Uninterruptible Power System

Abstract

To provide an uninterruptible power supply system capable of suppressing an increase in size and cost of an uninterruptible power supply device while preventing a cross current from flowing between different uninterruptible power supply devices.SOLUTION: An uninterruptible power supply system 100 includes a plurality of uninterruptible power supply devices 10 connected to each other in parallel and for supplying power to a load 103. Each of the plurality of uninterruptible power supply devices includes a converter 1 for converting AC power supplied from an AC power source 101 to DC power, an inverter 3 for converting DC power supplied from the converter or a power storage unit 102 that stores DC power to AC power, and a control unit 6 for generating a PWM carrier signal that serves as a reference for a PWM signal that controls the converter and inverter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an uninterruptible power supply system, and more particularly to an uninterruptible power supply system including a plurality of uninterruptible power supply devices connected in parallel with each other. [Background technology]

[0002] 2. Description of the Related Art Conventionally, an uninterruptible power supply system including a plurality of uninterruptible power supply devices connected in parallel with each other has been disclosed (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses an uninterruptible power supply system including a plurality of uninterruptible power supplies connected in parallel to each other. Power is supplied to a UPS load from each of the plurality of uninterruptible power supplies. Each of the plurality of uninterruptible power supplies includes a converter that converts AC power input into DC power, and an inverter that converts DC power from the converter or a storage battery into AC power. Each of the plurality of uninterruptible power supplies also includes a selection contactor that switches whether or not power from the inverter is transmitted to the load, and a reactor provided in a stage subsequent to the selection contactor. Since the impedance of the reactor is relatively large, the impedance between the different uninterruptible power supplies is relatively large, and cross currents between the different uninterruptible power supplies are suppressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-215344 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the uninterruptible power supply system described in the above Patent Document 1, the reactors in each of the multiple uninterruptible power supply devices suppress cross currents between different uninterruptible power supply devices. This causes problems in that the cost of the uninterruptible power supply devices increases by the amount of the reactors, and the size of the uninterruptible power supply devices increases by the amount of the reactors.

[0006] The present invention has been made to solve the problems described above, and one object of the present invention is to provide an uninterruptible power supply system that can suppress cross currents from flowing between different uninterruptible power supply devices while suppressing increases in cost and size of the uninterruptible power supply devices, and in particular, to provide an uninterruptible power supply system that can suppress cross currents from flowing between different uninterruptible power supply devices while suppressing increases in cost and size of the uninterruptible power supply devices even when the uninterruptible power supply devices are connected with short wiring in order to reduce the installation space of the uninterruptible power supply system. [Means for solving the problem]

[0007] In order to achieve the above object, an uninterruptible power supply system according to one aspect of the present invention comprises a plurality of uninterruptible power supply devices connected in parallel to each other and supplying power to a load, each of the plurality of uninterruptible power supply devices including a converter that converts AC power supplied from an AC power source into DC power, an inverter that converts DC power supplied from the converter or a storage unit that stores DC power into AC power, and a control unit that generates a PWM carrier signal that is a reference for a PWM signal that controls the converter and the inverter, and the control unit of each of the plurality of uninterruptible power supply devices is configured to generate a PWM carrier synchronization signal for synchronizing PWM carrier signals between different uninterruptible power supply devices, and to perform control to reduce an inter-PWM carrier phase difference, which is the phase difference between the PWM carrier signal of the uninterruptible power supply device in which it is installed and the PWM carrier signals in the other uninterruptible power supply devices, by correcting the frequency of the PWM carrier signal based on the PWM carrier synchronization signal.

[0008] As described above, the uninterruptible power supply system according to one aspect of the present invention includes a control unit that performs control to reduce the phase difference between the PWM carriers by correcting the frequency of the PWM carrier signal based on the PWM carrier synchronization signal. This allows the control unit to reduce the phase difference between the PWM carriers to synchronize the inverter output voltages of the multiple uninterruptible power supplies without providing an element such as a reactor in the uninterruptible power supplies to increase the impedance between the uninterruptible power supplies, thereby suppressing the cross current (high frequency cross current) from flowing between the uninterruptible power supplies. As a result, since the cross current (high frequency cross current) is suppressed by the control unit provided in advance, unlike the case where an element such as a reactor is provided in the uninterruptible power supplies, it is possible to suppress the uninterruptible power supplies from becoming larger and more costly while suppressing the cross current from flowing between different uninterruptible power supplies. In addition, even if the impedance between the uninterruptible power supplies is small because the uninterruptible power supplies are connected to each other by short wiring without using a reactor or the like, it is possible to suppress the cross current (high frequency cross current) from flowing between different uninterruptible power supplies.

[0009] In the uninterruptible power supply system according to the above aspect, the control unit of each of the plurality of uninterruptible power supplies is preferably configured to perform control to reduce the phase difference between the PWM carriers by correcting the frequency of the PWM carrier signal so as to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies. With this configuration, the phase difference between the PWM carriers can be easily reduced by performing control to reduce the phase difference between the PWM carrier synchronization signals of the different uninterruptible power supplies.

[0010] In this case, preferably, each of the control units of the plurality of uninterruptible power supplies generates a reference synchronization signal based on the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies, and controls to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies by controlling to reduce the phase difference between the reference synchronization signal and the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided. With this configuration, each of the plurality of uninterruptible power supplies can synchronize the PWM carrier synchronization signals of the plurality of uninterruptible power supplies based on the reference synchronization signal by reducing the phase difference between the reference synchronization signal that is the reference for the PWM carrier synchronization signal and the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided. As a result, the phase difference between the PWM carrier synchronization signals of the different uninterruptible power supplies can be easily reduced.

[0011] In the uninterruptible power supply system in which the control unit generates the reference synchronization signal, the control unit of each of the plurality of uninterruptible power supplies is preferably configured to generate the reference synchronization signal across a first period in which the PWM carrier synchronization signal of the uninterruptible power supply device in which the control unit is provided becomes a predetermined value and a second period in which the PWM carrier synchronization signals of the other uninterruptible power supplies become predetermined values. With this configuration, the period in which the PWM carrier synchronization signal of each of the plurality of uninterruptible power supplies becomes a predetermined value and the period in which the reference synchronization signal is generated can be made to overlap. As a result, the predetermined phase (e.g., the central phase) of the period in which the PWM carrier synchronization signal of each of the plurality of uninterruptible power supplies becomes a predetermined value and the above-mentioned predetermined phase (i.e., the central phase) of the period in which the reference synchronization signal is generated are relatively close to each other, compared with the case in which the period in which the PWM carrier synchronization signal of each of the plurality of uninterruptible power supplies becomes a predetermined value and the period in which the reference synchronization signal is generated are shifted without overlapping each other. This makes it possible to make the phase difference between the PWM carrier synchronization signal of each of the plurality of uninterruptible power supplies and the reference synchronization signal (i.e., the phase difference between the above-mentioned central phases) relatively small. As a result, the phase of the PWM carrier synchronization signal can be easily adjusted to match the phase of the reference synchronization signal.

[0012] In the uninterruptible power supply system in which the control unit generates the reference synchronization signal, preferably, each of the multiple uninterruptible power supplies includes a first power path that supplies power from the inverter to a load, and a second power path that is provided separately from the first power path and supplies power from outside to the load without passing through the converter and the inverter, and the control unit of each of the multiple uninterruptible power supplies is configured to perform control to reduce each of the output voltage phase difference, which is the phase difference between the bypass voltage and the inverter output voltage, and the synchronization signal phase difference, by correcting the frequency of the PWM carrier signal when synchronizing the phase of the inverter output voltage output from the inverter of the uninterruptible power supply unit in which it is provided, with the phase of a bypass voltage input from the outside via the second power path to each of the multiple uninterruptible power supplies. With this configuration, by reducing the synchronization signal phase difference, it is possible to suppress cross currents (high frequency cross currents) from flowing between different uninterruptible power supplies, and by reducing the output voltage phase difference, it is possible to suppress cross currents (low frequency cross currents) from flowing between the first power path and the second power path when the power supply path to the load is switched from the first power path to the second power path (or from the second power path to the first power path).In addition, since the inverter output voltages of the respective uninterruptible power supplies are synchronized with a common bypass voltage, it is possible to suppress cross currents (low frequency cross currents) from flowing between different uninterruptible power supplies.

[0013] In this case, the control unit of each of the plurality of uninterruptible power supplies is preferably configured to control the frequency of the inverter output voltage to the rated frequency when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, and to perform control to reduce the synchronization signal phase difference by correcting the frequency of the PWM carrier signal. With this configuration, when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, the frequency of the inverter output voltage of each of the plurality of uninterruptible power supplies is controlled to the rated frequency while reducing the synchronization signal phase difference, thereby suppressing cross currents (high frequency cross currents) from flowing between different uninterruptible power supplies.

[0014] In the uninterruptible power supply system that performs control to reduce the synchronization signal phase difference when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, the control unit of each of the multiple uninterruptible power supplies is preferably configured to perform control to set the correction amount of the frequency of the PWM carrier signal to 0 when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized and the value of the synchronization signal phase difference is within a dead band between a negative first value and a positive second value. With this configuration, when the synchronization signal phase difference includes a small detection error within the dead band, correction of the frequency of the PWM carrier signal based on the detection error can be suppressed.

[0015] In the uninterruptible power supply system that performs control to reduce each of the output voltage phase difference and the synchronization signal phase difference when the phase of the inverter output voltage and the phase of the bypass voltage are synchronized, preferably, each control unit of the plurality of uninterruptible power supplies has a proportional controller that performs at least proportional control using a value calculated by adding a value based on the synchronization signal phase difference and the output voltage phase difference as an input value, and is configured to calculate a carrier frequency determination value that determines the frequency of the PWM carrier signal by adding the output value of the proportional controller to a carrier frequency reference value that is a reference for the frequency of the PWM carrier signal, and correct the frequency of the PWM carrier signal based on the carrier frequency determination value when synchronizing the phase of the inverter output voltage and the phase of the bypass voltage. With this configuration, the frequency of the PWM carrier signal is corrected based on the carrier frequency determination value obtained by adding the output value of the proportional controller to the carrier frequency reference value, so that the value calculated by adding the value based on the synchronization signal phase difference and the output voltage phase difference, which is input to the proportional controller, is reduced by feedback control. As a result, the synchronization signal phase difference and the output voltage phase difference can be easily reduced. The proportional controller is realized by software such as a program.

[0016] In the uninterruptible power supply system that performs control to reduce each of the output voltage phase difference and the synchronization signal phase difference when the phase of the inverter output voltage and the phase of the bypass voltage are synchronized, preferably, the control unit of each of the plurality of uninterruptible power supplies is configured to perform control to correct the frequency of the PWM carrier signal based on a value obtained by adding an output value from the low-pass filter to a value obtained by proportionally controlling the phase of the inverter output voltage and the phase of the bypass voltage as an input value based on the synchronization signal phase difference when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, and the input value to the low-pass filter is switched from a value other than 0 to a value of 0 based on a change from a state in which the phase of the inverter output voltage and the phase of the bypass voltage are synchronized to a state in which the synchronization is released (for example, released when the bypass voltage is powered off). With this configuration, since the low-pass filter has a predetermined time constant, it is possible to suppress a sudden decrease in the output value of the low-pass filter when the input value of the low-pass filter is switched from a value other than 0 to a value of 0. As a result, it is possible to suppress a sudden change in the frequency of the PWM carrier signal, and therefore it is possible to suppress a sudden change in the frequency of the inverter output voltage even when a bypass voltage power outage or the like occurs.

[0017] In the uninterruptible power supply system that performs control to reduce each of the output voltage phase difference and the synchronization signal phase difference when synchronizing the phase of the inverter output voltage and the phase of the bypass voltage, preferably, during an overlap period in which both the bypass voltage and the inverter output voltage of the uninterruptible power supply device in which the uninterruptible power supply device is provided are supplied to the load, the control unit of each of the plurality of uninterruptible power supplies performs control to correct the frequency of the PWM carrier signal based on a value obtained by proportionally controlling a value obtained by multiplying the output current value of the uninterruptible power supply device in which the uninterruptible power supply device is provided by a predetermined gain and a value obtained by proportionally controlling a value based on the synchronization signal phase difference as an input value, and adding the result to the value obtained by proportionally controlling a value based on the synchronization signal phase difference as an input value. With this configuration, the first d-axis cross current component can be reduced in addition to the synchronization signal phase difference during the overlap period. As a result, by reducing the synchronization signal phase difference during the overlap period, it is possible to suppress cross currents (high frequency cross currents) from flowing between different uninterruptible power supply devices, and by reducing the first d-axis cross current component, it is possible to further suppress cross currents (low frequency cross currents) from flowing between the first power path and the second power path.

[0018] In the uninterruptible power supply system that performs control to reduce the output voltage phase difference and the synchronization signal phase difference when synchronizing the phase of the inverter output voltage and the phase of the bypass voltage, preferably, each of the multiple uninterruptible power supplies has multiple uninterruptible power supply units each including a converter and an inverter, and the control unit of each of the multiple uninterruptible power supplies is configured to calculate the output voltage phase difference based on the difference between the bypass voltage and the average value of the inverter output voltage in each of the multiple uninterruptible power supply units. With this configuration, the output voltage phase difference can be calculated using the average value of the inverter output voltage in each of the multiple uninterruptible power supply units, thereby making the output voltage phase differences in each of the multiple uninterruptible power supply units equal to each other. As a result, the frequencies of the PWM carrier signals after correction in the different uninterruptible power supply units can be made equal to each other.

[0019] In the uninterruptible power supply system in which the control unit generates the reference synchronization signal, preferably, the control unit of each of the plurality of uninterruptible power supplies is configured to perform control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value obtained by proportionally controlling a value based on the synchronization signal phase difference as an input value to a value obtained by proportionally controlling a second d-axis cross current component, which is a d-axis component of the difference between the average output current value of the plurality of uninterruptible power supplies and the output current value of the uninterruptible power supply unit in which the control unit is provided, as an input value. With this configuration, the first d-axis cross current component can be reduced in addition to the synchronization signal phase difference. As a result, by reducing the synchronization signal phase difference, it is possible to suppress cross currents (high frequency cross currents) from flowing between different uninterruptible power supplies, and by reducing the second d-axis cross current component, it is possible to suppress cross currents (low frequency cross currents) from flowing between different uninterruptible power supplies. Effect of the Invention

[0020] According to the present invention, as described above, it is possible to suppress cross currents between different uninterruptible power supplies, while suppressing an increase in size and cost of the uninterruptible power supplies. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram showing a configuration of an uninterruptible power supply system according to a first embodiment. [Diagram 2] FIG. 4 is a diagram showing a configuration of a phase difference control means of a control section according to the first embodiment. [Diagram 3] FIG. 4 is a diagram showing a synchronization signal phase difference according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing a PWM carrier signal according to the first embodiment. [Diagram 5] FIG. 2 is a diagram showing a configuration of a voltage command means of a control unit according to the first embodiment. [Figure 6] FIG. 11 is a diagram showing the configuration of an uninterruptible power supply system according to a second embodiment. [Figure 7] FIG. 11 is a diagram showing a configuration of a phase difference control means of a control section according to a second embodiment. [Figure 8] FIG. 11 is a diagram showing a configuration of a voltage command means of a control unit according to a second embodiment. [Figure 9] FIG. 13 is a diagram showing the configuration of an uninterruptible power supply system according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0023] [First embodiment] The configuration of an uninterruptible power supply system 100 according to a first embodiment will be described with reference to FIGS. 1 to 5.

[0024] (Uninterruptible Power System Configuration) First, the configuration of an uninterruptible power supply system 100 will be described with reference to FIG.

[0025] 1, an uninterruptible power supply system 100 includes a plurality of uninterruptible power supply devices 10 that are connected in parallel to each other and supply power to a load 103. The plurality of uninterruptible power supply devices 10 have the same configuration. In the first embodiment, an example is shown in which the uninterruptible power supply system 100 includes three devices: an uninterruptible power supply device 10a, an uninterruptible power supply device 10b, and an uninterruptible power supply device 10c.

[0026] Each of the multiple uninterruptible power supplies 10 includes a first power path 11 that supplies power from an inverter 3, which will be described later, to a load 103. Each of the multiple uninterruptible power supplies 10 also includes a second power path 12 that is provided separately from the first power path 11 and that supplies power from an external source to the load 103 without passing through a converter 1 and an inverter 3, which will be described later.

[0027] Each of the multiple uninterruptible power supplies 10 includes a converter 1 that converts AC power supplied from an AC power supply 101 into DC power. The AC power supplies 101 supplying AC power to each uninterruptible power supply 10 are different from each other. Alternatively, AC power may be supplied to each uninterruptible power supply 10 from a common AC power supply.

[0028] Each of the plurality of uninterruptible power supplies 10 also includes a chopper 2 that boosts the DC power supplied from a power storage unit 102 that stores DC power.

[0029] Each of the multiple uninterruptible power supplies 10 also includes an inverter 3 that converts DC power supplied from the converter 1 or the power storage unit 102 into AC power. The inverter 3 normally converts DC power from the converter 1 into AC power. In addition, when an abnormality such as a power outage occurs in the AC power source 101, the inverter 3 converts DC power sent from the power storage unit 102 via the chopper 2 into AC power.

[0030] Each of the multiple uninterruptible power supplies 10 also includes an inverter switch 4 that switches the electrical connection between the inverter 3 and the load 103 on and off.

[0031] Furthermore, each of the multiple uninterruptible power supplies 10 includes a bypass switch 5. When the bypass switch 5 is on, a bypass voltage input from the outside to each of the multiple uninterruptible power supplies 10 via the second power path 12 is applied to the load 103 via the bypass switch 5. Note that the bypass voltages input to each of the multiple uninterruptible power supplies 10 have the same voltage (amplitude and phase) as each other.

[0032] Each of the multiple uninterruptible power supplies 10 includes a control unit 6 that generates a PWM carrier signal that is a reference for a PWM signal that controls the converter 1 and the inverter 3. The PWM carrier signal is, for example, a triangular wave (see FIG. 4). The control unit 6 also includes a phase difference control means 60 and a voltage command means 61. The functions of the phase difference control means 60 and the voltage command means 61 can be realized by software such as a program. The control units 6 of the multiple uninterruptible power supplies 10 also communicate with each other (for example, wireless communication).

[0033] 2, the phase difference control means 60 includes a PI regulator 60a, a dead band processing unit 60b, a low-pass filter 60c, P control units 60d to 60g, and switches 60h to 60j. The PI regulator 60a is an example of the "proportional controller" in the claims.

[0034] The control unit 6 of each of the multiple uninterruptible power supplies 10 controls whether or not to synchronize the inverter output voltage output by the inverter 3 of the uninterruptible power supply 10 in which it is provided with with the bypass voltage. Each of the switches 60h to 60j is switched to the "T" side when the inverter output voltage and the bypass voltage are to be synchronized. Also, each of the switches 60h to 60j is switched to the "F" side when the synchronization between the inverter output voltage and the bypass voltage is to be released.

[0035] 3, the control unit 6 of each of the multiple uninterruptible power supplies 10 generates a PWM carrier synchronization signal for synchronizing PWM carrier signals between different uninterruptible power supplies 10. After the reference sine wave below changes from negative to 0 or from positive to 0, the PWM carrier synchronization signal first falls to L at the upward 0 crossing point (the first point of one period of the PWM carrier signal) where the count of the PWM carrier signal (see FIG. 4) changes from -1 to 0, and rises to H a predetermined time (see period A in FIG. 3) (for example, 400 μs) after falling to L.

[0036] Here, in the first embodiment, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to perform control to reduce the inter-PWM carrier phase difference, which is the phase difference between the PWM carrier signal of the uninterruptible power supply 10 in which it is provided and the PWM carrier signals of the other uninterruptible power supplies 10, based on the PWM carrier synchronization signal by correcting the frequency of the PWM carrier signal based on the PWM carrier synchronization signal. That is, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to perform control to synchronize the PWM carrier signals between different uninterruptible power supplies 10 by correcting the frequency of the PWM carrier signal based on the PWM carrier synchronization signal.

[0037] Specifically, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to perform control to reduce the phase difference between the PWM carriers by correcting the frequency of the PWM carrier signal so as to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply 10 in which it is provided and the PWM carrier synchronization signal of another uninterruptible power supply 10. In other words, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to perform control to synchronize the PWM carrier synchronization signals between different uninterruptible power supplies 10.

[0038] Also, based on the PWM carrier signal with the corrected frequency, the three-phase reference sine wave (multiplied with the inverter output voltage amplitude command and used together with the PWM carrier signal to generate the modulated wave that is the reference for the PWM signal) is corrected. Specifically, during one period of the reference sine wave (rated frequency is, for example, 50 Hz), counting is performed for each half period of the corrected PWM carrier signal. As a result, the period of the PWM carrier signal and the period of the reference sine wave are in a proportional relationship, and when the period of the PWM carrier signal changes, the period of the reference sine wave changes accordingly. In detail, if the maximum value of the count is M and the number of counts is N, the corrected three-phase reference sine waves are sin(360deg×N / M), sin(360deg×N / M-120deg), and sin(360deg×N / M-240deg), respectively. Note that the number of counts is reset to 0 when it reaches the maximum value M.

[0039] The control for synchronizing the PWM carrier synchronization signals with each other will be described in detail. First, the control unit 6 of each of the multiple uninterruptible power supplies 10 generates a reference synchronization signal (see FIG. 3) based on the PWM carrier synchronization signal of the uninterruptible power supply 10 in which it is provided and the PWM carrier synchronization signals of the other uninterruptible power supplies 10. The reference synchronization signals generated by each of the multiple uninterruptible power supplies 10 are the same signals.

[0040] Here, in the first embodiment, the control is configured to perform control to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the uninterruptible power supply 10 itself is provided and the PWM carrier synchronization signal of another uninterruptible power supply 10 by performing control to reduce the synchronization signal phase difference, which is the phase difference between the reference synchronization signal and the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the uninterruptible power supply 10 itself is provided. Specifically, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 performs control to synchronize a predetermined phase of the reference synchronization signal with a predetermined phase of its own PWM carrier synchronization signal. As a result, the PWM carrier synchronization signals of each of the multiple uninterruptible power supplies 10 are synchronized with each other based on the above-mentioned predetermined phase of the reference synchronization signal. In detail, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 performs control to synchronize the central phase of the reference synchronization signal with the central phase of its own PWM carrier synchronization signal. The PWM carrier synchronization signal of each of the multiple uninterruptible power supplies 10 is an L active signal (L state is the active state).

[0041] In the first embodiment, the control unit 6 of each of the multiple uninterruptible power supplies 10 is configured to generate a reference synchronization signal across a period A in which the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the control unit 6 is provided has a predetermined value and a period B in which the PWM carrier synchronization signal of the other uninterruptible power supplies 10 has a predetermined value. Specifically, the control unit 6 generates a reference synchronization signal that is an OR signal of the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the control unit 6 is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies 10. When any one of the PWM carrier synchronization signals of the multiple uninterruptible power supplies 10 is L (the above-mentioned predetermined value), an OR signal (reference synchronization signal) of L level is generated. As a result, in the example shown in FIG. 3, the OR signal (reference synchronization signal) is continuously at L level from the time when the PWM carrier synchronization signal of the most advanced uninterruptible power supply 10a falls to L to the time when the PWM carrier synchronization signal of the most delayed uninterruptible power supply 10c rises to H. Moreover, period A and period B are examples of the "first period" and "second period" in the claims, respectively.

[0042] Next, the control for reducing the synchronization signal phase difference will be described with reference to FIG.

[0043] (When synchronizing the inverter output voltage and bypass voltage) In the first embodiment, as shown in FIG. 2, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supply devices 10 is configured to perform control to reduce each of the output voltage phase difference, which is the phase difference between the bypass voltage and the inverter output voltage, and the synchronization signal phase difference by correcting the frequency of the PWM carrier signal when synchronizing the phase of the inverter output voltage and the phase of the bypass voltage. Specifically, at least proportional control is performed by the PI regulator 60a using a value calculated by adding a value based on the synchronization signal phase difference (output value of the P control unit 60d) and the output voltage phase difference as an input value. In detail, feedback control is performed so that each of the synchronization signal phase difference and the output voltage phase difference is reduced within a range of a predetermined specified value close to 0 by performing proportional control and integral control by the PI regulator 60a. The value based on the synchronization signal phase difference is a value P-controlled (proportional controlled) by the P control unit 60d using the synchronization signal phase difference as an input value. Also, a predetermined P gain (for example, 10) is used in the P control unit 60d. The predetermined gain is set based on the difference between the magnitude of the synchronization signal phase difference and the magnitude of the output voltage phase difference. The P gain used in P control unit 60f is also the same as the P gain used in P control unit 60d.

[0044] The control unit 6 of each of the multiple uninterruptible power supplies 10 detects the output voltage phase difference by detecting the phase difference between the phase when the bypass voltage becomes 0V and the phase when the inverter output voltage becomes 0V.

[0045] In the first embodiment, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to calculate a carrier frequency determination value that determines the frequency of the PWM carrier signal by adding the output value of the PI regulator 60a to a carrier frequency reference value that is the reference for the frequency of the PWM carrier signal, and correct the frequency of the PWM carrier signal based on the carrier frequency determination value. The carrier frequency determination value is the number of pulses (clock count) counted until the value of the PWM carrier signal changes from 0 to the peak value of the PWM carrier signal. In the first embodiment, since the PWM carrier signal is a triangular wave, the carrier frequency determination value is the number of counts of 1 / 4 period of the PWM carrier signal (period C in FIG. 4). Therefore, the period and frequency of the PWM carrier signal are corrected by correcting the carrier frequency determination value.

[0046] In the first embodiment, each of the control units 6 (phase difference control means 60) of the multiple uninterruptible power supplies 10 is configured to perform control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value (output value of the P control unit 60e) obtained by proportionally controlling the synchronization signal phase difference as an input value to a value (output value of the P control unit 60d) obtained by proportionally controlling the synchronization signal phase difference as an input value, which is a d-axis component of the difference between the average value of the output current values ​​of the multiple uninterruptible power supplies 10 and the output current value of the uninterruptible power supply 10 in which the control unit 6 performs the control. The d-axis cross current between the UPSs is a d-axis component of a value obtained by three-phase / dq conversion of the difference between the average value of the output current values ​​of the multiple uninterruptible power supplies 10 and the output current value of the uninterruptible power supply 10 in which the control unit 6 performs the control. The d-axis cross current between the UPSs is an example of a "second d-axis cross current component" in the claims.

[0047] Specifically, a first sum is calculated by adding a value obtained by proportional control in the P control unit 60e using the d-axis cross current between the UPS as an input value to the output voltage phase difference. Then, a second sum is calculated by adding the first sum to a value obtained by proportional control using the synchronization signal phase difference as an input value (the output value of the P control unit 60d). The second sum is input to the PI regulator 60a to correct the carrier frequency determination value and correct the frequency of the PWM carrier signal.

[0048] Moreover, during the overlap period in which both the bypass voltage and the inverter output voltage of the uninterruptible power supply 10 to which it is provided are supplied to the load 103, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 performs control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value obtained by proportionally controlling a value based on the synchronization signal phase difference as an input value to a value obtained by proportionally controlling a value based on the synchronization signal phase difference as an input value (output value of the P control unit 60d) to a value obtained by proportionally controlling a d-axis cross current (active current component) during the bypass wrap as an input value (output value of the P control unit 60e). That is, during the overlap period, the P control unit 60e receives the d-axis cross current during the bypass wrap in addition to the d-axis cross current between the UPSs. The d-axis cross current during the bypass wrap is an example of the "first d-axis cross current component" in the claims.

[0049] The d-axis cross current during bypass wrap is the d-axis component of the difference between the multiplied value obtained by multiplying the output current value of the uninterruptible power supply 10 in which the bypass wrap is installed by a predetermined gain during the overlap period and the output current value of the inverter 3 of the uninterruptible power supply 10 in which the bypass wrap is installed. Specifically, the d-axis cross current during bypass wrap is the d-axis component of the value obtained by three-phase / dq conversion of the difference between the multiplied value and the output current value during the overlap period.

[0050] Moreover, the predetermined gain is changed from 1 to 0 at a predetermined slope during the overlap period when switching from inverter power supply (power supply to load 103 via first power path 11) to bypass power supply (power supply to load 103 via second power path 12). Moreover, the predetermined gain is changed from 0 to 1 at a predetermined slope during the overlap period when switching from bypass power supply to inverter power supply.

[0051] 5, the control unit 6 (voltage command means 61) generates a signal including information on a command value of the amplitude of the inverter output voltage (the inverter output voltage amplitude command in FIG. 5). The voltage command means 61 includes a PI regulator 61a and a P control unit 61b.

[0052] The control unit 6 (voltage command means 61) performs proportional control and integral control in a PI regulator 61a using the difference between a value based on an inverter output voltage amplitude command reference value, which is the reference for the command value of the amplitude of the inverter output voltage, and an inverter output voltage amplitude detection value, which is the detection value of the amplitude of the inverter output voltage, as an input value. Then, the output of the PI regulator 61a becomes an inverter output voltage amplitude command.

[0053] The value based on the inverter output voltage amplitude command reference value is a value obtained by adding a value (output value of the P control unit 61b) obtained by proportional control using the sum of the UPS q-axis cross current (reactive current component) and the q-axis cross current (reactive current component) during bypass lap as an input value to the inverter output voltage amplitude command reference value. The UPS q-axis cross current is the q-axis component of a value obtained by three-phase / dq conversion of a difference between the average output current value of the plurality of uninterruptible power supplies 10 and the output current value of the uninterruptible power supply 10 in which the uninterruptible power supply 10 itself is provided. The q-axis cross current during bypass lap is the q-axis component of a value obtained by three-phase / dq conversion of a difference between a multiplied value obtained by multiplying the output current value of the uninterruptible power supply 10 in which the uninterruptible power supply 10 itself is provided by a predetermined gain during the overlap period and the output current value of the inverter 3 of the uninterruptible power supply 10 in which the uninterruptible power supply 10 itself is provided. The predetermined gain is the same as that of the d-axis cross current during bypass lap. This makes it possible to reduce the q-axis cross current between different uninterruptible power supplies 10, and also to reduce the q-axis cross current flowing between the inverter 3 and the bypass (between the first power path 11 and the second power path 12).

[0054] (When the inverter output voltage and bypass voltage are not synchronized) In the first embodiment, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to control the frequency of the inverter output voltage to an accuracy of ±0.01% of the rated frequency when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, and to perform control to reduce the synchronization signal phase difference by correcting the frequency of the PWM carrier signal. Specifically, as shown in FIG. 2, when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, each of the switches 60h to 60j is switched to the "F" side, so that the output voltage phase difference does not contribute to the correction of the carrier frequency, and only the synchronization signal phase difference, the d-axis cross current between the UPS, and the d-axis cross current at the time of the bypass wrap contribute to the correction of the carrier frequency. In addition, the rated frequency is, for example, a frequency of 50 Hz.

[0055] The control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to perform control to set the correction amount of the PWM carrier signal frequency to 0 when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized and when the value of the synchronization signal phase difference is within a dead band range between a negative first value (e.g., -5 μs) and a positive second value (e.g., 5 μs). Specifically, when the value of the synchronization signal phase difference is within the dead band range between the first value and the second value, the output value of the dead band processing unit 60b becomes 0. Note that the absolute value of the first value and the absolute value of the second value of the dead band range may be different from each other.

[0056] Furthermore, when the value of the synchronization signal phase difference is a value greater than 5 μs (for example, P), the output value of the dead band processing unit 60b is P-5 μs. When the value of the synchronization signal phase difference is a value less than -5 μs (for example, N), the output value of the dead band processing unit 60b is N-(-5 μs). This makes it possible to suppress a sudden change in the output value of the dead band processing unit 60b when the synchronization signal phase difference changes from a value within the dead band to a value outside the dead band. As a result, it is possible to suppress a sudden change in the frequency of the PWM carrier signal. The range of the dead band is set wider than the range of detection error of the synchronization signal phase difference.

[0057] The control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 is configured to perform control to correct the frequency of the PWM carrier signal based on a value obtained by adding the output value from the low-pass filter 60c to a value (output value of the P control unit 60f) obtained by proportional control using a value based on the synchronization signal phase difference (output value of the dead band processing unit 60b) as an input value when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized.

[0058] Specifically, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 calculates a third sum by adding the output value of the P control unit 60f and the value output from the P control unit 60g using the sum of the inter-UPS d-axis cross current and the bypass wrap time d-axis cross current as an input value. Also, the control unit 6 (phase difference control means 60) of each of the multiple uninterruptible power supplies 10 calculates a carrier frequency determination value by adding the carrier frequency reference value, the third sum, and the output value from the low-pass filter 60c.

[0059] Here, in the first embodiment, the input value to the low-pass filter 60c is switched from a value other than 0 to 0 based on a change from a state in which the phase of the inverter output voltage and the phase of the bypass voltage are synchronized to a state in which the synchronization is released (for example, released when the bypass voltage is powered off). Specifically, based on a change from a state in which the phase of the inverter output voltage and the phase of the bypass voltage are synchronized to a state in which the synchronization is released, the switch 60j is switched, and the input value to the low-pass filter 60c is switched from the output value of the PI regulator 60a (a value other than the above 0 value) to 0. The low-pass filter 60c has a predetermined time constant, and performs a process of gradually decreasing the output after a 0 value is input. This makes it possible to perform a continuous change process in which the carrier frequency determination value gradually decreases. Note that the integral term of the PI regulator 60a is reset to 0 when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized. This makes it possible to suppress the output of the PI regulator 60a from becoming excessively large due to the integral term when the phase of the inverter output voltage and the phase of the bypass voltage are synchronized.

[0060] The control of the voltage command means 61 is the same as when the phase of the inverter output voltage and the phase of the bypass voltage are synchronized.

[0061] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0062] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured such that the control unit 6 of each of the multiple uninterruptible power supplies 10 generates a PWM carrier synchronization signal for synchronizing PWM carrier signals between different uninterruptible power supplies 10, and corrects the frequency of the PWM carrier signal based on the PWM carrier synchronization signal to perform control to reduce the inter-PWM carrier phase difference between the PWM carrier signal of the uninterruptible power supply 10 in which the control unit 6 is provided and the PWM carrier signals of the other uninterruptible power supplies 10. As a result, even if an element such as a reactor is not provided in the uninterruptible power supply 10 to increase the impedance between the uninterruptible power supplies 10, the control unit 6 reduces the inter-PWM carrier phase difference to synchronize the inverter output voltages of the multiple uninterruptible power supplies 10, thereby suppressing the flow of a cross current (high-frequency cross current) between the uninterruptible power supplies 10. As a result, the pre-installed control unit 6 suppresses cross currents (high-frequency cross currents), and unlike the case where elements such as reactors are provided in the uninterruptible power supply 10, it is possible to suppress the uninterruptible power supply 10 from becoming larger and increasing in cost while suppressing cross currents from flowing between different uninterruptible power supply devices 10. Furthermore, because the uninterruptible power supply devices 10 are connected to each other by short wiring without using reactors or the like, it is possible to suppress cross currents (high-frequency cross currents) from flowing between different uninterruptible power supply devices 10 even if the impedance between the uninterruptible power supply devices 10 is small.

[0063] Also, in the first embodiment, as described above, the uninterruptible power supply system 100 is configured so that the control unit 6 of each of the multiple uninterruptible power supplies 10 performs control to reduce the phase difference between the PWM carriers by correcting the frequency of the PWM carrier signal so as to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply 10 in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies 10. In this way, by performing control to reduce the phase difference between the PWM carrier synchronization signals of different uninterruptible power supplies 10, the phase difference between the PWM carriers can be easily reduced.

[0064] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured such that the control unit 6 of each of the plurality of uninterruptible power supplies 10 performs control to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the control unit 6 is provided and the PWM carrier synchronization signal of the other uninterruptible power supply 10 by performing control to reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the control unit 6 is provided and the PWM carrier synchronization signal of the other uninterruptible power supply 10. As a result, each of the plurality of uninterruptible power supplies 10 can synchronize the PWM carrier synchronization signals of the plurality of uninterruptible power supplies 10 based on the reference synchronization signal by reducing the synchronization signal phase difference between the reference synchronization signal that is the reference for the PWM carrier synchronization signal and the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the control unit 6 is provided. As a result, the phase difference between the PWM carrier synchronization signals of the different uninterruptible power supplies 10 can be easily reduced.

[0065] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured such that each of the control units 6 of the multiple uninterruptible power supplies 10 generates a reference synchronization signal across a period A in which the PWM carrier synchronization signal of the uninterruptible power supply 10 in which the control unit 6 is provided has a predetermined value and a period B in which the PWM carrier synchronization signals of the other uninterruptible power supplies 10 have a predetermined value. This allows the period in which the PWM carrier synchronization signal of each of the multiple uninterruptible power supplies 10 has a predetermined value to overlap with the period in which the reference synchronization signal is generated. As a result, the predetermined phase (e.g., the central phase) of the period in which the PWM carrier synchronization signal of each of the multiple uninterruptible power supplies 10 has a predetermined value and the above-mentioned predetermined phase (i.e., the central phase) of the period in which the reference synchronization signal is generated are relatively close to each other, compared to a case in which the period in which the PWM carrier synchronization signal of each of the multiple uninterruptible power supplies 10 has a predetermined value and the period in which the reference synchronization signal is generated are shifted without overlapping each other. This makes it possible to relatively reduce the phase difference (i.e., the phase difference between the central phases) between the PWM carrier synchronization signal and the reference synchronization signal of each of the multiple uninterruptible power supplies 10. As a result, it is easy to adjust the phase of the PWM carrier synchronization signal to match the phase of the reference synchronization signal.

[0066] In the first embodiment, as described above, when the control unit 6 of each of the plurality of uninterruptible power supplies 10 synchronizes the phase of the inverter output voltage output from the inverter 3 of the uninterruptible power supply 10 in which the control unit 6 is provided with the phase of the bypass voltage input from the outside to each of the plurality of uninterruptible power supplies 10 via the second power path 12, the uninterruptible power supply system 100 is configured to perform control to reduce the output voltage phase difference, which is the phase difference between the bypass voltage and the inverter output voltage, and the synchronization signal phase difference. In this way, by reducing the synchronization signal phase difference, it is possible to suppress the cross current (high frequency cross current) from flowing between the different uninterruptible power supplies 10, and by reducing the output voltage phase difference, it is possible to suppress the cross current (low frequency cross current) from flowing between the first power path 11 and the second power path 12 when the power supply path to the load 103 is switched from the first power path 11 to the second power path 12 (or from the second power path 12 to the first power path 11). Furthermore, since the inverter output voltages of the respective uninterruptible power supplies 10 are synchronized with a common bypass voltage, cross currents (low-frequency cross currents) between the different uninterruptible power supplies 10 can be suppressed.

[0067] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured so that, when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, the control unit 6 of each of the multiple uninterruptible power supplies 10 controls the frequency of the inverter output voltage to an accuracy of ±0.01% of the rated frequency, and performs control to reduce the synchronization signal phase difference by correcting the frequency of the PWM carrier signal. As a result, when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, the frequency of the inverter output voltage of each of the multiple uninterruptible power supplies 10 is controlled to an accuracy of ±0.01% of the rated frequency, while reducing the synchronization signal phase difference, thereby making it possible to suppress cross currents (high frequency cross currents) from flowing between different uninterruptible power supplies 10.

[0068] Furthermore, in the first embodiment, as described above, the uninterruptible power supply system 100 is configured such that, when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized and the value of the synchronization signal phase difference is within a dead zone between a negative first value and a positive second value, the control unit 6 of each of the multiple uninterruptible power supplies 10 performs control to set the correction amount of the frequency of the PWM carrier signal to 0. This makes it possible to suppress correction of the frequency of the PWM carrier signal based on a detection error when the synchronization signal phase difference contains a small detection error within the dead zone.

[0069] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured such that, when each of the control units 6 of the multiple uninterruptible power supply devices 10 synchronizes the phase of the inverter output voltage with the phase of the bypass voltage, the output value of the PI regulator 60a is added to a carrier frequency reference value that is the reference for the frequency of the PWM carrier signal to calculate a carrier frequency determination value that determines the frequency of the PWM carrier signal, and the frequency of the PWM carrier signal is corrected based on the carrier frequency determination value. As a result, the frequency of the PWM carrier signal is corrected based on the carrier frequency determination value obtained by adding the output value of the PI regulator 60a to the carrier frequency reference value, so that the value calculated by adding the value based on the synchronization signal phase difference and the output voltage phase difference, which is input to the PI regulator 60a, is reduced by feedback control. As a result, the synchronization signal phase difference and the output voltage phase difference can be easily reduced.

[0070] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured so that the input value to the low-pass filter 60c is switched from a value other than 0 to a value of 0 based on a change from a state in which the phase of the inverter output voltage and the phase of the bypass voltage are synchronized to a state in which the synchronization is released (for example, released during a power outage of the bypass voltage). As a result, since the low-pass filter 60c has a predetermined time constant, it is possible to suppress a sudden decrease in the output value of the low-pass filter 60c when the input value of the low-pass filter 60c is switched from a value other than 0 to a value of 0. As a result, it is possible to suppress a sudden change in the frequency of the PWM carrier signal, and therefore it is possible to suppress a sudden change in the frequency of the inverter output voltage even when a power outage of the bypass voltage occurs.

[0071] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured such that each of the control units 6 of the multiple uninterruptible power supplies 10 performs control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value obtained by proportionally controlling a value based on a synchronization signal phase difference as an input value to a value obtained by proportionally controlling a value based on a synchronization signal phase difference as an input value, which is a d-axis component of the difference between the output current value of the uninterruptible power supply 10 in which the control unit 6 is provided and the output current value of the inverter 3 of the uninterruptible power supply 10 in which the control unit 6 is provided, during the overlap period. This makes it possible to reduce the d-axis cross current during the bypass wrap in addition to the synchronization signal phase difference during the overlap period. As a result, by reducing the synchronization signal phase difference during the overlap period, it is possible to suppress the cross current (high frequency cross current) from flowing between the different uninterruptible power supplies 10, and by reducing the d-axis cross current during the bypass wrap, it is possible to further suppress the cross current (low frequency cross current) from flowing between the first power path 11 and the second power path 12.

[0072] In the first embodiment, as described above, the uninterruptible power supply system 100 is configured so that each of the control units 6 of the multiple uninterruptible power supplies 10 performs control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value obtained by proportionally controlling the d-axis cross current between the UPSs, which is a d-axis component of the difference between the average output current value of the multiple uninterruptible power supplies 10 and the output current value of the uninterruptible power supply 10 to which the control unit 6 is provided, to the value obtained by proportionally controlling the d-axis cross current between the UPSs, which is an input value, to a value obtained by proportionally controlling the d-axis cross current between the UPSs, which is an input value. This makes it possible to reduce the d-axis cross current between the UPSs in addition to the synchronous signal phase difference. As a result, by reducing the synchronous signal phase difference, it is possible to suppress the cross current (high frequency cross current) from flowing between the different uninterruptible power supplies 10, and by reducing the d-axis cross current between the UPSs, it is possible to suppress the cross current (low frequency cross current) from flowing between the different uninterruptible power supplies 10.

[0073] [Second embodiment] A second embodiment will be described with reference to Figures 6 to 8. Unlike the first embodiment, the second embodiment has a plurality of uninterruptible power supply devices 10 each provided with a plurality of uninterruptible power supply modules 111. Note that configurations similar to those of the first embodiment are shown with the same reference numerals in the drawings, and description thereof will be omitted.

[0074] (Uninterruptible Power System Configuration) First, the configuration of an uninterruptible power supply system 200 will be described with reference to FIG.

[0075] 6, the uninterruptible power supply system 200 includes a plurality of uninterruptible power supply devices 110 that are connected in parallel to each other and supply power to a load 103. The plurality of uninterruptible power supply devices 110 have the same configuration. In the second embodiment, an example is shown in which the uninterruptible power supply system 200 includes three devices: an uninterruptible power supply device 110a, an uninterruptible power supply device 110b, and an uninterruptible power supply device 110c.

[0076] Each of the multiple uninterruptible power supplies 110 has multiple uninterruptible power supply modules 111 each including a converter 1 and an inverter 3. As a result, even if one (or two) of the uninterruptible power supply modules 111 in the uninterruptible power supply 110 breaks down or is stopped for part replacement, etc., it is possible to supply power to the load 103 using the remaining normal uninterruptible power supply modules 111. Also, it is possible to improve the efficiency of power supply by switching the number of uninterruptible power supply modules 111 to be operated according to the size of the load 103. Also, each of the multiple uninterruptible power supply modules 111 has a chopper 2 and an inverter switch 4 in addition to the converter 1 and the inverter 3. Also, each of the multiple uninterruptible power supplies 110 includes a first power path 11 and a second power path 12. The first power path 11 is provided in each of the multiple uninterruptible power supply modules 111. The uninterruptible power supply module 111 is an example of an "uninterruptible power supply unit" in the claims.

[0077] In each of the multiple uninterruptible power supplies 110, AC power is supplied to the multiple uninterruptible power supply modules 111 from a common AC power supply 101. In each of the multiple uninterruptible power supplies 110, DC power is supplied to the multiple uninterruptible power supply modules 111 from a common power storage unit 102.

[0078] Each of the plurality of uninterruptible power supplies 110 includes a control unit 16. The control unit 16 is configured to control each of the plurality of uninterruptible power supply modules 111 in each of the plurality of uninterruptible power supplies 110. The control unit 16 includes a phase difference control means 160 and a voltage command means 161. The functions of the phase difference control means 160 and the voltage command means 161 can be realized by software such as a program.

[0079] Here, in the second embodiment, as shown in FIG. 7, the control unit 16 (phase difference control means 160) of each of the multiple uninterruptible power supplies 110 is configured to calculate an output voltage phase difference based on the difference between the bypass voltage and the average value of the inverter output voltage in each of the multiple uninterruptible power supply modules 111. Specifically, the control unit 16 of each of the multiple uninterruptible power supplies 110 generates a reference sine wave whose frequency is corrected based on a predetermined rated frequency (50 Hz). The method of correcting the reference sine wave based on the PWM carrier signal is the same as that of the first embodiment. The output voltage phase difference is a value obtained by adding the average value of the phase difference between the phase of the reference sine wave and the phase of the inverter output voltage to the phase difference between the phase of the bypass voltage and the phase of the reference sine wave. Thereby, the output voltage phase difference, which is the phase difference between the phase of the bypass voltage and the phase of the inverter output voltage, is detected. Note that the average value of the phase difference between the phase of the reference sine wave and the phase of the inverter output voltage means the average value of the phase difference between the phase of the reference sine wave and the phase of the inverter output voltage in each of the multiple uninterruptible power supply modules 111. Moreover, the reference sine wave is common to each uninterruptible power supply module 111 in each of the multiple uninterruptible power supplies 110.

[0080] The d-axis cross current during bypass wrap in the second embodiment is the d-axis component of a three-phase / dq converted value of the difference between the product of the output current detection value of the uninterruptible power supply 110 and a predetermined gain and the total output current value of the multiple uninterruptible power supply modules 111. The predetermined gain is the same as in the first embodiment.

[0081] 8 is the q-axis cross current during bypass wrap, which is the q-axis component of a three-phase / dq converted value of the difference between the multiplication value of the output current detection value of the uninterruptible power supply 110 and a predetermined gain and the total output current value of the multiple uninterruptible power supply modules 111. The predetermined gain is the same as in the first embodiment.

[0082] The PI regulator 61a receives an input of a difference between a value obtained by adding the output value of the P control unit 61b to an inverter output voltage amplitude command reference value and an average value of the inverter output voltage amplitude detection values. The average value of the inverter output voltage amplitude detection values ​​means an average value of the output voltage amplitude detection values ​​of the inverters 3 of the plurality of uninterruptible power supply modules 111 that are not stopped. Note that a control unit having a voltage command means for performing the above control may be provided in each of the plurality of uninterruptible power supply modules 111. In this case, the voltage command means outputs an inverter output voltage amplitude command for each uninterruptible power supply module 111 using the output voltage amplitude detection value of the inverter 3 of each uninterruptible power supply module 111, instead of the average value of the inverter output voltage amplitude detection values ​​used in the voltage command means 161.

[0083] Other configurations of the second embodiment are similar to those of the first embodiment.

[0084] (Effects of the second embodiment) In the second embodiment, the following effects can be obtained.

[0085] In the second embodiment, the uninterruptible power supply system 200 is configured so that the control unit 16 of each of the multiple uninterruptible power supply devices 110 calculates the output voltage phase difference based on the difference between the bypass voltage and the average value of the inverter output voltage in each of the multiple uninterruptible power supply modules 111. In this way, by calculating the output voltage phase difference using the average value of the inverter output voltage in each of the multiple uninterruptible power supply modules 111, the output voltage phase differences in each of the multiple uninterruptible power supply modules 111 can be made equal to each other. As a result, the frequencies of the corrected PWM carrier signals in the different uninterruptible power supply modules 111 can be made equal to each other.

[0086] Other effects of the second embodiment are similar to those of the first embodiment.

[0087] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the description of the above embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0088] For example, in the first embodiment, the power storage units 102 corresponding to the plurality of uninterruptible power supplies 10 are provided separately from each other, but the present invention is not limited to this. A common power storage unit may be provided for each of the plurality of uninterruptible power supplies 10. For example, as shown in FIG. 9, each of the plurality of uninterruptible power supplies 10 of the uninterruptible power supply system 300 is supplied with DC power from a common power storage unit 202. In this case, by using a PWM carrier signal that has been controlled to synchronize the different uninterruptible power supplies 10 in generating a PWM signal that controls the chopper 2, it is possible to suppress high-frequency cross currents from flowing between the choppers 2 of the different uninterruptible power supplies 10. The second embodiment may be configured in the same way. In addition, in the case of a configuration in which AC power is supplied to each uninterruptible power supply 10 from a common AC power source 101, it is possible to suppress high-frequency cross currents from flowing between the converters 1 of the different uninterruptible power supplies 10. The same applies to the second embodiment.

[0089] In the above first and second embodiments, the control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) performs control to reduce the phase difference (synchronization signal phase difference) between the reference synchronization signal and the PWM carrier synchronization signal of the uninterruptible power supply 10 (110) itself, but the present invention is not limited to this. The control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) may perform control to directly reduce the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply 10 (110) itself and the PWM carrier synchronization signal of the other uninterruptible power supplies 10 (110) without using the reference synchronization signal.

[0090] In the above first and second embodiments, the control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) performs control to reduce the phase difference (synchronization signal phase difference) between the central phase of the reference synchronization signal and the central phase of the PWM carrier synchronization signal of the uninterruptible power supply 10 (110) itself, but the present invention is not limited to this. The control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) may perform control to reduce the phase difference between a predetermined phase other than the central phase of the reference synchronization signal (for example, the phase at which the reference synchronization signal falls to L) and a predetermined phase other than the central phase of the PWM carrier synchronization signal of the uninterruptible power supply 10 (110) itself (for example, the phase at which the PWM carrier synchronization signal falls to L).

[0091] In the above first and second embodiments, the control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) generates a reference synchronization signal that is an OR signal of the PWM carrier synchronization signal of the uninterruptible power supply 10 (110) in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies 10 (110), but the present invention is not limited to this. Each of the control units 6 (16) of the multiple uninterruptible power supplies 10 (110) may generate a reference synchronization signal that is an AND signal of the PWM carrier synchronization signal of the uninterruptible power supply 10 (110) in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supplies 10 (110). In this case, the reference synchronization signal and each PWM carrier synchronization signal are H active (H state is active) signals.

[0092] In the above first and second embodiments, the control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) performs control to reduce the output voltage phase difference and the synchronization signal phase difference, but the present invention is not limited to this. The control unit 6 (16) of each of the multiple uninterruptible power supplies 10 (110) may perform control to reduce the synchronization signal phase difference without performing control to reduce the output voltage phase difference.

[0093] In the above first and second embodiments, the control unit 6 (16) is provided with the dead zone processing unit 60b, but the present invention is not limited to this. The control unit 6 (16) does not necessarily have to be provided with the dead zone processing unit 60b.

[0094] In the first and second embodiments, when the input value of the dead band processor 60b is outside the range of the dead band, the dead band processor 60b outputs the difference between the input value and the range of the dead band, but the present invention is not limited to this. When the input value of the dead band processor is outside the range of the dead band, the dead band processor may output the input value as it is.

[0095] In the above first and second embodiments, the PI regulator 60a (proportional controller) that performs proportional control and integral control is provided in the control unit 6 (16), but the present invention is not limited to this. Instead of the PI regulator 60a, a PID regulator that performs differential control in addition to proportional control and integral control may be provided in the control unit 6 (16).

[0096] In the above first and second embodiments, an example has been shown in which three uninterruptible power supply devices 10 (110) are connected in parallel, but the present invention is not limited to this. Two or four or more uninterruptible power supply devices 10 (110) may be connected in parallel. In the second embodiment, each uninterruptible power supply device 110 may be provided with two or four or more uninterruptible power supply modules 111.

[0097] In the above first and second embodiments, an example has been shown in which one control unit 6 (16) is provided in each uninterruptible power supply 10 (110), but the present invention is not limited to this. Each uninterruptible power supply 10 (110) may be provided with multiple control units. In the second embodiment, each uninterruptible power supply module 111 may be provided with a control unit. [Explanation of symbols]

[0098] 1 Converter 3 Inverter 6, 16 Control section 10, 10a, 10b, 10c, 110, 110a, 110b, 110c uninterruptible power supply 11 First power path 12 Second power path 60a PI regulator (proportional controller) 60c low pass filter 100, 200, 300 Uninterruptible Power System 101 AC power supply 102, 202 Storage unit 103 Load 111 Uninterruptible power supply module (uninterruptible power supply section) Period A (first period) Period B (Second Period)

Claims

1. A plurality of uninterruptible power supplies connected in parallel to each other and supplying power to a load, Each of the plurality of uninterruptible power supplies includes a converter that converts AC power supplied from an AC power source into DC power, an inverter that converts DC power supplied from the converter or a power storage unit that stores DC power into AC power, and a control unit that generates a PWM carrier signal that is a reference for a PWM signal that controls the converter and the inverter, an uninterruptible power supply system, wherein the control unit of each of the plurality of uninterruptible power supplies is configured to generate a PWM carrier synchronization signal for synchronizing the PWM carrier signals between the different uninterruptible power supplies, and to perform control to reduce a PWM carrier phase difference, which is the phase difference between the PWM carrier signal of the uninterruptible power supply in which it is installed and the PWM carrier signals in the other uninterruptible power supplies, by correcting the frequency of the PWM carrier signal based on the PWM carrier synchronization signal.

2. 2. The uninterruptible power supply system of claim 1, wherein the control unit of each of the plurality of uninterruptible power supply devices is configured to perform control to reduce the phase difference between the PWM carriers by correcting the frequency of the PWM carrier signal so that the phase difference between the PWM carrier synchronization signal of the uninterruptible power supply device in which the control unit is provided and the PWM carrier synchronization signal of the other uninterruptible power supply devices is reduced.

3. 3. The uninterruptible power supply system of claim 2, wherein the control unit of each of the plurality of uninterruptible power supplies is configured to generate a reference synchronization signal based on the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supply, and to perform control to reduce a synchronization signal phase difference, which is the phase difference between the reference synchronization signal and the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided, thereby performing control to reduce a phase difference between the PWM carrier synchronization signal of the uninterruptible power supply in which it is provided and the PWM carrier synchronization signal of the other uninterruptible power supply.

4. 4. The uninterruptible power supply system of claim 3, wherein the control unit of each of the plurality of uninterruptible power supply devices is configured to generate the reference synchronization signal across a first period during which the PWM carrier synchronization signal of the uninterruptible power supply device in which the control unit is provided becomes a predetermined value and a second period during which the PWM carrier synchronization signal of the other uninterruptible power supply devices becomes the predetermined value.

5. each of the plurality of uninterruptible power supplies includes a first power path that supplies power from the inverter to the load, and a second power path that is provided separately from the first power path and supplies power from an external source to the load without passing through the converter and the inverter; 5. The uninterruptible power supply system according to claim 3, wherein the control unit of each of the plurality of uninterruptible power supplies is configured to perform control to reduce each of an output voltage phase difference, which is a phase difference between the bypass voltage and the inverter output voltage, and the synchronization signal phase difference, by correcting the frequency of the PWM carrier signal when synchronizing the phase of the inverter output voltage output from the inverter of the uninterruptible power supply device in which the control unit is provided, with a phase of a bypass voltage input from outside via the second power path to each of the plurality of uninterruptible power supplies.

6. 6. The uninterruptible power supply system according to claim 5, wherein the control unit of each of the plurality of uninterruptible power supply devices is configured to control the frequency of the inverter output voltage to a rated frequency when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized, and to perform control to reduce the synchronization signal phase difference by correcting the frequency of the PWM carrier signal.

7. 7. The uninterruptible power supply system according to claim 6, wherein the control unit of each of the plurality of uninterruptible power supply devices is configured to perform control to set a correction amount of the frequency of the PWM carrier signal to 0 when the phase of the inverter output voltage and the phase of the bypass voltage are not synchronized and when the value of the synchronization signal phase difference is within a dead band between a negative first value and a positive second value.

8. 8. The uninterruptible power supply system according to claim 5, wherein the control unit of each of the plurality of uninterruptible power supplies has a proportional controller that performs at least proportional control using as an input value a value calculated by adding a value based on the synchronization signal phase difference and the output voltage phase difference, and is configured to calculate a carrier frequency determination value that determines the frequency of the PWM carrier signal by adding the output value of the proportional controller to a carrier frequency reference value that is a reference for the frequency of the PWM carrier signal when synchronizing the phase of the inverter output voltage and the phase of the bypass voltage, and to correct the frequency of the PWM carrier signal based on the carrier frequency determination value.

9. the control unit of each of the plurality of uninterruptible power supplies is configured to, when a phase of the inverter output voltage and a phase of the bypass voltage are not synchronized, perform control to correct a frequency of the PWM carrier signal based on a value obtained by adding an output value from a low-pass filter to a value obtained by proportional control using a value based on the synchronization signal phase difference as an input value; The uninterruptible power supply system according to any one of claims 5 to 8, wherein the input value to the low-pass filter is switched from a value other than 0 to 0 based on a change from a state in which the phase of the inverter output voltage and the phase of the bypass voltage are synchronized to a state in which they are desynchronized.

10. The uninterruptible power supply system according to any one of claims 5 to 9, wherein the control unit of each of the plurality of uninterruptible power supplies performs control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value obtained by proportionally controlling a difference between the output current value of the uninterruptible power supply in which the control unit is provided and the output current value of the inverter in which the control unit is provided, which is obtained by multiplying the output current value of the uninterruptible power supply in which the control unit is provided by a predetermined gain and the output current value of the inverter in which the control unit is provided, to a value obtained by proportionally controlling a difference between the output current value of the uninterruptible power supply in which the control unit is provided and the output current value of the inverter in which the control unit is provided.

11. each of the plurality of uninterruptible power supply devices includes a plurality of uninterruptible power supply units each including the converter and the inverter; An uninterruptible power supply system according to any one of claims 5 to 10, wherein the control unit of each of the plurality of uninterruptible power supply devices is configured to calculate the output voltage phase difference based on the difference between the bypass voltage and the average value of the inverter output voltage in each of the plurality of uninterruptible power supply units.

12. The uninterruptible power supply system according to any one of claims 3 to 11, wherein the control unit of each of the plurality of uninterruptible power supplies is configured to perform control to correct the frequency of the PWM carrier signal based on a value obtained by adding a value obtained by proportionally controlling a value based on the synchronization signal phase difference as an input value to a value obtained by proportionally controlling a second d-axis cross current component, which is a d-axis component of the difference between the average value of the output current values ​​of the plurality of uninterruptible power supplies and the output current value of the uninterruptible power supply in which the control unit is provided.

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