. 5B and 5D). e)).

As described above, in this embodiment, the thyristor switch 16 is turned on and the supply of the reactive current from the inverter 7 to the capacitor 9 is stopped during the transition period from the inverter power supply mode to the bypass power supply mode. When the thyristor switch 16 is normal, a reactive current flows from the bypass AC power source 52 to the capacitor 9 via the thyristor switch 16 and the contactor 10, and current flows from the bypass AC power source 52 to the load 54 via the thyristor switch 16. Flowing. Therefore, since the reactive current to the capacitor 9 and the load current to the load 54 flow through the thyristor switch 16, whether or not the current is flowing through the thyristor switch 16 is determined accurately and quickly even when the load current is small. The inverter power supply mode can be quickly shifted to the bypass power supply mode.

Furthermore, since only the thyristor switch 16 is connected between the bypass terminal T2 and the output terminal T4, the apparatus can be downsized as compared with the case where the thyristor switch 16 and the contactor are connected in parallel between the bypass terminal T2 and the output terminal T4. be able to.

In the present embodiment, the supply of the reactive current I9 to the capacitor 9 is stopped at the time of transition from the inverter power supply mode to the bypass power supply mode. However, the present invention is not limited to this, and the reactive current I9 supplied to the capacitor 9 is For example, it may be decreased by several tens of percent. Even in this case, since the reduced reactive current I9 flows through the thyristor switch 16, it can be easily and accurately determined whether or not the current is flowing through the thyristor switch 16.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

T1 input terminal, T2 bypass terminal, T3 DC terminal, T4 output terminal, 1,10,12 contactor, 2 fuse, 3,8 reactor, 4 converter, 5 DC bus, 6,9 capacitor, 7 inverter, CD1 to CD3 current Detector, 11 bidirectional chopper, 13, 14 control circuit, 15 operation unit, 16 thyristor switch, 51 AC power source, 52 bypass AC power source, 53 storage battery, 54 load.

Claims

An uninterruptible power supply that supplies AC power to a load using power supplied from a DC power source or a first AC power source,
An inverter that converts DC power supplied from the DC power source into AC power;
A reactor having one terminal connected to the output terminal of the inverter;
A capacitor connected to the other terminal of the reactor;
A first switch connected between the other terminal of the reactor and the load;
A second switch connected between the first AC power source and the load;
A current detector for detecting a current flowing through the second switch;
A control circuit for controlling the inverter, the first switch, and the second switch based on a detection value of the current detector;
In an inverter power supply mode for supplying AC power generated by the inverter to the load, the control circuit turns on the first switch, turns off the second switch, controls the inverter, and controls the reactor. And a reactive current to the capacitor and a drive current to the load,
In the bypass power supply mode in which AC power from the first AC power supply is supplied to the load via the second switch, the control circuit turns off the first switch and turns on the second switch. And controlling the inverter to supply reactive current to the reactor and the capacitor,
In the transition period in which the inverter power supply mode shifts to the bypass power supply mode, the control circuit turns on the second switch, controls the inverter to reduce the reactive current supplied to the capacitor, and the current detector An uninterruptible power supply that turns off the first switch in response to a detected value exceeding a predetermined threshold value to increase the reactive current supplied to the capacitor by controlling the inverter.
In the transition period, the control circuit turns on the second switch, controls the inverter to stop the supply of reactive current to the capacitor, and a detection value of the current detector is set to a predetermined threshold. 2. The uninterruptible power supply according to claim 1, wherein when the value is exceeded, the first switch is turned off, and the inverter is controlled to restart the supply of reactive current to the capacitor.
In the transition period, when the detection value of the current detector is smaller than the predetermined threshold, the control circuit drives the inverter to the load without turning off the first switch. The uninterruptible power supply according to claim 1 which continues supply of current.
In the transition period, when the detection value of the current detector is smaller than the predetermined threshold, the control circuit indicates that a failure has occurred without turning off the first switch. The uninterruptible power supply according to claim 1 which outputs a signal.
The uninterruptible power supply according to claim 1, wherein the second switch includes a thyristor switch that is turned on during the transition period and the bypass power supply mode.
The uninterruptible power supply uses the power supplied from the DC power supply, the first AC power supply, or the second AC power supply to supply AC power to a load,
The DC power supply is
A converter that converts AC power from the second AC power source into DC power;
A power storage device for storing DC power generated by the converter,
The uninterruptible power supply according to claim 1, wherein the inverter converts DC power generated by the converter or DC power of the power storage device into AC power.