Uninterruptible power supply device

Abstract

The converter (10) converts AC power supplied from the AC power source (80) into DC power and outputs the DC power to the DC line (20). The inverter (40) converts DC power supplied from the DC line (20) into AC power and supplies the AC power to a load (84). A power storage device (82) is connected to the DC line (20). The converter (10) includes a plurality of converter units (12) connected in parallel. The inverter (40) includes a plurality of inverter units (42) connected in parallel. When the AC power source (80) is operating normally, the control device (50) determines an appropriate number of inverter units (42) to be operated based on the output current of the inverter (40). The control device (50) determines an appropriate number of converter units (12) to be operated based on the AC power supplied from the AC power source (80) to the converter (10). The control device (50) operates the determined appropriate number of inverter units (42) and converter units (12).

Description

[Technical Field]

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

[0002] For example, Japanese Patent Application Laid-Open Publication No. 2020-005410 (Patent Document 1) discloses an uninterruptible power supply system including multiple uninterruptible power supplies. The multiple uninterruptible power supplies are connected in parallel between an AC power source and a load. An appropriate number of operating units required to supply load current is determined, and the appropriate number of operating uninterruptible power supplies among the multiple uninterruptible power supplies are put into operation to supply the load current, while the remaining uninterruptible power supplies are put into standby mode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-005410 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, converters and inverters belonging to an uninterruptible power supply that has been put into operation are operated, and converters and inverters belonging to an uninterruptible power supply that has been put into a stopped state are stopped. That is, a number of inverters determined based on the load current and an equal number of converters are operated.

[0005] Therefore, when a load with a low power factor is connected to an uninterruptible power supply system, while each inverter can be operated at high operating efficiency, there is a possibility that the number of operating converters will be excessive compared to the AC power supplied from the AC power source (equivalent to the power consumption of the load).In this case, the operating efficiency of each converter will decrease, which raises concerns about a decrease in the power supply efficiency of the entire uninterruptible power supply system.

[0006] Therefore, a primary object of the present disclosure is to provide an uninterruptible power supply capable of improving power supply efficiency. [Means for solving the problem]

[0007] An uninterruptible power supply according to the present disclosure includes a converter that converts AC power supplied from an AC power source into DC power and outputs it to a DC line, an inverter that converts the DC power supplied from the DC line into AC power and supplies it to a load, and a control device that controls the converter and the inverter. A power storage device that stores DC power from the DC line is connected to the DC line. The converter includes a plurality of converter units connected in parallel between the AC power source and the DC line. The inverter includes a plurality of inverter units connected in parallel between the DC line and the load. When the AC power source is healthy, the control device determines an appropriate number of inverter units to operate based on the output current of the inverter. The control device determines an appropriate number of converter units to operate based on AC power supplied to the converter from the AC power source. The control device operates the determined appropriate number of inverter units and converter units to operate. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an uninterruptible power supply device that can improve power supply efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit block diagram showing a configuration of an uninterruptible power supply according to a first embodiment. [Figure 2] FIG. 2 is a block diagram illustrating an example of a hardware configuration of a control device. [Figure 3] 4 is a flowchart showing the flow of operation of the control device. [Figure 4] FIG. 2 is a block diagram showing the configuration of a portion of the control device that is related to inverter control. [Figure 5] FIG. 2 is a block diagram showing the configuration of a portion of the control device that is related to the control of the bidirectional chopper. [Figure 6] FIG. 2 is a block diagram showing the configuration of a portion of the control device that is related to the control of the converter. [Figure 7] FIG. 10 is a diagram illustrating an example of the operation of the uninterruptible power supply when the AC power supply is normal. [Figure 8] FIG. 1 is a diagram illustrating an example of the operation of an uninterruptible power supply during a power outage of an AC power supply. [Figure 9] FIG. 10 is a diagram illustrating an example of the operation of an uninterruptible power supply when AC power is restored. [Figure 10] FIG. 10 is a circuit block diagram showing a configuration of an uninterruptible power supply according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 will be denoted by the same reference numerals, and their description will not be repeated in principle.

[0011] [Embodiment 1] Fig. 1 is a circuit block diagram showing the configuration of an uninterruptible power supply according to a first embodiment. As shown in Fig. 1, uninterruptible power supply 100 includes an AC input terminal T1, a DC terminal T2, and an AC output terminal T3. AC input terminal T1 receives AC power of a predetermined frequency (for example, a commercial frequency) from an AC power supply 80. AC power supply 80 may be a commercial AC power supply or a generator.

[0012] DC terminal T2 is connected to battery 82. Battery 82 corresponds to an example of a "power storage device" that stores DC power. Battery 82 is a secondary battery such as a lead-acid battery, a nickel-metal hydride battery, or a lithium-ion battery. An electric double layer capacitor or a flywheel may be connected instead of battery 82.

[0013] The AC output terminal T3 is connected to the load 84. The load 84 is driven by AC power supplied from the uninterruptible power supply 100.

[0014] The uninterruptible power supply 100 further includes switches S1 to S3, a converter 10, current detectors CD1 to CD3, a DC line 20, capacitors C1, C2, and 22, reactors L1 and L2, a bidirectional chopper 30, an inverter 40, and a control device .

[0015] The switch S1 and the reactor L1 are connected in series between the AC input terminal T1 and the AC node of the converter 10. The switch S1 is controlled by the control device 50. When the AC power supply 80 is operating normally, the switch S1 is turned on, and AC power is supplied from the AC power supply 80 to the converter 10 via the switch S1. When the AC power supply 80 experiences a power outage, the switch S1 is turned off, and the AC power supply 80 and the converter 10 are disconnected.

[0016] The instantaneous value of the AC input voltage VI supplied from the AC power supply 80 is detected by the control device 50. Based on the instantaneous value of the AC input voltage VI, the control device 50 determines whether the AC voltage VI is being supplied normally from the AC power supply 80. The current detector CD1 detects the AC input current Ii flowing between the AC power supply 80 and the converter 10, and provides the control device 50 with a signal Iif indicating the detected value.

[0017] Capacitor C1 is connected to a node between switch S1 and reactor L1. Capacitor C1 and reactor L1 form AC filter F1. AC filter F1 is a low-pass filter that passes AC power of a predetermined frequency from AC power supply 80 to converter 10 and prevents signals of the switching frequency generated by converter 10 from passing to AC power supply 80.

[0018] The converter 10 is controlled by a control device 50. When the AC power supply 80 is operating normally, the converter 10 converts AC power received at an AC input terminal T1 into DC power and outputs the DC power to the DC line 20. The output voltage of the converter 10 can be controlled to a desired value. When the AC power supply 80 experiences a power outage, the operation of the converter 10 is stopped.

[0019] The converter 10 includes a plurality of converter units 12_1, 12_2, and 12_3 and a plurality of switches 11_1, 11_2, and 11_3. In the following description, the plurality of converter units 12_1, 12_2, and 12_3 may be collectively referred to as "converter units 12," and the plurality of switches 11_1, 11_2, and 11_3 may be collectively referred to as "switches 11." The number L of each of the converter units 12 and the switches 11 is not limited to 3, and may be any number.

[0020] The plurality of converter units 12_1, 12_2, 12_3 are connected in parallel between the AC node and the DC node of the converter 10. The converter units 12 are well known and include a plurality of semiconductor switching elements and a plurality of diodes, and are controlled by a control device 50. The converter units 12 convert AC power input from the AC node via the corresponding switches 11 into DC power and output it to the DC node.

[0021] A plurality of switches 11_1, 11_2, and 11_3 are provided corresponding to the plurality of converter units 12_1, 12_2, and 12_3, respectively. Each switch 11 is connected in series with a corresponding converter unit 12 between an AC node and a DC node of the converter 10. Each switch 11 is controlled by a control device 50, and is turned on when the corresponding converter unit 12 is to be put into an operating state, and is turned off when the corresponding converter unit 12 is to be put into a stopped state.

[0022] The capacitor 22 is connected to the DC line 20 and smooths the voltage of the DC line 20. The instantaneous value of the DC voltage VD appearing on the DC line 20 is detected by the control device 50.

[0023] The DC line 20 is connected to a high-voltage side node of the bidirectional chopper 30, and the low-voltage side node of the bidirectional chopper 30 is connected to a DC terminal T2 via a switch S2. The switch S2 is turned on when the uninterruptible power supply 100 is in use, and is turned off, for example, during maintenance of the uninterruptible power supply 100 and the battery 82.

[0024] The bidirectional chopper 30 is controlled by the control device 50, and exchanges DC power between the DC line 20 and the battery 82. When the AC power supply 80 is operating normally, the bidirectional chopper 30 stores the DC power supplied from the converter 10 via the DC line 20 in the battery 82. When the AC power supply 80 experiences a power outage, the bidirectional chopper 30 supplies the DC power of the battery 82 to the inverter 40 via the DC line 20.

[0025] The current detector CD2 detects a current IB (hereinafter also referred to as the "battery current") flowing between the bidirectional chopper 30 and the battery 82, and provides a signal IBf indicating the detected value to the control device 50. The instantaneous value of the voltage VB across the terminals of the battery 82 (hereinafter also referred to as the "battery voltage") appearing at the DC terminal T2 is detected by the control device 50.

[0026] The bidirectional chopper 30 includes a plurality of chopper units 32_1, 32_2, and 32_3 and a plurality of switches 31_1, 31_2, and 31_3. In the following description, the plurality of chopper units 32_1, 32_2, and 32_3 may be collectively referred to as "chopper units 32," and the plurality of switches 31_1, 31_2, and 31_3 may be collectively referred to as "switches 31." The number M of each of the chopper units 32 and the switches 31 is not limited to 3, and may be any number.

[0027] The plurality of chopper units 32_1, 32_2, 32_3 are connected in parallel between a high-voltage side node and a low-voltage side node of the bidirectional chopper 30. The chopper units 32 are well known and include a plurality of semiconductor switching elements and a plurality of diodes, and are controlled by the control device 50. When storing DC power in the battery 82, the chopper units 32 step down the DC voltage VD of the DC line 20 and provide it to the battery 82 via the corresponding switches 31. When supplying DC power from the battery 82 to the inverter 40, the chopper units 32 step up the battery voltage VB input via the corresponding switches 31 and output it to the DC line 20.

[0028] A plurality of switches 31_1, 31_2, 31_3 are provided corresponding to the plurality of chopper units 32_1, 32_2, 32_3, respectively. The switches 31 are connected in series with the corresponding chopper units 32 between the high-voltage side node and the low-voltage side node of the bidirectional chopper 30. The switches 31 are controlled by the control device 50, and are turned on when the corresponding chopper units 32 are to be put into an operating state, and are turned off when the corresponding chopper units 32 are to be stopped.

[0029] The DC line 20 is connected to a DC node of the inverter 40. The inverter 40 is controlled by a control device 50, and converts DC power supplied from the converter 10 or the bidirectional chopper 30 via the DC line 20 into AC power and outputs it to the AC node. That is, when the AC power supply 80 is operating normally, the inverter 40 converts the DC power supplied from the converter 10 via the DC line 20 into AC power, and when the AC power supply 80 is out of service, the inverter 40 converts the DC power supplied from the bidirectional chopper 30 via the DC line 20 into AC power. The output voltage of the inverter 40 can be controlled to a desired value.

[0030] The inverter 40 includes a plurality of inverter units 42_1, 42_2, and 42_3 and a plurality of switches 41_1, 41_2, and 41_3. In the following description, the plurality of inverter units 42_1, 42_2, and 42_3 may be collectively referred to as "inverter units 42," and the plurality of switches 41_1, 41_2, and 41_3 may be collectively referred to as "switches 41." The number N of each of the inverter units 42 and the switches 41 is not limited to 3, and may be any number.

[0031] The plurality of inverter units 42_1, 42_2, 42_3 are connected in parallel between a DC node and an AC node of the inverter 40. The inverter units 42 are well known units including a plurality of semiconductor switching elements and a plurality of diodes, and are controlled by the control device 50. The inverter units 42 convert DC power input from the DC node via the corresponding switches 41 into AC power and output it to the AC node.

[0032] A plurality of switches 41_1, 41_2, 41_3 are provided corresponding to the plurality of inverter units 42_1, 42_2, 42_3, respectively. The switches 41 are connected in series with the corresponding inverter units 42 between the DC node and the AC node of the inverter 40. The switches 41 are controlled by the control device 50, and are turned on when the corresponding inverter units 42 are to be put into an operating state, and are turned off when the corresponding inverter units 42 are to be put into a stopped state.

[0033] An AC node of the inverter 40 is connected to a first terminal of a switch S3 via a reactor L2, and a second terminal of the switch S3 is connected to an AC output terminal T3. A capacitor C2 is connected to the first terminal of the switch S3. The reactor L2 and the capacitor C2 form an AC filter F2. The AC filter F2 is a low-pass filter that passes AC power of a predetermined frequency generated by the inverter 40 to the AC output terminal T3 and prevents signals of a switching frequency generated by the inverter 40 from passing to the AC output terminal T3.

[0034] The switch S3 is controlled by the control device 50, and is turned on in an inverter power supply mode in which the AC power generated by the inverter 40 is supplied to the load 84, and is turned off in a bypass power supply mode in which the AC power from a bypass AC power supply (not shown) is supplied to the load 84.

[0035] The instantaneous value of the AC output voltage VO appearing at node N2 is detected by the control device 50. The current detector CD3 detects a current Io (hereinafter also referred to as a "load current") flowing between the inverter 40 and the AC output terminal T3, and provides the control device 50 with a signal Iof indicating the detected value.

[0036] The control device 50 controls the entire uninterruptible power supply 100 based on the AC input voltage VI, AC input current Ii, DC voltage VD, battery voltage VB, battery current IB, AC output voltage VO, and load current Io.

[0037] 2 is a block diagram showing an example of the hardware configuration of the control device 50. The control device 50 can be typically configured by a microcomputer in which a predetermined program is stored in advance.

[0038] 2, the control device 50 includes a CPU (Central Processing Unit) 52, a memory 54, and an input / output (I / O) circuit 56. The CPU 52, the memory 54, and the I / O circuit 56 can exchange data with one another via a bus 58. Programs are stored in a portion of the memory 54, and the CPU 52 executes these programs to realize various functions described below. The I / O circuit 56 exchanges signals and data with the outside of the control device 50.

[0039] The data provided from outside the control device 50 includes information about the number of power conversion units included in each of the power converters, i.e., the converter 10, the bidirectional chopper 30, and the inverter 40, and information about the rated output and operating efficiency of each of the power conversion units, i.e., the converter unit 12, the chopper unit 32, and the inverter unit 42. The acquired data is stored in a memory 54.

[0040] 2, at least a part of the control device 50 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 50 can be configured using an analog circuit.

[0041] Next, the operation of the uninterruptible power supply 100 will be described. 1, in the uninterruptible power supply 100, each of the power converters, namely, the converter 10, the bidirectional chopper 30, and the inverter 40, includes a plurality of power conversion units (converter unit 12, chopper unit 32, inverter unit 42) connected in parallel. The control device 50 is configured to individually control the number of operating power conversion units in each power converter according to the operating state of the uninterruptible power supply 100.

[0042] Fig. 3 is a flowchart showing the flow of the operation of the control device 50. The flowchart shown in Fig. 3 is repeatedly executed every time a predetermined condition is met (every predetermined period) while the uninterruptible power supply 100 is in operation.

[0043] 3, the control device 50 first detects whether a power outage has occurred in the AC power supply 80 (step S01). In S01, the control device 50 determines that a power outage has occurred in the AC power supply 80, for example, when the instantaneous value of the AC input voltage VI supplied from the AC power supply 80 falls below a lower limit value.

[0044] When the AC power supply 80 is healthy (NO in S01), the control device 50 determines the appropriate number of operating power conversion units in each power converter, namely, the converter 10, the bidirectional chopper 30, and the inverter 40 (steps S02 to S04).

[0045] Specifically, the control device 50 determines the appropriate number X of inverter units 42 to be operated for the inverter 40 (step S02). In S02, the control device 50 determines the appropriate number X of inverter units 42 to be operated based on the output current of the inverter 40 (i.e., the load current Io). X is an integer between 1 and N, inclusive, where N is the number of inverter units 42 included in the inverter 40 (total number of units). The control device 50 determines the appropriate number X of inverter units 42 to be operated so that the inverter units 42 operate at a load factor that provides high operating efficiency. A method for determining the appropriate number X of inverter units 42 to be operated will be described in detail later.

[0046] The control device 50 also determines the appropriate number Y of chopper units 32 to be operated for the bidirectional chopper 30 (step S03). In S03, the control device 50 determines the appropriate number Y of chopper units 32 to be operated based on the charging current required to charge the battery 82. Y is an integer between 0 and M, inclusive. M is the number of chopper units 32 included in the bidirectional chopper 30 (total number of units). The control device 50 determines the appropriate number Y of chopper units 32 to be operated so that the minimum number of chopper units 32 required to charge the battery 82 is operated. A method for determining the appropriate number Y of chopper units to be operated will be described in detail later.

[0047] Furthermore, the control device 50 determines an appropriate number Z of converter units 12 in operation for the converter 10 (step S04). In S04, the control device 50 determines the appropriate number Z of converter units 12 in operation based on the AC power supplied from the AC power source 80 to the converter 10. Z is an integer between 1 and L, inclusive. L is the number of converter units 12 included in the converter 10 (total number of units). The AC power supplied from the AC power source 80 to the converter 10 corresponds to the total power of the AC power consumed by the load 84 (power consumption of the load 84) and the AC power supplied to the battery 82 (charging power for the battery 82). The control device 50 determines the appropriate number Z of converter units 12 in operation so that the converter units 12 operate at a load factor that provides high operating efficiency. A method for determining the appropriate number Z of converter units in operation will be described in detail later.

[0048] Once the appropriate number of operating power conversion units in each power converter is determined, the control device 50 controls the operation of the converter 10, bidirectional chopper 30, and inverter 40 based on the determined appropriate number of operating units (step S05). In S05, the control device 50 operates the appropriate number of operating power conversion units among the multiple power conversion units in each power converter and turns on the corresponding switches. The control device 50 also stops the remaining power conversion units and turns off the corresponding switches.

[0049] Returning to step S01, if a power outage occurs in the AC power supply 80 (YES determination in S01), the control device 50 does not determine the appropriate number of operating units in steps S02 to S04. The control device 50 sets the appropriate number of operating inverter units 42 X for the inverter 40 to the total number of units N (step S06). That is, the control device 50 puts all of the multiple inverter units 42 into an operating state.

[0050] Furthermore, the control device 50 sets the appropriate number Y of chopper units 32 in operation to the total number M of units for the bidirectional chopper 30 (step S07). That is, the control device 50 puts all of the plurality of chopper units 32 into operation.

[0051] Meanwhile, the control device 50 sets the appropriate number Z of operating converter units 12 for the converter 10 to 0 (step S08). That is, the control device 50 stops the operation of the converter 10 by bringing all of the multiple converter units 12 into a stopped state.

[0052] The control device 50 controls the operation of the bidirectional chopper 30 and the inverter 40 based on the appropriate number of operating units determined in steps S06 and S07 (step S09). In S09, the control device 50 brings all of the multiple power conversion units in each of the bidirectional chopper 30 and the inverter 40 into an operating state and turns on all of the multiple switches.

[0053] In this way, by operating all the inverter units 42 of the inverter 40 and all the chopper units 32 of the bidirectional chopper 30 during a power outage of the AC power supply 80, it is possible to maintain the reliability of the power supply to the load 84 during the power outage.

[0054] Next, a method for determining the appropriate number of operating power conversion units in steps S02 to S04 in FIG. 3 will be described.

[0055] 4 is a block diagram showing the configuration of a portion of the control device 50 that is related to the control of the inverter 40. As shown in FIG. 4, the control device 50 includes a power outage detector 60, a number-of-operating-units calculation unit 44, a selection unit 45, and a control unit 46.

[0056] The power failure detector 60 detects whether a power failure has occurred in the AC power supply 80 based on the AC input voltage VI supplied from the AC power supply 80, and outputs a detection signal φPF indicating the detection result. For example, the power failure detector 60 determines that a power failure has occurred in the AC power supply 80 when the instantaneous value of the AC input voltage VI drops below a lower limit value. When the AC power supply 80 is healthy, the detection signal φPF is set to an L (logical low) level. When a power failure occurs in the AC power supply 80, the detection signal φPF is activated to an H (logical high) level.

[0057] The operating unit number calculation unit 44 receives the output signal Iof of the current detector CD3 and the detection signal φPF of the power failure detector 60. When the detection signal φPF is at L level (when the AC power supply 80 is healthy), the operating unit number calculation unit 44 determines the appropriate number X of operating inverter units 42 based on the load current Io indicated by the output signal Iof.

[0058] Specifically, the operating unit number calculation unit 44 acquires information about the inverters 40 from the memory 54. The information about the inverters 40 includes the number N of inverter units 42 included in the inverter 40 (total number of units), the rated output A of the inverter units 42, and the load characteristics of the inverter units 42. The load characteristics of the inverter units 42 represent the relationship between the load factor and operating efficiency of the inverter units 42. The load characteristics of the inverter units 42 are stored in the memory 54 in the form of a formula or a map.

[0059] As shown in Fig. 4, the operating efficiency of the inverter unit 42 changes depending on the load factor. In the example of Fig. 4, the highest operating efficiency can be achieved when the load factor is R1 (%), but when the load factor becomes lower than R1 (%), the operating efficiency drops sharply.

[0060] When N inverter units 42 are operated in parallel, the load current Io is equally shared among the N inverter units 42, and the shared current of each inverter unit 42 is Io / N. When N inverter units 42 are operated in parallel, if the load factor of each inverter unit 42 falls below R1 (%) and the operating efficiency is low, the operation of NX inverter units 42 can be stopped to increase the shared current of each inverter unit 42 and improve the operating efficiency of each inverter unit 42. Therefore, by controlling the number of inverter units 42 in operation so as to achieve a highly efficient load factor R1 (%), the operating efficiency of the entire inverter 40 can be improved.

[0061] The operating unit number calculation unit 44 calculates the output power of the inverter 40 based on the load current Io indicated by the output signal Iof. Furthermore, the operating unit number calculation unit 44 calculates the output power R1×A of the inverter unit 42 when the load factor is R1 (%) based on the load characteristics of the inverter unit 42. The operating unit number calculation unit 44 then divides the output power of the inverter 40 by the output power R1×A of the inverter unit 42. For example, if the output power of the inverter 40 corresponds to α% of the rated output N×A of the inverter 40, the quotient is (α×N×A) / (R1×A). The operating unit number calculation unit 44 determines the integer closest to this quotient α×N / R1 as the appropriate number of operating units X.

[0062] On the other hand, when the detection signal φPF is at H level (when the AC power supply 80 is in a power outage), the operating unit number calculation unit 44 sets the appropriate operating number X of the inverter units 42 to the total number N of units (corresponding to S06 in FIG. 3).

[0063] The operating unit number calculation unit 44 provides a signal φX indicating the appropriate operating unit number X to the selection unit 45. Based on the output signal φX of the operating unit number calculation unit 44, the selection unit 45 selects whether to put each of the N inverter units 42 into an operating state or a stopped state.

[0064] In one aspect, priorities for putting the N inverter units 42 into an operating state are set in advance. Based on the signal φX and the priorities, the selection unit 45 selects whether to put each inverter unit 42 into an operating state or a stopped state. The selection unit 45 provides the control unit 46 with signals SE1 to SEN indicating the selection results for each of the N inverter units 42.

[0065] A signal SEi indicating the selection result of the inverter unit 42_i having the i-th priority is set to H level when the inverter unit 42_i is selected to be in an operating state. When the inverter unit 42_i is selected to be in a stopped state, the signal SEi is set to L level. Note that when the appropriate number of operating units X is equal to the total number of units N, the signals SE1 to SEN are all set to H level.

[0066] For example, if the number of currently operating units is two and the appropriate number of operating units X is three, the selection unit 45 selects the inverter unit 42 with the highest priority among the stopped inverter units 42 to be in operation. Conversely, if the number of currently operating units is three and the appropriate number of operating units X is two, the selection unit 45 selects the inverter unit 42 with the highest priority among the three currently operating inverter units 42 to be in operation.

[0067] The control device 50 may include a timer 48 for measuring the time that each inverter unit 42 has been in an operating state. In this case, when the operating time measured for a certain inverter unit 42 reaches a predetermined time, the selector 45 selects this inverter unit 42 to be in a stopped state, and can select the inverter unit 42 with the highest priority among the stopped inverter units 42 to be in an operating state. In this way, the inverter units 42 to be put into an operating state are rotated, so that the operating times of the N inverter units 42 can be equalized. As a result, the occurrence of a failure in each inverter unit 42 can be delayed.

[0068] The control unit 46 controls the switches 41 and the inverter units 42 based on the output signals SE1 to SEN of the selection unit 45, the output signal Iof of the current detector CD3, and the AC output voltage VO.

[0069] Specifically, when the signal SEi is at L level, the control unit 46 stops the operation of the corresponding inverter unit 42_i and turns off the corresponding switch 41_i.

[0070] On the other hand, when the signal SEi is at H level, the control unit 46 operates the corresponding inverter unit 42_i and turns on the corresponding switch 41_i. The control unit 46 controls the inverter unit 42_i so that the AC output voltage VO becomes the sinusoidal reference voltage VOR.

[0071] Fig. 5 is a block diagram showing the configuration of a portion of the control device 50 that is related to the control of the bidirectional chopper 30. As shown in Fig. 5, the control device 50 includes a subtractor 33, a charging current calculation unit 34, a number-of-operating-units calculation unit 35, a selection unit 36, and a control unit 38.

[0072] The subtractor 33 calculates the deviation ΔVB=VBR−VB between the battery voltage VB and the reference voltage VBR. The reference voltage VBR corresponds to the target value of the battery voltage VB when the battery 82 is being charged.

[0073] The charging current calculation unit 34 calculates a current command value IBC for controlling the current flowing through the battery 82 so that the deviation ΔVB becomes zero. The charging current calculation unit 34 calculates the current command value IBC by, for example, performing a proportional calculation or a proportional-integral calculation of the deviation ΔVB. The current command value IBC corresponds to the current required to charge the battery 82.

[0074] The operating unit number calculation unit 35 receives the current command value IBC and a detection signal φPF from a power failure detector 60 (not shown). When the detection signal φPF is at an L level (when the AC power supply 80 is healthy), the operating unit number calculation unit 35 determines the appropriate number Y of operating chopper units 32 based on the current command value IBC.

[0075] Specifically, the operating unit number calculation unit 35 acquires information about the bidirectional chopper 30 from the memory 54. The information about the bidirectional chopper 30 includes the number M of chopper units 32 included in the bidirectional chopper 30 (total number of units) and the rated current B of the chopper unit 32. The operating unit number calculation unit 35 divides the current command value IBC by the rated current B. Then, the operating unit number calculation unit 35 determines the integer closest to this quotient IBC / B as the appropriate number Y of operating units.

[0076] In FIG. 5, the current command value IBC is divided by the rated current B of the chopper unit 32, but this is not limiting, and the current command value IBC may be divided by a current that the chopper unit 32 can charge into the battery 82.

[0077] On the other hand, when the detection signal φPF is at H level (when the AC power supply 80 is in a power outage), the operating unit number calculation unit 35 sets the appropriate operating number Y of chopper units 32 to the total number M of units (corresponding to S07 in FIG. 3).

[0078] The operating unit number calculation unit 35 provides a signal φY indicating the appropriate operating unit number Y to the selection unit 36. Based on the output signal φY of the operating unit number calculation unit 35, the selection unit 36 ​​selects whether to put each of the M chopper units 32 into an operating state or a stopped state.

[0079] In one aspect, similarly to the inverter 40, in the bidirectional chopper 30, priorities for putting the M chopper units 32 into an operating state are preset. The selection unit 36 ​​selects whether each chopper unit 32 is to be put into an operating state or a stopped state based on the signal φX and the priorities. The selection unit 36 ​​provides the control unit 38 with signals SE1 to SEM indicating the selection results for each of the M chopper units 32.

[0080] Signal SEk indicating the selection result of chopper unit 32_k having the kth priority is set to H level when chopper unit 32_k is selected to be in an operating state. When chopper unit 32_k is selected to be in a stopped state, signal SEk is set to L level. Note that when the appropriate number of operating units Y is equal to the total number of units M, signals SE1 to SEM are all set to H level.

[0081] The control device 50 may include a timer 37 for measuring the time that each chopper unit 32 has been in an operating state. In this case, when the operating time measured for a certain chopper unit 32 reaches a predetermined time, the selector 36 selects the chopper unit 32 to be in a stopped state, and can select the chopper unit 32 with the highest priority among the stopped chopper units 32 to be in an operating state. In this way, the chopper units 32 to be put into an operating state are rotated, so that the operating times of the M chopper units 32 can be equalized. As a result, the occurrence of a failure in each chopper unit 32 can be delayed.

[0082] The control unit 38 controls the switches 31 and the chopper units 32 based on the output signals SE1 to SEM of the selection unit 36, the output signal IBf of the current detector CD2, the battery voltage VB, the DC voltage VD, and the detection signal φPF.

[0083] Specifically, when the signal SEk is at L level, the control unit 46 stops the operation of the corresponding chopper unit 32_k and turns off the corresponding switch 31_k.

[0084] On the other hand, when the signal SEk is at H level, the control unit 38 operates the corresponding chopper unit 32_k and turns on the corresponding switch 31_k. When the detection signal φPF is at L level (when the AC power supply 80 is healthy), the control unit 38 controls the chopper unit 32_k so that the battery voltage VB becomes the reference voltage VBR.

[0085] When the detection signal φPF is at H level (when the AC power supply 80 experiences a power outage), the control unit 38 controls the chopper unit 32_k so that the DC voltage VD of the DC line 20 becomes equal to the reference voltage VDR. Note that when the AC power supply 80 experiences a power outage, all of the M chopper units 32 are selected to be in an operating state, and therefore the control unit 38 controls the M chopper units 32 so that the DC voltage VD of the DC line 20 becomes equal to the reference voltage VDR.

[0086] 6 is a block diagram showing the configuration of a portion of the control device 50 that is related to the control of the converter 10. As shown in FIG. 6, the control device 50 includes a load power calculation unit 13, a charge power calculation unit 14, an adder 15, an operating vehicle number calculation unit 16, a selection unit 17, and a control unit 19.

[0087] The load power calculation unit 13 calculates the AC power PL consumed by the load 84 (power consumption of the load 84) based on the AC output voltage VO and the output signal Iof of the current detector CD3. Specifically, the load power calculation unit 13 calculates the power consumption (active power) PL from the AC output voltage VO and the load current Io indicated by the output signal Iof, using the following equation (1): PL=VOrms×Iorms×cosθ (1) Here, VOrms represents the effective voltage applied to the load 84, Iorms represents the effective current related to the load 84, θ represents the phase difference between the load current Io and the AC output voltage VO, and cosθ represents the power factor.

[0088] The charging power calculation unit 14 calculates the AC power PB (charging power of the battery 82) to be supplied to the battery 82 based on the battery voltage VB and the output signal IBf of the current detector CD2. Specifically, the charging power calculation unit 14 calculates the charging power PB based on the product of the battery voltage VB and the battery current IB indicated by the output signal IBf.

[0089] The adder 15 calculates the total power PB+PL of the consumed power PL indicated by the signal φPL and the charging power PB indicated by the signal φPB. This total power PB+PL corresponds to the AC power supplied from the AC power supply 80 to the converter 10.

[0090] The operating unit number calculation unit 16 receives the output signal of the adder 15 and the detection signal φPF of the power failure detector 60. When the detection signal φPF is at L level (when the AC power supply 80 is healthy), the operating unit number calculation unit 16 calculates the appropriate number Z of operating converter units 12 based on the total power PL+PB (AC power supplied from the AC power supply 80 to the converter 10) indicated by the output signal of the adder 15.

[0091] Specifically, the operating unit number calculation unit 16 acquires information about the converter 10 from the memory 54. The information about the converter 10 includes the number L of converter units 12 included in the converter 10 (total number of units), the rated output C of the converter unit 12, and the load characteristics of the converter unit 12. The load characteristics of the converter unit 12 represent the relationship between the load factor and operating efficiency of the converter unit 12. The load characteristics of the converter unit 12 are stored in the memory 54 in the form of a formula or a map.

[0092] As shown in Fig. 6, the operating efficiency of the converter unit 12 changes depending on the load factor. In the example of Fig. 6, the highest operating efficiency can be achieved when the load factor is R2 (%), but when the load factor becomes lower than R2 (%), the operating efficiency drops sharply.

[0093] When L converter units 12 are operated in parallel, the AC input current Ii is equally shared among the L converter units 12, and the shared current of each converter unit 12 is Ii / L. When L converter units 12 are operated in parallel, if the load factor of each converter unit 12 falls below R2 (%) and the operating efficiency is low, the operation of LZ converter units 12 can be stopped to increase the shared current of each converter unit 12 and improve the operating efficiency of each converter unit 12. Therefore, by controlling the number of operating converter units 12 so as to achieve a highly efficient load factor R2 (%), the operating efficiency of the entire converter 10 can be improved.

[0094] Based on the load characteristics of the converter unit 12, the operating unit number calculation unit 16 calculates the output power R2×C of the converter unit 12 when the load factor is R2 (%). Then, the operating unit number calculation unit 16 divides the total power PL+PB by the output power R2×C of the converter unit 12. For example, if the total power PL+PB corresponds to β% of the rated output L×C of the converter 10, the quotient is (β×L×C) / (R2×C). The operating unit number calculation unit 16 determines the integer closest to this quotient β×L / R2 as the appropriate number of operating units Z.

[0095] On the other hand, when the detection signal φPF is at H level (when the AC power supply 80 is in a power outage), the operating unit number calculation unit 16 sets the appropriate operating number Z of converter units 12 to 0 (corresponding to S08 in FIG. 3).

[0096] The operating unit number calculation unit 16 provides a signal φZ indicating the appropriate operating unit number Z to the selection unit 17. Based on the output signal φZ of the operating unit number calculation unit 16, the selection unit 17 selects whether to put each of the L converter units 12 into an operating state or a stopped state.

[0097] In one aspect, similarly to the inverter 40 and the bidirectional chopper 30, in the converter 10, priorities for putting the L converter units 12 into an operating state are set in advance. The selection unit 17 selects whether each converter unit 12 is to be put into an operating state or a stopped state based on the signal φZ and the priorities. The selection unit 17 provides the control unit 19 with signals SE1 to SEL indicating the selection results of each of the L converter units 12.

[0098] A signal SEj indicating the selection result of the converter unit 12_j having the jth priority is set to H level when the converter unit 12_j is selected to be in an operating state. When the converter unit 12_j is selected to be in a stopped state, the signal SEj is set to L level. Note that when the appropriate number of operating units Z is equal to the total number of units L, the signals SE1 to SEL are all set to H level.

[0099] The control device 50 may include a timer 18 for measuring the time that each converter unit 12 has been in operation. In this case, when the operation time measured for a certain converter unit 12 reaches a predetermined time, the selector 17 selects this converter unit 12 to be in a stopped state, and can select the converter unit 12 with the highest priority among the stopped converter units 12 to be in an operating state. In this way, the converter units 12 to be put into operation are rotated, so that the operating times of the L converter units 12 can be equalized. As a result, the occurrence of a failure in each converter unit 12 can be delayed.

[0100] The control unit 19 controls the switches 11 and the converter units 12 based on the output signals SE1 to SEL of the selection unit 17, the output signal Iif of the current detector CD1, the battery voltage VB, the DC voltage VD, and the detection signal φPF.

[0101] Specifically, when the signal SEj is at L level, the control unit 19 stops the operation of the corresponding converter unit 12_k and turns off the corresponding switch 11_j.

[0102] On the other hand, when the signal SEj is at H level, the control unit 19 operates the corresponding converter unit 12_j and turns on the corresponding switch 11_j. The control unit 19 controls the converter unit 12_j so that the DC voltage VD of the DC line 20 becomes equal to the reference voltage VDR.

[0103] In the event of a power outage of the AC power supply 80, all of the L converter units 12 are selected to be in a stopped state, and the control unit 19 stops the operation of the converter 10.

[0104] Next, an example of the operation of the uninterruptible power supply 100 will be described with reference to FIGS. 7 to 9, in each of the power converters, the converter 10, the bidirectional chopper 30, and the inverter 40, the power conversion units in operation are represented by solid lines, and the power conversion units in a stopped state are represented by dashed lines. Also, in each figure, arrows indicate the flow of power.

[0105] Fig. 7 is a diagram showing an example of the operation of the uninterruptible power supply 100 when the AC power supply 80 is healthy. In Fig. 7, the load 84 is an electric device with a low power factor cos θ. The battery 82 is in a fully charged state.

[0106] In such a case, the power consumption PL (PL=VOrms×Iorms×cosθ) of the load 84 is smaller than the AC power (apparent power=VOrms×Iorms) output by the inverter 40. Furthermore, because the battery 82 is fully charged, the charging power PB required to maintain the battery voltage VB at the reference voltage VBR is also smaller. In other words, the AC power (total power PB+PL) supplied from the AC power supply 80 to the converter 10 is also smaller.

[0107] In such a situation, the appropriate number of operating converter units 12 (e.g., Z=1) and the appropriate number of operating chopper units 32 (e.g., Y=1) can be made smaller than the appropriate number of operating inverter units 42 (e.g., X=3).

[0108] In a conventional uninterruptible power supply system configured with multiple uninterruptible power supplies connected in parallel, the appropriate number of operating uninterruptible power supplies is determined based on the load current Io. Therefore, the same number of converter units and chopper units as the number of operating inverter units determined from the load current Io are operated. Therefore, when the load has a low power factor and the battery is fully charged, the number of operating converter units is excessive compared to the amount of AC power supplied from the AC power source, resulting in low operating efficiency of the converter as a whole. Furthermore, the number of operating chopper units is excessive compared to the amount of charging power of the battery, resulting in low operating efficiency of the bidirectional chopper. As a result, there is a concern that the power supply efficiency of the uninterruptible power supply system will be low.

[0109] In contrast, in the present embodiment, the number X of operating inverter units 42, the number Y of operating chopper units 32, and the number Z of operating converter units 12 can be individually controlled, so that it is possible to operate an appropriate number of inverter units 42 for the magnitude of the load current Io, an appropriate number of converter units 12 for the magnitude of the AC power supplied from the AC power supply 80, and a number of chopper units 32 necessary to charge the battery 82. Therefore, when the load 84 has a low power factor and the battery 82 is fully charged as shown in FIG. 7, the inverter 40, the bidirectional chopper 30, and the converter 10 can each be operated with high operating efficiency. As a result, it is possible to improve the power supply efficiency of the uninterruptible power supply 100.

[0110] Fig. 8 is a diagram showing an example of the operation of the uninterruptible power supply 100 during a power outage of the AC power supply 80. As shown in Fig. 8, when a power outage occurs in the AC power supply 80, the control device 50 sets the appropriate number Z of converter units 12 in operation to 0 and stops the operation of the converter 10. In addition, the control device 50 operates all chopper units 32 included in the bidirectional chopper 30 and operates all inverter units 42 included in the inverter 40.

[0111] In this way, even if the load 84 fluctuates during a power outage of the AC power supply 80, AC power can be stably supplied to the load 84. Therefore, the reliability of the power supply to the load 84 can be maintained.

[0112] Fig. 9 is a diagram showing an example of the operation of the uninterruptible power supply 100 when power is restored to the AC power supply 80. In Fig. 9, the load 84 is a light load. The battery 82 has supplied power to the load 84 during the power outage, and as a result, the amount of stored electricity therein has decreased.

[0113] In such a case, the AC power output by inverter 40 decreases, and the power consumption PL of load 84 also decreases. On the other hand, because the amount of stored power in battery 82 is small, the charging power PB required to maintain battery voltage VB at reference voltage VBR increases. Therefore, the AC power (total power PB+PL) supplied from AC power supply 80 to converter 10 also increases.

[0114] In such a situation, the appropriate number Z of converter units 12 in operation (for example, Z=2) and the appropriate number Y of chopper units 32 in operation (for example, Y=3) can be made larger relative to the appropriate number X of inverter units 42 in operation (for example, X=1). As a result, when power is restored to the AC power supply 80, the battery 82 can be quickly charged and the amount of electricity stored in the battery 82 can be restored while an appropriate number of inverter units 42 is operating relative to the magnitude of the load current Io.

[0115] [Embodiment 2] Fig. 10 is a circuit block diagram showing the configuration of an uninterruptible power supply according to embodiment 2. As shown in Fig. 10, an uninterruptible power supply 110 according to embodiment 2 differs from uninterruptible power supply 100 shown in Fig. 1 in that it does not include bidirectional chopper 30.

[0116] In the uninterruptible power supply 110, the control device 50 is configured to include the control configuration shown in Fig. 4 and Fig. 6. That is, when the AC power supply 80 is healthy, the control device 50 determines the appropriate number X of inverter units 42 in operation based on the output current (i.e., the load current Io) of the inverter 40. The control device 50 also determines the appropriate number Z of converter units 12 in operation based on the AC power supplied from the AC power supply 80 to the converter 10.

[0117] When the AC power supply 80 experiences a power outage, the control device 50 sets the appropriate number Z of converter units 12 in operation to 0 and stops operation of the converter 10. The control device 50 also sets the appropriate number X of inverter units 42 in operation to the total number N of units and operates all of the inverter units 42 included in the inverter 40.

[0118] Therefore, the same effects as those of the first embodiment can be obtained in the second embodiment as well.

[0119] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The 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]

[0120] 10 converter, 11, 31, 41, S1 to S3 switches, 12 converter unit, 13 load power calculation unit, 14 charging power calculation unit, 15 adder, 16, 35, 44 operating unit number calculation unit, 17, 36, 45 selection unit, 18, 37, 48 timer, 19, 38, 46 control unit, 20 DC line, 22, C1, C2 capacitor, 30 bidirectional chopper, 32 chopper unit, 33 subtractor, 34 charging current calculation unit, 40 inverter, 42 inverter unit, 50 control device, 52 CPU, 54 memory, 56 I / O circuit, 60 power outage detector, 80 AC power supply, 82 battery, 84 load, 100, 110 uninterruptible power supply, CD1 to CD3 current detector, T1 AC input terminal, T2 DC terminal, T3 AC output terminal, L1, L2 reactor, F1, F2 AC filter.

Claims

1. a converter that converts AC power supplied from an AC power source into DC power and outputs the DC power to a DC line; an inverter that converts DC power supplied from the DC line into AC power and supplies the AC power to a load; a control device that controls the converter and the inverter, a power storage device that stores DC power of the DC line is connected to the DC line; the converter includes a plurality of converter units connected in parallel between the AC power supply and the DC line; the inverter includes a plurality of inverter units connected in parallel between the DC line and the load; When the AC power supply is healthy, the control device determining an appropriate number of inverter units to be operated based on the output current of the inverter; determining an appropriate number of converter units to be operated based on the AC power supplied from the AC power source to the converter; An uninterruptible power supply operates the determined appropriate number of inverter units and converter units.

2. The control device calculating a total power of the power consumption of the load and the charging power supplied to the power storage device from the DC line; 2. The uninterruptible power supply according to claim 1, wherein the appropriate number of converter units to be operated is calculated from the total power by referring to the relationship between the load factor and the operating efficiency of the converter units.

3. The control device 3. The uninterruptible power supply according to claim 1, wherein the appropriate number of inverter units to be operated is calculated from the output current of the inverters by referring to the relationship between the load factor and the operation efficiency of the inverter units.

4. 2. The uninterruptible power supply according to claim 1, wherein the control device stops operation of the converter and operates all of the plurality of inverter units when a power outage occurs in the AC power supply.

5. 2. The uninterruptible power supply according to claim 1, wherein the control device has a timer for measuring the time that each of the inverter units is in an operating state, and rotates the inverter units that are in an operating state based on the time measured by the timer.

6. 2. The uninterruptible power supply according to claim 1, wherein the control device has a timer for measuring the time that each of the converter units is in an operating state, and rotates the converter units that are in an operating state based on the time measured by the timer.

7. further comprising a bidirectional chopper that exchanges DC power between the DC line and the power storage device, the bidirectional chopper being configured to charge the power storage device with DC power from the DC line when the AC power supply is healthy; the bidirectional chopper includes a plurality of chopper units connected in parallel between the DC line and the power storage device, 2. The uninterruptible power supply according to claim 1, wherein the control device determines an appropriate number of operating chopper units based on a charging current required to charge the power storage device when the AC power supply is healthy.

8. 8. The uninterruptible power supply according to claim 7, wherein the control device determines an appropriate number of the chopper units to be operated based on the charging current and a rated current of the chopper units.

9. the bidirectional chopper is configured to supply DC power from the power storage device to the DC line when a power outage occurs in the AC power supply; 9. The uninterruptible power supply according to claim 7, wherein the control device operates all of the plurality of chopper units when a power outage occurs in the AC power supply.

10. 8. The uninterruptible power supply according to claim 7, wherein the control device has a timer for measuring the time that each chopper unit is in an operating state, and rotates the chopper units that are in an operating state based on the time measured by the timer.

Images