JP2020005410A - Uninterruptible power supply system - Google Patents

Abstract

To provide an uninterruptible power supply system having high efficiency and capable of re-boosting an uninterruptible power supply in a standby mode even during a power failure.SOLUTION: In an uninterruptible power supply system, a switch S1 is turned off in an uninterruptible power supply U in a standby mode, so that flowing of a current into an AC input filter 3 from a commercial AC power supply 51 can be prevented and efficiency can be improved. A control power supply 23 of the uninterruptible power supply U in the standby mode can re-boost the uninterruptible power supply U in the standby mode even during a power failure because it generates a DC power supply voltage VDC for a control circuit 14 on the basis of an AC voltage supplied from other uninterruptible power supplies U in an operation mode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an uninterruptible power supply system, and more particularly, to an uninterruptible power supply system including a plurality of uninterruptible power supplies connected in parallel to a load.

  For example, Japanese Unexamined Patent Application Publication No. 2013-31325 (Patent Document 1) discloses an uninterruptible power supply system including a plurality of uninterruptible power supplies connected in parallel to a load. Each uninterruptible power supply includes a converter that converts AC power from an AC power supply into DC power, an inverter that converts DC power into AC power and supplies it to a load, and a current detector that detects an output current of the inverter. And a control circuit for controlling the converter and the inverter. The plurality of control circuits are connected to each other by a communication line.

  Each control circuit determines whether to set the uninterruptible power supply to which it belongs to a standby state or an operation state based on a communication result with another control circuit, and transmits the determination result to another control circuit. When the standby state is set, the operation of the converter and the inverter is stopped. When the operation state is set, the converter and the inverter are operated.

  In general, the efficiency of the uninterruptible power supply is maximized when the load factor is in a certain range (for example, about 30 to 60%), and the efficiency is reduced when the load factor is lower than the range or higher than the range. Tends to decrease. Therefore, in the uninterruptible power supply system, at the time of a low load, the load factor of each uninterruptible power supply in the operating state is set by setting a part of the plurality of uninterruptible power supplies to a standby state. Range can be raised. According to this, it is possible to improve the operation efficiency of the entire system by monitoring the load factor of each uninterruptible power supply device during operation and appropriately selecting the number of operating units according to the change in the load factor.

  Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-294381 (Patent Document 2), in an uninterruptible power supply, an AC input filter is generally provided between an AC power supply and a converter, and an AC input filter is provided between an inverter and a load. Is provided with an AC output filter. Each of the AC input filter and the AC output filter includes a capacitor and a reactor.

JP 2013-31325 A JP-A-9-294381

  When the AC input filter and the AC output filter of Patent Document 2 are provided in each of the uninterruptible power supply devices of Patent Document 1, AC current flows from the AC power supply into the AC input filter of each of the uninterruptible power supply devices. There is a problem that an AC current flows from the power failure power supply device to the AC output filter of the standby UPS and a loss occurs.

  As a countermeasure against this, the standby uninterruptible power supply is electrically disconnected from the AC power supply and the operating uninterruptible power supply, so that the current flows into the AC input filter and AC output filter of the standby uninterruptible power supply. A first method for preventing the loss and reducing the loss is conceivable. However, the first method has a problem that the DC power supply voltage for the control circuit cannot be generated in the uninterruptible power supply in the standby state, and the uninterruptible power supply cannot be restarted.

  As another measure, while maintaining the connection between the AC power supply and each uninterruptible power supply, the standby uninterruptible power supply is electrically disconnected from the operating uninterruptible power supply, so that the standby uninterruptible power supply is disconnected. A second method for preventing the current from flowing into the AC output filter of the power failure power supply device and reducing loss is conceivable. However, according to the second method, it is not possible to generate a DC power supply voltage for a control circuit during a power outage when the supply of AC power from the AC power supply is stopped, and it is not possible to restart the uninterruptible power supply. There's a problem.

  Therefore, a main object of the present invention is to provide an uninterruptible power supply system with high efficiency and capable of restarting an uninterruptible power supply in a standby state even during a power outage.

  An uninterruptible power supply system according to the present invention is an uninterruptible power supply system including a plurality of uninterruptible power supplies connected in parallel to a load. Each uninterruptible power supply device includes an input terminal receiving AC power supplied from an AC power supply, an output terminal connected to a load, a first switch connected in series between the input terminal and the output terminal, an AC input filter, It includes a converter, an inverter, and an AC output filter, a current detector that detects a current flowing from the inverter to a load, and a control circuit that controls a corresponding uninterruptible power supply.

  The AC input filter allows the AC power from the AC power supply to pass through the converter and blocks a switching frequency signal generated by the converter. The converter converts AC power that has passed through the AC input filter into DC power. The inverter converts the DC power generated by the converter into AC power during normal times when AC power is supplied from the AC power supply, and operates during a power outage when the AC power supply from the AC power supply is stopped. Is converted to AC power. The AC output filter allows the AC power generated by the inverter to pass through the load and blocks a switching frequency signal generated by the inverter. From the viewpoint of the control circuit, the uninterruptible power supply to which the control circuit belongs is its own device, each other uninterruptible power supply is another device, and the control circuit of each uninterruptible power supply controls each other device through a communication line. It is coupled to the circuit and each other.

  The control circuit of each uninterruptible power supply unit controls the control power supply that generates a DC power supply voltage for driving the control circuit based on the AC voltage appearing at the output terminal, and the detection result of the current detector of the own device and the communication line. A calculation unit for obtaining a load current from the sum of the detection results of the current detectors of the other devices obtained via the other devices and obtaining an appropriate number of uninterruptible power supply units required to supply the load current; and a calculation unit The proper number of vehicles determined by the above is compared with the current number of vehicles, and based on the comparison result, it is determined whether the own device is to be in a standby state or an operation state, and the determination result is transmitted via a communication line. The signal is transmitted to a control circuit of another device, and when the standby state is set, the first switch is turned off, and the operation of the converter and the inverter is stopped. When the operation state is set, the first switch is turned on. Together and a command unit for operating the converter and the inverter.

  In the uninterruptible power supply system according to the present invention, in the uninterruptible power supply in the standby state, the first switch is turned off to electrically disconnect the AC input filter from the AC power supply, so that the current from the AC power supply to the AC input filter can be reduced. Inflow can be prevented, and efficiency can be improved. In the uninterruptible power supply in the standby state, the DC power supply voltage for the control circuit is generated based on the AC voltage supplied to the output terminal from each other uninterruptible power supply in the operating state. Can be restarted.

FIG. 1 is a circuit block diagram illustrating a configuration of an uninterruptible power supply system according to Embodiment 1 of the present invention. FIG. 2 is a block diagram illustrating a configuration of a control circuit illustrated in FIG. 1. 3 is a flowchart showing the operation of the control circuit shown in FIG. FIG. 9 is a block diagram illustrating a configuration of a control circuit of an uninterruptible power supply device included in the uninterruptible power supply system according to Embodiment 2 of the present invention. 5 is a flowchart showing the operation of the control circuit shown in FIG. FIG. 13 is a block diagram showing a configuration of a control circuit of an uninterruptible power supply device included in the uninterruptible power supply system according to Embodiment 3 of the present invention. 7 is a flowchart showing the operation of the control circuit shown in FIG.

[Embodiment 1]
FIG. 1 is a circuit block diagram showing a configuration of an uninterruptible power supply system according to Embodiment 1 of the present invention. 1, this uninterruptible power supply system includes a plurality (three in the figure) of uninterruptible power supplies U1 to U3 and a plurality of batteries B1 to B3.

  Each of the uninterruptible power supply devices U1 to U3 includes an input terminal T1, a battery terminal T2, and an output terminal T3. Input terminal T1 receives commercial frequency AC power from commercial AC power supply 51. Battery terminals T2 of the uninterruptible power supply devices U1 to U3 are connected to batteries (power storage devices) B1 to B3, respectively. Each of batteries B1 to B3 stores DC power. A capacitor may be connected instead of the battery B.

  The output terminal T3 is connected to the load 52. The load 52 is driven by AC power. The uninterruptible power supplies U1 to U3 are connected in parallel to the load 52. Of the uninterruptible power supply units U1 to U3, only the appropriate number (for example, two) of uninterruptible power supply units (for example, U1 and U2) required for the operation of the load 52 are set to the operation state, and the remaining uninterruptible power supply units (for example, U1 and U2) In this case, U3) is in a standby state.

  Each of the uninterruptible power supply devices U1 to U3 further includes switches S1 to S3, capacitors 1, 5, 10, reactors 2, 9, converter 4, DC line 6, bidirectional chopper 7, inverter 8, current detector 12, An operation unit 13 and a control circuit 14 are provided.

  Switch S1 and reactor 2 are connected in series between input terminal T1 and the input node of converter 4. Capacitor 1 is connected to node N1 between switch S1 and reactor 2. The switch S1 is turned on when the corresponding uninterruptible power supply U is set to the operation state, and is turned off when the corresponding uninterruptible power supply U is set to the standby state. The instantaneous value of the AC input voltage VI appearing at the node N1 is detected by the control circuit 14. Based on the instantaneous value of the AC input voltage VI, whether or not a power failure has occurred is determined.

  The capacitor 1 and the reactor 2 constitute an AC input filter 3. The AC input filter 3 is a low-pass filter that passes AC power of a commercial frequency from the commercial AC power supply 51 to the converter 4 and prevents a signal of a switching frequency generated in the converter 4 from passing through the commercial AC power supply 51. I do.

  Converter 4 is controlled by control circuit 14, and converts AC power to DC power and outputs the DC power to DC line 6 during normal times when AC power is supplied from commercial AC power supply 51. During a power outage when the supply of AC power from commercial AC power supply 51 is stopped, the operation of converter 4 is stopped. The output voltage of the converter 4 can be controlled to a desired value.

  The capacitor 5 is connected to the DC line 6 and smoothes the voltage of the DC line 6. The instantaneous value of the DC voltage VD appearing on the DC line 6 is detected by the control circuit 14. The DC line 6 is connected to the high voltage side node of the bidirectional chopper 7, and the low voltage side node of the bidirectional chopper 7 is connected to the battery terminal T2 via the switch S2.

  The switch S2 is turned on when the corresponding uninterruptible power supply U is used, and turned off during maintenance of the corresponding uninterruptible power supply U and the corresponding battery B. The instantaneous value of the inter-terminal voltage VB of the battery B appearing at the battery terminal T2 is detected by the control circuit 14.

  The bidirectional chopper 7 is controlled by the control circuit 14, stores the DC power generated by the converter 4 in the battery B during normal operation when AC power is supplied from the commercial AC power supply 51, and outputs the AC power from the commercial AC power supply 51. When the power supply is stopped, the DC power of battery B is supplied to inverter 8 via DC line 6.

  When storing the DC power in the battery B, the bidirectional chopper 7 reduces the DC voltage VD of the DC line 6 and supplies the reduced voltage to the battery B. When supplying the DC power of the battery B to the inverter 8, the bidirectional chopper 7 boosts the inter-terminal voltage VB of the battery B and outputs it to the DC line 6. DC line 6 is connected to an input node of inverter 8.

  The inverter 8 is controlled by the control circuit 14, converts DC power supplied from the converter 4 or the bidirectional chopper 7 via the DC line 6 into AC power of a commercial frequency, and outputs the AC power. That is, the inverter 8 converts the DC power supplied from the converter 4 via the DC line 6 into AC power during normal times, and converts the DC power supplied from the battery B via the bidirectional chopper 7 into AC power during a power failure. Convert to electric power. The output voltage of the inverter 8 can be controlled to a desired value.

  The output node of inverter 8 is connected to one terminal of reactor 9, and the other terminal (node N2) of reactor 9 is connected to output terminal T3 via switch S3. Capacitor 10 is connected to node N2. The instantaneous value of the AC output voltage VO appearing at the node N2 is detected by the control circuit 14. The current detector 12 detects an instantaneous value of the current IO flowing from the node N2 to the output terminal T3 (that is, the load 52) via the switch S3, and supplies a signal IOf indicating the detected value to the control circuit 14.

  Reactor 9 and capacitor 10 constitute AC output filter 11. The AC output filter 11 is a low-pass filter that allows the AC power of the commercial frequency generated by the inverter 8 to pass through the output terminal T3 and the switching frequency signal generated by the inverter 8 to pass through the output terminal T3. To prevent. The switch S3 is controlled by the control circuit 14, and is turned on when the corresponding uninterruptible power supply U is used, and turned off when the corresponding uninterruptible power supply U is maintained.

  The operation unit 13 includes a plurality of buttons operated by the user of the corresponding uninterruptible power supply U, an image display unit that displays various information, and the like. The user of the system can operate the uninterruptible power supply U manually or automatically by operating the operation unit 13. In addition, the user of the system operates the operation unit 13 to cause the uninterruptible power supply devices U1 to U3 to be in a standby state when the appropriate number of drives required for driving the load 52 is larger than the current number of drives. Priorities can be set.

  The control circuit 14 controls the entire corresponding uninterruptible power supply U based on a signal from the operation unit 13, the AC input voltage VI, the DC voltage VD, the battery voltage VB, the AC output current IO, the AC output voltage VO, and the like. I do. That is, control circuit 14 detects whether a power failure has occurred based on the detected value of AC input voltage VI, and controls converter 4 and inverter 8 in synchronization with the phase of AC input voltage VI.

  Control circuit 14 controls converter 4 so that DC voltage VD becomes a desired target voltage VDT in a normal state when AC power is supplied from commercial AC power supply 51, and controls AC power from commercial AC power supply 51. At the time of a power outage where the supply is stopped, the operation of converter 4 is stopped.

  Further, the control circuit 14 controls the bidirectional chopper 7 so that the battery voltage VB becomes the desired target battery voltage VBT in the normal state, and controls the DC voltage VD to the desired target voltage VDT in the event of a power failure. The direction chopper 7 is controlled.

  Further, the control circuit 14 is connected to the control circuit 14 of each of the other uninterruptible power supplies U by a communication cable 15 and exchanges information with each of the other uninterruptible power supplies U via the communication cable 15. The control circuit 14 controls the converter 4 and the inverter 8 such that the shared currents of the plurality of uninterruptible power supply devices U1 to U3 are equal.

  Further, the control circuit 14 obtains the sum of the output currents IO of the plurality of uninterruptible power supplies U1 to U3, that is, the load current IL, based on the output signals IOf of the plurality of current detectors 12, and calculates the load current IL. The appropriate number of uninterruptible power supply units U required for supply is determined. Further, the control circuit 14 compares the obtained proper number of operating units with the current number of operating units and, based on the comparison result and the priority order of standby, sets the corresponding uninterruptible power supply U to the standby state or to the operating state. Is determined.

  When the corresponding uninterruptible power supply device U is set to the standby state, the control circuit 14 turns off the corresponding switch S1 to prevent the current from flowing from the commercial AC power supply 51 to the corresponding AC input filter 3, and The operation of converter 4, bidirectional chopper 7, and inverter 8 is stopped. When causing the corresponding uninterruptible power supply U to be in the operating state, the control circuit 14 keeps the corresponding switch S1 in the ON state and continues the operation of the corresponding converter 4, bidirectional chopper 7, and inverter 8 Let it.

  FIG. 2 is a block diagram showing a configuration of the control circuit 14. 2, the control circuit 14 includes communication terminals T4 and T5, voltage detectors 21 and 22, a control power supply 23, a calculation unit 24, a command unit 25, and a storage unit 26.

  The communication terminal T <b> 4 is connected to the calculation unit 24 and the command unit 25, and also connected to the calculation unit 24 and the command unit 25 of another uninterruptible power supply U via the communication cable 15. The communication terminal T5 is connected to the calculation unit 24 and the command unit 25, and is further connected to the calculation unit 24 and the command unit 25 of another uninterruptible power supply U via the communication cable 15.

  Voltage detector 21 detects AC voltage VI at node N1 (FIG. 1), and supplies a signal indicating the detected value to command unit 25. Voltage detector 22 detects AC voltage VO at node N2 (FIG. 1), and supplies a signal indicating the detected value to arithmetic unit 24. The control power supply 23 generates a DC power supply voltage VDC for driving the entire control circuit 14 based on the AC voltage VO.

  The calculation unit 24 transmits the detection results of the voltage detector 22 and the current detector 12 (FIG. 1) to the calculation units 24 of the other two uninterruptible power supplies U via the communication terminals T4 and T5, The detection results of the voltage detector 22 and the current detector 12 of the two uninterruptible power supplies U are received via the communication terminals T4 and T5.

  The arithmetic unit 24 also controls the command unit based on the detection results of the voltage detectors 22 and the current detectors 12 of the uninterruptible power supplies U1 to U3 so that the shared currents of the plurality of uninterruptible power supplies U1 to U3 are equal. 25 controls the converter 4 and the inverter 8.

  In addition, the arithmetic unit 24 obtains the sum of the output currents IO of the plurality of uninterruptible power supplies U1 to U3, that is, the load current IL supplied to the load 52 from the uninterruptible power supplies U1 to U3, and calculates the load current IL. An appropriate number of uninterruptible power supply units U required for supply is obtained, and the obtained appropriate number of operation units is provided to the command unit 25.

  The priority order in which the uninterruptible power supply devices U1 to U3 enter a standby state is stored in the storage unit 26. The priorities are set, for example, in the numerical order of the uninterruptible power supply U. In this case, the priorities of the uninterruptible power supply devices U1 to U3 are first, second, and third, respectively.

  Command unit 25 determines whether or not AC power is supplied from commercial AC power supply 51 based on a signal from voltage detector 21. The command unit 25 controls the converter 4, the bidirectional chopper 7, and the inverter 8 to generate AC power in the normal state, and stops the operation of the converter 4 and controls the bidirectional chopper 7 and the inverter 8 in the case of a power outage. Control to generate AC power. Further, the command unit 25 controls the switches S1 to S3.

  Further, the command unit 25 compares the appropriate number of vehicles operated by the arithmetic unit 24 with the current number of vehicles operated, and sets the corresponding uninterruptible power supply U in the standby state based on the comparison result and the priority of standby. It is determined whether the vehicle is to be operated or the vehicle is in the operating state.

  For example, when the appropriate number of operating vehicles is two and the current number of operating vehicles is three, the command unit 25 determines that the number of operating vehicles should be reduced. Further, the command unit 25 determines whether the corresponding uninterruptible power supply U is to be in the standby state or the operating state based on the priority order of the corresponding uninterruptible power supply U. Then, the command unit 25 turns off the corresponding switch S1 when the standby state is set, and stops the corresponding converter 4, the bidirectional chopper 7, and the inverter 8 and sets the corresponding switch S1 on state when the operation state is set. And the operation of the corresponding converter 4, bidirectional chopper 7, and inverter 8 is continued.

  For example, the command unit 25 of the uninterruptible power supply U1 should place the corresponding uninterruptible power supply U1 in a standby state because the priority of the corresponding uninterruptible power supply U1 (own apparatus) is the first. Is determined, the corresponding switch S1 is turned off, and the corresponding converter 4, bidirectional chopper 7, and inverter 8 are stopped. When the corresponding switch S1 is turned off and the corresponding converter 4, bidirectional chopper 7, and inverter 8 are stopped, the command unit 25 informs other uninterruptible power supply (other devices) U2 The command is sent to the command unit 25 of U3.

  Since the command units 25 of the uninterruptible power supplies U2 and U3 have the second and third priorities of the corresponding uninterruptible power supplies (U2 and U3 in this case), respectively, It is determined that the device U should be brought into the operating state, the corresponding switch S1 is kept on, and the operation of the corresponding converter 4, bidirectional chopper 7, and inverter 8 is continued.

  Conversely, when the number of properly operated vehicles is three and the number of currently operated vehicles is two, the command unit 25 determines that the number of operated vehicles should be increased. When the corresponding uninterruptible power supply U is in the standby state, the command unit 25 causes the corresponding uninterruptible power supply U to be in the operating state.

  For example, the command unit 25 of the uninterruptible power supply U1 determines that the corresponding uninterruptible power supply U1 should be put into the operating state because the corresponding uninterruptible power supply U1 is in the standby state, and the corresponding switch S1 Is turned on, and the corresponding converter 4, bidirectional chopper 7, and inverter 8 are operated. When the corresponding switch S1 is turned on and the corresponding converter 4, bidirectional chopper 7, and inverter 8 are operated, the command unit 25 notifies the command units of the other uninterruptible power supplies U2, U3. Tell 25.

  Operation unit 13 includes, for example, operation buttons. The user of the system can operate the uninterruptible power supply U manually or automatically by operating the operation unit 13. By operating the operation unit 13, the user of the system can write the number of the uninterruptible power supply U, the priority order in which the uninterruptible power supplies U <b> 1 to U <b> 3 enter the standby state, and the like in the storage unit 26. .

  When the priority order is written to the storage unit 26 using the operation unit 13 of one uninterruptible power supply U, the priority order is written to the storage units 26 of all the uninterruptible power supply units U1 to U3 by the command unit 25. . In addition, the number of the uninterruptible power supply U may be automatically set according to the position, the order, and the like where the uninterruptible power supply U is installed.

  Even when the corresponding uninterruptible power supply U is in a standby state and the switch S1 is turned off, the control power supply 23 receives a signal from another uninterruptible power supply U via the corresponding switch S3 and the node N2 (FIG. 1). A DC power supply voltage VDC for the control circuit is generated based on the supplied AC power. Therefore, control circuit 14 continues to be driven by DC power supply voltage VDC from control power supply 23 even when uninterruptible power supply U is in a standby state.

  FIG. 3 is a flowchart showing the operation of the control circuit 14 shown in FIG. The case where the control circuit 14 is included in the uninterruptible power supply U1 will be described. As viewed from the control circuit 14, the uninterruptible power supply U1 to which the control circuit 14 belongs is its own device, and each of the other uninterruptible power supplies U2 and U3 is another device.

  In step ST1 of FIG. 3, the command unit 25 of the uninterruptible power supply U1 turns on the corresponding switch S1 to operate the corresponding converter 4, bidirectional chopper 7, and inverter 8. In step ST2, the current detector 12 detects the output current IO of the own device U1. The detected value of the output current IO of the own device U1 is given to the calculation units 24 of the other uninterruptible power supply devices (other devices) U2 and U3. Conversely, the detected values of the output currents IO of the other uninterruptible power supplies U2 and U3 are provided to the calculation unit 24 of the uninterruptible power supply U1.

  In step ST3, the calculation unit 24 adds the detected values of the output currents IO of the uninterruptible power supply devices U1 to U3, and detects the load current IL supplied to the load 52 from the uninterruptible power supply devices U1 to U3. In step ST4, the calculation unit 24 obtains an appropriate number of uninterruptible power supply units U required to operate the load 52 based on the load current IL obtained in step ST3. For example, when the rated current of the uninterruptible power supply U is Ir and the load current IL is 1.5 times Ir, the proper number of uninterruptible power supplies U is two.

  In step ST5, the command unit 25 compares the appropriate number of operating vehicles obtained in step ST4 with the current number of operating vehicles, and based on the comparison result, maintains the uninterruptible power supply U while ensuring redundancy (parallel redundant operation). It is determined whether to increase, decrease, or maintain the number of vehicles operated. If it is determined in step ST5 that the number of operating vehicles is to be increased, another uninterruptible power supply U in standby is activated in step ST6.

  For example, when uninterruptible power supply units U1 and U2 are in the operating state and uninterruptible power supply unit U3 is in the standby state, if it is determined in step ST5 that the number of operating units is to be increased, the uninterruptible power supply unit in the standby state U3 is activated. When activating the uninterruptible power supply U3 in the standby state, even if the supply of AC power from the commercial AC power supply 51 is stopped, the switch of the uninterruptible power supply U3 from the uninterruptible power supply U1 or U2. The AC voltage VO is supplied to the control power supply 23 via S3, and the control circuit 14 is driven by the control power supply 23, so that the uninterruptible power supply U3 is started.

  If it is determined in step ST5 that the number of operating vehicles is to be reduced, in step ST7, the command unit 25 determines whether to stop the own device or continue operating the own device based on the priority stored in the storage unit 26. Determine. If it is determined in step ST7 that the own device is to be stopped, the switch S1 of the own device is turned off in step ST8, and the converter 4, the bidirectional chopper 7, and the inverter 8 are stopped.

  When the device itself is stopped, the switch S1 is turned off, and the commercial AC power supply 51 and the AC input filter 3 are electrically disconnected. Therefore, it is possible to prevent loss from occurring in the AC input filter 3, thereby improving efficiency. Can be achieved. If it is determined in step ST7 that the operation of the own device is continued, the process returns to step ST1.

  As described above, in the first embodiment, in the uninterruptible power supply U in the standby state, the switch S1 is turned off to electrically disconnect the AC input filter 3 from the commercial AC power supply 51. The current can be prevented from flowing into the filter 3, and the efficiency can be improved. Further, the uninterruptible power supply U in the standby state generates the DC power supply voltage VDC for the control circuit 14 based on the AC voltage VO supplied from each of the other uninterruptible power supply U in the operating state to the output terminal T3. Even in the event of a power failure, the uninterruptible power supply U in the standby state can be restarted.

  In the first embodiment, a case has been described in which the present invention is applied to an uninterruptible power supply system including three uninterruptible power supply devices U1 to U3. Needless to say, the present invention can be applied to an uninterruptible power supply system including more than one uninterruptible power supply U.

  Further, in the first embodiment, the switch S1 is turned off and the switches S2 and S3 are turned off in the uninterruptible power supply U in the standby state, but the switches S1 and S2 are turned off in the uninterruptible power supply U in the standby state. , The switch S3 may be turned on. In this case, the DC power discharged from battery B in the standby state can be reduced.

  When the switch S3 is turned off in the uninterruptible power supply U in the standby state, it is possible to prevent the current from flowing into the AC output filter 11 from another uninterruptible power supply U in the operating state, and to improve the efficiency. be able to. However, in this case, since the control power supply 23 (FIG. 2) cannot generate the DC power supply voltage VDC, the uninterruptible power supply U in the standby state cannot be started.

[Embodiment 2]
FIG. 4 is a block diagram showing a configuration of control circuit 14A of uninterruptible power supply U included in the uninterruptible power supply system according to Embodiment 2 of the present invention, and is a diagram to be compared with FIG. Referring to FIG. 4, control circuit 14A differs from control circuit 14 of FIG. 2 in that timer 27 is added.

  The timer 27 measures the time during which the corresponding uninterruptible power supply U is in a standby state, and outputs a start signal in response to the measured time reaching a predetermined time. The command unit 25 turns off the corresponding switch S1, stops the converter 4, the bidirectional chopper 7, and the inverter 8, and then turns on the corresponding switch S1 in response to the start signal, thereby turning on the converter 4, the bidirectional chopper. 7 and the inverter 8 are started.

  In addition, in response to the start signal from the timer 27, the command unit 25 updates the priority stored in the storage unit 26, makes the priority of the corresponding uninterruptible power supply U the lowest, and sets the other two The priority order of the uninterruptible power supply U is moved up one by one.

  For example, the command unit 25 of the uninterruptible power supply U1 updates the priority stored in the storage unit 26 in response to the start signal from the timer 27, and changes the priority of the corresponding uninterruptible power supply U1 to the lowest. And the priority order of the other uninterruptible power supply devices U2 and U3 is moved up one by one. In other words, the priorities in which the uninterruptible power supply devices U1 to U3 are placed in the standby state are updated to the third, first, and second places, respectively.

  When the number of operating units is reduced by one in this state, the uninterruptible power supply U2 is set to a standby state, the uninterruptible power supply U2 is set to an operating state after a predetermined time has elapsed, and the uninterruptible power supply units U1 to U3 are set to a standby state. The priority is updated to the second, third, and first places, respectively.

  When the number of operating units is reduced by one in this state, the uninterruptible power supply U3 is set to a standby state, the uninterruptible power supply U3 is set to an operating state after a predetermined time has elapsed, and the uninterruptible power supply units U1 to U3 are set to a standby state. The priorities are updated to first, second, and third, respectively. That is, when only one unit is in the standby state, the uninterruptible power supply units U1 to U3 are sequentially set in the standby state one by one, and the uninterruptible power supply unit U to be in the standby state is automatically rotated.

  The user of the system can set or cancel the automatic rotation of the uninterruptible power supply U by operating the operation unit 13. When the automatic rotation is canceled, the uninterruptible power supply system becomes the same as the uninterruptible power supply system of the first embodiment.

  FIG. 5 is a flowchart showing the operation of the control circuit 14A shown in FIG. 4, and is a diagram to be compared with FIG. The flowchart of FIG. 5 is obtained by replacing step ST8 of the flowchart of FIG. 3 with steps ST10 to ST14. Steps ST1 to ST7 are as described in FIG. FIG. 5 also describes a case where control circuit 14A is included in uninterruptible power supply U1. As viewed from the control circuit 14A, the uninterruptible power supply U1 to which the control circuit 14A belongs is its own device, and each of the other uninterruptible power supplies U2 and U3 is another device.

  If it is determined in step ST7 that the own device U1 is to be stopped, in step ST10, the command unit 25 determines whether or not the automatic rotation is set by the operation unit 13. When the automatic rotation is not set, the command unit 25 turns off the switch S1 of the own device U1 and stops the converter 4, the bidirectional chopper 7, and the inverter 8 in step ST11.

  When the automatic rotation is set, in step ST12, the command unit 25 turns off the switch S1 of the own device U1, stops the converter 4, the bidirectional chopper 7, and the inverter 8, and starts the timer 27. In step ST13, the timer 27 outputs a start signal after a lapse of a predetermined time from the start, and the command section 25 turns on the switch S1 of the own device U1 in response to the start signal, and the converter 4, the bidirectional chopper 7, and the inverter. 8 is started. In step ST14, the command unit 25 updates the priority stored in the storage unit 26 of each uninterruptible power supply U, and returns to step ST2.

  In the second embodiment, for example, when one uninterruptible power supply U is set to the standby state, the uninterruptible power supplies U1 to U3 are sequentially set to the standby state one by one. Therefore, since the operation time of the uninterruptible power supply devices U1 to U3 can be equalized, the occurrence of failure of each uninterruptible power supply device U can be delayed.

[Embodiment 3]
FIG. 6 is a block diagram showing the configuration of control device 14B of uninterruptible power supply U included in the uninterruptible power supply system according to Embodiment 3 of the present invention, and is a diagram to be compared with FIG. Referring to FIG. 6, control device 14B differs from control device 14A of FIG. 4 in that a failure detector 28 is added.

  The failure detector 28 detects the presence or absence of a failure in the corresponding uninterruptible power supply U, and outputs a failure detection signal when the corresponding uninterruptible power supply U has failed. When a failure detection signal is output from the corresponding failure detector 28, the command unit 25 turns off the switches S1 and S3 to disconnect the corresponding uninterruptible power supply unit U from the parallel operation or the corresponding uninterruptible power supply. The power supply U is set to the standby state.

  Further, the command unit 25 removes the corresponding uninterruptible power supply U from the priority order and raises the priority of the other uninterruptible power supply U by one in the standby state. For example, when the uninterruptible power supply units U1 to U3 are first to third in priority and the uninterruptible power supply unit U1 fails, the uninterruptible power supply unit U1 is excluded from the priority order, and The priorities of the devices U2 and U3 are made first and second, respectively.

  FIG. 7 is a flowchart showing the operation of the control circuit 14B shown in FIG. 6, and is a diagram to be compared with FIG. The flowchart of FIG. 7 is obtained by adding steps ST1A to ST1C to the flowchart of FIG. Step ST1A is performed between steps ST1 and ST2. FIG. 7 also illustrates a case where the control circuit 14B is included in the uninterruptible power supply U1. As viewed from the control circuit 14B, the uninterruptible power supply U1 to which the control circuit 14B belongs is its own device, and each of the other uninterruptible power supplies U2 and U3 is another device.

  In step ST1A, the failure detector 28 detects whether the corresponding uninterruptible power supply U1 (that is, the own device U1) has failed, and if not, proceeds to step ST2. If the own device U1 has failed, the command unit 25 turns off the switches S1 and S3 in step ST1B to disconnect the own device U1 from parallel operation, or puts the own device U1 in a standby state, and in step ST1C The command unit 25 updates the priority by excluding the device U1 from the priority.

  In the third embodiment, the same effects as those of the first and second embodiments can be obtained, and the failed uninterruptible power supply U can be excluded from the rotation.

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

  U1 to U3 uninterruptible power supply, B1 to B3 battery, T1 input terminal, T2 battery terminal, T3 output terminal, S1 to S3 switch, 1,5,10 capacitor, 2,9 reactor, 3 AC input filter, 4 converter, 6 DC line, 7 bidirectional chopper, 8 inverter, 11 AC output filter, 12 current detector, 13 operation unit, 14, 14A, 14B control circuit, T4, T5 communication terminal, 21, 22, voltage detector, 23 control power supply , 24 operation unit, 25 command unit, 26 storage unit, 27 timer, 28 failure detector, 51 commercial AC power supply, 52 load.

Claims (5)

An uninterruptible power supply system including a plurality of uninterruptible power supplies connected in parallel to a load,
Each uninterruptible power supply
An input terminal for receiving AC power supplied from an AC power supply,
An output terminal connected to the load,
A first switch, an AC input filter, a converter, an inverter, and an AC output filter connected in series between the input terminal and the output terminal;
A current detector for detecting a current flowing from the inverter to the load;
A control circuit for controlling a corresponding uninterruptible power supply,
The AC input filter allows the AC power from the AC power supply to pass through the converter, and blocks a switching frequency signal generated by the converter.
The converter converts AC power that has passed through the AC input filter into DC power,
The inverter converts the DC power generated by the converter into AC power during a normal time when AC power is supplied from the AC power supply, and during a power outage when the supply of AC power from the AC power supply is stopped. Converts the DC power of the power storage device into AC power,
The AC output filter allows the AC power generated by the inverter to pass through the load, and blocks a switching frequency signal generated by the inverter,
The uninterruptible power supply to which the control circuit belongs as viewed from the control circuit is its own device, and each other uninterruptible power supply is another device,
The control circuit of each uninterruptible power supply is coupled to the control circuit of each other device by a communication line,
The control circuit of each uninterruptible power supply,
A control power supply that generates a DC power supply voltage for driving the control circuit based on an AC voltage appearing at the output terminal;
It is necessary to obtain a load current from the sum of the detection result of the current detector of the own device and the detection result of the current detector of each other device obtained through the communication line, and supply the load current. A calculation unit for determining the appropriate number of operating uninterruptible power supply units,
Comparing the proper operating number obtained by the arithmetic unit with the current operating number, and determining whether to make the own device in the standby state or the operating state based on the comparison result, and transmitting the determined result to the communication When transmitting to the control circuit of each other device via a line and setting the standby state, the first switch is turned off and the converter and the inverter are stopped and the operation state is set. And a command unit for turning on the first switch and operating the converter and the inverter. Each uninterruptible power supply
Further, a DC line connected between the converter and the inverter,
A bidirectional chopper and a second switch connected in series between the DC line and the power storage device;
The bidirectional chopper stores the DC power generated by the converter in the power storage device in the normal state, and supplies the DC power from the power storage device to the inverter during the power outage,
The command unit further turns off the second switch when the standby state is set and stops the operation of the bidirectional chopper, and turns on the second switch when the operation state is set. The uninterruptible power supply system according to claim 1, wherein the uninterruptible power supply system operates the bidirectional chopper together. The control circuit of each uninterruptible power supply further includes a storage unit that stores a priority order in which the plurality of uninterruptible power supplies enter the standby state,
The command unit compares the appropriate number of operating units obtained by the arithmetic unit with the current number of operating units, and based on the comparison result and the priority stored in the storage unit, sets the own device in the standby mode. The uninterruptible power supply system according to claim 1, wherein it is determined whether the state is set to the operating state or the operating state. The control circuit of each uninterruptible power supply further measures the time during which the own device is stopped in the standby state by the command unit, and when the measured time reaches a predetermined time, a start signal. Including a timer that outputs
The command unit sets the own device to the operation state in response to the start signal being output from the timer of the own device, and sets the priority of the own device to the standby state to the lowest priority, Raise the priority of each other device by one via the communication line,
The uninterruptible power supply system according to claim 3, wherein the storage unit of each uninterruptible power supply device stores the priority changed by the command unit. The control circuit of each uninterruptible power supply further includes a failure detector that detects the presence or absence of a failure of the uninterruptible power supply,
The command unit, when the failure of the own device is detected by the failure detector of the own device, disconnects the own device from parallel operation, or puts the own device in the standby state, the own device Is excluded from the priorities, and each other device is shifted up by one in the standby state via the communication line,
The uninterruptible power supply system according to claim 3 or 4, wherein the storage unit of each uninterruptible power supply stores the priority changed by the command unit.