JPH01222665A - Inverter device - Google Patents

Abstract

PURPOSE:To increase the capacity of an inverter device and to form the output voltage of the device in a sine wave by employing one of the inverters as that for generating a basic wave output, employing the remaining inverter as a high frequency output inverter, and combining the output voltages. CONSTITUTION:A large capacity inverter 1 outputs a basic wave, and its switching frequency is formed to be low. A high frequency inverter 2 is formed to have a small capacity, a high switching frequency and good controllability. The outputs of both the inverters 1 and 2 are connected to the primary side of insulating transformers 3-4, the secondary sides are connected in series or in parallel, and this connecting point is connected to a load 7. As a result, the output voltages of the inverters 1 and 2 are combined, and applied as an AC output 4 to the load 7. The control circuit 6 of the inverter 2 is composed of a sine wave generating circuit 61, a converter 62, a comparator 63, an amplifier 64 and a pattern producing circuit 65.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to a technique for improving the output voltage waveform of a voltage source inverter device using a semiconductor capable of controlling the firing angle.

(Prior Art) Conventionally, techniques for improving the output voltage waveform of a voltage source inverter device, that is, making it closer to a sine wave, have been known as, for example,
There is something described in "Inverter Circuit" published by Corona Publishing in September 1964. The first example is one in which the inverter has a multiplex configuration as shown in Figure 4, and the second example is one in which the inverter output is pulse width modulated (so-called PPWM control) as shown in Figure 6. . In FIG. 4, three inverter circuits IA are prepared, and each inverter circuit IA is connected in series to a load 7 on the secondary side via an insulating transformer 3A in series on the output side of each inverter circuit IA. As a result, the load 7 is given the voltage waveform shown in FIG.

In other words, the output waveform of each inverter IA is shown in Figure 5.
, ■, ■, or these voltage waveforms are synthesized to form ■, and it can be understood that the voltage waveform of ■ is closer to a sine waveform than the voltage waveforms ■, ■, and ■ of each inverter IA.

In FIG. 6, the semiconductor element of the inverter 2A is, for example, a plurality of thyristors connected in a bridge, and each thyristor is turned on and off at high frequency to obtain a voltage waveform as shown in FIG. Both FIG. 4 and FIG. 6 are techniques for removing high frequency voltage components.

(Problems to be Solved by the Invention) However, all of these circuits have the following drawbacks. In the case of the multiplex configuration of the inverter IA shown in FIG. 4, the number of switching operations is small, so a large capacity inverter can be constructed without worrying about switching loss, but on the other hand, in order to remove high frequencies, inverter circuits must be multiplexed. Therefore, it has the disadvantage of being complicated and large.

In the case of the inverter 2A shown in Fig. 6, since switching is performed at a high frequency, it is easy to remove high frequencies, but on the other hand, switching loss increases due to the high frequency.
It has the disadvantage that it is difficult to increase capacity.

An object of the present invention is to provide an inverter device that has a large capacity and can obtain an output voltage waveform closer to a sine wave.

[Structure of the Invention (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention includes at least one of the plurality of inverters being an inverter for outputting a fundamental wave,
This inverter device is characterized in that the remainder is an inverter for high-frequency output, and the output voltages of each inverter are combined by an isolation transformer and applied to a load.

(Function) With the above configuration, the capacitance becomes large and the output voltage waveform becomes a waveform close to a sine wave.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. The large-capacity inverter 1 shown in the figure is only for outputting a fundamental wave, and has a low switching frequency but a large capacity, and the high-frequency inverter 2 is Although the capacity is small, the control performance with high switching frequency is excellent. The output sides of a large-capacity inverter 1 and a high-frequency inverter 2 are connected to the primary sides of isolation transformers 3 and 4, respectively, their secondary sides are connected in series or in parallel, and this connection point is connected to a load 7. In this way, an AC output 5 obtained by combining the output voltages of the large-capacity inverter 1 and the high-frequency inverter 2 is applied to the load 7.

The large-capacity inverter 1 is driven by a known control circuit (not shown) and supplies most of the power sent out from the AC output 5. The high-frequency inverter 2 is used to correct the output voltage waveform of the large-capacity inverter 1 so that it approaches a sine wave.

The large-capacity inverter 1 is capable of producing a rectangular voltage waveform as shown in FIG. The control circuit 6 of the high frequency inverter 2 includes a sine wave generating circuit 61, a converter 62, a comparator (matching circuit) 63, an amplifier 64,
It is composed of a pattern generation circuit 65. The sine wave generating circuit 61 generates an ideal sine wave voltage waveform to be obtained as the AC output 5. The converter 62 is for taking in the voltage waveform of the current AC output 5 and converting it into a sine wave voltage waveform of an appropriate voltage level.

The comparator 63 compares the sine wave voltage waveform from the sine wave generating circuit 61 and the sine wave voltage waveform output from the converter 62, and outputs a minute deviation thereof. The amplifier 64 is for amplifying the output of the comparator 63, and the pattern generation circuit 65 is for inputting the output of the amplifier 64 to generate a drive signal for the high frequency inverter 2.

The operation of the inverter device configured as above will be explained with reference to FIG. 2. 2 shows a rectangular wave voltage waveform obtained on the secondary side of the converter 62 when only the output voltage waveform of the large-capacity inverter 1 is applied to the AC output 5.

This rectangular voltage waveform is generated by the sine wave generating circuit 6 shown in FIG.
1 and the comparator 63, and here the output of
The minute deviation shown in is extracted. The waveform shown in FIG. 2 is amplified through an amplifier 64 and applied to a pattern generation circuit 65. The pattern generation circuit 65 generates a waveform shown in FIG. 2, and transmits this as a control waveform to the high frequency inverter 2, thereby driving the high frequency inverter.

Here, the pattern generation circuit 65 is well known, and although it will not be described in detail here, it superimposes the high frequency carrier waveform and the waveform shown in FIG. 2 to create the waveform shown in FIG. is a diagram for explaining this.

In Figure 3, ■-1 shows a triangular waveform sequence a as a high-frequency carrier waveform, and as a result of superimposing the controlled signal on this, the intersecting timing is detected and the controlled signal as shown in Figure 3 ■-2 is obtained. A pulse train having a width corresponding to the signal can be created.

The high-frequency inverter 2 shown in Fig. 1 is driven with the control waveform shown in Fig. 2 (■), and the large-capacity inverter 1 is
By combining with the self-blade of the AC output 5, a sine waveform having the same shape as the sine wave generating circuit 61 can be obtained.

Here, the output capacitance of the high frequency inverter 2 has the waveform shown in Figure 2 (■), that is, the positive and negative states are repeated as shown in Figure 2 (■) within a half cycle (in the example shown, the positive and negative states are repeated three times and the negative state is twice). ), it is understood that only the positive/negative difference needs to be given as a voltage. Therefore, the capacity of the high-frequency inverter 2 may be smaller than that of the large-capacity inverter 1, and ideally it functions as a reactive power source that does not supply fundamental wave power.

In reality, there is an upper limit to the frequency of the carrier triangular wave illustrated in Figure 3, and on the other hand, the voltage drop that occurs when the load 7 is connected to the AC output 5 (not shown or the impedance of the cable, etc.) generates a sine wave. The high frequency inverter 2 also plays a role in power supply since it creates a difference with the circuit 61.

In the example shown in Fig. 1, the waveform of the high-capacity inverter 1 is a rectangular wave, but it is also possible to remove relatively low-order high-frequency voltage components in advance, and in that case, the capacity of the high-frequency inverter 2 can be further reduced. can.

According to the embodiment of the present invention described above, the basic waveform output voltage waveform of the large-capacity inverter 1 and the output voltage waveform of the high-frequency inverter 2 are coupled via the isolation transformers 3 and 4, respectively, so that the large-capacity This results in an output voltage that is more similar to a sine wave.

In the example of FIG. 1, two single-phase inverters are shown for the sake of simplicity, but it goes without saying that each inverter may be a plurality of inverters or may be a three-phase inverter.

[Effects of the Invention] According to the present invention described above, at least one of the plurality of inverters is used as an inverter for fundamental wave output, and the rest are used as inverters for high frequency output, and the output voltage of each inverter is Since the signals are combined using an isolation transformer and applied to the load, it is possible to provide an inverter device that has a large capacity and can obtain an output voltage waveform that is closer to a sine wave.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of an inverter device according to the present invention, FIGS. 2 and 3 are diagrams for explaining the operation of FIG. 1, and FIG. 4 is a circuit diagram showing an embodiment of an inverter device according to the present invention. A circuit diagram showing an example, FIG. 5 is a diagram for explaining the operation of FIG. 4, FIG. 6 is a circuit diagram showing a second example of a conventional inverter device, and FIG. 7 is a diagram for explaining the operation of FIG. 6. It is a figure for explaining. 1. Large capacity inverter, 2... High frequency inverter,
3, 4... Isolation transformer, 5... AC output, 6... Control circuit, 61... Sine wave generation circuit, 62... Converter,
63...Comparator, 64...Amplifier, 65...Pattern generation circuit, 7...Load. Applicant's agent Patent attorney Takehiko Suzue - CO - Figure 1 Figure 3

Claims (1)

[Claims] At least one of the multiple inverters is used as an inverter for fundamental wave output, and the rest are used as inverters for high frequency output, and the output voltages of each inverter are combined by an isolation transformer and this is applied to the load. An inverter device characterized by: