Uninterruptible power supply device

Abstract

A bidirectional chopper (2) selectively performs a charging operation for storing DC power received from DC bus lines (L1, L2) into an electricity storage device (7) and a discharging operation for outputting the DC power of the electricity storage device (7) to the DC bus lines (L1, L2). An inverter (3) converts the DC power received from the DC bus lines (L1, L2) into AC power to supply the AC power to a load (8) and converts a regenerative power generated by the load (8) into DC power to output the DC power to the DC bus lines (L1, L2). In the electricity storage device (7), a SOC reference value is set that is smaller than the upper limit value of an SOC usable range and larger than the lower limit value of the usable range. When an AC power supply (6) is healthy, a control device (5) controls the bidirectional chopper (2) so that the SOC of the electricity storage device (7) becomes the SOC reference value. When the AC power supply (6) is failed, the control device (5) controls, on the basis of the usable range, the discharging operation corresponding to the powering operation of the load (8) and the charging operation corresponding to the regenerative operation of the load (8).

Description

[Technical field]

[0001] The present disclosure relates to uninterruptible power supplies. [Background technology]

[0002] International Publication No. 2017 / 179162 (Patent Document 1) discloses an uninterruptible power supply including a converter that converts AC power from an AC power source into DC power and outputs it to a DC bus, an inverter that converts the DC power received from the DC bus into AC power and supplies it to a load, a first bidirectional chopper that transfers DC power between the DC bus and a storage battery, and a second bidirectional chopper that transfers DC power between the DC bus and a lithium-ion battery.

[0003] In this uninterruptible power supply, the storage battery is used as a battery that stores DC power to be used when the AC power supply fails. The lithium-ion battery is used as a battery that is charged and discharged each time the load switches between powering and regenerative operation. When the AC power supply is healthy, the first bidirectional chopper is controlled to charge the storage battery, and when the AC power supply fails, the first bidirectional chopper is controlled to discharge the storage battery. When the load is in regenerative operation, the lithium-ion battery is charged, and when the load is in powering operation, the second bidirectional chopper is controlled to discharge the lithium-ion battery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 179162 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, regenerative power generated by the load can be stored in a lithium-ion battery, so that in the event of a power outage in the AC power supply, an increase in the voltage of the DC bus can be suppressed without returning the regenerative power to the AC power supply. In addition, when the load is in power running mode, the regenerative power can be effectively utilized by discharging the lithium-ion battery.

[0006] However, in Patent Document 1, it is necessary to prepare a battery (storage battery) for compensating for a power outage and a battery (lithium ion battery) for recovering regenerative power. In addition, it is necessary to provide two bidirectional choppers corresponding to these two batteries, respectively. This raises concerns that the uninterruptible power supply will become larger, heavier, and more costly. In addition, there is a concern that the control of the uninterruptible power supply according to the state of the AC power supply and the operating state of the load will become complicated.

[0007] The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide an uninterruptible power supply device that has a simple configuration and is capable of suppressing an increase in the voltage of the DC bus without returning the regenerative power generated in the load to the AC power source. [Means for solving the problem]

[0008] An uninterruptible power supply according to an embodiment of the present disclosure is connected between an AC power supply and a load. The uninterruptible power supply includes a converter, a bidirectional chopper, an inverter, and a control device. The converter converts AC power from the AC power supply into DC power and outputs the DC power to a DC bus. The bidirectional chopper selectively performs a charging operation for storing the DC power received from the DC bus in a power storage device and a discharging operation for outputting the DC power of the power storage device to the DC bus. The inverter converts the DC power received from the DC bus into AC power and supplies the AC power to the load, and converts regenerative power generated by the load into DC power and outputs the DC power to the DC bus. The control device controls the bidirectional chopper based on the SOC of the power storage device. The power storage device is set with an SOC reference value that is smaller than an upper limit value of a usable range of the SOC and larger than a lower limit value of the usable range. When the AC power supply is healthy, the control device controls the bidirectional chopper so that the SOC of the power storage device becomes the SOC reference value. When the AC power supply is interrupted, the control device controls the discharging operation in response to the powering operation of the load, and controls the charging operation in response to the regenerative operation of the load, based on the usable range. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide an uninterruptible power supply device that is capable of suppressing an increase in the voltage of a DC bus with a simple configuration without returning regenerative power generated in a load to an AC power source. [Brief description of the drawings]

[0010] [Figure 1] 1 is a circuit block diagram showing a configuration example of an uninterruptible power supply device according to an embodiment. [Diagram 2] FIG. 2 is a block diagram showing an example of a hardware configuration of a control device. [Diagram 3] 2 is a block diagram showing a configuration of a portion of the control device related to the control of the bidirectional chopper; FIG. [Figure 4] FIG. 11 is a diagram showing the relationship between the SOC of a battery and a reference voltage VBR. [Diagram 5] 1 is a diagram illustrating the operation of an uninterruptible power supply when the commercial AC power supply is healthy and the load is in power running mode. FIG. [Figure 6] 1 is a diagram illustrating the operation of an uninterruptible power supply when the commercial AC power supply is healthy and the load is in regenerative operation. FIG. [Figure 7] 1 is a diagram illustrating the operation of an uninterruptible power supply when a commercial AC power supply is interrupted and a load is in power running mode. FIG. [Figure 8] 1 is a diagram illustrating the operation of an uninterruptible power supply when a commercial AC power supply is interrupted and a load is in regenerative operation. FIG. [Figure 9] 1 is a diagram illustrating the operation of an uninterruptible power supply when the commercial AC power supply is restored and the load is in regenerative operation. FIG. [Figure 10] 4 is a flowchart for explaining control of the bidirectional chopper by the control device. [Figure 11] 4 is a flowchart for explaining control of the bidirectional chopper by the control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and their description will not be repeated in principle.

[0012] 1 is a circuit block diagram showing an example of the configuration of an uninterruptible power supply according to the present embodiment. As shown in FIG. 1, an uninterruptible power supply 100 is connected between a commercial AC power supply 6 and a load 8.

[0013] The load 8 is configured to perform a powering operation in which it is driven by AC power supplied from the uninterruptible power supply 100, and a regenerative operation in which it generates regenerative power (AC power). The load 8 is configured to include, for example, a motor. When power is supplied to the motor, such as when accelerating the motor, the load 8 performs a powering operation. On the other hand, when the motor is driven to rotate and operates as a generator, such as when decelerating the motor, the load 8 performs a regenerative operation. The regenerative power generated by the load 8 is supplied to the uninterruptible power supply 100.

[0014] As shown in FIG. 1, the uninterruptible power supply 100 includes an input terminal T1, a DC terminal T2, an output terminal T3, a converter 1, current detectors CD1-CD3, DC lines L1, L2, a capacitor C1, a bidirectional chopper 2, an inverter 3, an operation unit 4, and a control device 5.

[0015] Input terminal T1 receives AC voltage VI from a commercial AC power supply 6. The instantaneous value of AC voltage VI is detected by control device 5. The presence or absence of a power outage is determined based on the instantaneous value of AC voltage VI.

[0016] The DC terminal T2 is connected to a battery 7 (power storage device). The battery 7 stores DC power. For example, a lithium ion battery is used as the battery 7. The instantaneous value of the DC voltage VB at the DC terminal T2 (i.e., the terminal voltage VB of the battery 7) is detected by the control device 5.

[0017] The output terminal T3 is connected to a load 8. The load 8 is driven by AC power supplied from the uninterruptible power supply 100. The instantaneous value of the AC voltage VO appearing at the output terminal T3 is detected by the control device 5.

[0018] Although the uninterruptible power supply 100 receives a three-phase AC voltage from a commercial AC power supply 6 and supplies the three-phase AC voltage to a load 8, for the sake of simplicity of the drawings and explanation, FIG. 1 shows only a circuit for one phase.

[0019] The converter 1 has an AC terminal 1a, a positive voltage terminal 1b, and a negative voltage terminal 1c. The bidirectional chopper 2 has a DC terminal 2a, a positive voltage terminal 2b, and a negative voltage terminal 2c. The inverter 3 has an AC terminal 3a, a positive voltage terminal 3b, and a negative voltage terminal 3c.

[0020] The AC terminal 1a of the converter 1 is connected to the input terminal T1. The current detector CD1 detects the instantaneous value of a current Ii flowing between the input terminal T1 and the AC terminal 1a, and provides the control device 5 with a signal Iif indicative of the detected value.

[0021] The DC terminal 2a of the bidirectional chopper 2 is connected to the DC terminal T2. The current detector CD2 detects an instantaneous value of a DC current IB flowing between the DC terminal T2 and the DC terminal 2a, and provides the control device 5 with a signal IBf indicating the detected value.

[0022] The AC terminal 3a of the inverter 3 is connected to the output terminal T3. The current detector CD3 detects an instantaneous value of a current Io flowing between the AC terminal 3a and the output terminal T3, and provides the control device 5 with a signal Iof indicating the detected value.

[0023] One terminal of each of the DC lines L1 and L2 is connected to a positive voltage terminal 1b and a negative voltage terminal 1c of the converter 1, respectively. The other terminal of each of the DC lines L1 and L2 is connected to a positive voltage terminal 3b and a negative voltage terminal 3c of the inverter 3, respectively. Furthermore, the DC lines L1 and L2 are connected to a positive voltage terminal 2a and a negative voltage terminal 2c of the bidirectional chopper 2, respectively. The DC lines L1 and L2 correspond to an example of a "DC bus".

[0024] The capacitor C1 is connected between the DC lines L1 and L2, and stabilizes and smoothes the DC voltage VD between the DC lines L1 and L2. The instantaneous value of the DC voltage VD is detected by the control device 5.

[0025] The converter 1 is controlled by the control device 5, and when the AC voltage VI is being supplied normally from the commercial AC power supply 6 (i.e., when the commercial AC power supply 6 is normal) and the load 8 is in power running, the converter 1 converts the AC voltage VI supplied from the commercial AC power supply 6 via the input terminal T1 into a DC voltage VD and outputs it between the DC lines L1 and L2. When the AC voltage VI is not being supplied normally from the commercial AC power supply 6 (i.e., when the commercial AC power supply 6 is experiencing a power outage), the operation of the converter 1 is stopped.

[0026] When the commercial AC power supply 6 is healthy, the control device 5 controls the converter 1 so that the DC voltage VD between the DC lines L1 and L2 becomes the reference voltage VDR. When the commercial AC power supply 6 experiences a power outage, the control device 5 stops the operation of the converter 1.

[0027] The bidirectional chopper 2 is controlled by the control device 5. When the commercial AC power supply 6 is normal, the bidirectional chopper 2 stores the DC power supplied from the converter 1 through the DC lines L1 and L2 in the battery 7. When the commercial AC power supply 6 is out of power and the load 8 is in power running, the bidirectional chopper 2 converts the DC voltage VB of the battery 7 into a DC voltage VD and outputs it between the positive voltage terminal 2b and the negative voltage terminal 2c. When the commercial AC power supply 6 is out of power and the load 8 is in regenerative running, the bidirectional chopper 2 stores the DC power regenerated from the inverter 3 through the DC lines L1 and L2 in the battery 7. The bidirectional chopper 2 is configured to be capable of selectively performing a charging operation for storing DC power in the battery 7 and a discharging operation for outputting the DC power of the battery 7 between the DC lines L1 and L2.

[0028] When the commercial AC power supply 6 is healthy, the control device 5 controls the bidirectional chopper 2 so that the DC voltage VB becomes the reference voltage VBR. When the commercial AC power supply 6 is in a power failure state and the load 8 is in a power running state, the control device 5 controls the bidirectional chopper 2 so that the DC voltage VD becomes the reference voltage VDR. When the commercial AC power supply 6 is in a power failure state and the load 8 is in a regenerative running state, the control device 5 controls the bidirectional chopper 2 so that the DC voltage VB becomes the reference voltage VBR.

[0029] The inverter 3 is controlled by the control device 5. When the commercial AC power supply 6 is normal and the load 8 is in power running, the inverter 3 converts the DC voltage VD supplied from the converter 1 via the DC lines L1, L2 into an AC voltage VO and supplies it to the load 8. When the commercial AC power supply 6 is normal and the load 8 is in regenerative running, the inverter 3 converts the AC voltage VO supplied from the load 8 via the output terminal T3 into a DC voltage VD and outputs it between the DC lines L1, L2.

[0030] When the commercial AC power supply 6 is in a power failure state and the load 8 is in a power running state, the inverter 3 converts the DC voltage VD supplied from the battery 7 via the bidirectional chopper 2 and the DC lines L1, L2 into an AC voltage VO and supplies the AC voltage VO to the load 8. The output voltage VO of the inverter 3 can be controlled to a desired value. The control device 5 controls the inverter 3 so that the AC output voltage VO becomes a sinusoidal reference voltage VOR. When the commercial AC power supply 6 is in a power failure state and the load 8 is in a regenerative running state, the inverter 3 converts the AC voltage VO supplied from the load 8 via the output terminal T3 into a DC voltage VD and outputs the DC voltage between the DC lines L1, L2.

[0031] The operation unit 4 includes a plurality of buttons operated by a user of the uninterruptible power supply, an image display unit that displays various information, etc. By operating the operation unit 4, the user can turn the power of the uninterruptible power supply on and off and set various information.

[0032] The control device 5 controls the entire uninterruptible power supply based on the AC voltage VI, AC current Ii, DC voltages VD, VB, DC current IB, AC voltage VO, AC current Io, signals from the operation unit 4, and the like.

[0033] 2 is a block diagram showing an example of a hardware configuration of the control device 5. Typically, the control device 5 can be configured by a microcomputer in which a predetermined program is stored in advance.

[0034] 2, the control device 5 includes a CPU (Central Processing Unit) 10, a memory 12, and an input / output (I / O) circuit 14. The CPU 10, the memory 12, and the I / O circuit 14 can exchange data with each other via a bus 16. A program is stored in a partial area of ​​the memory 12, and the CPU 10 executes the program to realize various functions described below. The I / O circuit 14 inputs and outputs signals and data between the outside of the control device 5.

[0035] 2, at least a part of the control device 5 can be configured using a circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Also, at least a part of the control device 5 can be configured using an analog circuit.

[0036] Fig. 3 is a block diagram showing the configuration of a portion of the control device 5 related to the control of the bidirectional chopper 2. As shown in Fig. 3, the control device 5 includes a SOC (State Of Charge) calculation unit 20, a power failure detector 22, a charge control unit 24, a discharge control unit 26, a load determination unit 28, and a control unit 30. The function of each block shown in Fig. 3 can be realized by at least one of software processing and hardware processing by the control device 5.

[0037] The SOC calculation unit 20 calculates the SOC of the battery 7 using the detected value of the DC voltage VB (terminal voltage VB of the battery 7) and / or the detected value of the DC current IB. The SOC of the battery 7 is a value indicating the amount of charge stored in the battery 7, and is, for example, expressed as a percentage of the current amount of charge relative to the fully charged capacity of the battery 7. The SOC can be calculated using any known method, such as a method using an integrated value of the DC current IBT or a method using an OCV-SOC curve that indicates the relationship between the open circuit voltage (OCV) of the battery 7 and the SOC. A signal SOCf indicating the calculated SOC value is provided to the control unit 30.

[0038] The power failure detector 22 detects whether a power failure of the commercial AC power supply 6 has occurred based on the detected value of the AC voltage VI, and outputs a signal DF indicating the detection result. Specifically, when the AC voltage VI is within a preset normal range, the power failure detector 22 determines that the commercial AC power supply 6 is sound and outputs an L-level signal DF. When the AC voltage VI is lower than the normal range, the power failure detector 22 determines that a power failure of the commercial AC power supply 6 has occurred and outputs an H-level signal DF. The output signal DF of the power failure detector 22 is supplied to the charge control unit 24 and the control unit 30.

[0039] The charge control unit 24 generates a reference voltage VBR that is the target voltage of the DC voltage VB (the voltage VB between the terminals of the battery 7). Specifically, the charge control unit 24 generates the reference voltage VBR using the output signal DF of the power failure detector 22 and the OCV-SOC curve of the battery 7. FIG. 4 is a diagram showing the relationship between the SOC of the battery 7 and the reference voltage VBR.

[0040] As shown in FIG. 4, determination values SOCmin, SOCnormal, and SOCmax, which serve as guidelines for controlling the charging and discharging of the battery 7, are set for the SOC of the battery 7. SOC = 0% corresponds to the empty state of the battery 7, and SOC = 100% corresponds to the fully charged state of the battery 7.

[0041] For the SOC, a prohibited region for prohibiting the charging of the battery 7 to prevent overcharging and a prohibited region for prohibiting the discharging of the battery 7 to prevent overdischarging are set. The usable range of the SOC has an upper limit value SOCmax and a lower limit value SOCmin set based on these prohibited regions. When SOC > SOCmax, the charging of the battery 7 is prohibited, and when SOC < SOCmin, the discharging of the battery 7 is prohibited.

[0042] SOCnormal is a determination value used for controlling the charging and discharging of the battery 7 when the commercial AC power supply 6 is healthy. SOCnormal is set to be greater than SOCmin and less than SOCmax. When the commercial AC power supply 6 is healthy, when SOC > SOCnormal, the charging of the battery 7 is stopped, and when SOC < SOCnormal, the discharging of the battery 7 is stopped. That is, when the commercial AC power supply 6 is healthy, the charging and discharging of the battery 7 are controlled so that SOC maintains SOCnormal. SOCnormal corresponds to an embodiment of the "SOC reference value".

[0043] SOCnormal is set to be equal to or greater than SOCbackup. SOCbackup is the SOC for ensuring the function (power outage compensation function) as a backup power supply of the commercial AC power supply 6 when a power outage occurs in the uninterruptible power supply device 100. SOCbackup corresponds to the power storage amount for power outage compensation. The power storage amount for power outage compensation is the power storage amount required to continuously supply power from the battery 7 to the load 8 for a predetermined compensation time when a power outage occurs in the commercial AC power supply 6. Therefore, in order to ensure the power outage compensation function, it is necessary to maintain SOC at or above SOCbackup when the commercial AC power supply 6 is healthy.

[0044] As shown in FIG. 4, by setting SOCnormal ≧ SOCbackup, the power outage compensation function of the uninterruptible power supply device 100 can be ensured. On the other hand, if SOCnormal is set to a value close to SOCmax, when a power outage occurs in the commercial AC power supply 6 and the load 8 performs a regenerative operation, there is a possibility that the uninterruptible power supply device 100 cannot recover the regenerative power generated by the load 8.

[0045] In detail, when the commercial AC power supply 6 is interrupted, the regenerative power outputted from the inverter 3 between the DC lines L1 and L2 cannot be supplied to the commercial AC power supply 6 via the converter 1. Therefore, the regenerative power is stored in the capacitor C1 connected between the DC lines L1 and L2, and the DC voltage VD rises. In order to prevent the capacitor C1 from being overvoltage and causing a breakdown, a method of providing a resistor that converts the regenerative current into heat has been adopted in conventional uninterruptible power supplies. However, this method raises concerns that the regenerative power may be wasted.

[0046] In the uninterruptible power supply 100 according to this embodiment, when the commercial AC power supply 6 is out of power and the load 8 is in regenerative operation, the bidirectional chopper 2 stores the DC power regenerated between the DC lines L1 and L2 from the inverter 3 in the battery 7. This makes it possible to suppress an increase in the DC voltage VD. In addition, it becomes possible to effectively utilize the regenerative power.

[0047] However, if the SOC of the battery 7 is close to SOCmax during regenerative operation of the load 8, the battery 7 may not be able to recover the DC power regenerated from the load 8, which may result in an increase in the DC voltage VD.

[0048] As a countermeasure against this, the SOCnormal is set based on the maximum value Wmax of the amount of regenerative power generated in the load 8. The maximum value Wmax of the amount of regenerative power is the maximum amount of power that is estimated to be regenerated when the load 8 is in regenerative operation. Data for the maximum value Wmax of the amount of regenerative power can be obtained in advance by experiments or simulations, and stored in the memory 12 of the control device 5.

[0049] SOCnormal is set such that SOCnormal, Wmax, and SOCmax satisfy the relation SOCnormal + Wmax ≤ SOCmax. This relation is intended to ensure that even when the load 8 operates only in regenerative operation during a power outage of the commercial AC power supply 6, the SOC of the battery 7 does not exceed SOCmax due to the DC power regenerated from the load 8, that is, charging of the battery 7 is not prohibited. In the example of FIG. 4, the power storage amount corresponding to the difference between SOCmax and SOCnormal corresponds to the maximum value Wmax of the regenerative power amount.

[0050] As described above, SOCnormal is set to satisfy the relation SOCmin < SOCbackup ≤ SOCnormal + Wmax ≤ SOCmax among SOCmin, SOCbackup, SOCmax, and Wmax. In other words, a battery having a battery capacity that can satisfy this relation is applied to the battery 7. When the commercial AC power supply 6 is normal, since the battery 7 is not charged up to the upper limit value SOCmax of the available range of SOC, the progress of deterioration of the battery 7 can be suppressed. Therefore, the life of the battery 7 can be extended.

[0051] The charge control unit 24 has two voltages VB1 and VB2 as the reference voltage VBR. The voltage VB1 is set based on the OCV when SOC is SOCnormal in the OCV - SOC curve of the battery 7. The voltage VB2 is set based on the OCV when SOC is SOCmax in the OCV - SOC curve of the battery 7. When the output signal DF of the power outage detector 22 is at the L level, that is, when the commercial AC power supply 6 is normal, the charge control unit 24 sets the reference voltage VBR to VB1. When the output signal DF of the power outage detector 22 is at the H level, that is, when the commercial AC power supply 6 is out of power, the charge control unit 24 sets the reference voltage VBR to VB2.

[0052] 3, the discharge control unit 26 generates a reference voltage VDR which is a target voltage of the DC voltage VDC between the DC lines L1 and L2. For example, the discharge control unit 26 generates the reference voltage VDR based on a signal from the operation unit 4 or the like.

[0053] The load determination unit 28 determines whether the load 8 is in power running or regenerative operation based on the detection value of the AC current Io by the current detector CD3. The load determination unit 28, for example, performs a three-phase-two-phase conversion (e.g., dq conversion) on the three-phase AC current Io obtained from the output signal Iof of the current detector CD3 to obtain an active current and a reactive current. The load determination unit 28 determines that the load 8 is in power running when the active current has a positive value (i.e., when the active current flows from the inverter 3 to the load 8). The load determination unit 28 determines that the load 8 is in regenerative operation when the active current has a negative value (i.e., when the active current flows from the load 8 to the inverter 3). The load determination unit 28 outputs a signal DL indicating the determination result. When the load 8 is in power running, the signal DL is set to H level. When the load 8 is in regenerative operation, the signal DL is set to L level.

[0054] The control unit 30 controls the bidirectional chopper 2 based on the signal SOCf from the SOC calculation unit 20, the signal DF from the power failure detector 22, the reference voltage VBR from the charge control unit 24, the reference voltage VDR from the discharge control unit 26, the signal DL from the load determination unit 28, and the DC voltages VB, VD, etc.

[0055] When the signal DF is at L level and the signal DL is at H level (when the commercial AC power supply 6 is healthy and the load 8 is in power running), the control unit 30 controls the bidirectional chopper 2 so that the DC voltage VB (the terminal voltage VB of the battery 7) becomes the reference voltage VBR. The reference voltage VBR=VB1.

[0056] When the signal DF is at L level and the signal DL is at L level (when the commercial AC power supply 6 is healthy and the load 8 is in regenerative operation), the control unit 30 controls the bidirectional chopper 2 so that the DC voltage VB becomes the reference voltage VBR. The reference voltage VBR=VB1.

[0057] When the signal DF is at H level and the signal DL is at H level (when the commercial AC power supply 6 is at a power outage and the load 8 is in power running operation), the control unit 30 controls the bidirectional chopper 2 so that the DC voltage VD becomes the reference voltage VDR.

[0058] When the signal DF is at H level and the signal DL is at L level (when the commercial AC power supply 6 is in a power outage and the load 8 is in a regenerative operation), the control unit 30 controls the bidirectional chopper 2 so that the DC voltage VB becomes the reference voltage VBR. The reference voltage VBR=VB2.

[0059] Next, the operation of the uninterruptible power supply 100 will be described. 5 is a diagram illustrating the operation of the uninterruptible power supply 100 when the commercial AC power supply 6 is healthy and the load 8 is in power running mode. The arrows in the diagram indicate the flow of power exchanged between the commercial AC power supply 6, the load 8, and the battery 7.

[0060] 5, the converter 1 converts AC power supplied from a commercial AC power supply 6 into DC power and outputs it between DC lines L1 and L2. The inverter 3 converts the DC power supplied from the converter 1 via the DC lines L1 and L2 into AC power and supplies it to a load 8.

[0061] The bidirectional chopper 2 stores the DC power supplied from the converter 1 via the DC lines L1 and L2 in the battery 7. The control device 5 controls the bidirectional chopper 2 so that the DC voltage VB of the battery 7 becomes the reference voltage VBR (= VB1). Thereby, the battery 7 is charged so that the SOC of the battery 7 becomes SOCnormal. When SOC > SOCnormal, the control device 5 stops the charging of the battery 7 by stopping the bidirectional chopper 2.

[0062] FIG. 6 is a diagram for explaining the operation of the uninterruptible power supply device 100 when the commercial AC power supply 6 is normal and the load 8 is operating in regenerative operation.

[0063] As shown in FIG. 6, the inverter 3 converts the regenerative power (AC power) generated in the load 8 into DC power and outputs it between the DC lines L1 and L2. The converter 1 converts the DC power regenerated from the load 8 to the DC lines L1 and L2 into AC power and supplies it to the commercial AC power supply 6. In the example of FIG. 6, since SOC = SOCnormal, the bidirectional chopper 2 is stopped. However, when SOC < SOCnormal, the bidirectional chopper 2 can store the DC power regenerated from the load 8 in the battery 7. In this case, the control device 5 controls the bidirectional chopper 2 so that the DC voltage VB of the battery 7 becomes the reference voltage VBR (= VB1). When SOC > SOCnormal, the control device 5 stops the charging of the battery 7 by stopping the bidirectional chopper 2.

[0064] FIG. 7 is a diagram for explaining the operation of the uninterruptible power supply device 100 when the commercial AC power supply 6 is out of power and the load 8 is operating in power running. When a power outage of the commercial AC power supply 6 occurs, an electromagnetic contactor (not shown) provided between the input terminal T1 and the AC terminal 1a of the converter 1 is turned off, thereby disconnecting the commercial AC power supply 6 from the uninterruptible power supply device 100. The operation of the converter 1 is stopped.

[0065] As shown in Fig. 7, when the load 8 is in motoring operation, the bidirectional chopper 2 supplies the DC power of the battery 7 to the inverter 3 via the DC lines L1 and L2. The inverter 3 converts the DC power supplied from the battery 7 via the DC lines L1 and L2 into AC power and supplies it to the load 8.

[0066] The control device 5 controls the bidirectional chopper 2 so that the DC voltage VD becomes the reference voltage VDR. When the SOC of the battery 7 decreases and becomes SOC < SOCmin, the control device 5 stops the bidirectional chopper 2 to stop the discharge of the battery 7.

[0067] Fig. 8 is a diagram for explaining the operation of the uninterruptible power supply 100 when there is a power outage in the commercial AC power supply 6 and the load 8 is in regenerative operation. Similar to Fig. 7, the uninterruptible power supply 100 is disconnected from the commercial AC power supply 6, and the operation of the converter 1 is stopped.

[0068] As shown in Fig. 8, the inverter 3 converts the regenerative power (AC power) generated in the load 8 into DC power and outputs it between the DC lines L1 and L2. The bidirectional chopper 2 stores the DC power regenerated from the load 8 into the DC lines L1 and L2 in the battery 7. The control device 5 controls the bidirectional chopper 2 so that the DC voltage VB of the battery 7 becomes the reference voltage VBR (= VB2). Thereby, the battery 7 is charged until the SOC of the battery 7 reaches SOCmax. When SOC > SOCmax, the control device 5 stops the bidirectional chopper 2 to stop the charging of the battery 7.

[0069] FIG. 9 is a diagram for explaining the operation of the uninterruptible power supply device 100 when the commercial AC power supply 6 is restored and the load 8 is in regenerative operation. As shown in FIG. 8, there are cases where SOC>SOCnormal when the commercial AC power supply 6 is restored by storing regenerative power generated by the load 8 in the battery 7 during a power outage of the commercial AC power supply 6. In such a case, as shown in FIG. 9, the bidirectional chopper 2 can lower the SOC to SOCnormal by outputting the DC power of the battery 7 between the DC lines L1 and L2 during the regenerative operation of the load 8. The converter 1 converts the DC power supplied from the inverter 3 and the battery 7 to the DC lines L1 and L2 into AC power and supplies it to the commercial AC power supply 6. This allows the regenerative power to be effectively utilized.

[0070] The control device 5 controls the bidirectional chopper 2 so that the DC voltage VD becomes the reference voltage VDR. When the SOC of the battery 7 decreases and becomes SOC≦SOCmin, the control device 5 stops the bidirectional chopper 2, thereby stopping the discharge of the battery 7.

[0071] Figures 10 and 11 are flowcharts for explaining the control of the bidirectional chopper 2 by the control device 5. The flowcharts in Figures 10 and 11 are repeatedly executed by the control device 5 when the uninterruptible power supply 100 is in operation.

[0072] 10, the control device 5 determines whether or not a power outage has occurred in the commercial AC power source 6 based on the detected value of the AC voltage VI in step (hereinafter simply referred to as "S") 01. If the AC voltage VI is within the normal range, a NO determination is made in S01, and if the AC input voltage VI is lower than the normal range, a YES determination is made in S01.

[0073] If the commercial AC power supply 6 is healthy (NO in S01), the control device 5 proceeds to S02 and determines whether the load 8 is in power running or regenerative operation based on the detection value of the AC current Io by the current detector CD3. If the active current calculated from the AC current Io is a positive value, YES is determined in S02, and if the active current is a negative value, NO is determined in S02.

[0074] When the load 8 is in power running (YES in S02), the control device 5 controls the converter 1 and the inverter 3 in S03 so that AC power supplied from the commercial AC power supply 6 is supplied to the load 8 (see FIG. 5).

[0075] During powering operation of the load 8, the control device 5 compares the SOC of the battery 7 with SOCnormal in S04. If SOC≦SOCnormal (YES in S04), the control device 5 proceeds to S05 and controls the bidirectional chopper 2 so as to store the DC power supplied from the converter 1 via the DC lines L1 and L2 in the battery 7. In S05, the control device 5 sets the reference voltage VBR to VB1, and controls the bidirectional chopper 2 so that the DC voltage VB becomes the reference voltage VBR. If SOC>SOCnormal (NO in S04), the control device 5 stops charging of the battery 7 by stopping the bidirectional chopper 2 in S06.

[0076] Returning to S02, when the load 8 is in regenerative operation (when the determination in S02 is NO), the control device 5 controls the converter 1 and the inverter 3 in S07 so that the regenerative power generated by the load 8 is supplied to the commercial AC power supply 6 (see FIG. 6).

[0077] During the regenerative operation of the load 8, the control device 5 compares the SOC of the battery 7 with SOCnormal in S08. If SOC>SOCnormal (YES in S08), the control device 5 proceeds to S09 and controls the bidirectional chopper 2 so as to output the DC power of the battery 7 to the DC lines L1 and L2 (see FIG. 9). In S09, the control device 5 controls the bidirectional chopper 2 so that the DC voltage VD becomes the reference voltage VDR. If SOC≦SOCnormal (NO in S08), the control device 5 stops discharging the battery 7 by stopping the bidirectional chopper 2 in S10.

[0078] Returning to S01, if a power outage has occurred in the commercial AC power supply 6 (YES determination in S01), the control device 5 proceeds to S11 and turns off the electromagnetic contactor provided between the input terminal T1 and the AC terminal 1a of the converter 1, thereby disconnecting the uninterruptible power supply 100 from the commercial AC power supply 6.

[0079] Next, the control device 5 proceeds to S12, where it determines whether the load 8 is in a power running operation or a regenerative operation, based on the value of the AC current Io detected by the current detector CD3.

[0080] When the load 8 is in power running (YES in S12), the control device 5 controls the bidirectional chopper 2 and the inverter 3 in S13 so that the DC power of the battery 7 is supplied to the load 8 (see FIG. 7).

[0081] During powering operation of the load 8, the control device 5 compares the SOC of the battery 7 with SOCmin in S14. If SOC>SOCmin (YES in S14), the control device 5 proceeds to S15 and controls the bidirectional chopper 2 to output the DC power of the battery 7 to the DC lines L1 and L2. In S15, the control device 5 controls the bidirectional chopper 2 so that the DC voltage VD becomes the reference voltage VDR. If SOC≦SOCmin (NO in S16), the control device 5 stops the bidirectional chopper 2 in S16 to stop discharging the battery 7.

[0082] Returning to S12, when the load 8 is in regenerative operation (when the determination at S12 is YES), the control device 5 compares the SOC of the battery 7 with SOCmax at S17. If SOC < SOCmax (when the determination at S17 is YES), the control device 5 proceeds to S18 and controls the bidirectional chopper 2 so as to store the DC power regenerated from the inverter 3 via the DC lines L1 and L2 in the battery 7 (see FIG. 8). At S17, the control device 5 sets the reference voltage VBR to VB2 and controls the bidirectional chopper 2 so that the DC voltage VB becomes the reference voltage VBR. If SOC ≧ SOCmax (when the determination at S17 is NO), at S19, the charging of the battery 7 is stopped by stopping the bidirectional chopper 2.

[0083] As described above, in the uninterruptible power supply device 100 according to the present embodiment, when the commercial AC power supply 6 is healthy, the bidirectional chopper 2 is controlled so that the SOC of the battery 7 becomes SOCnormal (SOC reference value) that is smaller than the upper limit value SOCmax of the usable range of SOC and larger than the lower limit value SOCmin. According to this, when the load 8 is in regenerative operation during a power failure of the commercial AC power supply 6, the battery 7 can recover the regenerative power generated by the load 8 via the bidirectional chopper 2.

[0084] According to this, it is possible to suppress an increase in the DC voltage VD without returning the regenerative power to the commercial AC power supply 6. Further, when the load 8 switches from regenerative operation to power running operation, the regenerative power stored in the battery 7 can be supplied to the load 8, so that the regenerative power of the load 8 can be effectively utilized. Furthermore, since the battery 7 is not charged up to the upper limit value SOCmax of the usable range of SOC when the commercial AC power supply 6 is healthy, the progress of deterioration of the battery 7 can be suppressed. Therefore, it is possible to realize a long life of the battery 7.

[0085] In addition, in the above configuration, by setting the SOCnormal to be equal to or higher than the SOCbackup based on the power failure compensation storage amount, when the load 8 is powered during a power failure of the commercial AC power source 6, the load 8 can be driven for a predetermined compensation time using the DC power stored in the battery 7.

[0086] Furthermore, by setting SOCnormal to satisfy the relationship SOCnormal+Wmax (maximum amount of regenerative power)≦SOCmax, when the load 8 performs only regenerative operation during a power outage of the commercial AC power supply 6, it is possible to avoid a situation in which the SOC of the battery 7 exceeds SOCmax due to the regenerative power and charging of the battery 7 is prohibited. Therefore, it is possible to suppress an increase in the DC voltage VD due to a failure to recover the regenerative power.

[0087] In Patent Document 1, in addition to the storage battery for power failure compensation, a lithium ion battery for recovering regenerative power is used, so two batteries and two bidirectional choppers are required, which leads to an increase in size, weight, and cost of the uninterruptible power supply. In addition, there is a concern that the control of the uninterruptible power supply will become complicated. In this embodiment, one battery 7 can be used for both power failure compensation and recovery of regenerative power, so that such concerns can be resolved.

[0088] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The technical scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0089] 1 converter, 2 bidirectional chopper, 3 inverter, 4 operation unit, 5 control device, 6 commercial AC power supply, 7 battery, 8 load, 10 CPU, 12 memory, 14 I / O device, 16 bus, 20 SOC calculation unit, 22 power failure detector, 24 charge control unit, 26 discharge control unit, 28 load judgment unit, 30 control unit, 100 uninterruptible power supply, C1 capacitor, CD1 to CD3 current detectors, L1, L2 DC lines.

Claims

1. An uninterruptible power supply connected between an AC power source and a load, a converter that converts AC power from the AC power source into DC power and outputs the DC power to a DC bus; a bidirectional chopper that selectively performs a charging operation of storing DC power received from the DC bus in a power storage device and a discharging operation of outputting DC power from the power storage device to the DC bus; an inverter that converts DC power received from the DC bus into AC power and supplies the AC power to the load, and converts regenerative power generated by the load into DC power and outputs the DC power to the DC bus; a control device that controls the bidirectional chopper based on an SOC of the power storage device, an SOC reference value is set for the power storage device, the SOC reference value being smaller than an upper limit value of a usable range of the SOC and larger than a lower limit value of the usable range; When the AC power supply is healthy, the control device controls the bidirectional chopper so that the SOC of the power storage device becomes the SOC reference value; When the AC power supply is interrupted, the control device controls the discharging operation in response to a powering operation of the load based on the available range, and controls the charging operation in response to a regenerative operation of the load, When the AC power supply is in a healthy state, the converter converts DC power received from the DC bus into AC power in response to a regenerative operation of the load and supplies the AC power to the AC power supply; When the SOC of the power storage device is greater than the SOC reference value, the control device controls the discharge operation in response to regenerative operation of the load so that the SOC of the power storage device becomes the SOC reference value.

2. 2. The uninterruptible power supply according to claim 1, wherein the SOC reference value is set to be equal to or greater than an SOC required for supplying power from the storage device to the load until a predetermined compensation time has elapsed since a power outage occurred in the AC power supply.

3. 3. The uninterruptible power supply according to claim 2, wherein the SOC reference value is set so that a value obtained by adding a maximum value of the amount of regenerative power generated by the load to the SOC reference value is equal to or less than the upper limit value.

4. When the AC power supply is healthy, the control device stops the charging operation when the SOC of the power storage device exceeds the SOC reference value; 4 . The uninterruptible power supply device according to claim 1 , wherein, in the event of a power outage of the AC power supply, the control device stops the charging operation when an SOC of the power storage device exceeds the upper limit value.

5. When the AC power supply is healthy, the control device stops the discharging operation when the SOC of the power storage device becomes less than the SOC reference value, 4 . The uninterruptible power supply device according to claim 1 , wherein, in the event of a power outage of the AC power supply, the control device stops the discharging operation when an SOC of the power storage device falls below the lower limit value.

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

Images