Power supply device

Abstract

The uninterruptible power supply device has: a bypass circuit (1) and a plurality of vacuum circuit breakers (S1, S2) connected in series between a commercial AC power source (4) and a load (5); a control device (3) that causes the plurality of vacuum circuit breakers and the bypass circuit to be both on when the commercial AC power source is normal, and causes a vacuum circuit breaker different from a vacuum circuit breaker that was turned off at the last power failure among the plurality of vacuum circuit breakers to be turned off and causes the bypass circuit to be turned off when the commercial AC power source is powered off; and a power converter (2) that converts DC power of a battery (6) into AC power to supply to the load when the commercial AC power source is powered off.

Description

Technical Field

[0001] This invention relates to a power supply device, and more particularly to a power supply device that supplies AC power from the AC power supply to the load when the AC power supply is normal, and converts the DC power supplied from the DC power supply to AC power and supplies it to the load when the AC power supply fails. Background Technology

[0002] For example, Japanese Patent Application Publication No. 2009-136099 (Patent Document 1) discloses a power supply device having: an input terminal for receiving AC power supplied from an AC power source; an output terminal connected to a load; a bypass circuit connected between the input terminal and the output terminal, which is turned on when the AC power source is normal and turned off when the AC power source is interrupted; and a power converter that converts DC power supplied from a DC power source into AC power and outputs it to the output terminal when the AC power source is interrupted.

[0003] Furthermore, for example, Japanese Patent Application Publication No. 2017-70046 (Patent Document 2) discloses a power supply device comprising: an input terminal for receiving AC power supplied from an AC power source; an output terminal connected to a load; a mechanical switch and a bypass circuit connected in series between the input terminal and the output terminal; a control device that, when the AC power source is normal, turns on both the mechanical switch and the bypass circuit, and when the AC power source fails, turns off the bypass circuit, counts the number of times the AC voltage at the input terminal falls below a lower limit, and if the count value exceeds a predetermined value within a specified time, determines that a short circuit fault has occurred in the bypass circuit and turns off the mechanical switch; and a power converter that, when the AC power source fails, converts the DC power supplied from a DC power source into AC power and supplies it to the load.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-136099

[0007] Patent Document 2: Japanese Patent Application Publication No. 2017-70046 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, in Patent Document 1, a bypass circuit is constructed using a pair of thyristors connected in reverse parallel. The thyristors will not disconnect until the current flowing through them becomes 0A. Therefore, the following problem exists: in the event of an AC power outage, it takes time to disconnect the AC power supply from the load.

[0010] As a countermeasure, one could consider constructing a bypass circuit using a semiconductor switch comprising an IGBT (Insulated Gate Bipolar Transistor) and a diode. This semiconductor switch operates much faster than a thyristor, thus enabling rapid disconnection of the AC power supply from the load in the event of an AC power outage.

[0011] However, this semiconductor switch is susceptible to surge voltages, therefore a buffer circuit is needed to be connected in parallel with the semiconductor switch to suppress surge voltages generated when the semiconductor switch is turned off. The buffer circuit, for example, includes a resistor and a capacitor connected in series to transmit AC voltage.

[0012] Therefore, when the AC power supply fails, the AC output voltage of the power converter is transmitted to the input terminal via a buffer circuit, mistakenly identifying it as AC power restoration. If AC power restoration is detected, the AC power output from the power converter stops, and the system again identifies a power outage, resuming the AC power output from the power converter. This cycle of repeatedly outputting and stopping AC power from the power converter leads to malfunctions in the power supply unit.

[0013] Therefore, the following method can be considered: connect a mechanical switch and a bypass circuit in series between the input and output terminals, so that the mechanical switch and bypass circuit are disconnected when the AC power supply fails. According to this method, the AC output voltage of the power converter can be prevented from being transmitted to the input terminals via the buffer circuit when the AC power supply fails, thus preventing malfunction of the power supply unit.

[0014] Because using high-speed mechanical switches would increase costs, it is desirable to use inexpensive vacuum circuit breakers as mechanical switches. However, to close a vacuum circuit breaker that is in an open state, the potential energy of a spring, such as an energy storage motor, needs to be accumulated, making it impossible for the vacuum circuit breaker to repeatedly open and close within a short period of time. Therefore, when using a vacuum circuit breaker as a mechanical switch, the following problem exists: if the AC power supply is repeatedly interrupted and restored within a short period of time, it will not operate normally.

[0015] Therefore, the main objective of this invention is to provide a low-cost power supply device that operates at high speed and stably.

[0016] Solution for solving the problem

[0017] The power supply device of the present invention comprises: an input terminal for receiving AC power supplied from an AC power source; an output terminal connected to a load; a plurality of mechanical switches and a bypass circuit connected in series between the input terminal and the output terminal; a control device that, when the AC power source is normal, turns on all the plurality of mechanical switches and the bypass circuit, and when the AC power source is interrupted, turns off a mechanical switch that is different from the mechanical switch that was turned off during the previous power outage and disconnects the bypass circuit; and a power converter that, when the AC power source is interrupted, converts the DC power supplied from the DC power source into AC power and outputs it to the output terminal.

[0018] The effects of the invention

[0019] For the power supply device involved in this invention, multiple mechanical switches are connected in series between the input terminal and one terminal of the bypass circuit. When the AC power supply is normal, all multiple mechanical switches are turned on. When the AC power supply fails, one of the multiple mechanical switches that is different from the mechanical switch that was turned off during the last power failure is turned off.

[0020] Therefore, even when using parallel-connected semiconductor switches and buffer circuits to form a bypass circuit, it is possible to prevent the AC output voltage of the power converter from appearing at the input terminal via the bypass circuit when the AC power supply fails, thereby preventing malfunction of the power supply unit.

[0021] Furthermore, even when using inexpensive vacuum circuit breakers as mechanical switches, the vacuum circuit breaker, unlike those that have been opened and closed during the previous power outage and restoration, can be opened because the spring has already stored potential energy. Therefore, multiple mechanical switches can be quickly closed once AC power has been restored. This results in a low-cost power supply device that can operate at high speed and with stability. Attached Figure Description

[0022] Figure 1 This is a circuit block diagram illustrating the structure of an uninterruptible power supply device according to one embodiment of the present invention.

[0023] Figure 2 It means Figure 1 The diagram shows the structure of a vacuum circuit breaker.

[0024] Figure 3 It is used for explanation Figure 2 The timing diagram for the problem of the vacuum circuit breaker is shown.

[0025] Figure 4 This is a timing diagram used to illustrate the effects of the invention of this application.

[0026] Figure 5 It means Figure 1 The block diagram of the bypass circuit shown is shown.

[0027] Figure 6 It means Figure 5 The circuit diagram shown illustrates the structure of the AC switch.

[0028] Figure 7 It means Figure 1 The diagram shows the structure of the control device.

[0029] Figure 8 It means Figure 7 The timing diagram of the control device's operation is shown.

[0030] Figure 9 This is a circuit diagram illustrating a modified implementation example. Detailed Implementation

[0031] Figure 1 This is a circuit block diagram illustrating the structure of an uninterruptible power supply device according to one embodiment of the present invention. Figure 1 The uninterruptible power supply device has an input terminal T1, an output terminal T2, a battery terminal T3, and multiple (in) Figure 1 The system consists of two vacuum circuit breakers (mechanical switches) S1 and S2, a bypass circuit 1, a power converter 2, and a control device 3.

[0032] Input terminal T1 receives AC voltage VI at the commercial frequency supplied from commercial AC power supply 4. The instantaneous value of AC voltage VI is detected by control device 3. Control device 3 uses the detected value of AC voltage VI to detect power outages and restorations of commercial AC power supply 4.

[0033] Output terminal T2 is connected to load 5. Load 5 is driven by AC voltage VO supplied from the output terminal T2 of the uninterruptible power supply. The instantaneous value of AC voltage VO is detected by control device 3.

[0034] Battery terminal T3 is connected to battery 6 (DC power supply, power storage device). Battery 6 stores DC power. Alternatively, a capacitor can be connected instead of battery 6. The instantaneous value of the DC voltage VB (inter-terminal voltage of battery 6) at battery terminal T3 is detected by control device 3.

[0035] Vacuum circuit breakers S1 and S2 are connected in series between input terminal T1 and one terminal 1a of bypass circuit 1. Vacuum circuit breakers S1 and S2 are controlled by control device 3. When the AC voltage VI supplied from commercial AC power supply 4 is within the normal range (when commercial AC power supply 4 is normal), both vacuum circuit breakers S1 and S2 are closed.

[0036] If the AC voltage VI supplied from commercial AC power supply 4 is not within the normal range (when commercial AC power supply 4 is interrupted), one of the vacuum circuit breakers S1 and S2 (in this case, S2) will disconnect, unlike the vacuum circuit breaker S1 which was disconnected and connected during the previous power outage and restoration. The reason for this will be explained in detail later.

[0037] The other terminal 1b of the bypass circuit 1 is connected to the output terminal T2. The bypass circuit 1 is controlled by the control device 3. When the commercial AC power supply 4 is normal, the bypass circuit 1 is connected. When the commercial AC power supply 4 is de-energized, the bypass circuit 1 is disconnected.

[0038] The AC terminal 2a of power converter 2 is connected to the output terminal T2, and the DC terminal 2b of power converter 2 is connected to the battery terminal T3. Power converter 2 is controlled by control device 3. When the commercial AC power supply 4 is normal, power converter 2 converts the AC power supplied from the commercial AC power supply 4 via vacuum circuit breakers S1 and S2 and bypass circuit 1 into DC power and stores it in battery 6. At this time, control device 3 controls power converter 2 by changing the voltage VB between the terminals of battery 6 to the reference voltage VBR.

[0039] When the commercial AC power supply 4 fails, the power converter 2 converts the DC power from the battery 6 into AC power at the commercial frequency and supplies it to the load 5. At this time, the control device 3 controls the power converter 2 to change the AC voltage VO at the output terminal T2 to the reference AC voltage VOR. In addition, the control device 3 stops the operation of the power converter 2 when the voltage VB between the terminals of the battery 6 has reached the lower limit voltage.

[0040] Next, the operation of the uninterruptible power supply device will be briefly explained. When the commercial AC power supply 4 is normal, the vacuum circuit breakers S1 and S2 and the bypass circuit 1 are all connected, supplying AC power from the commercial AC power supply 4 to the load 5 through the vacuum circuit breakers S1 and S2 and the bypass circuit 1, so that the load 5 can operate.

[0041] In addition, AC power is supplied from commercial AC power source 4 to power converter 2 via vacuum circuit breakers S1 and S2 and bypass circuit 1, and the AC power is converted into DC power by power converter 2 and stored in battery 6.

[0042] If the commercial AC power supply 4 experiences a power outage, a different vacuum circuit breaker (S1 in this case) will trip, unlike the one that tripped during the previous power outage (e.g., S2), and bypass circuit 1 will disconnect, breaking the circuit between the commercial AC power supply 4 and the load 5. The DC power from the battery 6 will be converted to AC power by the power converter 2 and supplied to the load 5, allowing the load 5 to continue operating.

[0043] If commercial AC power supply 4 is restored, vacuum circuit breakers S1 and S2 and bypass circuit 1 are all connected, supplying AC power from commercial AC power supply 4 to load 5 through vacuum circuit breakers S1 and S2 and bypass circuit 1, and load 5 starts operating.

[0044] In addition, AC power is supplied from commercial AC power source 4 to power converter 2 via vacuum circuit breakers S1 and S2 and bypass circuit 1, and the AC power is converted into DC power by power converter 2 and stored in battery 6.

[0045] If the commercial AC power supply 4 experiences another power outage, vacuum circuit breaker S2, which is different from the one that tripped during the previous power outage (S1), will trip, and bypass circuit 1 will disconnect, breaking the circuit between commercial AC power supply 4 and load 5. The DC power from battery 6 will be converted into AC power by power converter 2 and supplied to load 5, allowing load 5 to continue operating.

[0046] Next, the reasons for connecting the two vacuum circuit breakers S1 and S2 in series and causing a different vacuum circuit breaker than the one that disconnected during the previous power outage to disconnect in the event of a power failure of the commercial AC power supply 4 are explained in detail.

[0047] Figure 2 This is a block diagram showing the structure of the vacuum circuit breaker S1. Figure 2 The vacuum circuit breaker S1 includes a vacuum valve 10, conductors 13 and 14, external terminals 15 and 16, an operating lever 17, an operating mechanism 18, a spring 19, and a drive unit 20.

[0048] The vacuum valve 10 includes a pair of electrodes 11 and 12. The front ends of electrodes 11 and 12 are disposed inside the vacuum valve 10 and are arranged facing each other. The rear ends of electrodes 11 and 12 protrude outside the vacuum valve 10. Electrode 11 is fixed to the upper end of the vacuum valve 10, and electrode 12 is supported on the lower end of the vacuum valve 10 in a manner that allows it to move in the vertical direction.

[0049] The rear end of electrode 11 is connected to external terminal 15 via conductor 13. The rear end of electrode 12 is connected to external terminal 16 via conductor 14 and is coupled to operating mechanism 18 via operating lever 17. Operating lever 17 is formed of insulating material.

[0050] The drive unit 20 includes an energy storage motor, a cam, etc., which causes the spring 19 to accumulate potential energy. The operating mechanism 18 responds to the disconnect command signal S1off from the control device 3 to move the operating lever 17 downward. When the operating lever 17 moves downward, the electrode 12 moves downward, the front ends of the electrodes 11 and 12 separate from each other, the external terminals 15 and 16 become non-conductive, and the vacuum circuit breaker S1 is disconnected.

[0051] Furthermore, when the spring 19 has accumulated potential energy, the operating mechanism 18 responds to the on command signal S1on from the control device 3 to release the spring 19, using the release force of the spring 19 to move the operating lever 17 upward. When the operating lever 17 moves upward, the electrode 12 moves upward, the front ends of electrodes 11 and 12 contact each other, the external terminals 15 and 16 become conductive, and the vacuum circuit breaker S1 is turned on. If the spring 19 is released, the drive unit 20 immediately causes the spring 19 to accumulate potential energy.

[0052] Figure 3 This is a timing diagram illustrating the operation of vacuum circuit breaker S1 when only one vacuum circuit breaker S1 is connected between input terminal T1 and one terminal 1a of bypass circuit 1. Figure 3 In the diagram, (A) shows the effective value of the AC voltage VI supplied from the commercial AC power supply 4, (B) shows the on and off states of the vacuum circuit breaker S1, and (C) shows the energy E1 of the spring 19.

[0053] For the sake of simplicity in the accompanying drawings and description, it is assumed that the AC terminal 2a of the power converter 2 is disconnected from the output terminal T2. Therefore, when the commercial AC power supply 4 is interrupted, the AC output voltage VO of the power converter 2 will not appear at one terminal 1a of the bypass circuit 1.

[0054] exist Figure 3 The diagram illustrates repeated power outages and restorations of the commercial AC power supply 4. When the commercial AC power supply 4 is functioning normally, the AC voltage VI is high; when the commercial AC power supply 4 is de-energized, the AC voltage VI becomes low.

[0055] Assuming that in the initial state, the commercial AC power supply 4 is normal, the vacuum circuit breaker S1 is closed, the potential energy of spring 19 is fully accumulated, and the energy E1 of spring 19 remains at a high value. When the vacuum circuit breaker S1 is opened (times t1, t3, ...), spring 19 is not used, and the energy E1 of spring 19 does not change. When the vacuum circuit breaker S1 is closed (times t2, t5, ...), spring 19 is released, and the energy E1 of spring 19 decreases from a high value to a low value.

[0056] If spring 19 is released, it immediately passes through drive unit 20 ( Figure 2 This allows spring 19 to accumulate potential energy. If spring 19 begins to accumulate potential energy, its energy E1 gradually increases. A specified time Tc is required for the energy E1 of spring 19 to increase from a low value to a high value.

[0057] like Figure 3As shown, if the time from the start of power outage to the restoration of power is longer than the specified time Tc (e.g., time t2 to t5), the potential energy of spring 19 is completed at the time of power restoration t5, so the vacuum circuit breaker S1 can be turned on at the time of power restoration t5.

[0058] However, if the time from the start of power outage to the restoration of power is shorter than the specified time Tc (e.g., time t7 to t9), the potential energy of spring 19 has not been fully accumulated at the time of power restoration t9, so the vacuum circuit breaker S1 cannot be turned on at the time of power restoration t9.

[0059] Therefore, with only one vacuum circuit breaker S1 connected between the input terminal T1 and one terminal 1a of the bypass circuit 1, it is impossible to cope with repeated power outages and restorations of the commercial AC power supply 4 in a short period of time.

[0060] then, Figure 4 This is a timing diagram illustrating the operation of vacuum circuit breakers S1 and S2 when two vacuum circuit breakers S1 and S2 are connected between input terminal T1 and a terminal 1a of bypass circuit 1. Figure 4 In the diagram, (A) shows the effective value of the AC voltage VI supplied from the commercial AC power supply 4, (B) shows the on and off states of the vacuum circuit breaker S1, (C) shows the energy E1 of the spring 19 of the vacuum circuit breaker S1, (D) shows the on and off states of the vacuum circuit breaker S2, (E) shows the energy E2 of the spring 19 of the vacuum circuit breaker S2, and (F) shows the on and off states of a mechanical switch S3 consisting of two vacuum circuit breakers S1 and S2 connected in series.

[0061] and Figure 3 Similarly, for the sake of simplicity in the accompanying drawings and description, it is assumed that the AC terminal 2a of the power converter 2 is disconnected from the output terminal T2. Therefore, when the commercial AC power supply 4 is interrupted, the AC output voltage VO of the power converter 2 will not appear at one terminal 1a of the bypass circuit 1.

[0062] exist Figure 4 The image shows a commercial AC power supply 4 in conjunction with... Figure 3 The same timed cycle of power outage and restoration repeats. When the commercial AC power supply 4 is normal, the AC voltage VI is high; when the commercial AC power supply 4 is interrupted, the AC voltage VI becomes low.

[0063] Assuming that in the initial state, the commercial AC power supply 4 is normal, both vacuum circuit breakers S1 and S2 are closed, the energies E1 and E2 of the springs 19 of vacuum circuit breakers S1 and S2 are high, and the mechanical switch S3 is closed.

[0064] If at some moment t1 the commercial AC power supply 4 experiences a power outage, then vacuum circuit breaker S1, which is different from the previously disconnected vacuum circuit breaker S2, will disconnect, and mechanical switch S3 will disconnect.

[0065] If commercial AC power supply 4 is restored at time t2, the spring 19 of vacuum circuit breaker S1 is released, thus closing vacuum circuit breaker S1 and mechanical switch S3. If the spring 19 of vacuum circuit breaker S1 is released, it immediately begins to accumulate potential energy, and the energy E1 of the spring 19 gradually increases. At time t4, after a predetermined time Tc has elapsed from time t2, the energy E1 of the spring 19 becomes high, and the accumulation of potential energy in the spring 19 of vacuum circuit breaker S1 is complete.

[0066] If the commercial AC power supply 4 experiences another power outage at time t3, vacuum circuit breaker S2, which is different from the previously disconnected vacuum circuit breaker S1, will disconnect, and mechanical switch S3 will disconnect.

[0067] If commercial AC power supply 4 is restored at time t5, spring 19 of vacuum circuit breaker S2 is released, thus closing vacuum circuit breaker S2 and mechanical switch S3. If spring 19 of vacuum circuit breaker S2 is released, it immediately begins to accumulate potential energy, and its energy E2 gradually increases. At time t7, after a predetermined time Tc has elapsed from time t5, the energy E2 of spring 19 reaches a high value, and the accumulation of potential energy in spring 19 of vacuum circuit breaker S2 is complete.

[0068] like Figure 4 As shown, in this embodiment, while one vacuum circuit breaker (e.g., S1) is being opened and closed and its spring 19 is accumulating potential energy, another vacuum circuit breaker (in this case, S2) is also opened and closed (e.g., at times t6 to t10). Therefore, even if the time from the power outage to the restoration of power is shorter than the predetermined time Tc (e.g., at times t7 to t9), it is possible to close the vacuum circuit breaker S2 at the time of power restoration t9.

[0069] Therefore, as Figure 4 As shown, even if the commercial AC power supply 4 repeatedly experiences power outages and restorations within a short period of time, the mechanical switch S3 can be opened during a power outage and closed during a power restoration, thus enabling the mechanical switch S3 (i.e., vacuum circuit breakers S1 and S2) to operate normally.

[0070] Figure 5 This is a block diagram showing the structure of bypass circuit 1. Figure 5In the bypass circuit 1, there are multiple stages of AC switches 21 connected in series between one terminal 1a and another terminal 1b. One terminal 21a of the first-stage AC switch 21 is connected to one terminal 1a of the bypass circuit 1. One terminal 21a of each subsequent AC switch 21 is connected to the other terminal 12b of the preceding AC switch 21, and the other terminal 21b of each subsequent AC switch 21 is connected to one terminal 12a of the following AC switch 21. The other terminal 21b of the final-stage AC switch 21 is connected to the other terminal 1b of the bypass circuit 1, i.e., the output terminal T2. Figure 1 )connect.

[0071] Multiple AC switches 21 are controlled by control device 3. When the commercial AC power supply 4 is normal, all AC switches 21 are turned on, and bypass circuit 1 is turned on. When the commercial AC power supply 4 fails, all AC switches 21 are turned off, and bypass circuit 1 is turned off.

[0072] Figure 6 This is a circuit diagram showing the structure of AC switch 21. Figure 6 In the AC switch 21, there are a semiconductor switch 22, a buffer circuit 23, and a variable resistor 26 connected in parallel between one terminal 21a and another terminal 21b.

[0073] Semiconductor switch 22 includes IGBTs Q1 and Q2 and diodes D1 and D2. The collectors of IGBTs Q1 and Q2 are connected to each other, and the emitters of IGBTs Q1 and Q2 are connected to terminals 21a and 21b, respectively. Diodes D1 and D2 are connected in reverse parallel with IGBTs Q1 and Q2, respectively. The switching on and off of IGBTs Q1 and Q2 is controlled by control device 3.

[0074] When the commercial AC power supply 4 is normal, during the period when the AC voltage VI supplied from the commercial AC power supply 4 is a positive voltage, the gates of IGBT Q1 and Q2 are at "L" and "H" levels, respectively. As a result, IGBT Q1 and Q2 are in the off state and on state, respectively, and the current flows from one terminal 21a through diode D1 and IGBT Q2 to the other terminal 21b.

[0075] Furthermore, when the commercial AC power supply 4 is normal, during the period when the AC voltage VI supplied from the commercial AC power supply 4 is negative, the gates of IGBTs Q1 and Q2 are at "H" and "L" levels, respectively. Therefore, IGBTs Q1 and Q2 are in the ON and OFF states, respectively, and current flows from another terminal 21b through diode D2 and IGBT Q1 to one terminal 21a. Consequently, when the commercial AC power supply 4 is normal, the semiconductor switch 22 is turned on.

[0076] Furthermore, when the commercial AC power supply 4 is interrupted, the gates of IGBTs Q1 and Q2 are both at an "L" level, and both IGBTs Q1 and Q2 are disconnected. Therefore, when the commercial AC power supply 4 is interrupted, semiconductor switch 22 is disconnected.

[0077] As described in Patent Document 1, there is also a method for constructing a bypass circuit using a pair of thyristors connected in reverse parallel. However, in this method, the thyristors do not disconnect until the current flowing through them becomes 0A, thus increasing the interruption time of the bypass circuit.

[0078] In contrast, in this embodiment, a semiconductor switch 22 comprising IGBTs Q1 and Q2 and diodes D1 and D2 is used to construct the bypass circuit 1, thus shortening the turn-off time of the bypass circuit 1. However, compared to thyristors, this semiconductor switch 22 has the disadvantage of being susceptible to surge voltage. Therefore, in this embodiment, a buffer circuit 23 and a variable resistor 26 are connected in parallel to the semiconductor switch 22.

[0079] The buffer circuit 23 includes a resistive element 24 and a capacitor 25 connected in series between terminals 21a and 21b. If the semiconductor switch 22 is suddenly turned off while current is flowing through it, a surge voltage is generated between terminals 21a and 21b due to self-inductance. The buffer circuit 23 protects the semiconductor switch 22 by suppressing this surge voltage.

[0080] A variable resistor 26 is connected between terminals 21a and 21b. When the voltage between terminals 21a and 21b is lower than the threshold voltage, the resistance of the variable resistor 26 is high. If the voltage between terminals 21a and 21b exceeds the threshold voltage, the resistance of the variable resistor 26 becomes low. Therefore, it is possible to prevent the voltage between terminals 21a and 21b from exceeding the threshold voltage, thereby preventing the semiconductor switch 22 from being damaged by surge voltage.

[0081] Therefore, in this embodiment, since the bypass circuit 1 is constructed using a semiconductor switch 22 comprising IGBTs Q1 and Q2 and diodes D1 and D2, compared to the case where a bypass circuit is constructed using a pair of thyristors, the bypass circuit 1 can be quickly disconnected in the event of a power outage of the commercial AC power supply 4, thus cutting off the connection between the commercial AC power supply 4 and the load 5 in a short time. Furthermore, since a buffer circuit 23 and a variable resistor 26 are connected in parallel to the semiconductor switch 22, damage to the semiconductor switch 22 due to surge voltage can be prevented.

[0082] However, the buffer circuit 23, including the series-connected resistor 24 and capacitor 25, transmits AC voltage. Therefore, even when the commercial AC power supply 4 fails, and the semiconductor switch 22 is already open, the AC voltage is still transmitted via the power converter 2 ( Figure 1The generated AC voltage VO is also transmitted to a terminal 1a of the bypass circuit 1 via a multi-stage buffer circuit 23.

[0083] In addition, the interruption time of vacuum circuit breakers S1 and S2 is longer than that of semiconductor switch 22. Therefore, before vacuum circuit breaker S1 or S2 is disconnected, the AC voltage VO generated by power converter 2 is transmitted to input terminal T1 via multi-stage buffer circuit 23 and vacuum circuit breakers S1 and S2.

[0084] In this scenario, the following concern exists: Although the commercial AC power supply 4 is actually de-energized, the AC voltage VI at input terminal T1 is used to determine that the commercial AC power supply 4 has been restored. Vacuum circuit breakers S1 and S2 and bypass circuit 1 are activated, and the DC-AC conversion operation of power converter 2 stops. If the DC-AC conversion operation of power converter 2 stops, the output AC voltage VO from power converter 2 ceases, thus again indicating that the commercial AC power supply 4 has been de-energized.

[0085] Therefore, the AC voltage VO from the power converter 2 will repeatedly output and stop, and the load 5 cannot operate normally. Therefore, in this embodiment, the control device 3 determines whether the commercial AC power supply 4 has been restored to power after a predetermined time Td has elapsed since the power outage. The predetermined time Td is set to be longer than the disconnection time required for each of the vacuum circuit breakers S1 and S2 to open. Next, the structure for implementing this power restoration detection method will be described.

[0086] Figure 7 This is a block diagram showing the structure of control device 3. Figure 7 In this configuration, the control device 3 includes voltage detectors 30-32, a power outage detector 33, a power restoration detector 34, and a control unit 35. Voltage detector 30 detects the instantaneous value of the AC voltage VI at input terminal T1 and outputs a signal φ30 representing its detected value. Voltage detector 31 detects the instantaneous value of the AC voltage VO at output terminal T2 and outputs a signal φ31 representing its detected value. Voltage detector 32 detects the instantaneous value of the DC voltage VB at battery terminal T3 and outputs a signal φ32 representing its detected value.

[0087] The power outage detector 33 compares the effective value of the AC voltage VI represented by the output signal φ30 of the voltage detector 30 with its lower limit value, and outputs a power outage detection signal φ33 based on the comparison result. When the effective value of the AC voltage VI is higher than the lower limit value, the power outage detection signal φ33 is set to a deactivated "H" level. When the effective value of the AC voltage VI drops below the lower limit value, the power outage detection signal φ33 is set to an activated "L" level.

[0088] After a predetermined time Td elapses following the drop in power outage detection signal φ33 from "H" level to "L" level, the power restoration detector 34 compares the effective value of the AC voltage VI represented by the output signal φ30 of the voltage detector 30 with its lower limit value. Based on the comparison result, it outputs a power restoration detection signal φ34. If the effective value of AC voltage VI is lower than the lower limit, the power restoration detection signal φ34 is set to the deactivated "L" level. If the effective value of AC voltage VI rises above the lower limit, the power restoration detection signal φ34 is set to the activated "H" level.

[0089] The control unit 35 controls the vacuum circuit breakers S1 and S2, the bypass circuit 1, and the power converter 2 based on the output signals φ30 to φ32 of the voltage detectors 30 to 32, the power outage detection signal φ33, and the power restoration detection signal φ34.

[0090] Figure 8 It means Figure 7 The timing diagram of the operation of control device 3 is shown. Figure 8 In the diagram, (A) shows the effective value of the AC voltage VI at input terminal T1, (B) shows the effective value of the AC voltage VO at output terminal T2, (C) shows the waveform of the power outage detection signal φ33, (D) shows the waveform of the power restoration detection signal φ34, (E) shows the on and off states of vacuum circuit breaker S1, and (F) shows the on and off states of vacuum circuit breaker S2.

[0091] exist Figure 8 In the initial state, the commercial AC power supply 4 is normal, and the vacuum circuit breakers S1 and S2 and the bypass circuit 1 are all connected. At this time, AC voltage VI is supplied from the commercial AC power supply 4 to the output terminal T2 through the vacuum circuit breakers S1 and S2 and the bypass circuit 1, and both AC voltages VI and VO are high values. In addition, the power outage detection signal φ33 is a deactivated "H" level, and the power restoration detection signal φ34 is an activated "H" level.

[0092] If the commercial AC power supply 4 fails to operate at a certain time t1, the AC voltages VI and VO will drop to low values, the power failure detection signal φ33 will become the activated level "L", and the power restoration detection signal φ34 will become the deactivated level "L".

[0093] If the power outage detection signal φ33 becomes the activation level "L", the control unit 35 disconnects each semiconductor switch 22 of the bypass circuit 1 and outputs a disconnect command signal S1off to the vacuum circuit breaker S1, which is different from the vacuum circuit breaker S2 that was disconnected last time. Figure 2This causes the power converter 2 to perform a DC-AC conversion operation. The vacuum circuit breaker S1 initiates the disconnection operation in response to the disconnection command signal S1off, and disconnects at time t2 after the disconnection time has elapsed.

[0094] According to the instructions from the control unit 35, the power converter 2 converts the DC voltage VB of the battery 6 into AC voltage VO and outputs it to the output terminal T2. This AC voltage VO is supplied to the load 5. On the other hand, this AC voltage VO is also supplied via multiple buffer circuits 23 included in the bypass circuit 1. Figure 6 The signal is transmitted to the input terminal T1 by the vacuum circuit breakers S1 and S2, and is detected by the voltage detector 30 as AC voltage VI. The power outage detection signal φ33 becomes the deactivated level "H" level (time t1~t2).

[0095] If the power restoration detector 34 determines whether the commercial AC power supply 4 has been restored based on the output signal φ30 of the voltage detector 30 during this period (times t1 to t2), it may lead to the mistaken assumption that the power supply has been restored even though it has not actually been restored. Therefore, in this embodiment, the power restoration detector 34 stops determining whether the power supply has been restored during the period (times t1 to t3) from the time of the power outage until a predetermined time Td has elapsed since the power outage, and starts determining whether the power supply has been restored at time t3, after the predetermined time Td has elapsed since the power outage (time 1). This predetermined time Td is longer than the disconnection time of the vacuum circuit breaker S1, so the vacuum circuit breaker S1 disconnects at time t3.

[0096] If the vacuum circuit breaker S1 opens (at time t2), the AC output voltage VO of the power converter 2 is no longer transmitted to the input terminal T1, the AC voltage VI decreases to a low value, and the power outage detection signal φ33 becomes the activated "L" level. At time t3, the power restoration detector 34 restarts its judgment on whether the power supply has been restored, and the power restoration detection signal φ34 maintains the deactivated "L" level.

[0097] If commercial AC power supply 4 resumes power at time t4, the AC voltage VI supplied from commercial AC power supply 4 rises to a high value. If AC voltage VI rises to a high value, the power outage detection signal φ33 becomes the deactivated level "H", and the power restoration detection signal φ34 becomes the activated level "H".

[0098] If the power supply detection signal φ34 becomes "H" level, the control unit 35 controls the power converter 2 to make the phase of AC voltage VO match the phase of AC voltage VI. If the phases of AC voltages VO and VI are matched, the control unit 35 connects the bypass circuit 1 and outputs a connection command signal S1on to the vacuum circuit breaker S1. Figure 2If the vacuum circuit breaker S1 is closed (at time t5), AC power is supplied from the commercial AC power supply 4 to the load 5 via the vacuum circuit breakers S1 and S2 and the bypass circuit 1. The control unit 35 causes the power converter 2 to perform AC-DC conversion.

[0099] As described above, in this embodiment, a semiconductor switch 22 including IGBTs Q1 and Q2 and diodes D1 and D2 is used to construct the bypass circuit 1. Therefore, compared with the case where a pair of thyristors are used to construct the bypass circuit, the bypass circuit 1 can be quickly disconnected when the commercial AC power supply 4 fails, thereby quickly disconnecting the commercial AC power supply 4 from the load 5.

[0100] Furthermore, two vacuum circuit breakers S1 and S2 are connected in series between input terminal T1 and one terminal 1a of bypass circuit 1. When the commercial AC power supply 4 is normal, both vacuum circuit breakers S1 and S2 are closed. When the commercial AC power supply 4 is interrupted, a different vacuum circuit breaker (S2 in this case) that was disconnected during the previous power outage (e.g., S1) is disconnected. Therefore, it is possible to prevent the AC output voltage of the power converter 2 from appearing at input terminal T1 via bypass circuit 1 when the commercial AC power supply 4 is interrupted, thereby preventing malfunction of the uninterruptible power supply device.

[0101] Furthermore, since a specified time Td has elapsed since the power outage of commercial AC power supply 4... Figure 8 Then it determines whether power has been restored, thus preventing the detection of AC voltage supplied from power converter 2 via bypass circuit 1 and vacuum circuit breakers S2 and S1 from being mistakenly judged as having restored power.

[0102] Furthermore, since the vacuum circuit breaker (S2 in this case) whose spring 19 has already stored potential energy is disconnected, unlike the vacuum circuit breaker (e.g., S1) that has already performed disconnection and connection operations during the previous power outage and restoration, the vacuum circuit breakers S1 and S2 can be quickly switched on after the commercial AC power supply 4 has been restored. In addition, since the inexpensive vacuum circuit breakers S1 and S2 are used instead of expensive high-speed mechanical switches, the cost of the device can be reduced. Therefore, a low-cost uninterruptible power supply device that operates at high speed and stably can be realized.

[0103] Furthermore, in this embodiment, two vacuum circuit breakers S1 and S2 are connected in series between the input terminal T1 and one terminal 1a of the bypass circuit 1. However, this is not a limitation; N vacuum circuit breakers (N being an integer of 3 or more) can also be connected in series between the input terminal T1 and one terminal 1a of the bypass circuit 1. In this case, if N power outages and power restorations occur, the N vacuum circuit breakers can be opened and closed sequentially one by one.

[0104] Figure 9 This is a circuit diagram illustrating a modified implementation example, and is related to... Figure 6 Comparison chart. (Refer to the original text.) Figure 9 The difference between this modified example and the previous implementation is that semiconductor switch 22 is replaced by semiconductor switch 22A. Semiconductor switch 22A includes IGBTs Q1 and Q2 and diodes D1 and D2. The emitters of IGBTs Q1 and Q2 are connected to each other, and the collectors of IGBTs Q1 and Q2 are connected to terminals 21a and 21b, respectively. Diodes D1 and D2 are connected in reverse parallel with IGBTs Q1 and Q2, respectively. The switching on and off of IGBTs Q1 and Q2 is controlled by control device 3.

[0105] When the commercial AC power supply 4 is normal, during the period when the AC voltage VI supplied from the commercial AC power supply 4 is a positive voltage, the gates of IGBT Q1 and Q2 are at "H" level and "L" level, respectively. As a result, IGBT Q1 and Q2 are in the ON and OFF states, respectively, and the current flows from one terminal 21a through IGBT Q1 and diode D2 to the other terminal 21b.

[0106] Furthermore, when the commercial AC power supply 4 is normal, during the period when the AC voltage VI supplied from the commercial AC power supply 4 is negative, the gates of IGBTs Q1 and Q2 are at "L" and "H" levels, respectively. Therefore, IGBTs Q1 and Q2 are in the off and on states, respectively, and current flows from the other terminal 21b through IGBT Q2 and diode D1 to one terminal 21a. Consequently, when the commercial AC power supply 4 is normal, semiconductor switch 22A is turned on.

[0107] Furthermore, when the commercial AC power supply 4 is interrupted, the gates of IGBTs Q1 and Q2 are both at an "L" level, and both IGBTs Q1 and Q2 are disconnected. Therefore, when the commercial AC power supply 4 is interrupted, semiconductor switch 22A is disconnected.

[0108] In this modified example, the same effect as in the implementation method is obtained. Other structures and operations are the same as in the implementation method, so their description will not be repeated.

[0109] The embodiments disclosed herein should be considered illustrative rather than limiting in all respects. The invention is defined by the claims, not by the foregoing description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0110] Explanation of reference numerals in the attached figures

[0111] T1: Input terminal; T2: Output terminal; T3: Battery terminal; S1, S2: Vacuum circuit breaker; 1: Bypass circuit; 2: Power converter; 3: Control device; 4: Commercial AC power supply; 5: Load; 6: Battery; 10: Vacuum valve; 11, 12: Electrodes; 13, 14: Conductors; 15, 16: External terminals; 17: Operating lever; 18: Operating mechanism; 19: Spring; 20: Drive unit; 21: AC switch; 22, 22A: Semiconductor switch; 23: Buffer circuit; 24: Resistive element; 25: Capacitor; 26: Variable resistor; Q1, Q2: IGBT; D1, D2: Diode; 30-32: Voltage detector; 33: Power outage detector; 34: Power restoration detector; 35: Control unit.

Claims

1. A power supply device comprising: Input terminal, which receives AC power supplied from an AC power source; Output terminals, which are connected to the load; A bypass circuit and a plurality of mechanical switches are connected in series between the input terminal and the output terminal. The bypass circuit includes semiconductor switches and a buffer circuit connected in parallel with each other. A control device that, when the AC power supply is normal, turns on all of the plurality of mechanical switches and the bypass circuit; and when the AC power supply fails, turns off one of the plurality of mechanical switches that is different from the mechanical switch that was turned off during the previous power failure, and turns off the bypass circuit. as well as A power converter that, when the AC power supply fails, converts the DC power supplied from the DC power supply into AC power and outputs it to the output terminal.

2. The power supply device according to claim 1, wherein, Each of the mechanical switches is a vacuum circuit breaker.

3. The power supply device according to claim 2, wherein, The vacuum circuit breaker includes: A pair of electrodes; spring; The driving part, which causes the spring to store potential energy; and The operating mechanism, when the vacuum circuit breaker is open, separates the pair of electrodes; when the vacuum circuit breaker is closed, the operating mechanism uses the release force of the spring to bring the pair of electrodes into contact.

4. The power supply device according to claim 1, wherein, The semiconductor switch includes a first terminal and a second terminal, a first transistor and a second transistor, and a first diode and a second diode. The first electrode of the first transistor and the first electrode of the second transistor are connected to each other. The second electrode of the first transistor and the second electrode of the second transistor are respectively connected to the first terminal and the second terminal. The first diode and the second diode are connected in reverse parallel with respect to the first transistor and the second transistor, respectively. The buffer circuit is connected between the first terminal and the second terminal.

5. The power supply device according to claim 1, wherein, The buffer circuit includes a resistor and a capacitor connected in series.

6. The power supply device according to claim 1, wherein, The control device includes: A voltage detector that detects the AC voltage at the input terminal; A power outage detector that outputs a power outage detection signal when the AC voltage detected by the voltage detector is not within the normal range; A power restoration detector outputs a power restoration detection signal when a predetermined time has elapsed since the power outage detector outputs the power outage detection signal, and the AC voltage detected by the voltage detector is within the normal range; and The control unit, in response to the power outage detection signal, disconnects a mechanical switch among the plurality of mechanical switches that is different from the one that was disconnected during the previous power outage and disconnects the bypass circuit; and in response to the power restoration detection signal, it connects both the plurality of mechanical switches and the bypass circuit. The predetermined time is longer than the cutting time of the mechanical switch.

7. The power supply device according to claim 1, wherein, The DC power supply includes a power storage device that stores DC power. When the AC power supply is normal, the power converter converts the AC power supplied from the AC power supply via the plurality of mechanical switches and the bypass circuit into DC power and stores it in the power storage device. When the AC power supply fails, the DC power in the power storage device is converted into AC power and output to the output terminal.

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