WO2019149346A1 - Method for switching off a power semiconductor component - Google Patents

Abstract

The invention relates to a method for switching off a switchable bipolar power semiconductor component (703). In the method, the gate emitter voltage (VGE) of the power semiconductor component (703) is reduced from a first voltage value (V1) to a second voltage value (V2) at a first average voltage change rate (dVGE_1/dt) starting in a first time period (t3-t4) in response to a switch-off signal. In a second time period (t4-t5), the gate emitter voltage (VGE) is then kept constant or is reduced to a third voltage value (V3), wherein the gate emitter voltage has a second average voltage change rate (dVGE_2/dt) in the second time period, and the value of the second average voltage change rate (dVGE_2/dt) is less than the value of the first average voltage change rate (dVGE_1/dt).

Description

description

Method for switching off a power semiconductor component

The invention relates to a method for switching off a bipolar switchable power semiconductor component and a drive circuit for a bipolar switchable

Power semiconductor component.

It has been found that it is advantageous to use bipolar switchable power semiconductor components, in particular

Insulated gate bipolar transistors to operate with comparatively large gate-emitter voltages. In the past, only 15 V gate-emitter voltages were used to drive the power semiconductor components. However, it has been shown that gate-emitter voltages greater than or equal to 18 V are advantageous, because in such

Gate-emitter voltages the forward losses of

Power semiconductor devices are reduced. However, the operation of power semiconductor devices with such high gate-emitter voltages poses difficulties: For example, when switched on by a

Power semiconductor component flowing electrical current short circuit occurs (so-called type 2 short circuit), then very high short-circuit currents can occur, which in

Extreme case, the power semiconductor device can destroy.

The invention is based on the object, a method for switching off a bipolar switchable

 Specify power semiconductor device and a drive circuit for a bipolar switchable power semiconductor device, with which even with the use of

Gate-emitter voltages greater than or equal to 18 V in the event of a short circuit, the power semiconductor device can be safely switched off. This object is achieved by a method and by a drive circuit according to the independent

Claims. Advantageous embodiments of the method and the drive circuit are in the dependent

Claims specified.

Disclosed is a method for switching off a bipolar switchable power semiconductor device, in which

 in response to a switch-off signal, the gate-emitter voltage of the power semiconductor component is reduced from a first voltage value in a first time segment with a first average voltage change rate up to a second voltage value,

 - then in a second period the

Gate-emitter voltage is kept constant or reduced to a third voltage value, wherein the

Gate-emitter voltage in the second period of time has a second mean voltage change rate, and the amount of the second average voltage change rate is smaller than the amount of the first middle

Voltage change rate, and

 - then in a third period the

Gate-emitter voltage with a third middle

Voltage change rate up to a fourth

Voltage value is reduced, wherein the amount of the third mean voltage change rate is greater than the amount of the second average voltage change rate. It is particularly advantageous that the gate-emitter voltage rapidly from the first

Voltage value is reduced to the second voltage value and then the gate-emitter voltage in the second

Period kept constant or only slightly reduced. This will accelerate desaturation of the

Power semiconductor device forced and allows a smooth transition to the third period in which the shutdown is terminated. The length of the second

Time period is chosen so that at the end of the second Thereafter, during the third time period, the gate-emitter voltage can be rapidly reduced to the fourth voltage value (the minimum value of the gate-emitter voltage). In this method, a rapid desaturation of the power semiconductor device takes place, so that the current peaks occurring during this desaturation are limited. This causes damage to the bipolar switchable

Power semiconductor device avoided.

The procedure may be such that the first voltage value is greater than or equal to 18V. By using a gate-emitter voltage greater than or equal to 18 V (in

switched state of the power semiconductor device) in particular low forward losses are achieved.

The method can also proceed in such a way that the second voltage value is less than 15 V and greater than the pinch-off voltage

 (Pinch-off voltage) of the power semiconductor device is. The choice of such a second voltage value leads to a particularly rapid desaturation of the

Power semiconductor device.

The method may be such that the magnitude of the second mean voltage change rate is at least a factor of 5 less than the amount of the first average voltage change rate.

The method may also be such that the magnitude of the second average voltage change rate is at least a factor of 5 less than the amount of the third average voltage change rate.

By the two variants of the method described above is advantageously achieved that the

Gate-emitter voltage during the second period is significantly less reduced than during the first time Time period or during the third time period. This contributes to a quick desaturation of the

Power semiconductor device at.

The method may also be such that the second average voltage change rate is between 0 and -1 V / ps, more preferably between -0.01 and -1 V / ps. This is a small second mean rate of voltage change. If the second average voltage change rate is zero, then the gate-emitter voltage remains constant in the second time period. The second period represents a waiting period.

The procedure can also be such that the second

Period between 1 and 20 ps, in particular between 3 and 10 ps, long. The second period is one

Waiting period, after which the

Gate-emitter voltage is reduced up to the fourth voltage value.

The method can also run such that the first voltage value corresponds to the gate-emitter voltage of the power semiconductor component in the switched-on state. In this switched-on state, the advantageous effects of the increased occur

Gate-emitter voltage, in particular the reduced forward losses of the power semiconductor device.

The method may also be such that the first voltage value is between 18 and 35 volts. It has been found that at such voltage values of the gate-emitter voltage a significant reduction of the forward losses of the

Power semiconductor device is present (compared to lower voltage values of the gate-emitter voltage).

The method may include a method for switching off a

Power semiconductor device of a module of a modular multilevel power converter, wherein the modular Multilevel power converter has a plurality of modules that form a series electrical connection, the modules each at least the power semiconductor device, a second power semiconductor device and an electrical

Have energy storage, the

Power semiconductor device and the second

 Power semiconductor device are arranged in a half-bridge circuit, or the modules each at least the

Power semiconductor device, a second

Power semiconductor device, a third

Power semiconductor device, a fourth

Power semiconductor component and an electrical

Have energy storage, the

Power semiconductor device, the second

Power semiconductor device, the third

Power semiconductor device and the fourth

 Power semiconductor device are arranged in a full bridge circuit. The method can thus be used advantageously in a modular multilevel power converter.

The method may also be configured such that the first voltage value is a positive voltage value, the fourth voltage value is a negative voltage value and the magnitude of the first voltage value is greater than the magnitude of the fourth voltage value. Due to this asymmetry (amount of the first voltage value is greater than the amount of the fourth

Voltage value) will be described advantageous

Effects, in particular the reduced forward losses of the power semiconductor device achieved.

The method may also be such that the bipolar switchable power semiconductor device is an insulated gate bipolar transistor.

Disclosed is still a drive circuit for a bipolar switchable power semiconductor device, the Outputting a gate-emitter voltage for the

Power semiconductor device is set up, wherein

 - The gate-emitter voltage of the power semiconductor device starting from a first voltage value in a first period of time with a first middle

Voltage change rate up to a second

Voltage drops,

 - then in a second period the

 Gate-emitter voltage remains constant or drops to a third voltage value, wherein the gate-emitter voltage in the second period of time, a second average

 Voltage change rate, and the magnitude of the second average voltage change rate is less than the magnitude of the first average

Voltage change rate, and

 - then in a third period the

Gate-emitter voltage with a third middle

Voltage change rate up to a fourth

Voltage value decreases, wherein the amount of the third average voltage change rate is greater than the amount of the second average voltage change rate.

This drive circuit may be configured such that the magnitude of the second mean voltage change rate is at least a factor of 5 smaller than the amount of the first average voltage change rate.

The drive circuit may be configured such that the magnitude of the second average voltage change rate is at least a factor of 5 less than the amount of the third average voltage change rate.

The drive circuit may also be configured such that the second average voltage change rate is between 0 and -1 V / ps, in particular between -0.01 and -1 V / ps. The drive circuit can also be designed such that the second time interval is between 1 and 20 ps, in particular between 3 and 10 ps.

The drive circuit may be configured such that the first voltage value of the gate-emitter voltage of

Power semiconductor device in the on state corresponds.

The drive circuit may also be designed such that the first voltage value is between 18 and 35 V.

The drive circuit may be configured such that the first voltage value is a positive voltage value, the fourth voltage value is a negative voltage value and the magnitude of the first voltage value is greater than the magnitude of the fourth voltage value.

The drive circuit can also be configured such that the second voltage value is less than 15 V and greater than the pinch-off voltage (pinch-off voltage) of the power semiconductor component.

The drive circuit may be configured such that the bipolar switchable power semiconductor component

Bipolar transistor with insulated gate electrode is.

Also disclosed is a power semiconductor unit with a bipolar switchable power semiconductor component, in particular with a bipolar transistor with isolated

Gate electrode, and with a drive circuit according to one of the variants described above.

Disclosed is still a module of a modular

Multilevel power converter with such a

Power semiconductor unit. The drive circuit, the power semiconductor unit and the module of the modular multilevel converter have

similar advantages as described above in connection with the method.

In the following the invention will be explained in more detail by means of exemplary embodiments. The same reference numbers refer to the same or equivalent elements. This is in

Figure 1 shows a first embodiment of a modular

 Multilevel power converter, in

Figure 2 shows a second embodiment of a modular

 Multilevel power converter, in

FIG. 3 shows an exemplary embodiment of a phase module branch of a modular multilevel converter, in FIG

FIG. 4 shows a section from the phase module branch of FIG. 3, in FIG

Figure 5 shows an embodiment of a module of a modular

 Multilevel power converter, in

Figure 6 shows another embodiment of a module of a modular multi-level power converter, in

Figure 7 shows an embodiment of a

 Power semiconductor unit with a

 Power semiconductor component and a

 Control circuit, in

8 shows an exemplary course of switching off the

 Power semiconductor device, and in

9 shows a detail of a further embodiment of a

Turn off the power semiconductor device shown.

In Figure 1, an embodiment of a modular

Multilevel power converter 1 shown in bridge circuit. This modular multilevel power converter 1 has a first AC power connection 4, a second AC power connection 6 and a third AC power connection 8. The first alternating current connection 4, the second alternating current connection 6 and the third alternating current connection 8 can be connected to a three-phase alternating current network.

The first AC connection 4 is electrically connected to a first phase module branch 12 and a second phase module branch 14. The first phase module branch 12 and the second

Phase module branch 14 form a first phase module 16 of the power converter 1. The end of the first phase module branch 12 facing away from the first AC connection 4 is electrically connected to a first DC voltage connection 18; the end of the second phase module branch 14 facing away from the first AC connection 4 is connected to a second one

 DC voltage terminal 20 electrically connected. The first DC voltage terminal 18 is a positive one

 DC-connection; the second DC voltage terminal 20 is a negative DC voltage terminal. Between the first DC voltage terminal 18 and the second

DC voltage terminal 20 is connected to a DC voltage Ud.

The second AC connection 6 is electrically connected to one end of a third phase module branch 22 and to one end of a fourth phase module branch 24. The third

Phase module branch 22 and the fourth phase module branch 24 form a second phase module 26. The third AC connection 8 is electrically connected to one end of a fifth phase module branch 28 and to one end of a sixth phase module branch 30. The fifth phase module branch 28 and the sixth phase module branch 30 form a third phase module 32. The second AC terminal 6 facing away from the end of the third phase module branch 22 and the third

AC connection 8 opposite end of the fifth

Phase module branches 2827 are connected to the first

DC voltage terminal 18 electrically connected. The end of the fourth phase module branch 24 facing away from the second AC connection 6 and the end of the sixth phase module branch 30 facing away from the third AC connection 8 are electrically connected to the second DC voltage connection 20. The first phase module branch 12, the third phase module branch 22 and the fifth phase module branch 28 form a positive side

Power converter part 38; the second phase module branch 14, the fourth phase module branch 23 and the sixth phase module branch 30 form a negative-side converter element 40.

Each phase module branch has a plurality of modules which are electrically connected in series, see also Figure 3. Such modules are also referred to as submodules. in the

Embodiment, each phase module branch n modules. The number of electrically connected in series by means of their galvanic power connections modules can be very different, at least two modules are connected in series, but it can also be, for example, 3, 50, 100 or more modules connected electrically in series.

From a control device (not shown) of the

Power converter 1 optical messages or optical signals via an optical communication link (for example, via an optical fiber) to the individual modules. For example, the control device sends to the individual modules in each case a desired value for the amount of the output voltage that is to provide the respective module.

FIG. 2 shows an exemplary embodiment of another modular multilevel converter 201. This modular multilevel power converter 201 has in addition to the three AC connections 4, 6 and 8 only the three

 Phase module branches 12, 22 and 28. The three phase module branches 12, 22 and 28 are connected in a delta connection. Such a modular multilevel power converter can

For example, be used for reactive power compensation. The first AC connection 4, the second

AC terminal 6 and the third AC terminal 8 are connectable to a three-phase AC mains.

FIG. 3 shows an exemplary embodiment of a phase module branch 301. The phase module branches illustrated in FIGS. 1 and 2 can be constructed like this phase module branch 301.

The phase module branch 301 has modules 304_1, 304_2 ... 304_n. These n modules are electrically connected in series. With the modules electrically connected in series is a

Coupling inductance 307 and a current measuring device 310. By means of the current measuring device 310 can be determined whether a short circuit has occurred and therefore an increased current flows as a short-circuit current through the phase module branch 301.

The phase module branch 301 has a first terminal 313 and a second terminal 316. The first terminal 313 is electrically connected to the current measuring device 310; the second terminal 316 is electrically connected to the coupling inductor 307. The first terminal 313 and the second terminal 316 may also be referred to as a first AC terminal 313 and a second AC terminal 316, because an AC voltage can be generated between the two AC terminals 313, 316 by means of the modules 304_1 to 304_n.

FIG. 4 shows a section of the phase module branch 301 of FIG. 3. The series circuit 401 shown in FIG. 4 has k modules 304_1 to 304_k, where k is smaller than n. The series circuit 401 has exactly those k modules of modular multilevel power converter, which are arranged spatially on a plane 403 of a converter tower. A converter tower usually has several levels (floors), so that a plurality of modules is arranged on a converter tower in several levels.

FIG. 5 shows an embodiment of a module 500 of the modular multilevel converter 1. This may, for example, be the module 304_1 of the phase module branch 301 (or else one of the other modules illustrated in FIG. 3 or 4). The module is configured as a half-bridge module 500. The module 500 has a first on and

switchable power semiconductor device 502 with a first antiparallel connected diode 504 (first freewheeling diode 504) on. Furthermore, the module 500 has a second power semiconductor component 506 that can be switched on and off with a second antiparallel-connected diode 508 (second

Freewheeling diode 508) and an electrical energy storage 510 in the form of an electrical capacitor 510. The first

Power semiconductor device 502 and the second

Power semiconductor device 506 are each as a

Bipolar transistor designed with insulated gate electrode. The first power semiconductor device 502 is electrically connected in series with the second power semiconductor device 506. At the connection point between the two

Power semiconductor devices 502 and 506, a first (galvanic) module connection 512 is arranged. At the connection of the second power semiconductor component 506, which lies opposite the connection point, a second (galvanic) module connection 515 is arranged. The second module connection 515 is furthermore connected to a first connection of the energy store 510; a second terminal of the energy storage 510 is electrically connected to the terminal of the first

Power semiconductor device 502 facing the connection point. The energy store 510 is thus electrically connected in parallel with the series circuit of the first

Power semiconductor device 502 and the second

Power semiconductor component 506. By appropriate

Triggering the first power semiconductor component 502 and the second power semiconductor component 506 can be achieved that between the first module connection 512 and the second module connection 515 either the voltage of

Energy storage 510 is output or no voltage is output (i.e., a zero voltage is output). By interaction of the modules of the individual phase module branches so the respective desired output voltage of the converter can be generated.

FIG. 6 shows a further exemplary embodiment of a module 600 of the modular multilevel converter. This module 600 can be, for example, the module 304_n (or also one of the other modules shown in FIG. 3 or 4). In addition to the first already known from Figure 5

Power semiconductor device 502, second

 Power semiconductor component 506, first freewheeling diode 504, second freewheeling diode 508 and energy storage 510, the module 600 shown in Figure 6 has a third

Power semiconductor device 602 with an antiparallel connected third freewheeling diode 604 and a fourth

Power semiconductor device 606 with a fourth

antiparallel freewheeling diode 608 on. The third power semiconductor device 602 and the fourth

Power semiconductor device 606 are each configured as an IGBT. In contrast to the circuit of FIG. 5, the second module connection 615 is not connected to the second one

Power semiconductor device 506 electrically connected, but with a midpoint of an electrical series circuit of the third power semiconductor device 602 and the fourth power semiconductor device 606th The module of FIG. 6 is a so-called full-bridge module 600. This full-bridge module 600 is characterized in that, with appropriate control of the four

 Power semiconductor devices between the first

Module connection 512 and the second module connection 615 selectively either the positive voltage of the energy storage device 510, the negative voltage of the energy storage device 510 or a voltage of zero (zero voltage) can be output. Thus, therefore, by means of the full-bridge module 600, the polarity of the output voltage can be reversed. A modular

Multilevel power converters can either have only half-bridge modules 500, only full-bridge modules 600 or also half-bridge modules 500 and full-bridge modules 600.

FIG. 7 shows by way of example a power semiconductor unit 700 which has a drive circuit 701 and a bipolar switchable power semiconductor component 703 which is electrically connected to the drive circuit. This

can be switched off power semiconductor device 703

preferably one of the power semiconductor components of a module of a modular multilevel power converter, this module can be configured either in half-bridge circuit (see Figure 5) or in full-bridge circuit (see Figure 6).

In the exemplary embodiment, the bipolar switchable power semiconductor component 703 is a

Insulated Gate Bipolar Transistor (IGBT) bipolar transistor 703. This transistor 703 has a collector terminal, an emitter terminal and a gate terminal. The emitter terminal is connected to the collector terminal by way of a freewheeling diode 706, wherein the anode of the freewheeling diode 706 is electrically connected to the emitter terminal and the cathode of the freewheeling diode 706 is electrically connected to the collector terminal. The emitter connection is with

Earth potential 709 connected. The gate terminal of the

Power semiconductor device 703 is connected to an output 712 of drive circuit 701. At this exit 712 the Drive circuit 701 may (in the embodiment)

Voltages between -15 V and + 35 V are output. Thus, the bipolar switchable power semiconductor device 703 can be applied with almost any gate-emitter voltage waveforms between -15V and + 35V. In other embodiments, the bipolar switchable power semiconductor device 703 may also be implemented differently, for example as a

Field effect transistor.

Via a first connection 715, the drive circuit 701 is supplied with a positive voltage (in the exemplary embodiment +15 V); via a second terminal 718 is the

Drive circuit 701 with a negative voltage (in

Embodiment -15 V) supplied. About a third

Terminal 721, the drive circuit 701 is supplied with a variable voltage (variable supply voltage, variable in the embodiment between +15 V and +35 V). Via a fourth terminal 725, the drive circuit 701 is supplied with a further voltage, which in the embodiment as

Clamp voltage (Vclamp) is called. The first terminal 715, the second terminal 718 and the third terminal 721 are each switchably connected via a resistor RGonl, RGon2, RGoffl, RGoff, SC or RGoff, soft to the output 712 of the drive circuit. In this case, each of the terminals 715, 718 and 721 can be connected to the output 712 or disconnected from the output 712 by means of at least one electronic switch Son1, Son2, Soffl, Soff, SC or Soff. The fourth terminal 725 is switchably connected via a diode Delamp to the output 712 of the drive circuit. In this case, the fourth connection 725 can be connected to the output 712 or disconnected from the output 712 by means of an electronic switch Sclamp. The electronic switches of the drive circuit 701 each have a field effect transistor. In addition, in the connection branch between the first terminal 715 and the output 712, a diode Dl is connected. The two branches with the electronic switches Sonl and Son2 are essentially switched on when the Power semiconductor device required. By means of the voltage applied to the third terminal 721 variable supply voltage is achieved that the gate-emitter voltage of

Power semiconductor device 703 in the stationary

switched-on state assumes the first voltage value VI> 18 V.

The branches with the electronic switches Soffl, Soff, SC, Soff, soft and Sclamp are switched off during the switch-off process of the

Power semiconductor device required.

 It is shown below how, by opening and closing the switches Soffl, Soff, SC, Soff, soft and Sclamp, the desired gate voltage for the bipolar switchable power semiconductor component 703 is generated at the output 712 of the drive circuit and thus the desired gate-emitter voltage for the

 Power semiconductor device 703 can be provided.

The drive circuit 701 thus has a gate driver with a multi-stage output stage. By this drive circuit, the gate terminal of the power semiconductor device is connected to different voltage levels. Switching on and off of the individual switches Sonl, Son2 and Soff1, Soff, SC, Soff, soft and Sclamp can be time-controlled or event-controlled. Of course, other embodiments are conceivable to produce the desired course of the gate-emitter voltage. For example, the gate voltage applied to the gate terminal can be generated by means of a pulse width modulation or a programmable voltage source. Furthermore, the production of such

 Gate-emitter voltage curve by charge or discharge of RC elements conceivable. Modules 500 and 600 of the modular multilevel power converter may include drive circuits 701 each associated with the power semiconductor devices of the modules. So the modules can

Power semiconductor units 700 have. FIG. 8 shows an exemplary sequence of the method for switching off the bipolar switchable

 Power semiconductor device 703 shown. Here, in the upper part of the diagram, the time course of

Gate-emitter voltage VGE shown, while in the lower part of the diagram, the timing of switching on and off of the electronic switches Soffl, Soff, soft, Sclamp and Soff, SC is represented by logic signals. The switching on and off of these electronic switches leads in conjunction with the applied to the drive circuit

Supply voltages to the illustrated course of

Gate-emitter voltage VGE.

At the time t = tl the electronic switches are brought into their initial position. In the initial state (t = t2), the gate-emitter voltage VGE has a first voltage value VI. The first voltage value VI corresponds to the gate-emitter voltage of the power semiconductor component 703 in the switched-on state. The first voltage value VI can be between 18 and 35 V; In the exemplary embodiment, the first voltage value is 20 V (Vl = 20 V). The first voltage value VI is the positive maximum voltage value of the gate-emitter voltage. The switches Soffl, Soff, soft, Sclamp and Soff, SC are switched off

(Initial position). The remaining switches Son1 and Son2 are not taken into consideration below; they are needed for switching on the power semiconductor component.

At the time t = t3 is by a not shown

Short-circuit detection device (for example, due to a measurement or estimation of the electric current passing through the phase module branch 301 and thus through the

Power semiconductor device 703 flows) detected the presence of a short circuit. These

Short-circuit detection device then generates a power-off semiconductor device 703 relating to the shutdown signal A and outputs this shutdown signal A. A detection of a short circuit by means of an estimate of current values is The power semiconductor component 703 is switched off on the basis of the switch-off signal A. For this purpose, first the switches Sclamp and Soff, SC are switched on

Gate emitter voltage VGE to fall.

In a first period (t3-t4) the

Gate-emitter voltage VGE with a first middle

Voltage change rate dVGE_l / dt reduced from the first voltage value VI to a second voltage value V2. The second voltage value V2 is less than 15 V (ie smaller than the conventional drive voltage of an IGBT). At the same time, the second voltage value V2 is greater than the so-called pinch-off voltage (pinch-off voltage) Vth of the IGBT. By turning on the electronic switch Soff, SC, the output 712 of the drive circuit 701 via the series resistor RGoff, SC with the negative voltage source (im

Embodiment -15 V) connected. This will be the

Gate-emitter voltage VGE relatively quickly reduced or lowered during the first period. The first mean voltage change rate dVGE_l / dt is thus

comparatively large. This can also be clearly seen in the graphic representation of FIG. At the time t = t4 (ie at the end of the first period of time), the gate-emitter voltage has reached the second voltage value V2. Then the electronic switch Soff, SC is turned off. As a result, the gate-emitter voltage remains almost constant during a subsequent second time period (t4-t5); the

 Gate-emitter voltage V3 at the end of the second time period at time t = t5 corresponds approximately to the gate-emitter voltage V2 at the beginning of the second time period at time t = t4. During this second period, rapid desaturation of the power semiconductor device occurs. The second

Period (t4-t5) thus represents a waiting period. During the second time period (t4-t5) is therefore waiting, until the power semiconductor device is desaturated.

Accordingly, this second time period is selected. At time t = t5 is the power semiconductor device

desaturated. Then, at time t = t5 (end of the second period), the electronic switch Soffl is turned on. As a result, in a third period (t5-t6) the

Gate-emitter voltage with a third middle

Voltage change rate dVGE_3 / dt decreases from the third voltage value V3 to a fourth voltage value V4. The fourth voltage value V4 corresponds to

Embodiment of the maximum negative

 Gate-emitter voltage, this is -15 V. During the third time interval t5-t6 there is a soft turn-off of the

Power semiconductor device instead; By "gentle" is meant here a slow turn-off in which only small overvoltages occur at the power semiconductor component At time t = t5 there is a smooth transition between the wait time section (t4-t5) and the slow turn-off of the power semiconductor device in the third time section

(t5-t6). Thus, the time of desaturation of the

Power semiconductor device (t5) at the same time the beginning of a very gentle off. At the time t = t6 (ie at the end of the third time period), the switch-off process is completed; the power semiconductor device is turned off. (Optionally, at the time t = t5, the two electronic switches Soffl and Soff, soft can also be switched on at the same time, enabling a faster shutdown.)

In the exemplary embodiment of FIG. 8, the magnitude of the second mean voltage change rate dVGE_2 / dt is smaller than the amount of the third middle one

 Voltage change speed dVGE_3 / dt and the amount of the third average voltage change rate is smaller than the amount of the first middle one

Voltage change rate dVGE_l / dt:

 and

Weiterhin gilt im Ausführungsbeispiel:

Furthermore, in the exemplary embodiment:

 | dVGE_2 / dt | <| dVGE_3 / dt | <| dVGE_l / dt |.

It can be seen in FIG. 8 that the magnitude of the second average voltage change rate dVGE_2 / dt

at least by a factor of 5 is smaller than the amount of the first average voltage change rate dVGE_l / dt and as the amount of the third middle

Voltage change speed dVGE_3 / dt.

The second mean voltage change rate dVGE_2 / dt can be between 0 and -1 V per ys, in particular also between -0.01 and -1 V per ys. In this case, the second section (t4-t5) can be between 1 and 20 y seconds long, in particular between 3 and 10 y seconds.

The first voltage value VI is a positive voltage value, the fourth voltage value V4 is a negative voltage value and the magnitude of the first voltage value | VI | is greater than the magnitude of the fourth voltage value | V4 | , In the exemplary embodiment, the magnitude of the first voltage value is 20 V and the magnitude of the fourth voltage value is 15 V. The greater the magnitude of the first

Voltage value is, the better the mentioned

advantageous properties of the switched-on

Power semiconductor device, in particular the minimized forward losses.

In the embodiment of Figure 8 is in the second

Period (t4-t5) kept the gate-emitter voltage almost constant. The second mean voltage change rate dVGE_2 / dt is approximately zero. In Figure 9 is a

Embodiment of a method shown in which the gate-emitter voltage in the second period (t4-t5) is slowly reduced.

FIG. 9 shows an exemplary embodiment of a method for switching off a power semiconductor component, wherein the gate-emitter voltage during the second

Time interval (t4-t5) is slowly reduced from the second voltage value V2 to a third voltage value V3 with a second average voltage change rate dVGE_2 / dt. In the exemplary embodiment, this reduction is almost linear, the second mean voltage change rate has a relatively low constant value. This slow change of the gate-emitter voltage VGE can be achieved by means of the drive circuit 701, for example, by slowly decreasing the voltage Vclamp linearly during the second time period. The gate-emitter voltage VGE does not need to be constant during the second time period (t4-t5). It is also possible that the gate-emitter voltage during the second time period is reduced comparatively less than during the first time period or during the third time period. The amount of the second average voltage change rate dVGE_2 / dt is thus smaller than the amount of the first middle

 Voltage change rate dVGE_l / dt and the amount of the third average voltage change speed dVGE_3 / dt. Even so, a quick desaturation of the

Achieved power semiconductor device.

A method has been described for switching off a bipolar switchable power semiconductor component and an associated one

Drive circuit for the power semiconductor device described. In particular, converter internal faults (short circuits) in modular multilevel converters can thus be switched off safely, even if the

Power semiconductor components of this modular

Multilevel power converters with an increased

 Gate-emitter voltage (VGE> 18 V) are operated. Namely, if such a modular multilevel power converter has an internal fault (for example, a flash over the modules of a plane of a power converter tower,

 "Floor overrun"), then occurs for several in the

Short circuit loop existing modules a so-called "failure Under load "(Short circuit type 2) .Interruption of such an error could cause high consequential damages, for example in the

Short circuit loop modules are destroyed. This error can be switched off by means of the described method and the drive circuit described, so that a threat to the power semiconductor components is reduced. The actual detection of the short circuit as such is done using established and known methods, such as

for example, by measuring the current flowing through the modules or by estimating this current.

In the method described, a rapid reduction in the value of the signal occurs immediately following the switch-off signal

Gate-emitter voltage. In this case, the gate-emitter voltage with a predetermined first middle

 Voltage change speed dVGE_l / dt rapidly reduced to the second voltage value V2. The magnitude of the average voltage change rates can be determined by the

Set control circuit according to Figure 7 by the size of the resistors RGoff, SC, RGoff, soft and RGoffl. The choice of voltage change rates has a controlled effect on the desaturation of the

Power semiconductor device 703 possible.

Particularly advantageous is the reduction of

Gate-emitter voltage on the switch-off signal A out by means of several different voltage change rates (slopes). This ensures fast desaturation of the power semiconductor device and therefore reduces the peak value of the short-circuit current. Each of the three voltage change rates can be customized

set by means of the resistors of the drive circuit 701 and / or the supply voltages. As a result, on the one hand, a quick and safe disconnection of the short-circuit current can be achieved, but at the same time a smooth transition between the waiting time section (t4-t5) and the third time section (t5-t6) the gentle final shutdown of the

Power semiconductor device.

The three different voltage change rates, each of which can be adjusted individually, allow good controllability of the turn-off method, and in particular a near-fluence transition between the desaturation of the power semiconductor device and the subsequent final turn-off of the power semiconductor device.

A method and a drive circuit have been described, with which a power semiconductor device can be switched off safely even if this is at a high

Gate-emitter voltage is operated above 18V and a

Short circuit occurs.

Claims

claims 1. Method for switching off a bipolar switchable Power semiconductor device (703), wherein  - In response to a switch-off signal, the gate-emitter voltage (VGE) of the power semiconductor component (703) from a first Voltage value (VI) starting in a first period (t3-t4) with a first middle  Voltage change rate (dVGE_l / dt) is reduced to a second voltage value (V2),  - Then in a second period (t4-t5) the Gate emitter voltage (VGE) is kept constant or reduced to a third voltage value (V3), wherein the Gate-emitter voltage in the second period of time a second mean voltage change rate (dVGE_2 / dt), and the amount of the second middle Voltage change rate (dVGE_2 / dt) is less than the amount of the first middle one  Voltage change rate (dVGE_l / dt), and  - Then in a third period (t5-t6) the Gate-emitter voltage with a third middle Voltage change rate (dVGE_3 / dt) is reduced to a fourth voltage value (V4), wherein the amount of the third average voltage change rate (dVGE_3 / dt) is greater than the magnitude of the second mean voltage change rate (dVGE_2 / dt). 2. The method according to claim 1, d a d u r c h e c e n c i n e s that  - the first voltage value (VI) is greater than or equal to 18 V. 3. The method according to claim 1 or 2, d a d u r c h e c e n c i n e s that  - The second voltage value (V2) is less than 15 V and greater than the pinch-off voltage of the power semiconductor device (703). 4. The method according to any one of the preceding claims, characterized in that  - the amount of the second middle  Voltage change rate (dVGE_2 / dt) is smaller by at least a factor of 5 than the amount of the first average voltage change rate (dVGE_l / dt). 5. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  - the amount of the second middle  Voltage change rate (dVGE_2 / dt) is smaller by at least a factor of 5 than the amount of the third mean voltage change rate (dVGE_3 / dt). 6. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  the second average rate of change of voltage (dVGE_2 / dt) is between 0 and -1 V / ps, in particular between -0.01 and -1 V / ps. 7. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  - The second period (t4-t5) between 1 and 20 ps, in particular between 3 and 10 ps, long. 8. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  - The first voltage value (VI) corresponds to the gate-emitter voltage of the power semiconductor device (703) in the on state. 9. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  - The first voltage value (V3) is between 18 V and 35 V. 10. The method according to any one of the preceding claims, characterized in that the method is a method for switching off a Power semiconductor device (502) of a module (500) of a modular multilevel power converter (1), wherein the modular multilevel power converter comprises a plurality of modules (500) forming a series electrical connection, the modules (500) at least the Power semiconductor device (502), a second Power semiconductor device (506) and an electrical energy storage device (510), wherein the Power semiconductor device (502) and the second Power semiconductor device (506) in one Half-bridge circuit are arranged, or the modules (600) each at least the power semiconductor device (502), a second power semiconductor device (506), a third Power semiconductor device (602), a fourth Power semiconductor device (606) and an electrical energy storage device (510), wherein the Power semiconductor device (502), the second Power semiconductor device (504), the third Power semiconductor device (602) and the fourth Power semiconductor device (606) in one Full bridge circuit are arranged. 11. The method according to any one of the preceding claims, d a d u r c h e c e n e c e s in that e  - the first voltage value is a positive voltage value (VI), the fourth voltage value is a negative voltage value (V4) and the magnitude of the first voltage value (VI) is greater than the magnitude of the fourth voltage value (V4). 12. The method according to any one of the preceding claims, d a d u r c h e c e n e c e s in that e  - The bipolar switchable power semiconductor device is an insulated gate bipolar transistor (703). 13. A drive circuit (701) for a bipolar switchable power semiconductor device (703), which is used to output a Gate-emitter voltage for the power semiconductor device (703) is arranged, wherein  the gate-emitter voltage (VGE) of the  Power semiconductor device (703) from a first Voltage value (VI) starting in a first period (t3-t4) with a first middle  Voltage change rate (dVGE_l / dt) drops to a second voltage value (V2),  - Then in a second period (t4-t5) the Gate emitter voltage (VGE) remains constant or drops to a third voltage value (V3), the  Gate-emitter voltage in the second period of time a second mean voltage change rate (dVGE_2 / dt), and the amount of the second middle Voltage change rate (dVGE_2 / dt) is less than the amount of the first middle one  Voltage change rate (dVGE_l / dt), and  - Then in a third period (t5-t6) the Gate-emitter voltage with a third middle Voltage change rate (dVGE_3 / dt) falls to a fourth voltage value (V4), wherein the amount of the third average voltage change rate (dVGE_3 / dt) is greater than the amount of the second middle Voltage change rate (dVGE_2 / dt). 14. A drive circuit according to claim 13, d a d u r c h e c e n c i n e s that  - the amount of the second middle  Voltage change rate (dVGE_2 / dt) is smaller by at least a factor of 5 than the amount of the first average voltage change rate (dVGE_l / dt). 15. A drive circuit according to claim 13 or 14, d a d u r c h e c e n c i n e s that  - the amount of the second middle Voltage change speed (dVGE_2 / dt) at least by the Factor 5 is smaller than the amount of the third average voltage change rate (dVGE_3 / dt). 16. The drive circuit according to claim 13, wherein:  the second average rate of change of voltage (dVGE_2 / dt) is between 0 and -1 V / ps, in particular between -0.01 and -1 V / ps. 17. The drive circuit according to claim 13, wherein:  - The second period (t4-t5) between 1 and 20 ps, in particular between 3 and 10 ps, long. 18. The drive circuit according to claim 13, wherein:  - The first voltage value (VI) corresponds to the gate-emitter voltage of the power semiconductor device (703) in the on state. 19. A drive circuit according to claim 13, wherein:  - the first voltage value (VI) is between 18 V and 35 V. 20. The drive circuit according to claim 13, wherein a  - the first voltage value is a positive voltage value (VI), the fourth voltage value is a negative voltage value (V4) and the magnitude of the first voltage value (VI) is greater than the magnitude of the fourth voltage value (V4). 21. The drive circuit according to claim 13, wherein:  - The second voltage value (V2) is less than 15 V and greater than the pinch-off voltage of the power semiconductor device (703). 22. A drive circuit according to one of claims 13 to 21, characterized in that - The bipolar switchable power semiconductor device is an insulated gate bipolar transistor (703). 23. Power semiconductor unit (700) with a bipolar switchable power semiconductor component (703), in particular with an insulated gate bipolar transistor, and with a drive circuit (701) according to one of claims 13 to 22. 24. Module (500, 600) of a modular multilevel power converter (1) with a power semiconductor unit (700) according to claim 23.