JP2555621B2 - Inverter energy recovery circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy recovery circuit for an inverter, which recovers energy stored in a snubber circuit along with the on / off operation of a semiconductor switch element to a power supply side.

[Conventional technology]

FIG. 4 is a circuit diagram showing a conventional example of an inverter. In FIG. 4, a feedback diode 11 is provided in a gate turn-off thyristor (hereinafter abbreviated as GTO thyristor) 10 as a semiconductor switching element, and a GTO thyristor 2 is provided.
Since the feedback diode 21 is connected in antiparallel to 0, both of these GTO thyristors 10 and 20 are connected in series, and the DC power supply 2 is connected to both ends thereof. GTO like this
By connecting two or three sets of series circuits of thyristors in parallel to each other and connecting them to a DC power supply, an inverter for converting DC into single-phase AC or three-phase AC is constructed. In the figure, only the first phase is illustrated.

GTO thyristor 10 is turned on / off and at the same time G
By turning on and off the TO thyristor 20 in the opposite phase to this, it is possible to take out an alternating current from the coupling point of both GTO thyristors 10 and 20, but such a switching operation of the GTO thyristor 10 or 20. As a result, the stored energy of the wiring inductance of the circuit is applied as a voltage with an extremely high rate of change,
Since it may damage the GTO thyristor 10 or 20, the first capacitor 12 and the first diode 13 and the resistor
By connecting the snubber circuit composed of 14 in parallel to the GTO thyristor 10 and connecting the snubber circuit composed of the first capacitor 22, the first diode 23 and the resistor 24 in parallel to the GTO thyristor 20, the first capacitor 12 or This energy is stored in 22 to slow down the rate of change of the voltage applied to the GTO thyristors 10 and 20.

For example, when the GTO thyristor 10 is turned on and the GTO thyristor 20 is turned off, the energy of the wiring inductance flows into the first capacitor 22 via the first diode 23 and charges the first capacitor 22 with the polarity shown. GTO thyristor 10 closed at the next moment, and GTO thyristor
When 20 is closed, the electric charge accumulated in the first capacitor 22 is stored in the first capacitor 22 → resistor 24 → GTO thyristor 20 →
It discharges in the path of the first capacitor 22.

As described above, the first capacitors 12 and 22 repeat charging and discharging in conjunction with the switching operation of the GTO thyristors 10 and 20.
The stored energy of and 22 is dissipated as heat in resistors 14 and 24, respectively. Incidentally, reference numeral 3 in FIG.
Is a smoothing capacitor.

[Problems to be solved by the invention]

By controlling the inverter with the pulse width modulation method, it is possible to suppress the waveform distortion of the alternating current output by the inverter, and the control characteristics become good, so that such a pulse width modulation control inverter is widely used. However, in order to further improve the control characteristics, the switching frequency of semiconductor switching devices such as GTO thyristors that compose the inverter tends to become higher and higher.

When the switching frequency is increased in this way, the switching loss of the GTO thyristor itself also increases, but especially the loss generated in the snubber circuit increases significantly, and a large-capacity resistor is required to dissipate this loss as heat. In addition to the drawback that the device becomes large and expensive, such as requiring special measures to dissipate the generated heat, it also has the drawback of significantly reducing the efficiency of the device.

Therefore, an object of the present invention is to prevent waste of energy by collecting energy accumulated in the snubber circuit along with the switching operation of the semiconductor switching element forming the inverter to the power source side, and to prevent the device from becoming large. It is aimed at suppressing formality and price increase and improving efficiency.

[Means for solving problems]

In order to achieve the above-mentioned object, the energy recovery circuit of the present invention has an anti-parallel connection circuit of two sets of semiconductor switch elements and a feedback diode, which are connected in series to each other and connected between the positive and negative electrodes of a DC power supply, Turn on these semiconductor switch elements
In an inverter that converts direct current into alternating current by performing off operation, a series circuit of a first capacitor and a first diode is separately connected in parallel to each of the semiconductor switching elements, and a second capacitor, a second diode, and a second diode are connected. A series circuit with one reactor is separately connected in parallel to each of the first diodes, and a series circuit obtained by separately connecting a parallel circuit of another reactor and another diode to both ends of a third capacitor, It connects between the positive and negative poles of the DC power supply, and one end of the second capacitor belonging to the negative pole side semiconductor switch element is connected to the positive pole side terminal of the third capacitor via the third diode and belongs to the positive pole side semiconductor switch element. The second
One end of the capacitor is connected to the third diode via a fourth diode.
It shall be connected to the negative terminal of the capacitor.

[Action]

This invention transfers the energy stored in the capacitor of the snubber circuit to the second capacitor when the semiconductor switch element to which the snubber circuit belongs is closed.
When the semiconductor switch element is subsequently opened, the energy stored in the second capacitor is transferred to the third capacitor connected between the positive and negative electrodes of the DC power supply,
Further, by regenerating the energy transferred to the third capacitor to the DC power source, the energy stored in the snubber circuit due to the switching operation of the semiconductor switch element is regenerated to the DC power source without wasting it. .

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
As in the case of the conventional circuit of FIG. 4, the inverter portion shows only one phase.

In Fig. 1, GT as a semiconductor switch element
A feedback diode 11 is connected to each of the O thyristors 10 and 20.
And 21 are connected in anti-parallel, both GTO thyristors 10 and 2
It is the same as in the case of the conventional circuit shown in FIG. 4 that one phase of the inverter is formed by connecting a series connection of 0 and 0 between the positive and negative electrodes of the DC power supply 2. Furthermore, a series circuit of the first capacitor 12 and the first diode 13 is connected in parallel to the GTO thyristor 10, and a series circuit of the first capacitor 22 and the first diode 23 is connected to the GTO thyristor 2.
By connecting in parallel to 0, the energy of the wiring inductance when these GTO thyristors 10 and 20 perform a switching operation is stored in these first capacitors 12 or 22. The conventional example shown in FIG. It is the same as the case of the circuit.

In the present invention, the series circuit of the first reactor 15, the second diode 16, and the second capacitor 17 is the first diode.
In addition to being connected in parallel to 13, the series circuit of the first reactor 25, the second diode 26, and the second capacitor 27 is connected in parallel to the first diode 23. Further, a circuit configured by connecting a parallel circuit of the reactor 31 and the diode 32 and a parallel circuit of the reactor 34 and the diode 35 to both ends of the third capacitor 33 is connected between the positive and negative electrodes of the DC power supply 2, The negative electrode side terminal of this third capacitor and one end of the above-mentioned second capacitor 17 on the positive electrode side are connected via a series circuit of a fourth diode 18 and a resistor 19, and
The positive terminal of the third capacitor and one end of the second capacitor 27 on the negative side are connected via a series circuit of a third diode 28 and a resistor 29.

The operation of the embodiment circuit of the present invention configured as described above is as follows. That is, assuming that the GTO thyristor 10 on the positive electrode side is in the ON state and the GTO thyristor 20 on the negative electrode side is in the OFF state, the first capacitor on the negative electrode side is
22 is charged to the power source voltage E with the polarity shown. At this point, the GTO thyristor 10 turns off, and then the GTO thyristor 20 turns on.
The charge of the first capacitor 22 → first reactor 25 → second
Diode 26 → Second capacitor 27 → GTO thyristor 20 →
By vibrating circuit composed of the path of the first capacitor 22,
The current is transferred to the second capacitor 27, and the current I ₂₂ flowing at this time charges the second capacitor 27 with the polarity shown. Next, when the negative side GTO thyristor 20 is turned off again, the potential on the anode side of the GTO thyristor 20 approaches the potential of + E, so the charge accumulated in the second capacitor 27 becomes the third diode 28 → Resistor 29 → 3rd capacitor 33 →
The current I ₂₇ flowing in the path of the diode 35 moves to the third capacitor 33. The electric charge transferred to the third capacitor 33 in this way is finally the third capacitor 33 → reactor 31 → DC power supply 2 → reactor 34 → third capacitor 33.
It is recovered to the DC power supply 2 by the route of. Resistance here 29
Is inserted in order to prevent vibration of the circuit when the charge of the second capacitor 27 is transferred to the third capacitor 33, and is essentially unnecessary. The resistor 19 is also inserted for the same purpose. The GT on the positive side
The charges accumulated in the first capacitor 12 due to the operation of the O thyristor 10 are also recovered to the power supply by the same operation.

FIG. 2 is a time chart showing the operation of each part of the embodiment circuit shown in FIG. 1, and FIG. 2 (a) shows the change in voltage between the anode and cathode of the GTO thyristor 20 on the negative electrode side. 2 (b) shows the change of the voltage V ₂₂ of the first capacitor 22 on the negative side with a solid line, and the voltage V ₂₂ of the second capacitor 27.
₂₇ changes in a dotted line, the current second diagram (c) of flowing a change in current I ₂₂ flowing from the first capacitor 22 on the negative electrode side to the second capacitor 27 in solid lines, and from the second capacitor 27 to the third capacitor 33 Each change in I ₂₇ is indicated by a dotted line.

As is clear from FIG. 2, when the GTO thyristor 20 is turned on at the time T ₁ , the charge accumulated in the first capacitor 22 is transferred to the second capacitor 27, and the time T _{2 is} next. It can be seen that, when the GTO thyristor 20 is turned off, the charge is moving from the second capacitor 27 to the third capacitor 33.

FIG. 3 is a circuit diagram when the embodiment circuit shown in FIG. 1 is applied to a three-phase inverter.
Each of the second phase unit 200 and the third phase unit 300 has the same circuit configuration as that shown in FIG. 1, except that the DC power supply 2 and the reactors 31 and 34 and the diodes 32 and 35 are provided.
-For the circuit composed of the third capacitor 33, it is sufficient to provide one set in common for the three phases.

〔The invention's effect〕

According to the present invention, as the semiconductor switch element forming the inverter for converting direct current into alternating current is turned on / off, the charge is stored in the first capacitor of the snubber circuit attached to the semiconductor switch element. The circuit is configured so that the generated charge is moved to the second capacitor and further to the third capacitor in conjunction with the operation of the semiconductor switch element, and finally this energy is regenerated to the DC power supply. Therefore, even if the switching frequency of the semiconductor switching element becomes high, the loss generated therewith is not dissipated as heat and is entirely recovered by the power supply, so that no waste of energy is consumed, and therefore the size of the device is large. It is possible to avoid the consumption required for shaping and processing of the generated heat and to suppress the decrease in the efficiency of the device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a time chart showing the operation of each part of the embodiment circuit shown in FIG. 1, and FIG. 3 shows the embodiment circuit shown in FIG. It is a circuit diagram at the time of applying to a phase inverter. FIG. 4 is a circuit diagram showing a conventional example of an inverter. 2 ... DC power supply, 3 ... Smoothing capacitor, 10, 20 ... GTO thyristor as semiconductor switching element, 11, 21 ... Feedback diode, 12, 22 ... First capacitor, 13, 23 ... First diode , 14,19,24,29 ...... Resistance, 15,25 ...... First reactor, 16,26 ...... Second diode, 17,27 ...... Second capacitor, 18 ...... Fourth diode, 28 ...... 3 diodes, 31,34 …… reactors, 32, 35 …… diodes, 33…
… Third capacitor.

Claims (1)

(57) [Claims] 1. An anti-parallel connection circuit of two sets of semiconductor switching elements and a feedback diode is connected in series to each other and connected between the positive and negative electrodes of a DC power source, and these semiconductor switching elements are turned on and off. In an inverter that converts direct current into alternating current, a series circuit of a first capacitor and a first diode is separately connected in parallel to each of the semiconductor switch elements, and a second capacitor, a second diode, and a first reactor are connected in series. A circuit is separately connected in parallel to each of the first diodes, and a series circuit obtained by separately connecting a parallel circuit of another reactor and another diode to both ends of the third capacitor is a positive and negative electrode of the DC power supply. One end of the second capacitor connected to the negative side semiconductor switch element,
It connects with the positive electrode side terminal of the said 3rd capacitor via a 3rd diode, and connects one end of the said 2nd capacitor which belongs to a positive electrode side semiconductor switch element to the negative electrode side terminal of the said 3rd capacitor via a 4th diode. An energy recovery circuit for an inverter, which is characterized in that