JPS6244072A - Ac power source - Google Patents

Abstract

PURPOSE:To obtain an AC power insulated from the power source and having small harmonic wave components, by supplying the AC output of an inverter through a transformer to a separately-excited converter, and producing the output of the converter through a filter capacitor. CONSTITUTION:A DC power source 10 is connected to a transistor inverter 11 to convert a DC into an AC of high frequency. After the AC is insulated by a transformer 12, it is supplied to a separately-excited converter composed of anti-parallel connection of rectifiers 15, 16. This converter phase-controls the AC output from the inverter 11. The harmonic wave of the output of the converter is removed by a filter capacitor 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an alternating current imaging device that is insulated from a power source and outputs alternating current with little waveform distortion.

[Prior art and its problems]

Electronic devices such as uninterruptible power supplies often require AC power that does not contain harmonic components and is isolated from the power supply. As a device that outputs such AC power, it is common to use an inverter device that is composed of a rectifier that rectifies the AC power source and an inverter that converts the DC output from the rectifier into AC.
Insert an isolation transformer on the AC power supply side or inverter output side for insulation. However, since the alternating current on both the power supply side and the output side is a commercial frequency, this transformer has the disadvantage of being large and expensive.

Furthermore, it is necessary to use a pulse width modulation type inverter in order to reduce harmonics of the alternating current outputted by the inverter as much as possible.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact AC power supply device that is insulated from a power source and can output AC power that does not contain harmonic components.

[Key points of the invention]

This invention converts DC power into high-frequency AC power using an inverter made of semiconductor switching elements with a high operating frequency, and inputs the converted power to an insulating transformer. A separately commutated converter is formed by connecting rectifiers obtained by combining series circuits of transistors and diodes in antiparallel to each other, and an AC input terminal of the separately commutated converter is connected to an AC input terminal insulated by the above-mentioned transformer. Let the power be input! By controlling the phase of the transistors that make up the current regulator, one rectifier outputs a positive voltage and the other rectifier outputs a negative voltage, thereby obtaining AC power with few harmonic components. This is what we are trying to do.

[Embodiments of the invention]

FIG. 1 is a circuit connection diagram showing a first embodiment of the present invention. In FIG. 1, a transistor inverter 11 is created by bridge-connecting a parallel circuit consisting of a transistor and a diode connected in antiparallel to the transistor.
These transistors are turned on and turned on in sequence at high speed.
By turning off the transistor inverter 1
1 directly applies this high frequency AC power to the primary side of the transformer 12, and from the secondary side of this, P is outputted AC power, but as mentioned above, this AC power The frequency of power is much higher than the commercial frequency, so the transformer 12 can be made much smaller and lighter than a transformer for commercial frequencies.

Reference numeral 15 is a rectifier for outputting a positive voltage, and reference numeral 16 is a rectifier for outputting a negative voltage. It is constructed by bridge-connecting an arm formed by a series diode connected to the transistor and a feedback diode connected in antiparallel to the transistor. These rectifiers 1
5 and 16 are separately excited converters which use the output voltage of the transistor inverter 11 as a commutation voltage, and by controlling the phase of the high frequency square wave output from the transistor inverter 11, the output voltage of the rectifiers 15 and 16 is The filter capacitor 17 removes harmonics and outputs an alternating current without waveform distortion to the output terminal 18.

In order to reduce the size of the transformer 12 and filter capacitor 17, increasing the output frequency of the transistor inverter 11 is an effective means. The turn-off time of the device becomes a problem. That is, since the load connected to the output terminal 18 is generally an inductive load and requires reactive current, the rectifiers 15 and 16 must be operated in the inverse conversion region, so the turn-off time of this semiconductor switching element is If the period is long, not only will the output frequency of the transistor inverter 11 not be sufficiently high as described above, but also the AC voltage applied to the output terminal 18 will not be sufficient.

In the embodiment of the present invention, a transistor is used as a high-speed operation semiconductor switching element, and since a large reverse voltage cannot be applied to this transistor, a series diode connected in series with the transistor shares this reverse voltage.

It goes without saying that a high-speed diode may be used as this series diode. In addition to transistors, self-extinguishing semiconductor switching elements such as gate turn-off thyristors can also be used as high-speed operation semiconductor switching elements, and in this case, the series diode can be used as is or can be omitted. .

As described above, since the rectifier 15 outputs a positive voltage and the rectifier 16 outputs a negative voltage, these rectifiers can alternately supply an alternating current voltage, that is, a positive half wave and a negative half wave. There are two ways to switch from a positive half-wave to a negative half-wave, or from a negative half-wave to a positive half-wave. The half-wave side is blocked, and the positive half-wave side is blocked during the period when the negative half-wave is output. However, since this method makes it difficult to supply reactive power to the load, it is used in conjunction with a method of detecting the direction of the output current and operating it.

The second method is to simultaneously operate the rectifier 15 for positive voltage output and the rectifier 16 for negative voltage output, and to cause a circulating current to flow between both rectifiers 15 and 16. The embodiment circuit shown in FIG. 1 is a case of this second method, and the above-mentioned circulating current is excessively caused by the rectifier 15 connected in series, the axle 13, and the rectifier 16 connected in series. It is suppressed so that it does not occur.

FIG. 2 is a main circuit connection diagram showing a second embodiment of the present invention, and the DC power supply 10 and transistor inverter 11 are the same as in FIG. 1. In this second embodiment, since the insulating transformer 22 has a center tap, the rectifier 25 that outputs a positive voltage and the rectifier 26 that outputs a negative voltage both have the number of arms. Since this can be reduced by half compared to the case shown in FIG. 1, the size, weight, and cost of the device can be reduced. Note that symbols 23 and 24 are circular '
r! It is a glue handle for suppressing the L flow, the reference numeral 27 is a filter reactor for removing harmonic components from the output, and the reference numeral 18 is an output terminal.

FIG. 3 is an operating waveform diagram showing the waveforms of each part in the embodiment circuit shown in FIG. 1, in which FIG. 1
5.16 output waveforms in FIG.

The high frequency square wave output by the snare transistor inverter 11 (see No. 31) is a double rectifier.

15. Phase control with 16 transistors Figure 3 (b)
), by removing harmonics of this with the filter capacitor 17, a sine wave without waveform distortion can be obtained (see third factor (c)).

Note that although the AC obtained in the example circuit shown in FIGS. 1 and 2 is single-phase, separately excited conversion is configured by combining a rectifier that outputs a positive voltage and a rectifier that outputs a negative voltage. Three-phase alternating current can be obtained by using three sets of transformers and three sets of transformers on the power supply side used for insulation purposes. Further, it is also possible to use only one set of insulation transformers and use three sets of separately excited converters to output three-phase alternating current.

Based on the present invention configured as described above, it is possible to operate the AC power supply as a rectifier by connecting the output terminal 18 of the AC power supply to another AC source, such as a commercial power system. Although it is possible.

In this case, the current waveform taken from the commercial power grid is a sine wave and can be rectified with very few harmonics. Note that such a rectifier can also omit a transformer located between the inverter and the separately excited converter.

〔Effect of the invention〕

According to this invention, direct current is converted into high frequency alternating current using an inverter;7. After insulating this high frequency AC with a transformer, it is supplied to a separately excited converter consisting of an antiparallel connection of rectifiers, and this separately excited converter controls the phase of the AC output from the inverter. I am trying to remove harmonics. Therefore, this AC power supply is isolated from the power source and can provide AC with little waveform distortion, but since the inverter's output frequency is sufficiently high, the isolation transformer and filter capacitor can be made smaller. Therefore, the AC power supply device can be small, lightweight, and low cost.

Furthermore, by connecting the output side of this AC power supply to another AC power system, it also has the advantage that it can be used as a rectifier with extremely low harmonics.

[Brief explanation of the drawing]

FIG. 1 is a main circuit connection diagram showing a first embodiment of the invention, FIG. 2 is a main circuit connection diagram showing a second embodiment of the invention, and FIG. 3 is a main circuit connection diagram showing a second embodiment of the invention. FIG. 3 is an operation waveform diagram showing waveforms of various parts in an example circuit. 10... DC power supply, 11... Transistor inverter, 12.22... Transformer, 13, 14, 23.24
...Reactor, 15.16, 25.26... Rectifier, 17.27... Filter capacitor, 18...
Output terminal. f3t'Hitosho no? -Mountain L7 叉1χninn-
4\4nFigure 2Figure 3

Claims (1)

[Claims] 1) A series circuit consisting of an inverter that converts direct current to alternating current, a transformer connected to the output side of this inverter, and a high-speed operating semiconductor switching element and a diode connected to the output side of this transformer. An AC power supply device comprising a separately excited converter configured by connecting two sets of rectifiers in antiparallel to each other, and a filter connected to the output side of the separately excited converter.