Uninterruptible power supply device

Abstract

An uninterruptible power supply device (10) is connected between an AC power supply (1) and a DC power transmission line (4). An uninterruptible power supply device (10) is provided with a converter (12), a DC bus (14), and a bidirectional chopper (18). A converter (12) converts AC power supplied from an AC power source (1) into DC power. The DC bus (14) supplies the DC power received from the converter (12) to the DC power transmission line (4). The bidirectional chopper (18) receives and supplies DC power between the DC bus (14) and the power storage device (3). The converter (12) includes a plurality of power converters that convert AC power input to the AC terminals into DC power and output the DC power from the DC terminals. The AC terminals of the plurality of power converters are connected in series with the AC power supply (1), and the DC terminals are connected in parallel with the DC bus (14).

Description

Technical Field

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

[0002] For example, International Patent Publication No. 2014 / 132452 (Patent Document 1) discloses an uninterruptible power supply (UPS) device for supplying power to multiple servers installed in a data center or similar location. This UPS device is connected to a low-voltage (400V series) AC power source. The UPS device is configured to include: a converter that converts low-voltage AC power (AC400V) from the AC power source into DC power; and an inverter that converts the DC power from the converter or DC power stored in a battery into low-voltage AC power (AC400V).

[0003] Existing technical documents Patent documents Patent Document 1: International Publication No. 2014 / 132452 Summary of the Invention

[0004] The problem that the invention aims to solve To supply AC power to loads with capacities ranging from tens to hundreds of MVA, multiple uninterruptible power supplies (UPS) are connected in parallel to the load to construct a power system. This power system supplies low-voltage AC power (AC400V) to the load via transmission lines.

[0005] In the aforementioned power system, the large current flowing through the transmission lines raises concerns about increased power loss and voltage drop. Furthermore, the need for multiple transmission lines to handle such large currents leads to larger power systems and increased equipment costs.

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

[0007] Methods for solving problems The uninterruptible power supply (UPS) device disclosed herein is connected between an AC power source and a DC transmission line. The UPS device includes a converter, a DC bus, and a bidirectional chopper. The converter converts AC power supplied from the AC power source into DC power. The DC bus supplies the DC power received from the converter to the DC transmission line. The bidirectional chopper receives and supplies DC power between the DC bus and a power storage device. The converter includes multiple power converters that convert AC power input to AC terminals into DC power and output DC power from the DC terminals. The AC terminals of the multiple power converters are connected in series with the AC power source, and the DC terminals are connected in parallel with the DC bus.

[0008] Invention Effects According to this disclosure, an uninterruptible power supply device capable of miniaturization and high efficiency can be provided. Attached Figure Description

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

[0010] Figure 2 This is a block diagram representing the main circuit structure of the converter.

[0011] Figure 3 It means Figure 2 The circuit diagram shown is of the main circuit structure of the power converter.

[0012] Figure 4 This is a circuit diagram showing the main circuit structure of a bidirectional chopper.

[0013] Figure 5 This is a diagram illustrating an application example of the uninterruptible power supply device according to this embodiment.

[0014] Figure 6 This is a diagram illustrating an application example of the uninterruptible power supply device used in the comparative example.

[0015] Figure 7 This is a diagram illustrating a structural example of a power supply system using the uninterruptible power supply device of this embodiment.

[0016] Figure 8 It means Figure 7 The circuit diagram of the main circuit structure of the converter is shown. Detailed Implementation

[0017] 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.

[0018] Figure 1 This is a circuit block diagram illustrating the structure of the uninterruptible power supply device according to this embodiment. Figure 1 As shown, the uninterruptible power supply (UPS) 10 is connected between the AC power source 1 and the DC transmission line 4. The UPS 10 receives three-phase AC voltage from the AC power source 1 and supplies DC voltage to the DC transmission line 4. However, for the sake of simplicity in the drawings and description, [the following is omitted as the original text is incomplete and cannot be translated]. Figure 1 The circuit diagram shows only one phase.

[0019] In this manual, in accordance with IEC (International Electrotechnical Commission) standards, for AC voltage levels, voltage levels above 230kV are classified as Extra-high Voltage Alternating Current (EHVAC), voltage levels from 35kV to 230kV are classified as High Voltage Alternating Current (HVAC), voltage levels from 1kV to 35kV are classified as Medium Voltage Alternating Current (MVAC), and voltage levels below 1kV are classified as Low Voltage Alternating Current (LVAC).

[0020] In addition, regarding DC, voltage levels exceeding 100kV are classified as high voltage (HVDC: High Voltage Direct Current), voltage levels from 1.5kV to 100kV are classified as medium voltage (MVDC: Medium Voltage Direct Current), and voltage levels below 1.5kV are classified as low voltage (LVDC: Low Voltage Direct Current).

[0021] Furthermore, in Japan, currently, regarding AC voltage, voltage levels above 7kV are classified as Extra High Voltage (EHVAC), voltage levels between 600V and 7kV are classified as High Voltage (HVAC), and voltage levels below 600V are classified as Low Voltage (LVAC). Regarding DC voltage, voltage levels above 7kV are classified as Extra High Voltage (EHVDC), voltage levels between 750V and 7kV are classified as High Voltage (HVDC), and voltage levels below 1.5kV are classified as Low Voltage (LVDC).

[0022] AC power source 1 is a power system that supplies medium-voltage AC power, or a generator that produces medium-voltage AC power. DC transmission line 4 transmits medium-voltage DC power.

[0023] The uninterruptible power supply device 10 includes an input terminal T1, a DC terminal T2, an output terminal T3, switches S1 to S3, a converter 12, current detectors CD1 to CD3, a DC bus 14, a capacitor 16, a bidirectional chopper 18, and a control device 20.

[0024] Input terminal T1 receives AC power of a specified frequency from AC power source 1 via transformer 2. The AC input voltage VI is a medium-voltage AC voltage, and its instantaneous value is detected by control device 20. Based on the instantaneous value of AC input voltage VI, it is determined whether a power outage has occurred. Current detector CD1 detects the AC input current Ii flowing in input terminal T1 and provides a signal Iif representing its detected value to control device 20.

[0025] Output terminal T3 is connected to DC transmission line 4. DC transmission line 4 transmits medium-voltage DC power. Multiple loads 6 are electrically connected to DC transmission line 4. A switch S4 and an inverter 5 are connected in series between DC transmission line 4 and each load 6. By turning on or off the switch S4 connected to each load 6, the load capacity of the uninterruptible power supply 10 changes.

[0026] When switch S4 is in the ON state, inverter 5 converts the medium-voltage DC power supplied from DC transmission line 4 into low-voltage AC power and supplies it to load 6. Load 6 is driven by the low-voltage AC power supplied from inverter 5.

[0027] DC terminal T2 is connected to battery 3. Battery 3 constitutes a "power storage device" for storing DC power. However, a capacitor may also be connected instead of battery 3. The instantaneous value of the inter-terminal voltage VB of battery 3 is detected by control device 20. In the following description, the inter-terminal voltage VB of battery 3 will also be referred to as "battery voltage VB". The battery voltage VB when battery 3 is fully charged is, for example, several kV.

[0028] Switch S1 is connected between input terminal T1 and the AC terminal of converter 12 and is controlled by control device 20. When AC power is normally supplied from AC power source 1 (when AC power source 1 is functioning properly), switch S1 is turned on, supplying AC power from AC power source 1 to converter 12 via switch S1. When AC power is not normally supplied from AC power source 1 (when AC power source 1 is de-energized), switch S1 is turned off, disconnecting AC power source 1 from converter 12.

[0029] Converter 12 is controlled by control device 20. When AC power supply 1 is intact, it converts the medium-voltage AC power from AC power supply 1 into medium-voltage DC power and outputs it to DC bus 14. Converter 12 will be described in detail later.

[0030] Capacitor 16 is connected to DC bus 14 to smooth and stabilize the DC voltage VD of DC bus 14. The instantaneous value of DC voltage VD of DC bus 14 is detected by control device 20.

[0031] When AC power supply 1 is working properly, control device 20 controls converter 12 in such a way that DC voltage VD is used as a reference DC voltage VDR. When AC power supply 1 is interrupted, control device 20 stops the operation of converter 12.

[0032] DC bus 14 is connected to DC terminal T2 via bidirectional chopper 18 and switch S2. Switch S2 is controlled by control device 20. Switch S2 is on when using uninterruptible power supply device 10. Switch S2 is off when maintaining battery 3 or bidirectional chopper 18.

[0033] The bidirectional chopper 18 is controlled by the control device 20. It receives and supplies DC power between the DC bus 14 and the battery 3 by converting DC voltage between the DC bus 14 and the battery 3. The current detector CD2 detects the DC current IB flowing between the battery 3 and the bidirectional chopper 18 and provides a signal IBf indicating its detection value to the control device 20.

[0034] When AC power supply 1 is intact, control device 20 controls bidirectional chopper 18 by making battery voltage VB a reference DC voltage VBR. When AC power supply 1 is de-energized, control device 20 controls bidirectional chopper 18 by making DC voltage VD a reference DC voltage VDR. The bidirectional chopper 18 will be described in detail later.

[0035] DC bus 14 is connected to output terminal T3 via switch S3. Switch S3 is controlled by control device 20. Switch S3 is on when using uninterruptible power supply device 10. Switch S3 is off during maintenance of converter 12.

[0036] The current detector CD3 detects the DC output current Io of the converter 12 and provides a signal Iof representing its detected value to the control device 20. The instantaneous value of the DC output voltage VO applied to the DC transmission line 4 is detected by the control device 20.

[0037] The control device 20 controls switches S1 to S3, converter 12, and bidirectional chopper 18 based on AC input voltage VI, DC output voltage VO, DC voltage VD, battery voltage VB, AC input current Ii, DC current IB, and DC output current Io. Typically, the control device 20 can be composed of at least one microprocessor with a pre-stored program.

[0038] Figure 2 This is a block diagram showing the main circuit structure of converter 12. For example... Figure 2 As shown, converter 12 is configured to include multiple power converters 30 connected between AC nodes 12a, 12b and DC nodes 12c, 12d. The multiple power converters 30 have the same structure.

[0039] Each power converter 30 includes AC terminals 30a and 30b, DC terminals 30c and 30d, an AC / DC converter 32, a DC / DC converter 34, and capacitors C1 and C2.

[0040] The AC terminals 30a and 30b of multiple power converters 30 are connected in series between the AC nodes 12a and 12b of converter 12. Specifically, the AC terminal 30a of the first power converter 30 is connected to the AC node 12a, and the AC terminal 30b of the first power converter 30 is connected to the AC terminal 30a of the second power converter 30. The AC terminal 30b of the second power converter 30 is connected to the AC terminal 30a of the third power converter 30.

[0041] Thus, the AC terminal 30a of the i-th power converter 30 is connected to the AC terminal 30b of the (i-1)-th power converter 30, and the AC terminal 30b of the i-th power converter 30 is connected to the AC terminal 30a of the (i+1)-th power converter 30. The AC terminal 30b of the N-th power converter 30 is connected to the AC node 12b. N represents the number of power converters 30, and i is an integer greater than 2 and less than N-1. That is, the AC terminals 30a and 30b of multiple power converters 30 are connected in series with the AC power source 1 via AC nodes 12a and 12b.

[0042] The DC terminals 30c and 30d of each power converter 30 are connected to the DC nodes 12c and 12d. That is, the DC terminals 30c and 30d of multiple power converters 30 are connected in parallel to the DC bus 14 via the DC nodes 12c and 12d.

[0043] In each power converter 30, the AC / DC converter 32 converts the AC power input to the AC terminals 30a and 30b into DC power. By making the AC side of the power converter 30 DC multi-stage, the AC voltage applied to the AC / DC converter 32 can be reduced, so the AC / DC converter 32 can use semiconductor switching elements with low withstand voltage and low on-resistance.

[0044] DC / DC converter 34 transmits the DC power generated by AC / DC converter 32 to DC terminals 30c and 30d. DC / DC converter 34 is an isolated DC / DC converter.

[0045] Capacitor C1 is connected between DC buses PL1 and NL1, which connect AC / DC converter 32 and DC / DC converter 34, to smooth and stabilize the DC voltage between DC buses PL1 and NL1. Capacitor C2 is connected between DC buses PL2 and NL2, which connect DC / DC converter 34 to DC terminals 30c and 30d, to smooth and stabilize the DC voltage between DC buses PL2 and NL2.

[0046] Figure 3 It means Figure 2 The circuit diagram of the main circuit structure of the power converter 30 is shown. Figure 3 As shown, the power converter 30 uses a semiconductor transformer (SST: Solid State Transformer). SST utilizes a high-frequency transformer for insulation and voltage transformation, which can significantly reduce the size and weight of the transformer compared to commercial frequency transformers.

[0047] like Figure 3 As shown, the AC / DC converter 32 includes semiconductor switching elements SW1 to SW4. The semiconductor switching elements SW1 to SW4 constitute a single-phase full-bridge circuit. Driven by a gate signal from the control device 20, the single-phase full-bridge circuit converts the AC power input to AC terminals 30a and 30b into DC power and outputs it to DC buses PL1 and NL1. Capacitor C1 smooths the DC voltage between DC buses PL1 and NL1.

[0048] The isolated DC / DC converter 34 is a DAB (Dual Active Bridge) converter. Specifically, the isolated DC / DC converter 34 includes a primary-side bridge circuit 35, a secondary-side bridge circuit 36, and a high-frequency transformer Tr.

[0049] The primary-side bridge circuit 35 constitutes a single-phase full-bridge circuit. Specifically, it includes semiconductor switching elements SW5 to SW8 connected between the DC positive bus PL1 and the DC negative bus NL1. Semiconductor switching elements SW5 and SW6 are connected in series between the DC positive bus PL1 and the DC negative bus NL1 via node N1a, which is connected to AC terminal 35a. Semiconductor switching elements SW7 and SW8 are connected in series between the DC positive bus PL1 and the DC negative bus NL1 via node N1b, which is connected to AC terminal 35b.

[0050] Similarly, the secondary-side bridge circuit 36 ​​constitutes a single-phase full-bridge circuit. Specifically, it includes semiconductor switching elements SW9 to SW12 connected between the DC positive bus PL2 and the DC negative bus NL2. Semiconductor switching elements SW9 and SW10 are connected in series between the DC positive bus PL2 and the DC negative bus NL2 via node N2a, which is connected to AC terminal 36a. Semiconductor switching elements SW11 and SW12 are connected in series between the DC positive bus PL2 and the DC negative bus NL2 via node N2b, which is connected to AC terminal 36b.

[0051] Semiconductor switching elements SW1 to SW12 each have a self-extinguishing switching element and a diode. The switching element can be composed of any self-extinguishing element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The diode is connected in anti-parallel with the switching element to form a freewheeling diode (FWD).

[0052] The high-frequency transformer Tr has a primary winding connected between AC terminals 35a and 35b of the primary side bridge circuit 35, and a secondary winding connected between AC terminals 36a and 36b of the secondary side bridge circuit 36.

[0053] The control device 20 controls the power conversion in the isolated DC / DC converter 34. Specifically, the control device 20 generates gate signals for controlling the on / off switching of semiconductor switching elements SW5 to SW12 based on the output signals of current sensors and voltage sensors (not shown).

[0054] The isolated DC / DC converter 34 converts the DC power input from DC buses PL1 and NL1 into AC power via the primary-side bridge circuit 35. This AC power is then transmitted to the secondary-side bridge circuit 36 ​​via the high-frequency transformer Tr. The secondary-side bridge circuit 36 ​​converts the transmitted AC power back into DC power and outputs it to DC buses PL2 and NL2. Thus, the DC power generated by the AC / DC converter 32 is transmitted to the DC bus 14 via DC terminals 30c and 30d.

[0055] Figure 4 This is a circuit diagram illustrating an example of the main circuit structure of the bidirectional chopper 18. For example... Figure 4 As shown, the bidirectional chopper 18 is a non-insulated bidirectional chopper. Specifically, the bidirectional chopper 18 is configured to include semiconductor switching elements SW13 and SW14, a reactor L1, and a capacitor C3.

[0056] Semiconductor switching elements SW13 and SW14 are connected in series between high-voltage side nodes 18a and 18b. Reactor L1 is connected between the connection point of semiconductor switching elements SW13 and SW14 and low-voltage side node 18c. Capacitor C3 is connected between high-voltage side nodes 5a and 5b to stabilize the DC voltage VD between high-voltage side nodes 5a and 5b.

[0057] When AC power supply 1 is working properly, semiconductor switching element SW3 switches on and off at a predetermined frequency, storing DC power from DC bus 14 in battery 3. When AC power supply 1 is interrupted, semiconductor switching element SW4 switches on and off at a predetermined frequency, supplying DC power from battery 3 to DC bus 14.

[0058] Next, an application example of the uninterruptible power supply device 10 of this embodiment will be described.

[0059] Figure 5 This is a diagram illustrating an application example of the uninterruptible power supply device 10 according to this embodiment. For example... Figure 5 As shown, the uninterruptible power supply device 10 of this embodiment receives medium-voltage AC power from the AC power source 1. The converter 12 converts the medium-voltage AC power into medium-voltage DC power and supplies it to the DC transmission line 4.

[0060] like Figure 2 and Figure 3 As described above, converter 12 is configured as a plurality of power converters 30, including an AC side connected in series with AC power supply 1 and a DC side connected in parallel with DC bus 14. According to the above structure, converter 12 is capable of generating medium-voltage DC power from medium-voltage AC power. The medium-voltage DC power transmitted in DC transmission line 4 is converted into low-voltage (e.g., 415V) AC power by inverter 5 and supplied to load 6.

[0061] Figure 6 This is a diagram illustrating an application example of the comparative example uninterruptible power supply device 10A. For example... Figure 6 As shown, the comparative example uninterruptible power supply device 10A is a conventional uninterruptible power supply device, which includes a converter 12, a bidirectional chopper 18, a DC bus 14, a capacitor 16, and an inverter 22A.

[0062] An uninterruptible power supply (UPS) 10A receives low-voltage (e.g., 480V) AC power from an AC power source 1. A converter 12 converts the low-voltage (e.g., 480V) AC power to low-voltage (e.g., 600V) DC power and outputs it to a DC bus 14. An inverter 22A converts the low-voltage (e.g., 600V) DC power to low-voltage (e.g., 480V) AC power and supplies it to an AC transmission line 7. The low-voltage (e.g., 480V) AC power transmitted in the AC transmission line 7 is stepped down to low-voltage (e.g., 415V) AC power by a transformer 8 and supplied to a load 6.

[0063] Compared with the uninterruptible power supply device 10A of the comparative example, the uninterruptible power supply device 10 of this embodiment does not have an inverter 22A, thus enabling the device size to be miniaturized.

[0064] Furthermore, the uninterruptible power supply 10 generates medium-voltage direct current from medium-voltage alternating current and supplies it to the direct current transmission line 4. Therefore, compared to the uninterruptible power supply 10A that supplies low-voltage alternating current, the current flowing in the direct current transmission line 4 can be reduced. As a result, power loss and voltage drop in the direct current transmission line 4 can be reduced. In addition, since the number of direct current transmission lines 4 can be reduced, the power supply system can be miniaturized and equipment costs can be reduced.

[0065] Figure 7 This is a diagram illustrating a structural example of a power system using the uninterruptible power supply device 10 of this embodiment. The power system can, for example, be applied to large-scale data centers.

[0066] like Figure 7 As shown, the power supply system includes multiple uninterruptible power supply (UPS) units 10 connected in parallel between the AC power source 1, 1A and the DC transmission line 4. The basic structure of each UPS unit 10 is similar to... Figures 1 to 4 The structure of the uninterruptible power supply device 10 described herein is the same. Figure 7 The uninterruptible power supply device 10 shown differs in that it includes a switch S5 instead of a switch S1, and has a transformer 2.

[0067] Switch S5 is controlled by a control device (not shown) and is configured to connect either of the two AC power sources 1 and 1A to the primary side of transformer 2. AC power source 1 is, for example, a commercial AC power source, and AC power source 1A is, for example, a generator. That is, the uninterruptible power supply 10 is configured to switch between the commercial AC power source and the generator as an AC power source.

[0068] like Figure 7 As shown, converter 12 receives 13.8kV (medium voltage) AC power from AC power source 1 and 1A via switch S5 and transformer 2. The AC power is 10MVA.

[0069] Figure 8 It shows Figure 7 The main circuit structure of converter 12 is shown. Figure 2 and Figure 3 As described, converter 12 is configured to include multiple power converters 30. Converter 12 converts 13.8 kV AC power (10 MVA) into 1.5 kV (medium voltage) DC power and supplies it to DC transmission line 4. DC transmission line 4 is approximately 1,000 feet long. The 1.5 kV DC power transmitted in DC transmission line 4 is converted to 415 V (low voltage) AC power by inverter 5 and supplied to the load.

[0070] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. The scope of this disclosure is defined not by the foregoing description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0071] Explanation of reference numerals in the attached figures 1. 1A AC power supply; 2. 8 transformer; 3. Battery; 4. DC transmission line; 5. 22A inverter; 6. Load; 7. AC transmission line; 10. 10A uninterruptible power supply; 12. Converter; 14. PL1, NL1, PL2, NL2 DC bus; 16. C1~C3 capacitor; 18. Bidirectional chopper; 20. Control device; 30. Power converter; 32. AC / DC converter; 34. DC / DC converter; 35. Primary side bridge circuit; 36. Secondary side bridge circuit; SW1~SW14 semiconductor switching elements; T1 input terminal; T2 DC terminal; T3 output terminal; Tr high-frequency transformer; S1~S5 switches.

Claims

1. An uninterruptible power supply device, connected between an AC power source and a DC transmission line, comprising: The converter converts the AC power supplied from the AC power source into DC power. The DC bus supplies DC power received from the converter to the DC transmission line; and A bidirectional chopper receives and supplies DC power between the DC bus and the power storage device. The converter includes multiple power converters that convert AC power input to AC terminals into DC power and output it from DC terminals. The plurality of power converters are configured such that the AC terminals are connected in series with the AC power supply, and the DC terminals are connected in parallel with the DC bus.

2. The uninterruptible power supply device according to claim 1, wherein, The plurality of power converters respectively include: An AC / DC converter converts the AC power input to the AC terminals into DC power; and An isolated DC / DC converter that transmits DC power from the AC / DC converter to the DC terminal.

3. The uninterruptible power supply device according to claim 2, wherein, The isolated DC / DC converter is a DAB converter, i.e., a dual active bridge converter.

4. The uninterruptible power supply device according to any one of claims 1 to 3, wherein, The AC power source is a power system or generator that supplies medium-voltage AC power. The power storage device is configured to store medium-voltage DC power. When the AC power supply is intact, the converter will convert the medium-voltage AC power supplied by the AC power supply into medium-voltage DC power and supply it to the DC bus. When the AC power supply fails, the converter stops operating, and the bidirectional chopper supplies the medium-voltage DC power from the power storage device to the DC bus.

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