Dokumentenidentifikation |
EP0867999 10.01.2008 |
EP-Veröffentlichungsnummer |
0000867999 |
Titel |
Verfahren und Vorrichtung zum Erfassen und Behandeln von Kurzschlussphänomenen für Leistungshalbleiterelemente |
Anmelder |
ABB AB, Västerås, SE |
Erfinder |
Bijlenga, Bo, 730 50 Skultuna, SE; Lundberg, Peter, 722 23 Västeras, SE |
Vertreter |
derzeit kein Vertreter bestellt |
DE-Aktenzeichen |
69838771 |
Vertragsstaaten |
DE, FR, GB, IT, SE |
Sprache des Dokument |
EN |
EP-Anmeldetag |
28.02.1998 |
EP-Aktenzeichen |
981035538 |
EP-Offenlegungsdatum |
30.09.1998 |
EP date of grant |
28.11.2007 |
Veröffentlichungstag im Patentblatt |
10.01.2008 |
IPC-Hauptklasse |
H02H 7/12(2006.01)A, F, I, 20051017, B, H, EP
|
Beschreibung[en] |
FIELD OF THE INVENTION AND PRIOR ART
The present invention relates to a method for handling
a short-circuit situation occurring in a circuit having a plurality of power semiconductor
devices of turn-off type connected in series after detecting thereof and a device
for handling such a situation according to the preambles of appended claims 1 and
8, respectively.
Such circuits having power semiconductor devices connected
in series may for example be used in voltage-stiff converters in stations of plants
for transmitting electric power through High Voltage Direct Current (HVDC) or for
reactive power compensation (RPC) for converting direct voltage to alternating voltage
and conversely. These converters may in such plants typically have to hold voltages
within the range 10-500 kV, although also other voltages are conceivable, which
makes it possible to connect comparatively many such power semiconductor devices
in series so as to distribute the voltage among them, since they normally each may
only hold 1-5 kV. However, it is emphasized that the invention is not in any way
restricted to such so-called high voltage converter circuits, even though this special
application will be described hereinafter for illuminating the problem upon which
the present invention is based.
Examples of such power semiconductor devices of turn-off
type are turn-off thyristors (GTO), MOSFETs and IGBTs (Insulated Gate Bipolar Transistor),
wherein the latter ones are to prefer in many respects, since they combine a good
power handling ability with properties making them well suited for connection in
series in so-called IGBT valves in converters, since they may be turned on and turned
off simultaneously with a high accuracy.
Short-circuit situations may in rare cases occur in these
circuits, and it is then necessary to be able to handle these in such a way that
not entire IGBT valves break down. Such short-circuits may in said application arise
for example through any fault of the control apparatus controlling the power semiconductor
devices, which may mean that the so-called DC capacitor normally located on the
direct voltage side of said station is discharged, so that the short-circuit current
will flow through one of the phase legs of the converter. A phase leg is formed
by two IGBT valves such a converter has in the same direction. Another possibility
to short-circuit is that a short-circuit between a phase terminal and one of the
terminals of the DC capacitor occurs or that a short-circuit between two phase terminals
occurs, or that a ground fault occurs in a phase terminal and that the DC capacitor
is formed by two capacitors having a grounded midpoint.
If a short-circuit occurs in a phase leg provided with
IGBT valves the following happens: The individual IGBTs take such a voltage that
the short-circuit current is limited to a value being normally 3-10 higher than
the nominal current through the IGBT valves under normal operation. The IGBTs make
this thanks to a current-limiting IV characteristics thereof, just as other transistors.
During the current-limiting process the power semiconductor devices are exerted
to a very high power dissipation, which they may only stand during a very restricted
period of time, typically 10 µs.
Thus, when such a short-circuit occurs there is a desire
to be able to turn off the different power semiconductor devices as soon as possible
so as to prevent breakdown of any of them. However, there is a problem because of
variations of the drive units controlling each individual power semiconductor device,
which means differently fast turn-off, individual variations between the different
power semiconductor devices so that they take differently much voltage during the
current-limiting process and are turned off differently fast as well as other individual
variations therebetween, which results in considerable problems during the current-limiting
process as well as at turn-off when a short-circuit occurs. It is namely so that
during both the current-limiting process and during the turn-off process the entire
series connection of the power semiconductor devices has to take a certain voltage,
in which the voltage to be taken by a certain power semiconductor device may through
said variations be too high, while it may be considerably lower and completely acceptable
across other power semiconductor devices. This means a high risk of failure of any
power semiconductor device, this may for example happen when the voltage across
a power semiconductor device gets so high that the high field strength generated
thereacross leads to "avalanche", which means that nearly all power is concentrated
to a certain point. It is also possible that the high voltage in combination with
a high short-circuit current leads to a too hot power semiconductor device breaking
down as a consequence thereof.
A method and a device according to the introduction are
known through
DE 42 18 749 A
, which discloses a method for handling a short-circuit situation occurring
in a circuit having a plurality of power semiconductor devices of turn-off type
connected in series after detection thereof as well as a device for such handling
through which it is prevented that the voltage across an individual power semiconductor
device gets so high that the power semiconductor device arrives above the short-circuit
safe operating area for the given gate voltage when the power semiconductor device
is in current-limiting mode.
SUMMARY OF THE INVENTION
It is an object of the present invention to further improve
a method and device of the type defined in the introduction so as to among others
more reliably remain within said short-circuit safe operating area.
This object is according to the present invention obtained
with respect to the method by reducing the turn-off speed of each individual power
semiconductor device during the turn-off process when the voltage measured thereacross
increases. Such a retardation of the voltage increase of exactly that or those semiconductor
devices where this increase is the largest is in this way obtained, which results
in a good voltage division and that the instantaneous over-voltage at the turn-off
process is reduced and by that the power semiconductor device may be kept within
said short-circuit safe operation area.
According to a preferred embodiment of the invention when
the voltage measured between the two electrodes of an individual power semiconductor
device exceeds a predetermined value it is changed to turning the power semiconductor
device on by reversing the direction of said current supply to the gate of this
power semiconductor device with respect to the direction during turn-off. It may
by turning the power semiconductor device on again in this way be avoided that the
voltage across the electrodes thereof rises above the highest allowed level of an
individual power semiconductor device.
According to another preferred embodiment of the invention
when said short-circuit situation is detected during the turn-on process of an individual
power semiconductor device and this by that is in current limiting mode it is during
the turn-off process caused by said detection changed to turn the power semiconductor
device on when the voltage exceeds a said predetermined value being lower than the
upper limit for the short-circuit safe operating area of the power semiconductor
device. The advantages thereof appear from the above.
According to another preferred embodiment of the invention
for each individual power semiconductor device a leakage current is fed from the
gate with a substantially constant current intensity as long as the voltage measured
across the two electrodes of the power semiconductor device is below a predetermined
value, and when this value of the voltage is exceeded the intensity of the leakage
current is reduced for a slower turn-off of the power semiconductor device. It is
by this obtained that the voltage of each individual power semiconductor device
does not rise to levels being not permitted.
According to two preferred embodiments of the invention,
which are further developments of the embodiment last mentioned, said reduction
is achieved by a stepwise or a linear reduction of the intensity of the leakage
current when the voltage across the electrodes of the power semiconductor device
increases.
According to another preferred embodiment of the invention
when a short-circuit situation of one of the power semiconductor devices is detected,
said turn-off process for this individual power semiconductor device is immediately
started and a signal informing about said detection is sent to an apparatus in common
to the power semiconductor devices, whereupon this apparatus sends signals to all
the other power semiconductor devices connected in series to start turn-off processes
thereof being individually regulated. By this way immediately starting the turn-off
process for that power semiconductor device for which the short-circuit is firstly
detected the shortest possible reaction time is obtained, which reduces the stress
on the power semiconductor devices in the valve.
Preferred embodiments of the device according to the invention
make it possible to realise the preferred embodiments mentioned above of the method
according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
With reference to the appended drawings, below follows
a description of preferred embodiments of the invention cited as examples.
In the drawings:
- Fig 1
- is a simplified diagram illustrating a possible circuit having a plurality of
power semiconductor devices connected in series, on which the problems according
to the invention are applicable,
- Fig 2
- is a diagram illustrating how the voltage across the electrodes of an individual
power semiconductor device may be measured and how the power semiconductor device
may be controlled through a drive unit,
- Fig 3
- is a graph illustrating how a short-circuit may be detected according to a method
according to the invention,
- Fig 4
- is a graph illustrating a comparison of the development of the current through
a power semiconductor device after short-circuit on detecting a short-circuit according
to prior art and according to a method according to the present invention, and
- Fig 5
- is a graph illustrating how the turn-off process of an individual power semiconductor
device after detection of a short-circuit may be controlled depending upon the voltage
across the electrodes of the power semiconductor device according to a method according
to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
A phase leg of a high voltage converter circuit, on which
the present invention is applicable, is schematically shown in Fig 1. There are
normally three phase legs having a DC capacitor 3 in common in a plant connected
to a three-phase alternating voltage network. This comprises in a conventional way
a plurality of power semiconductor devices 1 connected in series, here in the form
of IGBTs, and a so-called free-wheeling diode 2 connected in anti-parallel with
each such device. The number of power semiconductor devices connected in series
is probably in practice considerably higher than shown in Fig 1. The series connection
of the power semiconductor devices is connected to a DC capacitor 3, while the phase
terminal 4 between the power semiconductor devices is connected to a phase reactor
5 to for example a phase of an alternating voltage network. The power semiconductor
devices with diodes arranged above the phase terminal 4 in Fig 1 form in this way
an IGBT valve and those located thereunder another IGBT valve, in which all power
semiconductor devices in an IGBT valve are turned on simultaneously through signals
from a drive unit 6 each schematically indicated, so that the power semiconductor
devices in the first IGBT valve are conducting when a positive potential is desired
at the phase terminal 4 and the power semiconductor devices in the second IGBT valve
are conducting when a negative potential is desired on the phase terminal 4. By
controlling the power semiconductor device according to a determined pulse width
modulation pattern (PWM) the direct voltage across the DC capacitor 3 may be used
for generating a voltage at the phase terminal 4, the fundamental component of which
is an alternating voltage having a desired amplitude, frequency and phase position.
Such controlling takes place by sending control pulses to the different drive units
from a control apparatus 7, which normally takes place through light conductors.
A short-circuit may in a converter circuit of this type occur as a consequence of
any of the defect situations discussed in the introduction, and it may here be repeated
that such a short-circuit may for example take place by a defect of the control
of the control apparatus 7, so that the DC capacitor 3 starts to be discharged,
in which the current goes in the same direction through all the IGBTs 1. The invention
aims at solving the problems arising in such situations in a satisfying way without
damaging any power semiconductor devices.
It is shown in Fig 2 how a drive unit 6 for an individual
power semiconductor device may connect positive current through a voltage-limited
current source 8 to the gate 9 of the power semiconductor device for turning the
power semiconductor device on or a negative current to the gate through a second
voltage-limited current source 10 for turning the power semiconductor device off.
The sources 8 and 10, respectively, may alternatively be two controlled voltage
sources in series with a resistor each, which limit the current at turning on and
turning off, respectively, to a value appropriate therefor. It is characterizing
for the invention that a voltage divider circuit 13 is connected between the collector
11 of the IGBT and the emitter 12 thereof, said circuit being a parallel connection
of a resistive and a capacitive voltage divider. Thus, this voltage divider circuit
is designed with a wide band width extending from 0 Hz to a frequency region being
high with respect to the typical switching frequency of the power semiconductor
device, preferably several MHz, so that it may rapidly detect quick transients.
It is so designed that a small proportion of the voltage across the collector 11
and the emitter 12 is measured through tapping at the point 14 and supplied to the
drive unit 6. By the knowledge of the magnitude of this proportion with respect
to the total voltage across the power semiconductor device the voltage last mentioned
may in this way be determined.
What is happening when a short-circuit situation occurs,
is detected and is handled will now be described with reference to Figs 3-5.
It is illustrated in Fig 3 how a short-circuit is detected
in a way according to the invention. The voltage UCE across the two main
electrodes of an individual power semiconductor device is shown as a function of
the time from the point of time 15 for sending a turn-on order from the control
apparatus 7 to the drive unit 6 of the power semiconductor device and further therefrom
to the sources 8 and 10 for connecting the former to the gate 9. During the starting
process of the turn-on process the power semiconductor device in question is in
current-limiting mode and it is important that the voltage thereacross is not increasing
to a value being above the upper limit for the safe operating area of the power
semiconductor device. A reference voltage value 16 changing with time being higher
than the maximum voltage level 17 across the electrodes at normal operation of the
power semiconductor device in a given moment is compared in a member 31 with the
voltage across the electrodes of the power semiconductor device determined by the
voltage divider circuit 13. When the power semiconductor device is turned on into
a short circuit the voltage so measured will not as normally is the case sink to
the low on-state voltage of the power semiconductor device, but it will continue
approximately according to the dashed dotted line 18 and exceed the reference voltage
value at a point of time 19. When this takes place a short-circuit is detected by
the drive unit 6 and this immediately starts a turn-off process for the power semiconductor
device in question by connecting the source 10 to the gate 9 and feed a negative
turn-off current to the gate. As indicated through the arrow 20, a signal informing
about said detection is simultaneously sent to the control apparatus 7, whereupon
this sends signals to all the other power semiconductor devices of the two current
valves to start turn-off processes regulated individually so as to turn all the
power semiconductor devices connected in series off. The lines 20 and 33 form preferably
a fibre optic communication between the drive unit and the control apparatus and
different codes may be used so as to indicate for example "short-circuit turn-off",
"turn-on" and so on. 32 indicates a point of time at which the prior art short-circuit
detecting device described above would detect a short-circuit existing.
It is illustrated in Fig 4 how the current 21 through the
power semiconductor device in question is developed over the time and how this reaches
a top value and after that decreases as of the point of time 19 when the turn-off
process is started. The graph 22 illustrates the development of the current at normal
turn-on of the power semiconductor device, while the graph 23 illustrates how the
current through the power semiconductor device would develop should the prior art
method discussed in the introduction be used for detecting the short-circuit and
the short-circuit be detected at the point of time 32, in which the typical current
integral value to which the power semiconductor device is exerted during the short-circuit
process may through the method according to the invention be a fraction of the case
according to the prior art method according to the graph 23. A current-limiting
level of the power semiconductor device is here also illustrated by the dashed line
34.
How a short-circuit occurring when a power semiconductor
device is turned on is detected by the increase of the voltage across the electrodes
of the power semiconductor device at 24 is also illustrated in Fig 3. 25 indicates
a point of time for sending a turn-off order to the power semiconductor device at
normal operation thereof.
It is illustrated in Fig 5 how the turn-off process according
to the invention is carried out for each individual power semiconductor device independently
of the rest of the power semiconductor devices. The negative turn-off current fed
to the gate 9 of the power semiconductor device at normal turn-off thereof is illustrated
through the dashed line 26. This current has preferably a comparatively high intensity,
so that the turn-off will be fast for obtaining low turn-off losses, which however
results in a comparatively high voltage overshoot which is not dramatic thanks to
the comparatively low current through the power semiconductor device. However, when
a short-circuit occurs it will not be possible to carry out a turn-off being just
as fast, but the negative turn-off current 27 fed to the gate of the power semiconductor
device has to have a lower intensity, since no high voltage overshoot may be accepted
as a consequence of the comparatively high short-circuit current flowing through
the power semiconductor device. The voltage across the electrodes of the individual
power semiconductor device is during the very turn-off process measured all the
time through the voltage divider circuit 13 and should this voltage exceed a certain
level 28, the turn-off speed will be reduced by reducing the intensity of the negative
current fed to the gate of the power semiconductor device. Two possible alternatives
to reduce the intensity of the turn-off current are indicated in Fig 5, a stepwise
one and a linear one. Should the voltage across the two electrodes of the power
semiconductor device exceed the predetermined value 29, which is below the upper
limit 30 of the short-circuit safe operation area of the power semiconductor device,
the direction of the feeding current to the gate of the power semiconductor device
will be reversed and it is turned on again so as to reduce the voltage across the
electrodes thereof to an acceptable value, whereupon the turn-off may be continued.
Through such an individual control of the turn-off process of each of the power
semiconductor devices connected in series differences of voltages thereacross may
be smoothed out and a good voltage distribution among them be obtained during the
entire turn-off process, so that it may be avoided that any of the power semiconductor
devices breaks down as a consequence of "avalanche" or too high heat generation
wherein. It is pointed out that the voltage level 28 should be chosen so that this
corresponds to the fact that the voltage across the power semiconductor device in
question exceeds the average voltage across the power semiconductor devices connected
in series by a certain margin, so that the turn-off process may be slowed down not
before the power semiconductor device in question has a voltage thereacross clearly
exceeding said average voltage. The stepwise method may be simplified and mean that
it is changed to zero voltage directly at 28.
The invention is of course not in any way restricted to
the preferred embodiment described above, but several possibilities to modifications
thereof, except from those already mentioned above, would be apparent to a man skilled
in the art without departing from the basic idea of the invention, such as this
is defined in the claims.
The high voltage converter circuit shown in Fig 1 is only
one conceivable application of the present invention, and many other circuits having
power semiconductor devices connected in series could benefit from the present invention
so as to handle short-circuit situations.
The term "short-circuit situation" is chosen to indicate
that the invention relates to problems arising in the power semiconductor devices
connected in series as a consequence of any short-circuit independently of where
it occurs.
|
Anspruch[de] |
Verfahren zum Handhaben einer Kurzschlusssituation, die in einem Schaltkreis
mit mehreren in Serie geschalteten Leistungshalbleiterbauelementen (1) vom Abschaltetyp
auftritt, nach einer Detektion derselben, bei dem die Spannung über beiden
Elektroden (11, 12) jedes einzelnen Leistungshalbleiterbauelements gemessen wird
und in Abhängigkeit von der Größe der Spannung ein Strom dem Gate
(9) des einzelnen Leistungshalbleiterbauelements geliefert wird oder von diesem
weggeführt wird, für eine individuelle Regelung des Abschalteprozesses,
der dadurch für jedes der Leistungshalbleiterbauelemente in Abhängigkeit
von der Spannung darüber erreicht wird,
dadurch gekennzeichnet, dass
die Abschaltegeschwindigkeit jedes einzelnen Leistungshalbleiterbauelements während
des Abschalteprozesses reduziert wird, wenn sich die darüber gemessene Spannung
erhöht.
Verfahren nach Anspruch 1,
dadurch gekennzeichnet, dass,
wenn die zwischen den beiden Elektroden eines einzelnen Leistungshalbleiterbauelements
gemessene Spannung einen vorbestimmten Wert (29) übersteigt, sie durch Umkehren
der Richtung der Stromzufuhr zu dem Gate (9) dieses Leistungshalbleiterbauelements
in Bezug auf die Richtung während des Abschaltens geändert wird, um das
Leistungshalbleiterbauelement anzuschalten.
Verfahren nach Anspruch 2,
dadurch gekennzeichnet, dass,
wenn die Kurzschlusssituation während des Anschalteprozesses eines einzelnen
Leistungshalbleiterbauelements detektiert wird und sich dieses dadurch in
einem Strombegrenzungsmodus befindet, sie während des durch die Detektion bewirkten
Abschalteprozesses geändert wird, um das Leistungshalbleiterbauelement anzuschalten,
wenn die Spannung einen vorbestimmten Wert (29) übersteigt, der niedriger als
die obere Grenze (30) für den sicheren Betriebsbereich bei Kurzschluss (SCSOA)
des Leistungshalbleiterbauelements ist.
Verfahren nach einem der Ansprüche 1-3,
dadurch gekennzeichnet, dass
für jedes einzelne Leistungshalbleiterbauelement (1) ein Reststrom von dem
Gate mit einer im Wesentlichen konstanten Stromstärke zugeführt wird,
solange die über den beiden Elektroden des Leistungshalbleiterbauelements gemessene
Spannung unter einem vorbestimmten Wert (28) liegt, und dass, wenn dieser Wert der
Spannung überstiegen wird, die Stärke des Reststroms für ein langsameres
Abschalten des Leistungshalbleiterbauelements reduziert wird.
Verfahren nach Anspruch 4,
dadurch gekennzeichnet, dass,
wenn der vorbestimmte Spannungswert (28), ab dem mit der Reduzierung der Stärke
des Reststroms begonnen wird, überstiegen wird, die Stärke dieses Reststroms
schrittweise reduziert wird, wenn bestimmte höhere Spannungswerte überschritten
werden.
Verfahren nach Anspruch 4,
dadurch gekennzeichnet, dass,
wenn der vorbestimmte Spannungswert (28), bei dem die Stärke des Reststroms
reduziert wird, überstiegen wird, eine Reduzierung der Stärke des Reststroms
durchgeführt wird, die im Wesentlichen linear zu dem Anstieg der Spannung über
den Elektroden des Leistungshalbleiterbauelements ist.
Verfahren nach einem der Ansprüche 1-6,
dadurch gekennzeichnet, dass,
wenn eine Kurzschlusssituation eines der Leistungshalbleiterbauelemente detektiert
wird, der Abschalteprozess für dieses einzelne Leistungshalbleiterbauelement
sofort gestartet wird und ein Signal, das über die Detektion informiert, an
eine Vorrichtung (7) gesendet wird, die den Leistungshalbleiterbauelementen gemein
ist, woraufhin diese Vorrichtung Signale an alle anderen Leistungshalbleiterbauelemente
sendet, die in Serie geschaltet sind, um Abschalteprozesse dieser zu starten, die
individuell geregelt sind.
Einrichtung zum Handhaben einer Kurzschlusssituation, die in einem Schaltkreis
mit mehreren in Serie geschalteten Leistungshalbleiterbauelementen (1) vom Abschaltetyp
auftritt, nach einer Detektion dieser, wobei die Einrichtung Bauteile (13), die
geeignet sind, um die Spannung über den beiden Elektroden (11, 12) jedes einzelnen
Leistungshalbleiterbauelements zu messen, ein Mittel (8, 10), das geeignet ist,
um unabhängig zu oder von dem Gate (9) jedes einzelnen Leistungshalbleiterbauelements
Strom zuzuführen, um dessen Leitung zu regeln, und Bauteile (6), die geeignet
sind, um eine Information über die Spannung zu empfangen und nach einer Detektion
eines Kurzschlusses das Mittel zur individuellen Regelung des dadurch verursachten
Abschaltprozesses für jedes der Leistungshalbleiterbauelemente zu steuern,
dadurch gekennzeichnet, dass
das Steuerbauteil (6) geeignet ist, um das Zufuhrmittel zu steuern, um für
jedes einzelne Leistungshalbleiterbauelement während des Abschalteprozesses
die Abschaltegeschwindigkeit zu reduzieren, wenn sich die hierüber gemessene
Spannung erhöht.
Einrichtung nach Anspruch 8,
dadurch gekennzeichnet, dass
sie Bauteile (31) umfasst, die geeignet sind, um die über jedem einzelnen Leistungshalbleiterbauelement
(1) gemessene Spannung mit dem Leistungshalbleiterbauelement zugehörigen Referenzspannungswerten
zu vergleichen und eine Information über diesen Vergleich zum individuellen
Steuern des Abschalteprozesses jedes Leistungshalbleiterbauelements an das Steuerbauteil
(6) zu senden.
Einrichtung nach Anspruch 9,
dadurch gekennzeichnet, dass,
wenn die Spannung über den beiden Elektroden (11, 12) eines einzelnen Leistungshalbleiterbauelements
einen vorbestimmten Referenzwert (29) übersteigt, die Steuerbauteile (6) geeignet
sind, um das Zufuhrmittel zu steuern, um einen Übergang zum Anschalten des
Leistungshalbleiterbauelements zu bewirken, indem die Richtung des dem Gate (9)
dieses Leistungshalbleiterbauelements zugeführten Stroms in Bezug auf die Richtung
beim Abschalten umgekehrt wird.
Einrichtung nach einem der Ansprüche 8 - 10,
dadurch gekennzeichnet, dass
die Bauteile zum Messen der Spannung über den beiden Elektroden jedes einzelnen
Leistungshalbleiterbauelements einen Spannungsteiler (13) umfassen, der parallel
zu dem jeweiligen Leistungshalbleiterbauelement geschaltet ist und geeignet ist,
um zum Ermitteln der tatsächlichen Spannung einen bestimmten Anteil der Spannung
zu messen.
Einrichtung nach Anspruch 11,
dadurch gekennzeichnet, dass
der Spannungsteiler (13) eine große Bandbreite aufweist, die sich von 0 Hz
zu einem Frequenzbereich erstreckt, der in Bezug auf die typischen Schaltfrequenzen
des Leistungshalbleiterbauelements hoch ist.
|
Anspruch[en] |
A method for handling a short-circuit situation occurring in a circuit
having a plurality of power semiconductor devices (1) of turn-off type connected
in series after detection thereof, in which the voltage across both electrodes (11,
12) of each individual power semiconductor device is measured and a current is supplied
to or fed away from the gate (9) of the individual power semiconductor device depending
upon the magnitude of said voltage for individual regulation of the turn-off process
achieved thereby for each of the power semiconductor devices depending upon said
voltage thereacross,
characterized in that the turn-off speed of each individual power semiconductor
device is reduced during the turn-off process when the voltage measured thereacross
increases.
A method according to claim 1,
characterized in that when the voltage measured between the two electrodes
of an individual power semiconductor device exceeds a predetermined value (29) it
is changed to turning the power semiconductor device on by reversing the direction
of said current supply to the gate (9) of this power semiconductor device with respect
to the direction during turn-off.
A method according to claim 2,
characterized in that when said short-circuit situation is detected during
the turn-on process of an individual power semiconductor device and this by that
is in current limiting mode it is during the turn-off process caused by said detection
changed to turn the power semiconductor device on when the voltage exceeds a said
predetermined value (29) being lower than the upper limit (30) for the short-circuit
safe operating area (SCSOA) of the power semiconductor device.
A method according to any of claims 1-3,
characterized in that for each individual power semiconductor device
(1) a leakage current is fed from the gate with a substantially constant current
intensity as long as the voltage measured across the two electrodes of the power
semiconductor device is below a predetermined value (28), and when this value of
the voltage is exceeded the intensity of the leakage current is reduced for a slower
turn-off of the power semiconductor device.
A method according to claim 4,
characterized in that, when said predetermined voltage value (28), as
of which the reduction of the intensity of the leakage current is started, is exceeded,
the intensity of this leakage current is reduced stepwise when determined higher
voltage values are passed.
A method according to claim 4,
characterized in that, when said predetermined voltage value (28), as
of which the intensity of the leakage current is reduced, is exceeded, a reduction
of the intensity of the leakage current being substantially linear to the rise of
the voltage across the electrodes of the power semiconductor device is carried out.
A method according to any of claims 1-6,
characterized in that, when a short-circuit situation of one of the power
semiconductor devices is detected, said turn-off process for this individual power
semiconductor device is immediately started and a signal informing about said detection
is sent to an apparatus (7) in common to the power semiconductor devices, whereupon
this apparatus sends signals to all the other power semiconductor devices connected
in series to start turn-off processes thereof being individually regulated.
A device for handling a short-circuit situation occurring in a circuit
having a plurality of power semiconductor devices (1) of turn-off type connected
in series after detection thereof, said device comprising members (13) adapted to
measure the voltage across the two electrodes (11, 12) of each individual power
semiconductor device, means (8, 10) adapted to independently feed current to or
from the gate (9) of each individual power semiconductor device for individually
regulating the conduction thereof and members (6) adapted to receive information
about said voltage and after a detection of a short-circuit control said means for
individually regulating the turn-off process caused thereby for each of the power
semiconductor devices,
characterized in that said control member (6) is adapted to control the
feeding means to reduce the turn-off speed for each individual power semiconductor
device during the turn-off process, when the voltage measured thereacross increased.
A device according to claim 8,
characterized in that it comprises members (31) adapted to compare the
voltage measured across each individual power semiconductor device (1) with reference
voltage values associated with the power semiconductor device and send information
about this comparison to said control member (6) for individually controlling the
turn-off process of each power semiconductor device.
A device according to claim 9,
characterized in that, when the voltage across the two electrodes (11,
12) of an individual power semiconductor device exceeds a predetermined reference
value (29), said control members (6) are adapted to control the feeding means to
cause a transition to turn on of the power semiconductor device by reversing the
direction of the current fed to the gate (9) of this power semiconductor device
with respect to the direction at turn-off.
A device according to any of claims 8-10,
characterized in that said members for measuring the voltage across the
two electrodes of each individual power semiconductor device comprise a voltage
divider (13) connected in parallel with the respective power semiconductor device
and adapted to measure a certain proportion of said voltage for determining the
real voltage.
A device according to claim 11,
characterized in that said voltage divider (13) has a large band width
extending from 0 Hz to a frequency region being high with respect to the typical
switching frequencies of the power semiconductor device.
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Anspruch[fr] |
Procédé pour traiter une situation de court-circuit survenant
dans un circuit ayant une pluralité de dispositifs à semi-conducteurs
de puissance (1) de type à mise hors tension montés en série après
la détection de celle-ci, dans lequel la tension à travers les deux électrodes
(11, 12) de chaque dispositif à semi-conducteurs de puissance individuel est
mesurée et un courant est délivré à la grille (9) du dispositif
à semi-conducteurs de puissance individuel ou depuis celle-ci en fonction de
la grandeur de ladite tension pour une régulation individuelle du processus
de mise hors tension ainsi obtenu pour chacun des dispositifs à semi-conducteurs
de puissance en fonction de ladite tension à travers ceux-ci, caractérisé
en ce que la vitesse de mise hors tension de chaque dispositif à semi-conducteurs
de puissance individuel est réduite pendant le processus de mise hors tension
lorsque la tension mesurée à travers ceux-ci augmente.
Procédé selon la revendication 1, caractérisé
en ce que lorsque la tension mesurée entre les deux électrodes d'un
dispositif à semi-conducteurs de puissance individuel dépasse une valeur
prédéterminée (29), elle est changée pour mettre sous tension
le dispositif à semi-conducteurs de puissance en inversant la direction dudit
courant délivré à la grille (9) de ce dispositif à semi-conducteurs
de puissance par rapport à la direction pendant la mise hors tension.
Procédé selon la revendication 2, caractérisé
en ce que lorsque ladite situation de court-circuit est détectée pendant
le processus de mise sous tension d'un dispositif à semi-conducteurs de puissance
individuel et que la raison de ceci est un mode de limitation de courant, c'est
pendant le processus de mise hors tension provoqué par ladite détection
changée pour mettre sous tension le dispositif à semi-conducteurs de puissance
lorsque la tension dépasse ladite valeur prédéterminée (29)
étant inférieure à la limite supérieure (30) pour la zone opérationnelle
de sécurité de court-circuit (SCSOA) du dispositif à semi-conducteurs
de puissance.
Procédé selon l'une quelconque des revendications 1 à
3, caractérisé en ce que pour chaque dispositif à semi-conducteurs
de puissance individuel (1) un courant de fuite est délivré depuis la
grille avec une intensité de courant sensiblement constante tant que la tension
mesurée à travers les deux électrodes du dispositif à semi-conducteurs
de puissance est au-dessous d'une valeur prédéterminée (28), et lorsque
cette valeur de la tension est dépassée l'intensité du courant de
fuite est réduite pour une mise hors tension plus lente du dispositif à
semi-conducteurs de puissance.
Procédé selon la revendication 4, caractérisé
en ce que, lorsque ladite valeur de tension prédéterminée (28),
depuis laquelle la réduction de l'intensité du courant de fuite est lancée,
est dépassée, l'intensité de ce courant de fuite est réduite
pas-à-pas lorsque des valeurs de tension supérieure déterminées
sont transmises.
Procédé selon la revendication 4, caractérisé
en ce que, lorsque ladite valeur de tension prédéterminée (28),
depuis laquelle l'intensité du courant de fuite est réduite, est dépassée,
une réduction de l'intensité du courant de fuite étant sensiblement
linéaire à l'augmentation de la tension à travers les électrodes
du dispositif à semi-conducteurs de puissance est effectuée.
Procédé selon l'une quelconque des revendications 1 à
6, caractérisé en ce que, lorsqu'une situation de court-circuit
de l'un des dispositifs à semi-conducteurs de puissance est détectée,
ledit processus de mise hors tension pour ce dispositif à semi-conducteurs
de puissance individuel est immédiatement lancé et un signal informant
de ladite détection est envoyé à un dispositif (7) en commun avec
les dispositifs à semi-conducteurs de puissance, après quoi ce dispositif
envoie des signaux à tous les autres dispositifs à semi-conducteurs de
puissance montés en série pour lancer des processus de mise hors tension
de ceux-ci étant individuellement régulés.
Dispositif pour traiter une situation de court-circuit survenant dans
un circuit ayant une pluralité de dispositifs à semi-conducteurs de puissance
(1) de type à mise hors tension montés en série après la détection
de celle-ci, ledit dispositif comportant des éléments (13) adaptés
pour mesurer la tension à travers les deux électrodes (11, 12) de chaque
dispositif à semi-conducteurs de puissance individuel, des moyens (8, 10) adaptés
pour délivrer indépendamment du courant à la grille (9) de chaque
dispositif à semi-conducteurs de puissance individuel ou depuis celle-ci pour
réguler individuellement la conduction de ceux-ci et des éléments
(6) adaptés pour recevoir des informations concernant ladite tension et après
une détection d'un court-circuit commander lesdits moyens pour réguler
individuellement le processus de mise hors tension ainsi provoqué pour chacun
des dispositifs à semi-conducteurs de puissance, caractérisé en
ce que ledit élément de commande (6) est adapté pour commander
les moyens d'alimentation afin de réduire la vitesse de mise hors tension pour
chaque dispositif à semi-conducteurs de puissance individuel pendant le processus
de mise hors tension, lorsque la tension mesurée à travers ceux-ci augmente.
Dispositif selon la revendication 8, caractérisé en ce
qu'il comporte des éléments (31) adaptés pour comparer la tension
mesurée à travers chaque dispositif à semi-conducteurs de puissance
individuel (1) à des valeurs de tension de référence associées
au dispositif à semi-conducteurs de puissance et envoyer des informations concernant
cette comparaison audit élément de commande (6) pour commander individuellement
le processus de mise hors tension de chaque dispositif à semi-conducteurs de
puissance.
Dispositif selon la revendication 9, caractérisé en ce
que, lorsque la tension à travers les deux électrodes (11, 12) d'un
dispositif à semi-conducteurs de puissance individuel excède une valeur
de référence prédéterminée (29), lesdits éléments
de commande (6) sont adaptés pour commander les moyens d'alimentation afin
d'amener une transition pour mettre sous tension le dispositif à semi-conducteurs
de puissance en inversant la direction du courant délivré à la grille
(9) de ce dispositif à semi-conducteurs de puissance eu égard à la
direction au moment de la mise hors tension.
Dispositif selon l'une quelconque des revendications 8 à 10,
caractérisé en ce que lesdits éléments pour mesurer la
tension à travers les deux électrodes de chaque dispositif à semi-conducteurs
de puissance individuel comportent un diviseur de tension (13) monté en parallèle
avec le dispositif à semi-conducteurs de puissance respectif et adapté
pour mesurer une proportion particulière de ladite tension afin de déterminer
la tension réelle.
Dispositif selon la revendication 11, caractérisé en ce
que ledit diviseur de tension (13) a une grande largeur de bande s'étendant
de 0 Hz jusqu'à une région de fréquence étant élevée
eu égard aux fréquences de commutation typiques du dispositif à semi-conducteurs
de puissance.
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Patent Zeichnungen (PDF)
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