JPH09331684A - Non-insulated type uninterruptible power-supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-insulated type uninterruptible power-supply unit which can attain the size, weight and cost reduction of this unit and elimination of output voltage imbalance by making a transformer for obtaining single-phase three-wire output unnecessary. SOLUTION: In this uninterruptible power-supply unit which is provided with a converter, an inverter and a battery which is used as a DC voltage source for inverter in case of power failure, the inverters are constituted by parallel-connecting the first and second half-bridge type inverters 410, 420 having a semiconductor switch fitted at upper and lower arms respectively. An AC output terminal 10 of single-phase three-wire type is constituted of the interconnection points of the first and second capacitors 71, 72 connected between one end of a single AC power source 1 and a DC output terminal of a converter 200, and AC output terminals of the inverters 410, 420. This unit is controlled so that the AC output voltage of the inverters 410, 420 may be in a negative phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-insulated uninterruptible power supply device which can obtain a single-phase three-wire AC output from a single-phase two-wire AC input without using a transformer.

[0002]

2. Description of the Related Art FIG. 4 shows the structure of a power failure power supply unit 20 as a conventional technique. In FIG. 4, 1 is a single-phase AC power supply, 2 is an AC / DC converter (converter), 3 is a battery, 4 is a DC / AC converter (inverter), 5 is a transformer, 6 is a control circuit of the inverter 4, 7 is a DC smoothing capacitor, 8 is a switch 9 is a single-phase two-wire AC input terminal,
Reference numeral 10 is a single-phase three-wire AC output terminal.

In the above structure, the AC input voltage is converted into a DC voltage by the converter 2, and this DC voltage is converted into a stable AC voltage by the inverter 4. Since the inverter 4 has a single-phase two-wire output, it is converted into a single-phase three-wire output by the transformer 5. The transformer 5 is of an insulating type or a single winding type. The battery 3 is connected to the inverter 4 via the switch 8 when the single-phase AC power source 1 fails.
It is intended to supply a DC voltage to the power supply, and thereby the function as an uninterruptible power supply is fulfilled.

[0004]

In this prior art, the transformer device for converting the output of the inverter 4 into a single-phase three-wire output is downsized, lightened, and the cost reduction device 5 is downsized.
It was a cause of hindering weight reduction and price reduction. Also,
As shown in FIG. 5, loads 11, 1 are provided between the AC output terminals 10.
When connecting two in series and feeding power, if the power consumption of the loads 11 and 12 is extremely different, there is a problem that the output voltage becomes unbalanced due to the voltage drop of the transformer 5.

Therefore, the present invention intends to provide an uninterruptible power supply device which eliminates the need for a transformer for obtaining a single-phase three-wire output, makes the device compact, lightweight, and low-priced, and eliminates the imbalance of the output voltage. It is what

[0006]

In order to solve the above problems, the invention according to claim 1 is a converter for converting AC power from a single-phase AC power supply into DC power, and an inverter for converting the DC power into AC power. And a battery used as a DC power source for the inverter during a power failure of the single-phase AC power source, wherein the inverter has a semiconductor switch in each of upper and lower arms.
A second half-bridge inverter connected in parallel, and an interconnection point of the first and second capacitors connected between one end of the single-phase AC power supply and the DC output terminal of the converter; The AC output terminals of the first and second half-bridge type inverters constitute a single-phase three-wire AC output terminal.

According to a second aspect of the present invention, in the non-insulated uninterruptible power supply device according to the first aspect, the AC output voltages of the first and second half-bridge inverters are controlled to have opposite phases. It is a thing. As a result, the voltages applied to the two loads connected to the other AC output terminals with the common connection point of the first and second capacitors in common become equal.

According to a third aspect of the present invention, in the non-insulated uninterruptible power supply according to the first aspect, the AC output terminals of the first and second half-bridge type inverters are short-circuited, and the AC output voltage of these inverters is short-circuited. Are controlled so that they are in phase, and the interconnection point of the first and second capacitors,
A single-phase two-wire type AC output terminal is constituted by the AC output terminal of the first or second inverter. According to the present invention, the main circuit of the uninterruptible power supply according to claim 2 is left as it is, the AC output terminals of the first and second half-bridge type inverters are short-circuited, and the control method is changed. A two-wire non-insulated uninterruptible power supply can be realized.

According to a fourth aspect of the present invention, in the non-insulated uninterruptible power supply unit according to the first, second or third aspect, the converter is a half bridge type converter having semiconductor switches in upper and lower arms. It is a thing.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of this embodiment, and the same components as those in FIGS. 4 and 5 are designated by the same reference numerals. In FIG. 1, reference numeral 100 denotes the uninterruptible power supply device of this embodiment, which has an AC input terminal 9 connected to the single-phase AC power supply 1 and a single-phase three-wire AC output connected to the loads 11 and 12 as described above. And a terminal 10. In addition, 1
9 is a neutral line.

In the uninterruptible power supply system 100, a half bridge converter 200 is connected to the AC input terminal 9 via a capacitor 13 and a reactor 14 which form a filter.
Is connected. This converter 200 is an IGBT
A semiconductor switch 201, 202, which is an antiparallel circuit of a semiconductor switching element such as an (insulated gate bipolar transistor) and a diode, is provided on the upper and lower arms.

Between the DC output terminals of the converter 200,
First and second capacitors 71 and 72, which serve as a DC power source for half-bridge type inverters 410 and 420 described later, are connected in series. In addition, these capacitors 71,
A series circuit of the switch 8 and the battery 3 is connected to both ends of the series circuit of 72 as in the conventional case.

Further, the semiconductor switches 401 and 402 of the upper and lower arms are provided at both ends of the series circuit of the capacitors 71 and 72.
A first half-bridge inverter 410 consisting of
A second half-bridge inverter 420, which is also composed of semiconductor switches 403 and 404, is connected in parallel. The reactors 15 and 16 and the capacitors 17 and 18 that form a filter are connected between the AC output terminals of the inverters 410 and 420 and the interconnection points of the capacitors 71 and 72.
Both ends of 7, 18 are connected to the AC output terminal 10.

The voltage across the capacitors 17 and 18 (the voltage across the loads 11 and 12, that is, the single-phase output voltage v
1, v2) are input to the control circuits 405 and 406, and the semiconductor switches 401 to 404 of the inverters 410 and 420 are turned on / off by the drive pulses generated so that these voltages have the set values. Here, the control circuit of the converter 200 is not shown for convenience. The converter 200 and the inverters 410 and 420
As the semiconductor switching element of, M other than IGBT
OSFET etc. may be used.

Next, the operation of this embodiment will be described. First, the converter 200 converts an AC input voltage into a DC voltage and charges the capacitors 71 and 72 to the same voltage value. The inverters 410 and 420 include capacitors 71 and 7
The control circuit 405 and 406 control the output voltages v1 and v2 so that the output voltages v1 and v2 are stable and constant values with the voltage of 2 as the DC power supply voltage. Here, the point that the inverters 410 and 420 are operated by using the battery 3 as a power source when the single-phase AC power source 1 is out of power is similar to the conventional one.

In this embodiment, the control circuits 405 and 4 are arranged so that the output voltages v1 and v2 viewed from the neutral point 19 have opposite phases.
06 is operated. FIG. 2 shows waveforms of the output voltages v1 and v2 and the output voltage v3 across the series circuit of the loads 11 and 12, and the amplitudes of the output voltages v1 and v2 are a and b (a = b), respectively. Then, the amplitude c of the output voltage v3 is a
+ B (c = a + b). As a result, the single-phase, three-wire type power supply device can supply power to the loads 11 and 12 at the same voltage.

When the rated capacity of the device of this embodiment is (load 11 + load 12), another load 22 whose individual load capacity corresponds to (load 11 + load 12)
Fig. 3 shows the correspondence when the power is supplied by the single-phase two-wire system. FIG.
In the above, reference numeral 21 is a switch that short-circuits the AC output terminals of the inverters 410 and 420, and the fact that this switch has operated can be transmitted to the control circuits 405 and 406 as a switch operation signal. In addition, 100 A is an uninterruptible power supply device of the present invention (claim 3), and power is supplied to the load 22 from the single-phase two-wire AC output terminal 10.

In this case, the switch 21 short-circuits the AC output terminals of the inverters 410 and 420, and the control circuits 405 and 406 control the operation so that the output voltages of the inverters 410 and 420 are in phase. As a result, a system that operates the inverters 410 and 420 in parallel to supply power to the load 22 is configured, and a power supply device for single-phase two-wire output can be configured. If you do this,
Since it is possible to switch between single-phase three-wire system and single-phase two-wire system without changing the main circuit configuration of the uninterruptible power supply,
It is highly economical and versatile.

[0019]

As described above, according to the present invention, a transformer is not required in the case of single-phase three-wire output, and the overall size and weight of the device can be reduced and the cost can be reduced. Further, even in the single-phase three-wire output, the supply voltage to each load can be individually stabilized, so that a more stable output voltage can be obtained against load imbalance than when a transformer is used.
Furthermore, since it is possible to switch between the single-phase three-wire system and the single-phase two-wire system without changing the main circuit configuration, there are effects such as high versatility and high economical efficiency.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of output voltage waveforms in the embodiment of FIG.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional technique.

FIG. 5 is a circuit diagram showing a connection state between the conventional technique of FIG. 4 and a load.

[Explanation of symbols]

 1 Single-phase AC power supply 3 Battery 8 Switch 9 AC input terminal 10 AC output terminal 11, 12, 22 Load 13, 17, 18, 71, 72 Capacitor 14, 15, 16 Reactor 19 Neutral point 21 Switch 100, 100A Uninterruptible Power supply device 200 Half bridge type converter 201, 202, 401-404 Semiconductor switch 405, 406 Control circuit 410, 420 Half bridge type inverter

Claims (4)

[Claims] 1. A converter for converting AC power from a single-phase AC power supply into DC power, an inverter for converting the DC power into AC power, and a battery used as a DC power supply for the inverter during a power failure of the single-phase AC power supply. In the uninterruptible power supply device including :, the inverter is configured by connecting in parallel first and second half-bridge type inverters each having a semiconductor switch in upper and lower arms, and A single-phase three-wire type AC output terminal is formed by the interconnection point of the first and second capacitors connected to the DC output terminal of the converter and the AC output terminals of the first and second half-bridge inverters. A non-insulation type uninterruptible power supply characterized by being configured. 2. The non-insulated uninterruptible power supply device according to claim 1, wherein the AC output voltages of the first and second half-bridge inverters are controlled to have opposite phases. Uninterruptible power system. 3. The non-insulated uninterruptible power supply device according to claim 1, wherein the AC output terminals of the first and second half-bridge inverters are short-circuited so that the AC output voltages of these inverters are in phase. A non-isolated, single-phase two-wire AC output terminal that is controlled and that is configured by the interconnection point of the first and second capacitors and the AC output terminal of the first or second inverter. Type uninterruptible power supply. 4. The non-insulated uninterruptible power supply unit according to claim 1, 2, or 3, wherein the converter is a half-bridge converter including semiconductor switches in upper and lower arms. Isolated uninterruptible power supply.