Uninterruptible power supply device

Abstract

A converter (10) converts AC power supplied from an AC power source (80) into DC power and outputs the DC power to a DC line (20). An 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. A control device (50) determines a proper number of operating inverter units (42) based on an output current of the inverter (40) when the AC power source (80) is healthy. The control device (50) determines a proper number of operating converter units (12) based on AC power supplied from the AC power source (80) to the converter (10). The control device (50) causes the determined proper number of operating inverter units (42) and the determined proper number of operating converter units (12) to operate.

Description

Technical Field

[0001] This disclosure relates to uninterruptible power supply devices. Background Technology

[0002] For example, Japanese Patent Application Publication No. 2020-005410 (Patent Document 1) discloses an uninterruptible power supply system having multiple uninterruptible power supply devices. Multiple uninterruptible power supply devices are connected in parallel between an AC power source and a load. A suitable number of operating uninterruptible power supply devices are determined to supply the load current, and an appropriate number of these devices are set to an operating state to supply the load current, while the remaining devices are set to a standby state.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-005410 Summary of the Invention

[0004] The problem that the invention aims to solve In Patent Document 1, the converters and inverters belonging to the uninterruptible power supply (UPS) device set to an operating state are operated. Furthermore, the operation of the converters and inverters belonging to the UPS device set to a stopped state is stopped. That is, a number of inverters determined based on the load current and an equal number of converters are operated separately.

[0005] Therefore, when a low-power-factor load is connected to an uninterruptible power supply (UPS) system, each inverter can operate at high efficiency. However, relative to the AC power supplied from the AC power source (equivalent to the power consumed by the load), the number of operating converters may be excessive. In this case, the operating efficiency of each converter decreases, raising concerns about a reduction in the overall power supply efficiency of the UPS system.

[0006] Therefore, the main objective of this disclosure is to provide an uninterruptible power supply device that can improve power supply efficiency.

[0007] Methods for solving problems The uninterruptible power supply (UPS) device disclosed herein comprises: 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 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. An energy storage device for accumulating DC power on the DC line is connected to the DC line. The converter includes multiple converter units connected in parallel between the AC power source and the DC line. The inverter includes multiple inverter units connected in parallel between the DC line and the load. When the AC power source is available, the control device determines the appropriate number of inverter units to operate based on the output current of the inverter. The control device also determines the appropriate number of converter units to operate based on the AC power supplied from the AC power source to the converter. The control device operates the determined appropriate number of inverter units and converter units.

[0008] Invention Effects According to this disclosure, an uninterruptible power supply device that can improve power supply efficiency can be provided. Attached Figure Description

[0009] Figure 1 This is a circuit block diagram showing the structure of the uninterruptible power supply device according to Embodiment 1.

[0010] Figure 2 This is a block diagram representing an example of the hardware structure of a control device.

[0011] Figure 3 It is a flowchart showing the operation process of the control device.

[0012] Figure 4 It is a block diagram showing the structure of the part of the control device related to the control of the inverter.

[0013] Figure 5 It is a block diagram showing the structure of the part of the control device related to the control of the bidirectional chopper.

[0014] Figure 6 It is a block diagram showing the structure of the part of the control device related to the control of the converter.

[0015] Figure 7 This is a diagram illustrating the operation of an uninterruptible power supply (UPS) when the AC power supply is functioning properly.

[0016] Figure 8 This is a diagram illustrating the operation of an uninterruptible power supply (UPS) device when the AC power supply fails.

[0017] Figure 9 This is a diagram illustrating the operation of an uninterruptible power supply (UPS) device when AC power is restored.

[0018] Figure 10This is a circuit block diagram showing the structure of the uninterruptible power supply device according to Embodiment 2. Detailed Implementation

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, the same or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will generally not be repeated.

[0020] [Implementation Method 1] Figure 1 This is a circuit block diagram illustrating the structure of the uninterruptible power supply device according to Embodiment 1. For example... Figure 1 As shown, the uninterruptible power supply 100 includes an AC input terminal T1, a DC terminal T2, and an AC output terminal T3. The AC input terminal T1 receives AC power of a specified frequency (e.g., a commercial frequency) from an AC power source 80. The AC power source 80 can be a commercial AC power source or a generator.

[0021] DC terminal T2 is connected to battery 82. Battery 82 corresponds to one embodiment of an "energy storage device" that stores DC power. Battery 82 is a secondary battery such as a lead-acid battery, nickel-metal hydride battery, or lithium-ion battery. Alternatively, a double-layer capacitor or flywheel can be connected instead of battery 82.

[0022] 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.

[0023] The uninterruptible power supply device 100 also includes switches S1 to S3, converter 10, current detectors CD1 to CD3, DC line 20, capacitors C1, C2, and 22, reactors L1 and L2, bidirectional chopper 30, inverter 40, and control device 50.

[0024] Switch S1 and reactor L1 are connected in series between AC input terminal T1 and AC node of converter 10. Switch S1 is controlled by control device 50. When AC power supply 80 is intact, switch S1 is closed, supplying AC power from AC power supply 80 to converter 10 via switch S1. When AC power supply 80 is de-energized, switch S1 is open, disconnecting AC power supply 80 from converter 10.

[0025] 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 a signal Iif representing its detected value to the control device 50.

[0026] Capacitor C1 is connected at the node between switch S1 and reactor L1. Capacitor C1 and reactor L1 constitute AC filter F1. AC filter F1 is a low-pass filter that allows AC power of a specified frequency to flow from AC power source 80 to converter 10, while preventing the switching frequency signal generated by converter 10 from flowing to AC power source 80.

[0027] Converter 10 is controlled by control device 50. When AC power supply 80 is intact, converter 10 converts the AC power received at AC input terminal T1 into DC power and outputs it to DC line 20. The output voltage of converter 10 can be controlled to a desired value. When AC power supply 80 is interrupted, the operation of converter 10 stops.

[0028] The converter 10 includes multiple converter units 12_1, 12_2, and 12_3 and multiple switches 11_1, 11_2, and 11_3. In the following description, the multiple converter units 12_1, 12_2, and 12_3 are sometimes collectively referred to as "converter unit 12", and the multiple switches 11_1, 11_2, and 11_3 are collectively referred to as "switch 11". The number L of each converter unit 12 and switch 11 is not limited to 3; any number is acceptable.

[0029] Multiple converter units 12_1, 12_2, and 12_3 are connected in parallel between the AC and DC nodes of converter 10. Converter unit 12 is a known configuration including multiple semiconductor switching elements and multiple diodes, and is controlled by control device 50. Converter unit 12 converts AC power input from the AC node via corresponding switch 11 into DC power and outputs it to the DC node.

[0030] Multiple switches 11_1, 11_2, and 11_3 are respectively configured to correspond with multiple converter units 12_1, 12_2, and 12_3. Switch 11 is connected in series with the corresponding converter unit 12 between the AC and DC nodes of converter 10. Switch 11 is controlled by control device 50, turning on when the corresponding converter unit 12 is in the operating state and turning off when the corresponding converter unit 12 is in the stopped state.

[0031] Capacitor 22 is connected to DC line 20 to smooth the voltage in DC line 20. The instantaneous value of the DC voltage VD appearing in DC line 20 is detected by control device 50.

[0032] DC line 20 is connected to the high-voltage side node of bidirectional chopper 30, and the low-voltage side node of bidirectional chopper 30 is connected to DC terminal T2 via switch S2. Switch S2 is turned on when uninterruptible power supply 100 is in use, for example, when uninterruptible power supply 100 and battery 82 are being maintained.

[0033] The bidirectional chopper 30, controlled by the control device 50, receives and supplies DC power between the DC line 20 and the battery 82. When the AC power supply 80 is intact, 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 fails, the bidirectional chopper 30 supplies the DC power from the battery 82 to the inverter 40 via the DC line 20.

[0034] Current detector CD2 detects the current (hereinafter also referred to as "battery current") IB flowing between bidirectional chopper 30 and battery 82, and provides a signal IBf representing its detected value to control device 50. The instantaneous value of the inter-terminal voltage (hereinafter also referred to as "battery voltage") VB of battery 82 appearing at DC terminal T2 is detected by control device 50.

[0035] The bidirectional chopper 30 includes multiple chopper units 32_1, 32_2, and 32_3 and multiple switches 31_1, 31_2, and 31_3. In the following description, the multiple chopper units 32_1, 32_2, and 32_3 are sometimes collectively referred to as "chopper unit 32," and the multiple switches 31_1, 31_2, and 31_3 are collectively referred to as "switch 31." The number M of each chopper unit 32 and switch 31 is not limited to 3; any number is acceptable.

[0036] Multiple chopper units 32_1, 32_2, and 32_3 are connected in parallel between the high-voltage side node and the low-voltage side node of the bidirectional chopper 30. Chopper unit 32 has a known configuration including multiple semiconductor switching elements and multiple diodes, and is controlled by control device 50. When storing DC power in battery 82, chopper unit 32 steps down the DC voltage VD of DC line 20 and supplies it to battery 82 via corresponding switch 31. Conversely, when supplying DC power from battery 82 to inverter 40, chopper unit 32 boosts the battery voltage VB input via corresponding switch 31 and outputs it to DC line 20.

[0037] Multiple switches 31_1, 31_2, and 31_3 are respectively configured to correspond with multiple chopper units 32_1, 32_2, and 32_3. Switch 31 is connected in series with the corresponding chopper unit 32 between the high-voltage side node and the low-voltage side node of the bidirectional chopper 30. Switch 31 is controlled by the control device 50, turning on when the corresponding chopper unit 32 is in the operating state and turning off when the corresponding chopper unit 32 is in the stopped state.

[0038] DC line 20 is connected to the DC node of inverter 40. Inverter 40, controlled by control device 50, converts the DC power supplied from converter 10 or bidirectional chopper 30 via DC line 20 into AC power and outputs it to the AC node. That is, when AC power supply 80 is available, inverter 40 converts the DC power supplied from converter 10 via DC line 20 into AC power; when AC power supply 80 is unavailable, it converts the DC power supplied from bidirectional chopper 30 via DC line 20 into AC power. The output voltage of inverter 40 can be controlled to a desired value.

[0039] Inverter 40 includes multiple inverter units 42_1, 42_2, and 42_3 and multiple switches 41_1, 41_2, and 41_3. In the following description, the multiple inverter units 42_1, 42_2, and 42_3 are sometimes collectively referred to as "inverter unit 42," and the multiple switches 41_1, 41_2, and 41_3 are collectively referred to as "switch 41." The number N of each inverter unit 42 and switch 41 is not limited to 3; any number is acceptable.

[0040] Multiple inverter units 42_1, 42_2, and 42_3 are connected in parallel between the DC node and the AC node of inverter 40. Inverter unit 42 has a known configuration including multiple semiconductor switching elements and multiple diodes, and is controlled by control device 50. Inverter unit 42 converts DC power input from the DC node via corresponding switch 41 into AC power and outputs it to the AC node.

[0041] Multiple switches 41_1, 41_2, and 41_3 are respectively configured to correspond to multiple inverter units 42_1, 42_2, and 42_3. Switch 41 is connected in series with the corresponding inverter unit 42 between the DC and AC nodes of inverter 40. Switch 41 is controlled by control device 50, turning on when the corresponding inverter unit 42 is in the operating state and turning off when the corresponding inverter unit 42 is in the stopped state.

[0042] The AC node of inverter 40 is connected to the first terminal of switch S3 via reactor L2, and the second terminal of switch S3 is connected to the AC output terminal T3. Capacitor C2 is connected to the first terminal of switch S3. Reactor L2 and capacitor C2 constitute AC filter F2. AC filter F2 is a low-pass filter that allows AC power of a specified frequency generated by inverter 40 to flow to AC output terminal T3, while preventing signals of the switching frequency generated by inverter 40 from flowing to AC output terminal T3.

[0043] Switch S3 is controlled by control device 50 and is turned on in inverter power supply mode, which supplies AC power generated by inverter 40 to load 84, and turned off in bypass power supply mode, which supplies AC power from bypass AC power source (not shown) to load 84.

[0044] The instantaneous value of the AC output voltage VO at node N2 is detected by the control device 50. The current detector CD3 detects the current (hereinafter also referred to as "load current") Io flowing between the inverter 40 and the AC output terminal T3, and provides a signal Iof representing its detected value to the control device 50.

[0045] The control device 50 controls the uninterruptible power supply device 100 as a whole based on 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.

[0046] Figure 2 This is a block diagram illustrating an example of the hardware structure of the control device 50. The control device 50 can typically be constructed from a microcomputer with a pre-stored program.

[0047] like Figure 2 As shown, the control device 50 includes a CPU (Central Processing Unit) 52, a memory 54, and input / output (I / O) circuitry 56. The CPU 52, memory 54, and I / O circuitry 56 can exchange data via a bus 58. A portion of the memory 54 stores a program, which is executed by the CPU 52 to perform the various functions described later. The I / O circuitry 56 exchanges signals and data with external devices of the control device 50.

[0048] The data provided from outside the control device 50 includes information related to the number of power conversion units included in each power converter of the converter 10, the bidirectional chopper 30, and the inverter 40, as well as information related to the rated output and operating efficiency of each power conversion unit of the converter unit 12, the chopper unit 32, and the inverter unit 42. This acquired data is stored in the memory 54.

[0049] Or, with Figure 2 Unlike other examples, at least a portion of the control device 50 can be constructed using circuits such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit). Alternatively, at least a portion of the control device 50 can also be constructed using analog circuits.

[0050] Next, the operation of the uninterruptible power supply device 100 will be explained.

[0051] like Figure 1 As shown, in the uninterruptible power supply (UPS) device 100, each power converter of the converter 10, bidirectional chopper 30, and inverter 40 is configured to include multiple power conversion units (converter unit 12, chopper unit 32, and 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 UPS device 100.

[0052] Figure 3 This is a flowchart illustrating the operation of the control device 50. Figure 3 The flowchart shown is executed repeatedly during the operation of the uninterruptible power supply device 100 whenever a predetermined condition is met (every specified period).

[0053] like Figure 3 As shown, the control device 50 first detects whether a power outage of the AC power supply 80 has occurred (step S01). In S01, the control device 50 determines that a power outage of the AC power supply 80 has occurred, for example, if the instantaneous value of the AC input voltage VI supplied from the AC power supply 80 is lower than the lower limit value.

[0054] When the AC power supply 80 is in good condition (when S01 determines "no"), the control device 50 determines the appropriate number of operating power conversion units in each power converter of the converter 10, bidirectional chopper 30 and inverter 40 (steps S02 to S04).

[0055] Specifically, the control device 50 determines the appropriate number X of inverter units 42 to operate for the inverter 40 (step S02). In S02, the control device 50 determines the appropriate number X of inverter units 42 to operate based on the output current (i.e., load current Io) of the inverter 40. X is an integer greater than or equal to 1 and less than or equal to N. N is the number of inverter units 42 contained in the inverter 40 (total number of units). The control device 50 determines the appropriate number X of inverter units 42 to operate at a load rate that maximizes operating efficiency. The method for determining the appropriate number X of inverter units will be explained in detail later.

[0056] Additionally, the control device 50 determines the appropriate number Y of chopper units 32 to operate for the bidirectional chopper 30 (step S03). In S03, the control device 50 determines the appropriate number Y of chopper units 32 to operate based on the charging current required to charge the battery 82. Y is an integer greater than or equal to 0 and less than or equal to M. 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 operate in a manner that minimizes the number of chopper units 32 required to charge the battery 82. The method for determining the appropriate number Y of chopper units will be explained in detail later.

[0057] Furthermore, the control device 50 determines the appropriate number Z of converter units 12 to operate for the converter 10 (step S04). In S04, the control device 50 determines the appropriate number Z of converter units 12 to operate based on the AC power supplied from the AC power source 80 to the converter 10. Z is an integer greater than or equal to 1 and less than or equal to L. 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 is equivalent to the total AC power consumed by the load 84 (power consumed by the load 84) and the AC power supplied to the battery 82 (charging power of the battery 82). The control device 50 determines the appropriate number Z of converter units 12 to operate at a load rate that maximizes operating efficiency. The method for determining the appropriate number Z of units to operate will be explained in detail later.

[0058] Once the appropriate number of 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 sets the appropriate number of operating power conversion units in each power converter to the operating state and turns on the corresponding switches. Additionally, the control device 50 sets the remaining power conversion units to the stop state and turns off the corresponding switches.

[0059] Returning to step S01, in the event of a power outage of AC power supply 80 (when S01 is determined to be "yes"), control device 50 does not determine the appropriate number of operating units in steps S02 to S04. Instead, control device 50 sets the appropriate number X of operating inverter units 42 to the total number of units N (step S06). That is, control device 50 sets all inverter units 42 to the operating state.

[0060] In addition, for the bidirectional chopper 30, the control device 50 sets the appropriate number Y of operating chopper units 32 to the total number of units M (step S07). That is, the control device 50 sets all of the multiple chopper units 32 to the operating state.

[0061] On the other hand, the control device 50 sets the appropriate number Z of operating converter units 12 to 0 for the converter 10 (step S08). That is, the control device 50 stops the operation of the converter 10 by setting all of the multiple converter units 12 to the stop state.

[0062] Based on the appropriate number of operating units determined in steps S06 and S07, the control device 50 controls the operation of the bidirectional chopper 30 and the inverter 40 (step S09). In S09, the control device 50 ensures that all multiple power conversion units in both the bidirectional chopper 30 and the inverter 40 are in operation and that all multiple switches are turned on.

[0063] In this way, when the AC power supply 80 fails, the reliability of power supply to the load 84 can be maintained by operating all inverter units 42 of the inverter 40 and all chopper units 32 of the bidirectional chopper 30.

[0064] Next, regarding Figure 3 The method for determining the appropriate number of operating power conversion units in steps S02 to S04 will be explained.

[0065] Figure 4 This is a block diagram showing the structure of the parts of the control device 50 related to the control of the inverter 40. For example... Figure 4 As shown, the control device 50 includes a power failure detector 60, an operating unit calculation unit 44, a selection unit 45, and a control unit 46.

[0066] The power outage detector 60 detects whether a power outage 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 indicating the detection result. PF. For example, the power outage detector 60 determines that a power outage has occurred in the AC power supply 80 when the instantaneous value of the AC input voltage VI is lower than the lower limit. When the AC power supply 80 is intact, the detection signal... PF is set to L (logic low) level. In the event of a power outage at AC power supply 80, the detection signal... PF is activated at the H (logic high) level.

[0067] The unit 44, which calculates the number of operating units, receives the output signal Iof from the current detector CD3 and the detection signal from the power outage detector 60. PF. The operating unit 44 detects signals. When PF is at level L (when AC power supply 80 is intact), the appropriate number of inverter units X to operate is determined based on the load current Io represented by the output signal Iof.

[0068] Specifically, the operating unit calculation unit 44 retrieves information related to the inverter 40 from the memory 54. This information includes the number of inverter units 42 (total number of units) N contained in the inverter 40, the rated output A of each inverter unit 42, and the load characteristics of each inverter unit 42. The load characteristics of each inverter unit 42 represent the relationship between its load rate and operating efficiency. These load characteristics are stored in the memory 54 in the form of a mathematical expression or a mapping.

[0069] like Figure 4 As shown, the operating efficiency of inverter unit 42 varies depending on the load rate. Figure 4 In the example, the highest operating efficiency is achieved when the load rate is R1 (%), but if the load rate is lower than R1 (%), the operating efficiency drops sharply.

[0070] When N inverter units 42 are operated in parallel, the load current Io is equally shared by 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 rate of each inverter unit 42 is below R1 (%) and the operating efficiency is low, stopping the operation of N inverter units 42 can 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 to achieve a high-efficiency load rate R1 (%), the overall operating efficiency of the inverter 40 can be improved.

[0071] The operating unit calculation unit 44 calculates the output power of the inverter 40 based on the load current Io represented by the output signal Iof. Additionally, based on the load characteristics of the inverter unit 42, the operating unit calculation unit 44 calculates the output power R1×A of the inverter unit 42 at a load rate of R1 (%). Then, the operating unit calculation unit 44 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 is equivalent to α% of the rated output N×A of the inverter 40, the quotient is (α×N×A) / (R1×A). The operating unit calculation unit 44 determines the appropriate operating unit number X as the integer closest to this quotient α×N / R1.

[0072] On the other hand, in detecting signals When PF is at level H (when AC power supply 80 is interrupted), the operating unit calculation unit 44 sets the appropriate operating number X of inverter unit 42 to the total number of units N (corresponding to...). Figure 3 S06).

[0073] The operating unit 44 will display a signal indicating the appropriate operating number X. X is provided to the selection unit 45. The selection unit 45 is based on the output signal of the operating unit 44. X, select whether to set N inverter units 42 to the running state or the stopped state respectively.

[0074] In one respect, a priority order for the N inverter units 42 to be in operation is preset. The selection unit 45 selects based on the signal. X and the priority order determine whether to set each inverter unit 42 to 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 of each of the N inverter units 42.

[0075] The signal SEi, indicating the selection result of the i-th inverter unit 42_i, is set to H level when inverter unit 42_i is selected to operate. When inverter unit 42_i is selected to stop, the signal SEi is set to L level. Furthermore, when the appropriate number of operating units X is equal to the total number of units N, signals SE1 through SEN are all set to H level.

[0076] For example, if the current number of operating inverters is 2 and the appropriate number of operating inverters X is 3, the selection unit 45 will reselect the inverter unit 42 with the highest priority among the inverter units 42 in the stopped state to be in the operating state. Conversely, if the current number of operating inverters is 3 and the appropriate number of operating inverters X is 2, the selection unit 45 will select the inverter unit 42 with the highest priority among the 3 inverter units 42 currently in the operating state to be in the stopped state.

[0077] The control device 50 may also include a timer 48 for measuring the time during which each inverter unit 42 is set to the operating state. In this case, when the measured operating time for a certain inverter unit 42 reaches a predetermined time, the selection unit 45 can select that inverter unit 42 to the stop state, and select the inverter unit 42 with the highest priority among the stop inverter units 42 to the operating state. In this way, the inverter units 42 set to the operating state are rotated, thereby making the operating time of N inverter units 42 equal. As a result, the occurrence of failure of each inverter unit 42 can be delayed.

[0078] The control unit 46 controls multiple switches 41 and multiple 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.

[0079] Specifically, when the signal SEi is at the L level, the control unit 46 stops the operation of the corresponding inverter unit 42_i and disconnects the corresponding switch 41_i.

[0080] On the other hand, when the signal SEi is at level H, 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 in a manner that makes the AC output voltage VO a sinusoidal reference voltage VOR.

[0081] Figure 5 This is a block diagram showing the structure of the parts of the control device 50 related to the control of the bidirectional chopper 30. For example... Figure 5 As shown, the control device 50 includes a subtractor 33, a charging current calculation unit 34, an operating unit calculation unit 35, a selection unit 36, and a control unit 38.

[0082] Subtractor 33 calculates the deviation ΔVB between the battery voltage VB and the reference voltage VBR, which is ΔVB = VBR - VB. The reference voltage VBR corresponds to the target value of the battery voltage VB when the battery 82 is being charged.

[0083] The charging current calculation unit 34 calculates the current command value IBc used to control the current flowing in the battery 82, with the deviation ΔVB set to 0. The charging current calculation unit 34 calculates the current command value IBc, for example, by performing a proportional calculation or a proportional-integral calculation on the deviation ΔVB. The current command value IBc corresponds to the current required to charge the battery 82.

[0084] The unit 35, which calculates the number of operating units, receives the current command value IBc and the detection signal from the power outage detector 60 (not shown). PF. The operating unit 35 detects signals. When PF is at L level (when AC power supply 80 is intact), the appropriate number of operating units Y of chopper unit 32 is determined based on the current command value IBc.

[0085] Specifically, the operation count calculation unit 35 retrieves information related to the bidirectional chopper 30 from the memory 54. This information includes the number of chopper units 32 (total number of units) M contained in the bidirectional chopper 30 and the rated current B of each chopper unit 32. The operation count calculation unit 35 divides the current command value IBc by the rated current B. Then, the operation count calculation unit 35 determines the appropriate operation count Y from the integer closest to this quotient IBc / B.

[0086] In addition, although Figure 5 The current command value IBc is divided by the rated current B of the chopper unit 32, but it is not limited to this. The current command value IBc can also be divided by the current that the chopper unit 32 can use to charge the battery 82.

[0087] On the other hand, in detecting signals When PF is at level H (when AC power supply 80 is interrupted), the operating unit 35 sets the appropriate operating number Y of the chopper unit 32 to the total number of units M (corresponding to...). Figure 3 (S07).

[0088] The operating unit 35 will display a signal indicating the appropriate operating number Y. Y is provided to the selection unit 36. The selection unit 36 ​​is based on the output signal of the operating unit 35. Y, select whether to set the M chopper units 32 to the running state or the stopped state respectively.

[0089] In a similar respect to inverter 40, the bidirectional chopper 30 also pre-sets the operating priority order of the M chopper units 32. The selection unit 36 ​​selects based on the signal... X and the priority order determine whether to set each chopper unit 32 to an operating state or a stopped state. The selection unit 36 ​​provides the control unit 38 with signals SE1 to SEM indicating the selection results of each of the M chopper units 32.

[0090] The signal SEk, indicating the selection result of the chopper unit 32_k with priority order k, is set to H level when chopper unit 32_k is selected to be in the operating state. When chopper unit 32_k is selected to be in the stopped state, the signal SEk is set to L level. Furthermore, 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.

[0091] The control device 50 may also include a timer 37 for measuring the time during which each chopper unit 32 is set to the operating state. In this case, when the measured operating time for a certain chopper unit 32 reaches a predetermined time, the selection unit 36 ​​can select that chopper unit 32 to the stop state, and select the chopper unit 32 with the highest priority among the stop chopper units 32 to the operating state. In this way, the chopper units 32 set to the operating state are rotated, thereby making the operating time of the M chopper units 32 equal. As a result, the occurrence of failure of each chopper unit 32 can be delayed.

[0092] The control unit 38 is based on the output signals SE1 to SEM from the selection unit 36, the output signal IBf from the current detector CD2, the battery voltage VB, the DC voltage VD, and the detection signal. PF controls multiple switches 31 and multiple chopper units 32.

[0093] Specifically, when the signal SEk is at level L, the control unit 46 stops the operation of the corresponding chopper unit 32_k and disconnects the corresponding switch 31_k.

[0094] On the other hand, when the signal SEk is at level H, the control unit 38 operates the corresponding chopper unit 32_k and turns on the corresponding switch 31_k. (This is in contrast to the signal detection.) When PF is at level L (when AC power supply 80 is intact), the control unit 38 controls the chopper unit 32_k in a manner that makes the battery voltage VB the reference voltage VBR.

[0095] In detecting signals When PF is at level H (when AC power 80 is interrupted), the control unit 38 controls the chopper unit 32_k by using the DC voltage VD of the DC line 20 as the reference voltage VDR. Furthermore, when AC power 80 is interrupted, all M chopper units 32 are selected to operate; therefore, the control unit 38 controls the M chopper units 32 by using the DC voltage VD of the DC line 20 as the reference voltage VDR.

[0096] Figure 6 This is a block diagram showing the structure of the part of the control device 50 related to the control of the converter 10. For example... Figure 6 As shown, the control device 50 includes a load power calculation unit 13, a charging power calculation unit 14, an adder 15, an operating unit calculation unit 16, a selection unit 17, and a control unit 19.

[0097] The load power calculation unit 13 calculates the AC power PL (power consumed by the load 84) consumed by 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 uses the following formula (1) to calculate the consumed power (effective power) PL based on the AC output voltage VO and the load current Io represented by the output signal Iof.

[0098] PL=VOrms×Iorms×cosθ…(1) Here, VOrms represents the effective voltage applied to load 84, Iorms represents the effective current applied to load 84, θ represents the phase difference between the load current Io and the AC output voltage VO, and cosθ represents the power factor.

[0099] The charging power calculation unit 14 calculates the AC power PB (charging power of battery 82) supplied to battery 82 based on the battery voltage VB and the output signal IBf of 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 represented by the output signal IBf.

[0100] Adder 15 calculates the signal PL represents the power consumption PL and is related to the signal PB represents the total power PB+PL, which is the charging power PB. This total power PB+PL is equivalent to the AC power supplied from AC power source 80 to converter 10.

[0101] The unit 16 receives the output signal from the adder 15 and the detection signal from the power failure detector 60. PF. The number of operating units calculation unit 16 detects signals. When PF is at level L (when AC power supply 80 is intact), the appropriate number of operating units Z of converter unit 12 is determined based on the total power PL+PB (AC power supplied from AC power supply 80 to converter 10) represented by the output signal of adder 15.

[0102] Specifically, the unit 16 retrieves information related to the converter 10 from the memory 54. This information includes the number of converter units 12 (total number of units) L contained in the converter 10, the rated output C of each converter unit 12, and the load characteristics of each converter unit 12. The load characteristics of each converter unit 12 represent the relationship between its load rate and operating efficiency. These load characteristics are stored in the memory 54 in the form of a mathematical expression or a mapping.

[0103] like Figure 6 As shown, the operating efficiency of converter unit 12 varies depending on the load rate. Figure 6 In the example, the highest operating efficiency is achieved when the load rate is R2 (%), but if the load rate is lower than R2 (%), the operating efficiency drops sharply.

[0104] When L converter units 12 are operated in parallel, the AC input current Ii is equally shared by the L converter units 12, and the current shared by each converter unit 12 becomes Ii / L. When L converter units 12 are operated in parallel, if the load rate of each converter unit 12 is below R2 (%) and the operating efficiency is low, stopping the operation of L2 converter units 12 can increase the current shared by each converter unit 12 and improve the operating efficiency of each converter unit 12. Therefore, by controlling the number of converter units 12 in operation to achieve a high-efficiency load rate R2 (%), the overall operating efficiency of converter 10 can be improved.

[0105] The operating unit calculation unit 16 calculates the output power R2×C of the converter unit 12 when the load rate is R2 (%) based on the load characteristics of the converter unit 12. Then, the operating unit 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 is equivalent to β% of the rated output L×C of the converter 10, the quotient is (β×L×C) / (R2×C). The operating unit calculation unit 16 determines the appropriate operating unit number Z from the integer closest to this quotient β×L / R2.

[0106] On the other hand, in detecting signals When PF is at level H (when AC power supply 80 is interrupted), the operation count calculation unit 16 sets the appropriate operation count Z of converter unit 12 to 0 (corresponding to...). Figure 3 (S08).

[0107] The operating unit 16 will display a signal indicating the appropriate operating number Z. Z is provided to the selection unit 17. The selection unit 17 is based on the output signal of the operating unit 16. Z, select whether to set L converter units 12 to the running state or the stopped state respectively.

[0108] In one respect, similar to inverter 40 and bidirectional chopper 30, the L converter units 12 in converter 10 are also pre-set with a priority order for operation. Selection unit 17 is based on the signal... Z and the priority order determine whether to set each converter unit 12 to an operating state or a stopped state. 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.

[0109] The signal SEj, indicating the selection result of converter unit 12_j with priority j, is set to H level when converter unit 12_j is selected to operate. When converter unit 12_j is selected to stop, the signal SEj is set to L level. Furthermore, when the appropriate number of operating units Z is equal to the total number of units L, signals SE1 to SEL are all set to H level.

[0110] The control device 50 may also include a timer 18 for measuring the time during which each converter unit 12 is set to the operating state. In this case, when the measured operating time for a certain converter unit 12 reaches a predetermined time, the selection unit 17 can select that converter unit 12 to the stop state, and select the converter unit 12 with the highest priority among the stopped converter units 12 to the operating state. In this way, the converter units 12 set to the operating state are rotated, thereby making the operating time of the L converter units 12 equal. As a result, the occurrence of failure of each converter unit 12 can be delayed.

[0111] The control unit 19 is 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. PF controls multiple switches 11 and multiple converter units 12.

[0112] Specifically, when the signal SEj is at level L, the control unit 19 stops the operation of the corresponding converter unit 12_k and disconnects the corresponding switch 11_j.

[0113] On the other hand, when signal SEj is at level H, control unit 19 operates the corresponding converter unit 12_j and turns on the corresponding switch 11_j. Control unit 19 controls converter unit 12_j in a manner that makes the DC voltage VD of DC line 20 a reference voltage VDR.

[0114] Furthermore, when the AC power supply 80 fails, all L converter units 12 are selected to stop, so the control unit 19 stops the operation of the converter 10.

[0115] Next, refer to Figures 7 to 9 An example of the operation of the uninterruptible power supply device 100 will be explained.

[0116] exist Figures 7 to 9 In the various diagrams, in each power converter of converter 10, bidirectional chopper 30, and inverter 40, the power conversion unit in the operating state is represented by a solid line, and the power conversion unit in the stopped state is represented by a dashed line. Additionally, in each diagram, arrows indicate the flow of electricity.

[0117] Figure 7 This is a diagram illustrating an example of the operation of the uninterruptible power supply device 100 when the AC power supply 80 is functioning properly. Figure 7 In the diagram, load 84 is an electrical device with a low power factor (cosθ). Battery 82 is fully charged.

[0118] Under these circumstances, the power consumption PL of load 84 (PL = VOrms × Iorms) is smaller compared to the AC power output by inverter 40 (apparent power = VOrms × Iorms). Furthermore, since battery 82 is fully charged, the charging power PB required to maintain battery voltage VB at the reference voltage VBR is also smaller. In other words, the AC power supplied from AC power source 80 to converter 10 (total power PB + PL) is also smaller.

[0119] Under such circumstances, relative to the appropriate number of inverter units 42 operating X (e.g., X=3), the appropriate number of converter units 12 operating Z (e.g., Z=1) and the appropriate number of chopper units 32 operating Y (e.g., Y=1) can be reduced.

[0120] In existing uninterruptible power supply (UPS) systems that consist of multiple UPS units connected in parallel, the appropriate number of UPS units to operate is determined based on the load current Io. Therefore, the same number of converter and chopper units are operated as the number of inverter units determined by the load current Io. Consequently, when the load has a low power factor and the battery is fully charged, the number of converter units operating is excessive relative to the amount of AC power supplied from the AC power source, resulting in lower overall converter efficiency. Furthermore, the number of chopper units operating is excessive relative to the amount of battery charging power, leading to lower efficiency of the bidirectional choppers. As a result, there are concerns about reduced power supply efficiency of the UPS system.

[0121] In contrast, in this embodiment, the number of inverter units 42 (X), the number of chopper units 32 (Y), and the number of converter units 12 (Z) can be controlled independently. Therefore, it is possible to operate an appropriate number of inverter units 42 relative to the load current Io, an appropriate number of converter units 12 relative to the AC power supplied from the AC power source 80, and an appropriate number of chopper units 32 required to charge the battery 82. Thus, as... Figure 7 As shown, when the load 84 has a low power factor and the battery 82 is fully charged, the inverter 40, bidirectional chopper 30, and converter 10 can operate with high efficiency. As a result, the power supply efficiency of the uninterruptible power supply device 100 can be improved.

[0122] Figure 8 This is a diagram illustrating the operation of the uninterruptible power supply (UPS) 100 when the AC power supply 80 fails. (Example:) Figure 8As shown, in the event of a power outage of the AC power supply 80, the control device 50 sets the appropriate number of operating units Z of the converter unit 12 to 0, thereby stopping the operation of the converter 10. Additionally, the control device 50 operates all chopper units 32 included in the bidirectional chopper 30 and all inverter units 42 included in the inverter 40.

[0123] In this way, even if the load 84 changes during a power outage of AC power supply 80, AC power can still be stably supplied to the load 84. Therefore, the reliability of the power supply to the load 84 can be maintained.

[0124] Figure 9 This diagram illustrates an example of the operation of the uninterruptible power supply (UPS) 100 when AC power supply 80 is restored. Figure 9 In this case, load 84 is a light load. Battery 82 supplies power to load 84 during a power outage, thereby reducing its energy storage capacity.

[0125] Under these conditions, the AC power output of inverter 40 decreases, and the power consumption PL of load 84 also decreases. On the other hand, because the battery 82 has a low storage capacity, the charging power PB required to maintain the battery voltage VB at the reference voltage VBR increases. Therefore, the AC power supplied from AC power supply 80 to converter 10 (total power PB+PL) also increases.

[0126] Under these conditions, relative to the appropriate number of inverter units 42 operating (X) (e.g., X=1), the appropriate number of converter units 12 operating (Z) (e.g., Z=2) and the appropriate number of chopper units 32 operating (Y) (e.g., Y=3) can be increased. Thus, when the AC power supply 80 is restored, the inverter units 42, operating at an appropriate number relative to the load current Io, can be operated while the battery 82 is rapidly charged to restore its stored capacity.

[0127] [Implementation Method 2] Figure 10 This is a circuit block diagram illustrating the structure of the uninterruptible power supply device according to Embodiment 2. For example... Figure 10 As shown, the uninterruptible power supply device 110 of Embodiment 2 and Figure 1 The difference of the uninterruptible power supply device 100 shown is that it does not have a bidirectional chopper 30.

[0128] In the uninterruptible power supply device 110, the control device 50 is configured to include Figure 4 and Figure 6The control structure is shown. Specifically, when the AC power supply 80 is intact, the control device 50 determines the appropriate number X of inverter units 42 to operate based on the output current (i.e., load current Io) of the inverter 40. Furthermore, the control device 50 determines the appropriate number Z of converter units 12 to operate based on the AC power supplied from the AC power supply 80 to the converter 10.

[0129] When the AC power supply 80 fails, the control device 50 sets the appropriate number Z of operating converter units 12 to 0, thereby stopping the operation of converter 10. In addition, the control device 50 sets the appropriate number X of operating inverter units 42 to the total number of units N, thereby enabling all inverter units 42 contained in inverter 40 to operate.

[0130] Therefore, in embodiment 2, the same effect as in embodiment 1 can also be obtained.

[0131] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of this disclosure is defined not by the foregoing description but by the claims, and is intended to include all modifications equivalent to and within the scope of the claims.

[0132] Explanation of reference numerals in the attached figures 10 Converter; 11, 31, 41; S1~S3 Switches; 12 Converter Unit; 13 Load Power Calculation Unit; 14 Charging Power Calculation Unit; 15 Adder; 16, 35, 44 Operating Unit Calculation Unit; 17, 36, 45 Selection Unit; 18, 37, 48 Timer; 19, 38, 46 Control Unit; 20 DC Line; 22, C1, C2 Capacitors; 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 Failure Detector; 80 AC Power Supply; 82 Battery; 84 Load; 100, 110 Uninterruptible Power Supply Device; CD1~CD3 Current Detectors; T1 AC Input Terminal; T2 DC Terminal; T3 AC output terminals; L1 and L2 reactors; F1 and F2 AC filters.

Claims

1. An uninterruptible power supply device, comprising: The converter converts AC power supplied by an AC power source into DC power and outputs it to a DC line; The inverter converts the DC power supplied from the DC line into AC power and supplies it to the load; and The control device controls the converter and the inverter. An energy storage device is connected to the DC line to store the DC power of the DC line. The converter includes multiple converter units connected in parallel between the AC power supply and the DC line. The inverter includes multiple inverter units connected in parallel between the DC line and the load. When the AC power supply is intact, the control device Based on the inverter's output current, the appropriate number of inverter units to operate is determined. Based on the AC power supplied from the AC power source to the converter, the appropriate number of converter units to operate is determined. To operate the determined appropriate number of inverter units and converter units.

2. The uninterruptible power supply device according to claim 1, wherein, The control device is, Calculate the total power consumption of the load and the charging power supplied from the DC line to the energy storage device. Based on the relationship between the load rate and operating efficiency of the converter unit, the appropriate number of converter units to operate is calculated according to the total power.

3. The uninterruptible power supply device according to claim 1 or 2, wherein, The control device is, Based on the relationship between the load rate and operating efficiency of the inverter unit, the appropriate number of inverter units to operate is calculated according to the output current of the inverter.

4. The uninterruptible power supply device according to claim 1, wherein, When the AC power supply fails, the control device stops the operation of the converter and enables all of the multiple inverter units to operate.

5. The uninterruptible power supply device according to claim 1, wherein, The control device has a timer for measuring the time during which each inverter unit is set to the operating state, and based on the time measured by the timer, the inverter units set to the operating state are rotated.

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

7. The uninterruptible power supply device according to claim 1, wherein, It also has: A bidirectional chopper receives and supplies DC power between the DC line and the energy storage device. The bidirectional chopper is configured to charge the energy storage device with DC power from the DC line when the AC power supply is available. The bidirectional chopper includes multiple chopper units connected in parallel between the DC line and the energy storage device. When the AC power supply is intact, the control device determines the appropriate number of chopper units to operate based on the charging current required to charge the energy storage device.

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

9. The uninterruptible power supply device according to claim 7 or 8, wherein, The bidirectional chopper is configured to supply DC power to the energy storage device when the AC power supply fails. When the AC power supply fails, the control device causes all of the multiple chopper units to operate.

10. The uninterruptible power supply device according to claim 7, wherein, The control device has a timer for measuring the time during which each of the chopper units is set to the operating state, and the chopper units set to the operating state are rotated based on the time measured by the timer.

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