Method and control device for protection time setting in an electric drive system
The invention relates to a control device ( 12 ) for actuating a pulse-controlled converter of an electric drive system, having: an open-loop/closed-loop control circuit ( 12 a) which is configured to generate pulse-width-modulated actuation signals for switching devices of the pulse-controlled converter; a fault logic circuit ( 12 b) which can detect fault states in the drive system and which is configured to select a switching state or a sequence of switching states for the switching devices of the pulse-controlled converter which are assigned to the corresponding fault state; and a protection circuit ( 12 c) which is embodied in hardware and which comprises a signal delay device ( 15 ), which is configured to delay the actuation signals in order to implement a minimum protection time, and a locking device ( 16 a, 16 b) which is configured to lock two complementary switching devices of a bridge branch of the pulse-controlled converter with respect to one another.
1. A control device ( 12 ) for controlling a pulse-controlled inverter ( 5 ) of an electric drive system, comprising:
an open-loop/closed-loop control circuit ( 12 a ) embodied as a microprocessor and configured to generate pulse-width-modulated control signals for switching devices of the pulse-controlled inverter ( 5 ) to dynamically adjust protection times for driving complementary switching devices in a bridge branch of the pulse-controlled inverter ( 5 );
a fault logic circuit ( 12 b ) , which can detect fault states in the drive system and configured to select a switching state or a sequence of switching states for the switching devices of the pulse-controlled inverter ( 5 ) which are assigned to the corresponding fault state;
a protection circuit ( 12 c ), which is embodied in hardware and which comprises
a signal delay device ( 15 ), configured to delay the control signals in order to implement a minimum protection time, and
a latching device ( 16 a , 16 b ), configured to latch two complementary switching devices of a bridge branch of the pulse-controlled inverter ( 5 ) with respect to one another; and
a driver circuit ( 12 d ), configured to drive the switching devices of the pulse-controlled inverter ( 5 ) depending on the control signals output by the protection circuit ( 12 c );
wherein the protection circuit ( 12 c ) is the last logic element upstream of the driver circuit ( 12 d ) and is independent of the open-loop/closed-loop control circuit ( 12 a ); and
wherein the arrangement of the hardware protection circuit ( 12 a ) enables the setting of the minimum protection time and a failsafe latching of complementary power switching elements in the inverter ( 5 ) without adversely influencing open-loop/closed-loop control circuit software control of the switching times.
2. The control device ( 12 ) as claimed in claim 1 , wherein the signal delay device ( 15 ) comprises a multiplicity of shift registers ( 15 a , 15 b , 15 n ), which are clocked via the computer clock of the open-loop/closed-loop control circuit ( 12 a ).
3. The control device ( 12 ) as claimed in claim 1 , wherein the latching device ( 16 a , 16 b ) comprises at least two logic AND gates, which receive as input signals a control signal of a first switching device and a negated control signal of a second switching device, which is complementary to the first switching device.
4. A system, comprising:
a control device ( 12 ) as claimed in claim 1 ;
a pulse-controlled inverter ( 5 ) having a multiplicity of complementary switching devices in a full-bridge circuit, which are controlled via the control device; and
an electric machine ( 1 ), which is supplied with an electrical supply voltage by the pulse-controlled inverter ( 5 ).
5. A method for controlling a pulse-controlled inverter ( 5 ) of an electric drive system, comprising:
generating, by a microprocessor, pulse-width-modulated control signals for complementary switching devices of the pulse-controlled inverter ( 5 ) in a software circuit;
setting dynamic protection times for the activation of the complementary switching devices in bridge branches of the pulse-controlled inverter ( 5 );
detecting a fault state in the drive system;
selecting a switching state or a sequence of switching states for the switching devices of the pulse-controlled inverter ( 5 ) which are assigned to the corresponding fault state; and
delaying, by a protection circuit ( 12 c ), the control signals in order to implement a minimum protection time; and
latching two complementary switching devices of a bridge branch of the pulse-controlled inverter ( 5 ) in a hardware circuit;
wherein the protection circuit ( 12 c ) is the last logic element upstream of a driver circuit ( 12 d ) for driving he pulse-controlled inverter ( 5 ) and is independent of the software circuit; and
wherein the arrangement of the hardware protection circuit enables the setting of the minimum protection time and a failsafe latching of the two complementary switching devices without adversely influencing the software control of the pulse-width-modulated control signals.