JPH01238465A - Control of inverter device - Google Patents

Abstract

PURPOSE:To miniaturize the title device and reduce the weight of the same, by synchronizing an igniting pulse for a rectifier and a second inverter with the igniting for a first inverter. CONSTITUTION:AC current is inputted from an AC power source 1 into the first inverter 10 of a first converting means through a thyristor rectifier 2, a smoothing reactor 3L and a smoothing capacitor 3C. The inputted DC is converted into high-frequency AC by a pulse width modulating control to supply it to the transistor rectifier 20 of a second converting means through an insulating transformer 4 and convert it into DC again. Further, the DC is inputted into the second inverted 30 of a third converting means to convert it into AC having predetermined voltage and frequency, and supply it to a load 7. According to this method, the first inverter 10, a transistor rectifier 20 and the second inverter 30 are operated by a synchronized igniting pulse, whereby short-circuit mode between respective transistors is eliminated and the jumping voltage of the transistor is restrained into a small value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling an inverter device that outputs alternating current that is isolated from a direct current power source.

[Conventional technology]

FIG. 5 is a main circuit connection diagram showing a conventional example of an inverter device that outputs alternating current that is isolated from a direct current power source.

In FIG. 5, the AC power supply with the symbol l is a commercial power supply in which voltage fluctuations and frequency fluctuations are allowed to some extent, and the AC from this AC power supply 1 is passed through the Cyrisk rectifier 2.
The smoothing reactor 3L and the smoothing capacitor 3C smooth the DC output from the thyristor rectifier 2 and provide it to the first inverter 10.

The first inverter 10 is a field effect transistor (hereinafter abbreviated as FET) as a semiconductor switching element.
It consists of a single-phase bridge connection of arms formed by a diode connected in antiparallel to this, and by turning each arm on and off sequentially,
The direct current input to the first inverter IO is converted into alternating current and supplied to the isolation transformer 4.The higher the frequency of the alternating current output from the first inverter 10, the more compact the isolation transformer 4 becomes. can do.

The alternating current that is isolated from the direct current side by the isolation transformer 4 is converted back into direct current by the diode rectifier 5 configured with a single-phase bridge connection of diodes, and the ripple contained in this direct current is smoothed by the smoothing reactor. After being absorbed and removed by a smoothing circuit composed of a smoothing capacitor 6L and a smoothing capacitor 6C, the second inverter 30 converts the current into alternating current again, and supplies this alternating current to the load 7.

Here, the second inverter 30 forms an arm with a FET as a semiconductor switching element and a diode connected in antiparallel to this FET, and this arm is connected in a single-phase bridge. By controlling these FETs to turn on and off, the AC voltage and frequency applied to the load 7 can be controlled to desired values.

[Problems to be Solved by the Invention] Incidentally, an inverter device configured with the conventional circuit shown in FIG. 5 and insulating the AC supplied to the load from the DC power supply side is Since the power source is converted to alternating current, then insulated, and then converted back to direct current, the second inverter outputs the desired alternating current, so it is necessary to smooth the output direct current of the diode rectifier 5 after insulation. For this purpose, a large capacity smoothing reactor of 6L is used.
Also, a smoothing capacitor 6C must be installed,
This has the disadvantage that the device becomes larger. Furthermore, it also has the disadvantage that it cannot be applied to an inverter device that outputs a pulse width modulated waveform with a varying output voltage cycle.

Therefore, the purpose of this invention is to eliminate the need for a circuit that smoothes the output of a rectifier that converts alternating current to direct current, which is isolated from a direct current power source, and to make the transformer for insulating the direct current power smaller, and to reduce the output voltage. It is assumed that the inverter device is controlled so that it can output a pulse width modulated waveform with a changing period.

[Means to solve the problem]

In order to achieve the above object, the control method of the present invention includes:
By bridge-connecting an arm formed by a semiconductor switch element and a diode connected antiparallel to it,
The first converting means, the second converting means, and the third converting means are configured separately, and the first converting means is arranged such that the operation of the upper arm and the lower arm are opposite to each other for each phase, and The direct current input to the first conversion means is converted into alternating current by applying an ignition pulse so that the overlapping period of operation between the phases changes in accordance with the output voltage, and the voltage difference for each half cycle of this alternating current is The magnetic flux is applied to the second converting means through an isolating transformer, which is adapted to determine the magnetic flux by the summation, and the second converting means converts the insulation by a firing pulse synchronized with the firing pulse to the first converting means. The AC input is converted to DC and the AC input is converted to DC. The third converting means converts the DC input into AC using a pulse width modulated firing pulse in synchronization with the firing pulse of the first converting means and outputs the converted AC.

[Effect]

The present invention provides a first
An insulating transformer is designed to determine the magnetic flux by the sum of the voltage differences for each half cycle of the alternating current output by the inverter. After insulating this alternating current, a rectifier that converts it to direct current is connected to a semiconductor switch element and an inverter. It is configured by a bridge connection of arms consisting of diodes connected in parallel, and the firing pulse to this semiconductor switching element as well as the firing pulse to the semiconductor switching element constituting the second inverter in the next stage is transmitted to the first inverter. By synchronizing the ignition pulse for the semiconductor switch elements of the inverter, the DC output from the rectifier can be supplied to the second inverter without smoothing, and the smoothing circuit for the rectifier DC output can be omitted. This is what I did.

〔Example〕

FIG. 1 is a main circuit connection diagram showing an embodiment of the present invention,
FIG. 2 is a time chart showing an example of the operation of each conversion means in the embodiment circuit shown in FIG. 1, and the content of the present invention will be described below with reference to FIG. 1 and FIG. 2.

In this FIG. 1, the AC power supply designated by reference numeral 1 is a commercial power supply in which voltage fluctuations and frequency fluctuations are allowed to some extent, and the AC from this AC m1ll is converted into constant voltage DC by a thyristor rectifier 2. A smoothing reactor 3L and a smoothing capacitor 3C smooth the direct current output from this Sirisk rectifier 2, and convert it into a first converter as a first conversion means.
The input to the inverter 10 is the same as in the conventional circuit described above in FIG.

The first inverter IO is constructed by connecting four FETs 11.12.13.14 as semiconductor switching elements in a single-phase bridge.
T 11.12.13.14 each have a separate diode connected in antiparallel. This first inverter 1
0 inputs the smoothed DC from the DC power supply, that is, the Sirisk rectifier 2, converts it into high frequency AC using pulse width modulation control, and applies it to the primary side of the isolation U transformer 4, so this isolation transformer Since it is possible to extract alternating current from the secondary side of the device 4, which is insulated from the direct current power supply side, this is supplied to a transistor rectifier 20 as a second converting means to convert it back into direct current.

This transistor rectifier 20 is constructed by connecting four transistors 21, 22, 23, 24 as semiconductor switching elements with diodes connected in antiparallel to each other in a single-phase bridge connection.
Converts the alternating current input to the
The signal is input to a second inverter 30 as a conversion means.

The second inverter 30 is also configured by connecting diodes in antiparallel to each of four F E 731.32.33.34 as semiconductor switching elements in a single-phase bridge connection. Converts the input DC to AC of the desired voltage and frequency and connects it to the load 7.
This load 7 is supplied with a thyristor rectifier 2.
It is possible to supply AC power that is isolated from the DC output. Here, the reference numeral 41 is an instrument transformer that detects the AC voltage output to the load 7, and the reference numeral 40 is the first inverter 1.
0 and the transistor rectifier 20 and the second inverter 3
This is a pulse distribution circuit that provides ignition pulses to 0 at appropriate timing.

Due to the function of this pulse distribution circuit 40, the inverter shown in FIG. 1 performs the operation shown in the time chart of FIG. 2. That is, FIG.
10 output voltage, Figure 2 (b) shows the magnetic flux of isolation transformer 4,
FIG. 2(c) shows the output voltage of the transistor rectifier 20, FIG. 2(d) shows the output voltage of the second inverter 30, and FIG.
E) shows the output current of the second inverter, and FIG.
2(G) shows the operation of the four transistors 21, 22, 23 and 24 that make up the transistor rectifier 20, and FIG. 2(H) shows the operation of the four FE transistors that make up the second inverter 30.
T 31.32.33. and 34 movements each.

As is clear from FIG. 2, the upper FET II and the lower FET constitute the first phase of the first inverter 10.
13, when one of them is on, the other is always off, so that both of them alternately turn on and off. Similarly, when one of the upper FET 12 and lower FET 14 that constitutes the second phase is on, the other is off, and they alternately turn on and off. Since the overlapping period between the operation and the second phase operation changes in accordance with the output voltage, this first inverter 10 operates at a pulse width modulated high frequency with a period in which the output voltage is zero. (See Figure 2 (a)).

The isolation transformer 4 is designed so that its magnetic flux is determined by the sum of the voltage differences every half cycle from the first inverter 10 (see FIG. 2 (b)), and the transistor rectifier 20 is Component transistor 21
．． The ignition pulses to 22.23 and 24 are synchronized depending on the polarity of the isolation transformer 4, in other words to the ignition pulses to FETs 11.12.13.14 constituting the first inverter 10. The on/off operations of these transistors 21, 22, 23, and 24 are given as follows.
Completed within the period when the first inverter lO is outputting voltage (see Figure 2 (v)), and then the second inverter
FET 31.32.33.3 comprising 30
The firing pulse to FET 4 is also synchronized with the firing pulse of FETs 11, 12, 13, and 14 that constitute the first inverter 10, and the voltage generation section of this second inverter 30 is the same as that of each transistor of the transistor rectifier 20. 21.22゜23
, 24 are provided with firing signals. This second inverter 30 is as shown in FIG.
FET31 and FET33 perform switching operation at the fundamental frequency, while FET32 and FET34 perform pulse width modulation operation.

Note that the snubber capacitor 51. shown in FIG.
Reference numeral 52 is a capacitor which is not required in principle when this inverter device operates, and may be omitted, but it is actually used as a snubber. Therefore, when the snubber capacitors 51 and 52 are connected, the DC voltage output from the thyristor rectifier 20 is maintained, resulting in a waveform different from that in FIG. 2(b).

This FIG. 2 (b) only depicts the voltage corresponding to the primary side voltage of the isolation transformer 4.

By operating the first inverter 10, the transistor rectifier 20, and the second inverter 30 while maintaining the above-mentioned relationship, the short circuit mode between the transistors of the transistor rectifier 20 around the first inverter 10 is eliminated.
Since the transistor of the transistor rectifier 20 is turned off after the second inverter 30 enters the freewheeling mode, it is possible to suppress the surge voltage of this transistor to a small value.

FIG. 3 is a time chart obtained by enlarging the period A in the embodiment time chart of FIG. 2, and FIG.
B) shows the output voltage of the transistor rectifier 20, FIG. 3C shows the output voltage of the second inverter 30, and FIG.
2.13.14 operation, FIG. 3 (e) shows the transistors 21.22.2 constituting the transistor rectifier 20.
3.24 operations, FIG.

As is clear from FIG. 3, each switch is τ between elements
,~τ,.

FIG. 4 is a time chart showing a second embodiment of the operation of each conversion means in the embodiment circuit shown in FIG. 1, and FIG. 4(a) corresponds to FIG. 3(a). ing.

However, since the illustration of the magnetic flux of the isolation transformer 4 is omitted,
Figure 4 (b), (c), (d).

(E), (F) and (G) are respectively shown in Figure 3 (C),
(d).

(E), (E), (G), and (J), so their explanations will be omitted.

In this FIG. 4, as shown in (G), FET31 and FET33 that constitute the second inverter 30 are
is operated by a firing pulse synchronized with the first inverter 10 or transistor rectifier 20, and the FE
T32 and FET34 perform pulse width modulation operation.

In short, as long as a ignition pulse for an inverter circuit that can configure a circulation mode is given and the inverter circuit is operated at °C, there are no restrictions on how the pulse width modulation waveform can be created. Furthermore, it goes without saying that the semiconductor switching elements constituting the first inverter IO, the second inverter 30, and the transistor rectifier 20 may be controllable elements.

〔Effect of the invention〕

According to this invention, after insulating the output of the first inverter that converts direct current to alternating current, the rectifier converts the output to direct current, and the second inverter converts the direct current back to alternating current and outputs the inverter. In the apparatus, a semiconductor switch forming the rectifier synchronizes the firing pulse to the rectifier and the second inverter with the firing pulse to the first inverter, and during a period when the first inverter is outputting voltage. Since the element completes its on/off operation and the second inverter is controlled to complete the voltage generation section while the ignition signal is given to this rectifier, a smoothing circuit is installed on the DC side of the rectifier. It is not necessary to provide the inverter device, and the inverter device can be made smaller and lighter. Furthermore, since the transformer determines the magnetic flux by the sum of the voltage differences every half cycle of the first inverter, it can be made smaller, and this inverter device can output a pulse width modulation waveform with a changing period. Furthermore, the processing of active power and reactive power during the output voltage generation period of the inverter device is
This is done by the inverter, the rectifier, the first inverter, and the DC power supply of the first inverter.The current during the period when no output voltage is generated is drained by the second inverter, so the first It also has the effect of suppressing the surge voltage when the inverter or rectifier performs a switching operation. Furthermore, by connecting a small-capacity capacitor as a snubber to the DC output side of the rectifier, it is possible to suppress the surge voltage caused by circuit vibration that occurs when driving the isolation transformer.

[Brief explanation of the drawing]

Fig. 1 is a main circuit connection diagram showing an embodiment of the present invention, Fig. 2 is a time chart showing an example of the operation of each conversion means in the embodiment circuit shown in Fig. 1, and Fig. 3 is a main circuit connection diagram showing an embodiment of the present invention. FIG. 4 is a time chart showing a second example of the operation of each conversion means in the example circuit shown in FIG. 1. , FIG. 5 is a main circuit connection diagram showing a conventional example of an inverter device that outputs alternating current that is isolated from a direct current power source. 1... AC power supply, 2... Thyristor rectifier, 3C. 6C... Smoothing capacitor, 3L, 6L... Smoothing reactor], 4... Isolation transformer, 5... Diode rectifier, 7... Load, 10... As first conversion means 1st inverter, 11.12.13.14... FET as a semiconductor switch element, 20... Transistor rectifier as second conversion means, 21.22.23.24
...Transistor as a semiconductor switch element, 30
...Second inverter as third conversion means, 31.3
2.33.34...FE as a semiconductor switch element
T, 40...Pulse distribution circuit, 73 Fig.

Claims (1)

[Claims] 1) By bridge-connecting an arm formed by a semiconductor switch element and a diode connected in antiparallel to the semiconductor switch element, the first conversion means, the second conversion means, and the third conversion means are configured separately, and the 1. The conversion means applies an ignition pulse so that the operation of the upper arm and the operation of the lower arm are opposite to each other for each phase, and the overlapping period of the operation between each phase changes in accordance with the output voltage. The direct current input to the first converting means is converted into alternating current, and the magnetic flux is determined by the sum of the voltage differences every half cycle of this alternating current. give to
The second converting means converts the insulated AC input into direct current and outputs it to the third converting means using an ignition pulse synchronized with the ignition pulse sent to the first converting means. A method for controlling an inverter device, characterized in that a DC input is converted into AC by a pulse width modulated firing pulse in synchronization with the firing pulse of the first conversion means, and outputted.