JPH09130995A - Uninterruptive power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to operate an inverter always with the highest modulation factor and design a transformer with a high primary voltage by separating a converter input from a commercial power supply and connecting it to a battery during commercial power interruption and operating the converter as a booster chopper using a battery voltage as a power source. SOLUTION: First switching means 7 which opens the circuit in response to a detection signal from power interruption detection means 12 is provided at the input side of a commercial power supply 1 and a converter 2. And second switching means 8 is provided constituting a booster chopper circuit, which is closed in response to a detection signal of power interruption detection means 12 and connects a positive terminal of a battery 6 to at least one input terminal of the converter 2 and also connects a negative terminal of the battery 6 to a negative terminal of the converter 2. In this way, a control voltage range of the inverter 3 can take a higher primary voltage of a transformer accordingly, thereby permitting a decrease in a current applied to a semiconductor during normal operation.

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 system for supplying a load with electric power from a storage battery when a commercial power supply fails, and more particularly to an inverter for normal operation by suppressing the storage battery voltage range during a power failure. The present invention relates to an uninterruptible power supply device capable of increasing a voltage utilization rate and reducing an energization current of an element.

[0002]

2. Description of the Related Art In recent years, in a power converter, adoption of harmonic pulse width modulation control using a high-speed switching element has been applied to both converters and inverters in order to improve the performance of power conversion. Since it can supply high-quality power to loads, it is widely used in uninterruptible power supplies and the like.

The structure of a conventional uninterruptible power supply will be described with reference to FIG. In the figure, 1 is a commercial power supply, 2 is a converter that is composed of semiconductor elements such as transistors, and has a function of converting AC to DC, 3 is an inverter that converts the DC converted by the converter 2 into AC, and 4 is an inverter 3
Is a transformer for converting the AC voltage of
Reference numeral 6 is a backup storage battery that supplies DC power to the inverter 3 when the commercial power supply 1 fails. Also, 11
Is an AC voltage detector such as an insulation transformer for converting the voltage of the commercial power supply 1 into a voltage of a control circuit level, and 12 is a level judgment of the output of the AC voltage detector 11 to detect an abnormal voltage drop or power failure of the commercial power supply 1. A power failure detector, 13 is a gate switching control circuit of the converter 2.

Next, the operation of the uninterruptible power supply will be described. When the commercial power source 1 is healthy, the power of the commercial power source 1 is converted into DC power by the converter 2 and the storage battery 6 is charged to a predetermined DC voltage, and at the same time, the inverter is used. Input of 3.
The electric power converted into alternating current by the inverter 3 is supplied to the load 5 via the transformer 4.

On the other hand, when the commercial power source 1 fails, the voltage of the commercial power source 1 is detected by the power failure detection circuit 12 via the AC voltage detector 11 and the gate switching control circuit 13 is conditioned on the power failure detection.
Deactivates the converter gate. Therefore, the input of the inverter 3 is only the storage battery 6, and the load 6 is supplied via the inverter 3 and the transformer 4 by the amount of energy held by the storage battery 6.
Can continue to be powered.

The advantage of using the self-excited converter will be briefly described below. Unlike general thyristor rectifiers, active power and reactive power can be controlled independently.
If the input power factor is controlled to 1, it is possible to minimize the required input capacity of the uninterruptible power supply, and if the semiconductor element of the self-exciting converter is subjected to pulse width modulation control (called PWM control), It is indispensable for the recent uninterruptible power supply because it can suppress the harmonic current generated in the commercial power supply 1.

[0007]

In the uninterruptible power supply having such a structure, the fluctuation range of the storage battery voltage has an important meaning. That is, even when the commercial power supply 1 fails, the input of the inverter 3 becomes only the storage battery 6, the energy of the storage battery 6 is discharged, and the storage battery voltage gradually decreases, the inverter 3 performs the pulse width modulation control to obtain a desired voltage. It must be designed so that it can be put out. Therefore, it is necessary to specify the maximum modulation rate of the inverter 3 by the discharge end voltage of the storage battery 6.

Generally, the storage battery 6 has a nominal voltage of 2.0 V per cell and a discharge end voltage of 1.6 V, so the maximum modulation rate of the inverter 3 is designed at a storage battery voltage of 80% (1.6 / 2). , Which determines the primary voltage of the transformer 4.
In other words, the primary voltage of the transformer 4 is designed so as to guarantee a short period of time when the storage battery 6 reaches the discharge end voltage, and normally has the ability to output this 120% voltage, It means that the voltage is reduced.

Due to this restriction, the primary voltage of the transformer 4 is inevitably suppressed to a voltage of about 80% of the maximum modulation rate in the normal state, so that the energizing current of the semiconductor element increases accordingly. In general, the loss of a semiconductor element is proportional to the current flowing through it and is almost constant with respect to the voltage, so increasing the current flowing hinders the downsizing of the cooler of the semiconductor element and improves the efficiency of the UPS. Has become a factor that hinders.

Therefore, an object of the present invention was made in view of the above-mentioned points, and in an uninterruptible power supply device in which a converter, an inverter transformer and a storage battery are combined, the inverter voltage utilization rate is improved and the semiconductor device An object of the present invention is to provide an uninterruptible power supply device that can reduce the size of a cooler for semiconductor devices and improve device efficiency by reducing the energization current.

[0011]

In order to achieve the above object, the invention according to claim 1 is a converter for converting an alternating current supplied from a commercial power source into a direct current, and an inverter for converting the direct current into an alternating current. An uninterruptible power supply including a storage battery that backs up the direct current when the commercial power source fails, and a power failure detection unit that detects a power failure of the commercial power source; and the power failure detection provided on the input side of the commercial power source and the converter. First opened in response to the detection signal of the means
Closed circuit, and closed in response to the detection signal of the power failure detection means, the positive terminal of the storage battery is connected to at least one input terminal of the converter, the negative terminal of the storage battery is connected to the negative terminal of the converter. The present invention is characterized in that it is provided with a second opening / closing means which constitutes a booster chipper circuit constituted by the above.

Further, the invention according to claim 2 is a converter for converting an alternating current supplied from a commercial power source into a direct current, an inverter for converting the direct current into an alternating current, and a backup of the direct current when the commercial power source fails. In an uninterruptible power supply device equipped with a storage battery, a power failure detection means for detecting a power failure of the commercial power supply, and a first opening / closing circuit provided on an input side of the commercial power supply and the converter and opened by a detection signal of the power failure detection means. Means and a booster chipper circuit closed by the detection signal of the power failure detection means, the positive terminal of the storage battery being connected to at least one input terminal of the converter, and the negative terminal of the storage battery being connected to the negative terminal of the converter. Second opening / closing means, a power recovery detecting means for detecting power recovery of the commercial power source, and a bypass switch from the commercial power source. A bypass circuit for supplying power to the load Te,
Switching control that opens the bypass switch by closing the bypass switch in response to the detection signal of the power recovery detection unit and returning the converter and the inverter fed through the first opening / closing unit to normal operation. It is characterized by comprising means.

Further, the invention according to claim 3 is such that at least two converters for converting alternating current supplied from a commercial power source into direct current, an inverter for converting the direct current to alternating current, and a diode for the inverter. In an uninterruptible power supply device that is connected to a direct current circuit and includes a storage battery that backs up the direct current when the commercial power source fails, a power failure detection unit that detects a power failure of the commercial power source, and an input side of the commercial power source and the converter. An opening / closing means that is provided and is opened in response to a detection signal of the power failure detecting means, and operates the converters as a step-up chipper by using the storage battery as an input power source in response to the detection signal of the power failure detecting means, and the commercial power source. When the power is restored, one of the converters continues to operate as a step-up chipper, and the other converter receives the commercial power as an input. After operating as a transducer, it is characterized in that each converter equipped with a switching means for switching to operate as AC to DC conversion device.

[0014]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the invention described in claim 1 will be described below with reference to the block diagram of FIG. However,
The components denoted by the same reference numerals as those in FIG. 6 of the conventional art have the same functions as those of the conventional art, and therefore the description thereof will be omitted.

In FIG. 1, the difference from the prior art is that the first switching means 7 provided on the input side of the commercial power source 1 and the converter 2 and opened in response to the detection signal of the power failure detection means 12, and the power failure detection. A booster chipper circuit is formed which is closed in response to the detection signal of the means 12 and in which the positive terminal of the storage battery 6 is connected to at least one input terminal of the converter 2 and the negative terminal of the storage battery 6 is connected to the negative terminal of the converter 2. The second opening / closing means 8 is provided.

FIG. 2 is a block diagram showing a concrete example of the converter 2 and that the boosting chipper circuit is constituted by the second opening / closing means 8. The operation when the commercial power source 1 fails will be described. When the commercial power source 1 fails, the power failure detecting means 12 performs level determination to detect the power failure, and the first opening / closing means 7 is opened and the second opening / closing means 8 is opened. Switch from the (b) side to the (a) side. At the time when the second opening / closing means 8 is on the (b) side, the voltage of the storage battery 6 has sufficient energy, and at the voltage of about 1.9 V per cell, the storage battery 6 drives the inverter 3 via the second opening / closing means 8. Convert to AC, transformer 4
Power is supplied to the load 5 via the. When the second opening / closing means 8 is switched from the (b) side to the (a) side as shown in FIG. 2, the storage battery 6 is switched from the output of the converter 2 to the input, and the converter 2 is operated as a boost chopper. To do. The operation of the boost chopper will be described with reference to the circuit of FIG.
The transistor 21V on the side is reverse-biased to stop its operation. The energy of the reactor 24 is transferred to the DC capacitor 25 by controlling the pulse width of the transistor 21Y on the N side, and the output voltage is controlled to be higher than the input voltage. It is a method that can.

That is, if the transistor 21Y is turned on,
A closed circuit composed of the positive electrode terminal of the storage battery → the (a) side of the second opening / closing means 8 → one input terminal V of the converter 2 → reactor 24 → transistor 21Y → the negative electrode terminal of the storage battery 6 is formed, and the current of the reactor 24 is formed. Rises. When the current of the reactor 24 rises to some extent, the transistor 2
Turn off 1Y. When the transistor 21Y is turned off, the current of the reactor 24 changes from the reactor 24 to the diode 22.
V → DC capacitor 25 → storage battery 6 → second opening / closing means 8
→ A circuit of the reactor 24 is formed, and the stored energy of the reactor 24 is transferred to the DC capacitor 25. Reactor 2
When the current of 4 drops to a predetermined value, the transistor 21Y
Is turned on, and the same operation is performed thereafter, so that the voltage of the DC capacitor 25 can be boosted to the voltage of the storage battery 6 or higher. In the above description, the V-phase arm is operated as a step-up chopper, but if the U-phase terminal and the V-phase terminal are commonly connected, the U-phase arm can also be operated simultaneously as a step-up chopper. In this way, by switching the second opening / closing means 8 from the output side (b) of the converter 2 in FIG. 2 to the input side (a) of the converter, the blackout of the commercial power source 1 continues for a long time and the voltage of the storage battery 6 becomes 1 0.7V or 1.6V
Since the converter 2 is operated as a step-up chopper even when the voltage drops to 0, the DC input voltage of the inverter 3 does not decrease, and the control voltage range of the inverter 3 can be designed in the same manner as when the commercial power supply is normal.

Therefore, the control voltage range of the inverter 3 is
Unlike the conventional case, the storage battery 6 is not designed in consideration until it reaches the discharge end voltage. Therefore, by enlarging the primary voltage of the transformer 4 by that amount, the conduction current of the semiconductor element in the normal operation can be reduced. Therefore, the cooler for the semiconductor element can be downsized and the efficiency of the uninterruptible power supply can be improved.

1 and 2, the contact b of the second opening / closing means 8 is necessary when the storage battery 6 is charged by the converter 2, and is omitted when charging from another charging device. You can also do it.

The power failure detecting means 12 includes not only a power failure of the commercial power source 1 but also an abnormal voltage drop. Next, another embodiment of the invention described in claim 1 will be described with reference to FIG. 3 in which the same parts as those in FIG.

In the figure, the point different from FIG. 1 is that the first switching means 7 and the second switching means 8 are replaced with semiconductor switches. In the embodiment of FIG. 1, since the switching of the storage battery 6 at the time of power failure or power recovery is a mechanical switch, the DC voltage drops for 20 to 40 ms during which the DC voltage switches at the time of switching, and the output voltage may fluctuate. Since it is necessary to attach an electrolytic capacitor (DC capacitor 25) having a sufficiently large capacity, there is a need for the second opening / closing means 8 during a power failure.
After closing the switch, the charging switch is opened and the second
It is possible to prevent the DC voltage from decreasing by opening the opening / closing means 8 and closing the first opening / closing means 7 at the same time.

Next, an embodiment of the invention described in claim 2 will be described with reference to FIG. 4 in which the same parts as those in FIG. 1 is different from FIG. 1 in that a bypass circuit 14A for supplying electric power from the commercial power source 1 to the load 5 via the bypass switch 14B is added, and the power recovery detecting means 15 is used when the commercial power source 1 is recovered. Switching control means 16 for controlling switching between the inverter 3 and the bypass switch 14B
Is added. In the embodiment shown in FIG. 1, the time until the converter is normally operated after the second switching means 8 is switched from the converter input to the converter output when the commercial power source 1 is restored, and then the first switching means 7 is turned on. In contrast to the point that it is necessary to mount the electrolytic capacitor 25 having a sufficiently large capacity in order to prevent the output voltage from fluctuating due to the reduction of the DC voltage, the load 5 is output by the output of the power recovery detecting means 15 at the time of power recovery After switching the bypass switch 14B from the inverter 3 to the bypass circuit 14A, the second opening / closing means 8 is switched from the converter input to the converter output.
The converter 2 is normally operated through the first opening / closing means 7, the inverter 3 is operated, and at the same time, the bypass switch 14B is extinguished again, and the power supply to the load 5 is switched from the bypass circuit 14A to the inverter 3 side. It is a point. As a result, it is possible to prevent the output voltage from varying when the commercial power supply 1 is restored.

Next, an embodiment of the invention described in claim 3 will be described with reference to FIG. 5 in which the same parts as those in FIG. 1 is different from FIG. 1 in that two converters 2 are provided in order to increase the capacity of the converter 2, and a switching means 30 for operating these converters as a step-up chopper circuit or an AC / DC converter. The point is that a diode 31 for connecting the storage battery 6 to the output side of the converter 2 and a charger 32 for charging the storage battery 6 are provided.

The opening / closing means Mb provided on the input side of the commercial power source 1 and the converter 2 and opened in response to the detection signal of the power failure detection means 12 is, for example, an output signal of the power failure detection means 12 (a contact point that is closed by the power failure detection). ), The normally-closed contact of an instantaneous action instantaneous return type contactor M (hereinafter simply referred to as contactor M) is used. Further, the switching means 30 is, for example, a normally open contact Ma of the contactor M and an instantaneous operation time-delaying contactor (hereinafter referred to as a contactor which is excited in response to an output signal of the power failure detection means 12 (contact closed when power failure is detected). A contactor T) and a normally open contact Ta and a normally open contact Ta.

According to the third aspect of the present invention configured as described above, when the commercial power source 1 is normal, the contactors M and T are not excited, so that the normally closed contacts Mb and Tb are closed. The two converters 2 convert the alternating current fed from the commercial power source 1 into direct current, convert the converted direct current into alternating current by the inverter 3, and feed the load 5 through the transformer 4. It will be.

Next, the operation at the time of power failure will be described. When a power failure occurs, the input of the converter 2, that is, the commercial power supply voltage becomes zero, but the input direct current of the inverter 3 is instantaneously supplied from the storage battery 6 via the diode 31, and then the normally closed contact M
Since b and Tb are opened and the normally open contacts Ma and Ta are closed, the two converters 2 operate as a booster chipper using the storage battery 6 as an input power source. When the DC voltage of the converter 2 operating as the step-up chipper becomes higher than the voltage of the storage battery 6, the diode is turned off.

When the commercial power supply 1 is restored from the above-mentioned state, the normally closed contact Mb is closed, the normally closed contact Tb is open, and the normally open contact Ta is closed, so that the lower converter 2 is The converter 2 on the upper side continues to operate as a booster chipper, and operates as an AC / DC converter fed from the commercial power source 1. After that, after the time limit of the contactor T, the normally closed contact Tb is closed and the normally open contact Ta is opened.
Return to normal operation.

As described above, according to the embodiment shown in FIG. 5, even if mechanical contacts are used for the opening / closing means Mb and the switching means 30, the commercial power source 1 is not affected by the delay of the operation time and a power failure occurs. However, in the process of recovering from the power failure, it is possible to prevent the DC voltage of the converter from decreasing. In the embodiment of FIG. 5, the opening / closing means Mb and the switching means 30 are not limited to mechanical contacts, but semiconductor switches may be used.

[0029]

As described above, according to the first to third aspects of the present invention, the converter input is disconnected from the commercial power source and connected to the storage battery at the time of the commercial power source power failure, and the converter uses the storage battery voltage as the power source. By operating as a step-up chopper, the inverter input voltage can be suppressed to a constant value even when the storage battery approaches the discharge end voltage, and by operating the inverter at the maximum modulation rate at all times,
The primary voltage of the transformer can be designed high. Therefore, the current flowing through the semiconductor element of the inverter can be suppressed to a low level, and the semiconductor loss can be reduced, thereby improving the efficiency of the device.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram showing an embodiment of an uninterruptible power supply according to the invention described in claim 1.

FIG. 2 is a detailed circuit diagram of the converter shown in FIG. 1 and operating the converter as a step-up chopper.

FIG. 3 is a block configuration diagram showing another embodiment of the uninterruptible power supply device according to the invention described in claim 1.

FIG. 4 is a block diagram showing an embodiment of an uninterruptible power supply device according to the invention described in claim 2.

FIG. 5 is a block configuration diagram showing an embodiment of an uninterruptible power supply device according to the invention described in claim 3.

FIG. 6 is a block configuration diagram of a conventional uninterruptible power supply.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Converter 3 ... Inverter 4 ... Transformer 5 ... Load 6 ... Storage battery 7 ... 1st opening / closing means 8 ... 2nd opening / closing means 11 ... AC voltage detector 12 ... Blackout detection means 13 ... Gate switching control Circuit 14A ... Bypass circuit 14B ... Bypass switch 15 ... Power recovery detection means 16 ... Switching control means 21 ... Transistor 22 ... Diode 23 ... Reactor 24 ... Reactor 25 ... DC capacitor Mb ... Opening / closing means 30 ... Switching means 31 ... Diode 32 ... Charging vessel

Claims (3)

[Claims] 1. An uninterruptible power supply comprising a converter for converting alternating current supplied from a commercial power supply to direct current, an inverter for converting the direct current to alternating current, and a storage battery for backing up the direct current when the commercial power supply fails. A power failure detecting means for detecting a power failure of the commercial power source; a first opening / closing means provided on an input side of the commercial power source and the converter and opened in response to a detection signal of the power failure detecting means; Closed in response to the detection signal of the means,
The present invention further comprises a second opening / closing means forming a step-up chipper circuit in which the positive terminal of the storage battery is connected to at least one input terminal of the converter and the negative terminal of the storage battery is connected to the negative terminal of the converter. And an uninterruptible power supply. 2. An uninterruptible power supply device comprising: a converter that converts alternating current supplied from a commercial power supply to direct current; an inverter that converts the direct current to alternating current; and a storage battery that backs up the direct current when the commercial power supply fails. A power failure detecting means for detecting a power failure of the commercial power source, a first opening / closing means provided on the input side of the commercial power source and the converter and opened by a detection signal of the power failure detecting means, and a detection of the power failure detecting means A second opening / closing means forming a booster chipper circuit, which is closed by a signal, the positive terminal of the storage battery is connected to at least one input terminal of the converter, and the negative terminal of the storage battery is connected to the negative terminal of the converter; A power recovery detection means for detecting power recovery of the commercial power supply, and a bypass for supplying power to the load from the commercial power supply via a bypass switch Circuit, and the bypass switch is closed in response to the detection signal of the power recovery detection means, and the bypass switch is opened when the converter and the inverter fed through the first opening / closing means return to normal operation. An uninterruptible power supply device comprising a switching control means for switching. 3. A commercial power supply, which is connected to at least two converters for converting alternating current supplied from a commercial power supply to direct current, an inverter for converting the direct current to alternating current, and a direct current circuit of the inverter through a diode. In an uninterruptible power supply device equipped with a storage battery that backs up the direct current in the event of a power failure, a power failure detection means for detecting a power failure of the commercial power supply, and a detection signal of the power failure detection means provided on the input side of the commercial power supply and the converter In response to the detection signal of the power failure detection means, the storage battery as an input power source to operate each of the converters as a booster, and one of the converters when the commercial power source is restored. After continuing the operation as a booster chipper and operating the other converter as an AC / DC converter using the commercial power source as an input Uninterruptible power supply, characterized by comprising a switching means for switching to operate as well AC-DC converter wherein one of the converter.