Uninterruptible power supply device

Abstract

This uninterruptible power supply device (100) is provided with: an AC power supply line (2) for supplying AC power to an AC load (40); a switch (1) having a first terminal connected to an AC power supply (10) and a second terminal connected to the AC power supply line (2); and a DC power supply line (4) for supplying DC power to a DC load (42). An electric energy storage device (20) is connected to the DC power supply line (4). The uninterruptible power supply device (100) further comprises a bidirectional power converter (3) that bidirectionally converts power between the AC power supply line (2) and the DC power supply line (4).

Description

Uninterruptible power supply device

[0001] The present disclosure relates to an uninterruptible power supply device, and particularly to an uninterruptible power supply device that supplies power in parallel to an AC load and a DC load.

[0002] For example, Japanese Patent Application Laid-Open No. 2014-7929 (Patent Document 1) discloses an uninterruptible power supply device configured to supply AC power generated from an AC power source to an AC load. In this uninterruptible power supply device, the converter converts the AC power from the AC power source into DC power. The inverter converts the DC power from the converter into AC power of a constant frequency and a constant voltage, and supplies the converted AC power to the AC load.

[0003] When an abnormality (such as a power outage or a momentary voltage drop) occurs in the AC power source, the operation of the converter is stopped, and DC power is supplied from the power storage device to the inverter. Thereby, when an abnormality occurs in the AC power source, the uninterruptible power supply device supplies AC power to the AC load without interruption.

[0004] Japanese Patent Application Laid-Open No. 2014-7929

[0005] When supplying power to a DC load using the above uninterruptible power supply device, generally, the AC power generated by the inverter is converted into DC power suitable for the DC load by an AC adapter provided outside the device, and the converted DC power is supplied to the DC load. However, in the above configuration, power losses occur in each of the inverter and the AC adapter, so there is a possibility that the efficiency may be reduced.

[0006] With the explosive spread of AI (Artificial Interface) and IoT (Internet Of Things) technologies, the demand for data centers that support these technologies has been rapidly expanding. In large-scale data centers, the increase in power consumption has become a major problem. The main devices used in data centers are servers, power supply devices, storage, and air conditioning equipment, and the servers account for most of the power consumption of the data center. Since the servers are DC loads, when the above uninterruptible power supply device is applied to the power supply device of a data center, there is a concern that the power losses in the inverter and the AC adapter will increase significantly.

[0007] Here, if the uninterruptible power supply (UPS) is configured to supply DC power generated by a converter directly to the DC load without going through an inverter and AC adapter, power loss can be suppressed. However, in data centers, it is necessary to supply AC power to AC loads such as air conditioning equipment without interruption, in parallel with the power supply to DC loads such as servers. In other words, there is a need to realize an uninterruptible power supply that can supply power to AC and DC loads in parallel with high efficiency.

[0008] Therefore, the primary object of this disclosure is to provide an uninterruptible power supply that can supply power to AC and DC loads in parallel with high efficiency.

[0009] An uninterruptible power supply (UPS) according to this disclosure comprises an AC power supply line for supplying AC power to an AC load, a switch whose first terminal is connected to the AC power supply and whose second terminal is connected to the AC power supply line, and a DC power supply line for supplying DC power to a DC load. An electrical energy storage device is connected to the DC power supply line. The UPS further comprises a bidirectional power converter for converting power bidirectionally between the AC power supply line and the DC power supply line.

[0010] According to this disclosure, it is possible to provide an uninterruptible power supply that can supply power to AC and DC loads in parallel with high efficiency.

[0011] This is a circuit block diagram showing the configuration of an uninterruptible power supply according to Embodiment 1. This is a block diagram showing the configuration of the control device. This is a diagram illustrating the operation of the uninterruptible power supply when the AC power supply is healthy. This is a diagram illustrating the operation of the uninterruptible power supply when the AC power supply is abnormal. This is a diagram illustrating other operations of the uninterruptible power supply when the AC power supply is healthy. This is a circuit block diagram showing another configuration example of a bidirectional power converter. This is a diagram showing an example of a switch configuration. This is a circuit block diagram showing the configuration of an uninterruptible power supply according to Embodiment 2. This is a block diagram showing the configuration of the control device. This is a diagram illustrating the operation of the uninterruptible power supply when the AC power supply is healthy. This is a diagram illustrating other operations of the uninterruptible power supply when the AC power supply is healthy. This is a diagram illustrating the first operation of the uninterruptible power supply when the AC power supply is abnormal. This is a diagram illustrating the second operation of the uninterruptible power supply when the AC power supply is abnormal. This is a diagram illustrating the third operation of the uninterruptible power supply when the AC power supply is abnormal.

[0012] Embodiments of this disclosure will be described in detail below 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 descriptions will not be repeated in principle.

[0013] [Embodiment 1] Figure 1 is a circuit block diagram showing the configuration of an uninterruptible power supply according to Embodiment 1. As shown in Figure 1, the uninterruptible power supply 100 is connected between the AC power supply 10 and the load equipment 40 and 42. The AC power supply 10 is a power system that supplies AC power, or a generator that generates AC power. The load equipment 40 is an AC load driven by AC power. The load equipment 42 is a DC load driven by DC power. The number of each of the load equipment 40 and 42 may be one or more.

[0014] The uninterruptible power supply (UPS) 100 receives a three-phase AC voltage from the AC power supply 10 and supplies the three-phase AC voltage to the load equipment 40, as well as a DC voltage to the load equipment 42. However, for the sake of simplicity in the drawings and explanations, only a single-phase circuit is shown in Figure 1.

[0015] The uninterruptible power supply (UPS) 100 includes an input terminal T1, a DC terminal T2, and output terminals T3 and T4. The input terminal T1 receives AC power of a predetermined frequency from the AC power supply 10. The instantaneous value of the AC input voltage VI appearing at the input terminal T1 is detected by the control circuit 5. Based on the instantaneous value of the AC input voltage VI, it is determined whether or not an abnormality has occurred in the AC power supply 10.

[0016] The DC terminal T2 is connected to the electrical energy storage device 20. The electrical energy storage device 20 stores DC power. The electrical energy storage device 20 is, for example, a rechargeable secondary battery or a capacitor.

[0017] The output terminal T3 is connected to the load equipment 40. The load equipment 40 is an AC load and is driven by AC power supplied from the output terminal T3. The load equipment 40 includes, for example, air conditioning equipment installed in a data center.

[0018] The output terminal T4 is connected to the load equipment 42. The load equipment 42 is a DC load and is driven by DC power supplied from the output terminal T4. The load equipment 42 includes, for example, a server installed in a data center.

[0019] The uninterruptible power supply 100 further comprises a switch 1, an AC power supply line 2, a bidirectional power converter 3, a DC power supply line 4, a current detector CD 1, and control circuits 5 and 6.

[0020] Switch 1 has its first terminal connected to input terminal T1 and its second terminal connected to AC power supply line 2. Switch 1 is controlled by control circuit 5. When AC power is supplied normally from AC power source 10 (when AC power source 10 is healthy), switch 1 is turned on, and AC power is supplied from AC power source 10 to AC power supply line 2 via switch 1. When AC power is not supplied normally from AC power source 10 (when AC power source 10 is abnormal), switch 1 is turned off, and the connection between AC power source 10 and AC power supply line 2 is interrupted.

[0021] The AC power supply line 2 is installed between the second terminal and output terminal T3 of the switch 1 and transmits AC power. The instantaneous value of the AC voltage VAC of the AC power supply line 2 is detected by the control circuit 6.

[0022] The AC node 3a of the bidirectional power converter 3 is connected to the AC power supply line 2, and its DC node 3b is connected to the DC power supply line 4. The bidirectional power converter 3 is controlled by a control circuit 6 and converts power bidirectionally between the AC power supply line 2 and the DC power supply line 4. Specifically, the bidirectional power converter 3 is composed of a reactor L1, a capacitor C1, and a bidirectional AC / DC converter 30.

[0023] The reactor L1 and the bidirectional AC / DC converter 30 are connected in series between the AC node 3a and the DC node 3b. Capacitor C1 is connected to the AC node 3a. The bidirectional AC / DC converter 30 is a well-known type including multiple semiconductor switching elements and multiple diodes, and is controlled by the control circuit 6, for example, using PWM (Pulse Width Modulation). By turning each semiconductor switching element in the bidirectional AC / DC converter 30 on and off at a predetermined frequency, AC power can be converted to DC power, and conversely, DC power can be converted to AC power.

[0024] When the AC power supply 10 is functioning correctly, the bidirectional AC / DC converter 30 converts the AC power supplied from the AC power supply 10 via the switch 1 and the AC power supply line 2 into DC power and outputs it to the DC power supply line 4. When the AC power supply 10 malfunctions, the bidirectional AC / DC converter 30 converts the DC power supplied from the electrical energy storage device 20 to the DC power supply line 4 into AC power and outputs it to the AC power supply line 2. This AC power is supplied to the load equipment 40 via the AC power supply line 2. The current detector CD1 detects the AC current IAC flowing through the reactor L1 and outputs a signal IACf indicating the detected value to the control circuit 6.

[0025] The reactor L1 and capacitor C1 constitute an AC filter. The AC filter is a low-pass filter that allows commercial frequency current to pass through and blocks the switching frequency current generated by the bidirectional AC / DC converter 30. In other words, the AC filter converts the output voltage of the bidirectional AC / DC converter 30 into a sinusoidal AC voltage VAC.

[0026] The DC power supply line 4 is installed between the DC node 3b and the output terminal T4 of the bidirectional power converter 3 and transmits DC power. The instantaneous value of the DC voltage VDC of the DC power supply line 4 is detected by the control circuit 6. An electrical energy storage device 20 is connected to the DC power supply line 4 via the DC terminal T2. The electrical energy storage device 20 exchanges DC power with the DC power supply line 4.

[0027] The control circuit 5 controls the switch 1 based on the AC input voltage VI. The control circuit 5 generates a switch status signal φSW indicating the state of the switch 1 and outputs it to the control circuit 6.

[0028] The control circuit 6 controls the bidirectional power converter 3 based on a switch status signal φSW, an AC voltage VAC, a DC voltage VDC, an AC current IAC, etc. Typically, the control circuits 5 and 6 can be configured by at least one microprocessor with a predetermined program pre-stored. In the example of Figure 1, the control circuit 6 is separate from the control circuit 5, but works in conjunction with the control circuit 5 to provide the functions described herein. That is, the control circuits 5 and 6 constitute a "control device". The control circuits 5 and 6 may also be configured to be provided as an integrated unit.

[0029] Figure 2 is a block diagram showing the configuration of control circuits 5 and 6. As shown in Figure 2, control circuit 5 includes an abnormality detector 50 and a switch control unit 52. Control circuit 6 includes an AC / DC control unit 7, a DC / AC control unit 8, and a switching circuit 9.

[0030] The abnormality detector 50 determines whether or not an abnormality has occurred in the AC power supply 10 based on the AC input voltage VI that appears at the input terminal T1, and outputs an abnormality detection signal φF indicating the determination result to the switch control unit 52. If the AC input voltage VI supplied from the AC power supply 10 is within the normal range, the abnormality detector 50 determines that the AC power supply 10 is healthy and sets the abnormality detection signal φF to the deactivation level "H". If the AC input voltage VI is outside the normal range, the abnormality detector 50 determines that an abnormality has occurred in the AC power supply 10 and sets the abnormality detection signal φF to the activation level "L".

[0031] The switch control unit 52 controls the switch 1 based on the abnormality detection signal φF from the abnormality detector 50. When the abnormality detection signal φF is at the "H" level (when the AC power supply 10 is healthy), the switch control unit 52 turns on the switch 1. When the abnormality detection signal φF is at the "L" level (when the AC power supply 10 is abnormal), the switch control unit 52 turns off the switch 1.

[0032] The switch control unit 52 outputs a switch status signal φSW to the control circuit 6, which indicates the state of switch 1. The switch status signal φSW is set to "H" level when switch 1 is ON (when the AC power supply 10 is healthy) and to "L" level when switch 1 is OFF (when the AC power supply 10 is abnormal).

[0033] The AC / DC control unit 7 is a control unit for controlling the AC / DC conversion operation in the bidirectional power converter 3. The AC / DC control unit 7 controls the AC / DC conversion operation so that the DC voltage VDC of the DC power supply line 4 becomes the reference DC voltage VDCr, and the phase of the input current (AC current IAC) and the AC voltage VAC of the bidirectional power converter 3 matches (i.e., the input power factor becomes 1). Specifically, the AC / DC control unit 7 includes subtractors 71, 75, a voltage control unit 72, a multiplier 73, a sine wave generator 74, a current control unit 76, an adder 77, and a PWM circuit 78.

[0034] The subtractor 71 calculates the deviation ΔVDC = VDCr - VDC between the reference DC voltage VDCr and the DC voltage VDC. The voltage control unit 72 calculates a current command value I* to control the current flowing to the AC side of the bidirectional power converter 3 so that the deviation ΔVDC becomes 0. The voltage control unit 72 calculates the current command value I* by, for example, performing a proportional or proportional-integral operation on the deviation ΔVDC.

[0035] The sine wave generator 74 outputs a three-phase sine wave signal that is in phase with each phase of the AC input voltage VI (three-phase AC voltage) of the AC power supply 10. The three-phase sine wave signal is constantly converted to a current command value I* by the multiplier 73. This generates a three-phase current command value IAC1* that is in phase with the AC input voltage VI (three-phase AC voltage) of the AC power supply 10.

[0036] The subtractor 75 calculates the deviation ΔIAC between the current command value IAC1* and the AC current IAC detected by the current detector CD1. The current control unit 76 generates a voltage command value VACa* as the voltage to be applied to the reactor L1 so that the deviation ΔIAC becomes 0. The current control unit 76 calculates the voltage command value VACa* by, for example, performing a proportional or proportional-integral operation on the deviation ΔIAC.

[0037] The adder 77 adds the voltage command value VACa* and the AC voltage VAC to generate the voltage command value VAC*. The PWM circuit 78 generates a signal to drive multiple semiconductor switching elements included in the bidirectional AC / DC converter 30 based on the voltage command value VAC*. The signal generated by the PWM circuit 78 is supplied to the first input terminal of the switching circuit 9.

[0038] The DC / AC control unit 8 is a control unit for controlling the DC / AC conversion operation in the bidirectional power converter 3. The DC / AC control unit 8 controls the DC / AC conversion operation so that the AC voltage VAC becomes the reference AC voltage VACr. Specifically, the DC / AC control unit 8 includes subtractors 81, 83, a voltage control unit 82, a current control unit 84, an adder 85, and a PWM circuit 86.

[0039] The subtractor 81 calculates the deviation ΔVAC = VACr - VAC between the reference AC voltage VACr and the AC voltage VAC. The reference AC voltage VACr consists of three sinusoidal signals corresponding to the three-phase voltage command values.

[0040] The voltage control unit 82 calculates a current command value IAC2* to control the current flowing to the AC side of the bidirectional power converter 3 so that the deviation ΔVAC becomes 0. The voltage control unit 72 calculates the current command value IAC2* by, for example, performing a proportional or proportional-integral operation on the deviation ΔVAC.

[0041] The subtractor 83 calculates the deviation ΔIAC between the current command value IAC2* and the alternating current IAC detected by the current detector CD1. The current control unit 76 generates a voltage command value VACa* as the voltage to be applied to the reactor L1 such that the deviation ΔIAC becomes zero. The current control unit 84 calculates the voltage command value VACa*, for example, by performing proportional calculation or proportional-integral calculation on the deviation ΔIAC.

[0042] The adder 85 adds the voltage command value VACa* and the alternating voltage VAC to generate a voltage command value VAC*. The PWM circuit 86 generates a signal for driving a plurality of semiconductor switching elements included in the bidirectional AC / DC converter 30 based on the voltage command value VAC*. The signal generated by the PWM circuit 86 is supplied to the second input terminal of the switching circuit 9.

[0043] The switching circuit 9 is provided between the AC / DC control unit 7 and the DC / AC control unit 8, and the bidirectional power converter 3. The switching circuit 9 supplies either the output signal of the AC / DC control unit 7 or the output signal of the DC / AC control unit 8 to the bidirectional power converter 3 based on the switch state signal φSW from the control circuit 5. Specifically, when the switch state signal φSW is at the "H" level (when the AC power supply 10 is normal), the switching circuit 9 supplies the output signal of the AC / DC control unit 7 to the bidirectional power converter 3. Thereby, when the AC power supply 10 is normal, the AC / DC conversion operation in the bidirectional power converter 3 is controlled so that the DC voltage VDC on the DC power supply line 4 becomes the reference DC voltage VDCr.

[0044] When the switch state signal φSW is at the "L" level (when the AC power supply 10 is abnormal), the switching circuit 9 supplies the output signal of the DC / AC control unit 8 to the bidirectional power converter 3. Thereby, when the AC power supply 10 is abnormal, the DC / AC conversion operation in the bidirectional power converter 3 is controlled so that the alternating voltage VAC on the AC power supply line 2 becomes the reference alternating voltage VACr.

[0045] Next, the operation of the uninterruptible power supply device 100 according to Embodiment 1 will be described. FIG. 3 is a diagram for explaining the operation of the uninterruptible power supply device 100 when the AC power supply 10 is normal. In FIG. 3, the path through which power flows is indicated by arrows.

[0046] As shown in FIG. 3, when the AC power supply 10 is normal, the control circuit 5 turns on the switch 1. The AC power supplied from the AC power supply 10 is supplied to the AC power supply line 2 via the switch 1. The AC power supply line 2 supplies AC power to the load equipment 40 and also supplies AC power to the bidirectional power converter 3.

[0047] The bidirectional power converter 3 converts the AC power from the AC power supply line 2 into DC power and supplies it to the DC power supply line 4. The control circuit 6 controls the AC / DC conversion operation in the bidirectional power converter 3 so that the DC voltage VDC of the DC power supply line 4 becomes the reference DC voltage VDCR.

[0048] The DC power supply line 4 supplies DC power to the load equipment 42. The surplus power of the DC power generated by the bidirectional power converter 3 is stored in the electrical energy storage device 20.

[0049] FIG. 4 is a diagram for explaining the operation of the uninterruptible power supply device 100 when the AC power supply 10 is abnormal. In FIG. 4, the path through which power flows is indicated by an arrow.

[0050] As shown in FIG. 4, when the AC power supply 10 is abnormal, the control circuit 5 cuts off the connection between the AC power supply 10 and the AC power supply line 2 by turning off the switch 1.

[0051] The DC power supply line 4 receives DC power supply from the electrical energy storage device 20. The DC power supply line 4 supplies DC power to the load equipment 42 and also supplies DC power to the bidirectional power converter 3.

[0052] The bidirectional power converter 3 converts the DC power of the electrical energy storage device 20 into AC power and supplies it to the AC power supply line 2. The control circuit 6 controls the DC / AC conversion operation in the bidirectional power converter 3 so that the AC voltage VAC of the AC power supply line 2 becomes the reference AC voltage VACR. The AC power supply line 2 supplies the AC power generated by the bidirectional power converter 3 to the load equipment 42.

[0053] In Figure 3, a configuration was described in which, when the AC power supply 10 is functioning properly, the uninterruptible power supply 100 supplies AC power from the AC power supply 10 to the load equipment 40 and the bidirectional power converter 3. However, the uninterruptible power supply 100 may also be configured to operate in grid-connected mode, exchanging power with the AC power supply 10.

[0054] Figure 5 illustrates other operations of the uninterruptible power supply 100 when the AC power supply 10 is functioning properly. In Figure 5, the paths through which power flows are indicated by arrows.

[0055] As shown in Figure 5, the DC power supply line 4 receives DC power from the electrical energy storage device 20. The DC power supply line 4 supplies DC power to the load equipment 42 and also supplies DC power to the bidirectional power converter 3.

[0056] The bidirectional power converter 3 converts the DC power from the electrical energy storage device 20 into AC power and supplies it to the AC power supply line 2. If the output power of the bidirectional power converter 3 is greater than the power consumption of the load equipment 40, the surplus power is supplied to the AC power source 10. Conversely, if the output power of the bidirectional power converter 3 is less than the power consumption of the load equipment 40, the insufficient power is supplied from the AC power source 10 to the load equipment 40.

[0057] The control circuit 6 controls the bidirectional power converter 3 to generate an AC voltage VAC with the same amplitude and frequency as the AC input voltage VI. For example, in the AC / DC control unit 7, a voltage command value VACa* corresponding to the power to be supplied to the AC power supply line 2 is generated by the current control unit 76, and this voltage command value VACa* and the AC voltage VAC are added by the adder 77 to generate a voltage command value VAC*. Then, based on the voltage command value VAC*, a signal for driving the bidirectional AC / DC converter 30 is generated by the PWM circuit 78, and the bidirectional power converter 3 is driven by this signal.

[0058] In this way, by operating the uninterruptible power supply 100 in sync with the AC power supply 10 when the AC power supply 10 is functioning properly, the electricity stored in the electrical energy storage device 20 can be effectively utilized.

[0059] To achieve the above-described operation, it is preferable to select the various electrical components included in the uninterruptible power supply 100 based on the following guidelines.

[0060] (1) Bidirectional power converter 3 When the AC power supply 10 is functioning properly (see Figure 2), the bidirectional power converter 3 generates DC power to drive the load equipment 42 and charging power for the electrical energy storage device 20 based on the AC power from the AC power supply 10. In order to operate the load equipment 42 stably, the capacity of the bidirectional power converter 3 must be greater than the capacity of the load equipment 42.

[0061] In the event of an abnormality in the AC power supply 10 (see Figure 3), the bidirectional power converter 3 generates AC power to drive the load equipment 40 based on the DC power of the electrical energy storage device 20. In order to operate the load equipment 40 stably, the capacity of the bidirectional power converter 3 must be greater than the capacity of the load equipment 40.

[0062] To meet these requirements, it is desirable to select the capacity of the bidirectional power converter 3 based on the larger of the two load equipment 40 and 42. However, if load equipment 40 is air conditioning equipment within the data center and load equipment 42 is servers within the data center, the capacity of load equipment 42 is significantly larger than that of load equipment 40. In such cases, the capacity of the bidirectional power converter 3 is selected based on the capacity of load equipment 42. This allows the bidirectional power converter 3 to supply power to load equipment 40 and 42 with a size that is substantially matched to the capacity of load equipment 42. Therefore, the size of the device can be reduced compared to a configuration where a power converter is provided for each of the load equipment 40 and 42.

[0063] In the example shown in Figure 1, the bidirectional power converter 3 is described as having one bidirectional AC / DC converter 30, but it may also have multiple bidirectional AC / DC converters 30. Figure 5 is a circuit block diagram showing another example of the configuration of the bidirectional power converter 3. In the example shown in Figure 5, the bidirectional power converter 3 includes N bidirectional AC / DC converters 30_1 to 30_N, N reactors L1 to LN, and N capacitors C1 to CN. N is an integer of 2 or more.

[0064] N bidirectional AC / DC converters 30_1 to 30_N are connected in parallel to each other between the AC power supply line 2 and the DC power supply line 4. N reactors L1 to LN and N capacitors C1 to CN constitute N AC filters. The N AC filters are provided corresponding to each of the N bidirectional AC / DC converters 30_1 to 30_N.

[0065] The electrical energy storage device 20 includes N energy storage devices 20_1 to 20_N. Each energy storage device is a secondary battery or a capacitor. The N energy storage devices 20_1 to 20_N are provided in correspondence with N bidirectional AC / DC converters 30_1 to 30_N. One energy storage device may be provided for each of the N bidirectional AC / DC converters 30_1 to 30_N.

[0066] When the AC power supply 10 is functioning properly, each bidirectional AC / DC converter converts the AC power supplied from the AC power supply line 2 into DC power and outputs it to the DC power supply line 4, and also stores it in the corresponding energy storage device. Alternatively, each bidirectional AC / DC converter converts the DC power from the corresponding energy storage device into AC power and outputs it to the AC power supply line 2. When the AC power supply 10 malfunctions, each bidirectional AC / DC converter converts the DC power from the corresponding energy storage device into AC power and outputs it to the AC power supply line 2.

[0067] (2) Electrical energy storage device 20 In the event of an abnormality in the AC power supply 10 (see Figure 3), the power stored in the electrical energy storage device 20 is supplied to the load equipment 40 via the bidirectional power converter 3 and the AC power supply line 2, and also to the load equipment 42 via the DC power supply line 4.

[0068] In order to ensure the reliability of power supply in the event of an abnormality in the AC power supply 10, it is desirable to select the capacity of the electrical energy storage device 20 to be equal to or greater than the sum of the capacities of the load equipment 40 and the load equipment 42.

[0069] The electrical energy storage device 20 may also include a DC / DC converter for transferring DC power between a power storage device such as a secondary battery or capacitor and a DC power supply line 4, and a control unit for controlling the DC / DC converter.

[0070] (3) Switch 1 Switch 1 has the function of switching the electrical connection and disconnection between the AC power source 10 and the AC power supply line 2. Depending on the power fluctuation tolerance of the load equipment 40, one of the three types of switches shown in Figure 7 can be used for switch 1.

[0071] In the first example shown in Figure 7(A), switch 1 includes a mechanical switch S1. In the second example shown in Figure 7(B), switch 1 includes a semiconductor switch S2. In the third example shown in Figure 7(C), switch 1 is a high-speed switch (HSS) and includes a mechanical switch S1 and a semiconductor switch S2 connected in series.

[0072] The semiconductor switch S2 has the characteristics of faster operating speed and lower voltage resistance compared to the mechanical switch S1. The mechanical switch S1 has the characteristics of slower operating speed and higher voltage resistance compared to the semiconductor switch S2. In the third example, by connecting the semiconductor switch S2 and the mechanical switch S1 in series, a switch 1 can be configured that instantly turns off when an abnormality occurs in the AC power supply 10 and has high voltage resistance.

[0073] For example, if the load equipment 40 is not sensitive to power supply fluctuations, the switch 1 of the first example can be used. If the load equipment 40 is sensitive to power supply fluctuations, it is preferable to use the switch 1 of the second or third example.

[0074] <Effects> As described above, in Embodiment 1, when the AC power supply 10 is functioning properly, AC power is supplied directly from the AC power supply 10 to the load equipment 40, which is an AC load, without going through a converter and inverter. At the same time, DC power generated by the bidirectional power converter 3 based on the AC power from the AC power supply 10 is supplied to the load equipment 42, which is a DC load.

[0075] In the event of an abnormality in the AC power supply 10, DC power from the electrical energy storage device 20 is supplied to the load equipment 42, which is a DC load, and AC power generated by the bidirectional power converter 3 based on the DC power from the electrical energy storage device 20 is supplied to the load equipment 40, which is an AC load.

[0076] According to the uninterruptible power supply (UPS) 100 of Embodiment 1, compared to conventional UPS systems equipped with converters and inverters, power loss in the power supply path to AC loads can be reduced. Furthermore, since inverters and AC adapters are not required in the power supply path to DC loads, power loss in that path can be reduced. As a result, the UPS 100 of Embodiment 1 can supply power to AC and DC loads in parallel with high efficiency.

[0077] Furthermore, in Embodiment 1, the capacity of the bidirectional power converter 3 is selected based on the larger of the AC load and the DC load. Therefore, in a data center where the capacity of the DC load (servers) is far greater than the capacity of the AC load (air conditioning equipment), the bidirectional power converter 3 can supply power to both the AC and DC loads with a size that is substantially matched to the capacity of the DC load. Thus, the size of the device can be reduced.

[0078] (Example of application) The uninterruptible power supply 100 according to Embodiment 1 supplies DC power generated by the bidirectional power converter 3 to the load equipment 42 via the DC power supply line 4. When the load equipment 42 is a large-capacity DC load ranging from tens of MVA to hundreds of MVA, a large current flows through the DC power supply line 4, raising concerns about increased power loss and voltage drop. In addition, since a large number of DC power supply lines 4 are required to carry the large current, there are concerns that the uninterruptible power supply 100 will become larger and the equipment costs will increase.

[0079] To address these concerns, the bidirectional power converter 3 can be configured to receive medium-voltage (1kV to 35kV, for example 6.6kV) AC power from the AC power source 10, convert this medium-voltage AC power into medium-voltage (1.5kV to 100kV, for example 1.5kV) DC power, and supply it to the DC power supply line 4.

[0080] In this way, the current flowing through the DC power supply line 4 can be reduced compared to conventional uninterruptible power supplies that output low-voltage (e.g., 400V) AC power. This reduces power loss and voltage drop in the DC power supply line 4. Furthermore, since the number of DC power supply lines 4 can be reduced, it becomes possible to miniaturize the uninterruptible power supply 100 and reduce equipment costs.

[0081] Furthermore, by receiving medium-voltage AC power from the AC power source 10, the current flowing through the AC power supply line 2 can be reduced, thereby reducing power loss and voltage drop in the AC power supply line 2. Therefore, the uninterruptible power supply 100 according to Embodiment 1 is suitable for high-voltage power distribution.

[0082] [Embodiment 2] Figure 8 is a circuit block diagram showing the configuration of an uninterruptible power supply according to Embodiment 2. The uninterruptible power supply 110 according to Embodiment 2 differs from the uninterruptible power supply 100 shown in Figure 1 in that it is equipped with an AC terminal T5.

[0083] As shown in Figure 8, a distributed power supply 60 is connected to the AC terminal T5. The distributed power supply 60, although not shown in the figure, includes a DC power supply and a power conditioner. The DC power supply converts natural energy into DC power. Natural energy includes, for example, solar power, wind power, tidal power, and geothermal energy, and is also called renewable energy. The power conditioner operates in synchronization with the AC voltage VAC of the AC power supply line 2 and converts the DC power generated by the DC power supply into AC power and supplies it to the AC power supply line 2.

[0084] The uninterruptible power supply 110 further includes current detectors CD2 to CD4. Current detector CD2 detects the alternating current IL1 flowing through the output terminal T3 and provides a signal IL1f indicating the detected value to the control circuit 6. Current detector CD3 detects the direct current IL2 flowing through the output terminal T4 and provides a signal IL2f indicating the detected value to the control circuit 6. Current detector CD4 detects the alternating current IP flowing between the AC power supply line 2 and the distributed power supply 60 and provides a signal IPf indicating the detected value to the control circuit 6.

[0085] Control circuit 5 controls switch 1 based on the AC input voltage VI. Control circuit 6 controls switch 1 and bidirectional power converter 3 based on the AC voltage VAC, DC voltage VDC, AC currents IAC, IL1, IP, and DC current IL2, etc.

[0086] Figure 9 is a block diagram showing the configuration of control circuits 5 and 6 shown in Figure 8. As shown in Figure 9, control circuit 6 differs from control circuit 6 shown in Figure 2 in that it includes a power adjustment circuit 12.

[0087] The power adjustment circuit 12 manages the power input and output to the uninterruptible power supply 110 based on the AC voltage VAC, DC voltage VDC, AC currents IL1, IP, DC currents IL2, IB, switch status signal φSW, etc. The power adjustment circuit 12 generates a signal φP for controlling the switching circuit 9 based on the state of switch 1 (i.e., whether there is an abnormality in the AC power supply 10), the power consumption of the load equipment 40, 42, the power generated by the distributed power supply 60, etc.

[0088] Specifically, the power adjustment circuit 12 determines the power consumption PL1 of the load equipment 40 based on the AC voltage VAC of the AC power supply line 2 and the AC current IL1 indicated by the output signal IL1f of the current detector CD2. The power adjustment circuit 12 determines the power consumption PL2 of the load equipment 42 based on the DC voltage VDC of the DC power supply line 4 and the DC current IL2 indicated by the output signal IL2f of the current detector CD3. Furthermore, the power adjustment circuit 12 determines the generated power PP of the distributed power source 60 based on the AC voltage VAC of the AC power supply line 2 and the AC current IP indicated by the output signal IPf of the current detector CD4.

[0089] When the switch status signal φSW is at the "H" level (when the AC power supply 10 is healthy), the power adjustment circuit 12 controls the switching circuit 9 to provide the output signal of the AC / DC control unit 7 to the bidirectional power converter 3. As a result, when the AC power supply 10 is healthy, the AC / DC conversion operation in the bidirectional power converter 3 is controlled so that the DC voltage VDC of the DC power supply line 4 becomes the reference DC voltage VDCr. Figure 10 is a diagram illustrating the first operation of the uninterruptible power supply 110 when the AC power supply 10 is healthy. In Figure 10, the power flow path is indicated by arrows.

[0090] As shown in Figure 10, when the AC power supply 10 is functioning properly, the control circuit 5 turns on switch 1. The AC power from the AC power supply 10 is supplied to the AC power supply line 2 via switch 1. The power generated by the distributed power supply 60 is supplied to the AC power supply line 2.

[0091] The AC power supplied from the AC power source 10 and the distributed power source 60 is supplied to the load equipment 40 via the AC power supply line 2, and is also converted to DC power by the bidirectional power converter 3 and supplied to the DC power supply line 4.

[0092] For example, if the power generated by the distributed power source 60 (PP) is less than the sum of the power consumption of the load equipment 40 (PL1) and the power consumption of the load equipment 42 (PL2) (PLL = PL1 + PL2), the deficit is supplied from the AC power source 10 to the AC power supply line 2. Conversely, if the power generated by the distributed power source 60 (PP) is greater than the sum of the power consumption (PL), the surplus power is supplied to the AC power source 10 via the switch 1.

[0093] In Figure 10, when the AC power supply 10 is functioning properly, the AC power supplied from the AC power supply 10 and the distributed power supply 60 to the AC power supply line 2 is supplied to the load equipment 40 and the bidirectional power converter 3. However, the uninterruptible power supply 100 may also be configured to operate in grid-connected mode, exchanging power with the AC power supply 10.

[0094] Figure 11 illustrates other operations of the uninterruptible power supply 100 when the AC power supply 10 is functioning properly. In Figure 11, the paths through which power flows are indicated by arrows.

[0095] For example, if there is a request to reduce the AC power received from the AC power source 10 (e.g., peak shaving), and the generated power PP of the distributed power source 60 is less than the power consumption PL1 of the load equipment 40, the bidirectional power converter 3 converts the DC power of the electrical energy storage device 20 into AC power and supplies it to the AC power supply line 2. In this case, the power adjustment circuit 12 controls the switching circuit 9 so that the output signal of the DC / AC control unit 8 is provided to the bidirectional power converter 3. As a result, the DC / AC conversion operation in the bidirectional power converter 3 is controlled so that the AC voltage VAC of the AC power supply line 2 becomes the reference AC voltage VACr.

[0096] When the switch status signal φSW is at the "L" level (indicating an abnormality in the AC power supply 10), the power adjustment circuit 12 controls the switching circuit 9 based on the power consumption PL1 of the load equipment 40, the power consumption PL2 of the load equipment 42, and the generated power PP of the distributed power supply 60.

[0097] Specifically, the power adjustment circuit 12 controls the switching circuit 9 so that, if the generated power PP of the distributed power source 60 is greater than the total power PL, the output signal of the AC / DC control unit 7 is supplied to the bidirectional power converter 3. This controls the AC / DC conversion operation in the bidirectional power converter 3 so that the DC voltage VDC of the DC power supply line 4 becomes the reference DC voltage VDCr. Figure 12 is a diagram illustrating the first operation of the uninterruptible power supply 110 in the event of an abnormality in the AC power source 10. In Figure 12, the path through which power flows is indicated by arrows.

[0098] As shown in Figure 12, in the event of an abnormality in the AC power supply 10, the control circuit 5 turns off switch 1, interrupting the connection between the AC power supply 10 and the AC power supply line 2. The power generated by the distributed power supply 60 is supplied to the load equipment 40 via the AC power supply line 2 and also to the load equipment 42 via the DC power supply line 4. In addition, any surplus power is supplied from the DC power supply line 4 to the electrical energy storage device 20, which is then charged.

[0099] On the other hand, if the power generated PP of the distributed power source 60 is less than the total power PL, the power adjustment circuit 12 compares the power generated PP of the distributed power source 60 with the power consumed PL1 of the load equipment 40. If the power generated PP of the distributed power source 60 is greater than the power consumed PL1 of the load equipment 40, the power adjustment circuit 12 controls the switching circuit 9 to provide the output signal of the AC / DC control unit 7 to the bidirectional power converter 3. This controls the AC / DC conversion operation in the bidirectional power converter 3 so that the DC voltage VDC of the DC power supply line 4 becomes the reference DC voltage VDCr. Figure 13 is a diagram illustrating the second operation of the uninterruptible power supply 110 in the event of an abnormality in the AC power source 10. In Figure 12, the power flow path is indicated by arrows. As shown in Figure 13, the power generated by the distributed power source 60 is supplied to the load equipment 40 via the AC power supply line 2 and also supplied to the DC power supply line 4. The power needed to compensate for the power consumption PL2 of the load equipment 42 is supplied from the electrical energy storage device 20 to the DC power supply line 4.

[0100] On the other hand, if the generated power PP of the distributed power source 60 is less than the power consumption PL1 of the load equipment 40, the power adjustment circuit 12 controls the switching circuit 9 to provide the output signal of the DC / AC control unit 8 to the bidirectional power converter 3. This controls the DC / AC conversion operation in the bidirectional power converter 3 so that the AC voltage VAC of the AC power supply line 2 becomes the reference AC voltage VACr. Figure 14 is a diagram illustrating the third operation of the uninterruptible power supply 110 in the event of an abnormality in the AC power source 10. In Figure 14, the path through which power flows is indicated by arrows. As shown in Figure 14, the DC power of the electrical energy storage device 20 is supplied to the load equipment 42 via the DC power supply line 4 and also to the bidirectional power converter 3. The bidirectional power converter 3 converts the DC power to AC power and outputs it to the AC power supply line 2. Therefore, the generated power of the distributed power source 60 and the output power of the bidirectional power converter 3 are supplied to the load equipment 40 via the AC power supply line 2.

[0101] <Effects> As described above, in Embodiment 2, since the distributed power source 60 is connected to the AC power supply line 2, when the AC power source 10 is functioning properly, power can be supplied to the load equipment 40 and 42 using the AC power supplied from the AC power source 10 via the switch 1 and the AC power supplied from the distributed power source 60 which operates in synchronous connection with the AC power source 10. By effectively utilizing the power generated by the distributed power source 60, for example, if there is a request to reduce the AC power received from the AC power source 10 (for example, peak cutting), that request can be met.

[0102] Furthermore, in the event of an abnormality in the AC power supply 10, power can be supplied to the load equipment 40 and 42 using the power stored in the electrical energy storage device 20 and the power generated by the distributed power supply 60. Therefore, compared to a configuration in which power is supplied to the load equipment 40 and 42 using only the power stored in the electrical energy storage device 20, the reliability of power supply in the event of an abnormality in the AC power supply 10 can be improved.

[0103] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims and not by the foregoing description, and all modifications within the meaning and scope of the claims are intended to be included.

[0104] 1 Switch, 2 AC power supply line, 3 Bidirectional power converter, 4 DC power supply line, 5, 6 Control circuits, 7 AC / DC control unit, 8 DC / AC control unit, 9 Switching circuit, 10 AC power supply, 12 Power adjustment circuit, 20_1 to 20_N Energy storage device, 30 Bidirectional AC / DC converter, 40, 42 Load equipment, 50 Anomaly detector, 52 Switch control unit, 60 Distributed power supply, 71, 75, 81, 83 Subtractor, 72, 82 Voltage control unit, 73 Multiplier, 74 Sine wave generator, 76, 84 Current control unit, 77, 85 Adder, 78, 86 PWM circuit, 100, 110 Uninterruptible power supply, CD1 to CD4 Current detector, S1 Mechanical switch, S2 Semiconductor switch, T1 Input terminal, T2 DC terminal, T3, T4 Output terminal, T5 AC terminals, L1-LN reactors, C1-CN capacitors.

Claims

1. An uninterruptible power supply comprising: an AC power supply line for supplying AC power to an AC load; a switch whose first terminal is connected to an AC power source and whose second terminal is connected to the AC power supply line; and a DC power supply line for supplying DC power to a DC load, wherein an electrical energy storage device is connected to the DC power supply line, and the uninterruptible power supply further comprises a bidirectional power converter for converting power bidirectionally between the AC power supply line and the DC power supply line.

2. The uninterruptible power supply according to claim 1, further comprising a control device for controlling the switch and the bidirectional power converter, wherein the control device is configured to detect an abnormality in the AC power supply based on the AC input voltage from the AC power supply, and when the AC power supply is healthy, the control device turns on the switch, and when the AC power supply is abnormal, the control device turns off the switch and controls the bidirectional power converter to convert the DC power of the electrical energy storage device into AC power and output it to the AC power supply line.

3. The uninterruptible power supply according to claim 1 or 2, wherein the capacity of the bidirectional power converter is selected based on the larger of the AC load and the DC load.

4. The uninterruptible power supply according to claim 1 or 2, wherein the capacity of the electrical energy storage device is selected to be equal to or greater than the sum of the capacity of the AC load and the capacity of the DC load.

5. The uninterruptible power supply according to claim 1 or 2, wherein the switch is selected from a mechanical switch, a semiconductor switch, or a series circuit of a mechanical switch and a semiconductor switch, depending on the voltage fluctuation tolerance of the AC load.

6. In the event of an abnormality in the AC power supply, the control device controls the bidirectional power converter so that the AC voltage of the AC power supply line becomes the reference AC voltage, as described in claim 2.

7. When the AC power supply is functioning properly, the control device controls the bidirectional power converter to convert the AC power supplied from the AC power supply to the AC power supply line via the switch into DC power and output it to the DC power supply line, as described in claim 2.

8. When the AC power supply is functioning properly, the control device controls the bidirectional power converter so that the DC voltage of the DC power supply line becomes the reference DC voltage, as described in claim 7.

9. The uninterruptible power supply according to claim 2, wherein when the AC power supply is functioning properly, the control device controls the bidirectional power converter so that the uninterruptible power supply operates in grid-connected mode with the AC power supply.

10. The uninterruptible power supply according to claim 1, wherein a distributed power source that supplies AC power generated from generated power to the AC power supply line is connected to the AC power supply line.

11. The uninterruptible power supply according to claim 10, further comprising a control device for controlling the switch and the bidirectional power converter, wherein the control device is configured to detect an abnormality in the AC power supply based on the AC input voltage from the AC power supply, the control device turns on the switch when the AC power supply is healthy, the control device turns off the switch when the AC power supply is abnormal, and controls the bidirectional power converter to convert the AC power supplied from the distributed power supply to the AC power supply line into DC power and output it to the DC power supply line when the power generated by the distributed power supply is greater than the power consumed by the AC load, and controls the bidirectional power converter to convert the DC power of the electrical energy storage device into AC power and output it to the AC power supply line when the power generated by the distributed power supply is less than the power consumed by the AC load.

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