JPH0270258A - Protection circuit for switching element in power conversion device - Google Patents

Abstract

PURPOSE:To prevent the destruction of thyristor by connecting a snubber circuit in parallel to switching elements capable of self-extinction of arc connected in reverse-parallel to a thyristor and another snubber circuit connecting a parallel circuit of a resistance and a capacitor in series to a diode. CONSTITUTION:A power conversion device is formed in a bridge connection of a thyristor T-Y incapable of self-extinction of arc with a controllableelectric valve capable of self-extinction of arc, e.g., a switching element couple connecting a GTO thyristor in inverse parallel. Between the anode A and cathode K of the THY a snubber circuit connecting a resistance RS1 with a capacitor CS1 in series is connected in parallel. Another snubber circuit connected in parallel between the anode A and cathode K of the GTO connects a parallel circuit of a capacitor CS2 and a resist RS3 in series to a diode DS and conducts current directly. In ignition of arc for THY, the inflow of current from a snubber capacitor of the GTO to the THY can thereby be prevented, so that the destruction of THY can be prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a protection circuit for a switch element in a power converter, and more particularly to a snubber circuit for a switch element in a reversible converter configured by combining a self-excited converter and a separately excited converter.

[Conventional technology]

Figure 5 shows a reactive power compensated polyphase cycloconverter published as Japanese Patent Application Laid-Open No. 61-177167, namely an automatic converter (41 to 43) consisting of a self-extinguishable controllable electric valve (for example, a GTO thyristor) and a self-extinguishing controllable electric valve (41-43) A circuit showing the main circuit configuration of a three-phase power conversion device comprising a plurality of reversible bridge rectifiers connected in antiparallel with separately excited converters (11 to 13) consisting of controllable electric valves (for example, thyristors) that cannot be extinguished. It is a diagram. 51 to 53 are transformers, and 6 is a load. FIG. 6 is a circuit diagram in which the reversible bridge rectifier portion for one phase of the three-phase output power converter shown in FIG. 5 is extracted and redrawn. In the Cyrisk converter, when the Cyrisk is turned off, a high steep voltage is generated due to the inductance of the commutation retreat path, and this voltage is applied as a jump reverse voltage between the anode A and the cathode of the Cyrisk that has been turned off. If this jump reverse voltage exceeds the peak repeated reverse voltage of Cyrisk, Cyrisk will be destroyed. Therefore, in order to suppress the application of this sudden reverse voltage, a snubber circuit S having a resistor R3I and a capacitor C3I connected in series is generally connected between A- of each thyristor THY, as shown in FIG. On the other hand, in a converter using GTO Cyrisk, G
When the TO is turned off, the anode voltage rises rapidly, causing an excessive power loss in the turned-off GTO, and if this exceeds the allowable power value, the GTO is destroyed. Therefore, in order to suppress the rise of the anode voltage at turn-off and reduce the power loss that occurs at turn-off, a snubber circuit S consisting of a capacitor C32, a diode DS, and a resistor R32 is connected to A- of the GTO as shown in Figure 8. It is common practice to connect between Here, the operation of the GTO Cyrisk snubber circuit will be briefly explained. In FIG. 8, consider the case where the GTO is now turned off. At this time, just before turn-off,
The charge of capacitor C32 is C32→R32→GTO→C
Assume that it is discharged in a loop of 32 and becomes zero. Therefore, when the GTO is turned off, the current flowing through the GTO flows through a bypass circuit called Ds-+cS2, which controls the rise of the anode voltage of the GTO. The function of resistor R32 is to limit the discharge current of capacitor C32 when the GTO is turned off. The function of diode DS is to short circuit resistor R3 when GTO is turned off and capacitor C32 is charged. Please note that the main circuit connection diagrams in Figures 5 and 6 are simple, so
The above-mentioned snubber circuit portion, which is originally connected, is omitted.

[Problem to be solved by the invention]

By the way, in a circuit in which a thyristor and a GTO are connected in antiparallel as shown in FIG. 6, if the snubber circuit described above is provided for each of the thyristor and the GTO, the following problems will occur. Figure 9 shows the GT type of the reversible bridge rectifier shown in Figure 6.
It is a circuit diagram depicting an anti-parallel connection set (for example, a combination of Ul-X2) of O and Cyrisk, including a snubber circuit. The problem here is when the thyristor THY turns on, and when the thyristor constituting the passive converter turns on, a forward voltage is applied to the thyristor, and therefore the capacitors C31 and C32 of the snubber circuit also Cyrisk A- is charged to the interventricular pressure with the polarity shown in . When Cyrisk is turned on in this state, capacitor C3I
, C32 discharge current 11+l! flows. The discharge current i of capacitor C3I is C3I■→THY→
The current flows in a loop of R3I→C31e, and the current value is limited by the resistor R3I, so there is no problem. However, the discharge current i! of the capacitor C32! is C32
There is no element that limits the flowing current in the loop (E)-+THY-+DS→C32e, and a large discharge current flows instantaneously, and in some cases, the current flowing through Thyrisk THY exceeds the critical on-current increase rate and causes the thyristor to flow. There was a problem with destroying it. The present invention solves the above-mentioned problem and provides a protection circuit for a switching element in a power conversion device. Specifically, in a reversible bridge rectifier consisting of an anti-parallel connection of a thyristor and a GTO thyrisk, the present invention has an adverse effect on the thyristor side when the thyristor is turned on. It is an object of the present invention to provide a snubber circuit for GTO Sairisk that does not cause any adverse effects.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a power conversion device including a switch element pair configured by connecting a switch element that cannot self-extinguish and a switch element that can self-extinguish in antiparallel to each other. When using a circuit configuration in which a series connection circuit of a capacitor and a resistor is connected between the anode and cathode of the non-self-extinguishing switch element as a snubber circuit for a switch element that cannot self-extinguish, As a snubber circuit for the switch element, a circuit in which a diode is connected in series with a parallel connection circuit of a capacitor and a resistor is used as a snubber circuit for the self-extinguishing switch element, and a series connection circuit of a capacitor and a resistor is used as the snubber circuit for the self-extinguishing switch element. It is characterized by using a circuit connected between the anode and cathode of the switch element. Furthermore, in order to solve the above-mentioned problems, the present invention provides a power converter including a switch element pair configured by connecting a non-self-extinguishable switch element and a self-extinguishable switch element in antiparallel to each other. , when a circuit configuration in which a series connection circuit of a capacitor and a resistor is connected between the anode and cathode of the non-self-extinguishing switch element is used as a snubber circuit for the non-self-extinguishing switch element, self-extinguishing is possible. As a snubber circuit for a switch element capable of self-extinguishing, a circuit configuration is provided in which a circuit in which a parallel connection circuit of a diode and a resistor is connected in series to a parallel connection circuit of a capacitor and a diode is connected between the anode and cathode of the switch element capable of self-extinguishing. It is also characterized by the fact that it has been used.

[For use]

The reason why the discharge current of the snubber capacitor of the GTO thyristor connected in anti-parallel connection with the thyristor flows through the fired thyristor is that the snubber capacitor of the GTO thyristor is charged in the direction of the forward voltage of the thyristor. Therefore, the present invention connects a circuit so that the snubber capacitor of the GTO Thyrisk snubber is not charged in the forward voltage direction of the thyristor (in the reverse voltage direction of the GTO Thyrisk) without impairing the original snubber function.

【Example】

Next, embodiments of the present invention will be described in detail based on the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the figure, the snubber circuit of the GTO thyristor has a circuit configuration in which a capacitor C32 and a resistor R33 are connected in parallel, and a diode DS is further connected in series. Now, consider the case where GTO turns off. At this time,
In other words, just before turn-off, capacitor C32
The charge of is the resistor R3 connected in parallel to the capacitor C32.
Assume that it is discharged through 3 and becomes zero. When the GTO is turned off, the current flowing through the GTO flows through a bypass circuit called DS-4C32, suppressing the rise of the anode voltage of the GTO. The function of the resistor R33 is to transfer the charge stored in the capacitor C32 by turning off the GTO to the GTO.
The purpose is to discharge the battery to zero in preparation for the next turn-off. In this way, the protection function provided by the GTO snubber circuit of the present invention during GTO turn-off is no different from that of the conventional type. Next, consider the case where a thyristor connected in antiparallel to the GTO is turned off. In the conventional GTO snubber circuit shown in FIG. 8, the capacitor C32 is charged to the forward voltage of the thyristor through the resistor R32, and a large discharge current flows through the thyristor at the same time as the thyristor is turned off. By the way, in the first embodiment of the present invention shown in FIG. 1, the forward voltage of the thyristor (reverse voltage of the GTO) is
Therefore, in the present invention, capacitor C32 is only charged with the polarity shown in FIG. 1, and even if the thyristor is turned on, the charge on capacitor C32 is Since it is blocked by DS, it cannot flow through Cyrisk. In addition, as in the second embodiment shown in FIG.
It is clear that the problems of the present invention can be solved even if the order of the parallel circuit of 2 and the resistor R33 and the diode DS is changed. FIG. 3 is a circuit diagram showing a third embodiment of the present invention. In FIG. 3, the snubber circuit of the GTO Sirisk has a circuit configuration in which a capacitor C32 and a diode DS2 are connected in parallel, and a diode DSL and a resistor R32 are further connected in series. Now, consider the case where GTO turns off. At this time,
In other words, in series with turn-off, capacitor C32
The charge is C32 → R52 → G as in the conventional circuit shown in Figure 8.
Assume that the discharge occurs in a loop of TO→C32 and becomes zero. When the GTO is turned off, the current flowing through the GTO flows through a bypass circuit called DS1→C82, suppressing the rise of the anode voltage of the GTO. Next, let us consider the case where the SIRISK connected in anti-parallel with the GTO is turned off. As mentioned above, the conventional GTO shown in FIG.
In the snubber circuit, capacitor C32 is connected through resistor R32.
was charged to the forward voltage of the thyristor, and a large discharge current flowed through the thyristor at the same time as the thyristor was turned off. However, in the third embodiment of the present invention shown in FIG. 3, the thyristor THY
This is to prevent the capacitor C32 from being charged to a polarity opposite to that shown in FIG. 3 during a period when a forward voltage is applied to GTO, that is, a period when a reverse voltage is applied to GTO. Therefore, in the present invention, capacitor C32 is charged only to the polarity shown in FIG. No discharge current flows. In addition, as in the fourth embodiment shown in FIG.
It is clear that the problems of the present invention can be solved even if the order of the parallel circuit of 2 and the diode DS2 and the parallel circuit of the diode DSI and the resistor R32 is changed. Effects of the Invention According to the present invention, in a power conversion device including a switching element pair configured by connecting a GTO thyristor and a thyristor in antiparallel, the snubber circuit of the GTO thyristor is replaced with a diode in a parallel circuit of a capacitor and a resistor. A conventional snubber circuit can be used for the thyristor by using a circuit configuration in which the thyristors are connected in series, or by using a circuit configuration in which a parallel circuit of a diode and a resistor is connected in series with a parallel circuit of a capacitor and a diode. Without impairing the protection function of the GTO thyristor, the discharge current of the snubber capacitor of the GTO thyristor can be prevented from flowing into the thyristor when the thyristor is fired, and the thyristor can be prevented from being destroyed.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a first embodiment of the present invention, Fig. 2 is a circuit diagram showing a second embodiment of the invention, Fig. 3 is a circuit diagram showing a third embodiment of the invention, and Fig. 4 is a circuit diagram showing a third embodiment of the invention. is a circuit diagram showing a fourth embodiment of the present invention, FIG. 5 is a circuit diagram showing a configuration example of a power conversion device to which the present invention is implemented, and FIG. 6 is a main circuit connection for one phase shown in FIG. Fig. 7 is a circuit diagram showing a snubber circuit of a general thyristor, Fig. 8 is a circuit diagram showing a snubber circuit of a general GTO thyristor, Fig. 9 is a circuit diagram of anti-parallel connection of thyristors and GTO thyristors, It is. R3I~RS 3-------One resistance, C31, C32
...---Capacitor, DS, DS 1. DS 2
−−−−−−−−Diode. Ryozu Haya 5 Hiryo 3 Sword Helmet 4 Illustration 6

Claims (1)

[Scope of Claims] 1) A power conversion device including a switch element pair configured by connecting a switch element that cannot self-extinguish and a switch element that can self-extinguish in antiparallel to each other, When using a circuit configuration in which a series connection circuit of a capacitor and a resistor is connected between the anode and the cathode of the non-self-extinguishable switch element as a snubber circuit for the self-extinguishable switch element, A power conversion device characterized in that the snubber circuit uses a circuit configuration in which a circuit in which a diode is connected in series to a parallel connection circuit of a capacitor and a resistor is connected between an anode and a cathode of the self-extinguishing switch element. Protection circuit for switch elements. 2) In a power conversion device including a switch element pair configured by connecting a non-self-extinguishable switch element and a self-extinguishable switch element in antiparallel to each other, a snubber for the non-self-extinguishable switch element is provided. When using a circuit configuration in which a series connection circuit of a capacitor and a resistor is connected between the anode and cathode of the non-self-extinguishable switch element, the capacitor and the resistor are used as a snubber circuit for the self-extinguishable switch element. A power conversion device characterized in that a circuit configuration is used in which a circuit in which a parallel connection circuit of diodes and a resistor is directly connected to a parallel connection circuit of diodes is connected between an anode and a cathode of the self-extinguishing switch element. Protection circuit for switch elements.