JP3316858B2 - Constant voltage / constant frequency power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant-voltage / constant-frequency power supply for inputting or outputting AC power having three or more phases and used for speed control of small single-phase induction motors, computers and the like. .

[0002]

2. Description of the Related Art A conventional typical constant-voltage / constant-frequency power supply for inputting and outputting three-phase alternating current is shown in FIG.
Converter switching circuit arm A formed by connecting two rectifier elements 1a, 1b, 1c, 1d, 1e, 1f in series.
A, A2, and A3 are connected in parallel by a number (three circuits) equal to the number of phases, a converter circuit A, a smoothing circuit B including a smoothing capacitor 2, and switching elements 3a, 3
b, 3c, 3d, 3e, 3f (usually accompanied by a flywheel diode 4 in parallel; the same applies hereinafter) inverter switching circuit arms C1, C2,
And an inverter circuit C constituted by connecting C2 and C3 in parallel by the same number (three circuits) as the number of phases. Each terminal of the AC power input unit 7 is connected between the rectifying elements of each converter switching circuit arm A1, A2, A3, and each terminal of the AC power output unit 8 is connected to each inverter switching circuit arm C1, C2. , C3.

[0003]

However, in the conventional constant voltage / constant frequency power supply device configured as described above, since both the converter circuit A and the inverter circuit C are full bridge circuits, the number of parts is large and the cost is low. Was higher.
In addition, one potential of the AC power input unit 7 does not match the corresponding one potential of the AC power output unit 8. Therefore, when this power supply circuit is used as an uninterruptible power supply, a short-circuit current flows through the bypass when switching between the power supply circuit and a bypass (not shown) (direct input / output circuit), which may cause malfunction or failure. There were also problems. These problems can be prevented by using a transformer. However, doing so increases the number of components, increases the size and weight of the device, increases the cost, and increases the power loss during operation.

The inventor has invented a variable voltage / variable frequency power supply apparatus shown in FIG. 6 in cooperation with other inventors (Japanese Patent Laid-Open No. 63-314176). In this power supply device, a converter circuit A is configured by connecting two rectifying elements 1a and 1b in series, a smoothing circuit B including smoothing capacitors 2a and 2b is connected to the converter circuit A, and an inverter circuit C is connected to a switching element. 3a, 3b are connected in series, one of the AC power input units 7 is connected between the rectifying elements 1a, 1b of the converter circuit A, and one of the AC power output units 8 is connected to the switching element of the inverter circuit C. 3a,
3b, and the other of the AC power input unit 7 and the other of the AC power output unit 8 are connected by a common line 9.
According to the present invention, the number of components can be reduced by reducing the number of transformers and the filter can be simplified, and a low-cost and high-precision power supply device can be obtained. However, this power supply circuit is for inputting and outputting single-phase AC power, and does not support AC power having three or more phases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to reduce the number of parts and to make the apparatus compact, lightweight and inexpensive, despite being able to input or output AC power having three or more phases. And a novel constant-voltage / constant-frequency power supply device capable of reducing power loss during operation.

[0006]

According to a first aspect of the present invention, there is provided a power supply device having three phases.
In the constant-voltage / constant-frequency power supply device for inputting and outputting the AC power, a converter switching circuit arm having at least two rectifiers or switching elements connected in series is subtracted by 1 from the number of phases of the input AC power. And a converter circuit configured by connecting at least two smoothing capacitors in series, and a smoothing circuit connected in parallel to the converter circuit and at least two switching elements connected in series. An inverter switching circuit arm comprising the inverter circuit connected in parallel with the number of phases of AC power to be output minus one, and an inverter circuit connected in parallel to the smoothing circuit. Each terminal except for one terminal is connected between the rectifying elements of the respective converter switching circuit arms or switched. Connected between the elements, each terminal leaving any one terminal of the AC power output unit, connected between the switching elements of the respective inverter switching circuit arm, the remaining one terminal of the AC power input unit, The remaining terminal of the AC power output unit is connected to a common line, and a connection between the smoothing capacitors of the smoothing circuit is connected to the common line.

According to a second aspect of the present invention, in the constant voltage / constant frequency power supply for inputting single-phase AC power and outputting AC power having three or more phases, at least two rectifying elements or switching elements are provided. A converter circuit configured by connecting in series, a smoothing capacitor configured by connecting at least two smoothing capacitors in series, a smoothing circuit connected in parallel to the converter circuit, and an inverter configured by connecting at least two switching elements in series A switching circuit arm is configured by connecting in parallel the number of phases of the output AC power by subtracting 1 and comprising an inverter circuit connected in parallel to the smoothing circuit, and having one terminal of the AC power input unit connected thereto. Connected between the rectifying element or the switching element of the converter circuit,
Each terminal except one terminal of the AC power output unit is connected between the switching elements of the respective inverter switching circuit arms, and the other terminal of the AC power input unit and the remaining of the AC power output unit And a common line, and a connection between the smoothing capacitors of the smoothing circuit is connected to the common line.

According to a third aspect of the present invention, in the constant voltage / constant frequency power supply for inputting AC power having three or more phases and outputting single-phase AC power, at least two rectifying elements or switching elements are provided. A converter switching circuit arm connected in series is connected in parallel by the number obtained by subtracting 1 from the number of input AC power phases, and at least two smoothing capacitors are connected in series. A smoothing circuit connected in parallel to the converter circuit, and an inverter circuit configured by connecting at least two switching elements in series and connected in parallel to the smoothing circuit; Are connected between the rectifying elements or between the switching elements of the respective converter switching circuit arms,
One terminal of the AC power output unit is connected between the switching elements of the inverter circuit, the other terminal of the AC power input unit and the other terminal of the AC power output unit are connected by a common line, It is characterized in that the smoothing capacitors of the smoothing circuit are connected to the common line.

[0009]

According to the first aspect of the present invention, when AC power having three or more phases is input from the AC power input unit, the AC voltage is rectified by the converter circuit and charges the smoothing capacitor of the smoothing circuit. And the ripple is smoothed. Here, since one terminal of the AC power input unit is held at the ground potential via the common line, the rectification is performed on the common line. The DC voltage generated in the smoothing capacitor is converted into AC power of a predetermined frequency with three or more phases by an inverter circuit and output from an AC power output unit. Here, since one terminal of the AC power output unit is also held at the ground potential via the common line, the conversion is performed on this common line. However, the AC output voltage does not become exactly the same as the AC input voltage, but becomes lower due to a voltage drop in the converter circuit, the inverter circuit, or the filter circuit and a voltage drop occurring at the time of switching.

[0010] According to the power supply device of the second aspect, the single-phase →
Except for the conversion of the number of phases of three phases, it has substantially the same operation as the above operation.

According to the power supply device of the third aspect, three phases
Except for the conversion of the number of phases, ie, a single phase, the operation is substantially the same as the above operation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is embodied in a constant-voltage / constant-frequency power supply device for inputting and outputting three-phase AC power will be described with reference to FIG. In the figure, A is a converter circuit, and rectifying elements 1a and 1 such as diodes.
b and a converter switching circuit arm A2 formed by connecting two rectifying elements 1c and 1d in series.
And are connected in parallel. B is a smoothing circuit connected in parallel to the converter circuit A, and is configured by connecting two smoothing capacitors 2a and 2b in series.

An inverter circuit C is connected in parallel with the smoothing circuit B, and includes an inverter switching circuit arm C1 formed by connecting two switching elements 3a and 3b such as bipolar transistors in series, and a switching element 3c and a switching element 3c. An inverter switching circuit arm C2 formed by connecting two 3d units in series is connected in parallel. A flywheel diode 4 is connected in parallel between the collector and the emitter of each of the switching elements 3a to 3d.

Numeral 7 is a three-terminal AC power input section connected to a three-phase AC power supply 12, one of which is connected to the rectifier elements 1a, 1a of the one converter switching circuit arm A1.
1b, and another terminal is connected between the rectifiers 1c and 1d of the other converter switching circuit arm A2.

Reference numeral 8 denotes an AC power output unit to which a load 13 is connected, one terminal of which is connected between the switching elements 3a and 3b of the one inverter switching circuit arm C1, and another terminal which is connected to the other inverter. It is connected between the switching elements 3c and 3d of the switching circuit arm C2.

The other terminal of the AC power input unit 7 and the remaining terminal of the AC power output unit 8 are connected by a common line 9, and the common line 9 is grounded. The common line 9 is connected to the smoothing capacitor 2 of the smoothing circuit B.
a and 2b are connected to each other.

The operation of the first embodiment configured as described above will be described. AC power input section 7
, This AC voltage is rectified by the converter circuit A, and the smoothing capacitors 2a and 2b of the smoothing circuit B
And the ripple is smoothed. Here, since one terminal of the AC power input unit 7 is held at the ground potential via the common line 9, the rectification is performed on the common line 9, and the ground potential is also applied between the smoothing capacitors 2a and 2b. Becomes The DC voltage generated in each of the smoothing capacitors 2a and 2b is converted into three-phase AC power of a predetermined frequency by the inverter circuit C, and output from the AC power output unit 8. Here, one terminal of the AC power output unit 8 is also held at the ground potential via the common line 9, so that the conversion is performed on the common line 9. Switching in the inverter circuit C is performed by, for example, a known PWM (pulse width modulation).
It can be done by control.

As described above, in the first embodiment, since the converter circuit A and the inverter circuit C are constituted by the number of elements smaller by one arm than the conventional full bridge circuit, the number of parts can be reduced. Can be. Also, since one terminal of the AC power input unit 7 and one terminal of the AC power output unit 8 are connected via the common line 9 and are both held at the ground potential, this power supply circuit is used as an uninterruptible power supply. In this case, even if an insulating transformer is not provided between the input and output, no short-circuit current flows through the bypass when switching between the power supply circuit and a bypass (not shown). Therefore, from this point as well, the number of parts can be reduced, the size, weight, and cost of the device can be reduced, and power loss during operation can be reduced. In the first embodiment, the AC output voltage is not exactly the same as the AC input voltage, and the rectifying elements 1a to 1d of the converter circuit A and the switching element 3 of the inverter circuit C are not used.
In the filter circuits a to 3d and a filter circuit (not shown), the voltage drop is caused by a voltage drop and a voltage drop generated during switching.

Next, the constant voltage / constant frequency power supply device of the second embodiment shown in FIG. 2 is different from the first embodiment only in the following points. The converter circuit A includes a converter switching circuit arm A1 formed by connecting two switching elements 11a and 11b in series and a converter switching circuit arm A2 formed by connecting two switching elements 11c and 11d in series. It is configured to be connected to. Each switching element 11a
Flywheel diodes 4 are connected in parallel to .about.11d. One terminal of the AC power input unit 7 is connected to the switching element 1 of the converter switching circuit arm A1.
Another terminal is connected between the switching elements 11c and 11d of the converter switching circuit arm A2 via the reactor 14. The other terminal is connected between the reactors 1a and 11b via the reactor 14.

The second embodiment configured as described above performs the following operations in addition to the substantially same operations as the first embodiment. That is, the reactor 14 and the switching elements 11a of the converter switching circuit arms A1 and A2,
11b. Since a boost chopper circuit is formed by 11c and 11d, the boost chopper circuit performs an operation of boosting the converted DC voltage by an amount corresponding to the voltage drop in the converter circuit A and the inverter circuit C. An AC output voltage that is exactly the same as the AC input voltage can be extracted from the AC power output unit 8 through a filter that is not used. If the switching frequency of the switching element of the converter unit is set to a high frequency (for example, 10 kHz or more), the reactor 14 needs to be small and lightweight, and does not substantially increase the size and weight of the power supply device.

Next, a third embodiment in which the present invention is embodied in a constant-voltage / constant-frequency power supply device that inputs single-phase AC power and outputs three-phase AC power will be described with reference to FIG. I do. This third embodiment differs from the first embodiment only in the following points. Converter circuit A
It is configured by connecting two rectifying elements 1a and 1b in series. One terminal of the AC power input unit 7 to which the single-phase AC power supply 12 is connected is connected to the rectifier element 1a of the converter circuit A,
1b, and the other terminal is connected to the other terminal of the AC power output unit 8 by a common line 9.

The third embodiment constructed as described above operates almost the same as the first embodiment except that the number of phases is changed from single phase to three phases. Incidentally, also in the third embodiment, it is possible to provide a boost chopper circuit as in the second embodiment.

Next, a fourth embodiment in which the present invention is embodied in a constant-voltage / constant-frequency power supply device that inputs three-phase AC power and outputs single-phase AC power will be described with reference to FIG. I do. The fourth embodiment differs from the first embodiment only in the following points. The inverter circuit C is
It is configured by connecting two switching elements 3a and 3b in series. One terminal of the AC power output unit 8 to which the single-phase AC load 13 is connected is connected between the rectifying elements 3a and 3b of the inverter circuit C, and the other terminal is connected to the rest of the AC power input unit 7 by the common line 9. Is connected to one terminal.

The fourth embodiment configured as described above has three
The operation is almost the same as that of the first embodiment except that the number of phases is changed from phase to single phase. Incidentally, also in the fourth embodiment, it is possible to provide a boost chopper circuit as in the second embodiment.

Note that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with appropriate modifications without departing from the spirit of the invention, for example, as follows. (1) As switching elements, besides the illustrated bipolar transistor, for example, GTO, MOSFET,
IGBT or the like can be used. (2) When the voltage to be handled is high and the withstand voltage of the element becomes a problem, a converter circuit, a smoothing circuit, or an inverter circuit can be obtained by connecting a larger number of rectifying elements, switching elements, smoothing capacitors, etc. in series than in the above embodiment. May be configured. (3) The present invention can also be embodied as a constant voltage / constant frequency power supply device that inputs or outputs polyphase AC power having more than three phases.

[0026]

As described in detail above, the constant voltage and the
According to the constant-frequency power supply device, although it is possible to input or output AC power having three or more phases, the number of components can be reduced, and the device can be configured small, light, and inexpensively. An excellent effect that power loss during operation can be reduced can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a constant voltage / constant frequency power supply circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a constant voltage / constant frequency power supply circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a constant voltage / constant frequency power supply circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a constant voltage / constant frequency power supply circuit according to a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram showing a conventional constant voltage / constant frequency power supply circuit.

FIG. 6 is a circuit diagram showing another conventional constant voltage / constant frequency power supply circuit.

[Explanation of symbols]

1a, 1b, 1c, 1d Rectifying element 2a, 2b Smoothing capacitor 3a, 3b, 3c, 3d Switching element 7 AC power input section 8 AC power output section 11a, 11b, 11c, 11d Switching element 14 Reactor A converter circuit A1, A2 Converter switching circuit arm B Smoothing circuit C Inverter circuit C1, C2 Inverter switching circuit arm

Claims (3)

(57) [Claims] 1. A constant voltage / constant frequency power supply device for inputting and outputting AC power having three or more phases, wherein a converter switching circuit arm comprising at least two rectifiers or switching elements connected in series is input. A converter circuit configured by connecting the number of phases of the AC power by subtracting 1 in parallel, a smoothing circuit configured by connecting at least two smoothing capacitors in series, and connected in parallel to the converter circuit; An inverter switching circuit arm comprising at least two elements connected in series, connected in parallel by a number obtained by subtracting 1 from the number of phases of the output AC power,
An inverter circuit connected in parallel to the smoothing circuit, wherein each terminal except one of the AC power input units is connected between the rectifying element or the switching element of each of the converter switching circuit arms, Each terminal of the AC power output unit, with one terminal remaining, is connected between the switching elements of each of the inverter switching circuit arms, and the other terminal of the AC power input unit and the AC power output unit. A constant-voltage / constant-frequency power supply device, wherein the other terminal is connected to a common line, and the smoothing capacitors of the smoothing circuit are connected to the common line. 2. A constant-voltage / constant-frequency power supply device for inputting single-phase AC power and outputting AC power having three or more phases, wherein at least two rectifying elements or switching elements are connected in series. A converter circuit and at least two smoothing capacitors are connected in series, and a smoothing circuit connected in parallel to the converter circuit and an inverter switching circuit arm formed by connecting at least two switching elements in series are output. It is configured by connecting in parallel the number of AC power phases minus 1 and
An inverter circuit connected in parallel to the smoothing circuit, wherein one terminal of the AC power input unit is connected between a rectifying element or a switching element of the converter circuit, and one terminal of the AC power output unit is left. Are connected between the switching elements of each of the inverter switching circuit arms, the other terminal of the AC power input unit and the other terminal of the AC power output unit are connected by a common line, and the smoothing is performed. A constant-voltage / constant-frequency power supply device, wherein smoothing capacitors of a circuit are connected to the common line. 3. A constant-voltage / constant-frequency power supply device for inputting AC power having three or more phases and outputting single-phase AC power, comprising a converter having at least two rectifiers or switching elements connected in series. A switching circuit arm is configured by connecting in parallel the number of phases of the input AC power less one, and a converter circuit configured by connecting at least two smoothing capacitors in series, and is configured in parallel with the converter circuit. A connected smoothing circuit, and an inverter circuit configured by connecting at least two switching elements in series and connected in parallel to the smoothing circuit, wherein each terminal except one terminal of the AC power input unit is connected. Connected between the rectifier elements or between the switching elements of each of the converter switching circuit arms, and one terminal of an AC power output unit is connected to the inverter. A common line between the other terminal of the AC power input unit and the other terminal of the AC power output unit, and a common line between the smoothing capacitors of the smoothing circuit. A constant-voltage / constant-frequency power supply device, characterized in that it is connected to a power supply.