Uninterruptible power supply device

Abstract

This uninterruptible power supply device has a normal mode in which power supplied from an AC power supply is supplied to a load, a backup mode in which the power stored in a storage battery is supplied to the load during a power failure of the AC power supply, and a deterioration diagnosis mode in which the deterioration state of the storage battery is diagnosed. The control device of the uninterruptible power supply device periodically shifts to the deterioration diagnosis mode during execution of the normal mode. During execution of the deterioration diagnosis mode, the control device stops the charging of the storage battery by stopping the operation of a power converter. The control device measures the voltage (VB) of the storage battery at a first timing (t2) after the lapse of a first time (T1) after stopping the charging of the storage battery, and diagnoses the deterioration state of the storage battery on the basis of the measured value (VB1) of the voltage of the storage battery at the first timing.

Description

uninterruptible power supply

[0001] The present disclosure relates to an uninterruptible power supply, and more particularly to a technique for diagnosing the deterioration of a storage battery used in an uninterruptible power supply.

[0002] For example, Japanese Patent Laid-Open Publication No. 2008-259296 (Patent Document 1) discloses an uninterruptible power supply including an uninterruptible power supply main unit, multiple storage batteries, and an automatic storage battery deterioration diagnosis means. The uninterruptible power supply main unit has a converter that converts input power from an AC power source into DC power, and an inverter that converts the DC power output from the converter into AC power and outputs it to a load. The multiple storage batteries are connected in series to a DC power section between the converter and the inverter, and supply power to the load in the event of an abnormality in the AC power source. The automatic storage battery deterioration diagnosis means performs a test discharge on the multiple storage batteries while the uninterruptible power supply is operating, and detects an abnormality in the multiple storage batteries as a whole.

[0003] In the above configuration, the floating charge voltage of the batteries gradually decreases during test discharge of the batteries. However, as the batteries deteriorate, the decrease in floating charge voltage during discharge becomes more pronounced. If the floating charge voltage drops to the abnormality determination voltage during test discharge, the automatic battery deterioration diagnosis means determines that an abnormality has occurred in all of the batteries.

[0004] Japanese Patent Application Laid-Open No. 2008-259296

[0005] The uninterruptible power supply described in Patent Document 1, during normal operation when power is supplied from an AC power source, supplies power to a load while an automatic battery deterioration diagnosis means performs a test discharge on multiple batteries to diagnose the deterioration state of the batteries. During the test discharge, input power from the AC power source is supplied to the load via the uninterruptible power supply main body, and power discharged from the multiple batteries is supplied to the load. Therefore, when the uninterruptible power supply is operating under a light load, the current output from the uninterruptible power supply to the load is small, making it difficult to supply a constant current for test discharge to the multiple batteries. As a result, there is a concern that the automatic battery deterioration means may not be able to diagnose the deterioration state of the multiple batteries when the load current is small.

[0006] Furthermore, in order to improve the reliability of power supply from an uninterruptible power supply when an abnormality occurs in the AC power supply, it is necessary to be able to diagnose the deterioration state of the storage battery with higher accuracy.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide an uninterruptible power supply that can accurately diagnose the deterioration state of a storage battery regardless of the magnitude of the load.

[0008] An uninterruptible power supply according to the present disclosure has a normal mode in which power supplied from an AC power source is supplied to a load, a backup mode in which power stored in a storage battery is supplied to the load when the AC power source is out of service, and a degradation diagnosis mode in which the degradation state of the storage battery is diagnosed. The uninterruptible power supply includes a power converter and a control device. The power converter float-charges the storage battery using power supplied from the AC power source in the normal mode and discharges the storage battery in the backup mode. The control device periodically transitions to the degradation diagnosis mode while the normal mode is being executed. During the degradation diagnosis mode, the control device stops charging of the storage battery by stopping operation of the power converter. The control device measures the voltage of the storage battery at a first timing when a first time has elapsed since charging of the storage battery was stopped, and diagnoses the degradation state of the storage battery based on the measured value of the voltage of the storage battery at the first timing.

[0009] According to the present disclosure, it is possible to provide an uninterruptible power supply that can accurately diagnose the degradation state of a storage battery regardless of the magnitude of the load.

[0010] FIG. 1 is a circuit block diagram showing the configuration of an uninterruptible power supply according to a first embodiment. FIG. 2 is a block diagram showing an example of the hardware configuration of a control device. FIG. 3 is a block diagram showing main parts of the control device. FIG. 4 is a diagram explaining operation modes of the uninterruptible power supply. FIG. 5 is a block diagram showing parts of the control circuit related to control of the converter, inverter and bidirectional chopper. FIG. 6 is a diagram for explaining battery degradation diagnosis processing in a degradation diagnosis unit. FIG. 7 is a diagram showing an example of the relationship between battery usage time and DC resistance. FIG. 8 is a flowchart showing the flow of battery degradation diagnosis processing according to the first embodiment. FIG. 9 is a diagram for explaining degradation diagnosis processing in a degradation diagnosis unit according to a second embodiment. FIG. 10 is a flowchart showing the flow of battery degradation diagnosis processing according to the second embodiment. FIG. 11 is a flowchart showing the flow of battery degradation diagnosis processing according to a third embodiment. FIG. 12 is a circuit block diagram showing the configuration of an uninterruptible power supply according to a fourth embodiment.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and the description thereof will not be repeated.

[0012] First Embodiment <Configuration of Uninterruptible Power Supply> FIG. 1 is a circuit block diagram showing the configuration of an uninterruptible power supply according to a first embodiment.

[0013] As shown in Fig. 1, an uninterruptible power supply 100 according to the first embodiment includes an input terminal 1, a DC terminal 2, an output terminal 3, switches S1 to S3, a converter 4, current detectors CD1 to CD3, a DC line 5, a capacitor 6, a bidirectional chopper 7, an inverter 8, an operation unit 9, and a control device 10. Note that although the uninterruptible power supply 100 supplies three-phase AC power to a load 13, for the sake of simplicity of the drawings and explanation, Fig. 1 only shows the portions related to one phase.

[0014] The input terminal 1 receives AC power of a predetermined frequency (for example, a commercial frequency) from an AC power source 11. The AC power source 11 may be a commercial AC power source or a generator.

[0015] The DC terminal 2 is connected to a battery 12. The battery 12 stores DC power. The battery 12 is a secondary battery such as a lithium ion battery or a lead storage battery. The battery 12 corresponds to an example of a "storage battery."

[0016] The output terminal 3 is connected to a load 13. The load 13 is driven by AC power of a predetermined frequency (for example, a commercial frequency) supplied from the uninterruptible power supply 100.

[0017] The switch S1 is connected between the input terminal 1 and the AC node of the converter 4, and is controlled by the control device 10. When AC power is being supplied normally from the AC power supply 11 (when the AC power supply 11 is functioning properly), the switch S1 is turned on, and AC power is supplied from the AC power supply 11 to the converter 4 via the switch S1. When AC power is not being supplied normally from the AC power supply 11 (when the AC power supply 11 is experiencing a power outage), the switch S1 is turned off, and the AC power supply 11 and the converter 4 are disconnected.

[0018] The instantaneous value of the AC input voltage VI supplied from the AC power supply 11 is detected by the control device 10. Based on the instantaneous value of the AC input voltage VI, the control device 10 determines whether or not the AC voltage is being normally supplied from the AC power supply 11. The current detector CD1 detects the AC input current Ii flowing between the AC power supply 11 and the converter 4, and provides the control device 10 with a signal Iif indicating the detected value.

[0019] The converter 4 is controlled by the control device 10, and when the AC power supply 11 is healthy, converts AC power from the AC power supply 11 into DC power and outputs it to the DC line 5. The converter 4 is a well-known device that includes multiple sets of IGBTs (Insulated Gate Bipolar Transistors) and diodes.

[0020] The capacitor 6 is connected to the DC line 5 and smooths and stabilizes the DC voltage VD of the DC line 5. The instantaneous value of the DC voltage VD of the DC line 5 is detected by the control device 10.

[0021] When the AC power supply 11 is normal, the control device 10 controls the converter 4 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. When the AC power supply 11 experiences a power outage, the control device 10 stops the operation of the converter 4.

[0022] The DC line 5 is connected to the DC terminal 2 via the bidirectional chopper 7 and the switch S2. The switch S2 is controlled by the control device 10. When the uninterruptible power supply 100 is in use, the switch S2 is turned on. When maintenance of the battery 12 and the bidirectional chopper 7 is performed, the switch S2 is turned off.

[0023] The instantaneous value of the voltage VB between the terminals of the battery 12 (hereinafter also referred to as the "battery voltage") is detected by the control device 10. The current detector CD2 detects the DC current IB flowing between the battery 12 and the bidirectional chopper 7, and provides the control device 10 with a signal IBf indicating the detected value.

[0024] The bidirectional chopper 7 is controlled by a control device 10, and exchanges DC power between the DC line 5 and a battery 12. The bidirectional chopper 7 is a well-known device that includes a plurality of sets of IGBTs and diodes, and a reactor.

[0025] When the AC power supply 11 is healthy, the control device 10 controls the bidirectional chopper 7 so that the battery voltage VB becomes equal to the reference DC voltage VBR. When a power outage occurs in the AC power supply 11, the control device 10 controls the bidirectional chopper 7 so that the DC voltage VD of the DC line 5 becomes equal to the reference DC voltage VDR. The bidirectional chopper 7 corresponds to an example of a "power converter."

[0026] Furthermore, the DC line 5 is connected to a DC node of the inverter 8, and the AC node of the inverter 8 is connected to the output terminal 3 via a switch S3. The switch S3 is controlled by the control device 10. When the uninterruptible power supply 100 is in use, the switch S3 is turned on. When maintenance of the inverter 8 is performed, the switch S3 is turned off.

[0027] The current detector CD3 detects the AC output current Io of the inverter 8 and provides a signal Iof indicating the detected value to the control device 10. The AC output current Io corresponds to the load current flowing from the uninterruptible power supply 100 to the load 13. The instantaneous value of the AC output voltage VO applied to the load 13 is also detected by the control device 10.

[0028] The inverter 8 is controlled by a control device 10, and converts DC power supplied from the converter 4 and the bidirectional chopper 7 via the DC line 5 into AC power of a predetermined frequency (for example, a commercial frequency), and supplies the AC power to a load 13. The inverter 8 is a well-known device that includes multiple sets of IGBTs and diodes.

[0029] When the AC power supply 11 is operating normally, the inverter 8 converts the DC power supplied from the converter 4 or the bidirectional chopper 7 into AC power and supplies it to the load 13. At this time, the control device 10 controls the inverter 8 so that the AC output voltage VO becomes the sinusoidal reference AC voltage VOR.

[0030] The operation unit 9 includes a plurality of buttons, a plurality of switches, and an image display unit. A user of the uninterruptible power supply 100 can turn the power of the uninterruptible power supply 100 on and off, and operate the uninterruptible power supply 100 automatically or manually, by operating the operation unit 9. The operation unit 9 outputs signals and information indicating the content of operations performed by the user to the control device 10.

[0031] The control device 10 controls the switches S1 to S3, the converter 4, the bidirectional chopper 7, and the inverter 8 based on signals from the operation unit 9, the AC input voltage VI, the AC output voltage VO, the DC voltage VD, the battery voltage VB, the AC input current Ii, the battery current IB, and the AC output current Io.

[0032] 2 is a block diagram showing an example of a hardware configuration of the control device 10. Typically, the control device 10 can be configured by a microcomputer in which a predetermined program is stored in advance.

[0033] 2, the control device 10 includes a CPU (Central Processing Unit) 102, a memory 104, and an input / output (I / O) circuit 106. The CPU 102, the memory 104, and the I / O circuit 106 can exchange data with one another via a bus 108. Programs are stored in a partial area of ​​the memory 104, and the CPU 102 executes these programs to realize various functions described below. The I / O circuit 106 inputs and outputs signals and data to and from the outside of the control device 10.

[0034] 2, at least a part of the control device 10 may be configured using a circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), or at least a part of the control device 10 may be configured using an analog circuit.

[0035] <Functional Configuration of Control Device> Fig. 3 is a block diagram showing the main parts of the control device 10. As shown in Fig. 3, the control device 10 includes voltage detectors 21 to 24, a power outage detector 25, a timer 26, an output unit 27, and a control circuit 28.

[0036] The voltage detector 21 detects the instantaneous value of the AC input voltage VI supplied from the AC power supply 11, and outputs a signal VIf indicating the detected value to the power failure detector 25 and the control circuit 28. The voltage detector 22 detects the instantaneous value of the AC output voltage VO applied to the load 13, and outputs a signal VOf indicating the detected value to the control circuit 28.

[0037] The voltage detector 23 detects the instantaneous value of the DC voltage VD of the DC line 5 and outputs a signal VDf indicating the detected value to the control circuit 28. The voltage detector 24 detects the instantaneous value of the battery voltage VB and outputs a signal VBf indicating the detected value to the control circuit 28. The output signals Iif, IBf, and Iof of the current detectors CD1 to CD3 (FIG. 1) are supplied to the control circuit 28.

[0038] The power failure detector 25 detects whether a power failure has occurred in the AC power supply 11 based on the output signal VIf of the voltage detector 21, and outputs a power failure detection signal φ25 indicating the detection result to the control circuit 28. When the AC power supply 11 is healthy, the power failure detection signal φ25 is set to an inactive "H" level. When a power failure has occurred in the AC power supply 11, the power failure detection signal φ25 is set to an active "L" level.

[0039] For example, when the AC input voltage VI is higher than a lower limit, the power failure detector 25 determines that the AC power supply 11 is healthy and sets the power failure detection signal φ25 to the inactivation level "H". When the AC input voltage VI is lower than the lower limit, the power failure detector 25 determines that a power failure has occurred in the AC power supply 11 and sets the power failure detection signal φ25 to the activation level "L".

[0040] The timer 26 is reset when the reset signal RST from the control circuit 28 is set to the activated level "H" for a predetermined period of time, measures the time TD that has elapsed since the reset, and outputs a signal TDf indicating the measured time TD to the control circuit 28.

[0041] The control circuit 28 controls the entire uninterruptible power supply 100 based on the output signals VIf, VOf, VDf, VBf of the voltage detectors 21 to 24, the output signals Iif, IBf, Iof of the current detectors CD1 to CD3, the signal φ25, and a signal from the operation unit 9.

[0042] Furthermore, when the AC power supply 11 is healthy, the control circuit 28 periodically diagnoses the degradation state of the battery 12 while supplying AC power to the load 13. Based on the diagnosis result, the control circuit 28 outputs a status signal φ28 indicating the degradation state of the battery 12 to the output unit 27. The status signal φ28 can include information about the direct current resistance (DCR) of the battery 12 obtained by the degradation diagnosis.

[0043] Furthermore, the control circuit 28 determines whether the battery 12 has deteriorated based on the diagnosis result, and outputs a deterioration detection signal φ27 indicating the determination result to the output unit 27. If it is determined that the battery 12 has not deteriorated, the deterioration detection signal φ27 is set to the inactivation level "L" level. If it is determined that the battery 12 has deteriorated, the deterioration detection signal φ27 is set to the activation level "H" level. Deterioration diagnosis of the battery 12 will be described later.

[0044] Based on the status signal φ28, the output unit 27 presents an image or the like showing the deterioration state of the battery 12 to the user of the uninterruptible power supply 100. When the deterioration detection signal φ27 is set to the "H" level, which is the activation level, the output unit 27 notifies the user of the uninterruptible power supply 100 that the battery 12 is degraded by using sound, light, an image, or the like. The image display unit of the operation unit 9 can be used as the output unit 27.

[0045] Alternatively, an external device (e.g., a server) communicatively connected to the uninterruptible power supply 100 can be used as the output unit 27. The external device is configured to receive the status signal φ28 and the deterioration detection signal φ27 from the uninterruptible power supply 100 via a communication network such as the Internet, and to present information regarding the deterioration state of the battery 12 to the user based on the received signals. This allows the user of the uninterruptible power supply 100 to remotely monitor the deterioration state of the battery 12.

[0046] <Operation Modes of Uninterruptible Power Supply> Figure 4 is a diagram illustrating the operation modes of the uninterruptible power supply 100. As shown in Figure 4, the uninterruptible power supply 100 has a normal mode, a backup mode, and a degradation diagnosis mode. The control circuit 28 selectively executes the normal mode, the backup mode, and the degradation diagnosis mode based on the power failure detection signal φ25, the output signal TDf of the timer 26, and the reset signal RST.

[0047] (Normal Mode) When the AC power supply 11 is healthy (φ25=H), the control circuit 28 executes the normal mode. In the normal mode, the control circuit 28 turns on the switches S1 to S3. Furthermore, the control circuit 28 controls the converter 4 based on the signals VIf, VDf, and Iif so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. Furthermore, the control circuit 28 controls the bidirectional chopper 7 based on the signals VBf and Ibf so that the battery voltage VB becomes the reference DC voltage VBR.

[0048] Furthermore, the control circuit 28 controls the inverter 8 based on the signals VOf and Iof so that the AC output voltage VO of the inverter 8 becomes the sinusoidal reference AC voltage VOR. In this case, a load current is supplied from the inverter 8 to the load 13, and the load 13 is operated.

[0049] (Backup Mode) When a power outage occurs in the AC power supply 11 (φ25 = L), the control circuit 28 executes the backup mode. In the backup mode, the control circuit 28 turns off the switch S1 to stop the operation of the converter 4. The control circuit 28 also controls the bidirectional chopper 7 based on the signals VBf and Ibf so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. The control circuit 28 also controls the inverter 8 based on the signals VOf and Iof so that the AC output voltage VO of the inverter 8 becomes the sinusoidal reference AC voltage VOR. Therefore, even when a power outage occurs in the AC power supply 11, the operation of the load 13 can continue as long as DC power is stored in the battery 12.

[0050] When the AC power supply 11 recovers from a power outage and returns to a normal state (φ25=H), the control circuit 28 shifts from the backup mode to the normal mode. The control circuit 28 turns on the switch S1 to start the operation of the converter 4, controls the converter 4 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VD, and controls the bidirectional chopper 7 so that the battery voltage VB becomes the reference DC voltage VBR. The control circuit 28 also controls the inverter 8 so that the AC output voltage VO of the inverter 8 becomes the sinusoidal reference AC voltage VOR.

[0051] (Degradation diagnosis mode) When the time TD indicated by the output signal TDf of the timer 26 exceeds a predetermined time Tc during execution of the normal mode, the control circuit 28 executes the degradation diagnosis mode. The predetermined time Tc is the cycle for executing the degradation diagnosis mode during execution of the normal mode.

[0052] In the degradation diagnosis mode, the control circuit 28 controls the converter 4 based on the signals VIf, VDf, and Iif so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. The control circuit 28 also controls the inverter 8 based on the signals VOf and Iof so that the AC output voltage VO of the inverter 8 becomes the sinusoidal reference AC voltage VOR.

[0053] Then, while AC power is being supplied from the inverter 8 to the load 13, the control circuit 28 diagnoses the degradation state of the battery 12. At this time, the control circuit 28 controls the operation of the bidirectional chopper 7 based on the output signal TDf of the timer 26. The control circuit 28 will be described later. The control circuit 28 diagnoses the degradation state of the battery 12 based on the battery voltage VB indicated by the signal VBf, and outputs a status signal φ28 indicating the degradation state to the output unit 27. The control circuit 28 also determines whether the battery 12 has deteriorated based on the battery voltage VB. If the control circuit 28 determines that the battery 12 has deteriorated, it sets the degradation detection signal φ27 to the "H" level, which is an activation level. If the control circuit 28 determines that the battery 12 has not deteriorated, it sets the degradation detection signal φ27 to the "L" level, which is an inactivation level.

[0054] When the execution of the degradation diagnosis mode is completed, the control circuit 28 sets the reset signal RST to the activated "H" level for a predetermined time to reset the timer 26, and then executes the normal mode again.

[0055] Furthermore, if a power outage occurs in the AC power supply 11 while the degradation diagnosis mode is being executed (φ25=L), the control circuit 28 executes the backup mode. At this time, the control circuit 28 stops the operation of the converter 4 and controls the bidirectional chopper 7 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. In response to the suspension of the execution of the degradation diagnosis mode, the control circuit 28 sets the reset signal RST to the "H" level, which is the activation level, for a predetermined time period to reset the timer 26.

[0056] <Functional Configuration of Control Circuit> Fig. 5 is a block diagram showing the portions of the control circuit 28 that are related to the control of the converter 4, the inverter 8, and the bidirectional chopper 7. As shown in Fig. 5, the control circuit 28 includes a mode setting unit 30, a command generating unit 32, a power supply control unit 34, a charge / discharge control unit 36, a deterioration diagnosis unit 38, a storage unit 40, and a threshold generating unit 42.

[0057] The mode setting unit 30 sets the operation mode of the uninterruptible power supply 100 based on the output signal φ25 of the power failure detector 25, the output signal TDf of the timer 26, and the reset signal RST provided by the degradation diagnosis unit 38.

[0058] Specifically, when the power failure detection signal φ25 is at an "H" level and the time TD measured by the timer 26 is less than the predetermined time Tc, the mode setting unit 30 sets the operation mode to the normal mode. When the power failure detection signal φ25 is at an "H" level and the time TD measured by the timer 26 exceeds the predetermined time Tc, the mode setting unit 30 sets the operation mode to the degradation diagnosis mode. When the power failure detection signal φ25 is at an "L" level, the mode setting unit 30 sets the operation mode to the backup mode. The mode setting unit 30 outputs a signal φ30 indicating the set operation mode to the power supply control unit 34 and the command generation unit 32.

[0059] The power supply control unit 34 controls the converter 4 and the inverter 8 based on the output signal φ30 of the mode setting unit 30, the output signals VIf, VDf, VOf of the voltage detectors 21 to 23, and the output signals Iif, Iof of the current detectors CD1, CD2.

[0060] Specifically, when the operation mode indicated by signal φ30 is the normal mode or the degradation diagnosis mode, the power supply control unit 34 controls the converter 4 based on the signals VIf, VDf, and Iif so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. Also, the power supply control unit 34 controls the inverter 8 based on the signals VOf and Iof so that the AC output voltage VO of the inverter 8 becomes the sinusoidal reference AC voltage VOR.

[0061] When the operation mode indicated by the signal φ30 is the backup mode, the power supply control unit 34 stops the operation of the converter 4 and controls the inverter 8 based on the signals VOf and Iof so that the AC output voltage VO of the inverter 8 becomes the sinusoidal reference AC voltage VOR.

[0062] Command generating unit 32 generates a charge command for instructing to start / stop charging of battery 12 and a discharge command for instructing to start / stop discharging of battery 12, based on output signal φ30 of mode setting unit 30 and output signal TDf of timer 26. When instructing to start charging of battery 12, the charge command is set to an activated level of "H" and when instructing to stop charging, the charge command is set to an inactivated level of "L". When instructing to start discharging of battery 12, the discharge command is set to an activated level of "H" and when instructing to stop discharging, the discharge command is set to an inactivated level of "L".

[0063] When the operation mode indicated by the signal φ30 is the normal mode, the charge command is set to the "H" level and the discharge command is set to the "L" level. When the operation mode indicated by the signal φ30 is the backup mode, the charge command is set to the "L" level and the discharge command is set to the "H" level.

[0064] When the operation mode indicated by signal φ30 is the degradation diagnosis mode, the charge command is set to "L" level and the discharge command is set to "L" level. However, while the degradation diagnosis mode is being executed, the discharge command is set to "H" level for a predetermined time T2 based on the output signal TDf of timer 26. Command generation unit 32 outputs signal φ32 indicating the generated charge command and discharge command to charge / discharge control unit 36 ​​and degradation diagnosis unit 38.

[0065] The charge / discharge control unit 36 ​​controls the bidirectional chopper 7 based on the output signal φ32 of the command generating unit 32, the output signals VDf and VBf of the voltage detectors 23 and 24, and the output signal IBf of the current detector CD2.

[0066] Specifically, when the charge command indicated by the signal φ32 is at "H" level and the discharge command is at "L" level, the charge / discharge control unit 36 ​​controls the bidirectional chopper 7 so that the battery voltage VB becomes the reference DC voltage VBR. When the charge command indicated by the signal φ32 is at "L" level and the discharge command is at "H" level, the charge / discharge control unit 36 ​​controls the bidirectional chopper 7 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR. When both the charge command and the discharge command indicated by the signal φ32 are at "L" level, the charge / discharge control unit 36 ​​stops the operation of the bidirectional chopper 7.

[0067] The deterioration diagnosis unit 38 diagnoses the deterioration state of the battery 12 based on the output signal φ32 of the command generation unit 32 , the output signal TDf of the timer 26 , and the output signal VBf of the voltage detector 24 .

[0068] <Battery Deterioration Diagnosis Processing> Fig. 6 is a diagram for explaining the deterioration diagnosis processing of the battery 12 in the deterioration diagnosis unit 38. Fig. 6 shows the waveform of the battery voltage VB indicated by the output signal VBf of the voltage detector 24, and the waveforms of the charge command and the discharge command generated by the command generation unit 32.

[0069] Referring to FIG. 6, at time t1, when the time TD measured by timer 26 exceeds a predetermined time Tc, uninterruptible power supply 100 transitions from the normal mode to the degradation diagnosis mode.

[0070] During execution of the normal mode before time t1, the charge command is set to "H" level and the discharge command is set to "L" level. In response to this "H" level charge command, the charge / discharge control unit 36 ​​controls the bidirectional chopper 7 so that the battery voltage VB becomes equal to the reference DC voltage VBR. As a result, floating charging of the battery 12 is performed, and the battery voltage VB at time t1 becomes equal to the reference DC voltage VBR.

[0071] In response to the transition to the degradation diagnosis mode at time t1, the charge command is set to "L" level. In response to this "L" level charge command, the charge / discharge control unit 36 ​​stops the operation of the bidirectional chopper 7, thereby stopping the charging of the battery 12.

[0072] After time t1, the battery voltage VB gradually drops due to the charging of the battery 12 being stopped. This drop in the battery voltage VB is caused by the internal resistance of the battery 12. Specifically, the battery voltage VB drops sharply immediately after charging is stopped. This voltage drop is due to a voltage drop (IR drop) caused by the current during charging and the internal resistance of the battery 12. The battery voltage VB continues to drop gradually even after the voltage drop due to the IR drop. This behavior of the battery voltage VB after charging is stopped is also called a relaxation characteristic or a transient characteristic.

[0073] The IR drop is mainly caused by the ohmic component contained in the internal resistance of the battery 12. The gradual voltage drop after the IR drop is caused by a component other than the ohmic component (hereinafter also referred to as the "relaxation component") contained in the internal resistance of the battery 12. Due to this relaxation component, the battery voltage VB gradually drops, for example, over a period of about 30 minutes to 1 hour after charging is stopped. The battery voltage VB eventually converges to a voltage value corresponding to the battery capacity. The time it takes for the battery voltage VB to converge after charging of the battery 12 is stopped varies depending on the battery.

[0074] As the deterioration of the battery 12 progresses, the internal resistance of the battery 12 gradually increases. In particular, the relaxation component of the internal resistance is said to increase with deterioration. Furthermore, as the battery 12 deteriorates, the voltage and battery capacity decrease. Therefore, as the deterioration of the battery 12 progresses, the amount of drop in the battery voltage VB after charging is stopped increases.

[0075] Based on the output signal VBf of the voltage detector 24, the degradation diagnosis unit 38 measures the battery voltage VB at time t2, a predetermined time T1 after the time t1 when charging of the battery 12 is stopped. In the following description, the measured value of the battery voltage VB at time t2 will be referred to as the "battery voltage VB1." The predetermined time T1 is set to, for example, about 30 minutes to 1 hour. The predetermined time T1 is set to include the time it takes for the battery voltage VB to relax after charging of the battery 12 is stopped. This makes it possible to diagnose capacity degradation of the battery 12 while minimizing the effect of the relaxation of the battery voltage VB after charging is stopped.

[0076] The deterioration diagnosis unit 38 determines whether the battery 12 has deteriorated based on the battery voltage VB1. Specifically, the deterioration diagnosis unit 38 compares the battery voltage VB1 with a predetermined threshold voltage Vth and generates a deterioration detection signal φ27 based on the comparison result. If VB1≧Vth, it is determined that the battery 12 has not deteriorated, and the deterioration detection signal φ27 is set to the "L" level. If VB1<Vth, it is determined that the battery 12 has deteriorated, and the deterioration detection signal φ27 is set to the "H" level.

[0077] Next, for a predetermined time T2 from time t3 to time t4 after time t2, the discharge command is temporarily set to the "H" level. The predetermined time T2 is set to, for example, several tens of milliseconds to one second.

[0078] The charge / discharge control unit 36 ​​operates the bidirectional chopper 7 in response to this "H" level discharge command, thereby performing pulse discharge of the battery 12. The charge / discharge control unit 36 ​​controls the bidirectional chopper 7 so that the DC voltage VD of the DC line 5 becomes the reference DC voltage VDR at the predetermined time T2. During the execution of pulse discharge, the battery 12 is discharged at a constant current value.

[0079] During pulse discharge, the battery voltage VB drops. Specifically, immediately after pulse discharge begins, the battery voltage VB drops sharply due to the internal resistance of the battery 12, and then gradually drops again. The degradation diagnosis unit 38 measures the minimum voltage of the battery 12 during pulse discharge based on the output signal VBf of the voltage detector 24. In the following description, the measured minimum voltage during pulse discharge is referred to as "battery voltage VB2." The battery voltage VB2 corresponds to the battery voltage VB at time t4 when pulse discharge is stopped.

[0080] At time t4, the pulse discharge is stopped, and the battery voltage VB begins to rise. Immediately after the pulse discharge is stopped, the battery voltage VB rises sharply. This voltage rise is caused by the current during discharge and the internal resistance of the battery 12.

[0081] Based on the output signal VBf of the voltage detector 24, the degradation diagnosis unit 38 measures the battery voltage VB at time t5, which is a predetermined time T3 after time t4, when the pulse discharge is stopped. The predetermined time T3 is set to, for example, several tens of milliseconds to about one second. In the following description, the measured value of the battery voltage VB at time t5 will be referred to as "battery voltage VB3."

[0082] Next, the degradation diagnosis unit 38 calculates the direct current resistance (DCR) of the battery 12 using the battery voltage VB2, which is the minimum voltage during pulse discharge, the battery voltage VB3 immediately after pulse discharge, and the current value I during pulse discharge. The DCR is calculated using the following equation (1). The DCR includes the ohmic component and the mitigation component described above. DCR = (VB3 - VB2) / I (1) The degradation diagnosis unit 38 determines the degradation state of the battery 12 based on the calculated DCR. In some aspects, the degradation diagnosis unit 38 determines the progression of degradation of the battery 12 by comparing the DCR calculated in a previous degradation diagnosis mode with the DCR calculated in the current degradation diagnosis mode. For example, if the increase in DCR since the previous degradation diagnosis mode is greater than the increase in DCR in the past, it can be determined that the rate of degradation of the battery 12 is increasing. In this case, the life of the battery 12 is expected to be shorter than expected. Conversely, if it is determined from the increase in DCR that the rate of deterioration of the battery 12 is slow, it is predicted that the life of the battery 12 will be longer than expected. The deterioration diagnosis unit 38 generates the status signal φ28 based on these determination results.

[0083] Furthermore, the degradation diagnosis unit 38 determines whether the battery 12 has deteriorated based on the calculated DCR. Specifically, the degradation diagnosis unit 38 compares the calculated DCR with a threshold DCRth provided by the threshold generation unit 42, and generates a degradation detection signal φ27 based on the comparison result. If DCR≦DCRth, it is determined that the battery 12 has not deteriorated, and the degradation detection signal φ27 is set to the "L" level. If DCR>DCRth, it is determined that the battery 12 has deteriorated, and the degradation detection signal φ27 is set to the "H" level.

[0084] When the execution of the degradation diagnosis mode ends (time t6), degradation diagnosis unit 38 sets reset signal RST to "H" level for a predetermined time to reset timer 26, and executes the normal mode again, thereby setting the charge command to "H" level.

[0085] 5 , the degradation diagnosis unit 38 outputs the generated status signal φ28 and degradation detection signal φ27 to the output unit 27. The output unit 27 presents information about the degradation state of the battery 12 to the user of the uninterruptible power supply 100 based on the status signal φ28. For example, the output unit 27 generates a graph (see FIG. 7 ) showing the time progression of the calculated DCR value and displays it on the image display unit of the operation unit 9 (or the display of an external device). Furthermore, when the degradation detection signal φ27 is at an “H” level, the output unit 27 notifies the user of the uninterruptible power supply 100 that the battery 12 is degraded by using sound, light, images, etc.

[0086] Furthermore, the degradation diagnosis unit 38 stores the calculated DCR in the storage unit 40. The storage unit 40 stores the usage time of the battery 12 and the calculated DCR value in association with each other. Fig. 7 is a diagram showing an example of the relationship between the usage time of the battery 12 and the DCR. The horizontal axis of Fig. 7 represents the usage time of the battery 12 replaced with a new one, and the vertical axis of Fig. 7 represents the DCR of the battery 12.

[0087] 7 plots the DCR of the battery 12 calculated each time the degradation diagnosis mode is executed. As shown in Fig. 7, the DCR increases as the usage time of the battery 12 increases. In the example of Fig. 7, the longer the usage time, the greater the increase in DCR relative to the cycle of executing the degradation diagnosis mode.

[0088] 5 , the threshold generator 42 sets the threshold DCRth. In one aspect, the threshold generator 42 can set the threshold DCRth by amplifying a predetermined reference value (e.g., a design value) for the battery 12 by M times, where M is a number greater than 1. By setting the threshold DCRth using the reference value of the DCR in this manner, it is possible to determine the deterioration of the battery 12 from the increase in the DCR relative to the reference value (relative ratio).

[0089] In another aspect, the threshold generator 42 can set the threshold DCRth based on the relationship between the usage time of the battery 12 and the DCR (the graph in FIG. 7 ) stored in the memory 40. Specifically, the threshold generator 42 sets the threshold DCRth by amplifying the value of the DCR at the beginning of use of the battery 12 (corresponding to DCRi in FIG. 7 ) by N times (DCRth = DCRi × N), where N is a number greater than 1.

[0090] In this way, by setting the threshold DCRth using the DCRi at the beginning of use of the battery 12, it is possible to determine the deterioration of the battery 12 from the increase in DCR (relative ratio) to DCRi. For a battery with a small DCRi, even if the calculated DCR value does not reach M times the reference value described above, the rate of deterioration may tend to increase due to some abnormality. By setting the threshold DCRth using DCRi, it is possible to detect abnormalities that accelerate the progression of battery deterioration early, regardless of individual differences between batteries.

[0091] FIG. 8 is a flowchart showing a flow of a deterioration diagnosis process for battery 12 according to the first embodiment.

[0092] As shown in FIG. 8, in step (hereinafter simply referred to as "S") 01, the control device 10 transitions to the degradation diagnosis mode in response to the measured time TD of the timer 26 exceeding the predetermined time Tc while the normal mode is being executed.

[0093] In the degradation diagnosis mode, the control device 10 first stops the operation of the bidirectional chopper 7 in step S02, thereby stopping the charging of the battery 12. As shown in Fig. 6, the battery voltage VB drops due to the stopping of the charging of the battery 12.

[0094] In step S03, the control device 10 measures the battery voltage VB1 based on the output signal TDf of the timer 26 and the output signal VBf of the voltage detector 24 at a time (time t2 in FIG. 6) when a predetermined time T1 has elapsed since the time (time t1 in FIG. 6) when charging of the battery 12 was stopped.

[0095] In S04, the control device 10 compares the battery voltage VB1 with the threshold voltage Vth. If VB1<Vth (NO in S04), in S14, the control device 10 determines that the battery 12 has deteriorated and outputs an "H" level deterioration detection signal φ27 to the output unit 27. In S14, the output unit 27 notifies the user of the uninterruptible power supply 100 that the battery 12 has deteriorated using sound, light, an image, or the like.

[0096] On the other hand, if VB1≧Vth (YES in S04), the control device 10 executes pulse discharge of the battery 12 for a predetermined time T2 in S05 based on the output signal TDf of the timer 26. In S05, the control device 10 discharges the battery 12 at a constant current value.

[0097] During the execution of pulse discharge, the control device 10 measures the minimum voltage of the battery 12 (battery voltage VB2) based on the output signal VBf of the voltage detector 24 in S06.

[0098] Next, in S07, the control device 10 measures the battery voltage VB3 at the time (time t4 in Figure 6) when a predetermined time T3 has elapsed since the time when the pulse discharge was stopped (time t5 in Figure 6) based on the output signal VBf of the voltage detector 24.

[0099] In S08, the control device 10 calculates the DCR of the battery 12 according to equation (1) using the battery voltages VB2 and VB3 measured in S06 and S07 and the current value I during pulse discharge.

[0100] In S09, the control device 10 generates a status signal φ28 indicating the degradation state of the battery 12 based on the DCR calculated in S08, and outputs the signal to the output unit 27. The output unit 27 presents information regarding the degradation state of the battery 12 to the user of the uninterruptible power supply 100 based on the status signal φ28. In S09, for example, the output unit 27 displays a graph (see FIG. 7 ) showing the time progression of the calculated value of the DCR calculated each time the degradation diagnosis mode is executed on the image display unit of the operation unit 9 (or the display of an external device).

[0101] In S10, the control device 10 stores the DCR calculated in S08 in the internal memory.

[0102] In S11, the control device 10 compares the DCR calculated in S08 with a threshold value DCRth. If DCR≦DCRth (NO in S11), the control device 10 determines in S12 that the battery 12 is not degraded and sets the degradation detection signal φ27 to the “L” level. Next, in S13, the control device 10 sets the reset signal RST to the “H” level for a predetermined period of time to reset the timer 26. The reset timer 26 restarts measuring the time TD from 0 seconds. This ends the degradation diagnosis mode and transitions to the normal mode.

[0103] On the other hand, if DCR>DCRth (YES in S11), the control device 10 determines in S14 that the battery 12 has deteriorated and outputs an "H" level deterioration detection signal φ27 to the output unit 27. In S15, the output unit 27 notifies the user of the uninterruptible power supply 100 that the battery 12 has deteriorated.

[0104] <Effects> As described above, in the first embodiment, the degradation state of the battery 12 is diagnosed based on the battery voltage VB1 at the time when the predetermined time T1 has elapsed since charging of the battery 12 was stopped. This makes it possible to perform a degradation diagnosis of the battery 12 without test discharging the battery 12. Furthermore, by setting the predetermined time T1 to include the time (e.g., approximately 30 minutes to 1 hour) during which the battery voltage VB relaxes after charging of the battery 12 is stopped, the effect of the relaxation of the battery voltage VB after charging is stopped is reduced, and it is possible to accurately diagnose the capacity degradation of the battery 12.

[0105] In addition, in embodiment 1, pulse discharge is performed after a predetermined time T1 has elapsed since charging of battery 12 was stopped, and the DCR of battery 12 is calculated from the minimum voltage VB2 during pulse discharge and the battery voltage VB3 immediately after pulse discharge.

[0106] Here, the DCR of battery 12 can also be calculated based on the battery voltage VB1 before the start of pulse discharge and the minimum voltage VB2 during pulse discharge. However, because the battery voltage VB1 is affected to a large extent by the relaxation of the battery voltage VB after charging is stopped, the accuracy of the DCR may be reduced. In contrast, in the first embodiment, the DCR is calculated based on the minimum voltage VB2 during pulse discharge and the battery voltage VB3 immediately after pulse discharge, thereby reducing the effect of the relaxation of the battery voltage VB and enabling the DCR to be calculated with high accuracy.

[0107] If the predetermined time T1 is set to a sufficiently long time in consideration of the relaxation characteristics of the battery voltage VB, the effect of relaxation contained in the battery voltage VB1 at the time when the predetermined time T1 has elapsed will be smaller. In such a case, the DCR may be calculated based on the battery voltage VB1 and the minimum voltage VB2 during pulse discharge.

[0108] Furthermore, by setting the threshold value DCRth to be compared with the calculated DCR using the DCRi at the beginning of use of the battery 12, it becomes possible to detect abnormalities that accelerate the progression of battery deterioration early, regardless of individual differences between batteries.

[0109] [Embodiment 2] In Embodiment 1, pulse discharge is performed while the degradation diagnosis mode is being executed, and the DCR of battery 12 is calculated based on the minimum voltage VB2 during pulse discharge, the battery voltage VB3 immediately after pulse discharge, and the current value during pulse discharge. However, there is a concern that pulse discharge at a constant current may not be possible when uninterruptible power supply 100 is under a light load. Embodiment 2 aims to solve this concern.

[0110] The uninterruptible power supply 100 according to the second embodiment has the same configuration and operation as the uninterruptible power supply 100 according to the first embodiment, except for the processing in the degradation diagnosis mode described below.

[0111] <Deterioration Diagnosis Processing> Figure 9 is a diagram for explaining the deterioration diagnosis processing in deterioration diagnosis unit 38 according to the second embodiment, and is a diagram to be compared with Figure 6. Figure 9 shows the waveform of battery voltage VB indicated by output signal VBf of voltage detector 24, and the waveforms of the charge command and discharge command generated by command generating unit 32. The deterioration diagnosis processing shown in Figure 9 differs from the deterioration diagnosis processing shown in Figure 6 in that pulse discharging of battery 12 is replaced by pulse charging.

[0112] Specifically, during the degradation diagnosis mode, the discharge command is maintained at the "L" level. During a predetermined time T4 from time t7 to time t8, which is after time t2 when the predetermined time T1 has elapsed since time t1 when charging of the battery 12 was stopped, the discharge command is temporarily set to the "H" level. The predetermined time T4 is set to, for example, about one second.

[0113] In response to this "H" level charge command, the charge / discharge control unit 36 ​​operates the bidirectional chopper 7 to pulse charge the battery 12. The charge / discharge control unit 36 ​​controls the bidirectional chopper 7 so that the battery voltage VB becomes equal to the reference DC voltage VBR at a predetermined time T4. During pulse charging, the battery 12 is charged at a constant current value.

[0114] During pulse charging, the battery voltage VB increases. Specifically, immediately after pulse charging begins, the battery voltage VB rises sharply due to the internal resistance of the battery 12, and then gradually increases. The degradation diagnosis unit 38 measures the maximum voltage of the battery 12 during pulse charging based on the output signal VBf of the voltage detector 24. In the following description, the measured maximum voltage during pulse charging is referred to as "battery voltage VB4." Battery voltage VB4 corresponds to the battery voltage VB at time t8 when pulse charging is stopped.

[0115] At time t8, pulse charging is stopped, and battery voltage VB begins to drop. Immediately after pulse charging is stopped, battery voltage VB drops sharply. This voltage drop is caused by the current during charging and the internal resistance of battery 12. Thereafter, battery voltage VB gradually drops.

[0116] Based on the output signal VBf of the voltage detector 24, the degradation diagnosis unit 38 measures the battery voltage VB at time t9, which is a predetermined time T5 after time t8, when the pulse charging was stopped. The predetermined time T5 is set to, for example, several tens of milliseconds to about one second. In the following description, the measured value of the battery voltage VB at time t9 will be referred to as "battery voltage VB5."

[0117] Next, the degradation diagnosis unit 38 calculates the DCR of the battery 12 using the battery voltage VB4, which is the maximum voltage during pulse charging, the battery voltage VB5 immediately after pulse charging, and the current value I during pulse charging. The DCR is calculated using the following equation (2): DCR=(VB4-VB5) / I (2) The degradation diagnosis unit 38 determines the degradation state of the battery 12 based on the calculated DCR. As described in the first embodiment, the degradation diagnosis unit 38 determines the progression of degradation of the battery 12, for example, by comparing the DCR calculated in a previous degradation diagnosis mode with the DCR calculated in the current degradation diagnosis mode. Specifically, the degradation diagnosis unit 38 determines the progression rate of degradation of the battery 12 based on the increase in DCR relative to the cycle in which the degradation diagnosis mode is executed, and generates a status signal φ28 based on the determination result.

[0118] Furthermore, the degradation diagnosis unit 38 determines whether the battery 12 has deteriorated based on the calculated DCR. Specifically, the degradation diagnosis unit 38 compares the calculated DCR with a threshold DCRth provided by the threshold generation unit 42, and generates a degradation detection signal φ27 based on the comparison result. If DCR≦DCRth, it is determined that the battery 12 has not deteriorated, and the degradation detection signal φ27 is set to the "L" level. If DCR>DCRth, it is determined that the battery 12 has deteriorated, and the degradation detection signal φ27 is set to the "H" level.

[0119] Fig. 10 is a flowchart showing the flow of a degradation diagnosis process for battery 12 according to embodiment 2. In the flowchart shown in Fig. 10, the processes in S05 to S07 in the flowchart shown in Fig. 8 are replaced with S05A to S07A.

[0120] 10, if VB1≧Vth in S04, which is the same as in Fig. 8 (YES in S04), the control device 10 performs pulse charging of the battery 12 for a predetermined time T4 in S05A based on the output signal TDf of the timer 26. In S05A, the control device 10 charges the battery 12 at a constant current value.

[0121] During pulse charging, in step S06A, control device 10 measures the maximum voltage of battery 12 (battery voltage VB4) based on output signal VBf of voltage detector 24.

[0122] Next, in S07A, the control device 10 measures the battery voltage VB5 at the time (time t8 in Figure 9) when a predetermined time T5 has elapsed since the time when pulse charging was stopped (time t9 in Figure 9) based on the output signal VBf of the voltage detector 24.

[0123] In S08, the control device 10 calculates the DCR of the battery 12 according to equation (2) using the battery voltages VB4 and VB5 measured in S06A and S07A and the current value I during pulse charging. Using the calculated DCR, the control device 10 executes the same processes of S09 to S15 as in FIG. 8.

[0124] <Effects> According to the second embodiment, the same effects as those of the first embodiment can be obtained. Furthermore, even when the uninterruptible power supply 100 is under a light load, the DCR of the battery 12 can be calculated by executing pulse charging of the battery 12.

[0125] Also in the second embodiment, by calculating the DCR of the battery 12 from the maximum voltage VB4 during pulse charging and the battery voltage VB5 immediately after pulse charging, the influence of relaxation of the battery voltage VB can be reduced and the DCR can be calculated with high accuracy compared to when the DCR is calculated based on the battery voltage VB1 before the start of pulse charging and the maximum voltage VB4 during pulse charging.

[0126] However, if the predetermined time T1 is set to a sufficiently long time, the effect of relaxation contained in the battery voltage VB1 at the time when the predetermined time T1 has elapsed will be smaller, so the DCR may be calculated based on the battery voltage VB1 and the maximum voltage VB4 during pulse charging.

[0127] In the first and second embodiments, pulse discharge (or pulse charge) is performed during execution of the degradation diagnosis mode, and the DCR of the battery 12 is calculated based on the amount of change in the battery voltage VB immediately after the pulse discharge (or pulse charge) and the current value during the pulse discharge (or pulse charge). In the third embodiment, either pulse discharge or pulse charge is performed during execution of the degradation diagnosis mode depending on the magnitude of the load current, and the DCR of the battery 12 is calculated.

[0128] The uninterruptible power supply 100 according to the third embodiment has the same configuration and operation as the uninterruptible power supply 100 according to the first embodiment, except for the processing in the degradation diagnosis mode described below.

[0129] 11 and 12 are flowcharts showing the flow of a degradation diagnosis process for battery 12 according to the third embodiment. The flowchart shown in Fig. 11 is obtained by adding the process of S16 to the flowchart shown in Fig. 8. The flowchart shown in Fig. 12 is obtained by extracting the processes of S05A to S07A from the flowchart shown in Fig. 10.

[0130] 11, if VB1≧Vth is satisfied in S04, the same as in FIG. 8 (YES in S04), the control device 10 proceeds to S16 and compares the load current Io indicated by the output signal Iof of the current detector CD3 with a predetermined reference current Ioth. This reference current Ioth is a load current for determining whether the uninterruptible power supply 100 is operating under a light load.

[0131] If Io≧Ioth (YES in S16), the control device 10 determines that the uninterruptible power supply 100 is not operating under a light load. In this case, the control device 10 performs pulse discharge of the battery 12 and measures the battery voltages VB2 and VB3 in the same steps S05 to S07 as in Fig. 8. Then, the control device 10 calculates the DCR of the battery 12 based on the amount of change in the battery voltage VB and the current value during pulse discharge in the same steps S08 to S15 as in Fig. 8, and diagnoses the degradation state of the battery 12 using the calculated DCR.

[0132] On the other hand, if Io≧Ioth (YES in S16), the control device 10 determines that the uninterruptible power supply 100 is operating under a light load. In this case, the control device 10 pulse charges the battery 12 and measures the battery voltages VB4 and VB5 in steps S05A to S07A, which are the same as those in Fig. 10. The control device 10 then calculates the DCR of the battery 12 based on the amount of change in the battery voltage VB and the current value during pulse discharge in steps S08 to S15, which are the same as those in Fig. 8, and uses the calculated DCR to diagnose the degradation state of the battery 12.

[0133] <Effects> According to the third embodiment, when the load on the uninterruptible power supply 100 fluctuates, it is possible to switch between pulse discharging and pulse charging of the battery 12 depending on the magnitude of the load. As a result, it is possible to calculate the DCR of the battery 12 and diagnose the degradation state of the battery 12 regardless of the magnitude of the load.

[0134] [Fourth Embodiment] Uninterruptible power supplies to which a degradation diagnosis method for battery 12 according to this embodiment is applied can include, in addition to uninterruptible power supply 100 shown in Fig. 1, an uninterruptible power supply 110 shown in Fig. 13. Uninterruptible power supply 110 is also called a momentary voltage sag compensator.

[0135] Fig. 13 is a circuit block diagram showing the configuration of an uninterruptible power supply 110 according to embodiment 4. This uninterruptible power supply 110 supplies three-phase AC power to a load, but for the sake of simplicity of the drawing and explanation, Fig. 13 shows only the parts related to one phase.

[0136] 13, the uninterruptible power supply 110 includes an input terminal 1, an output terminal 3, a DC terminal 2, breakers B1 to B4, a high-speed switch (HSS) 51, a transformer 53, a bidirectional converter 52, and a control device 55. The uninterruptible power supply 110 differs from the uninterruptible power supply 100 shown in FIG. 1 in that the uninterruptible power supply 110 includes the HSS 51, the transformer 53, the bidirectional converter 52, and the control device 55 instead of the converter 4, the bidirectional chopper 7, the inverter 8, and the control device 10.

[0137] Each of the breakers B1 to B4 is, for example, a VCB (Vacuum Circuit Breaker). Breaker B1 is connected between input terminal 1 and output terminal 3. When the uninterruptible power supply 110 is in use, breaker B1 is turned off. During maintenance of the uninterruptible power supply 110, breaker B1 is turned on, and AC input voltage VI from AC power supply 11 is supplied to load 13 via breaker B1.

[0138] Breaker B2 is connected between input terminal 1 and one terminal 51a of HSS 51. Breaker B3 is connected between the other terminal 51b of HSS 51 and output terminal 3. When the uninterruptible power supply 110 is in use, breakers B2 and B3 are turned on. When maintenance of the uninterruptible power supply 110 is performed, breakers B2 and B3 are turned off.

[0139] The HSS 51 is configured by, for example, a semiconductor switching element and is controlled by the control device 55. When the AC power supply 11 is healthy (normal mode and degradation diagnosis mode), the HSS 51 is turned on, and the AC input voltage VI from the AC power supply 11 is supplied to the load 13 via breaker B2, the HSS 51, and breaker B3. When the AC power supply 11 experiences a power outage (backup mode), the HSS 51 is turned off, and the AC power supply 11 and the load 13 are electrically disconnected. The instantaneous value of the AC voltage VO appearing at the other terminal 51b of the HSS 51 is detected by the control device 55.

[0140] Breaker B4 is connected between the other terminal 51b of the HSS 51 and a primary winding 53b of the transformer 53. When the uninterruptible power supply 110 is in use, breaker B4 is turned on. When maintenance of the uninterruptible power supply 110 is performed, breaker B4 is turned off. A secondary winding 53a of the transformer 53 is connected to an AC terminal 52b of the bidirectional converter 52. The transformer 53 exchanges AC power between the other terminal 51b of the HSS 51 and the AC terminal 52b of the bidirectional converter 52. The instantaneous value of the AC voltage VAC appearing at the AC terminal 52b of the bidirectional converter 52 is detected by a control device 55.

[0141] A DC terminal 52a of the bidirectional converter 52 is connected to the DC terminal 2. The bidirectional converter 52 is controlled by a control device 55. When the AC power supply 11 is operating normally (normal mode), the bidirectional converter 52 converts AC power supplied from the AC power supply 11 via the breaker B2, the HSS 51, the breaker B4, and the transformer 53 into DC power and stores the DC power in the battery 12. When the AC power supply 11 is in a power outage (backup mode), the bidirectional converter 52 converts the DC power of the battery 12 into AC power of a commercial frequency and supplies the AC power to the load 13 via the transformer 53 and the breakers B4 and B3. The bidirectional converter 52 corresponds to an embodiment of a "power converter."

[0142] The control device 55 controls the HSS 51 and the bidirectional converter 52 based on the AC voltages VI, VO, and VAC and the battery voltage VB. That is, when the AC power supply 11 is healthy (φ25=H), the control device 55 executes the normal mode. In the normal mode, the control device 55 turns on the breakers B2 to B4 and the HSS 51. The control device 55 also controls the bidirectional converter 52 in synchronization with the AC input voltage VI so that the battery voltage VB becomes equal to the reference DC voltage VBR.

[0143] When the battery voltage VB reaches the reference DC voltage VBR, the control device 55 controls the bidirectional converter 52 to convert the battery voltage VB into an AC voltage VAC of the commercial frequency.

[0144] When the phase of the AC output voltage VAC of the bidirectional converter 52 is made to lead the phase of the AC input voltage VI from the AC power supply 11, power flows from the battery 12 to the load 13 via the bidirectional converter 52, and the battery voltage VB drops. When the phase of the AC output voltage VAC is made to lag the phase of the AC input voltage VI, power flows from the AC power supply 11 to the battery 12 via the bidirectional converter 52, and the battery voltage VB rises. The control device 55 controls the bidirectional converter 52 to adjust the phase of the AC voltage VAC and maintains the battery voltage VB at the reference DC voltage VBR.

[0145] When a power outage occurs in the AC power supply 11 (φ25=L), the control device 55 executes the backup mode. In the backup mode, the control device 55 turns off the HSS 51 and controls the bidirectional converter 52 so that the AC voltage VO becomes the reference AC voltage VOR. When the AC power supply 11 recovers from the power outage state to a healthy state (φ25=H), the control device 55 transitions from the backup mode to the normal mode. The control device 55 controls the bidirectional converter 52 to match the phase and frequency of the AC voltage VO with the phase and frequency of the AC input voltage VI, and then turns on the HSS 51.

[0146] During the normal mode, if the time TD indicated by the output signal TDf of a timer (not shown) exceeds a predetermined time Tc, the control device 55 executes the degradation diagnosis mode. In the degradation diagnosis mode, the control device 55 diagnoses the degradation state of the battery 12 while supplying AC power to the load 13. The control device 55 controls the operation of the bidirectional converter 52 based on the output signal TDf of the timer. In one aspect, as shown in FIG. 6 , the control device 55 stops the operation of the bidirectional converter 52 for a predetermined time T1 to stop charging the battery 12, and determines whether the battery 12 has deteriorated based on the battery voltage VB1 at the time when the predetermined time T1 has elapsed since charging was stopped. The control device 55 further executes pulse discharge of the battery 12 and calculates the DCR of the battery 12 based on the minimum voltage VB2 during pulse discharge and the battery voltage VB2 immediately after pulse discharge. The control device 55 determines the deterioration state of the battery 12 based on the calculated DCR, and compares the calculated DCT with a threshold DCRth to determine whether the battery 12 has deteriorated based on the comparison result.

[0147] In another aspect, as shown in FIG. 9 , the control device 55 stops the operation of the bidirectional converter 52 for a predetermined time T1 to stop charging the battery 12, and determines whether the battery 12 has deteriorated based on the battery voltage VB1 at the time when the predetermined time T1 has elapsed since charging was stopped. The control device 55 further pulse-charges the battery 12 and calculates the DCR of the battery 12 based on the maximum voltage VB4 during pulse charging and the battery voltage VB5 immediately after pulse charging. The control device 55 determines the deterioration state of the battery 12 based on the calculated DCR, compares the calculated DCR with a threshold DCRth, and determines whether the battery 12 has deteriorated based on the comparison result. When execution of the deterioration diagnosis mode ends, the control device 55 sets the reset signal RST to the activated “H” level for a predetermined time to reset the timer, and executes the normal mode again.

[0148] Furthermore, if a power outage occurs in the AC power supply 11 (φ25=L) while the degradation diagnosis mode is being executed, the control device 55 executes the backup mode. In response to the interruption of the execution of the degradation diagnosis mode, the control device 55 sets the reset signal RST to the activated "H" level for a predetermined time period to reset the timer.

[0149] <Effects> The same effects as those of the first embodiment can be obtained in the fourth embodiment. Note that the fourth embodiment may also be configured to switch between pulse discharging and pulse charging of the battery 12 depending on the magnitude of the load when the load on the uninterruptible power supply 110 fluctuates. This makes it possible to calculate the DCR of the battery 12 and diagnose the degradation state of the battery 12 regardless of the magnitude of the load.

[0150] [Other Configuration Examples] In the above-described first to fourth embodiments, configurations for diagnosing the degradation state of a battery used in an uninterruptible power supply have been described. However, the degradation diagnosis method according to the present embodiment can also be applied to a configuration for diagnosing the degradation state of each of multiple battery modules that make up a battery. For example, the terminal voltage of each battery module can be measured a predetermined time after charging of the battery is stopped, and the degradation state of the battery module can be diagnosed based on the measured terminal voltage value. Furthermore, by calculating the DCR of each battery module from the amount of change in the terminal voltage of each battery module immediately after pulse discharging or pulse charging of the battery, the degradation state of the battery module can be determined based on the calculated DCR value.

[0151] Furthermore, the degradation diagnosis method according to the present embodiment can also be applied to a configuration in which the degradation state of each of a plurality of battery cells constituting a battery module is diagnosed. In one aspect, the terminal voltage of each battery cell is measured at a time when a predetermined time has elapsed since charging of the battery is stopped, and the degradation state of the battery cell can be diagnosed based on the measured terminal voltage. Also, by calculating the DCR of each battery cell from the amount of change in the terminal voltage of each battery cell immediately after pulse discharging or pulse charging of the battery, the degradation state of the battery cell can be determined based on the calculated DCR.

[0152] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The present disclosure is defined by the scope of the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0153] 1 Input terminal, 2 DC terminal, 3 Output terminal, 4 Converter, 5 DC line, 6 Capacitor, 7 Bidirectional chopper, 8 Inverter, 9 Operation unit, 10, 55 Control device, 11 AC power supply, 12 Battery, 13 Load, 21 to 24 Voltage detector, 25 Power outage detector, 26 Timer, 27 Output unit, 28 Control circuit, 30 Mode setting unit, 32 Command generation unit, 34 Power supply control unit, 36 Charging / discharging control unit, 38 Degradation diagnosis unit, 40 Memory unit, 42 Threshold generation unit, 51 HSS, 52 Bidirectional converter, 53 Transformer, 100, 110 Uninterruptible power supply, 102 CPU, 104 Memory, 106 I / O circuit, 108 Bus, S1 to S3 Switches, CD1 to CD3 Current detectors, B1 to B4 Breakers.

Claims

1. An uninterruptible power supply having a normal mode in which power supplied from an AC power source is supplied to a load, a backup mode in which power stored in a storage battery is supplied to the load in the event of a power outage of the AC power source, and a degradation diagnosis mode in which the storage battery's degradation state is diagnosed, the uninterruptible power supply comprising: a power converter that float-charges the storage battery using power supplied from the AC power source in the normal mode and discharges the storage battery in the backup mode; and a control device, wherein the control device periodically transitions to the degradation diagnosis mode while the normal mode is being executed, and while the degradation diagnosis mode is being executed, the control device: stops charging of the storage battery by stopping operation of the power converter; measures the voltage of the storage battery at a first timing when a first time has elapsed since charging of the storage battery was stopped; and diagnoses the degradation state of the storage battery based on the measured value of the voltage of the storage battery at the first timing.

2. The uninterruptible power supply device of claim 1, wherein the control device further: operates the power converter to perform pulse discharging of the storage battery at a second time after the first timing; measures a minimum voltage of the storage battery during the pulse discharging; measures the voltage of the storage battery at a second timing a third time after the pulse discharging is stopped; calculates a DC resistance of the storage battery based on the minimum voltage, the measured value at the second timing and the current value during the pulse discharging; and diagnoses a deterioration state of the storage battery based on the calculated DC resistance.

3. The uninterruptible power supply device of claim 1, wherein the control device further: operates the power converter to perform pulse charging of the storage battery at a second time after the first timing; measures a maximum voltage of the storage battery during the pulse charging; measures the voltage of the storage battery at a second timing a third time after the pulse charging is stopped; calculates a DC resistance of the storage battery based on the maximum voltage, the measured value at the second timing and the current value during the pulse charging; and diagnoses a deterioration state of the storage battery based on the calculated DC resistance.

4. The uninterruptible power supply device of claim 1, wherein the control device further: when the load current supplied to the load is greater than a predetermined reference current, operates the power converter to perform pulse discharging of the storage battery at a second time after the first timing, measures a minimum voltage of the storage battery during the pulse discharging, measures the voltage of the storage battery at a second timing a third time after the pulse discharging is stopped, calculates a DC resistance of the storage battery based on the minimum voltage, the measured value at the second timing and the current value during the pulse discharging, and diagnoses a deterioration state of the storage battery based on the calculated DC resistance.

5. The uninterruptible power supply according to claim 4, wherein the control device further performs pulse charging of the storage battery by operating the power converter at a fourth time after the first timing when the load current is smaller than the reference current, measures a maximum voltage of the storage battery during the pulse charging, measures the voltage of the storage battery at a fourth timing which is a fifth time after the pulse charging is stopped, calculates a DC resistance of the storage battery based on the maximum voltage, the measured value at the fourth timing and the current value during the pulse charging, and diagnoses a deterioration state of the storage battery based on the calculated DC resistance.

6. An uninterruptible power supply as claimed in any one of claims 2 to 5, wherein the control device generates a status signal representing the degradation state of the storage battery from the time progression of the calculated value of the DC resistance calculated each time the degradation diagnosis mode is executed, and further comprises an output unit that presents information regarding the degradation state of the storage battery to a user of the uninterruptible power supply based on the status signal.

7. An uninterruptible power supply device as described in any one of claims 2 to 5, wherein the control device stores in a memory unit a corresponding time period during which the storage battery is used and the calculated value of the DC resistance, sets a threshold value by amplifying the DC resistance at the beginning of use of the storage battery stored in the memory unit by a predetermined factor, and diagnoses that the storage battery is degraded when the calculated value of the DC resistance is greater than the threshold value.

8. The uninterruptible power supply according to claim 1, wherein said control device transitions to said backup mode when a power outage occurs in said AC power supply while said degradation diagnosis mode is being executed.

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