JP2009219252A - Method of controlling uninterruptible power supply apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of controlling an uninterruptible power supply apparatus of which power consumption of equipment required for cooling and running cost can be reduced by reducing loss of the uninterruptible power supply apparatus. <P>SOLUTION: In the uninterruptible power supply apparatus of constant commercial power feeding method, a power is supplied from an AC power supply to a load while a storage element is charged through a reactor and a power converter when the AC power supply is normal. When the AC power supply is abnormal due to blackout or the like, a DC power of the storage element is converted into an AC power using the power converter and it is supplied to the load through the reactor. After a storage element 19 is fully charged in the high-frequency charging mode for high-frequency switching of a semiconductor switch in a power converter 20, low-frequency switching of a semiconductor switch 7 or 6 in the power converter 20 is performed for shifting to the low-frequency charging mode in which the storage element 19 is charged through an inverted arm type reflux diode 12 or 13 when a semiconductor switch is off. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control method for a so-called continuous commercial power supply type uninterruptible power supply, and more particularly to an improvement in a charge control method for a storage element in the uninterruptible power supply.

FIG. 6 shows a circuit configuration of a constant commercial power supply type uninterruptible power supply.
In FIG. 6, 1 is a three-phase AC power source as a commercial power source, 2 is a switch, 3 is an output terminal to which a load (not shown) is connected, 4 is a capacitor, 5 is a reactor, 6 to 11 are semiconductor switches, 12 -17 is a free-wheeling diode, 18 is a capacitor, 19 is a storage element such as a battery, 20 is a semiconductor power converter, 30 is a U-phase current of the reactor 5, and U, V, and W are three-phase alternating current phases. .

When the three-phase AC power source 1 is healthy (during normal operation), the switch 2 is turned on to supply the AC power of the three-phase AC power source 1 as it is from the output terminal 3 to the load. At the same time, by turning on and off the semiconductor switches 6 to 11 of the power converter 20 at a high frequency, the AC power of the three-phase AC power source 1 is converted to DC power and the storage element 19 is charged.
Further, when an abnormality such as a power failure occurs in the three-phase AC power source 1 and commercial power supply becomes impossible, the switch 2 is turned off and the power converter 20 is operated as an inverter, so Electric power is converted into AC power and supplied from the output terminal 3 to the load.

FIG. 7 shows the U-phase voltage 101 of the three-phase AC power source 1 in FIG. 6, the gate signals 102 and 103 of the U-phase semiconductor switches 6 and 7, and the U-phase current waveform 104 of the reactor 5.
When the gate signal 103 of the semiconductor switch 7 is turned on when the U-phase voltage 101 of the three-phase AC power supply 1 is positive, a current flows in the U-phase of the reactor 5 in the direction from the three-phase AC power supply 1 to the semiconductor switch 7. 5 stores energy. FIG. 8 shows a part of the current flow path at this time. Specifically, the three-phase AC power source 1 → the U phase of the reactor 5 → the semiconductor switch 7 → the freewheeling diodes 15 and 17 → the reactor. 5 V, W phase → 3 phase AC power source 1.

When the gate signal 103 of the semiconductor switch 7 is turned off, the energy stored in the U phase of the reactor 5 is supplied to the capacitor 18 through the freewheeling diode 12 of the upper arm, and the storage element 19 is charged. FIG. 9 shows a part of the current flow path at this time. Specifically, the U phase of the reactor 5 → the freewheeling diode 12 → the capacitor 18 and the storage element 19 → the freewheeling diodes 15 and 17 → Reactor 5 V, W phase → 3 phase AC power source 1 → reactor 5 U phase.
The charging mode is referred to as a high frequency charging mode for convenience.

  When the gate signal 102 of the semiconductor switch 6 is turned on, a current flows in the direction from the capacitor 18 and the storage element 19 after the completion of the mode in FIG. 9 to the three-phase AC power supply 1, and the storage element 19 is discharged. FIG. 10 shows a part of the current flow path at this time. Specifically, the capacitor 18 and the storage element 19 → the semiconductor switch 6 → the U phase of the reactor 5 → the three-phase AC power source 1 → Reactor 5 V phase or W phase → semiconductor switch 9 or 11 in the on state → capacitor 18 and power storage element 19.

Conventionally, by adjusting the pulse widths of the gate signal 102 of the semiconductor switch 6 and the gate signal 103 of the semiconductor switch 7, the semiconductor switches 6 and 7 are configured so that a large amount of current flows in the direction of charging the power storage element 19. On / off control is performed at a high frequency of several kHz, and this operation is basically the same for the other V and W phases.
For this reason, the charging / discharging current of the electricity storage element 19 flows through the three-phase AC power source 1, the capacitor 4, the reactor 5, the semiconductor switches 6 to 11, the freewheeling diodes 12 to 17, the capacitor 18, and the electricity storage element 19.

  Note that a continuous commercial power supply uninterruptible power supply as shown in FIG. 6 is described in Non-Patent Document 1, Patent Document 1, and the like.

IEEJ Technical Report No. 596 “Uninterruptible Power Supply (UPS) Trends”, NO. ISSN 0919-9195, p.13 3.3.1 “Parallel Processing Method”, April 1996 JP 2006-187088 (paragraph [0003], FIG. 5 etc.)

Now, since the electric storage element 19 such as a battery is in a fully charged state during most of the normal operation, almost no charging current is required.
Nevertheless, as described above, the conventional semiconductor switches 6 to 11 are always switched at a high frequency. Therefore, the three-phase AC power source 1 to the capacitor 4, the reactor 5, the semiconductor switches 6 to 11, and the freewheeling diodes 12 to 17 are used. A current always flows through the capacitor 18 and the storage element 19.

For this reason, there is a problem that switching loss and loss in each circuit element become large, lowering the efficiency of the apparatus, and when cooling with a fan or the like to process the loss, further driving power of the fan is required. .
Driving the fan not only reduces the efficiency, but also causes inconveniences such as increased noise and maintenance of the fan. Further, when the apparatus is installed indoors, an air conditioner or the like is required for indoor cooling, and there is a problem that running cost is further increased due to power consumption and maintenance.

  Therefore, the problem to be solved by the present invention is to provide a control method for an uninterruptible power supply apparatus that reduces the loss of the always commercial power supply type uninterruptible power supply apparatus and reduces the power consumption and running cost of facilities required for cooling and the like. is there.

In order to solve the above-described problem, the invention according to claim 1 is configured to supply power from the AC power source to a load when the AC power source is healthy, and to charge the storage element via a reactor and a semiconductor power converter. In an uninterruptible power supply of a commercial power supply system that converts the direct current power of the electricity storage element into alternating current power by the power converter and supplies the load to the load through the reactor at the time of abnormality,
After the power storage element is fully charged in a high frequency charging mode in which the semiconductor switch of the power converter is switched at a high frequency, the semiconductor switch of the lower arm or the upper arm of the power converter is switched at a low frequency, and the semiconductor switch When the switch is turned off, the semiconductor switch shifts to a low-frequency charging mode in which the storage element is charged by a charging current flowing through a free-wheeling diode in the reverse arm.

The invention according to claim 2 is the control method of the uninterruptible power supply device according to claim 1,
In the low-frequency charging mode, the lower arm or the upper arm semiconductor switch is switched at the frequency of the AC power supply.

The invention according to claim 3 is the control method of the uninterruptible power supply device according to claim 1,
In the low frequency charging mode, the semiconductor switch is switched near the peak value of the phase voltage of the AC power supply.

The invention according to claim 4 is the control method of the uninterruptible power supply device according to claim 1,
In the low-frequency charging mode, any one of the semiconductor switches of the upper arm and any of the semiconductor switches of the lower arm are alternately switched at a frequency n (n is an integer) times the frequency of the AC power supply.

The invention according to claim 5 is the control method of the uninterruptible power supply device according to claim 1,
In the low-frequency charging mode, all the semiconductor switches of the upper arm and all the semiconductor switches of the lower arm are switched alternately.

The invention according to claim 6 is the control method of the uninterruptible power supply according to any one of claims 1 to 5,
When the state where the charging current of the power storage element is equal to or lower than a predetermined value has elapsed for a predetermined time, the high frequency charging mode is shifted to the low frequency charging mode.

The invention according to claim 7 is the control method of the uninterruptible power supply according to any one of claims 1 to 5,
When the voltage of the power storage element becomes equal to or higher than a predetermined value, the high frequency charging mode is shifted to the low frequency charging mode.

The invention according to claim 8 is the control method of the uninterruptible power supply device according to any one of claims 1 to 7,
When the voltage of the power storage element becomes lower than a certain value (for example, when a backup operation due to a power failure is performed for a certain period and then power is restored, or when the voltage of the power storage element becomes lower than a certain value for some reason) Furthermore, the low frequency charging mode is shifted to the high frequency charging mode.

The invention according to claim 9 is the control method of the uninterruptible power supply according to any one of claims 1 to 8,
The on-pulse width of the semiconductor switch in the low-frequency charging mode can be selected according to the voltage of the storage element.

The invention according to claim 10 is the control method of the uninterruptible power supply device according to claim 9,
When the on-pulse width of the semiconductor switch in the low-frequency charging mode exceeds a predetermined value, the semiconductor switch is turned on by a pulse train composed of a plurality of pulses included in the on-pulse width.

  According to an eleventh aspect of the present invention, when the voltage of the power storage element becomes equal to or higher than a first predetermined value, the operation shifts to the low-frequency charging mode switching operation according to any one of the fourth, fifth, and tenth aspects. Then, when the voltage of the power storage element becomes equal to or higher than a second predetermined value higher than the first predetermined value, the operation shifts to the switching operation in the low frequency charging mode according to claim 2.

According to the present invention, when the storage element is fully charged, the switching loss is reduced by shifting from the high-frequency charging mode to the low-frequency charging mode, and the burden on the cooling device such as a fan or an air conditioner is reduced. Running costs can be reduced.
In addition, since most of the ripple current accompanying switching in the low frequency charging mode flows to the capacitor, there is no fear of reducing the life of the storage element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the circuit configuration of the continuous commercial power supply type uninterruptible power supply to which this embodiment is applied is the same as FIG.
FIG. 1 is a time chart showing the operation of the embodiment of the present invention. This time chart is after the storage element 19 is fully charged and requires a large amount of charging power until it is fully charged. Therefore, the semiconductor switches 6 to 11 perform high-frequency switching in the same high-frequency charging mode as before. Then, the energy storage device 19 is charged with the energy accumulated in the reactor 5.

Since the charging power may be small after the storage element 19 is fully charged, as shown in FIG. 1, one phase of the power converter 20, for example, the U-phase lower arm semiconductor switch 7 is set to 1 of the U-phase voltage. Turn on once per cycle.
That is, when the gate signal 103 of the semiconductor switch 7 is turned on once when the U-phase voltage 101 of the three-phase AC power supply 1 is positive, the current flows in the direction of the U-phase of the reactor 5 from the three-phase AC power supply 1 to the semiconductor switch 7. Flows and energy is stored in the reactor 5. The current flow path at this time is as shown in FIG.

When the gate signal 103 of the semiconductor switch 7 is turned off, the energy stored in the U phase of the reactor 5 is supplied to the capacitor 18 through the freewheeling diode 12 of the upper arm, and the storage element 19 is charged. The current flow path at this time is as shown in FIG.
During this time, by turning off the gate signal 102 of the upper arm semiconductor switch 6, no current flows from the capacitor 18 and the power storage element 19 to the three-phase AC power source 1, and the power storage element 19 is not discharged.

Although not shown, when the U-phase voltage 101 of the three-phase AC power supply 1 is negative, the gate signal 102 of the upper arm semiconductor switch 6 is turned on only once, and during that time, the gate of the lower arm semiconductor switch 7 is turned on. The signal 103 may be controlled to be turned off.
In this case, energy is accumulated in the reactor 5 by the U-phase current 30 flowing in the direction opposite to that in FIG. 8, and when the gate signal 102 of the semiconductor switch 6 is turned off, the accumulated energy in the reactor 5 is the U-phase in the reactor 5. → 3-phase AC power source 1 → V and W phase of reactor 5 → circular diodes 14 and 16 → capacitor 18 and storage element 19 → circulation diode 13 → reduced by the U-phase path of reactor 5, It will be charged.

  Here, the charging mode in which the power storage element 19 is charged by switching the upper arm or the lower arm semiconductor switch at a low frequency as described above is referred to as a low frequency charging mode for convenience. The switching frequency in the low-frequency charging mode is not limited to the case where the switching frequency is the same as the frequency of the AC power supply 1 as described above, but in principle, it should be sufficiently lower than the switching frequency (several kHz) in the high-frequency charging mode.

In the above description, the case where the U-phase semiconductor switch 6 or 7 is turned on / off according to the positive / negative of the U-phase voltage 101 has been described. However, the V-phase semiconductor switch 8 or 9 is turned on / off according to the positive / negative of the V-phase voltage. In this case, the same applies to the case where the W-phase semiconductor switch 10 or 11 is turned on / off in accordance with the sign of the W-phase voltage.
This significantly reduces the number of times the charging current flows through the circuit elements in the uninterruptible power supply when fully charged, so switching loss and circuit element losses are reduced compared to the conventional case of charging only in the high-frequency charging mode. It is possible to reduce the cost of the cooling device such as a fan or an air conditioner, thereby reducing the equipment cost and the running cost.

Furthermore, in the example of FIG. 1, only the gate signal 103 of the semiconductor switch 7 is turned on once when the U-phase voltage 101 is positive. In addition, when the U-phase voltage 101 is negative, the gate of the semiconductor switch 6 is turned on. The signal 102 may be turned on once. That is, it is possible to turn on not only once in one cycle of the AC power supply voltage but once in the positive half cycle and once in the negative half cycle (twice in one cycle in total).
Alternatively, in general, any semiconductor switch in the upper arm and any semiconductor switch in the lower arm may be alternately switched at a frequency n (n is an integer) times the frequency of the AC power supply.
Further, the timing for turning on once in one cycle or half cycle may be performed in the vicinity of the peak value of the phase voltage. Since the voltage is high near the peak value, a large amount of energy can be stored in the reactor 5 when the gate signal is turned on, and the power storage element 19 can be efficiently charged in a short on-time.

It is also possible to charge the power storage element 19 by intermittently performing high-frequency switching of the power converter 20, but in that case, a large charging current flows and the peak value of the ripple current increases, and this ripple There is a possibility that the current flows through the electric storage element 19 to shorten its life.
On the other hand, according to the present embodiment, the peak value of the ripple current in the low-frequency charging mode does not become larger than the current defined by the on-pulse width of the semiconductor switch, and most of the current flows through the capacitor 18, so that the storage element 19 There is no risk of reducing the life of the product.

In the present embodiment, it is necessary to determine that the storage element 19 is fully charged and shift from the high frequency charging mode to the low frequency charging mode.
Here, the electric storage element 19 has a characteristic that the charging current gradually decreases as it approaches full charge, and the charging current finally has a very small value. Therefore, it can be determined that the storage element 19 is fully charged if it is detected that the charging current to the storage element 19 has become a certain current or less. However, since the charging current is very small and there is a problem with its detection accuracy, the state where the charging current has become very small is determined for a certain period of time, and the fully charged state is judged, and the high frequency charging mode is switched to the low frequency charging mode. Just do it.

Moreover, when the electrical storage element 19 is no longer in a fully charged state, it is necessary to shift from the low frequency charging mode to the high frequency charging mode to return to the fully charged state.
For example, at the time of backup operation due to a power failure, since the power storage element 19 is discharged and the power converter 20 is operated as an inverter, the power storage element 19 is not fully charged, so the voltage of the power storage element 19 decreases. Further, even during backup operation, the amount of electricity stored in the electricity storage element 19 may decrease due to some cause, and the voltage may decrease.

For this reason, the voltage of the electrical storage element 19 is always detected, and control may be performed so as to shift from the low frequency charging mode to the high frequency charging mode when the voltage becomes a certain value or less.
In the pulse width control of the semiconductor switch in the low-frequency charging mode, several stages of pulse widths are prepared from pulse off (on pulse width zero) to a predetermined on pulse width, and the voltage detection value (voltage detection value) of the storage element 19 is prepared. It is desirable that an appropriate pulse width can be selected in accordance with the deviation between the charging voltage command value and the charging voltage command value.

  Next, FIG. 2 shows a configuration example of an always commercial power supply type uninterruptible power supply to which the embodiment of the present invention is applied. In FIG. 2, the configuration of the main circuit is the same as that in FIG. 6, and the same reference numerals are given to the same components, but in FIG.

  In FIG. 2, VT is a voltage detector that detects the voltage of the storage element 19, DCCT is a current detector that detects the charging current flowing through the storage element 19, and SWC is a switching signal based on detection signals from the detectors VT and DCCT. AVR is a voltage regulator for controlling the voltage of the storage element 19 to a predetermined value, CW is a carrier generator, CP is an output signal of the voltage regulator AVR and a carrier from the carrier generator CW Is a comparator that generates a high-frequency pulse, PPD is a peak phase detection circuit that detects a peak phase of the phase voltage of the three-phase AC power supply 1, and PG1 to PG3 are predetermined based on the peak phase and the voltage of the storage element 19 A pulse generator SW1 that generates a low-frequency pulse having a width, and a low frequency pulse from the pulse generators PG1 to PG3 and a high frequency from the comparator CP A pulse distribution circuit that generates a turn-on signal of the semiconductor switches 6 to 11 of the power converter 20 based on the pulse output from the change-over switch SW1 and distributes it to each switch. It is.

In the above configuration, when the switch switching circuit SWC detects that the storage element 19 is not fully charged from the detection signal of the voltage detector VT or the current detector DCCT, in order to operate in the high frequency charging mode, the selector switch SW1 Is switched to the comparator CP side, and the high frequency pulse output from the comparator CP is distributed by the pulse distribution circuit PDIV to be an on / off signal for the semiconductor switches 6 to 11 of the power converter 20.
Further, when the switch switching circuit SWC detects that the storage element 19 is fully charged from the detection signal of the voltage detector VT or the current detector DCCT, the changeover switch is operated to operate in the low frequency charging mode. SW1 is switched to the pulse generators PG1 to PG3, and the low frequency pulse output from the pulse generators PG1 to PG3 is distributed by the pulse distribution circuit PDIV to be an on / off signal for the semiconductor switches 6 to 11.

3 to 5 are time charts showing the operation of the pulse distribution circuit PDIV in the low frequency charging mode.
First, FIG. 3 is an example in which a pulse is generated near the peak value of the phase voltage of the AC power supply 1 and the pulse is distributed to the semiconductor switches 6 to 11 of the power converter 20. In this example, a pulse is generated near the peak value on both the positive and negative sides of each phase voltage, and one of the upper arm semiconductor switches and one of the lower arm semiconductor switches are alternately turned on (in one cycle of each phase voltage). 6), the generated loss of each semiconductor switch is equalized, the uniform cooling mechanism can be used, and the loss is not biased to a specific semiconductor switch, resulting in an unbalanced life It becomes difficult. In this example, a pulse is generated near the peak value on both the positive and negative sides of each phase voltage of the AC power supply, but a pulse is generated only on either the positive or negative side (ON three times in one cycle of each phase voltage). Even so, there is no problem with the charging function. If it is acceptable that the generated loss of the semiconductor switch is not uniform, a pulse is generated only in one specific phase or two phases (on twice or four times in one cycle of each phase voltage). Also good.

Next, FIG. 4 shows that when the pulse is distributed to any one semiconductor switch (for example, the semiconductor switch 6 marked “ON” in the vicinity of the pulse) in FIG. The pulses are also distributed to the semiconductor switches of the arm (for example, semiconductor switches 8 and 10 in which the pulses are shaded), and similarly, any one semiconductor switch of the lower arm (for example, “ON” in the vicinity of the pulse) This is an example of distributing pulses to the remaining lower-arm semiconductor switches (for example, semiconductor switches 7 and 9 in which the pulses are shaded) at the same timing when the pulses are distributed to the semiconductor switches 11).
In this case, as a result, all the semiconductor switches 6, 8, and 10 in the upper arm and all the semiconductor switches 7, 9, and 11 in the lower arm are alternately turned on and off, which is the same as the example of FIG. The charging function can be obtained, and the generated loss of the semiconductor switches 6 to 11 is also equalized. According to this example, there is an advantage that the operation of the pulse distribution circuit PDIV is simplified.

Furthermore, FIG. 5 shows that when the voltage of the storage element 19 is lowered and the pulse width for turning on the semiconductor switch is widened to increase the charging power, when the pulse width exceeds a predetermined value, the pulse width is set to a plurality of values. It is a wave form diagram when comprising by the pulse train which consists of a pulse. That is, as shown in the upper part of FIG. 5, AND logic elements are provided on the output sides of the pulse generators PG1 to PG3, respectively, and the logical product of the signal A and the high-frequency signal B output from the pulse generators PG1 to PG3. A signal C of a pulse train including a plurality of pulses within a predetermined pulse width (pulse width of the signal A) can be obtained, and this signal C is input to the pulse distribution circuit PDIV via the change-over switch SW1 to switch the semiconductor switch. Turn it on.
When the pulse width of the signal A exceeds a predetermined value, the reactor 5 is magnetically saturated and an overcurrent flows through the semiconductor switch. However, according to the method shown in FIG. 5, a plurality of pulses generated within the pulse width of the signal A By turning on and off the semiconductor switch by the signal C comprising the above, it is possible to prevent the magnetic saturation of the reactor 5 and to suppress the overcurrent from flowing through the semiconductor switch.

The determination of the fully charged state of the storage element 19 may be performed by detecting the voltage of the storage element 19 in addition to detecting the magnitude of the charging current. That is, it can be determined by the voltage detector VT that the voltage of the electric storage element 19 has become equal to or higher than a predetermined value, and it is determined that the battery is fully charged, and the high frequency charging mode can be shifted to the low frequency charging mode.
In this case, the above-described high-frequency charging mode in FIG. 7 may be directly shifted to the low-frequency charging mode in FIG. 1, but the voltage of the storage element 19 is the first during charging in the high-frequency charging mode in FIG. When the value exceeds the predetermined value, first, the mode is shifted to the mode of FIG. 3, the mode of FIG. 4, or the mode of FIG. 5 (or the mode of FIG. 3 or the mode of FIG. 4 → the mode of FIG. 5 is sequentially shifted). Then, after that, when the voltage of the electric storage element 19 becomes equal to or higher than a second predetermined value (second predetermined value> first predetermined value), the low frequency charging mode of FIG.

It is a time chart which shows operation | movement of embodiment of this invention. 1 is an overall configuration diagram of a continuous commercial power supply uninterruptible power supply to which an embodiment of the present invention is applied. It is a time chart which shows the operation | movement of the pulse distribution circuit in FIG. It is a time chart which shows the operation | movement of the pulse distribution circuit in FIG. FIG. 3 is a time chart showing an operation when a pulse width for turning on a semiconductor switch in FIG. 2 is wide. It is a main circuit block diagram of a continuous commercial power feeding system uninterruptible power supply. It is a time chart which shows operation | movement of a prior art. It is a main circuit block diagram for demonstrating the energy storage operation | movement to a reactor. It is a main circuit block diagram for demonstrating the charge operation to an electrical storage element. It is a main circuit block diagram for demonstrating the discharge operation from an electrical storage element.

Explanation of symbols

1: Three-phase AC power supply 2: Switch 3: Output terminal 4: Capacitor 5: Reactor 6-11: Semiconductor switch 12-17: Free-wheeling diode 18: Capacitor 19: Power storage device 20: Semiconductor power converter 30: U of reactor 5 Phase current VT: Voltage detector DCCT: Current detector AVR: Voltage regulator CW: Carrier generator CP: Comparator PDIV: Pulse distribution circuit SWC: Switch switching circuit SW1: Changeover switch PG1 to PG3: Pulse generator PPD: Peak phase Detection circuit

Claims (11)

When the AC power supply is healthy, power is supplied from the AC power supply to the load and the storage element is charged via a reactor and a power converter. When the AC power supply is abnormal, the DC power of the storage element is supplied to the AC power by the power converter. In an uninterruptible power supply of a continuous commercial power supply system that converts to the load through the reactor and supplies it to the load,
After the power storage element is fully charged in a high frequency charging mode in which the semiconductor switch of the power converter is switched at a high frequency, the semiconductor switch of the lower arm or the upper arm of the power converter is switched at a low frequency, and the semiconductor switch A control method for an uninterruptible power supply, characterized in that a transition is made to a low-frequency charging mode in which the storage element is charged by a charging current flowing through a free-wheeling diode having an arm opposite to that of the semiconductor switch. In the control method of the uninterruptible power supply according to claim 1,
A control method for an uninterruptible power supply, characterized in that, in the low-frequency charging mode, the lower arm or the upper arm semiconductor switch is switched at the frequency of the AC power supply. In the control method of the uninterruptible power supply according to claim 1,
A control method for an uninterruptible power supply, characterized in that, in the low-frequency charging mode, the semiconductor switch is switched near the peak value of the phase voltage of the AC power supply. In the control method of the uninterruptible power supply according to claim 1,
In the low-frequency charging mode, any one of the semiconductor switches of the upper arm and any of the semiconductor switches of the lower arm are alternately switched at a frequency n (n is an integer) times the frequency of the AC power supply. To control the uninterruptible power supply.
In the control method of the uninterruptible power supply according to claim 1,
In the low-frequency charging mode, the control method of the uninterruptible power supply apparatus, wherein all the semiconductor switches of the upper arm and all the semiconductor switches of the lower arm are switched alternately. In the control method of the uninterruptible power supply according to any one of claims 1 to 5,
A control method for an uninterruptible power supply, wherein when a state in which a charging current of the power storage element is equal to or less than a certain value has elapsed for a certain period of time, the high frequency charging mode is shifted to the low frequency charging mode. In the control method of the uninterruptible power supply according to any one of claims 1 to 5,
The control method for an uninterruptible power supply, wherein when the voltage of the power storage element becomes equal to or higher than a predetermined value, the high frequency charging mode is shifted to the low frequency charging mode. In the control method of the uninterruptible power supply according to any one of claims 1 to 7,
When the voltage of the said electrical storage element becomes below a fixed value, it transfers to the said high frequency charge mode from the said low frequency charge mode, The control method of the uninterruptible power supply characterized by the above-mentioned. In the control method of the uninterruptible power supply according to any one of claims 1 to 8,
A control method for an uninterruptible power supply, wherein an on-pulse width of a semiconductor switch in the low-frequency charging mode can be selected in accordance with a voltage of the power storage element. In the control method of the uninterruptible power supply according to claim 9,
A control method for an uninterruptible power supply, wherein the semiconductor switch is turned on by a pulse train comprising a plurality of pulses included in the on-pulse width when the on-pulse width of the semiconductor switch in the low-frequency charging mode exceeds a predetermined value. .   When the voltage of the power storage element becomes equal to or higher than a first predetermined value, the operation shifts to the low-frequency charging mode switching operation according to any one of claim 4, claim 5, or claim 10, and then The control method for an uninterruptible power supply, wherein the operation shifts to a switching operation in a low-frequency charging mode according to claim 2 when the voltage becomes equal to or higher than a second predetermined value higher than the first predetermined value.

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