Uninterruptible power supply device

Abstract

This uninterruptible power supply device is provided with a converter (1), capacitors (C1, C2), an inverter (3), a first current detector (CD1), a second current detector (CD3), and a control device (5). The control device (5) controls the converter (1) such that the phase of the input voltage and the phase of the input current of the converter (1) match each other and such that the DC voltage of the DC lines (L1, L3) becomes a first reference voltage. The control device (5) controls the converter (1) such that the input current, which includes a feedback component corresponding to a deviation between a DC voltage of the DC lines (L1, L3) and a first reference voltage, and a feed-forward component corresponding to a load current detected by the second current detector (CD2), flows from the AC power source to the converter (1).

Description

Technical Field

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

[0002] For example, International Publication No. 2020 / 026430 (Patent Document 1) discloses an uninterruptible power supply device comprising a converter, a capacitor, an inverter, and a control device. When the AC power supply is available, the converter converts the AC power supplied from the AC power supply to DC power and supplies it to the DC line. The capacitor is connected to the DC line. The inverter converts the DC power received from the DC line to AC power and supplies it to the load. When the AC power supply is available, the control device controls the converter in such a way that the DC voltage of the DC line is used as a reference voltage.

[0003] Existing technical documents Patent documents Patent Document 1: International Publication No. 2020 / 026430 Summary of the Invention

[0004] The problem that the invention aims to solve In such an uninterruptible power supply (UPS), the control device controls the converter in a manner that stabilizes the DC voltage of the DC line evenly and makes the power factor of the input power supplied to the UPS equal to 1. Furthermore, the capacitance of the capacitor is set to a sufficiently large value according to the load specifications so that the capacitor can absorb fluctuations in the output power of the UPS caused by ripple voltage containing high-frequency components and the characteristics of the load.

[0005] On the other hand, from the perspective of miniaturization and cost reduction of devices, capacitor miniaturization is required. However, if capacitor miniaturization results in a reduction in capacitance, the capacitance will be insufficient to stabilize the DC voltage of the DC line relative to load variations. In addition, the ripple voltage generated in the DC line will cause greater distortion of the input current waveform of the converter, potentially reducing efficiency.

[0006] Therefore, the main objective of this disclosure is to provide a small and efficient uninterruptible power supply device.

[0007] Methods for solving problems The uninterruptible power supply device disclosed herein includes a converter, a capacitor, an inverter, a first current detector, a second current detector, and a control device. The converter converts AC power supplied from an AC power source into DC power and supplies it to a DC line. The capacitor is connected to the DC line. The inverter converts DC power received from the DC line into AC power and supplies it to a load. The first current detector detects the input current of the converter. The second current detector detects the load current flowing from the inverter to the load. The control device controls the converter in a manner that makes the input voltage of the converter phase with the input current, and the DC voltage of the DC line serves as a first reference voltage. The control device controls the converter such that the input current, including a feedback component corresponding to the deviation between the DC voltage of the DC line and the first reference voltage, and a feedforward component corresponding to the load current detected by the second current detector, flows from the AC power source to the converter.

[0008] Invention Effects According to this disclosure, a small and highly efficient uninterruptible power supply device can be provided. Attached Figure Description

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

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

[0011] Figure 3 It is a block diagram showing the structure of the part of the control device associated with the control of the converter.

[0012] Figure 4 It means Figure 3 The block diagram shown illustrates the configuration of the control circuit.

[0013] Figure 5 This is a circuit block diagram showing the configuration of the uninterruptible power supply device according to Embodiment 2.

[0014] Figure 6 It means Figure 5 The diagram shows the configuration of the part of the control device associated with the control of the converter.

[0015] Figure 7 It means Figure 6 The block diagram shown illustrates the configuration of the control circuit.

[0016] Figure 8 It is a flowchart used to illustrate the control of the switch by the switch control unit.

[0017] Figure 9 This is a flowchart used to explain the control of the load current FF section.

[0018] Figure 10 This is a circuit block diagram showing the configuration of the uninterruptible power supply device according to Embodiment 1. 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 configuration of the uninterruptible power supply device according to Embodiment 1. For example... Figure 1 As shown, the uninterruptible power supply device includes an input terminal T1, a DC terminal T2, an output terminal T3, a converter 1, current detectors CD1 to CD3, DC lines L1 to L3, capacitors C1 to C4, a bidirectional chopper 2, an inverter 3, an operation unit 4, and a control device 5.

[0021] Input terminal T1 receives AC voltage VI from AC power supply 6. The instantaneous value of AC voltage VI (hereinafter also referred to as "AC input voltage VI") is detected by control device 5. Based on the instantaneous value of AC input voltage VI, it is determined whether AC power supply 6 has experienced a power outage.

[0022] DC terminal T2 is connected to battery 7 (power storage device). Battery 7 stores DC power. A capacitor can also be connected instead of battery 7. The instantaneous value of the DC voltage VB at DC terminal T2 (i.e., the inter-terminal voltage VB of battery 7) is detected by control device 5.

[0023] Output terminal T3 is connected to load 8. Load 8 is driven by AC power supplied from an uninterruptible power supply. The instantaneous value of the AC voltage VO (hereinafter also referred to as "AC output voltage VO") appearing at output terminal T3 is detected by control device 5.

[0024] In addition, the uninterruptible power supply (UPS) receives three-phase AC voltage from AC power source 6 and supplies three-phase AC voltage to load 8. However, for the sake of simplicity in the accompanying drawings and descriptions, in Figure 1 Only one phase of the circuit is shown in the diagram.

[0025] Converter 1 has an AC terminal 1a, a positive voltage terminal 1b, a neutral voltage terminal 1c, and a negative voltage terminal 1d. Bidirectional chopper 2 has a DC terminal 2a, a positive voltage terminal 2b, a neutral voltage terminal 2c, and a negative voltage terminal 2d. Inverter 3 has an AC terminal 3a, a positive voltage terminal 3b, a neutral voltage terminal 3c, and a negative voltage terminal 3d.

[0026] The AC terminal 1a of converter 1 is connected to the input terminal T1. The current detector CD1 detects the instantaneous value of the current Ii (hereinafter also referred to as "AC input current Ii") flowing between the input terminal T1 and the AC terminal 1a of converter 1, and provides a signal Iif representing its detected value to the control device 5.

[0027] The DC terminal 2a of the bidirectional chopper 2 is connected to the DC terminal T2. The current detector CD2 detects the instantaneous value of the DC current IB flowing between the DC terminal T2 and the DC terminal 2a, and provides the signal IBf, representing its detected value, to the control device 5.

[0028] The AC terminal 3a of inverter 3 is connected to the output terminal T3. The current detector CD3 detects the instantaneous value of the current Io (hereinafter also referred to as "load current Io") flowing between the AC terminal 3a and the output terminal T3, and provides the signal Iof representing its detected value to the control device 5.

[0029] The first terminals of DC lines L1 to L3 are connected to the positive voltage terminal 1b, neutral voltage terminal 1c, and negative voltage terminal 1d of converter 1, respectively. The second terminals of DC lines L1 to L3 are connected to the positive voltage terminal 3b, neutral voltage terminal 3c, and negative voltage terminal 3d of inverter 3, respectively. In addition, DC lines L1 and L3 are connected to the positive voltage terminal 2b and negative voltage terminal 2d of bidirectional chopper 2, respectively.

[0030] Capacitor C1 is connected between DC lines L1 and L2 to stabilize and smooth the DC voltage Ep between them. Capacitor C2 is connected between DC lines L2 and L3 to stabilize and smooth the DC voltage En between them. Capacitors C1 and C2 are connected in series between DC lines L1 and L3 to stabilize and smooth the DC voltage VD = Ep + En between them. The instantaneous values ​​of DC voltages Ep and En are detected by control device 5.

[0031] Capacitor C3 is connected between terminals 2b and 2c of the bidirectional chopper 2 to stabilize and smooth the DC voltage between terminals 2b and 2c. Capacitor C4 is connected between terminals 2c and 2d of the bidirectional chopper 2 to stabilize and smooth the DC voltage between terminals 2c and 2d. Capacitors C3 and C4 are connected in series between terminals 2b and 2d of the bidirectional chopper 2 to stabilize and smooth the DC voltage VD = Ep + En between terminals 2b and 2d.

[0032] Converter 1 is a known converter comprising multiple transistors and multiple diodes, and is controlled by control device 5. When the AC input voltage VI is normally supplied from the AC power source 6 (i.e., when the AC power source 6 is functioning properly), converter 1 converts the AC input voltage VI supplied from the AC power source 6 via input terminal T1 into three-level DC voltages V1 to V3, and outputs them to DC lines L1 to L3 respectively. That is, Ep = V1 - V2, En = V2 - V3. When the AC input voltage VI is not normally supplied from the AC power source 6 (i.e., when the AC power source 6 is de-energized), the operation of converter 1 stops.

[0033] The bidirectional chopper 2 is a known configuration comprising multiple transistors and multiple diodes, and is controlled by the control device 5. When the AC power supply 6 is intact, the bidirectional chopper 2 stores the DC power supplied from the converter 1 via DC lines L1 and L3 in the battery 7.

[0034] When AC power supply 6 fails, bidirectional chopper 2 converts the DC voltage VB of battery 7 into three-level DC voltages V1 to V3, and outputs them to the positive voltage terminal 2b, neutral voltage terminal 2c, and negative voltage terminal 2d, respectively. DC voltages V1 and V3 are supplied to DC lines L1 and L3, respectively. The DC voltage (V1-V3) between DC lines L1 and L3 is divided by capacitors C1 and C2, generating a neutral voltage V2 = (V1-V3) / 2 in DC line L2. The DC voltage V2 of DC line L2 is then supplied to inverter 3.

[0035] Inverter 3 is a known inverter comprising multiple transistors and multiple diodes, and is controlled by control device 5. When AC power supply 6 is available, inverter 3 converts the three-level DC voltage V1-V3 supplied from converter 1 via DC lines L1-L3 into AC output voltage VO and supplies it to load 8. When AC power supply 6 is interrupted, inverter 3 converts the three-level DC voltage V1-V3 supplied from battery 7 via bidirectional chopper 2 and DC lines L1-L3 into AC output voltage VO and supplies it to load 8.

[0036] The operation unit 4 includes multiple buttons operated by the user of the uninterruptible power supply (UPS), an image display unit for displaying various information, etc. By operating the operation unit 4, the user can turn the power supply of the UPS on and off, or set various information.

[0037] The control device 5 controls the entire uninterruptible power supply device based on AC input voltage VI, AC input current Ii, DC voltage Ep, En, VB, AC output voltage VO, load current Io, and signals from the operation unit 4.

[0038] Figure 2 This is a block diagram illustrating an example of the hardware configuration of control device 5. For example... Figure 2 As shown, the control device 5 can typically be composed of a microcomputer with a pre-stored program.

[0039] exist Figure 2 In this example, the control device 5 includes a CPU (Central Processing Unit (50), a memory 52, and input / output (I / O) circuitry 54. The CPU 50, memory 52, and I / O circuitry 54 can send and receive data with each other via a bus 56. A program is stored in a portion of the memory 52, and the CPU 50 executes the program to perform various functions described later. The I / O circuitry 54 inputs and outputs signals and data to and from the outside of the control device 5.

[0040] Or, with Figure 2 Unlike other examples, at least a portion of the control device 5 can be constructed using circuits such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

[0041] When the AC power supply 6 is intact, the control device 5 makes the DC voltage VD = Ep + En between the DC lines L1 and L3 a reference voltage VD. The converter 1 is controlled in such a way that the input current (AC input current Ii) is in phase with the AC input voltage VI, and the difference between the DC voltages Ep and En, ΔE = Ep - En, is zero. When the AC power supply 6 is de-energized, the control device 5 stops the operation of the converter 1.

[0042] Furthermore, when the AC power supply 6 is intact, the control device 5 controls the bidirectional chopper 2 by using the DC voltage VB as the reference voltage VBR. When the AC power supply 6 is de-energized, the control device 5 uses the DC voltage VD between DC lines L1 and L3 as the reference voltage VD. The bidirectional chopper 2 is controlled in a certain way.

[0043] Furthermore, the control device 5 makes the AC output voltage VO a sinusoidal reference voltage VO. The inverter 3 is controlled in this way.

[0044] Figure 3 This is a block diagram showing the configuration of the part of the control device 5 associated with the control of the converter 1. For example... Figure 3 As shown, the control device 5 is configured to include a power outage detector 10, an adder 11, a subtractor 12, and a control circuit 13. Figure 3 The functions of each module shown can be realized through at least one of the software processing and hardware processing of the control device 5.

[0045] The power outage detector 10 detects whether the AC power supply 6 has experienced a power outage based on the AC input voltage VI supplied from the AC power supply 6, and outputs a power outage detection signal indicating the detection result. F. Power outage detection signal When AC power supply 6 is functioning properly, F is set to the inactive "L" level. In the event of a power outage at AC power supply 6, the power outage detection signal... F is set to the "H" level, which is the active level. For example, the power outage detector 10 determines that a power outage has occurred in the AC power supply 6 when the AC input voltage VI is lower than the lower limit.

[0046] Adder 11 adds the DC voltage between DC lines L1 and L2 (i.e., the voltage between the terminals of capacitor C1) Ep to the DC voltage between DC lines L2 and L3 (i.e., the voltage between the terminals of capacitor C2) En, to calculate the DC voltage between DC lines L1 and L3, VD = Ep + En. Subtractor 12 subtracts the DC voltage En from the DC voltage Ep to calculate the DC voltage ΔE = Ep - En.

[0047] Control circuit 13 detects the power failure signal When F is at the "L" level, based on the AC input voltage VI, AC input current Ii, DC voltage VD, ΔE, and load current Io, the DC voltage VD is made to serve as the reference voltage VD. The converter 1 is controlled in such a way that the DC voltage ΔE becomes 0.

[0048] A power outage detection signal is generated when AC power supply 6 fails. When F reaches the "H" level, control circuit 13 stops the operation of converter 1. When converter 1 stops operating, all transistors contained in converter 1 become off, and input terminal T1 is electrically disconnected from DC lines L1 to L3.

[0049] Figure 4 It means Figure 3 The block diagram shown illustrates the configuration of the control circuit 13. Figure 4 As shown, the control circuit 13 includes a reference voltage generation unit 20, subtractors 24 and 36, a filter 22, a DC voltage control unit 26, a load current feedforward (FF) unit 28, adders 30, 40 and 44, a multiplier 32, a divider 34, a current control unit 38, a balance control unit 42 and a PWM (Pulse Width Modulation) circuit 46.

[0050] Reference voltage generation unit 20 generates reference voltage VD Filter 22 removes the AC component from the DC voltage VD from adder 11. Filter 22 is configured, for example, to include a moving average circuit. The moving average circuit calculates a moving average value over a predetermined moving average interval Tw for the DC voltage VD from adder 11. The moving average interval Tw is, for example, set to the reciprocal of the frequency f of the AC power supply 6 (Tw = 1 / f). Therefore, when the frequency f of the AC power supply 6 is 50Hz, the moving average interval Tw = 20ms.

[0051] Subtractor 24 calculates the reference voltage VD The deviation ΔVD from the DC voltage VD from filter 22 is equal to VD. -VD.

[0052] The DC voltage control unit 26 calculates the feedback component Ifb used to control the input current (AC input current Ii) of the converter 1 so that the deviation ΔVD becomes zero. The DC voltage control unit 26 calculates the feedback component Ifb corresponding to the voltage ΔVD by performing proportional or proportional-integral calculations on the deviation ΔVD. Feedback control is performed in a manner that if the deviation ΔVD increases, the feedback component Ifb increases and the deviation ΔVD decreases; conversely, if the deviation ΔVD decreases, the feedback component Ifb decreases and the deviation ΔVD disappears.

[0053] The load current FF section 28 generates a current command value Ii based on the load current Io represented by the output signal Iof of the current detector CD3. The feedforward component Iff. Current command value Ii This is equivalent to the instruction value of the input current (AC input current) Ii of converter 1.

[0054] The load current FF section 28 is configured, for example, to include a moving average circuit. The moving average circuit calculates the moving average value within a predetermined moving average interval Tw based on the output signal Iof from the current detector CD3. The moving average interval Tw is, for example, set to the reciprocal of the frequency f of the AC power supply 6 (Tw = 1 / f). In the case of a frequency f = 50Hz for the AC power supply 6, the moving average interval Tw = 20ms.

[0055] Adder 30 adds the feedback component Ifb from DC voltage control unit 26 to the feedforward component Iff from load current FF unit 28 to generate current command value ID. =Ifb+Iff.

[0056] Multiplier 32 multiplies the DC voltage VD from filter 22 by the current command value ID. Generate DC power command value Pi The divider 34 uses the DC power command value Pi Divide by the AC input voltage VI to generate the current command value Ii. This generates a sinusoidal current command value Ii that is in phase with the AC input voltage VI. .

[0057] Subtractor 36 calculates the current command value Ii The deviation ΔIi=Ii from the AC input current Ii detected by current detector CD1 -Ii.

[0058] The current control unit 38 generates the voltage command value VIa in a manner that makes the deviation ΔIi zero. The current control unit 38 amplifies the deviation ΔIi, for example, by using proportional control or proportional-integral control, to generate a voltage command value VIA. Adder 40 will convert the voltage command value VIA The voltage command value VIb is generated by adding the AC input voltage VI. .

[0059] The balance control unit 42 generates a voltage command value VIc based on the DC voltage ΔE=Ep-En from the subtractor 12. For example, the balance control unit 42 generates a voltage command value VIc by performing proportional or proportional-integral calculations on the DC voltage ΔE. When ΔE = Ep - En > 0, the voltage command value VIc is generated such that the charging time of capacitor C1 is shorter than the charging time of capacitor C2. When ΔEp = Ep - En < 0, the voltage command value VIc is generated such that the charging time of capacitor C1 is longer than the charging time of capacitor C2. .

[0060] Adder 44 will convert the voltage command value VIb and V1c The voltage command value VI is generated by adding them together. The PWM circuit 46 receives a power outage detection signal from the power outage detector 10. When F is at the inactive "L" level (when AC power supply 6 is intact), the voltage command value VI is based on a sinusoidal waveform. Control converter 1. Therefore, the DC voltage VD = Ep + En is maintained as the reference voltage VD. And the DC voltage ΔE is maintained at 0.

[0061] Additionally, in the power outage detection signal When F is at the "H" level (the activation level) (when AC power supply 6 is interrupted), PWM circuit 46 stops the operation of converter 1. As a result, input terminal T1 is electrically disconnected from DC lines L1 to L3.

[0062] As explained above, in Implementation 1, the feedforward component Iff corresponding to the load current Io is introduced into the current command value ID. This enables the AC input current Ii, which includes the feedback component Ifb and the feedforward component Iff, to flow from the AC power supply 6 into the converter 1.

[0063] Therefore, the feedback component Ifb can be controlled at a low speed to achieve control stabilization, and the feedforward component Iff can respond quickly to changes in the load current Io. In addition, the proportional gain of the feedback component Ifb can be set to a relatively small value, thus stabilizing the proportional control or proportional-integral control in the DC voltage control unit 26.

[0064] Furthermore, the DC voltage VD can be stabilized by controlling converter 1, thereby reducing the capacitance of capacitors C1 and C2 and making them smaller. Therefore, it is possible to achieve miniaturization and cost reduction of the device size.

[0065] In addition, Figure 4 The text describes a configuration that uses the detected value of the load current Io detected by the current detector CD3 to generate the feedforward component Iff, but it can also be configured to use the detected value of the current flowing in the DC lines L1 and L3 to generate the feedforward component Iff.

[0066] [Implementation Method 2] Figure 5 This is a circuit block diagram illustrating the configuration of the uninterruptible power supply device according to Embodiment 2. For example... Figure 5 As shown, the uninterruptible power supply device of Embodiment 2 and Figure 1 The uninterruptible power supply device shown is different in that it has input terminals T1a, T1b and switch (SW) 9.

[0067] Input terminal T1a receives AC voltage VIA from AC system 6A. The instantaneous value of AC voltage VIA is detected by control device 5. Based on the instantaneous value of AC voltage VIA, it is determined whether AC system 6A has experienced a power outage. Input terminal T1b receives AC voltage VIB from generator 6B.

[0068] Switch 9 is connected between input terminals T1a and T1b and AC terminal 1a of converter 1. Switch 9 is controlled by control device 5 and configured to connect either input terminal T1a or T1b to AC terminal 1a of converter 1. That is, the uninterruptible power supply device of embodiment 2 is configured to switch between AC system 6A and generator 6B as an AC power source.

[0069] When AC system 6A is connected to AC terminal 1a of converter 1 via switch 9, the AC input voltage VI becomes the output voltage VIA of AC system 6A. When generator 6B is connected to AC terminal 1a of converter 1 via switch 9, the AC input voltage VI becomes the output voltage VIB of generator 6B.

[0070] Figure 6 It means Figure 5 A block diagram showing the configuration of the part of the control device 5 associated with the control of the converter 1. (See diagram for reference.) Figure 6 As shown, control device 5 and Figure 2 The difference in the control device 5 shown is that it includes a SOC detector 14 and a power failure detector 15.

[0071] SOC detector 14 detects the State of Charge (SOC) of battery 7. SOC is a value representing the stored capacity of battery 7, for example, a percentage representing the current stored capacity relative to the full charge capacity of battery 7. SOC detector 14 detects the SOC of battery 7 based on the detected value of the inter-terminal voltage VB of battery 7. Regarding the SOC detection method, known methods can be used, such as using an OCV-SOC curve indicating the relationship between the open circuit voltage (OCV) of battery 7 and SOC. SOC detector 14 sends a signal SOCf representing the detected SOC value to control circuit 13.

[0072] The power outage detector 15 detects whether a power outage has occurred in the AC system 6A based on the AC voltage VIA supplied from the AC system 6A, and outputs a power outage detection signal indicating the detection result. FA. Power outage detection signal When AC system 6A is functioning properly, FA is set to an inactive "L" level. In the event of a power outage in AC system 6A, the power outage detection signal... FA is set to the active level "H". For example, if the AC voltage VIA is below the lower limit, the power outage detector 15 determines that a power outage of AC system 6A has occurred.

[0073] In embodiment 2, the power outage detector 10 detects whether the AC power supply (AC system 6A or generator 6B) connected to the AC terminal 1a has experienced a power outage based on the AC input voltage VI supplied to the AC terminal 1a of the converter 1, and outputs a power outage detection signal indicating the detection result. F. When the AC power supply is intact, the power outage detection signal... F is set to the "L" level. In the event of a power outage, the power outage detection signal... F is set to the "H" level.

[0074] Figure 7 It means Figure 6 The block diagram shown illustrates the configuration of the control circuit 13. Figure 7 As shown, control circuit 13 and Figure 4 The difference in the control circuit 13 shown is that it includes a switch control unit 48.

[0075] The switch control unit 48 is based on the power outage detection signal from the power outage detector 15. The output signal SOCf of FA and SOC detector 14 controls switch 9. Figure 8 This is a flowchart illustrating an example of how the switch control unit 48 controls the switch 9. Figure 8 The flowchart is repeatedly executed by the switch control unit 48 when the uninterruptible power supply is in operation.

[0076] like Figure 8 As shown, the switch control unit 48, through step (hereinafter referred to as "S") 01, bases the signal from the power outage detector 15 on the power outage detection signal. FA determines whether the AC system 6A is functioning correctly. In S01, the switch control unit 48 detects a power outage signal. If FA is at an "L" level, the AC system is considered to be functioning correctly (6A). This is confirmed during a power outage detection signal. If FA is at the "H" level, it is determined that a 6A power outage has occurred in the AC system.

[0077] When AC system 6A is functioning properly (as in S01), the switch control unit 48 controls switch 9 in S02 by connecting AC system 6A to AC terminal 1a of converter 1. In S02, the switch control unit 48 generates a control signal for controlling the switching of switch 9. SW outputs to switch 9. Switch 9 responds to the control signal from switch control unit 48. Connect the input terminal T1a to the AC terminal 1a of the converter 1. Thus, the uninterruptible power supply receives AC power from the AC system 6A.

[0078] In the case where a power outage occurs in the AC system 6A (No in S01), the switch control unit 48 determines whether the SOC of the battery 7 is equal to or higher than a predetermined SOC lower limit value (SOCmin) based on the output signal SOCf of the SOC detector 14. SOCmin is a determination value set to prevent over-discharge of the battery 7. When the SOC decreases below SOCmin during the discharge of the battery 7, the discharge of the battery 7 is prohibited.

[0079] In the case where SOC ≥ SOCmin (Yes in S03), the switch control unit 48 controls the switch 9 in such a way that the AC system 6A is connected to the AC terminal 1a of the converter 1 through S02. That is, even when a power outage occurs in the AC system 6A, when the SOC of the battery 7 ≥ SOCmin, the AC system 6A is connected to the uninterruptible power supply device. However, since AC power is not normally supplied from the AC system 6A, the power outage detector 10 outputs a power outage detection signal F of "H" level. Therefore, the PWM circuit 46 of the control circuit 13 stops the operation of the converter 1.

[0080] On the other hand, the bidirectional chopper 2 converts the DC voltage VB of the battery 7 into three-level DC voltages V1 to V3 and outputs them to the DC lines L1 to L3 respectively. The inverter 3 converts the three-level DC voltages V1 to V3 supplied from the battery 7 via the bidirectional chopper 2 and the DC lines L1 to L3 into an AC output voltage VO and supplies it to the load 8. Therefore, during the period when the SOC of the battery 7 ≥ SOCmin, the operation of the load 8 can be continued.

[0081] S03 In the case where SOC < SOCmin (No in S03), the switch control unit 48 controls the switch 9 in such a way that the generator 6B is connected to the AC terminal 1a of the converter 1 through S04. In S04, in response to the control signal SW from the switch control unit 48, the input terminal T1b is connected to the AC terminal 1a of the converter 1.

[0082] Thereby, the uninterruptible power supply device receives AC power from the generator 6B. The converter 1 converts the AC power supplied from the generator 6B into DC power and supplies it to the DC lines L1 and L3. The bidirectional chopper 2 stores the DC power supplied from the converter 1 via the DC lines L1 and L3 in the battery 7. Therefore, the SOC of the battery 7 rises from SOCmin.

[0083] In S05, based on the output signal SOCf of the SOC detector 14, the switch control unit 48 determines whether the SOC of the battery 7 is equal to or higher than a pre-determined SOC reference value (SOCbackup). SOCbackup is the SOC for ensuring the function (power outage compensation function) of the uninterruptible power supply device as a backup power supply when the AC power supply fails.

[0084] SOCbackup is set to be equal to or higher than the power storage capacity for power outage compensation. The "power storage capacity for power outage compensation" refers to the power storage capacity required to continuously supply power to the load 8 from the battery 7 for a pre-determined compensation time when an outage of the AC power supply occurs. The power storage capacity for power outage compensation is calculated based on the assumption that the load 8 at the time of an outage of the AC power supply is the rated load and based on the rated current and compensation time of the uninterruptible power supply device. In order to ensure the power outage compensation function, the uninterruptible power supply device needs to maintain the SOC of the battery 7 at or higher than SOCbackup when the AC power supply is normal.

[0085] In the case where SOC < SOCbackup (No in S05), the switch control unit 48 returns to S04 and continues to control the switch 9 in such a way that the generator 6B is connected to the AC terminal 1a of the converter 1. The uninterruptible power supply device temporarily converts the AC power from the generator 6B into DC power, supplies the DC power to the battery 7, and converts the DC power into AC power of a specified frequency and supplies it to the load 8.

[0086] In S05, in the case where SOC ≥ SOCbackup (Yes in S05), the switch control unit 48 selects the switch 9 as the AC power supply in such a way that the AC system 6A is connected to the AC terminal 1a of the converter 1 through S02, and generates a signal SW and outputs it to the switch 9.

[0087] In this case, even when the AC system 6A is out of power and the operation of the converter 1 stops, the operation of the load 8 can continue during the period when the SOC of the battery 7 ≥ SOCmin due to the action of the above power outage compensation function. In addition, when the power supply of the AC system 6A is restored, it is determined to be Yes in S01, and the control circuit 13 causes the operation of the converter 1 to start again. Therefore, the uninterruptible power supply device temporarily converts the AC power from the AC system 6A into DC power, supplies the DC power to the battery 7, and converts the DC power into AC power of a specified frequency and supplies it to the load 8.

[0088] As explained above, the uninterruptible power supply device of Embodiment 2 includes a switch SW configured to connect either the AC system 6A or the generator 6B to the AC terminal 1a of the converter 1. Therefore, even in the event of a power outage in the AC system 6A, the converter 1 can receive AC power from the generator 6B to generate DC power.

[0089] When generator 6B is connected to AC terminal 1a of converter 1, the AC input current Ii, including feedback component Ifb and feedforward component Iff, flows from generator 6B to converter 1 under the control of control circuit 13. However, when the capacity of generator 6B is sufficiently small compared to AC system 6A, there is a problem that generator 6B has difficulty in making its output current follow the AC input current Ii at a high speed. In order to make the output current follow the AC input current Ii at a high speed, the response speed of generator 6B is accelerated, which may cause generator 6B to malfunction.

[0090] In response to such concerns, in the control circuit 13, the load current FF section 28 is configured to set the feedforward component Iff to 0 when the generator 6B is connected to the AC terminal 1a of the converter 1.

[0091] Therefore, the output current of generator 6B is controlled at a low speed so that the AC input current Ii, which contains only the feedback component Ifb, flows into converter 1. Because the output current of generator 6B can be stably controlled, generator 6B malfunctions can be prevented.

[0092] Specifically, such as Figure 7 As shown, the load current FF section 28 obtains the control signal of switch 9 from the switch control section 48. SW. The load current FF section 28 is based on the load current Io represented by the output signal Iof of the current detector CD3 and the control signal. SW generates current command value Ii The feedforward component Iff. Figure 9 This is a flowchart used to explain the control of the load current FF section 28. Figure 9 The flowchart is repeatedly executed by the load current FF section 28 when the uninterruptible power supply device is operating.

[0093] like Figure 9 As shown, via S10, the load current FF section 28 is based on the control signal obtained from the switch control section 48. SW determines whether AC system 6A is connected to AC terminal 1a of converter 1. If AC system 6A is connected to AC terminal 1a of converter 1 (yes in S10), load current FF unit 28 generates feedforward component Iff in S11 based on the load current Io represented by the output signal Iof of current detector CD3. In S11, load current FF unit 28, for example, calculates the moving average value in a predetermined moving average interval Tw (Tw=20ms) for the output signal Iof from current detector CD3, thereby generating feedforward component Iff.

[0094] When AC system 6A is not connected to AC terminal 1a of converter 1, that is, when generator 6B is connected to AC terminal 1a of converter 1 (no in S10), load current FF section 28 sets feedforward component Iff to 0 through S12.

[0095] As described above, in Embodiment 2, when the AC system 6A is connected to the AC terminal 1a of the converter 1, the AC input current Ii, which includes the feedback component Ifb and the feedforward component Iff, flows into the converter 1. On the other hand, when the generator 6B is connected to the AC terminal 1a of the converter 1, the AC input current Ii, which only includes the feedback component Ifb, flows into the converter 1.

[0096] Therefore, when AC system 6A is connected to AC terminal 1a of converter 1, DC voltage VD can be controlled at high speed in response to changes in load current. On the other hand, when generator 6B is connected to AC terminal 1a of converter 1, the output current of generator 6B can be controlled at a low speed, thus preventing generator 6B from malfunctioning.

[0097] Furthermore, in Embodiment 1 described above, the application of the uninterruptible power supply device of this disclosure to a three-level uninterruptible power supply device having three DC lines L1 to L3 and four capacitors C1 to C4 was explained, but it is not limited thereto. Each of the converter 1 and the inverter 3 may also be configured with a two-level circuit or a multi-level circuit with four or more levels. For example, the uninterruptible power supply device of this disclosure can also be applied to... Figure 10 The device shown is a two-level uninterruptible power supply with two DC lines L1 and L3 and two capacitors C5 and C6.

[0098] exist Figure 10 In the uninterruptible power supply device shown, when the AC power supply 6 is intact, the control device 5 makes the DC voltage VD between the DC lines L1 and L3 the reference voltage VD. Furthermore, the converter 1 is controlled in a manner where the input current (AC input current Ii) is in phase with the AC input voltage VI. Specifically, the control device 5 synchronizes the DC voltage VD between the DC lines L1 and L3 with the reference voltage VD. The AC input current Ii, corresponding to the feedback component Ifb and the feedforward component Iff corresponding to the load current Io, flows into converter 1 to control converter 1. Therefore, the same effect as in embodiment 1 described above can be obtained.

[0099] 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.

[0100] Explanation of reference numerals in the attached figures 1 Converter; 2 Bidirectional chopper; 3 Inverter; 4 Operation unit; 5 Control device; 6 AC power supply; 6A AC system; 6B Generator; 7 Battery; 8 Load; 9 Switch; 10, 15 Power failure detector; 11; 30; 40, 44 Adder; 12, 24, 36 Subtractor; 13 Control circuit; 14 SOC detector; 20 Reference voltage generation unit; 22 Filter; 26 DC voltage control unit; 28 Load current FF unit; 32 Multiplier; 34 Divider; 38 Current control unit; 42 Balance control unit; 42, 46 PWM circuit; 48 Switch control unit; 50 CPU; 52 Memory; 54 I / O circuit; 56 Bus; C1~C4 Capacitors; CD1~CD3 Current detectors; L1~L3 DC lines.

Claims

1. An uninterruptible power supply device, comprising: The converter converts AC power supplied from an AC power source into DC power and supplies it to a DC line; A capacitor is connected to the DC line; The inverter converts the DC power received from the DC line into AC power and supplies it to the load; A first current detector detects the input current of the converter; A second current detector detects the load current flowing from the inverter to the load; as well as The control device controls the converter in such a way that the input voltage of the converter is in phase with the input current, and the DC voltage of the DC line becomes a first reference voltage. The control device controls the converter such that the input current, which includes a feedback component corresponding to the deviation between the DC voltage of the DC line and the first reference voltage, and a feedforward component corresponding to the load current detected by the second current detector, flows from the AC power source to the converter.

2. The uninterruptible power supply device according to claim 1, wherein, The control device is, The feedback component is calculated by using the deviation between the DC voltage of the DC line and the first reference voltage as input in the control operation. The feedforward component is calculated by taking the moving average of the AC power supply over one cycle based on the detection value from the second current detector. Based on the sum of the feedback component and the feedforward component, and the input voltage of the converter, a current command value is generated. The converter is controlled in such a way that the deviation between the current command value and the input current detected by the first current detector is 0.

3. The uninterruptible power supply device according to claim 1 or 2, wherein, The control device is, When the AC power supply is an AC system, the feedforward component corresponding to the load current detected by the second current detector is calculated. When the AC power source is a generator, the feedforward component is set to 0.

4. The uninterruptible power supply device according to claim 1 or 2, wherein, It also has: The switch is configured to connect either the AC system or the generator to the AC terminal of the converter. The control device is, When the AC system is connected to the AC terminal via the switch, the feedforward component is calculated based on the load current detected by the second current detector. When the generator is connected to the AC terminal via the switch, the feedforward component is set to 0.

5. The uninterruptible power supply device according to claim 4, wherein, It also has: A bidirectional chopper receives and supplies DC power between the DC line and the power storage device. When the communication system is functioning properly, the control device is, The AC system is connected to the AC terminal via the switch. The converter is controlled in such a way that the input voltage of the converter is in phase with the input current, and the DC voltage of the DC line becomes the first reference voltage. The bidirectional chopper is controlled in such a way that the voltage between the terminals of the power storage device becomes a second reference voltage. When the AC system experiences a power outage, the control device is: When the energy storage capacity of the power storage device is above a reference value, the AC system is connected to the AC terminal via the switch. On the other hand, when the energy storage capacity of the power storage device is below a lower limit value, the generator is connected to the AC terminal via the switch.

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