JPH02250626A - GTO thyristor arm - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a GTO thyristor arm formed by connecting a plurality of GTO thyristors in series.

(Prior Art) FIG. 3 is an example of a conventional GTO thyristor arm in which a plurality of GTO thyristors are connected in series.

Note that in this example, in order to simplify the explanation, the number of GTO thyristors (hereinafter simply referred to as GTO in some cases) is three.

In the GTO thyristor stack 100 shown in the same figure, 11
-13 are GTO121-23 voltage dividing resistors, 31-33 are snubber circuits, 311, 321, 331 are snubber capacitors, 312°322.332 are snubber diodes, 3
13, 323, and 333 are snubber resistors. Also, 41
42 represents an arm reactor, 42 represents a resistor, and 43 represents a diode.

Here, the snubber circuits 31 to 33 prevent overvoltage from occurring in the GTO when the GTO is turned off, and the voltage dividing resistors 21 to 23 are used to equalize static voltage sharing. Furthermore, the arm reactor 41 is necessary to suppress d i / d t when the GTO is turned on, and the series circuit of the resistor 42 and the diode 43 is required to suppress the d i /d t when the GTO is turned off. It is used to absorb energy.

Next, FIG. 4 shows the basic circuit of the GTO including the snubber circuit, and FIG. 5 shows the basic operation of the GTO at turn-off. In addition, in Fig. 4, the GT in Fig. 3 is
Although the OII and the corresponding snubber circuit 31 are shown, the basic operation described below is similar to that of other GT 012,1
3 and the snubber circuits 32 and 33 corresponding thereto are also the same.

That is, at time t1 in FIG. 5, the off-operation of GToll is started, and a reverse direction current ig is supplied to its gate, and this current ig increases thereafter. And G
At time t2 after the time (turn-off time) determined by Toll has elapsed, GToll is turned off and the current i becomes zero. However, even if the current 1r becomes zero, the current flowing in the circuit does not suddenly become zero, and is commutated to the snubber circuit 31 as a current is, charging the snubber capacitor 311 via the snubber diode 312.

At time t in FIG. 5, the voltage of the snubber capacitor 311 (in the figure, the anode-cathode voltage v of GTOII
(denoted as Ak) is the voltage vd of the power supply (not shown)
When the current is reaches , the current is begins to decrease and becomes zero at time t. During this time, snubber capacitor 311 is charged to voltage V o p.

Here, the voltage jump (ΔV(+)) of the snubber capacitor 311 is as follows.

C3: Capacity of snubber capacitor (pF) LID: Inductance of main circuit wiring (pH) ■T: GTO
The breaking current (A) is

By the way, when GTOs are connected in series, it is necessary to equalize the voltages applied to each element during turn-on and turn-off, similar to a normal thyristor (SCR). here,
In FIG. 3, each of the currents at turn-off of GTOII-13 connected in series i6.1-1-iT3. is
Shared voltage VT□~V of U~is3 and GTO11~13
T3 is shown in FIG.

In order to equalize the voltage applied to GTOII-13 during turn-off, it is sufficient if the turn-off time of each GTOII-13 is the same, but the turn-off time actually varies depending on the characteristics of each element.

For example, as shown in FIG. 6, at time t1, three GTol
Even if the arcs 1 to 13 start to be extinguished at the same time, GTOll will not be able to reach the time t.
, , GTO12 is at t,2, and GTO13 is at t,
Turn off at 23. In the case of such a series connection, the shared voltage vT□ of the GTOII turned off first is the highest, and the shared voltage V7 of the GTO13 turned off last is the lowest. This shared voltage difference ΔVT is as follows.

s Note that Δ is the maximum value of the turn-off time difference of GTOs connected in series.

Here, if ΔvT becomes too large, G is turned off early.
Since the shared voltage of TO increases, voltage duty and turn-off loss increase, it is necessary to keep this ΔVT within a certain tolerance value. In order to keep 67 guns within the allowable value, it is necessary to ensure the turn-off time difference Δtm is within the allowable value.
In other words, it is necessary to increase the capacitance of the snubber capacitor.

By the way, in a large capacity GTO of 4500 (V), 3000 (A) class, the turn-off time (tgq) is 20 to 30
It is about [μs]. From the above formula (2), I T = 3
000 (A), Cs = 6 [μF], then Δtm
= 1 [μs] and ΔVT = 500 (V). Follow me,
A tra= 2 (us) Te is ΔvT=100
It becomes 0 (V).

(Problem to be Solved by the Invention) From the above, when configuring an arm by connecting GTOs in series, it is important to keep the variation in turn-off time to about 1 [μs] regardless of the number of GTOs connected in series. This is necessary from the viewpoint of voltage responsibilities, etc. Here, if there are several GTOs connected in series.

It is possible to control the above variation to about 1 [μs], but if there are many series, it is possible to control the variation to <20 to 30 [μs] as described above
It is practically difficult to control all the variations in the turn-off time of large-capacity GTOs, which are in the range of approximately 1 μs, to within 1 μs.

For this reason, in the past, the practical limit was to limit the number of GTOs connected in series to a few; if the number was more than that, it would be necessary to take measures such as special selection of the elements, which would increase the element price.
In some cases, there were problems such as difficulty in connecting a large number of devices in series. Against this.

Although it is conceivable to increase the number of GTOs that can be connected in series by increasing the capacitance of the snubber capacitor, there is actually a limit to increasing the capacitor capacitance because the loss occurring in the snubber resistor increases.

In other words, various power converters in which multiple GTOs are connected in series to form an arm are required to have high voltage resistance.

Despite the demand for lower prices, there is currently no product that can meet this demand.

The present invention has been made to solve the above problems,
The objective is to create multiple GTOs at low cost without having to sort GTOs or increase capacitance.
An object of the present invention is to provide a GTO thyristor arm that enables series connection of TOs.

(Means for solving the problem) Conventionally, only a snubber circuit is connected to each GTO forming an arm, so the voltage difference between the GTOs in the arm is equal to the difference in turn-off time of all GTOs in the arm. It is decided. Therefore, in the present invention, the arm is divided into a plurality of unit blocks, a voltage clamp circuit is connected to each block, and the variation in the turn-off time of the GTO within each block is managed in the same manner as before, and the turn-off time between the blocks is It was decided that time dispersion would not be managed, or that it would be looser than that between GTOs within an arm.

(Operation) According to the present invention, since the turn-off time differs for each unit block, some blocks turn off early and some blocks turn off late. In this case, in the block that turned off early, current must continue to flow because there are other blocks that have not turned off yet, but this current flows to the voltage clamp circuit connected in parallel to the block that turned off early.

Since the voltage clamp circuit is configured to keep the voltage substantially constant even when the current flows, the voltage across the block that is turned off early is clamped to the voltage of the voltage clamp circuit. As a result, the GTOs within this block share this clamp voltage within a specified variation.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of this embodiment, and in the figure, 101 to 103 are unit blocks connected in series. These unit blocks 101 to 103 have the same configuration as the GTO thyristor stack 100 in FIG.
It is composed of a voltage dividing resistor and a snubber circuit. Note that in this example, the number of blocks is three, but
This number is not limited at all.

Voltage clamp circuits 201 to 203 are connected in parallel to these unit blocks 101 to 103, respectively. The configurations of these voltage clamp circuits 201 to 203 are all the same, and an example thereof is shown in voltage clamp circuit 20.
1, a diode 212, a capacitor 211 connected in series with the diode 212, and the diode 21
2 and a resistor 213 connected in parallel. Note that in the other voltage clamp circuits 202 and 203, 22
2 and 232 are diodes, 221 and 231 are capacitors, and 223 and 233 are resistors. Here, the resistor 213°223.233 is a discharge resistance of the capacitors 211, 221, 231, and the resistance is set so that the voltage of the capacitors 211, 221, 231 is kept almost constant even during the ON period of the unit blocks 101 to 103. The value is set sufficiently larger than the resistance value of the snubber resistors (snubber resistors (discharge resistors) 313, 323, 333 in FIG. 3) in the unit blocks 101 to 103.

Moreover, the plurality of GTOs in each block 101 to 103 are
At turn-off, care is taken to keep variations in turn-off time within a specified value within the same block so that overvoltage exceeding the allowable value does not occur in elements that turn off early due to variations in turn-off time. On the other hand, the variation in turn-off time of the GTO for each block 101 to 103 is a value corresponding to the clamp voltage difference between the voltage clamp circuits 201 to 203 of each block 101 to 103. This variation is caused by blocks 101 to 103.
It is allowed to be several times larger than the variation between GTOs within the GTO.

Next, the operation of this GTO thyristor arm when it is off will be explained with reference to FIG. 2. That is, when the off-operation starts at time t in the figure, the block 101 enters the off-operation at time t□, and the block voltage increases.

Further, the block 102 enters the off operation at time t2, and the block 103 enters the off operation at time t□, and the block voltage increases. These times t, t, are not the same due to variations in the turn-off times of the GTOs in each block 101 to 103, and in the figure, block 101 enters the off operation earliest, followed by blocks 102 and 103 in that order. It is assumed that

After the block 101 enters the off-operation, its voltage increases and reaches the voltage Vt of the capacitor 211 at one time t1□, so the voltage of the block 101 is clamped to this voltage VL. After time t11, the current flowing to block 101 is transferred to voltage clamp circuit 201 as current io.
Translocated to. Similarly, block 102 indicates time tzz
The clamp voltage VL is reached at .

Further, as shown in the figure, the block 103 enters the off operation at time t, and the block voltage increases, but at time t4
Since the combined value of the voltages of blocks 101 to 103 reaches the power supply voltage, the current ic decreases thereafter and becomes zero at time t5.

(Effects of the Invention) As described above, according to the present invention, a plurality of G
TO is a - unit block, and multiple unit blocks are connected in series, and a voltage clamp circuit is connected in parallel to each unit block, so the GT in the block
The variation in turn-off time of O requires the same variation management as in the past, but it is possible to tolerate a large variation in turn-off time between blocks.

In other words, even if the turn-off times vary widely, the turn-off times can be grouped into multiple groups.

A unit block can be configured for each group of turn-off times. As a result, it is not necessary to specially select the GTO, and the yield of use is greatly improved, and there is no need to increase the capacitance of the capacitor, so the cost can be significantly reduced.

In addition, in the past, there was a limit to the number of GTOs connected in series due to variations in turn-off time, but with the present invention, a large number of GTOs can be connected in series.
Because TO can be freely connected in series.

Various power converters that require high voltage can be easily realized.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a waveform diagram showing operation at turn-off, Fig. 3 is a circuit diagram showing the prior art, Fig. 4 is a basic circuit diagram of GTO, 5 is a waveform diagram showing the operation at turn-off in FIG. 4, and FIG. 6 is a waveform diagram showing the operation at turn-off in FIG. tH6 Figures 101-103...Unit blocks 201-203
...Voltage clamp circuit 211, 221, 231...
Capacitor 212, 222, 232...Diode 2
13.223,233...Resistance

Claims (1)

[Claims] A plurality of GTO thyristors each connected to a snubber circuit are connected in series to form a unit block, and a plurality of these unit blocks are connected in series, and each unit block is provided with a signal at both ends of the unit block when the GTO thyristor is turned off. A GTO thyristor arm characterized by having voltage clamp circuits connected in parallel to each other to clamp the voltage within an allowable value.