Apparatus and method for controlling discharge of intermediate circuit capacitor

Abstract

The invention relates to activation of active discharge of an intermediate circuit capacitor. To this end, a discharge device is provided, which can detect a condition for activating the discharge of the intermediate circuit capacitor independent of additional system components, and thus can initiate the active discharge of the intermediate circuit capacitor. To this end, the voltage at the intermediate circuit capacitor is evaluated, and an active discharge of the intermediate circuit capacitor is permitted if the gradient of the voltage at the intermediate circuit capacitor falls below a predefined threshold value.

Description

Technical Field

[0001] The invention relates to a device and a method for controlling the discharge of an intermediate circuit capacitor, a device for the discharge of an intermediate circuit capacitor, a power converter and an electric drive system. Background Art

[0002] Power converters for converting an input voltage into an output voltage are used in a large number of application areas. Such converters are used, for example, in electric drive systems, such as are also used primarily in electric vehicles. In this case, the input DC voltage, which is usually several hundred volts, is converted by the converter into an output voltage for actuating the electric machine. In order to stabilize the input DC voltage, so-called intermediate circuit capacitors are provided.

[0003] In order to avoid possible dangers that could be caused by a charged intermediate circuit capacitor in the event of an accident or during maintenance work, the intermediate circuit capacitor is deliberately discharged when the electric drive system is switched off or deactivated.

[0004] For example, laid-open patent application DE 10 2013 224 884 A1 describes a device and a method for discharging such an intermediate circuit capacitor. In this case, a discharge controller is provided which discharges the intermediate circuit capacitor via an electrical load with a predetermined discharge current. Summary of the invention

[0005] The invention provides a device and a method for controlling the discharge of an intermediate circuit capacitor, a device for discharging an intermediate circuit capacitor, a power converter and an electric drive system having the features of the independent claims. Further advantageous embodiments are the subject matter of the dependent claims.

[0006] The corresponding settings are:

[0007] A device for controlling the discharge of an intermediate circuit capacitor comprises a monitoring device and a control device. The monitoring device is designed to detect the voltage across the intermediate circuit capacitor. The control device is designed to determine the time gradient of the voltage across the intermediate circuit capacitor. Furthermore, the control device is designed to allow active discharge of the intermediate circuit capacitor if the gradient of the voltage across the intermediate circuit capacitor falls below a predetermined first threshold value.

[0008] Additionally set:

[0009] A device for discharging an intermediate circuit capacitor, comprising a passive discharge path, an active discharge path and a device according to the invention for controlling the discharge of the intermediate circuit capacitor. The passive discharge path comprises a resistor and / or an electrical load between a first connection of the intermediate circuit capacitor and a second connection of the intermediate circuit capacitor. The active discharge path comprises a switching element between the first connection of the intermediate circuit capacitor and the second connection of the intermediate circuit capacitor. In particular, the active discharge path can comprise a series circuit consisting of a switching element and a further resistor and / or a further electrical load. In this case, the device for controlling the discharge of the intermediate circuit capacitor is designed to close the switching element in the active discharge path when active discharge of the intermediate circuit capacitor is permitted.

[0010] Additionally set:

[0011] A power converter having an input connection, an intermediate circuit capacitor, an output connection and a device according to the invention for discharging the intermediate circuit capacitor. The input connection is designed to be connected to a DC voltage source. The intermediate circuit capacitor is arranged between a first connection point and a second connection point of the input connection. The converter is particularly designed to convert a DC voltage provided at the input connection into a predetermined output voltage and to provide the output voltage to the output connection.

[0012] Additionally set:

[0013] An electric drive system comprises a power converter according to the present invention and a motor, wherein the motor is electrically connected to an output terminal of the converter.

[0014] The last settings are:

[0015] A method for controlling the discharge of an intermediate circuit capacitor comprises a step for detecting a voltage across the intermediate circuit capacitor, a step for determining a time gradient of the voltage across the intermediate circuit capacitor, and a step for permitting active discharge of the intermediate circuit capacitor if the time gradient of the voltage across the intermediate circuit capacitor falls below a predetermined first threshold value.

[0016] Advantages of the present invention:

[0017] For example, intermediate circuit capacitors present in power converters can continue to store electrical energy even after the converter has been switched off in active operation, so that relatively high voltages can be applied via the intermediate circuit capacitors, if necessary for a longer period of time. In order to avoid possible dangers that could result from such high voltages, it is desirable to discharge the intermediate circuit capacitors as quickly as possible as soon as the power converter is deactivated.

[0018] Although such an active discharge of the intermediate circuit capacitor can in principle be initiated by the control of the converter, it is also necessary or at least desirable, for example for safety reasons, to provide an intermediate circuit capacitor discharge that is independent of the control. Thus, even in the event of a failure or malfunction of the control for the converter, a rapid and reliable discharge of the intermediate circuit capacitor can be ensured by an additional device that is independent of the actual control.

[0019] However, it is necessary for this purpose that such a system, which is independent of the actual control, also detects operating states in which the intermediate circuit capacitor can be discharged as quickly and reliably as possible.

[0020] The invention makes use of the fact that, when the converter is switched off and, in conjunction with this, the converter is disconnected from the input voltage source, the voltage on the intermediate circuit capacitor decreases continuously over time. This is usually supported by a resistor arranged in parallel with the intermediate circuit capacitor in a passive discharge branch. This continuously decreasing voltage corresponds mathematically to a negative gradient of the voltage on the intermediate circuit capacitor. In other words, if the gradient of the voltage on the intermediate circuit capacitor has a negative value, the absolute value of which (Betrag) exceeds a predefined threshold value, this can serve as an indication that the power converter is deactivated. Thus, in such a case, an active discharge of the intermediate circuit capacitor can be initiated.

[0021] Thus, by monitoring the voltage across the intermediate circuit capacitor, an easy and at the same time very reliable possibility is provided in order to be able to decide whether an active discharge of the intermediate circuit capacitor should be initiated. In particular, in this way, an active discharge of the intermediate circuit capacitor can be decided completely independently of the control of the converter itself. Thus, even in the event of a functional failure of this control of the converter, active discharge of the intermediate circuit capacitor can be initiated by an independent mechanism. The safety of the entire system can thereby be increased.

[0022] In this case, a simple voltage sensor is sufficient to detect the voltage across the intermediate circuit capacitor. For this purpose, for example, a voltage divider in the form of a series circuit of a plurality of resistors can also be used. If necessary, such a resistor divider for detecting the voltage across the intermediate circuit capacitor can also be combined with a resistor in the passive discharge branch. Furthermore, any other possible options for detecting the voltage across the intermediate circuit capacitor are of course also possible.

[0023] In order to determine the gradient of the voltage on the intermediate circuit capacitor, for example, the voltage profile within a predetermined time interval can be analyzed. For example, the current voltage on the intermediate circuit capacitor can be compared with the voltage on the intermediate circuit capacitor at a predetermined time period, for example one second ago, and the voltage gradient can be calculated therefrom. However, any other suitable time intervals are also possible in principle. For example, it is also possible to perform a time filtering on the voltage profile in order to eliminate short-term voltage peaks if necessary.

[0024] The evaluation of the voltage profile across the intermediate circuit capacitor can be carried out in any suitable manner, for example by means of a microcontroller, a dedicated integrated circuit or in any other manner.

[0025] According to one specific embodiment, the control device is designed to permit active discharge of the intermediate circuit capacitor only if at least a predetermined time period has elapsed since the previous active discharge of the intermediate circuit capacitor. In this way, a minimum pause time can be set between two consecutive active discharges. This makes it possible, for example, to prevent undesired activation of intermediate circuit capacitor discharges in rapid succession in the case of very dynamic changes in the voltage across the intermediate circuit capacitor.

[0026] According to one specific embodiment, the control device is designed to allow active discharge of the intermediate circuit capacitor even when the voltage across the intermediate circuit capacitor is below a predefined minimum voltage. For example, a minimum input voltage can be specified as a threshold value for this minimum voltage. The minimum input voltage can correspond, for example, to a voltage to be expected at least at the input. For a battery-fed transformer, this can correspond, for example, to a minimum battery voltage, for example the voltage of a discharged battery or the voltage of a discharged battery under load. If the voltage across the intermediate circuit capacitor is below such a minimum voltage, it can be assumed that the intermediate circuit capacitor is disconnected from the voltage source and therefore the prerequisites for discharging the intermediate circuit capacitor can exist.

[0027] According to one specific embodiment, the control device is designed to detect the rotational speed of an electric machine in an electric drive system having an intermediate circuit capacitor. In this case, the control device can be designed to allow active discharge of the intermediate circuit capacitor if the detected rotational speed is below a predetermined rotational speed. If, for example, the value zero is used as the predetermined minimum rotational speed, this corresponds to a stationary state of the electric machine. As an alternative to a rotational speed of zero, a rotational speed can also be selected at which the induced voltage generated by the electric machine is below a predetermined maximum value in terms of amplitude. The predetermined maximum value can correspond, for example, to a value that is less than or equal to the maximum permissible voltage of the discharged intermediate circuit capacitor.

[0028] According to one embodiment, the control device is designed to stop the active discharge of the intermediate circuit capacitor when the time gradient of the voltage on the intermediate circuit capacitor exceeds a predetermined second threshold value. Here, the predetermined second threshold value can correspond, for example, to a predetermined first threshold value for permitting active discharge. Alternatively, the two threshold values ​​can differ so that, for example, a hysteresis is provided between the first threshold value and the second threshold value. If the time gradient of the voltage on the intermediate circuit capacitor exceeds the second threshold value, this can indicate, for example, that the conditions for active discharge of the intermediate circuit capacitor are not currently met in a system with an intermediate circuit capacitor. The previous lower than rated gradient of the voltage on the intermediate circuit capacitor can be caused, for example, by a relatively large load. In such a case, the voltage disturbance on the intermediate circuit capacitor can be subsequently compensated by a connected voltage source. The gradient of the voltage on the intermediate circuit capacitor is thereby increased. In such a case, it can be determined that the discharge of the intermediate circuit capacitor that may have started is inappropriate, and the discharge of the intermediate circuit capacitor can thus be stopped again.

[0029] According to one embodiment of the electric drive system, the device for controlling the discharge of the intermediate circuit capacitor is designed to allow active discharge of the intermediate circuit capacitor only when a predetermined operating state is set by the converter. The operating state in which active discharge of the intermediate circuit capacitor can be allowed can be, for example, so-called reliable operating states such as active short circuit or no-load operation. In this way, it can be ensured that active discharge of the intermediate circuit capacitor does not take place as long as the drive system is in an operating mode for controlling the electric machine, in which the electric machine is actively operated as a motor or generator.

[0030] As long as it makes sense, the above-mentioned designs and modifications can be combined with each other arbitrarily. Other designs, modifications and implementations of the present invention also include combinations of features of the present invention described above or below with respect to the embodiments that are not explicitly mentioned. In particular, those skilled in the art will also add various aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following is an explanation of the other features and advantages of the present invention with reference to the accompanying drawings.

[0032] Figure 1 A schematic diagram shows a basic circuit diagram of an electric drive system according to one embodiment, the electric drive system having a device for controlling the discharge of an intermediate circuit capacitor;

[0033] Figure 2 A voltage-time diagram according to one specific embodiment is shown for illustrating the control of the discharge of an intermediate circuit capacitor;

[0034] Figure 3 A voltage-time diagram according to a further embodiment is shown for illustrating the control of the discharge of the intermediate circuit capacitor; and

[0035] Figure 4 A flow chart is shown on which a method for controlling the discharge of an intermediate circuit capacitor according to one specific embodiment is based. DETAILED DESCRIPTION

[0036] Figure 1 The schematic diagram of a principle circuit diagram of an electric drive system according to one embodiment is shown, which has a device 1 for discharging an intermediate circuit capacitor. The electric drive system comprises a converter 2 and an electric machine 3 connected to the power converter 2. The power converter 2 can be supplied with electrical energy at the input connection by a voltage source 4. The voltage source 4 can be, for example, a DC voltage source, in particular a battery, such as a traction battery of an electric vehicle. The voltage source 4 can be disconnected from the input connection of the converter 2 by means of switching elements 41, 42. To operate the electric drive system, the two switches 41, 42 are closed.

[0037] The power converter 2 can thus generate a voltage suitable for driving the electric machine 3 using the electrical energy provided by the voltage source 4. In a further operating mode, the converter 2 can convert the voltage generated by the electric machine 3 in generator operation into a voltage suitable for charging the battery 4 connected to the input connection of the converter 2.

[0038] In order to stabilize the input voltage, an intermediate circuit capacitor 20 is provided between two connection points of the input connection in the converter 2. If the converter 2 is deactivated, even when the two switching elements 41, 42 are open, the voltage can still be present via the charged intermediate circuit capacitor 20. In such a case, the intermediate circuit capacitor 20 can be discharged by the device 1 for discharging the intermediate circuit capacitor 20.

[0039] The device 1 for discharging an intermediate circuit capacitor 20 comprises an active discharge path and a passive discharge path. In the passive discharge path, a resistor 12 is arranged between two connection points of the input connection of the converter 2. Of course, as an alternative to a single resistor 12, a series circuit and / or a parallel circuit of a plurality of resistors can also be provided. Therefore, as long as a voltage is applied across the intermediate circuit capacitor 20, a current always flows through such a resistor 12 in the passive discharge path. As a result, the intermediate circuit capacitor 20 is continuously discharged with a relatively low discharge current.

[0040] In the active discharge path, a switching element 13 is arranged between two connection points of the DC voltage connection of the converter 2. In addition, at least one resistor 14 can be arranged in series with the switching element 13. By means of the resistor 14, the discharge current can be limited during the active discharge of the intermediate circuit capacitor 20. For this active discharge of the intermediate circuit capacitor 20, the switching element 13 is closed. The switching element 13 can be controlled, for example, by the control device 11, so that the active discharge of the intermediate circuit capacitor 20 begins. The resistors 12 and 14 can be implemented, for example, as ohmic resistors in the passive discharge path and the active discharge path. However, it is also possible as an additional or alternative solution to arrange other suitable electrical loads. In particular, as an electrical load, the controlled discharge of the intermediate circuit capacitor 20 through the converter 2, in particular through the so-called thermal branch of the converter 2, can also be included here.

[0041] In this case, the control device 11 can be operated in particular independently of other components of the electric drive system, for example a control circuit for actuating the converter 2. Thus, even if malfunctions occur in other components of the drive system, the discharge of the intermediate circuit capacitor 20 can be activated.

[0042] The control device 11 of the device 1 for discharging the intermediate circuit capacitor 20 can detect the voltage across the intermediate circuit capacitor 20. For this purpose, for example, a current sensor for monitoring the current can be provided. In this case, the control device 11 can continuously monitor the voltage across the intermediate circuit capacitor 20. For example, it is also possible to periodically detect the voltage across the intermediate circuit capacitor 20 at predetermined time intervals and evaluate it as explained below.

[0043] The control device 11 evaluates the voltage across the intermediate circuit capacitor 20 and, using the measured value of the voltage across the intermediate circuit capacitor 20 , controls a switching element 13 in an active discharge path of the device 1 for discharging the intermediate circuit capacitor 20 in order to activate or deactivate the active discharge of the intermediate circuit capacitor 20 .

[0044] For example, the gradient of the time profile of the voltage across the intermediate circuit capacitor 20 can be determined from the time profile of the voltage across the intermediate circuit capacitor 20. The gradient corresponds to the time profile of the voltage across the intermediate circuit capacitor 20. A negative gradient corresponds to a drop in the voltage across the intermediate circuit capacitor 20, while a positive gradient corresponds to an increase in the voltage across the intermediate circuit capacitor 20.

[0045] If the intermediate circuit capacitor 20 of the converter 2 is disconnected from the voltage source 4, for example by opening the switching elements 41, 42, the voltage on the intermediate circuit capacitor 20 will drop over time, because the intermediate circuit capacitor 20 is discharged via the passive discharge path with the resistor 12. Therefore, the control device 11 of the device 1 for discharging the intermediate circuit capacitor 20 can detect this drop in voltage and thus allow the active discharge of the intermediate circuit capacitor 20 via the active discharge path. For this purpose, the control device 11 can, for example, recognize that the gradient of the voltage curve on the intermediate circuit capacitor 20 has a negative value below a predetermined threshold value. In other words, the absolute value of the negative gradient exceeds the threshold value. In this case, the threshold value (below which the negative gradient of the voltage curve of the voltage on the intermediate circuit capacitor 20 should drop before the active discharge is triggered) should be selected, for example, as a function of the discharge current through the passive discharge path with the resistor 12.

[0046] Figure 2 A schematic diagram of a voltage-time diagram is shown to illustrate the previously described principle for permitting active discharge of the intermediate circuit capacitor 20. In a first section I, the electric drive system is, for example, in a normal operating state. During this normal operating state, the electric drive system is supplied with electrical energy, for example, by a voltage source 4, so that the voltage U_Z on the intermediate circuit capacitor 20 is at least approximately constant at a value of about U_1. If, for example, the connection between the voltage source 4 and the input connection of the converter 2 is disconnected by disconnecting the switching elements 41, 42, the voltage U_Z on the intermediate circuit capacitor 20 drops, because the intermediate circuit capacitor 20 is discharged through a passive discharge path having a resistor 12. This drop in the voltage U_Z on the intermediate circuit capacitor 20 in the second phase II and the negative gradient associated therewith can be detected, for example, by the control device 11. If the gradient of the voltage U_Z on the intermediate circuit capacitor 20 is below a predetermined threshold value, the control device 11 thereby permits active discharge and closes the switching element 13 in the active discharge path. Thus, in the third phase III, the intermediate circuit capacitor 20 is discharged via the active discharge path having the switching element 13 and the resistor 14. In particular, this discharge process is maintained until the voltage U_Z across the intermediate circuit capacitor 20 falls below a predetermined maximum value U_2 of, for example, 60 volts. As a result, the active discharge of the intermediate circuit capacitor 20 can be terminated and the switching element 13 in the active discharge path can be opened again, so that in the section IV the voltage permanently falls below the maximum permissible value U2.

[0047] In addition to evaluating the gradient in the voltage profile of the voltage U_Z across the intermediate circuit capacitor 20, it is also possible to additionally take into account the absolute value of the voltage U_Z across the intermediate circuit capacitor 20 in order to activate the active discharge of the intermediate circuit capacitor 20. If the voltage U_Z across the intermediate circuit capacitor 20, for example, falls below a previously specified minimum voltage, this can also serve as an indication that the input of the converter 2 and therefore the intermediate circuit capacitor 20 are not electrically connected to the voltage source 4. If the power converter 2 is fed by a voltage source 4 with a battery, this minimum voltage can, for example, correspond to the minimum battery voltage, in particular to the minimum battery voltage under load. This minimum battery voltage can, for example, correspond to the minimum battery voltage of a discharged battery. If the voltage U_Z across the intermediate circuit capacitor 20 falls below this previously specified minimum voltage, this can also serve as an indication that the input of the converter 2 is not further connected to the DC voltage source 4. Therefore, in this case, the active discharge of the intermediate circuit capacitor 20 via the active discharge path with the switching element 13 can also be permitted.

[0048] Furthermore, the permission for active discharge can also be linked to any other conditions. For example, active discharge of the intermediate circuit capacitor 20 can only be permitted when the motor 3 of the drive system is stopped or the rotational speed of the motor 3 is below a predefined limit value. For example, the following rotational speed can be selected as the maximum rotational speed of the motor 3, at which the motor induces a voltage in the generator operating mode, the peak value of which is below the predefined maximum voltage value.

[0049] Figure 3 Schematic diagram of a voltage-time diagram showing the voltage profile of the voltage U_Z across the intermediate circuit capacitor 20 according to a further specific embodiment. Figure 2During normal operation of the electric drive system in phase I, the voltage U_Z on the intermediate circuit capacitor 20 is at least approximately at a constant value U_1. If the voltage source 4 feeding the input of the transformer 2 is subjected to a very large load, for example due to the activation of a large load, this will also cause the voltage U_Z at the input of the DC transformer 2 and therefore on the intermediate circuit capacitor 20 to drop briefly and cause a negative gradient accordingly. This may lead to the undesired activation of the active discharge of the intermediate circuit capacitor 20 in phase II. However, since the DC voltage source 4 continuously provides further electrical energy, this short-term voltage disturbance is compensated very quickly and the voltage U_Z at the input of the transformer and therefore on the intermediate circuit capacitor 20 rises again at least approximately to the original value U_1. In this case, the control device 11 can detect a correspondingly high positive gradient of the voltage on the intermediate circuit capacitor 20. In such a case, the active discharge of the intermediate circuit capacitor 20 can be stopped by disconnecting the switching element 13 again. Therefore, in the case of such a voltage disturbance due to the activation of a large load, only a short-term activation of the active discharge of the intermediate circuit capacitor 20 occurs. In order to prevent undesired activation of the discharge of the intermediate circuit capacitor 20 too frequently in particularly dynamic systems, further activation of the active discharge of the intermediate circuit capacitor 20 may be permitted, for example, only if a predetermined time period has elapsed since the previous activation of the active discharge.

[0050] Figure 4 The flowchart on which the method for controlling the discharge of the intermediate circuit capacitor 20 according to one specific embodiment is based is shown. The method can in principle include any method steps as have been described above in conjunction with the device 1 for discharging the intermediate circuit capacitor 20. Similarly, the device 1 for discharging the intermediate circuit capacitor 20 described above can also have any components as are required for implementing the method described below.

[0051] In step S1, the voltage U_Z is first detected across the intermediate circuit capacitor 20. As a result, the gradient of the detected time profile of the voltage U_Z across the intermediate circuit capacitor 20 can be determined in step S2. If the gradient of the time profile of the voltage U_Z across the intermediate circuit capacitor 20 is below a predefined threshold value, that is to say if the absolute value of the negative gradient is greater than a corresponding positive threshold value, an active discharge of the intermediate circuit capacitor 20 is permitted. For such an active discharge of the intermediate circuit capacitor 20, for example, a switching element 13 in an active discharge path connected in parallel with the connection of the intermediate circuit capacitor 20 can be closed.

[0052] In order to evaluate the gradient of the time profile of the voltage U_Z across the intermediate circuit capacitor 20, the measured value of the voltage U_Z across the intermediate circuit capacitor 20 can optionally also be subjected to a time filtering. In order to determine the gradient of the voltage U_Z across the intermediate circuit capacitor 20, for example, the change in the voltage U_Z within a time interval of one second can be taken into account. However, in principle, any other suitable time intervals are also possible.

[0053] In summary, the invention relates to the activation of an active discharge of an intermediate circuit capacitor. For this purpose, a discharge device is provided which can detect conditions for activating the discharge of the intermediate circuit capacitor independently of further system components and can thereby initiate the active discharge of the intermediate circuit capacitor. For this purpose, the voltage across the intermediate circuit capacitor is evaluated and, if the gradient of the voltage across the intermediate circuit capacitor is below a predefined threshold value, active discharge of the intermediate circuit capacitor is permitted.

Claims

1. A device for controlling the discharge of an intermediate circuit capacitor (20), comprising: a monitoring device, which is designed to detect the voltage (U_Z) across the intermediate circuit capacitor (20); A control device (11) is designed to determine the time gradient of the voltage (U_Z) across the intermediate circuit capacitor (20) and to allow active discharge of the intermediate circuit capacitor (20) when the time gradient of the voltage (U_Z) across the intermediate circuit capacitor (20) is below a predetermined first threshold value.

2. The device according to claim 1, wherein The control device (11) is designed to permit active discharging of the intermediate circuit capacitor (20) only if at least a predetermined period of time has elapsed since a previous active discharging of the intermediate circuit capacitor (20).

3. The device according to claim 1 or 2, wherein: The control device (11) is designed to permit active discharging of the intermediate circuit capacitor (20) when the voltage (U_Z) across the intermediate circuit capacitor (20) falls below a predetermined minimum voltage.

4. The device according to any one of claims 1 to 3, wherein: The control device (11) is designed to detect the rotational speed of an electric machine (3) in an electric drive system having the intermediate circuit capacitor (20) and to permit active discharge of the intermediate circuit capacitor (20) if the detected rotational speed falls below a predetermined rotational speed value.

5. The device according to any one of claims 1 to 4, wherein: The control device is designed to stop the active discharging of the intermediate circuit capacitor (20) if the time gradient of the voltage (U_Z) across the intermediate circuit capacitor (20) exceeds a predetermined second threshold value.

6. A device (1) for discharging an intermediate circuit capacitor (20), comprising: a passive discharge path, which is arranged between a first connection of the intermediate circuit capacitor (20) and a second connection of the intermediate circuit capacitor (20), and which comprises a resistor (12) and / or an electrical load; an active discharge path, which is arranged between a first connection of the intermediate circuit capacitor (20) and a second connection of the intermediate circuit capacitor (20) and comprises a switching element (13); and The device for controlling the discharge of an intermediate circuit capacitor (20) according to any one of claims 1 to 5, wherein: The device for controlling the discharge is designed to close the switching element (13) in the active discharge path when active discharge of the intermediate circuit capacitor (20) is permitted.

7. A power converter (2) comprising: An input connector, which is designed to be connected to a DC voltage source (4); an intermediate circuit capacitor (20) arranged between a first connection point and a second connection point of the input connection; Output connector; The device (1) for discharging an intermediate circuit capacitor (20) according to claim 6, wherein the converter (2) is designed to convert the DC voltage provided at the input connection into a predetermined output voltage and to provide it to the output connection.

8. An electric drive system having: The power converter (2) according to claim 7; and A motor (3) is electrically connected to an output terminal of the converter (2).

9. The electric drive system according to claim 8, wherein: The device for controlling the discharge of an intermediate circuit capacitor (2) is designed to permit active discharge of the intermediate circuit capacitor (20) only when a predetermined operating state is set by the converter (2).

10. A method for controlling the discharge of an intermediate circuit capacitor (2), the method comprising the steps of: Acquiring (S1) a voltage on the intermediate circuit capacitor (2); determining (S2) the time gradient of the voltage (U_Z) across the intermediate circuit capacitor (2); In the event that the time gradient of the voltage across the intermediate circuit capacitor (20) is below a predetermined first threshold value, active discharging of the intermediate circuit capacitor (20) is permitted (S3).

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