JP2003244868A - Uninterruptible power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable charging via an inverter in steady-state operation, and enable controlling so that a commercial power source side forms a sine wave with high power factor, by imparting active filter function to the inverter in steady operation, further prevent occurrences of failures of switching elements due to on-offs of the commercial power switches with respect to the generation of overcurrent on the load side. <P>SOLUTION: In an uninterruptible power supply which continuously feeds commercial power source, a control means computes electric power of the inverter to obtain differential current from an input AC source, and controls the switches of the inverter so that input side has high power factor in steady operation. If an abnormality occurs in the input AC source, the control means turns the input power side switches off at a high speed, feeds the AC source from the inverter, and instantaneously causes the input power switches to be turned on, when the input AC source recovers to normal operation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply device of constant commercial power supply type. The present invention particularly relates to an uninterruptible power supply device that can switch from commercial power supply to inverter power supply without interruption and realizes high power factor power.

This uninterruptible power supply system can also be used as a device for supplying the AC power converted from the inverter to the commercial power supply side when the DC power supply of the inverter is a generator.

[0003]

2. Description of the Related Art Conventionally, as an uninterruptible power supply device used for office equipment such as a computer, a constant inverter power supply type uninterruptible power supply device has been used.

FIG. 8 shows an example of the configuration of the constant inverter power supply type uninterruptible power supply device. In the steady state, this constant inverter power supply type uninterruptible power supply device converts a commercial power supply into a direct current by an AC / DC converter 81, converts it into an alternating current by a DC / AC inverter 82, and outputs an alternating current through a filter 83. When the input commercial power supply is abnormal, the DC power supply of the battery BA is turned on by the DC / AC inverter 8
When the inverter is out of order, it is converted into alternating current at 2 and supplied to the load, and in the case where the inverter fails, it is switched to a commercial power source and supplied to the load.

One of the reasons why such an always-inverter-powered uninterruptible power supply is used is that it is difficult and reliable to switch from commercial power to inverter power without interruption. . For example, if a thyristor is used as an inverter and a switching element for switching commercial power supply, a half AC cycle delay is required to turn off the switch. I couldn't switch. This is one of the reasons for hesitating to adopt the continuous commercial power supply type uninterruptible power supply as a power supply for office equipment such as computers that need to take protective measures against instantaneous power failure. It was

[0006]

However, in the above-mentioned constant inverter power feeding system, it is necessary to once convert the commercial power source into the direct current by the AC / DC converter and then convert it into the alternating current by the inverter again. There is a problem that efficiency is worse than that of the system, and the device is large and expensive.

An object of the present invention is to provide an uninterruptible power supply device of a constant commercial power supply type which is capable of instantaneously switching from a commercial power supply to an inverter by using a high-speed switching element and which is power efficient.

Another object of the present invention is to operate the inverter as an active filter so that, during steady operation, the commercial power supply current is increased even if the load current is a power factor or waveform of various currents depending on the type of load. It is to provide an uninterruptible power supply device that uses a sine wave with a power factor.

Another object of the present invention is to supply commercial power because the input voltage crosses zero when switching to inverter power supply after switching to inverter power supply by detecting an abnormality in the input commercial power supply using a high-speed switch element. An object of the present invention is to provide an uninterruptible power supply device that can be controlled so that a surge current or the like does not occur by being restored.

Another object of the present invention is to rapidly turn off the commercial power source side switch when an overcurrent occurs in the output current and the power supply to the inverter and the commercial power source is stopped to control the output current droop. An object of the present invention is to provide an uninterruptible power supply capable of protecting a switch element by absorbing a surge current generated in a reactor existing on the output side.

[0011]

SUMMARY OF THE INVENTION An aspect of the present invention relates to an uninterruptible power supply device of a constant commercial power supply type capable of soft-starting normal operation recovery, and an AC switch (S) to which an AC power supply is connected. _1, S ₂₎ and the first power supply; and a second power supply device including an inverter DC power source is connected, the input voltage detecting means for detecting an input ac voltage, the second when the AC power supply to detect a stop In the uninterruptible power supply device including a control unit that operates a power supply device, the control unit stops the first power supply device when the input voltage detection unit detects an abnormality of the AC power supply, and the second power supply device. Means for switching to voltage mode control for providing an output AC voltage corresponding to the reference sine wave, and when the abnormality of the AC power supply is recovered, the second power supply device is operated as an active filter. Characterized by comprising a means for switching the flow mode control. The switching to the current mode control may be performed when the input voltage detected by the input voltage detecting means becomes zero in each cycle of AC.

Further, the present invention is an invention relating to an uninterruptible power supply unit for continuous commercial power supply, which makes an inverter function as an active filter and enables high power factor operation, and is an AC switch (S) to which an AC power supply is connected. _1, S ₂₎ and the first power supply; and a second power supply device including an inverter DC power source is connected, an uninterruptible power supply with a control unit wherein the AC power source to operate the second power supply is stopped In the device, a first current detection means for detecting the output current of the first power supply device, and a second current detection means for detecting the output current of the second power supply device, the control unit, the second current A means for obtaining the output power of the inverter based on the output of the detecting means, and a means for generating a sine wave reference current based on the output power, and the obtained reference current and the first current detecting means during steady operation. The differential current between the AC power source output current so that the AC output current issued matches can comprise a means for controlling so that the inverter provides.

It is preferable that the means for generating the reference current includes means for controlling the level of the reference sine wave so that the output power of the inverter gives the charging current to the battery as the DC power supply.

The present invention also relates to a structure for protecting the AC switch from surge current, in which a capacitor (C) is provided on the load side of the first AC switch to which the AC power supply terminal is connected.
₂ ) is the second AC switch (S ₃ , S) between the output side lines.
₄ ), the second AC switch can be ON / OFF controlled in a phase opposite to that of the first AC switch.

When the output current of the inverter exceeds a predetermined level and an overcurrent occurs, a means for turning off all or some of the switching elements of the inverter to stop the operation, and an output current of the AC power supply have a predetermined value. It is preferable to include means for turning off the first AC switch and turning on the second AC switch when an overcurrent exceeding the level is detected.

[0016]

First, the power is supplied from the AC power supply during steady operation. Here, the inverter is made to function as an active filter, and the current mode control of the inverter is performed so that the AC power supply current becomes a sine wave and the power factor is increased. . This is a mode in which a sinusoidal reference current is generated based on the output power of the inverter, and the inverter is controlled to supply the difference between the reference current and the AC power supply output current. The sine wave reference current is generated by calculating the average power of the inverter from the output voltage and the output current of the inverter, and controlling the level of the reference sine wave based on the average power of the inverter. At this time, if the power of the inverter is controlled to be always 0 (only the loss of the inverter), the inverter can set the input AC power factor of the AC power supply to 1 without consuming extra power. it can. Further, if the power consumption of the inverter is controlled to be on the negative side, energy can be stored on the DC side of the inverter, so that the battery as the DC power source can be charged as it is.

When an abnormality occurs in the input AC power supply, the abnormality is detected, and the switch is instantly switched to the inverter side to perform the voltage mode control for feeding the inverter. At this time, the switch on the commercial power source side is turned off, and when the input AC power source is restored, control is performed so that the AC power source side supplies power when the input AC voltage crosses zero on the AC cycle. As a result, the AC power supply can be soft-started and no surge current or the like is generated.

When an overcurrent is detected and a predetermined threshold value is exceeded, all or part of the inverter and the switching elements on the AC power supply side are turned off, and the drooping control for drooping the output current is performed. At this time, a surge absorbing capacitor is provided on the load side of the AC power supply side switch, and when turning off the switch connecting the AC power supply input terminal and the load,
The switch for connecting the surge absorbing capacitor is turned on to operate so as to absorb the surge voltage generated by the reactor of the output side AC filter.

[0019]

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

FIG. 1 is a diagram for explaining an outline of a connection form of an uninterruptible power supply according to an embodiment of the present invention, and FIG. 2 is a diagram showing an outline of a configuration of a control unit of this uninterruptible power supply.

In FIG. 1, an uninterruptible power supply system according to this embodiment has an AC switch section (ACSW) 1 for constantly supplying commercial power to a load, and an inverter section (I) equipped with a battery.
NVSW) 2 and a filter unit (FIL) 3 that functions as an AC filter.

The AC switch unit 1 is provided with switches S ₁ and S ₂ as switches for controlling the supply of commercial power to the load, and surges are provided on the load side of the switches S ₁ and S _2. The current absorbing capacitor C is a switch S
_3, through S ₄ is connected between the load-side output line.
The inverter unit 2 converts the power supply of the battery BA into an alternating current and supplies it to the load by the switches S ₅ , S ₆ , S ₇ , and S ₈ . The filter unit 3 is composed of the AC switch unit 1, the reactors LS ₁ and LS ₂ provided on the load side of the inverter unit 2, and a capacitor C. The uninterruptible power supply is provided with a current detector CT ₁ for detecting the output current I _C of the commercial power supply and a current detector CT ₂ for detecting the output current I _{I of the} inverter, and the input of the commercial power supply. The voltage V _C and the output voltage V _O of this uninterruptible power supply are detected.

The configuration of the control unit of the uninterruptible power supply will be described with reference to FIG.

The control section is provided with a reference sine wave generating circuit for generating a reference sine wave in synchronization with the input commercial power source, and performs various controls based on the generated reference sine wave. This control unit is roughly divided from the operation control mode into a current mode control unit that controls the output by using the inverter as an active filter during steady operation, and a voltage that controls the inverter and the AC switch unit when a commercial power supply abnormality occurs. It is divided into a mode control unit and an overcurrent control unit that controls the overcurrent of the inverter and the AC switch unit when an overcurrent occurs.

First, the current mode control unit corresponds to the inverter power calculation unit 10 to which the inverter output current I _I and the output voltage V _O are input, and the output of the inverter power calculation unit 10 and the reference sine wave. The reference current calculation unit 11 that calculates the reference current value by performing the level control of the reference sine wave that is generated, and the difference output between the input commercial power supply output current I _C and this reference current value are used to obtain the current mode control signal ( And a comparison unit 12 that outputs a current mode AVR). Here, the inverter power calculation unit 10 uses the inverter output current I
A power calculation unit 101 that calculates the power of the inverter from _I and the output voltage V _O , an averaging circuit 102 that averages the output power of the inverter, and a charging reference from a separately provided charging control circuit for the battery BA are compared. Then, the comparison unit 103 that outputs the power consumption value of the inverter is included.

The voltage mode control unit corresponds to a voltage mode control signal (voltage mode AV that controls the output voltage of the inverter by comparing the output voltage V _O with the reference sine wave).
The comparison unit 13 that generates R) corresponds to this.

The current mode control signal and the voltage mode control signal
The signal is the input commercial power supply voltage V_C Comparison to detect abnormalities
The changeover switch 1
The switch S of the inverter unit is switched by 5_Five 
~ S₈ Based on the output of the triangular wave generating circuit 17 which is a carrier wave
The pulse width modulation signal is transmitted through the PWM logic circuit 16
Given. Also, the mode switching signal is the AC switch
1 switch S₁ ~ S _Four ACSW that outputs the switching signal of
Input to the switching logic circuit 18, abnormal input power supply
If S occurs, switch S₁ ~ S_Four Output switching signal
To do.

The overcurrent control unit corresponds to the overcurrent detection which detects whether the output current I _{I of the} inverter exceeds a predetermined threshold value and outputs an inverter drooping signal when the output current I _I exceeds the threshold value. It corresponds to the unit 19 and the overcurrent detection unit 20 which detects whether the commercial power supply output current I _C exceeds a predetermined threshold value and outputs an ACSW droop signal when it exceeds the threshold value. The inverter droop signal is the PWM logic circuit 1
Is inputted to 6, turns off the switch S ₅ to S _8. In addition, the ACSW droop signal is the switch S ₁ of the AC switch unit _1.
Is input to the ACSW switching logic circuit 18 for outputting a switching signal to S ₄ and outputs a switching signal of the switch S ₁ to S _4.

The configuration of the uninterruptible power supply of this embodiment will be described more specifically with reference to FIGS. 3 and 4.

As shown in FIG. 3, the commercial power supply side terminal is not connected.
Power commercial power supply voltage V_C A terminal for detecting is provided.
Then, connect the AC switch to the commercial power supply side.
SA C ₁ Are connected. Switch element of AC switch
The child is an IGBT (Insulated Gate Bipolar Transistor)
This is the IGBTQ₁ , Q₂ With commercial power
Controls on / off with the load. Also this IGBTQ
₁ , Q₂ IGBTQ on the load side of₃ , Q_Four Through
Capacitor C₂ And resistance R₁ Connected in parallel circuit
It In addition, IGBTQ₁ Reactor L on the output line on the side
₁ Is provided, IGBTQ₂ Side commercial power supply
Force current I_C Current detector CT for detecting₁Is provided
It Furthermore, a capacitor C is provided on the load side.₃ Is connected
It

The output of the inverter is connected to the connection point of the capacitor C ₃ , and the inverter uses IGBTs Q _{5 to} Q ₈ as its switching elements.
A battery B is connected to BTQ _{5 to} Q ₈ via a capacitor C _5.
A is connected. Also, the IG of this switching unit
The reactor L ₂ is connected to the IG on the output line on the BTQ ₅ and Q ₇ side.
A current detector CT ₂ for detecting the inverter output current I _I is provided on the output lines of BTQ ₆ and Q ₈ .

FIG. 4 shows the structure of the control section. This control section is basically composed of an ACSW control section, an inverter common section, a current mode section, and a voltage mode section. The configuration is substantially the same as that of the control unit shown in FIG. 2, and the configuration is realized by an analog circuit.

First, a common sine wave generating circuit 30 for generating an AC standard sine wave for various controls is provided in the common part of the inverters. This standard sine wave generating circuit 30 is commercialized by a phase synchronization circuit 31. It is controlled to synchronize with the power supply frequency. The reference sine wave generation circuit 30 uses a ROM that stores a reference sine wave waveform, and the phase synchronization circuit 31 reads it in synchronization with the commercial power supply frequency to generate a reference sine wave. In addition, the inverter common unit includes a changeover switch 1 that switches between a current mode control signal and a voltage mode control signal.
5 and the input of this changeover switch 15 to the triangular wave generation circuit 1
PWM logic circuit 1 which modulates the carrier wave generated by 7 to generate a pulse width modulation signal and supplies it to IGBTs Q _{5 to} Q _8.
6 is provided. The circuit configurations of the triangular wave generation circuit 17 and the PWM logic circuit 16 are the same as the PWM control of the conventional inverter. Further, as the reference sine wave generation circuit 30 and the phase synchronization circuit 31, circuits similar to the conventional one can be used.

The current mode unit multiplies the output voltage V _O by the inverter output current I _I to generate an inverter power value, the average value circuit 34 for averaging the output of the multiplier 33, A comparison circuit 35 that compares the output of the average value circuit 34 and the charging reference signal, a multiplier 36 that multiplies the output of the comparison circuit 35 and a reference sine wave, and an output of the multiplier 36 and a commercial output that is input. And a comparison circuit 37 that compares the current I _C and outputs a current mode control signal to the changeover switch 15. Further, as a unit corresponding to the overcurrent detection unit 19, there is provided a comparison circuit 41 which compares the commercial output current I _C with the droop level and outputs a CS droop signal when the droop level is exceeded. Further, as a unit corresponding to the comparison / determination unit 14 for switching between the current mode control and the voltage mode control, the comparison circuit 3 that compares the reference sine wave with the input commercial power supply voltage V _C to detect an input voltage abnormality at high speed.
9 and an HL determination circuit 40 that determines whether the output of the comparison circuit is high or low and outputs a mode switching signal.

The voltage mode section compares the reference sine wave with the output voltage V _O and outputs a voltage control signal to the changeover switch 15, and compares the inverter output current I _I with the droop level. A comparator circuit 42 is provided which outputs an inverter droop signal when the inverter output current I _I exceeds the droop level.

Further, the ACSW unit is a switching logic circuit 18
Comprising a, performs on-off control of IGBTQ ₁ ~Q ₄ by the input commercial power supply voltage abnormality and overcurrent detection.

Next, the operation of this embodiment will be described with reference to the operation waveform charts of FIGS.

First, the control operation in the current mode in the steady state will be described with reference to FIG. FIG. 5 shows a waveform diagram at the time of steady operation. In FIG. 5, (a) to (d) are waveforms during the power control of the inverter, and (e) to (g) are after the power control of the inverter. The waveform of the steady state of is shown.

First, in the steady state, the IGBTs Q ₁ and Q ₂
Is on and commercial power is being supplied to the load.
In the current mode control in such a state, the output current has various current power factors and waveforms from the load impedance, but by operating the inverter as an active filter, the input AC current is always sinusoidal in each cycle of the AC waveform. It is a wave and is controlled so that the input power factor is always 1.

For example, depending on the load impedance (b)
The waveform of the load current is as shown in b.
The input voltage is the solid line a in (a), and the current waveform during control is
It is assumed that the waveform is the dotted line c in (b). Early in control
Is the output current I of the inverter_I Is 0 and the load current is
IGBTQ₁ , Q₂ Current that passes through the current detector
CT ₁ Current I detected by_C Is the same as.

The power of the inverter is obtained by multiplying the output voltage V _O by the inverter output current detected by the current detector CT ₂ by the multiplier 33. The inverter output current is a bc waveform d obtained by subtracting the commercial power supply current from the load current as shown in (c), and is multiplied by the output sine wave voltage (voltage waveform equal to the input sine wave voltage) a. The waveform of e is obtained. The obtained inverter power is averaged by the average value circuit 34 to obtain the average power of the inverter.
In this embodiment, basically, the control is performed so that the average power of the inverter is always 0.

The average value of the inverter power and the reference sine wave output are multiplied by the multiplier 36 to obtain the sine wave reference current value, and the sine wave reference current value and the commercial power supply output current I _C are obtained. The comparison circuit 37 compares and outputs the current mode control signal so that the difference current is supplied by the inverter. With this current mode control signal, the PWM logic circuit 16 sends the PWM signal to the IGBTs Q _{5 to} Q of the inverter.
Give to _eight . By this current mode control, the commercial power supply output current I _C has a sinusoidal waveform as seen in the cs current of (d) waveform c ′, so the power of this power supply device can have a power factor of 1. . This means that the inverter operates as an active filter without storing or releasing extra power.

Since there is actually a loss due to the inverter circuit, the inverter power goes to the minus side accordingly. Further, when the inverter power is further increased to the negative side, the energy on the DC side of the inverter is accumulated, so that the battery BA can be charged. Therefore, the comparison circuit 35 compares the average power of the inverter with the charging reference value of the battery BA, and the battery BA is charged to the negative side by the amount not exceeding the charging reference value. The charging reference is given when the charging state of the battery is monitored by a battery monitoring circuit which is separately provided and charging is required according to the charging state.

As described above, in the steady operation, by controlling the inverter in the current mode, the power supply device can be used as a high power factor device, and the battery can be charged by the inverter. .

Next, the voltage mode control operation when an abnormality occurs in the input commercial power supply will be described with reference to FIG.

For example, assume that a waveform abnormality as shown by a occurs in the input voltage waveform of FIG. Input voltage V _C
Is compared with the reference sine wave by the comparison circuit 39,
The comparison result is judged by the HL judging circuit 40, and the abnormality of the input waveform is judged. The output of the HL determination circuit 40 has a waveform represented by f in FIG.

The operation at this time is basically the same as the conventional inverter.
It is the same as the power supply of the data, IGBTQ ₁ , Q₂ Turn off
So that the output voltage waveform becomes a sine wave waveform.
V_O And the reference sine wave are compared by the comparison circuit 38, and the difference
The inverter AVR signal causes the inverter IG
BTQ_Five ~ Q₈ Is PWM controlled.

Here, the feature of this embodiment lies in the switching from the current mode control to the voltage mode control due to an abnormal input voltage. That is, in this embodiment, the conversion to the voltage mode is instantaneous (IG
BT switching delay and input voltage detection delay, but very short), the inverter is switched to, and the inverter instantaneously performs the operation of the sinusoidal voltage output that continues from before that. Another feature of this embodiment resides in switching from voltage mode control to current mode control by restoration of the input voltage. That is, the control unit detects the input voltage V _c and controls the switching timing so as to be performed at the zero cross point of the input voltage V _C. As a result, the IGBTs Q ₁ and Q ₂ are turned on to shift the control mode of the inverter to the current mode control. Therefore, the portion indicated by the diagonal line G in FIG. 6 (e) is fed from the inverter. By controlling in this way, when the input voltage of the commercial power supply is zero, the IGBTQ
_{Since 1} and Q ₂ are turned on, a sudden inrush current does not occur on the load side.

Next, the drooping control operation when an overcurrent occurs will be described with reference to FIG.

Generally, when an overcurrent occurs in the load current, in order to prevent damage to the switching elements of the inverter and the AC switch, all the switching elements are turned off to reduce the output current, and the current value becomes a constant level. The drooping control is performed.

First, the drooping control of the inverter will be described.

The inverter output current I _I is input to the comparison circuit 42 having a hysteresis characteristic, and when the upper limit exceeds the droop level, the output of the comparison circuit 42 is inverted and an inverter droop signal for stopping the operation of the inverter is output. . This stops the operation of the inverter, and the inverter output current I _I gradually decreases due to the influence of the reactor of the AC filter. When the lower limit of the hysteresis of the comparison circuit 42 is reached, the output of the comparison circuit 42 is inverted and the inverter is restarted. As a result, the inverter current I _I is in a constant level drooping state.

Next, the drooping control of the AC switch section will be described. The droop control of this AC switch is basically the same as the inverter control, and when the commercial power supply current I _C exceeds the droop level, the droop signal is output by the comparison circuit 41 having the same function as the comparison circuit 42. IGBT Q ₁ , Q ₂
Is controlled on and off.

Here, the feature of this embodiment is that the series circuit of the capacitor C ₂ and the IGBTs Q ₃ and Q ₄ provided on the load side of the IGBTs Q ₁ and Q ₂ and the commercial power source side are provided. The point is that the capacitor C ₁ is provided.

IGBTQ for switching commercial power supply
Considering the lines of ₁ and Q _2, the power supply inductance is on the input side of the commercial power supply and the reactor L _{1 of the} AC filter is on the output side. At this time, if the switch of the commercial power supply is suddenly turned off, a large surge voltage due to the inductance is generated across the switch. Accordingly rapidly consuming large surge voltage to IGBTQ _1, Q _2, which may IGBTQ _1, Q ₂ may be damaged.

Therefore, in the present embodiment, the capacitor C ₁ absorbs the surge voltage due to the power supply inductance when the IGBTs Q ₁ and Q ₂ are off. In addition, IGBTs Q ₁ , Q ₂
When turned off, a control signal opposite in phase to the control signal given to the IGBTs Q ₁ and Q ₂ is given to the IGBTs Q ₃ and Q ₄ to turn them on, and the surge voltage generated by the reactor L _{1 is} absorbed by the capacitor C ₂ . The capacity of the capacitor C ₂ is determined by the inductance of the reactor L ₁ , but the capacity may be small.

From the voltage mode control described above, the current mode is changed.
In the case of transition to control mode, zero cross control is performed,
IGBTQ₁ , Q₂ Since there is no potential difference between both terminals of
IGBTQ₃ , Q_Four No need for reverse phase switching due to
is there. However, in the case of droop control due to overcurrent, the IGBT
Q₁ , Q₂ Switching is controlled on / off at any time
Therefore, the IGBTQ₁ , Q₂ There is a potential difference between the terminals
It Therefore, if the IGBTQ₃ , Q_Four Reverse-phase Sui
IGBTQ without touching₁ , Q₂ When turned on,
Indexer C₁ , C₂ Inrush current to the
IGBTQ₁ , Q ₂ May be damaged. others
Therefore, IGBTQ₃ , Q_Four Is installed, and IGBTQ ₁ , Q₂ of
When the IGBTQ turns on₃ , Q_Four Turn off the conden
SA C₂ The IGBTQ₁ , Q₂ To separate from the line
is doing. The resistance R₁ Is the capacitor C₂ For discharge of
Then used.

Although the control unit shown in FIG. 4 is constructed by an analog circuit, it goes without saying that it can be constructed by a digital circuit.

Further, although the above embodiment has been described by way of the example of the single-phase power supply, it is obvious that it can be realized by an uninterruptible power supply system of a three-phase AC power supply. Further, in the above-described embodiment, the AC switch section 1 is provided with the switches S ₁ and S ₂ for each line to open and close each line, but it is also possible to provide an AC switch only on one line. The invention can be realized.

Further, when a fuel cell device or a solar cell provided for each business place is used as a direct current power source instead of the battery BA of the above-mentioned embodiment, power can be constantly fed by an inverter, When there is an electromotive force larger than the power consumption of the load, it is possible to supply (sell) power to the commercial power supply side in the inverter power supply mode.

[0061]

As described above, the present invention has the following effects. By using an IGBT capable of high-speed switching as a switch element, it is possible to provide an uninterruptible power supply device that can perform instantaneous waveform control and consumes less power, which is always commercial power supply. By controlling the output current of the inverter so that it functions as an active filter, it is possible to provide an uninterruptible power supply capable of converting an alternating current into a sine wave and realizing a high power factor. By controlling the power of the inverter so as to store energy on the DC side of the inverter, the battery can be charged through the inverter without using a special charging device during steady operation. When an abnormality occurs in the commercial power supply, it can instantly switch to the inverter power supply, and at the time of restoration, it is controlled to return at the zero cross timing of the input voltage.
Recovery control is possible without generating surge voltage. Even when an overcurrent occurs on the load side, drooping control that controls the output current to a constant level is possible. In the drooping control when an overcurrent occurs, the surge voltage generated by the switching of the AC switch unit is controlled so as to be absorbed, so that the switch element of the AC switch unit can be prevented from being damaged. When a DC power generator is used as the DC power source and the electromotive force is equal to or more than the load power consumption, it can be used as a device that feeds power to the commercial power source side through the AC switch unit in the inverter power feeding mode.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an outline of a configuration of an uninterruptible power supply according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an outline of a configuration of a control unit of the uninterruptible power supply according to the embodiment of this invention.

FIG. 3 is a diagram showing a specific connection configuration of an uninterruptible power supply according to an embodiment of the present invention.

FIG. 4 is a diagram showing a more specific configuration of the control unit of the uninterruptible power supply according to the embodiment of the present invention.

FIG. 5 is a waveform diagram illustrating current mode control according to the embodiment.

FIG. 6 is a waveform diagram illustrating voltage mode control according to the embodiment.

FIG. 7 is a waveform diagram illustrating drooping characteristic control according to the embodiment.

FIG. 8 is a diagram showing a configuration of a conventional constant inverter power supply type uninterruptible power supply device.

[Explanation of symbols]

1 AC Switch Section 2 Inverter Section 3 Filter Section 10 Inverter Power Calculation Section 11 Reference Current Calculation Sections 12, 13, 103 Comparison Section 14 Comparison Judgment Section 15 Changeover Switch 16 PWM Logic Circuit 17 Triangular Wave Generation Circuit 18 ACSW Switching Logic Circuit 19, 20 Overcurrent detection unit 30 Reference sine wave generation circuit 31 Phase synchronization circuits 33, 36 Multiplier 34 Average value circuit 35, 37, 38, 39, 41, 42 Comparison circuit 40 HL determination circuit 81 AC / DC converter 82 DC / AC inverter 83 Filter 84 ACSW CT ₁ , CT ₂ Current detector BA Battery

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Claims (2)

[Claims] 1. An AC switch (S ₁ connected to an AC power source)
, S ₂ ), a second power supply device including an inverter to which a DC power supply is connected, an input voltage detection means for detecting an input AC voltage, and a second power supply when the AC power supply detects a stop. In the uninterruptible power supply device including a control unit for operating the device, the control unit stops the first power supply device when the input voltage detection means detects an abnormality of the AC power supply, the second power supply device, A means for switching to a voltage mode control for providing an output AC voltage corresponding to the reference sine wave, and a means for switching to a current mode control for operating the second power supply device as an active filter when the abnormality of the AC power supply is recovered. An uninterruptible power supply characterized by that. 2. The means for switching to the current mode control comprises means for switching to the current mode control when the input voltage detected by the input voltage detecting means becomes zero on each cycle of the alternating current. Uninterruptible power system.