JP2001197683A - Uninterruptible power supply apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase reliability in the supply of power to a load. SOLUTION: This apparatus comprises a power breakdown detection means 20 for detecting power breakdown of a commercial power supply, a reference generation means 21 for outputting an output voltage reference 32 when the power breakdown of the commercial power supply is detected, a low-speed PLL means 58 which adjusts the phase, following the output power of the commercial power supply at a prescribed speed, a high-speed PLL means 59 which adjusts the phase, following the output power of the commercial power supply at a speed higher than the specified one, a switching means 60 which outputs, as an output voltage phase reference 33, the output of the low-speed PLL means 58 under normal conditions and the output of the high-speed PLL means 59, in the power breakdown of the commercial power supply, an output voltage control means 22 which outputs an output voltage command 34 for an inverter, based on the output voltage 31 of the inverter 1, the output voltage reference 32, and the output voltage phase reference 33, so that the output voltage of the inverter 1 matches with the output voltage reference, and a gate controlling means 24 which generates a gate signal 35, based on the output voltage command 34 to control the gate of the inverter 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an inverter for converting DC power into AC power and outputting the AC power, and a commercial power supply for outputting commercial power, and always supplies output power from the commercial power supply to a load. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply that switches power supply so as to supply output power from an inverter to a load when a commercial power supply fails, and more particularly to an uninterruptible power supply that can improve the reliability of power supply to a load.

[0002]

2. Description of the Related Art Conventionally, an uninterruptible power supply that supplies power from a commercial power supply directly to a load at all times and supplies power from an inverter to the load when the commercial power supply fails is used as one of the power supply apparatuses. Is coming.

FIG. 7 is a block diagram showing a configuration example of a conventional uninterruptible power supply of this type.

In FIG. 7, an output of an inverter 1 that converts DC power from a DC power supply 9 serving as power storage means into AC power and outputs the AC power is supplied to a load 6 via an inverter transformer 2.

[0005] Commercial power from a commercial power supply 7 is supplied to a load 6 via a switching circuit 3.

The switching circuit 3 includes a contactor 4 and a semiconductor switch 5 and is used to switch the power supply to the load 6 to either the inverter 1 or the commercial power supply 7.

Although the switching circuit 3 is composed of the contactor 4 and the semiconductor switch 5, it may be composed of only one of them.

The contact of the contactor 4 in the switching circuit 3 is always in a state where power is supplied from the commercial power supply 7 to the load 6.

On the other hand, when an AC input is abnormal such as a power failure of the commercial power supply 7, an output from a voltage detector 8a for detecting an output voltage from the commercial power supply 7 is input to a power failure detection circuit 20 to detect a power failure and to generate a reference signal. When the circuit 21 operates and the inverter 1 outputs a desired voltage output, power is supplied from the inverter 1 to the load 6.

Note that the DC power supply 9 may be a converter, a storage battery, or the like as long as it can constitute a DC voltage source.

The inverter output voltage 36 via the inverter transformer 2 is detected by the voltage detector 8b.

An output from the voltage detector 8b is input to an output voltage control circuit 22 in the inverter control circuit 11 as an output voltage feedback 31.

The output from the reference generation circuit 21 in the inverter control circuit 11 is input to the output voltage control circuit 22 as an output voltage reference 32.

An output from a phase locked loop (hereinafter referred to as a PLL circuit) 23 of the inverter control circuit 11 is as follows:
The output voltage phase reference 33 is input to the output voltage control circuit 22.

An output from the output voltage control circuit 22 is input to the gate control circuit 24 as an output voltage command 34.

The output from the gate control circuit 24 is connected and input to the inverter 2 as a gate signal 35.

That is, in FIG.
1 outputs an output furnace pressure reference 32 corresponding to the voltage that the uninterruptible power supply should originally output.

The output voltage control circuit 22 includes a voltage detector 8b
The feedback 31 of the output voltage detected by
Control is performed so as to be equal to the output voltage reference 32, and an output voltage command 34 is output.

Gate control circuit 24 outputs a gate signal 35 so that the output from inverter 1 matches output voltage command 34.

The inverter 1 outputs a voltage 36 according to the gate signal 35, and the winding configuration of the inverter transformer 2
The output converted by the turns ratio or the like is the output of the present uninterruptible power supply.

FIG. 8 is a circuit diagram showing a configuration example of the inverter 1.

In FIG. 8, the positive pole P of the DC power supply 9 is connected to one terminal of a DC capacitor 41.

The positive pole P of the DC power supply 9 is connected to the collectors of the switching elements 42a, 42c, 42e.

Further, these are U-phase, V-phase, and W-phase, respectively, and are the inverter output 36.

Switching elements 42b, 42d, 42f
Is connected to another terminal of the DC capacitor 41 and further connected to the negative electrode N of the DC power supply 9.

The gate drive circuit 43 has a gate signal 35
Is entered.

In practice, each switching element 42
Is provided with a snubber circuit for suppressing a surge voltage at the time of switching individually or collectively, but is omitted here for simplicity of description.

In response to the gate signal 35, the gate drive circuit 4
3 generates a dead time for preventing the switching elements connected in series vertically, for example, 42a and 42b, from being simultaneously turned on, and secures a charging / discharging period of each snubber circuit.

The inverter 1 has a pulse width modulation (PWM)
The output voltage is controlled by the control.

FIG. 9 is a block diagram showing a configuration example of the reference generation circuit 21 in the inverter control circuit 11.

In FIG. 9, voltage reference signals 51a-51
The output of c is input to multipliers 53a to 53c, respectively.

The outputs from the multipliers 53a to 53c become the output voltage reference 32 which is the output of the reference generation circuit 21.

FIG. 9 shows an example of a case in which three phases of U-phase, V-phase, and W-phase are used, and shows an example in which a constant sine-wave voltage is output.

The output voltage reference changes with time.
(For example, VVVF... Variable voltage variable frequency power supply).

The soft start signal 52 is output from the inverter 1
Is a signal that gradually raises the output voltage from zero when
This function is a temporary increase function such as a ramp function during the activation period, and becomes a constant value such as 1 after the activation is completed.

With this circuit, the uninterruptible power supply can gradually increase the output voltage at startup. This is a method generally called soft start.
FIG. 3 is a block diagram illustrating a configuration example of an output voltage control circuit in the inverter control circuit.

In FIG. 10, the difference between the output voltage reference 32 and the output voltage feedback 31 is calculated, and PI
The signals are input to the control circuits 54a to 54c, respectively.

In this embodiment, an example is shown in which PI control is used as voltage control, but PID control, IP control,
A control circuit using other general control methods or modern control theory may be used.

In FIG. 10, PI control circuits 54a to 54a-5
4c indicates that the output voltage feedback 31 is the output voltage reference 3
2 is controlled.

In particular, for the purpose of speeding up and stabilizing, a current control such as an output current may be added at a subsequent stage, a preceding stage, or in parallel with the output voltage.

Here, the illustration is omitted for the sake of simplicity.

FIG. 11 is a block diagram showing a configuration example of the gate control circuit 24 in the inverter control circuit 11.

In FIG. 11, the difference between the output voltage command 34 and the output from the carrier generation circuit 55 is calculated and input to the comparators 56a to 56c.

Outputs from the comparators 56a to 56c are input to gate signal output circuits 57a to 57c.

Outputs from the gate signal output circuits 57a to 57c become gate signals 35.

This configuration example is an example showing a triangular wave comparison method generally called. Note that the method of generating the gate pulse is not particularly limited.

[0047]

However, the conventional uninterruptible power supply as described above has the following problems.

That is, when the power supply from the inverter 1 to the commercial power supply 7 is switched to the load 6 when the commercial power supply 7 is restored, the transient response characteristic of the PLL circuit 23 is not good.

For this reason, even though the voltage of the commercial power supply 7 has been restored to the rated value, the inverter 1 and the commercial power supply 7 are not synchronized, and until the PLL circuit 23 responds sufficiently.
It is necessary to supply power from the DC power supply 9 serving as power storage means for about several seconds.

As a result, the DC power supply 9 serving as the power storage means
In addition, it is conceivable that the main circuit constituting the inverter 1 is deteriorated due to a temperature rise or the like.

If there is a voltage difference or a phase difference between the inverter 1 and the commercial power supply 7, the protection of the inverter 1 may be stopped by a cross current flowing between the inverter 1 and the commercial power supply 7.

The inverter 1 is in a standby state for a certain period after the protection is stopped.
Only.

For this reason, if a power failure occurs again in the standby state after the protection stop of the inverter 1, the power supply to the load 6 becomes impossible because the inverter 1 is inoperable, and the power supply may be stopped.

An object of the present invention is to switch the load power supply from the commercial power supply immediately after the commercial power supply is restored, thereby reducing the operation time of the inverter. It is an object of the present invention to provide a highly reliable uninterruptible power supply capable of continuously supplying power to a load without a protection stop of an inverter due to a cross current flowing between the power supply and a commercial power supply.

[0055]

According to an aspect of the present invention, there is provided an inverter comprising a plurality of switching elements for converting DC power into AC power and outputting the AC power, An uninterruptible power supply device that includes a commercial power supply that outputs power to the load, always supplies output power from the commercial power supply to the load, and switches power supply to supply output power from the inverter to the load when the commercial power supply fails. A power outage detecting unit that receives an output power from the commercial power supply and detects a power outage of the commercial power supply, and a reference generating unit that operates when a power outage of the commercial power supply is detected by the power outage detecting unit and outputs an output voltage reference. A low-speed phase synchronizing means for inputting output power from a commercial power supply, adjusting the phase by following the input power at a predetermined speed, and inputting output power from the commercial power supply. The output from the high-speed phase synchronizing means for adjusting the phase by following the input power at a speed higher than a predetermined speed and the output from the low-speed phase synchronizing means are always detected. Switching means for switching and outputting the output from the high-speed phase synchronization means at times as an output voltage phase reference, an output voltage of the inverter,
Output voltage control means for generating and outputting an inverter output voltage command based on the output voltage reference from the reference generation means and the output voltage phase reference from the switching means so that the output voltage of the inverter matches the output voltage reference. And a gate control means for generating a gate signal based on an output voltage command from the output voltage control means and controlling a gate of a switching element constituting the inverter.

Therefore, in the uninterruptible power supply according to the present invention, the low-speed phase synchronizing means receives the output power from the commercial power supply and adjusts the phase by following the input power at a predetermined speed. And high-speed phase synchronization means for receiving output power from a commercial power supply as input and adjusting the phase by following the input power at a speed higher than a predetermined speed;
Switching means for switching the output from the low-speed phase synchronizing means at all times and the output from the high-speed PLL means when the power failure detecting means detects a power failure of the commercial power supply, as an output voltage phase reference. By switching the output voltage phase reference to the output from the phase synchronization means and to the output from high-speed phase synchronization in the event of a commercial power failure, it is possible to switch to the load power supply from the commercial power supply immediately after the commercial power is restored. Operation time can be reduced. As a result, the deterioration of the main circuit constituting the DC power supply and the inverter as the power storage means does not proceed due to a rise in temperature or the like.

On the other hand, according to the second aspect of the present invention,
In the uninterruptible power supply according to the invention, means for adjusting the output voltage amplitude command of the inverter with respect to the amplitude of the output power from the commercial power supply at the time of power supply switching after the commercial power supply is restored is added.

Therefore, the uninterruptible power supply according to the second aspect of the present invention has the same effect as the first aspect of the present invention, and has the same function as that of the first aspect of the present invention when the power supply is switched after the commercial power supply is restored. Means for adjusting the output voltage amplitude command of the inverter with respect to the amplitude of the output power from the commercial power supply. When the power supply is switched after the commercial power supply is restored, the inverter adjusts the amplitude of the output power from the commercial power supply. When the power supply is switched between the inverter and the commercial power supply by adjusting the output voltage amplitude command of the inverter, the power supply to the load is continued without the protection stop of the inverter due to the cross current flowing between the inverter and the commercial power supply. Can be done. According to a third aspect of the present invention, in the uninterruptible power supply according to the first aspect of the present invention, the output voltage from the commercial power supply is switched when the power supply is switched after the commercial power supply is restored after adjusting the output voltage phase command of the inverter. Means for the phase of

Therefore, the uninterruptible power supply according to the third aspect of the present invention has the same effect as the first aspect of the present invention, and also has a commercial power supply that adjusts the output voltage phase command of the inverter. A means for adjusting the phase of the output power from the commercial power supply when the power supply is switched after the power is restored is provided. When the power supply is switched between the inverter and the commercial power supply by adjusting the output voltage phase command of the inverter, the power supply to the load is continued without the protection stop of the inverter due to the cross current flowing between the inverter and the commercial power supply. Can be done. Further, in the invention according to claim 4, in the uninterruptible power supply according to the invention according to claim 1, when the power supply is switched after the commercial power supply is restored, the current of the inverter exceeds the predetermined value and the overcurrent occurs. An overcurrent control means for detecting that an overcurrent has occurred and a gate block means for blocking the output of a gate signal to the inverter when an overcurrent is detected by the overcurrent control means are added.

Therefore, the uninterruptible power supply according to the fourth aspect of the present invention has the same effect as the first aspect of the present invention, and also has a function of switching the power supply after the commercial power supply is restored. An overcurrent control means for detecting that the current of the inverter has exceeded a predetermined value and an overcurrent, and a gate for blocking the output of a gate signal to the inverter when the overcurrent control means detects an overcurrent. Block means to block the gate output of the inverter when the current of the inverter exceeds a predetermined value and becomes an overcurrent at the time of power supply switching after the commercial power is restored, thereby turning the inverter into the commercial power. When switching the power supply, even if a sudden phase difference or voltage difference occurs during the lap operation of the inverter and the commercial power supply by igniting the switching element of the inverter, Over motor is not stopped protected overcurrent detection, etc., performs the power supply switching without affecting the load, can be performed to continue the power supply to the load.

According to a fifth aspect of the present invention, in the uninterruptible power supply according to the first aspect of the present invention, when the power supply is switched after the commercial power supply is restored, the amplitude of the output power from the commercial power supply is reduced. Means for adjusting the output voltage amplitude command of the inverter, and overcurrent control means for detecting that the current of the inverter has exceeded a predetermined value and has become an overcurrent when the power supply is switched after the commercial power is restored. And a gate blocking means for blocking output of a gate signal to the inverter when an overcurrent is detected by the overcurrent control means.

Therefore, in the uninterruptible power supply according to the fifth aspect of the invention, the operation of the second aspect and the operation of the fourth aspect can be simultaneously achieved. This makes it possible to further improve the load power supply reliability when switching the power supply between the inverter and the commercial power supply.

Further, according to a sixth aspect of the present invention, in the uninterruptible power supply according to the first aspect,
Means for adjusting the output voltage phase command of the inverter with respect to the phase of the output power from the commercial power supply at the time of power supply switching after the commercial power supply is restored; Overcurrent control means for detecting that overcurrent has exceeded a predetermined value, and gate block means for blocking the output of a gate signal to the inverter when the overcurrent is detected by the overcurrent control means. Has been added.

Therefore, in the uninterruptible power supply according to the sixth aspect of the invention, the operation of the third aspect and the operation of the fourth aspect can be simultaneously achieved. This makes it possible to further improve the load power supply reliability when switching the power supply between the inverter and the commercial power supply.

[0065]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration example of an uninterruptible power supply according to the present embodiment. The same parts as those in FIG. The description is omitted, and only different portions are described here.

That is, in the uninterruptible power supply of the present embodiment, as shown in FIG. 1, the PLL circuit 23 in the inverter control circuit 11 in FIG. 7 is omitted, and instead, a low-speed PLL circuit 58 and A new inverter control circuit 80 is configured by adding a high-speed PLL circuit 59 and a switching circuit 60.

The low-speed PLL circuit 58 receives the output power from the commercial power supply 7 as an input, and adjusts the phase by following the input power at a predetermined speed.

The low-speed PLL circuit 58 has a configuration similar to that of the PLL circuit 23, and is designed with emphasis on stability in a steady state.

The high-speed PLL circuit 59 receives the output power from the commercial power supply 7 and adjusts the phase by following the input power at a speed higher than a predetermined speed of the low-speed PLL circuit 58.

Unlike the low-speed PLL circuit 58, the high-speed PLL circuit 59 is designed with emphasis on transient characteristics, that is, high-speed response.

As a result, the output phase of inverter 1 can be synchronized with the phase of commercial power supply 7 immediately after commercial power supply 7 is restored.

The switching circuit 60 is normally connected to the low-speed PLL circuit 5
When the power failure of the commercial power supply 7 is detected by the power failure detection circuit 20, the output from the high-speed PLL circuit 59 is switched and output as the output voltage phase reference 33.

FIG. 2 is a block diagram showing a configuration example of the high-speed PLL circuit 59 in the inverter control circuit 80 in the uninterruptible power supply according to the present embodiment.

In FIG. 2, based on an output from a three-phase to two-phase conversion circuit 62 to which a three-phase AC input voltage from the commercial power source 7 is input, and a two-phase sine wave from a sine wave generation circuit 6 described later. The PI control circuit (error amplifier) 64 removes noise and distortion of high frequency components from the phase difference Δθ calculated by the calculation circuit 63 and amplifies the error.

The output from the PI control circuit 64 is input to a voltage controlled oscillator (VCO) 65, and the output pulse frequency is controlled.

The output pulse frequency is counted by a counter 66 and output as a digital phase detection value θ, and is also input to a sine wave generation circuit 67 to be converted into a two-phase sine wave.

The two-phase sine wave is fed back to the arithmetic circuit 63.

With this configuration, the three-phase AC input voltage from the commercial power supply 7 can calculate the respective phase from the instantaneous value of each phase.

That is, the circuit of FIG. 2 is a PLL circuit using a continuous phase comparison method for immediately synchronizing the phase of the output voltage of the inverter 1 with the phase of the commercial power supply 7 when the commercial power supply 7 is restored. With this method, a high-speed response can be realized.

Next, the operation of the uninterruptible power supply according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 7 is omitted, and only the operation of the different parts will be described here.

Normally, the output from low-speed PLL circuit 58 is used as output voltage phase reference 33 as output voltage control circuit 34.
And the output voltage of the inverter 1 is controlled.

On the other hand, when the commercial power source 7 is out of power, the output from the high-speed PLL circuit 59 is given to the output voltage control circuit 34 as the output voltage phase reference 33 by the switching circuit 60, and the phase of the output voltage of the inverter 1 is changed. The low-speed PLL
The circuit 58 can be switched to the high-speed PLL circuit 59.

By switching to the high-speed PLL circuit 59, the phase of the output voltage of the inverter 1 can be immediately synchronized with the phase of the commercial power supply 7 after the commercial power supply 7 is restored.

As described above, in the uninterruptible power supply of this embodiment, the output from the low-speed PLL circuit 58 is always
When the commercial power supply 7 fails, the output voltage phase reference 33 is switched to the output from the high-speed PLL circuit 59. Therefore, it is possible to switch to the load power supply from the commercial power supply 7 immediately after the commercial power supply 7 is restored. The operation time of the inverter 1 can be reduced. As a result, the deterioration of the main circuit constituting the DC power supply and the inverter as the power storage means does not proceed due to a rise in temperature or the like.

(Second Embodiment) FIG. 3 shows an inverter control circuit 8 in an uninterruptible power supply according to the present embodiment.
FIG. 3 is a block diagram illustrating a configuration example of a reference generation circuit in 0;
The same parts as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

That is, the reference generation circuit according to the present embodiment has a configuration in which a one-shot circuit 61 and a subtractor 81 are added to FIG. 9 as shown in FIG.

The one-shot circuit 61 outputs a one-shot signal when switching power supply after the commercial power supply 7 is restored.

The subtracter 81 outputs the soft start signal 52
, The one-shot signal from the one-shot circuit 61 is reduced.

Then, the soft start signal 52 from which the one-shot signal has been reduced and the voltage reference signals 51a to 51a.
The output voltage reference 32 is obtained by multiplying the output voltage 51c by the multipliers 53a to 53c.

With this configuration, it is possible to adjust the output voltage amplitude command of inverter 1 with respect to the amplitude of the output power from commercial power supply 7 at the time of power supply switching after commercial power supply 7 is restored.

Next, the operation of the uninterruptible power supply according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 9 is omitted, and only the operation of the different parts will be described here.

When the output of the inverter 1 is switched to the commercial power supply 7 after the commercial power supply 7 is restored, the switching element of the inverter 1 is ignited and the inverter 1 and the commercial power supply 7 are lap-operated only during the lap operation. One shot circuit 61
Accordingly, the output of inverter 1 can be changed to a predetermined voltage amplitude.

If the output voltage amplitude of the inverter 1 is reduced with respect to the commercial power supply 7, the load current can be immediately transferred to the commercial power supply 7 when the power supply is switched.

As described above, the uninterruptible power supply of the present embodiment has the same effects as those of the first embodiment, that is, the load from the commercial power supply 7 immediately after the commercial power supply 7 is restored. Since the power supply can be switched, the operation time of the inverter 1 can be reduced. In addition, when the power supply is switched after the commercial power supply 7 is restored,
Inverter 1 with respect to the amplitude of output power from commercial power supply 7
Is adjusted, the power supply is switched between the inverter 1 and the commercial power supply 7.
The cross current flowing between the inverter 1 and the commercial power supply 7 makes it possible to continuously supply power to the load 6 without stopping the protection of the inverter 1.

(Third Embodiment) FIG. 4 shows an inverter control circuit 8 in an uninterruptible power supply according to the present embodiment.
FIG. 3 is a block diagram illustrating a configuration example of a reference generation circuit in 0;
The same parts as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

That is, the reference generation circuit according to the present embodiment has a configuration in which a one-shot circuit 61 and subtracters 81a, 81b, 81c are added to FIG. 9 as shown in FIG.

The one-shot circuit 61 outputs a one-shot signal when power supply is switched after the commercial power supply 7 is restored.

The subtractors 81a, 81b, 81c subtract the one-shot signal from the one-shot circuit 61 from the voltage reference signals 51a, 51b, 51c.

The voltage reference signals 51a to 51c obtained by reducing the one-shot signal and the soft start signal 5
The output voltage reference 32 is obtained by multiplying 2 by the multipliers 53a to 53c.

With this configuration, it is possible to adjust the output voltage phase command of inverter 1 with respect to the phase of the output power from commercial power supply 7 at the time of power supply switching after commercial power supply 7 is restored.

Next, the operation of the uninterruptible power supply according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 9 is omitted, and only the operation of the different parts will be described here.

When the output of the inverter 1 is switched to the commercial power supply 7 after the power supply of the commercial power supply 7 is restored, the switching element of the inverter 1 is ignited and the inverter 1 and the commercial power supply 7 are lap-operated only during the lap operation. One shot circuit 61
Thus, a predetermined voltage phase difference can be given to the output of inverter 1.

If the output voltage phase of the inverter 1 is delayed with respect to the commercial power supply 7, the load current can be immediately transferred to the commercial power supply 7 when the power supply is switched.

As described above, the uninterruptible power supply of this embodiment has the same effects as those of the first embodiment, that is, the load from the commercial power supply 7 immediately after the commercial power supply 7 is restored. Since the power supply can be switched, the operation time of the inverter 1 can be reduced. In addition, when the power supply is switched after the commercial power supply 7 is restored,
Inverter 1 with respect to the amplitude of output power from commercial power supply 7
Is adjusted, the power supply between the inverter 1 and the commercial power supply 7 is switched.
The cross current flowing between the inverter 1 and the commercial power supply 7 makes it possible to continuously supply power to the load 6 without stopping the protection of the inverter 1.

(Fourth Embodiment) FIG. 5 is a block diagram showing a configuration example of an uninterruptible power supply according to the present embodiment. The same parts as those in FIG. The description is omitted, and only different portions are described here.

That is, as shown in FIG. 5, the uninterruptible power supply according to the present embodiment is obtained by adding a current detector 69 and an overcurrent detection circuit 70 to the inverter control circuit 80 shown in FIG. A new inverter control circuit 90 is configured.

The current detector 69 detects the output current of the inverter 1.

The overcurrent detection circuit 70 detects that the current of the inverter 1 detected by the current detector 69 exceeds the predetermined value and becomes an overcurrent when the power supply is switched after the commercial power supply 7 is restored. An output is generated upon detection of the event.

FIG. 6 is a block diagram showing a configuration example of gate control circuit 24 'in inverter control circuit 90 in the uninterruptible power supply according to the present embodiment, and the same parts as those in FIG. The description thereof will be omitted, and only different portions will be described here.

That is, as shown in FIG. 6, the gate control circuit 24 'of this embodiment is provided with changeover switches 68a to 68g as gate block means on the output side of the gate signal output circuits 57a, 57b, 57c in FIG. 68c is added.

The changeover switches 68a to 68c normally output the output signals from the gate signal output circuits 57a, 57b and 57c as they are to the inverter 1 as the gate signal 35, and receive the overcurrent detection circuit 70 which is input as a changeover signal.
Is switched to block the output of the gate signal 35 to the inverter 1 in accordance with the output from the inverter 1.

Next, the operation of the uninterruptible power supply according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIGS. 1 and 11 is omitted, and only the operation of the different parts will be described here.

The output current of the inverter 1 is detected by the current detector 69 and input to the overcurrent detection circuit 70.

The overcurrent detection circuit 70 detects that the current of the inverter 1 detected by the current detector 69 has exceeded a predetermined value and has become an overcurrent when the power supply is switched after the commercial power supply 7 is restored. Then, the output is the gate control circuit 2
4 'is input as a switching signal.

On the other hand, in the gate control circuit 24 ', when a switching signal is input from the overcurrent detection circuit 70, the switching signals 68a to 68c are switched by this switching signal, and
The output of the gate signal 35 to the inverter 1 from the gate signal output circuits 57a, 57b, 57c is blocked.

In this way, the gate of the inverter 1 can be controlled according to the result of the overcurrent determination in the overcurrent detection circuit 70.

As described above, the uninterruptible power supply of the present embodiment has the same effects as those of the first embodiment, that is, the load from the commercial power supply 7 immediately after the commercial power supply 7 is restored. Since the power supply can be switched, the operation time of the inverter 1 can be reduced. In addition, when the power supply is switched after the commercial power supply 7 is restored,
Since the gate output of the inverter 1 is blocked when the current of the inverter 1 exceeds a predetermined value and becomes an overcurrent, when the power supply of the inverter 1 is switched to the commercial power supply 7, the switching element of the inverter 1 is turned on. Even if a sudden phase difference or voltage difference occurs during the lap operation of the inverter 1 and the commercial power supply 7 due to arcing, the inverter 1 does not stop protection due to overcurrent detection or the like, and does not affect the load 6. By performing power supply switching, power supply to the load 6 can be continued.

(Other Embodiments) (a) Power recovery of the commercial power supply 7 by combining the above-described first and second embodiments with the above-described fourth embodiment Since it is possible to immediately switch to the load power supply from the commercial power supply 7 later, the operation time of the inverter 1 can be reduced, and
When the power is switched between the inverter 1 and the commercial power source 7, the cross current flowing between the inverter 1 and the commercial power source 7 makes it possible to continuously supply power to the load 6 without stopping the protection of the inverter 1. Further, when the power supply of the inverter 1 is switched to the commercial power source 7, even if a phase difference or a voltage difference occurs suddenly during the lap operation of the inverter 1 and the commercial power source 7 by igniting the switching element of the inverter 1, the inverter 1 Does not stop protection due to overcurrent detection or the like, switches power supply without affecting the load 6, and can continue power supply to the load 6.

As a result, it is possible to further improve the load power supply reliability when switching the power supply between the inverter 1 and the commercial power supply 7.

(B) By combining the above-described first and third embodiments with the above-described fourth embodiment, the commercial power supply 7 can be used immediately after the commercial power supply 7 is restored.
, The operation time of the inverter 1 can be reduced, and when the power supply is switched between the inverter 1 and the commercial power supply 7,
The cross current flowing between the inverter 1 and the commercial power supply 7 makes it possible to continuously supply power to the load 6 without stopping the protection of the inverter 1. Even if a phase difference or a voltage difference occurs suddenly during the lap operation of the inverter 1 and the commercial power supply 7 by igniting the switching element of the inverter 1, the protection of the inverter 1 is not stopped by overcurrent detection or the like, and the load is not stopped. The power supply is switched without affecting the load 6, and the power supply to the load 6 can be continued.

As a result, it is possible to further improve the load power supply reliability at the time of switching the power supply between the inverter 1 and the commercial power supply 7.

(C) In the first to fourth embodiments, the low-speed PLL circuit 58 and the high-speed PLL circuit 5
As 9, the case where the phase is adjusted by following the output power from the commercial power supply 7 at a predetermined speed has been described. However, the process is not limited to the speed but may be simply handled by time.

[0128]

As described above, according to the uninterruptible power supply of the present invention, it is possible to reduce the operation time of the inverter by immediately switching to the load power supply from the commercial power supply after the commercial power supply is restored. . As a result, the deterioration of the main circuit constituting the DC power supply and the inverter as the power storage means does not proceed due to a rise in temperature or the like.

Further, when the inverter is switched to the commercial power supply, even if a phase difference or a voltage difference occurs suddenly during a period in which the switching element of the inverter is ignited and the inverter and the commercial power supply are lap-operated, the inverter is not operated. The power supply is switched without affecting the load without stopping the protection due to the current detection or the like, and the power supply to the load can be continuously performed.

Furthermore, when the power supply is switched between the inverter and the commercial power supply, the power supply to the load can be continued without the protection stop of the inverter due to the cross current flowing between the inverter and the commercial power supply. It is possible to improve the load feeding reliability of the device.

As described above, the load power supply reliability at the time of switching the power supply between the inverter and the commercial power supply can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an uninterruptible power supply according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a high-speed PLL circuit in an inverter control circuit in the uninterruptible power supply according to the first embodiment.

FIG. 3 is a block diagram showing a configuration example of a reference generation circuit in an inverter control circuit in an uninterruptible power supply according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration example of a reference generation circuit in an inverter control circuit in an uninterruptible power supply according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a fourth embodiment of the uninterruptible power supply according to the present invention.

FIG. 6 is a block diagram showing a configuration example of a gate control circuit in an inverter control circuit in the uninterruptible power supply according to the fourth embodiment.

FIG. 7 is a block diagram showing a configuration example of a conventional uninterruptible power supply.

FIG. 8 is a circuit diagram showing a configuration example of an inverter in a conventional uninterruptible power supply.

FIG. 9 is a block diagram showing a configuration example of a reference generation circuit in an inverter control circuit in a conventional uninterruptible power supply.

FIG. 10 is a block diagram showing a configuration example of an output voltage control circuit in an inverter control circuit in a conventional uninterruptible power supply.

FIG. 11 is a block diagram showing a configuration example of a gate control circuit in an inverter control circuit in a conventional uninterruptible power supply.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inverter 2 ... Inverter transformer 3 ... Switching circuit 4 ... Contactor 5 ... Semiconductor switch 6 ... Load 7 ... Commercial power supply 8 ... Voltage detector 9 ... DC power supply 11 ... Inverter control circuit 20 ... Power failure detection circuit 21 ... Reference generation circuit 22 ... Output voltage control circuit 24 ... Gate control circuit 24 '... Gate control circuit 31 ... Output voltage feedback 32 ... Output voltage reference 33 ... Output voltage phase reference 34 ... Output voltage command 35 ... Gate signal 36 ... Inverter output voltage 41 ... DC Capacitor 42 Switching element 43 Gate drive circuit 51 Voltage reference signal 52 Soft start signal 53a Multiplier 53b Multiplier 53c Multiplier 54a PI control circuit 54b PI control circuit 54c PI control circuit 55 Carrier Generation circuit 56a: comparator 56b: comparator 56 ... Comparator 57a ... Gate signal output circuit 57b ... Gate signal output circuit 57c ... Gate signal output circuit 58 ... Low-speed PLL circuit 59 ... High-speed PLL circuit 60 ... Switching circuit 61 ... One-shot circuit 62 ... Three-phase to two-phase conversion circuit 63 ... Arithmetic circuit 64 PI control circuit 65 Voltage control transmitter (VCO) 66 Counter 67 Sine wave generation circuit 68a Changeover switch 68b Changeover switch 68c Changeover switch 69 Current detector 70 Overcurrent limiting circuit 80 Inverter control circuit 81: subtractor 81a: subtractor. 81b: Subtractor 81c: Subtractor 90: Inverter control circuit.

Claims (6)

[Claims] An inverter, comprising a plurality of switching elements, for converting DC power into AC power and outputting the same, and a commercial power supply for outputting commercial power, and always supplying output power from the commercial power to a load. An uninterruptible power supply that switches power supply so as to supply the output power from the inverter to the load when the commercial power supply fails, wherein the output power from the commercial power supply is input and the power failure of the commercial power supply is detected. Power failure detection means, which operates when a power failure of the commercial power supply is detected by the power failure detection means, and a reference generation means for outputting an output voltage reference; and inputting output power from the commercial power supply, A low-speed phase synchronizing means for adjusting the phase by following at a predetermined speed, inputting the output power from the commercial power supply, and applying the predetermined speed to the input power. A high-speed phase synchronizing means for adjusting the phase by following at a higher speed, always outputting the output from the low-speed phase synchronizing means, and outputting the output from the high-speed phase synchronizing means when a power failure of the commercial power supply is detected by the power failure detecting means. Switching means for switching and outputting the output of the inverter as an output voltage phase reference, the inverter based on an output voltage of the inverter, an output voltage reference from the reference generation means, and an output voltage phase reference from the switching means. Output voltage control means for generating and outputting an output voltage command of the inverter so that the output voltage of the inverter matches the output voltage reference; and generating a gate signal based on the output voltage command from the output voltage control means; And a gate control means for controlling a gate of the switching element constituting the uninterruptible power supply. 2. The uninterruptible power supply according to claim 1, wherein at the time of power supply switching after the commercial power supply is restored, an output voltage amplitude command of the inverter with respect to an amplitude of output power from the commercial power supply. An uninterruptible power supply characterized by adding means for adjusting the power. 3. The uninterruptible power supply according to claim 1, wherein at the time of power supply switching after the commercial power supply is restored, an output voltage phase command of the inverter with respect to a phase of output power from the commercial power supply. An uninterruptible power supply characterized by adding means for adjusting the power. 4. The uninterruptible power supply according to claim 1, wherein when the power supply is switched after the commercial power is restored, it is detected that the current of the inverter has exceeded a predetermined value and has become an overcurrent. An uninterruptible power supply device, further comprising: an overcurrent control unit that performs an operation, and a gate block unit that blocks output of a gate signal to the inverter when an overcurrent is detected by the overcurrent control unit. 5. The uninterruptible power supply according to claim 1, wherein at the time of power supply switching after the commercial power supply is restored, the output voltage amplitude command of the inverter with respect to the amplitude of the output power from the commercial power supply. An overcurrent control unit that detects that the current of the inverter has exceeded a predetermined value and has become an overcurrent when the power supply is switched after the commercial power supply is restored, and the overcurrent control unit. And an uninterruptible power supply characterized by adding gate block means for blocking the output of a gate signal to the inverter when an overcurrent is detected by (1). 6. The uninterruptible power supply according to claim 1, wherein at the time of power supply switching after the commercial power supply is restored, an output voltage phase command of the inverter with respect to a phase of output power from the commercial power supply. An overcurrent control unit that detects that the current of the inverter has exceeded a predetermined value and has become an overcurrent when the power supply is switched after the commercial power supply is restored, and the overcurrent control unit. And an uninterruptible power supply characterized by adding gate block means for blocking the output of a gate signal to the inverter when an overcurrent is detected by (1).