Uninterruptible power supply

Abstract

The uninterruptible power supply includes an AC / DC converter 11 that converts AC power supplied from a commercial AC power source (15) into DC power and supplies it to a DC line (DL), a DC / AC converter (13) that converts DC power received from the DC line into AC power and supplies it to a load (17), a DC / DC converter (12) that exchanges DC power between the DC line and a battery (16), and a bidirectional converter (14) that operates in conjunction with the AC / DC converter (11) to convert AC power supplied from the commercial AC power source into DC power and supplies it to the DC line when fast charging the battery. Therefore, it is possible to prevent a shortage of DC power during fast charging operation and fast charge the battery while supplying rated power to the load.

Description

[Technical field]

[0001] The present disclosure relates to an uninterruptible power supply, and more particularly to an uninterruptible power supply that converts AC power supplied from an AC power supply into DC power, and then converts the DC power into AC power to supply it to a load. [Background technology]

[0002] For example, Japanese Patent No. 7073590 (Patent Document 1) discloses an uninterruptible power supply including first, second, and third power converters. When the AC power supply is normal, the first power converter converts AC power supplied from the AC power supply into DC power and supplies it to a DC line. When the AC power supply is out of order, the operation of the first power converter is stopped. The second power converter converts DC power received from the DC line into AC power and supplies it to a load. When the AC power supply is normal, the third power converter stores DC power received from the DC line in a power storage device, and when the AC power supply is out of order, supplies the DC power of the power storage device to the DC line. Therefore, even if a power outage occurs in the AC power supply, the operation of the load can be continued for the period during which DC power is stored in the power storage device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7073590 Summary of the Invention [Problem to be solved by the invention]

[0004] Traditionally, lead-acid batteries have been used primarily as power storage devices, but in recent years, lithium-ion batteries have begun to be used as power storage devices. Lithium-ion batteries have the advantage of being larger in capacity per unit volume than lead-acid batteries and capable of being charged quickly. For this reason, recent uninterruptible power supplies may require high-speed charging (high-power charging) of the power storage device.

[0005] Normally, in an uninterruptible power supply, the input capacity (capacity of the first power converter) and the output capacity (capacity of the second power converter) are designed to be approximately the same. Therefore, when high-speed charging of the power storage device is performed while a load is being operated, there is a problem that the DC power generated by the first power converter is insufficient.

[0006] One possible solution to this problem is to select a large-capacity uninterruptible power supply, but this would increase the extra capacity and costs.Another possible solution is to charge the lithium-ion battery using an external charger, but this method also increases costs by the cost of the external charger.

[0007] Therefore, a primary object of the present disclosure is to provide a low-cost uninterruptible power supply capable of fast charging a power storage device while operating a load. [Means for solving the problem]

[0008] The uninterruptible power supply according to the present disclosure includes a first, a second, a third, and a fourth power converter. The first power converter converts AC power supplied from the AC power source into DC power and supplies it to a DC line when the AC power source is healthy. When the AC power source is out of service, the operation of the first power converter is stopped. The second power converter converts DC power received from the DC line into AC power and supplies it to a load. The third power converter stores DC power received from the DC line in a power storage device when the AC power source is healthy, and supplies the DC power of the power storage device to the DC line when the AC power source is out of service. The fourth power converter operates in cooperation with the first power converter in a first case in which high-speed charging of the power storage device is performed, and converts AC power supplied from the AC power source into DC power and supplies it to the DC line. Effect of the Invention

[0009] In the uninterruptible power supply according to the present disclosure, when the power storage device is fast-charged, a fourth power converter is provided that operates in cooperation with the first power converter to convert AC power supplied from the AC power source into DC power and supply it to the DC line. Therefore, since DC power is generated by the first and fourth power converters during fast-charge operation, it is possible to prevent a shortage of DC power and fast-charge the power storage device while operating the load. In addition, it is possible to reduce costs compared to using a large-capacity uninterruptible power supply or adding an external charger. [Brief description of the drawings]

[0010] [Figure 1] 1 is a circuit block diagram showing a configuration of an uninterruptible power supply according to an embodiment of the present disclosure. [Diagram 2] 2 is a circuit diagram showing a configuration of a converter 1 and an inverter 3 shown in FIG. [Diagram 3] 2 is a circuit diagram showing a configuration of a converter 4 included in the bidirectional converter shown in FIG. [Figure 4] FIG. 2 is a block diagram showing a configuration of a control device shown in FIG. [Diagram 5] FIG. 5 is a block diagram showing a configuration of a control circuit shown in FIG. [Figure 6] 3 is a circuit block diagram for explaining the operation of the uninterruptible power supply at startup. FIG. [Figure 7] FIG. 2 is a circuit block diagram for explaining the operation of an uninterruptible power supply during a high-speed charging operation. [Figure 8] 3 is a circuit block diagram for explaining the operation of the uninterruptible power supply during normal operation. FIG. [Figure 9] FIG. 2 is a circuit block diagram for explaining the operation of an uninterruptible power supply during overload operation. [Figure 10] 1 is a circuit block diagram for explaining the operation of an uninterruptible power supply during a power outage of a commercial AC power supply. [Figure 11] FIG. 11 is a circuit block diagram showing a comparative example of the embodiment. [Figure 12]FIG. 13 is a circuit block diagram showing another comparative example of the embodiment. [Figure 13] FIG. 13 is a circuit block diagram showing yet another comparative example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Fig. 1 is a circuit block diagram showing a configuration of an uninterruptible power supply according to an embodiment of the present disclosure. In Fig. 1, the uninterruptible power supply includes an AC input terminal T1, a battery terminal T2, and an AC output terminal T3. The AC input terminal T1 receives AC power of a commercial frequency from a commercial AC power source 15.

[0012] The battery terminal T2 is connected to a battery 16 (power storage device). The battery 16 stores DC power. A lithium ion battery is used as the battery 16. However, a lead storage battery may be used instead of the lithium ion battery, and an electric double layer capacitor or a flywheel may be connected instead of the battery 16. The AC output terminal T3 is connected to a load 17. The load 17 is driven by AC power supplied from an uninterruptible power supply.

[0013] Note that this uninterruptible power supply actually receives a three-phase AC voltage from a commercial AC power supply 15 and supplies the three-phase AC voltage to a load 17, but in order to simplify the drawings and explanation, FIG. 1 shows only the parts related to a one-phase AC voltage.

[0014] The uninterruptible power supply further includes switches S1 to S5, capacitors C1 to C4, reactors L1 to L4, current detectors CD1 to CD4, converters 1 and 4, a DC line DL, a bidirectional chopper 2, an inverter 3, an operation unit 5, and a control device 6.

[0015] The switch S1 and the reactor L1 are connected in series between the AC input terminal T1 and the AC node 1a of the converter 1. The switch S1 is controlled by the control device 6. When AC power is normally supplied from the commercial AC power supply 15 (when the commercial AC power supply 15 is healthy), the switch S1 is turned on. When AC power is no longer normally supplied from the commercial AC power supply 15 (when the commercial AC power supply 15 has a power outage), the switch S1 is turned off. The current detector CD1 detects a current Ii flowing between the commercial AC power supply 15 and the converter 1, and outputs a signal Iif indicating the detected value to the control device 6.

[0016] The instantaneous value of the AC input voltage VI appearing at the AC input terminal T1 is detected by the control device 6. The control device 6 determines whether or not a power outage has occurred based on the detected value of the AC input voltage VI. The control device 6 also controls the converter 1 and the like in synchronization with the AC input voltage VI.

[0017] Capacitor C1 is connected between a node N1 between switch S1 and reactor L1 and neutral point NP. Capacitor C1 and reactor L1 configure an AC filter. This AC filter is a low-pass filter that passes AC power of a commercial frequency from commercial AC power supply 15 to converter 1 and prevents a signal of a switching frequency generated by converter 1 from passing to commercial AC power supply 15.

[0018] The converter 1 is a well-known device including a plurality of transistors and a plurality of diodes, and is controlled by a control device 6. When the commercial AC power supply 15 is normal, the converter 1 converts AC power into DC power and outputs it to a DC node 1d. The DC node 1d is connected to a DC line DL. The output voltage of the converter 1 can be controlled to a desired value. When the commercial AC power supply 15 experiences a power outage, the operation of the converter 1 is stopped.

[0019] The capacitor C1, the reactor L1, and the converter 1 constitute an AC / DC converter 11 (first power converter) that converts AC power into DC power. The capacitor C2 is connected to the DC line DL and smoothes the voltage of the DC line DL. The instantaneous value of the DC voltage VD appearing on the DC line DL is detected by the control device 6.

[0020] The control device 6 controls the converter 1 so that the DC voltage VD of the DC line DL becomes the reference voltage VDR when the commercial AC power supply 15 is normal, and stops the operation of the converter 1 when the commercial AC power supply 15 experiences a power outage.

[0021] The DC line DL is connected to a high-voltage side node 2a of the bidirectional chopper 2, and a low-voltage side node 2b of the bidirectional chopper 2 is connected to a battery terminal T2 via a reactor L2 and a switch S2. The switch S2 is turned on when the uninterruptible power supply is in use, and turned off, for example, during maintenance of the uninterruptible power supply and the battery 16. The reactor L2 smoothes the current Ib flowing between the bidirectional chopper 2 and the battery 16.

[0022] The bidirectional chopper 2 is a well-known device including a plurality of transistors and a plurality of diodes, and is controlled by a control device 6. The capacitance of the bidirectional chopper 2 is set to the same value as the capacitance of the converter 1.

[0023] Basically, the bidirectional chopper 2 stores the DC power received from the DC line DL in the battery 16 when the commercial AC power supply 15 is normal, and supplies the DC power of the battery 16 to the DC line DL when the commercial AC power supply 15 is in a power outage. However, even when the commercial AC power supply 15 is normal, during overload operation, the bidirectional chopper 2 supplies the DC power of the battery 16 to the inverter 3 via the DC line DL.

[0024] When storing DC power in the battery 16, the bidirectional chopper 2 steps down the DC voltage VD of the DC line DL and supplies it to the battery 16. Also, when supplying the DC power of the battery 16 to the inverter 3, the bidirectional chopper 2 steps up the voltage VB between the terminals of the battery 16 and outputs it to the DC line DL.

[0025] The bidirectional chopper 2 and the reactor L2 constitute a DC / DC converter 12 (third power converter) that exchanges DC power between the DC line DL and the battery 16.

[0026] The current detector CD2 detects the current Ib flowing between the bidirectional chopper 2 and the battery 16, and outputs a signal Ibf indicating the detected value to the control device 6. The instantaneous value of the voltage VB between the terminals of the battery 16 appearing at the battery terminal T2 is detected by the control device 6.

[0027] Basically, when the commercial AC power supply 15 is normal, the control device 6 controls the bidirectional chopper 2 so that the battery voltage VB becomes the reference voltage VBR, and when the commercial AC power supply 15 fails, the control device 6 controls the bidirectional chopper 2 so that the DC voltage VD of the DC line DL becomes the reference voltage VDR.

[0028] However, even when the commercial AC power supply 15 is normal, during overload operation, the control device 6 controls the bidirectional chopper 2 so that the DC voltage VD of the DC line DL becomes the reference voltage VDR.

[0029] Also, when the battery voltage VB is equal to or higher than the lower limit voltage VBL (VB≧VBL), the control device 6 controls the bidirectional chopper 2 to charge the battery 16 at a normal speed, and when the battery voltage VB is lower than the lower limit voltage VBL (VB<VBL), the control device 6 controls the bidirectional chopper 2 to charge the battery 16 at a speed higher than normal. The DC line DL is connected to the DC node 3a of the inverter 3.

[0030] The inverter 3 is a well-known device including a plurality of transistors and a plurality of diodes, and is controlled by the control device 6. The circuit configuration of the inverter 3 is the same as that of the converter 1, and the capacity (i.e., size) of the inverter 3 is the same as that of the converter 1. The inverter 3 converts DC power received from the DC line DL via a DC node 3a into AC power of a commercial frequency and outputs it to an AC node 3b. The output voltage of the inverter 3 can be controlled to a desired value.

[0031] The AC node 3b of the inverter 3 is connected to one terminal (node ​​N2) of a switch S3 via a reactor L3, and the other terminal of the switch S3 is connected to an AC output terminal T3. The capacitor C3 is connected between the node N2 and a neutral point NP.

[0032] Reactor L3 and capacitor C3 configure an AC filter. This AC filter is a low-pass filter that passes commercial frequency AC power generated by inverter 3 to AC output terminal T3 and prevents switching frequency signals generated by inverter 3 from passing to AC output terminal T3.

[0033] The inverter 3, the reactor L3, and the capacitor C3 constitute a DC / AC converter 13 (second power converter) that converts DC power into AC power. The circuit configuration of the DC / AC converter 13 is the same as that of the AC / DC converter 11, and the capacity (i.e., size) of the DC / AC converter 13 is the same as that of the AC / DC converter 11.

[0034] The switch S3 is controlled by the control device 6, and is turned on when the uninterruptible power supply is operating, and is turned off when the uninterruptible power supply is stopped, etc. The instantaneous value of the AC output voltage VO appearing at the AC output terminal T3 is detected by the control device 6.

[0035] The current detector CD3 detects a current Io flowing between the inverter 3 and the load 17, and provides a signal Iof indicating the detected value to the control device 6. The control device 6 controls the inverter 3 so that the AC output voltage VO becomes a sinusoidal reference voltage VOR.

[0036] The switch S4 is connected between the AC input terminal T1 and the AC node N3, and is controlled by the control device 6. The switch S4 is turned on during a high-speed charging operation in which the battery 16 is quickly charged while the load 17 is being operated, and is turned off during other periods.

[0037] The switch S5 is connected between the AC node N3 and the AC output terminal T3, and is controlled by the control device 6. The switch S5 is turned on during normal operation and overload operation. During normal operation, the rated power Pc of the load 17 is supplied to the load 17, and during overload operation, power greater than the rated power Pc is supplied to the load 17. During a power outage of the commercial AC power supply 15, both the switches S4 and S5 are turned off. The switches S4 and S5 constitute an embodiment of a switching circuit that connects the AC node N3 to the commercial AC power supply 15 or the load 17.

[0038] The DC line DL is also connected to a DC node 4a of a converter 4. The converter 4 is a well-known converter including a plurality of transistors and a plurality of diodes, and is controlled by a control device 6.

[0039] The circuit configuration of converter 4 is the same as that of each of converter 1 and inverter 3, and the capacity (i.e., size) of converter 4 is smaller than the capacity (i.e., size) of each of converter 1 and inverter 3. For example, if the capacity of each of converter 1 and inverter 3 is 100%, the capacity of converter 4 is 50%.

[0040] The AC node 4b of the converter 4 is connected to the AC node N3 via the reactor L4. The capacitor C4 is connected between the AC node N3 and the neutral point NP. The reactor L4 and the capacitor C4 configure an AC filter. This AC filter is a low-pass filter that passes AC power of the commercial frequency supplied from the commercial AC power source 15 or the converter 4 and prevents a signal of the switching frequency generated by the converter 4 from passing to the AC node N3.

[0041] The converter 4, the reactor L4, and the capacitor C4 configure a bidirectional converter 14 (fifth power converter) that selectively executes one of an AC / DC conversion mode in which the AC power supplied from the commercial AC power supply 15 via the AC node N3 is converted into DC power and supplied to the DC line DL, and a DC / AC conversion mode in which the DC power received from the DC line DL is converted into AC power and supplied to the load 17 via the AC node N3.

[0042] The circuit configuration of bidirectional converter 14 is identical to the circuit configurations of AC / DC converter 11 and DC / AC converter 13, and the capacity (i.e., size) of bidirectional converter 14 is smaller than the capacity (i.e., size) of each of AC / DC converter 11 and DC / AC converter 13. For example, if the capacity of each of AC / DC converter 11 and DC / AC converter 13 is 100%, the capacity of bidirectional converter 14 is 50%. Switches S4, S5 and bidirectional converter 14 constitute an embodiment of a fourth power converter.

[0043] The instantaneous value of the AC voltage VS appearing at the AC node N3 is detected by the control device 6. The current detector CD4 detects a current Is flowing through the reactor L4, and provides the control device 6 with a signal Isf indicating the detected value.

[0044] During the high-speed charging operation, the control device 6 controls the converters 1 and 4 so that the DC voltage VD of the DC line DL becomes the reference voltage VDR. At this time, the ratio between the output of the converter 4 and the output of the converter 1 is controlled to be the ratio between the capacity of the converter 4 and the capacity of the converter 1 (for example, 1 / 2).

[0045] During overload operation, the control device 6 controls the converter 4 so that the AC voltage VS appearing at the AC node N3 becomes the sinusoidal reference voltage VOR. At this time, the ratio between the output of the converter 4 and the output of the inverter 3 is controlled to be the ratio between the capacity of the converter 4 and the capacity of the inverter 3 (for example, 1 / 2).

[0046] The operation unit 5 includes a plurality of buttons operated by a user of the uninterruptible power supply, an image display unit that displays various information, etc. By operating the operation unit 5, the user can set various voltages VDR, VBR, VOR, and VBL, turn the power supply of the uninterruptible power supply on and off, and operate the uninterruptible power supply automatically or manually.

[0047] In addition, the control device 6 controls the entire uninterruptible power supply based on the AC input voltage VI, the AC input current Ii, the DC voltage VD, the battery voltage VB, the battery current Ib, the AC output voltage VO, the AC output current Io, the AC voltage VS, the AC current Is, the reference voltages VDR, VBR, VOR, the lower limit voltage VBL, a signal from the operation unit 5, and the like.

[0048] Fig. 2 is a circuit diagram showing the configuration of the converter 1 and the inverter 3. Fig. 1 shows only a portion related to one phase of the three-phase AC voltage, but Fig. 2 shows a portion related to the three-phase AC voltage. Also, Fig. 1 shows only the positive DC line DL, but Fig. 2 shows the negative DC line DLn as well.

[0049] 2, converter 1 includes IGBTs (Insulated Gate Bipolar Transistors) Q1-Q6 and diodes D1-D6. The IGBTs constitute switching elements. The collectors of IGBTs Q1-Q3 are all connected to a positive DC line DL via DC node 1b, and the emitters thereof are connected to AC nodes 1a, 1c, and 1d, respectively.

[0050] AC nodes 1a, 1c, and 1d are provided corresponding to three-phase AC voltages supplied from a commercial AC power supply 15. The collectors of IGBTs Q4 to Q6 are connected to AC nodes 1a, 1c, and 1d, respectively, and their emitters are both connected to a negative DC line DLn. Diodes D1 to D6 are connected in anti-parallel to IGBTs Q1 to Q6, respectively. Capacitor C2 is connected between DC lines DL and DLn.

[0051] IGBTs Q1 and Q4 are controlled by gate signals A1 and B1, IGBTs Q2 and Q5 are controlled by gate signals A2 and B2, and IGBTs Q3 and Q6 are controlled by gate signals A3 and B3. Gate signals B1, B2, and B3 are inverted versions of gate signals A1, A2, and A3, respectively.

[0052] IGBTs Q1 to Q3 turn on when gate signals A1, A2, and A3 are set to "H" level, and turn off when gate signals A1, A2, and A3 are set to "L" level. IGBTs Q4 to Q6 turn on when gate signals B1, B2, and B3 are set to "H" level, and turn off when gate signals B1, B2, and B3 are set to "L" level.

[0053] Each of the gate signals A1, B1, A2, B2, A3, and B3 is a pulse signal train and a PWM (Pulse Width Modulation) signal. The phases of the gate signals A1 and B1, the gate signals A2 and B2, and the gate signals A3 and B3 are basically shifted by 120 degrees each. The gate signals A1, B1, A2, B2, A3, and B3 are generated by the control device 6.

[0054] By turning each of IGBTs Q1 to Q6 on and off at a predetermined timing using gate signals A1, B1, A2, B2, A3, and B3, and adjusting the on-time of each of IGBTs Q1 to Q6, it is possible to convert the three-phase AC voltage applied to AC nodes 1a, 1c, and 1d into a desired DC voltage VD (terminal voltage of capacitor C2).

[0055] Inverter 3 includes IGBTs Q11-Q16 and diodes D11-D16. The IGBTs constitute switching elements. The collectors of IGBTs Q11-Q13 are all connected to a positive side DC line DL via a DC node 3a, and the emitters thereof are connected to AC nodes 3b, 3c, and 3d, respectively.

[0056] AC nodes 3b, 3c, and 3d are provided corresponding to the three-phase AC voltages supplied to load 17. The collectors of IGBTs Q14 to Q16 are connected to AC nodes 3b, 3c, and 3d, respectively, and their emitters are both connected to the negative DC line DLn. Diodes D11 to D16 are connected in anti-parallel to IGBTs Q11 to Q16, respectively.

[0057] IGBTs Q11 and Q14 are controlled by gate signals X1 and Y1, IGBTs Q12 and Q15 are controlled by gate signals X2 and Y2, and IGBTs Q13 and Q16 are controlled by gate signals X3 and Y3. Gate signals Y1, Y2, and Y3 are inverted signals of gate signals X1, X2, and X3, respectively.

[0058] IGBTs Q11-Q13 turn on when gate signals X1, X2, and X3 are set to "H" level, and turn off when gate signals X1, X2, and X3 are set to "L" level. IGBTs Q14-Q16 turn on when gate signals Y1, Y2, and Y3 are set to "H" level, and turn off when gate signals Y1, Y2, and Y3 are set to "L" level.

[0059] Each of the gate signals X1, Y1, X2, Y2, X3, and Y3 is a pulse signal train, that is, a PWM signal. The phases of the gate signals X1 and Y1, the gate signals X2 and Y2, and the gate signals X3 and Y3 are basically shifted by 120 degrees each. The gate signals X1, Y1, X2, Y2, X3, and Y3 are generated by the control device 6.

[0060] For example, when IGBT Q11 and Q15 are turned on, DC line DL is connected to AC node 3b via IGBT Q11, and AC node 3c is connected to DC line DLn via IGBT Q15, and a positive voltage is output between AC nodes 3b and 3c.

[0061] Furthermore, when IGBT Q12, Q14 are turned on, DC line DL is connected to AC node 3c via IGBT Q12, and AC node 3b is connected to DC line DLn via IGBT Q14, and a negative voltage is output between output nodes 3b, 3c.

[0062] By turning on and off each of IGBTs Q11 to Q16 at a predetermined timing using gate signals X1, Y1, X2, Y2, X3, and Y3, and adjusting the on-time of each of IGBTs Q11 to Q16, it is possible to convert the DC voltage VD between DC lines DL and DLn into a three-phase AC voltage.

[0063] Fig. 3 is a circuit diagram showing a configuration of the converter 4 included in the bidirectional converter 14. Fig. 1 shows only a portion related to one phase of the three-phase AC voltage, but Fig. 3 shows a portion related to the three-phase AC voltage. Also, Fig. 1 shows only the positive DC line DL, but Fig. 3 also shows the negative DC line DLn.

[0064] 3, converter 4 includes IGBTs Q21-Q26 and diodes D21-D26. The IGBTs constitute switching elements. The collectors of IGBTs Q21-Q23 are all connected to a positive-side DC line DL via DC node 4a, and the emitters thereof are connected to AC nodes 4b, 4c, and 4d, respectively.

[0065] AC nodes 4b, 4c, and 4d are provided corresponding to three-phase AC voltages. The collectors of IGBTs Q24 to Q26 are connected to AC nodes 4b, 4c, and 4d, respectively, and their emitters are both connected to a negative DC line DLn. Diodes D21 to D26 are connected in anti-parallel to IGBTs Q21 to Q26, respectively. Capacitor C2 is connected between DC lines DL and DLn.

[0066] IGBTs Q21 and Q24 are controlled by gate signals E1 and F1, IGBTs Q22 and Q25 are controlled by gate signals E2 and F2, and IGBTs Q23 and Q26 are controlled by gate signals E3 and F3. Gate signals F1, F2, and F3 are inverted versions of gate signals E1, E2, and E3, respectively.

[0067] IGBTs Q21-Q23 turn on when gate signals E1, E2, E3 are set to "H" level, and turn off when gate signals E1, E2, E3 are set to "L" level. IGBTs Q24-Q26 turn on when gate signals F1, F2, F3 are set to "H" level, and turn off when gate signals F1, F2, F3 are set to "L" level.

[0068] Each of the gate signals E1, F1, E2, F2, E3, and F3 is a pulse signal train, that is, a PWM signal. The phases of the gate signals E1 and F1, the gate signals E2 and F2, and the gate signals E3 and F3 are basically shifted by 120 degrees each. The gate signals E1, F1, E2, F2, E3, and F3 are generated by the control device 6.

[0069] During fast charging operation, gate signals E1, F1, E2, F2, E3, and F3 turn each of IGBTs Q21-Q26 on and off at predetermined timing, and by adjusting the on-time of each of IGBTs Q21-Q26, it is possible to convert the three-phase AC voltage applied to AC nodes 4b, 4c, and 4d from commercial AC power supply 15 into the desired DC voltage VD (terminal-to-terminal voltage of capacitor C2).

[0070] During overload operation, gate signals E1, F1, E2, F2, E3, and F3 turn each of IGBTs Q21 to Q26 on and off at predetermined timing, and by adjusting the on-time of each of IGBTs Q21 to Q26, it is possible to convert the DC voltage VD between DC lines DL and DLn into a three-phase AC voltage.

[0071] 2 and 3, the circuit configuration of converter 1, the circuit configuration of inverter 3, and the circuit configuration of converter 4 are the same. Also, similar to conventional uninterruptible power supplies, the capacity (i.e., size) of converter 1 and the capacity (i.e., size) of inverter 3 are designed to be the same.

[0072] Furthermore, the capacity (i.e., size) of converter 4 is smaller than the capacity (i.e., size) of each of converter 1 and inverter 3. For example, if the capacity (i.e., size) of each of converter 1 and inverter 3 is 100%, the capacity (i.e., size) of converter 4 is 50%.

[0073] In this way, by making the circuit configurations of converters 1 and 4 the same and making the capacity of converter 4 50% of the capacity of converter 1, it is possible to easily control converters 1 and 4 so that converters 1 and 4 operate in coordination during fast charging operation and the output of converter 4 is 50% of the output of converter 1.

[0074] In addition, by making the circuit configurations of converter 4 and inverter 3 the same and making the capacity of converter 4 50% of the capacity of inverter 3, it becomes possible to easily control converter 4 and inverter 3 so that they operate in conjunction with each other during overload operation and the output of converter 4 becomes 50% of the output of inverter 3.

[0075] 4 is a block diagram showing a main part of the control device 6. In FIG. 4, the control device 6 includes voltage detectors 21-25, a power failure detector 26, comparators 27 and 28, and a control circuit 29.

[0076] The voltage detector 21 detects an instantaneous value of the AC input voltage VI supplied from the commercial AC power supply 15, 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 an instantaneous value of the AC output voltage VO supplied to the load 17, and outputs a signal VOf indicating the detected value to the control circuit 29. The voltage detector 23 detects an instantaneous value of the AC voltage VS appearing at the AC node N3, and outputs a signal VSf indicating the detected value to the control circuit 29.

[0077] The voltage detector 24 detects the instantaneous value of the DC voltage VD of the DC line DL, and outputs a signal VDf indicative of 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 16, and outputs a signal VBf indicative of the detected value to the control circuit 29. Output signals Iif, Ibf, Iof, Isf of the current detectors CD1 to CD4 (FIG. 1) are provided to the control circuit 29.

[0078] The power failure detector 26 detects whether or not a power failure has occurred in the commercial AC power supply 15 based on the output signal VIf of the voltage detector 21, and outputs a signal φ26 indicating the detection result to the control circuit 29. When the commercial AC power supply 15 is healthy, the signal φ26 is set to the "H" level. When a power failure has occurred in the commercial AC power supply 15, the signal φ26 is set to the "L" level.

[0079] For example, when the AC input voltage VI is higher than a lower limit, the power failure detector 26 determines that the commercial AC power supply 15 is healthy and sets the signal φ26 to the “H” level. When the AC input voltage VI is lower than a lower limit, the power failure detector 26 determines that a power failure has occurred in the commercial AC power supply 15 and sets the signal φ26 to the “L” level.

[0080] The comparator 27 compares the battery voltage VB indicated by the signal VBf with the lower limit voltage VBL, and provides a signal φ27 indicating the comparison result to the control circuit 29. When the battery voltage VB is equal to or higher than the lower limit voltage VBL (VB≧VBL), the signal φ27 is set to the “H” level.

[0081] When the DC voltage VB is lower than the lower limit voltage VBL (VBL>VB), the signal φ27 is set to the "L" level. The "L" level of the signal φ27 is a condition for performing a high-speed charging operation of the battery 16. When the signal φ27 is at the "H" level, the high-speed charging operation of the battery 16 is not performed.

[0082] The comparator 28 compares the magnitude of the AC output current Is of the converter 4 indicated by the signal Isf with the upper limit current IsH, and provides a signal φ28 indicating the comparison result to the control circuit 29. When the AC output current Is of the converter 4 is equal to or lower than the upper limit current IsH (Is≦IsH), the signal φ28 is set to the “L” level.

[0083] When the AC output current Is of converter 4 exceeds the upper limit current IsH (Is>IsH), signal φ28 is set to "H" level. When signal φ28 is at "H" level, it is determined that an overload operation is performed. When signal φ28 is at "L" level, the overload operation is not performed.

[0084] For example, when the ratio between the capacity of converter 4 and the capacity of inverter 3 is 1 / 2 and the AC output current Is of converter 4 is controlled to 1 / 2 of the AC output current Io of inverter 3, the upper limit current IsH is set to a value 1 / 3 times the rated current Ic of load 17.

[0085] When the AC output current Is of the converter 4 reaches the upper limit current IsH=Ic / 3, the AC output current Iof of the inverter 3 becomes 2 / 3 times the rated current Ic of the load 17, and the rated current Ic is supplied to the load 17 from the converter 4 and the inverter 3. In this case, the signal φ28 becomes the "L" level, and overload operation is not performed.

[0086] When the AC output current Is of the converter 4 exceeds the upper limit current IsH=Ic / 3, the AC output current Iof of the inverter 3 becomes greater than 2 / 3 times the rated current Ic of the load 17, and a current greater than the rated current Ic is supplied from the converter 4 and the inverter 3 to the load 17. In this case, the signal φ28 becomes "H" level, and overload operation is performed.

[0087] Fig. 5 is a block diagram showing the main parts of control circuit 29. In Fig. 5, control circuit 29 includes control units 31-35 and a communication line 36. Control units 31-35 and operation unit 5 are connected to each other via communication line 36. Control units 31-35 send and receive various signals via communication line 36 and cooperate with each other to control the entire uninterruptible power supply.

[0088] The control unit 31 controls the switches S1 to S3 based on the output signal φ26 of the power failure detector 26 and a signal from the operation unit 5. When the signal φ26 is at the “H” level (when the commercial AC power supply 15 is healthy), the control unit 31 turns on the switches S1 to S3.

[0089] When the signal φ26 is at the “L” level (when the commercial AC power supply 15 is out of power), the control unit 31 turns off the switch S1 and keeps the switches S2 and S3 in the on state. Furthermore, the control unit 31 turns on and off each of the switches S1 to S3 individually during manual operation in accordance with a signal from the operation unit 5.

[0090] The control unit 32 generates gate signals A1 to A3, B1 to B3 (Figure 2) based on output signals VIf, VDf of the voltage detectors 21, 24, output signals Iif, Isf of the current detectors CD1, CD4, output signals φ26, φ27 of the power outage detector 26 and the comparator 27, and a signal from the operation unit 5, to control the converter 1.

[0091] When signals φ26 and φ27 are both at the “H” level (during normal operation and overload operation), the control unit 32 controls the converter 1 based on the signals VIf, VDf, and Iif so that the DC voltage VD of the DC line DL becomes the reference voltage VDR.

[0092] When signal φ26 is at the “L” level (when commercial AC power supply 15 is at a power outage), control unit 32 stops the operation of converter 1. At this time, gate signals A1 to A3, B1 to B3 are all set to the “L” level, and IGBTs Q1 to Q6 (FIG. 2) of converter 1 are all turned off.

[0093] When signals φ26 and φ27 are at the “H” level and the “L” level, respectively (during fast charging operation), control unit 32 operates in cooperation with control unit 35 and controls converter 1 based on signals VIf, VDf, Iif, and Isf so that DC voltage VD of DC line DL becomes reference voltage VDR.

[0094] At this time, the converter 1 is controlled so that the ratio (Is / Ii) of the current Is flowing through the converter 4 to the current Ii flowing through the converter 1 becomes the ratio (for example, 1 / 2) of the capacity of the converter 4 to the capacity of the converter 1. Furthermore, the control unit 32 starts or stops the converter 1 during manual operation according to a signal from the operation unit 5.

[0095] The control unit 33 controls the bidirectional chopper 2 based on the output signals VDf, VBf of the voltage detectors 24, 25, the output signal Ibf of the current detector CD2, the output signals φ26, φ27, φ28 of the power outage detector 26 and the comparators 27, 28, and a signal from the operation unit 5.

[0096] When the signals φ26, φ27, and φ28 are at the “H” level, the “H” level, and the “L” level, respectively (during normal operation), the control unit 33 controls the bidirectional chopper 2 based on the signals VBf and Ibf so that the battery voltage VB becomes the reference voltage VBR.

[0097] When the signals φ26, φ27, and φ28 are at the “H” level, the “L” level, and the “L” level, respectively (during fast charging operation), the control unit 33 controls the bidirectional chopper 2 based on the signals VBf and Ibf so that the battery voltage VB becomes the reference voltage VBR.

[0098] Here, during normal operation, the control unit 33 controls the bidirectional chopper 2 to charge the battery 16 at a normal speed, and during high-speed charging, the control unit 33 controls the bidirectional chopper 2 to charge the battery 16 at a higher speed than normal.

[0099] For example, during normal operation, the control unit 33 controls the bidirectional chopper 2 so that a current Ib=K1×(VBR−VB), which is a value obtained by multiplying a difference ΔVB=VBR−VB between a reference voltage VBR and a battery voltage VB by a gain K1, flows from the DC line DL to the battery 16. Here, K1 is a positive real number.

[0100] Furthermore, during the high-speed charging operation, the control unit 33 controls the bidirectional chopper 2 so that a current Ib=K2×(VBR−VB), which is a value obtained by multiplying a difference ΔVB=VBR−VB between the reference voltage VBR and the battery voltage VB by a gain K2, flows from the DC line DL to the battery 16. Here, K2 is a positive real number larger than K1.

[0101] Therefore, during high-speed charging operation, a larger charging current can be passed through the battery 16, and the battery 16 can be charged at a higher speed than during normal driving operation.

[0102] When the signals φ26, φ27, and φ28 are all at the “H” level (during overload operation), the control unit 33 controls the bidirectional chopper 2 based on the signals VDf and Ibf so that the DC voltage VD of the DC line DL becomes the reference voltage VDR.

[0103] When the signal φ26 is at the “L” level (when the commercial AC power supply 15 is at a power outage), the control unit 33 controls the bidirectional chopper 2 based on the signals VBf and Ibf so that the DC voltage VD of the DC line DL becomes the reference voltage VDR. Also, the control unit 33 starts or stops the bidirectional chopper 2 during manual operation according to a signal from the operation unit 5.

[0104] The control unit 34 generates gate signals X1 to X3, Y1 to Y3 (Figure 2) based on output signals VIf, VOf of the voltage detectors 21, 22, an output signal Iof of the current detector CD3, an output signal φ26 of the power outage detector 26, and a signal from the operation unit 5, to control the inverter 3.

[0105] When the signal φ26 is at the “H” level (when the commercial AC power supply 15 is healthy), the control unit 34 operates in cooperation with the control unit 35, operates in synchronization with the signal VIf, and controls the inverter 3 based on the signals VOf and Iof so that the AC output voltage VO becomes the sinusoidal reference voltage VOR.

[0106] At this time, the inverter 3 is controlled so that the ratio (Is / Io) of the current Is flowing through the converter 4 to the current Io flowing through the inverter 3 becomes the ratio of the capacity of the converter 4 to the capacity of the inverter 3 (for example, 1 / 2).

[0107] When the signal φ26 is at the “L” level (when the commercial AC power supply 15 is at a power outage), the control unit 34 operates in synchronization with the signal VIf and controls the inverter 3 based on the signals VOf and Iof so that the AC output voltage VO becomes the sinusoidal reference voltage VOR.

[0108] The control unit 35 controls the switches S4, S5 based on output signals VIf, VOf, VSf, VDf of the voltage detectors 21-24, output signals Iif, Iof, Isf of the current detectors CD1, CD3, CD4, output signals φ26, φ27, φ28 of the power failure detector 26 and comparators 27, 28, and a signal from the operation unit 5, and also generates gate signals E1-E3, F1-F3 (Figure 3) and controls the converter 4.

[0109] When signals φ26, φ27, and φ28 are at the “H” level, the “L” level, and the “L” level, respectively (during high-speed charging operation), control unit 35 turns on switch S4 and turns off switch S5, thereby connecting bidirectional converter 14 in parallel with AC / DC converter 11. Control unit 35 also operates in cooperation with control unit 22 to control converter 4 so that DC voltage VD of DC line DL becomes reference voltage VDR.

[0110] At this time, converter 4 is controlled so that the ratio (Is / Ii) of current Is flowing through converter 4 to current Ii flowing through converter 1 becomes the ratio of the capacity of converter 4 to the capacity of converter 1 (for example, 1 / 2).

[0111] When signals φ26 and φ27 are both at the “H” level (during normal operation and overload operation), regardless of the logical level of signal φ28, control unit 35 turns off switches S4 and S5 and controls converter 4 to make AC voltage VS equal to AC output voltage VO, then turns on switch S5 and connects bidirectional converter 14 in parallel to DC / AC converter 13. Control unit 35 also operates in cooperation with control unit 24 to control converter 4 so that AC voltage VS becomes sinusoidal reference voltage VOR.

[0112] At this time, converter 4 is controlled so that the ratio (Is / Io) of current Is flowing through converter 4 to current Io flowing through inverter 3 becomes the ratio of the capacity of converter 4 to the capacity of inverter 3 (for example, 1 / 2).

[0113] When the signal φ26 is at the “L” level (when the commercial AC power supply 15 is experiencing a power outage), the control unit 35 turns off the switches S4 and S5 to electrically disconnect the AC node N3 from the commercial AC power supply 15 and the load 17.

[0114] Furthermore, control unit 35 turns on and off switches S4 and S5, respectively, in accordance with a signal from operation unit 5 to operate or stop converter 4. For example, a user of the uninterruptible power supply can operate operation unit 5 to perform only one of the high-speed charging operation and the overload operation.

[0115] When fast charging is performed but overload operation is not performed, switch S5 is fixed to the off state and converter 4 performs only AC / DC conversion operation. Conversely, when overload operation is performed but fast charging is not performed, switch S4 is fixed to the off state and converter 4 performs only DC / AC conversion operation.

[0116] In addition, a user of the uninterruptible power supply can operate the operation unit 5 to stop the operation of the converter 4, turn off the switch S3, and turn on the switches S4 and S5, thereby supplying AC power from the commercial AC power source 15 to the load 17 via the switches S4 and S5.

[0117] Next, the operation of this uninterruptible power supply will be described. Fig. 6 is a circuit block diagram for explaining the operation of the uninterruptible power supply at start-up. In Fig. 6, for the sake of simplicity of the drawing and explanation, the terminals T1 to T3, the capacitors C1, C3, C4, the reactors L1 to L4, the current detectors CD1 to CD4, the operation unit 5, and the control device 6 (Fig. 1) are omitted.

[0118] Also, the capacitance of converter 1, the capacitance of bidirectional chopper 2, and the capacitance of inverter 3 are set to the same value, and the ratio of the capacitance of converter 4 to the capacitance of each of converter 1, bidirectional chopper 2, and inverter 3 is set to 1 / 2. For this reason, converter 1, bidirectional chopper 2, and inverter 3 are shown as blocks of the same size, and converter 4 is shown as a block smaller than those blocks.

[0119] Also, before startup, the terminal voltage VB of the battery 16 is assumed to be lower than the lower limit voltage VBL, and the output signal φ27 of the comparator 27 (FIG. 4) is assumed to be at the “L” level. Also, at startup, the commercial AC power supply 15 is assumed to be healthy, and the output signal φ26 of the power failure detector 26 is assumed to be at the “H” level.

[0120] When an instruction to start up the uninterruptible power supply is given using operation unit 5 (FIGS. 1 and 5), capacitor C2 is pre-charged to a predetermined voltage by a pre-charging circuit (not shown), and then switch S1 is turned on by control unit 31 (FIG. 5), and operation of converter 1 is started by control unit 32 (FIG. 5). Converter 1 converts AC power supplied from commercial AC power supply 15 via switch S1 into DC power and supplies it to DC line DL.

[0121] Next, the control unit 35 (FIG. 5) turns on the switch S4 and starts the operation of the converter 4. At this time, in order to prevent an inrush current from flowing from the commercial AC power supply 15 to the converters 1 and 4, the switch S4 is turned on after a predetermined time has elapsed since the switch S1 was turned on. The converter 4 operates in cooperation with the converter 1, converts the AC power supplied from the commercial AC power supply 15 via the switch S4 into DC power and supplies it to the DC line DL.

[0122] Next, the operation of the inverter 3 is started by the control unit 34 (FIG. 5), and the switch S3 is turned on by the control unit 31. The inverter 3 converts the DC power received from the DC line DL into AC power, and supplies it to the load 17 via the switch S3.

[0123] Next, the control unit 31 turns on the switch S2, and the control unit 33 (FIG. 5) starts the operation of the bidirectional chopper 2. As a result, a current flows from the DC line DL through the bidirectional chopper 2 and the switch S2 to the battery 16, and high-speed charging of the battery 16 starts.

[0124] Fig. 7 is a circuit block diagram for explaining the operation of the uninterruptible power supply during high-speed charging operation. In Fig. 7, the arrows indicate the paths through which power is supplied. AC power supplied from a commercial AC power supply 15 is converted to DC power by converters 1 and 4 and supplied to a DC line DL. The DC power supplied to the DC line DL is stored in a battery 16 via a bidirectional chopper 2, and is also converted to AC power by an inverter 3 and supplied to a load 17.

[0125] During fast charging operation, control units 32, 35 operate in cooperation with each other to control converters 1, 4 so that the ratio (Is / Ii) of current Is flowing through converter 4 to current Ii flowing through converter 1 becomes the ratio of the capacity of converter 4 to the capacity of converter 1 (here, 1 / 2).

[0126] Therefore, if the rated power Pc of the load 17 is 100%, as shown in FIG. 7, it is possible to generate 150% DC power by the converters 1 and 4, and supply 100% AC power to the load 17 by the inverter 3, while supplying 50% DC power to the battery 16.

[0127] When the battery voltage VB rises and exceeds the lower limit voltage VBL, the output signal φ27 of the comparator 27 (FIG. 4) is set to the “H” level. When the signal φ27 is set to the “H” level, the operation of the converter 4 is temporarily stopped by the control unit 35, and the switch S4 is turned off.

[0128] Next, the control unit 35 starts the operation of the converter 4, and controls the converter 4 so that the AC voltage VS at the AC node N3 coincides with the AC output voltage VO. When the AC voltage VS coincides with the AC output voltage VO, the control unit 35 turns on the switch S5, and the control units 32 and 35 operate the inverter 3 and the converter 4 in parallel.

[0129] At this time, converter 4 operates in cooperation with inverter 3, converts DC power received from DC line DL into AC power, and supplies it to load 17 via switch S5. Control units 34, 35 operate in cooperation with each other, and control inverter 3 and converter 4 so that the ratio (Is / Io) of output current Is of converter 4 to output current Io of inverter 3 becomes the ratio of the capacity of converter 4 to the capacity of inverter 3 (here, 1 / 2).

[0130] During normal operation in which the load 17 is operated at the rated power Pc, the control unit 33 controls the bidirectional chopper 2 so that the battery voltage VB becomes the reference voltage VBR. Figure 8 is a circuit block diagram for explaining the operation of the uninterruptible power supply during normal operation.

[0131] 8, AC power supplied from a commercial AC power supply 15 is converted into DC power by a converter 1 and supplied to a DC line DL. The DC power supplied to the DC line DL is stored in a battery 16 via a bidirectional chopper 2, and is also converted into AC power by an inverter 3 and a converter 4 and supplied to a load 17.

[0132] If the rated power Pc of the load 17 is 100%, then, as shown in Fig. 8, 100% AC power is supplied from the commercial AC power supply 15 to the converter 1, 100% DC power is supplied from the converter 1 to the DC line DL, (2 / 3) x 100% AC power is supplied from the inverter 3 to the load 17, and (1 / 3) x 100% AC power is supplied from the converter 4 to the load 17. However, it is assumed that the battery voltage VB has reached the reference voltage VBR, and the DC power supplied from the bidirectional chopper 2 to the battery 16 is sufficiently small.

[0133] During overload operation in which the load 17 is operated at a power greater than the rated power Pc, the control unit 33 controls the bidirectional chopper 2 so that the DC voltage VD of the DC line DL becomes the reference voltage VDR. Fig. 9 is a circuit block diagram for explaining the operation of the uninterruptible power supply during overload operation.

[0134] 9, AC power supplied from a commercial AC power supply 15 is converted into DC power by a converter 1 and supplied to a DC line DL. In addition, DC power of a battery 16 is supplied to the DC line DL via a bidirectional chopper 2. The DC power supplied to the DC line DL from the converter 1 and the bidirectional chopper 2 is converted into AC power by an inverter 3 and a converter 4 and supplied to a load 17.

[0135] Assuming that 150% of the rated power Pc is supplied to the load 17, as shown in FIG. 9, 100% of the AC power is supplied from the commercial AC power source 15 to the converter 1, 50% of the DC power is supplied from the battery 16 to the bidirectional chopper 2, 100% of the AC power is supplied from the inverter 3 to the load 17, and 50% of the AC power is supplied from the converter 4 to the load 17.

[0136] When a power outage occurs in the commercial AC power supply 15 during normal operation or overload operation, the control unit 31 turns off the switch S1, and the control unit 32 stops the operation of the converter 1. The control unit 35 turns off the switch S5 and stops the operation of the converter 4. In addition, the control unit 33 controls the bidirectional chopper 2 so that the DC voltage VD of the DC line DL becomes the reference voltage VDR.

[0137] 10 is a circuit block diagram for explaining the operation of an uninterruptible power supply device during a power outage of a commercial AC power supply 15. In FIG. 10, DC power of a battery 16 is supplied to a DC line DL via a bidirectional chopper 2. The DC power supplied from the bidirectional chopper 2 to the DC line DL is converted into AC power by an inverter 3 and supplied to a load 17.

[0138] If the rated power Pc of the load 17 is 100%, then 100% of the DC power is supplied from the battery 16 to the inverter 3 via the bidirectional chopper 2, and 100% of the AC power is supplied from the inverter 3 to the load 17, as shown in Fig. 10. Therefore, even if a power outage occurs in the commercial AC power supply 15, the rated power Pc can be supplied to the load 17 for the period during which the DC power is stored in the battery 16.

[0139] As described above, in this embodiment, a bidirectional converter 14 is provided that operates in cooperation with the AC / DC converter 11 during high-speed charging to convert AC power supplied from the commercial AC power source 15 into DC power and supply it to the DC line DL. This makes it possible to prevent a shortage of DC power during high-speed charging, and allows high-speed charging of the battery 16 while operating the load 17. Furthermore, costs can be reduced compared to using a large-capacity uninterruptible power supply or adding an external charger.

[0140] During overload operation, the bidirectional converter 14 operates in cooperation with the DC / AC converter 13 to convert the DC power received from the DC line DL into AC power and supply it to the load 17. Therefore, during the period in which the DC power is stored in the battery 16, it is possible to supply power larger than the rated power Pc to the load 17.

[0141] Fig. 11 is a circuit block diagram showing a first comparative example of the embodiment, and is to be compared with Fig. 7. Referring to Fig. 11, the first comparative example differs from the embodiment in that the converter 4 and the switches S4 and S5 are removed. That is, the first comparative example is a conventional uninterruptible power supply.

[0142] In Comparative Example 1, the capacity of the converter 1, the capacity of the bidirectional chopper 2, the capacity of the inverter 3, and the rated capacity Pc of the load 17 are set to the same value. The rated capacity Pc of the load 17 is set to 100%. During fast charging operation, 100% AC power is supplied from the commercial AC power source 15 to the converter 1, 100% DC power is generated by the converter 1, 50% DC power is supplied from the bidirectional chopper 2 to the battery 16, and 50% AC power is supplied from the inverter 3 to the load 17.

[0143] Therefore, during high-speed charging, only 50% of the rated power Pc of AC power can be supplied to the load 17, and the load 17 cannot be operated normally. Therefore, in this comparative example 1, the battery 16 cannot be charged at high speed while the load 17 is being operated.

[0144] Fig. 12 is a circuit block diagram showing another comparative example 2 of the embodiment, and is a diagram to be compared with Fig. 11. Referring to Fig. 12, the comparative example 2 is different from the comparative example 1 in that the converter 1, the bidirectional chopper 2, and the inverter 3 are replaced with the converter 1A, the bidirectional chopper 2A, and the inverter 3A, respectively. The capacities of the converter 1A, the bidirectional chopper 2A, and the inverter 3A are set to 1.5 times the capacities of the converter 1, the bidirectional chopper 2, and the inverter 3, respectively.

[0145] During fast charging operation, 150% AC power is supplied from the commercial AC power source 15 to the converter 1A, 150% DC power is generated by the converter 1A, 50% DC power is supplied from the bidirectional chopper 2A to the battery 16, and 100% AC power is supplied from the inverter 3A to the load 17.

[0146] Therefore, during high-speed charging operation, 100% AC power, which is the rated power Pc, can be supplied to the load 17, and the battery 16 can be high-speed charged while operating the load 17. However, in this comparative example 2, there is a problem that the device becomes large in size and costs become high because of the extra capacity.

[0147] Fig. 13 is a circuit block diagram showing still another comparative example 2 of the embodiment, which is to be compared with Fig. 11. Referring to Fig. 13, the comparative example 3 differs from the comparative example 1 in that an external charger 41 is added. The capacity of the charger 41 is set to 50% of the rated capacity Pc of the load 17.

[0148] During high-speed charging operation, 50% AC power is supplied from commercial AC power supply 15 to charger 41, and 50% DC power is supplied from charger 41 to battery 16. In addition, 100% AC power is supplied from commercial AC power supply 15 to converter 1, 100% DC power is generated by converter 1, and 100% AC power is supplied from inverter 3 to load 17.

[0149] Therefore, the battery 16 can be quickly charged while the load 17 is operating. However, since the charger 41 is externally attached, the cost increases and the maintainability of the system deteriorates. In addition, the charger 41 has no other use than quickly charging the battery 16.

[0150] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The present invention is defined by the claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0151] T1 AC input terminal, T2 battery terminal, T3 AC output terminal T3, S1 to S5 switches, C1 to C4 capacitors, L1 to L4 reactors, CD1 to CD4 current detectors, 1, 1A, 4 converter, DL DC line, 2, 2A bidirectional chopper, 3, 3A inverter, 5 operation unit, 6 control device, 15 commercial AC power supply, 16 battery, 17 load, Q1 to Q6, Q11 to Q16, Q21 to Q26 IGBTs, D1 to D6, D11 to D16, D21 to D26 diodes, 21 to 25 voltage detectors, 26 power failure detectors, 27, 28 comparators, 29 control circuits, 31 to 35 control units, 36 communication lines, 41 chargers.

Claims

1. a first power converter that converts AC power supplied from the AC power supply into DC power and supplies the DC power to a DC line when the AC power supply is normal, and stops operating when the AC power supply is interrupted; a second power converter that converts DC power received from the DC line into AC power and supplies the AC power to a load; a third power converter that stores DC power received from the DC line in a power storage device when the AC power supply is normal, and supplies DC power from the power storage device to the DC line when the AC power supply is in a power outage; a fourth power converter that operates in cooperation with the first power converter in a first case in which high-speed charging of the power storage device is performed, converts AC power supplied from the AC power source into DC power, and supplies the DC power to the DC line; the third power converter supplies DC power of the power storage device to the DC line even when the AC power supply is healthy in a second case in which an overload operation is performed; An uninterruptible power supply device, wherein the fourth power converter operates in cooperation with the second power converter in the second case, converts DC power received from the DC line into AC power and supplies it to the load.

2. The fourth power converter includes: a switching circuit for connecting an AC node to the AC power source in the first case and for connecting the AC node to the load in the second case; and a fifth power converter that, in the first case, converts AC power supplied from the AC power source via the AC node into DC power and supplies it to the DC line, and, in the second case, converts DC power received from the DC line into AC power and supplies it to the load via the AC node.

3. 3. The uninterruptible power supply according to claim 2, wherein the switching circuit electrically disconnects the AC node from the AC power supply and the load when a power failure occurs in the AC power supply.

4. The first, second, and fifth power converters have the same circuit configuration; the first and second power converters have the same capacity; 3. The uninterruptible power supply according to claim 2, wherein a capacity of the fifth power converter is smaller than a capacity of each of the first and second power converters.

5. a ratio between an output of the fifth power converter and an output of the first power converter in the first case is controlled to be a ratio between a capacity of the fifth power converter and a capacity of each of the first power converters; 5. The uninterruptible power supply according to claim 4, wherein a ratio between the output of the fifth power converter and the output of the second power converter in the second case is controlled to be a ratio between a capacity of the fifth power converter and a capacity of each of the second power converters.

6. 2. The uninterruptible power supply of claim 1, wherein the power storage device is a lithium ion battery.

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