SK19172001A3 - Method for protecting power semiconductors of a power converter and converter implementing same - Google Patents

Abstract

The active clamping control method involves using at least one power interrupter connected to a clamping device with a voltage threshold, preferably connected between the power terminal and the control of interrupter. In this way the maintenance of maximum allowable voltage at the interrupter poles is ensured, by inhibiting the clamping function when the interrupter is off. The mechanism for maintaining the maximum allowable voltage includes an inhibition interrupter connected between the clamping device and the control of power interrupter. Independent claims are included for an active control device.

Description

14884

Method of protection of power converter semiconductors and power converter

Technical field

The invention relates to a method of protecting a power converter semiconductor and a power converter for carrying out the method.

BACKGROUND OF THE INVENTION

The electrical conversion devices (DC-AC, AC-DC, DC-DC and AC-AC) are equipped with controlled semiconductors in the field of power electronics, which have the function of electric switches. These include eg. bipolar transistors, thyristors, GTO tripping thyristors, MOSFETY-y, IGBT switching transistors and more. However, these semiconductors have certain limits regarding the maximum permissible terminal voltage. In certain situations, it is desirable to control the switch so that it at least partially leads (by closing it), while avoiding overvoltage at its terminals and consequently destroying it. Therefore, various safety circuits have been developed.

Damage concerns concern, for example, the power supply circuits of the driving electric motors (synchronous, asynchronous, direct current powered). These circuits are equipped with transducers, for example three-phase transducers connected to interrupters, in which the voltage load of the semiconductors in the switch function must be at least equal, but preferably several times higher than the DC voltage of the overhead contact line. Particularly suitable are semiconductors which can withstand two to three times the voltage of the overhead contact network.

In the case of high voltages, i. j. For DC contact voltages with values higher than 2000 V, it is desirable to use semiconductors with relatively high voltage resistance. In addition, these semiconductors must have a linear function as opposed to the two-level transistors. . Of these semiconductors, IGBTs whose voltage characteristics are still higher and reach up to 6.5 kV are the most suitable.

In the following description, we use the IGBT type switch as an example because they are components with a relatively high voltage load exceeding 2 kV, with bipolar transistors and MOSFETs being limited to a maximum voltage of approximately 1000 V.

In addition, IGBTs are very fast and easy to operate.

In case of lower voltage resistance of transistors, several switches (semiconductors) are connected in series. In this case, a voltage limitation system must be assigned to them. This is particularly the case when IGBTs are used in the circuit whose voltage resistance is relatively low (3.3 kV).

The operating principle of the active voltage limiting device is simple: the switch closes when the voltage at its terminals exceeds a predetermined value. For this reason, a threshold voltage circuit (Zener avalanche diodes, Transil, etc.) is included between the power terminal and the switch control.

Thus, the active voltage limiting device serves to protect the IGBT against transient overvoltage. When an overvoltage occurs, the device is activated by closing the IGBT, which then passes through its linear region. The threshold voltage from which the voltage limiting is activated is calculated so that the voltage at the IGBT terminals never exceeds the maximum allowable value. The voltage limiting circuit is located between the collector and the IGBT grid to produce the reaction as quickly as possible.

The threshold voltage circuit injects the control signal again when the voltage at the switch terminals exceeds a predefined value (eg 2000 V). The disadvantage is that this device reduces the maximum threshold voltage of the switch when the switch does not lead; when the switch is open.

• ·

When the voltage at the terminals of the IGBT-Active Voltage Limiting device exceeds 2.2 kV, the power switch turns ON and its voltage is maintained around

2.2 kV instead of 3.3 kV, which is the maximum permissible voltage.

In the case of an uncontrolled and thus open IGBT, the maximum voltage that the circuit formed by the IGBT and the active voltage limiting device can maintain is a set voltage limiter threshold that is less than the maximum allowable IGBT voltage. In the above example, the IGBT has a maximum allowable voltage of 3.3 kV, and an active voltage limiting device is set, whose threshold is set to 2.2 kV: this gives a device that cannot be controlled when closed above 2.2 kV.

JP-061639911 describes very generally a device which makes it possible to determine whether the voltage at the collecting electrode of MOSFET is higher than the voltage at the Zener diode built into the connected limiting circuit. This is probably a device that is designed for integrated circuits with relatively low voltage of several tens of volts.

SUMMARY OF THE INVENTION

The object of the invention is to protect a high-voltage power converter which allows the switches to maintain the maximum permissible voltage on their terminals when the voltage limiting system is used.

SUMMARY OF THE INVENTION The present invention provides a method of protecting a power switch in a power converter that is coupled to a voltage limiting device to a threshold level that maintains the maximum permissible voltage at the power switch terminals by blocking the voltage limiting function to a threshold level when the power switch is off. .

Maximum permissible voltage at the power switch terminals

In particular, it is secured by means of a blocking switch which is located between the voltage limiting device to the threshold value and the power switch control member.

According to a preferred embodiment, the same control member is used to control the interlock switch and the power switch.

The blocking switch control pulse leading edge is synchronized with the power switch control pulse leading edge and the falling edge of the blocking switch control pulse is delayed relative to the power switch control pulse leading edge. This delay is 50 to 500 gs, preferably about 200 gs.

The invention also relates to a power converter which is provided with at least one power switch connected to a voltage limiting device to a threshold level. This converter is also characterized in that it is furthermore provided with a blocking switch which is located between the voltage limiting device and the power switch control member.

The inverter is comprised of several power switches connected in series and these switches are connected to a voltage limiting device to a set voltage threshold.

These power switches are linear mode high voltage semiconductors, such as power IGBTs.

The interlock switch is located in series with the voltage limiting device and this set is connected between the collector and the power IGBT grid.

The blocking switch is a linear mode semiconductor, preferably an IGBT or a two-level transistor.

The interlock switch is controlled via the respective network by the same controller as the power switch or switches.

The present invention relates to the use of the above method of protecting the converter against overvoltage of the power switches in the circuit of the interrupter and voltage limiter.

..... · J; * · ₅ · '·· · .. ·:

Overview of the figures in the drawing.

The invention will be elucidated by a description with reference to the drawing, in which:

Fig. 1 - diagram of the principle of the device for active voltage limitation, resp. a threshold voltage circuit that is part of the power switch;

Fig. 2 is a diagram of the principle of carrying out the method according to the invention by means of an IGBT for blocking the active voltage limitation which is interposed between the threshold voltage circuit and the power IGBT control member;

Fig. 3 - pulse control shapes of the power IGBT and IGBT for voltage limiting;

Fig. 4 is a diagram of the principle of the voltage limiter blocking circuit;

Fig. 5 is a diagram of the complete circuit breaker and voltage limiter circuit.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is a diagram of the principle of a power switch equipped with a threshold voltage circuit. A second switch is included in the limiting loop to block the active voltage limitation. This switch must withstand high voltage and be fast. These characteristics correspond to the IGBT placed in a small box. In the following, it will be referred to as a switch or blocking IGBT.

The voltage of the switch shall be such that the system so constructed can absorb all or part of the maximum permissible power IGBT voltage in a static state. Taking as an example an IGBT that has a maximum allowable voltage of 3.3 kV and that is associated with an active voltage limiting device with a threshold of 2.2 kV, then the maximum allowable IGBT voltage must be at least 3.3-2.2 = 1.1 kV.

9 ·

From a plurality of IGBT lock control options, an option that is derived from the power IGBT control pulses has been selected, which allows the limiter lock function to be more transparent with respect to the control electronics. The IGBT block control strategy is described in FIG. 2. Care must be taken to ensure that the IGBT is closed before the power IGBT begins to operate in the linear region, both in the off and on states. When the control pulse of the power IGBT is complete, the voltage limitation continues for approximately 200 με.

The active voltage limiting device with its blocking circuit is applicable to all electrical conversion systems that may be subjected to commutation overvoltages (breaker, vibrator, DC rectifier, etc.).

The complete circuit diagram of the voltage limiter blocking circuit is shown in FIG. 4, in which V29 is interlocking with a maximum permissible voltage rating

IGBT

1,2 kV.

diode V34, resistors R11 and R2, and capacitor C1.

voltage threshold is 2.2 switch X14 and X13, diode kV, forms

The V22 to V1 pulses from the power as shown transmit them to the IGBT blocking.

X18 is lead to the power grid (IGBT circuit), XI is connected to its collector.

In the example described, the device is made by IGBT power switches.

it is a breaker in which V2, V3 are in series and two diodes (U2:

They come into the circuit

X20; The IGBT creates them so that the direct serial is shown positioned by 3 IGBTs

The IGBT connection of FIG. 2 and (through the wiring example application:

within

In FIG.

(Ul: Vl,

V1, V2) also connected in series.

blocking of active voltage limitation the voltage resistance of the breaker equals 3 times the maximum permissible voltage for each

IGBT, i.

x 3.3 kV = 9.9 kV.

Without the voltage limiter, the voltage value would be only 3 x 2.2 kV

6.6 kV, which is insufficient for a conventional 3 kV overhead contact network.

Claims (11)

Modified claims A method of protecting a power switch in a power converter, which is connected to a voltage limiting device for a threshold voltage that maintains the maximum permissible voltage at the terminals of the power switch by blocking the voltage limiting function to a threshold level when the power switch is off. Method according to claim 1, characterized in that maintaining the maximum permissible voltage at the terminals of the power switch is ensured by a blocking switch located between the voltage limiting device to the threshold level and the power switch control member. Method according to claim 1 or 2, characterized in that the control of the interlock switch and the power switch is performed by the same control member. Method according to claim 3, characterized in that the leading edge of the blocking pulse of the blocking switch is synchronized with the leading edge of the blocking pulse of the blocking switch, and that the falling edge of the blocking pulse of the blocking switch is delayed. Method according to claim 3, characterized in that the delay is 50 to 500 gs, preferably about 200 gs. 6. A power converter connected to a voltage limiting device, which is provided with at least one power switch, a power switch control member, a blocking switch located between the voltage limiting device to the threshold level and the power switch control member, said control member allowing to simultaneously control the power switch. switch and lock switch. 7. The transducer according to claim 6, wherein the transducer comprises a plurality of power switches connected in series, the switches being connected to a voltage limiting device to a threshold level. Converter according to claim 6 or 7, characterized in that the power switch (s) are high voltage semiconductors of the IGBT type, which operate in a linear mode. 9. The transducer according to claim 8, wherein the interlock switch is located in series with the voltage limiting device and the entire assembly is connected between the collector and the power IGBT grid. The transducer according to any one of claims 6 to 9, characterized in that the blocking switch is a semiconductor operating in a linear mode, preferably IGBT, or a two-level semiconductor. Use of a method according to any one of claims 1 to 5 or a converter according to any one of claims 6 to 11 for protection against overvoltage of power converters in the circuit of a circuit breaker and voltage limiter.