JP2013009463A - Switching method of uninterruptible power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching method of an uninterruptible power supply device capable of preventing an excitation rush current at power recovery switching.SOLUTION: An uninterruptible power supply device has a switch 14 for switching between commercial power feeding for outputting a power from a commercial AC power supply 2 to a commercial transformer 3 that is a load and inverter power feeding for outputting a power from an accumulator battery 12 to the commercial transformer 3 via an inverter 13. When the commercial AC power supply 2 returns to a normal condition from an abnormal condition, a phase of an output voltage of the inverter 13 is advanced to a phase of a commercial input voltage of the commercial AC power supply 2 by a switching time period of the switch 14, and then, the switch 14 is switched from the inverter power feeding to the commercial power feeding.

Description

  The present invention relates to a switching method for an uninterruptible power supply that switches a power supply source between a normal time and an abnormal time, and more particularly to a switching method for an uninterruptible power supply of a constant commercial power supply system.

  When an abnormality occurs in the commercial AC power supply (for example, a momentary voltage drop or interruption), the electronic device such as a computer that operates with the power from the commercial AC power supply malfunctions (for example, loss of information or Breakage). Therefore, in order to solve such problems, an uninterruptible power supply (UPS) has been introduced. The uninterruptible power supply supplies power from the commercial AC power supply to the electronic equipment when the commercial AC power supply is normal. When the commercial AC power supply is abnormal, the uninterruptible power supply supplies power from the built-in storage battery via the inverter. It is supplied to electronic equipment.

  An uninterruptible power supply system called a regular commercial power supply system performs commercial power supply (commercial direct transmission operation) that directly outputs power from a commercial AC power supply when the commercial AC power supply is normal, and in parallel to the storage battery When power is stored and the commercial AC power supply is abnormal, inverter power feeding (backup operation) is performed to output power from the storage battery via the inverter. When a commercial transformer is connected as a load to the output of such a continuous commercial power supply uninterruptible power supply, in most cases when switching power is switched from inverter power supply to commercial power supply, an inrush current is applied to the commercial transformer. Will occur. If a magnetizing inrush current occurs at the time of power recovery switching, the input voltage of the commercial AC power supply may decrease, and this decrease in input voltage may be recognized as abnormal by the commercial AC power supply, and inverter power feeding may be repeated. .

  In a continuous commercial power supply uninterruptible power supply, a switch is used to switch between a normal power supply and an abnormal power supply, that is, a switch between commercial power supply and inverter power supply. Time T is required. Therefore, as shown in FIG. 4, when power recovery switching is performed at time t1, inverter power feeding is stopped at time t1, and commercial power feeding is started at time t2 when the switching time T has elapsed from time t1. FIG. 4 shows an example in which the output voltage waveform of the inverter power supply and the output voltage waveform of the commercial power supply are synchronized. In the example shown in FIG. 4, the switching time T is required for power recovery switching. As a result, the balance between the upper and lower areas of the output voltage waveform is lost, and the magnetizing inrush current flows through the commercial transformer of the load. When the power recovery switching timing is near the peak, the balance between the upper and lower areas of the output voltage waveform is greatly disrupted, so the magnetizing inrush current increases and the power recovery switching timing is near the zero cross. Because the collapse of the upper and lower areas of the output voltage waveform is reduced, the magnetizing inrush current is reduced.

In order to prevent such a magnetizing inrush current, it is conceivable to control the power recovery switching timing, that is, the timing to stop inverter power feeding or the timing to start commercial power feeding (for example, see Patent Document 1).
In Patent Document 1, switching start timing (timing for stopping inverter feeding) is controlled according to the phase difference between two AC power sources (inverter feeding and commercial feeding) and the instantaneous interruption time (switching time T) at the time of switching. is doing.

Japanese Patent Laid-Open No. 54-131636

  However, when controlling the power recovery switching timing, that is, the timing for stopping the inverter power feeding or the timing for starting the commercial power feeding as in Patent Document 1, the power switching is performed promptly after the commercial AC power supply is restored. There is a problem in that it cannot be performed or the non-power-feed time becomes longer than the switch switching time T.

  In view of the above problems, an object of the present invention is to provide a switching method for an uninterruptible power supply that can solve the problems of the prior art and prevent an inrush current during switching of power recovery.

The switching method of the uninterruptible power supply of the present invention comprises a switch that switches between commercial power supply that outputs power from a commercial AC power source to a load and inverter power supply that outputs power from a storage battery to the load via an inverter, When the commercial AC power supply is normal, the switch is switched to the commercial power supply, and at the same time, the power is stored in the storage battery. When the commercial AC power supply is abnormal, the switch is switched to the inverter power supply. In the switching method of the uninterruptible power supply, when the commercial AC power supply returns to normal from an abnormality, the phase of the output voltage of the inverter power supply is set to the phase of the commercial input voltage of the commercial power supply. It is characterized in that the switch is switched from the inverter power supply to the commercial power supply after advancing for the switching time.
Furthermore, in the uninterruptible power supply of the present invention, the load is a commercial transformer.

  According to the present invention, when switching the switch from the inverter power supply to the commercial power supply, the phase of the output voltage of the inverter power supply is switched after the switch switching time is advanced with respect to the phase of the commercial power supply commercial voltage, The balance of the upper and lower areas of the output voltage waveform to the load is not lost, and the effect of preventing the magnetizing inrush current at the time of switching power recovery can be achieved.

It is a circuit block diagram which shows the circuit structure of embodiment of the uninterruptible power supply device which concerns on this invention. It is a flowchart for demonstrating the power recovery switching process in embodiment of the uninterruptible power supply which concerns on this invention. It is a figure which shows the output voltage waveform at the time of the recovery switching in embodiment of the uninterruptible power supply which concerns on this invention. It is a figure which shows the output voltage waveform at the time of power recovery switching in the conventional uninterruptible power supply.

Next, embodiments of the present invention will be specifically described with reference to the drawings.
Referring to FIG. 1, uninterruptible power supply device 1 of the present embodiment includes charger 11, storage battery 12, inverter 13, switch 14, and controller 15, and commercial AC power supply 2 at input terminal 16. However, the commercial transformer 3 as a load is connected to the output terminal 17.

  The charger 11 is connected to the input terminal 16 of the uninterruptible power supply 1 and converts the AC voltage input from the commercial AC power supply 2 connected to the input terminal 16 into a DC voltage of a predetermined level. The charger 11 is connected to the storage battery 12 and applies the converted DC voltage to the storage battery 12 to charge the storage battery 12.

  The storage battery 12 is a backup power source (backup power source) such as various secondary batteries, capacitors, electric double layer capacitors, flywheels, etc. When an abnormality such as a power failure occurs in the commercial AC power source 2 connected to the input terminal 16, Power is supplied to the commercial transformer 3 which is a load connected to the output terminal 17.

  The inverter 13 is the same as the commercial input voltage input from the commercial AC power supply 2 under the control of the control unit 15 when an abnormality occurs in the commercial AC power supply 2 (for example, an instantaneous voltage drop or instantaneous interruption). The DC voltage of the storage battery 12 is converted into an AC voltage having a frequency and substantially the same voltage level and output. Further, when the commercial AC power supply 2 returns to normal, the inverter 13 advances the phase of the output voltage by the switching time T of the switch 14 as compared with the commercial input voltage of the commercial AC power supply 2 under the control of the control unit 15.

  The switch 14 is controlled by the control unit 15 so as to directly output power from the commercial AC power supply 2 (commercial direct transmission operation) and inverter power supply that outputs power from the storage battery 12 via the inverter 13 (backup operation). Switching means for switching between. That is, the switch 14 switches the input to the input terminal 16 side in the commercial power supply and directly connects the input terminal 16 and the output terminal 17, and switches the input to the inverter 13 side in the inverter power supply to the inverter 13 and the output terminal. 17 is connected. Further, the switching time T required for switching the switch 14 is fixed, and when the switching is instructed by the control unit 15, one connected input is disconnected and then connected to the other input after the switching time T. Is done.

  The control unit 15 monitors the commercial input voltage from the commercial AC power supply 2 connected to the input terminal 16, and controls the switch 14 and the inverter 13 when an abnormality such as a power failure occurs in the commercial AC power supply 2. Thus, switching to inverter power feeding that outputs power from the storage battery 12 via the inverter 13 is performed. The switching to the inverter power supply is performed by switching the input of the switch 14 to the inverter 13 side, connecting the inverter 13 and the output terminal 17, and converting the DC voltage of the storage battery 12 into an AC voltage by the inverter 13. An alternating voltage is output from the output terminal 17. In addition, when the commercial AC power supply 2 returns to normal, the control unit 15 controls the inverter 13 and the switch 14 to switch to the commercial power supply (commercial direct feed operation) that directly outputs the power from the commercial AC power supply 2. Perform switching. In the power recovery switching, the phase of the output voltage is advanced by the switching time T of the switch 14 by the inverter 13 as compared with the commercial input voltage of the commercial AC power supply 2, and then the input of the switch 14 is switched to the input terminal 16 side. The terminal 16 and the output terminal 17 are directly connected, and the commercial input voltage of the commercial AC power supply 2 is output from the output terminal 17.

Next, the power recovery switching process in the uninterruptible power supply 1 of the present embodiment will be described in detail with reference to FIGS. 2 and 3.
In the state where the commercial AC power supply 2 is abnormal, the uninterruptible power supply 1 is switched to inverter power feeding. In this way, when switching to the inverter power supply, the control unit 15 periodically executes the power recovery switching process as shown in FIG.

  First, the control unit 15 determines whether or not the commercial AC power supply 2 has returned to normal, that is, whether or not the commercial input voltage from the commercial AC power supply 2 has recovered (Step S1). If the commercial input voltage is not restored, the restoration switching process is terminated.

  FIG. 3A shows a commercial input voltage waveform from the commercial AC power supply 2. In step S1, as shown in FIG. 3A, when the commercial input voltage from the commercial AC power supply 2 is restored, the control unit 15 changes the phase of the output voltage with respect to the inverter 13 to the commercial AC power supply 2 The phase adjustment is advanced by the switching time T of the switch 14 compared to the commercial input voltage (step S2).

  Next, the control unit 15 monitors whether or not the phase of the output voltage has been advanced by the switching time T of the switch 14 by the inverter 13 as compared with the commercial input voltage of the commercial AC power supply 2 (step S3). FIG. 3B shows an output voltage waveform from the inverter 13. When the phase of the output voltage of the inverter 13 is advanced by the switching time T of the switch 14 as compared with the commercial input voltage of the commercial AC power supply 2 as shown in FIG. 14 is switched from the inverter 13 side to the input terminal 16 side, switch switching for directly connecting the input terminal 16 and the output terminal 17 is executed (step S4), switching from inverter power supply to commercial power supply, and power recovery switching processing Exit.

  FIG. 3C shows an output voltage waveform from the uninterruptible power supply 1 at the time of power recovery switching. When the switch switching of step S4 is executed by the control unit 15 at time t11, inverter power feeding is stopped at time t11, and commercial power feeding is started at time t12 when the switching time T has elapsed from time t11. In the present embodiment, as described above, the phase of the output voltage of the inverter 13 is compared with the commercial input voltage of the commercial AC power source 2 by the switching time T before the switch switching of step S4 is executed. Advance phase adjustment is performed. Therefore, the commercial input voltage waveform when commercial power supply is started at time t12 is resumed from the phase at which the output voltage waveform from the inverter 13 is interrupted when the inverter power supply is stopped at time t11. Thereby, at the time of power recovery switching, the balance of the upper and lower areas of the output voltage waveform from the uninterruptible power supply device 1 at the time of power recovery switching is not disturbed, and it is possible to prevent a magnetizing inrush current from flowing into the commercial transformer of the load. be able to.

  In this embodiment, after monitoring whether or not the phase of the output voltage of the inverter 13 is advanced by the switching time T of the switch 14 as compared with the commercial input voltage of the commercial AC power supply 2 in step S3, step S4 is performed. However, the switch switching may be executed in step S4 after a predetermined time after instructing the phase adjustment in step S2. In other words, in the present embodiment, the phase of the output voltage of the inverter 13 only needs to be advanced by the switching time T of the switch 14 as compared with the commercial input voltage of the commercial AC power supply 2 when the switch is switched in step S4. After the time necessary for the above has elapsed, the switch switching in step S4 may be executed without confirming the output voltage waveform of the inverter 13.

  In the present embodiment, the phase adjustment is performed in step S2 after the commercial AC power supply 2 is restored. However, the abnormality of the commercial AC power supply 2 due to the decrease in the output level is caused when switching to the inverter power supply. However, when the commercial input voltage waveform can be recognized, the phase adjustment in step S2 may be performed during the inverter power feeding. In this case, the switch switching in step S4 can be executed immediately after the commercial AC power supply 2 is restored.

  As described above, in the present embodiment, when the commercial AC power supply 2 returns to normal from an abnormality, the phase of the output voltage of the inverter 13 is switched with respect to the phase of the commercial input voltage of the commercial AC power supply 2. Since the balance of the upper and lower areas of the output voltage waveform to the commercial transformer 3 is not disrupted by switching the switch 14 from the inverter power supply to the commercial power supply after advancing the switching time, the inrush current during the switching of power recovery is prevented. can do.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 1 Uninterruptible power supply 2 Commercial AC power supply 3 Commercial transformer 11 Charger 12 Storage battery 13 Inverter 14 Switch 15 Control part 16 Input terminal 17 Output terminal

Claims (2)

A switch that switches between a commercial power supply that outputs power from a commercial AC power source to a load and an inverter power supply that outputs power from a storage battery to the load via an inverter, and when the commercial AC power source is normal, the commercial power source A method for switching an uninterruptible power supply that switches the switch to power feeding, simultaneously stores power in the storage battery, and switches the switch to power feeding the inverter when the commercial AC power supply is abnormal,
When the commercial AC power supply returns to normal from an abnormality, the phase of the output voltage of the inverter power supply is advanced by the switching time of the switch with respect to the phase of the commercial input voltage of the commercial power supply. A method for switching an uninterruptible power supply characterized by switching the switch to the commercial power supply.   The uninterruptible power supply according to claim 1, wherein the load is a commercial transformer.

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