DE102018204230A1 - Filter device for an electric power converter, electric power converter and method for driving a filter device for an electric power converter - Google Patents

Abstract

The present invention relates to the discharge of capacitors at a DC input of an electric power converter. For this purpose, the Y capacitors are short-circuited at the input terminal by means of suitable switching elements. In this way, an electrical connection between the two terminals of the DC voltage terminal of the power converter is created. Thus, a DC link capacitor between the two terminals of the DC voltage terminal of the power converter can be discharged.

Description

The present invention relates to a filter device for an electric power converter and a method for driving a filter device for an electric power converter. Furthermore, the present invention relates to an electric power converter with a filter device.

State of the art

Fully or partially electrically powered vehicles usually have a high-voltage architecture with a so-called high-voltage DC link. The high-voltage components have a DC link capacity. This DC link capacity is charged during operation to the electrical voltage of the high-voltage electrical system. The current standards require that for safety reasons, a discharge of the DC link capacitors must be provided within a predetermined period of time to a predetermined maximum voltage. For this purpose, suitable unloading devices should be provided.

The publication DE 10 2009 022 167 A1 discloses a high-voltage system for an electrically driven motor vehicle. In this case, a high-voltage intermediate circuit with a central and actively activatable discharge circuit is provided between a battery and a consumer. Furthermore, each consumer has a passive discharge circuit.

Disclosure of the invention

The present invention provides a filter device for an electrical power converter with the features of claim 1, an electric power converter with the features of claim 6, and a method for driving a filter device for an electric power converter with the features of claim 7.

Accordingly, it is provided:

A filter device for an electric power converter having a first capacitor, a second capacitor and a third capacitor. The filter device further comprises a first switching element and a second switching element. The first capacitor is disposed between the first input terminal of the power converter and a node. The second capacitor is arranged between a second input terminal of the power converter and the node. The third capacitor is arranged between the first input terminal and the second input terminal of the power converter. The first switching element is arranged between the first input terminal of the power converter and the node. In particular, the first switching element is designed to provide an electrical connection between the first input terminal of the power converter and the node. The second switching element is arranged between the second input terminal and the node. In particular, the second switching element is designed to provide an electrical connection between the second input terminal of the power converter and the node.

Furthermore, it is provided:

An electric power converter with a filter device according to the invention.

Finally, it is planned:

A method of driving a filter device for an electric power converter. The filtering device of the method comprises a first capacitor, a second capacitor and a third capacitor. The first capacitor is arranged between a first input terminal of the power converter and a node. The second capacitor is arranged between a second input terminal of the power converter and the node. The third capacitor is disposed between the first input terminal and the second input terminal. The method includes the steps of providing an electrical connection between the first input terminal and the node, and providing another electrical connection between the second input terminal and the node.

Advantages of the invention

The present invention is based on the finding that capacitors, in particular capacitors, in a high-voltage network, such as, for example, the high-voltage network of an electric vehicle, are charged during operation to high and thus dangerous electrical voltages. Therefore, for safety reasons and to comply with applicable regulations, an active discharge of the electrical voltage must be provided by such capacitors. In addition to the intermediate circuit capacitors between a positive and a negative terminal of the high-voltage network, other capacitors, for example so-called Y capacitors for filtering common-mode noise, may be provided in particular.

The present invention is therefore based on the idea to take this knowledge into account and to create an efficient and reliable discharge of the capacitors in a high-voltage electrical system, especially in the high-voltage DC link. For this purpose, it is provided according to the invention to bridge the so-called Y capacitors for discharging the capacitors electrically. This can be done, for example, by means of an actively designed short circuit of the respective Y capacitors. The simultaneous bridging of the Y capacitors thereby also creates an electrical connection between the two terminals of the intermediate circuit capacitor, which is arranged between a positive and a negative terminal of the DC voltage network.

Thus, by bridging the two Y capacitors, a complete discharge of all capacitors in the high-voltage intermediate circuit can take place. In particular, further components for direct discharge of the DC link capacitor between the positive and the negative terminal of the high-voltage network can be saved.

The two Y capacitors are each arranged between a connection of the high-voltage vehicle electrical system and a node. In particular, the node can be electrically coupled to a reference potential, such as a ground terminal.

The circuit arrangement according to the invention thus makes it possible to discharge all capacitors required for common-mode and push-pull filtering by means of only two switching elements. Thus, the given by standards and legal requirements can be reliably met with little effort on components.

In an embodiment, the filter device comprises a control device. The control device may be designed to jointly control the first switching element and the second switching element. By driving the switching elements can be made in each case an electrical connection between the respective input terminal and the node. In this case, not only the respective capacitor is bypassed by the simultaneous driving of the two switching elements, which is arranged parallel to the respective switching element, but at the same time an electrical connection of the third capacitor between the first input terminal and the second input terminal is made via the two switching elements. In this way, all three capacitors are thus discharged simultaneously.

In one embodiment, the first switching element and the second switching element each comprise a semiconductor switching element. The semiconductor switching elements may, for example, be a MOSFET or a bipolar transistor with an insulated gate connection (IGBT). In addition, of course, any other suitable semiconductor switching elements are possible. In particular, such switching elements can be used as switching elements, which have a sufficient current carrying capacity to discharge the electrical energy stored in the capacitors can.

In one embodiment, the filter device comprises a first electrical resistance and a second electrical resistance. The first electrical resistor may be disposed between the first input terminal and the node. The second electrical resistor may be disposed between the second input terminal and the node. In this way, an electrical resistance is in each case arranged parallel to the first and the second capacitor. These electrical resistors may in particular be high-resistance resistors, for example electrical resistors with a resistance of several kilohms or several megohms. Such electrical resistances make it possible to discharge the capacitors even when the switching elements are open, so that a discharge of the capacitors can also be made possible in the event of a fault, if one or both of the switching elements can not be closed.

In an embodiment, a series circuit of an electrical resistance and a switching element may be provided between the first input terminal and the node. Analog can be provided between the second input terminal and the node, a series circuit of a further electrical resistance and the second switching element. By the series connection of an electrical resistance and a switching element, the maximum discharge current of the respective capacitor can be limited. In this way, the loading of the switching element during unloading can be minimized.

In one embodiment, the filter device may be coupled to a DC voltage source. For example, the first input terminal may be coupled to a first terminal of a DC voltage source and the second input terminal of the filter device may be coupled to a second terminal of the DC voltage source. In this case, the filter device may comprise a circuit breaker. The circuit breaker may be configured to interrupt an electrical connection between the filter device and the DC voltage source. Depending on the application, either only an electrical connection between the DC voltage source and the first input terminal or the second input terminal are interrupted, or alternatively, both the electrical connection between the DC voltage source and the first input terminal and simultaneously the electrical connection between the DC voltage source and the second input terminal can be interrupted. In this way, during the discharge of the capacitors of the filter device, the filter device and thus also the power converter can be disconnected from the DC voltage source, so that no further electrical energy can be fed from the DC voltage source.

The above embodiments and developments can, as far as appropriate, combine arbitrarily. Further refinements, further developments and implementations of the invention also include combinations of feature of the invention which have not been explicitly mentioned above or described below with regard to the exemplary embodiments. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

list of figures

• 1: eine schematische Darstellung eines elektrischen Stromrichters mit einer Filtervorrichtung gemäß einer Ausführungsform;
• 2: eine schematische Darstellung eines elektrischen Stromrichters mit einer Filtervorrichtung gemäß einer weiteren Ausführungsform;
• 3: eine schematische Darstellung eines elektrischen Stromrichters mit einer Filtervorrichtung gemäß noch einer weiteren Ausführungsform; und
• 4: eine schematische Darstellung eines Ablaufdiagramms, wie es einem Verfahren zum Ansteuern einer Filtervorrichtung gemäß einer Ausführungsform zugrunde liegt.

Further features and advantages of the present invention will be explained below with reference to the figures. Show it:

• 1 a schematic representation of an electric power converter with a filter device according to an embodiment;
• 2 a schematic representation of an electric power converter with a filter device according to another embodiment;
• 3 a schematic representation of an electric power converter with a filter device according to yet another embodiment; and
• 4 3 is a schematic representation of a flow chart underlying a method for driving a filter device according to an embodiment.

Embodiments of the invention

1 shows a schematic representation of a block diagram for an electric power converter 2 with a filter device 1 , The electric power converter 2 in this case is a DC voltage source 3 , For example, a battery such as a traction battery powered by an electric vehicle. One connection of the DC voltage source 3 is with a first input port E1 of the power converter 2 connected, and another connection of the DC voltage source 3 is with a second input port E2 of the power converter 2 connected. The input terminals E1 and E2 of the power converter 2 are with an electric filter device 1 connected. The filter device 1 includes a first capacitor 11 which is between the first input terminal E1 of the power converter 2 and a node K is arranged. A second capacitor 12 is between the second input terminal E2 of the power converter 2 and the node K arranged. The node K can in particular be connected to a reference potential, for example a ground connection. The first capacitor 11 and the second capacitor 12 serve as so-called Y-capacitors. These capacitors 11 . 12 can be used in particular for filtering common mode noise. A third capacitor 13 is between the first input terminal E1 and the second input terminal E2 of the power converter 2 arranged. The third capacitor 13 can be used in particular for filtering push-pull interference. In the third capacitor 13 it may be, for example, a so-called intermediate circuit capacitor of the power converter 2 act.

Between the DC voltage source 3 and the power converter 2 with the filter device 1 can be a circuit breaker 30 be provided. This circuit breaker 30 can be an electrical connection between the DC voltage source 3 and the power converter 2 with the filter device 1 open or close. For example, this circuit breaker can 30 to act a single or multi-pole mechanical switch. In principle, however, any other circuit breaker, such as semiconductor switches or the like are possible.

At the power converter 2 it may be, for example, a single- or multi-phase inverter or even to a DC-DC converter (DC-DC converter). For example, the power converter 2 feeding an electric machine, such as an electric machine of an electric drive system in an electric vehicle. However, the present invention is not limited to electric drive systems or electric vehicles. Rather, the filter device 1 for the power converter 2 can be used for any application.

Parallel to the first capacitor 11 is a first switching element 21 arranged. The first switching element 21 is thus between the first input terminal E1 of the power converter 2 and the node K are arranged. Analog is a second switching element 22 between the second input terminal E2 of the power converter 2 and the node K are arranged. During operation of the power converter 2 , that is as long as the power converter 2 electrical energy from the input terminals E1 . E2 transmits to the output terminal A, the two switching elements 21 . 22 open. It is the first, the second and the third capacitor 11 . 12 . 13 charged to the respective operating voltage.

For discharging the first, second and third capacitors 11 . 12 . 13 become the first switching element 21 and the second switching element 22 closed. This creates an electrical connection between the first input terminal E1 and the node K and between the second input terminal E2 and the node K. Thus, the first capacitor 11 over the first switching element 21 be discharged, the second capacitor 12 can via the second switching element 22 be discharged and the third capacitor 13 can via the series connection of the first and second switching element 21 . 22 be discharged. To avoid further input of electrical energy, during discharge of the first, second and third capacitors 11 . 12 . 13 the electrical connection to the DC voltage source 3 by opening the circuit breaker 30 to be interrupted.

The control of the first switching element 21 , the second switching element 22 and optionally the circuit breaker 30 can, for example, via a suitable control device 50 respectively.

The control device 50 For example, the switching state of the switching elements 21 . 22 and the circuit breaker 30 depending on the operating status of the converter 2 to adjust. For example, in a motor vehicle, the activation, in particular the closing of the first and second switching element 21 . 22 depending on a voltage of the terminals 11 respectively. 30 be controlled.

Furthermore, suitable monitoring devices, such as, for example, voltage sensors, current sensors, temperature sensors, etc., can also be provided, which determine the state of the power converter 1 monitor and if necessary initiate a shutdown and in particular a discharge of the capacitors. For this purpose, for example, the sensor values of the monitoring devices can be evaluated by the control device. In particular, for example, when opening the circuit breaker 30 automatically discharge the capacitors 11 . 12 and 13 by closing the first and second switching elements 21 . 22 to be triggered.

2 shows a schematic representation of a block diagram for an electric power converter 2 with a filter device 1 according to a further embodiment. The circuit arrangement largely corresponds to the previously described filter device in FIG 1 , Therefore, the statements made above apply analogously to the filter device in 2 , The filter device 1 in 2 differs from the filter device described above in particular in that parallel to the first capacitor 11 a first electrical resistance 41 is arranged. The first electrical resistance 41 is thus between the first input terminal E1 and the node K are arranged. Analog is between the second input terminal E2 and the node K a second electrical resistance 42 parallel to the second capacitor 12 arranged. In the first and second electrical resistance 41 . 42 these are relatively high-resistance electrical resistors. In particular, the electrical resistance may be in the range of a few megohms. In this way flows during operation of the power converter 2 at one between the first and second input terminals E1 . E2 applied DC voltage a relatively low electric current. The electrical resistances 41 . 42 are sufficient, however, with the disconnector open 30 the first capacitor 11 and the second capacitor 12 to unload. Furthermore, via the series connection of the first and second resistor 41 . 42 also the third capacitor 13 be discharged. In this way, even a discharge of the three capacitors 11 . 12 . 13 be achieved when the first switching element 21 and the second switching element 22 are open. Thus, in the event of a faulty activation or a defect in one of the switching elements 21 . 22 nevertheless a safe discharge can be guaranteed.

3 shows a further embodiment of a power converter 2 with a filter device 1 , Also for this filter device 1 the remarks made above apply in connection with 1 and 2 , The embodiment in 3 differs from the embodiments described above in particular in that in series with the first switching element 21 and the second switching element 22 each an electrical resistance 43 . 44 is arranged. With these electrical resistors 43 . 44 it is electrical resistors with a low electrical resistance in the range of one or a few ohms or possibly also a lower value. By the series connection of an electrical resistance 43 . 44 with the respective switching element 21 . 22 can the maximum electric current through the respective switching element 21 . 22 be limited, so that the switching elements 21 . 22 not be damaged or destroyed by too high an electric current and the associated heat development.

4 shows a schematic representation of a flowchart of a method for controlling a filter device, in particular a previously described filter device for an electric power converter.

In step S1 becomes an electrical connection between the first input terminal E1 and the node K provided. In step S2 is another electrical connection between the second input terminal E2 and the node K provided. In particular, providing the electrical connection between the first input terminal E1 and the node K and the second input terminal E2 and the node K take place simultaneously. However, at least the provision of the electrical connection between the first input terminal E1 and the node K and connecting the second input terminal E2 with the node K at periods that at least partially overlap. In this way, an electrical connection between the first input terminal E1 and the second input terminal E2 by means of the two switching elements 21 . 22 be achieved. This can also be a third capacitor 13 between the first input terminal E1 and the second input terminal E2 be discharged.

In summary, the present invention relates to the discharge of capacitors at a DC input of an electric power converter. For this purpose, the Y capacitors are short-circuited at the input terminal by means of suitable switching elements. In this way, an electrical connection between the two terminals of the DC voltage terminal of the power converter is created. Thus, a DC link capacitor between the two terminals of the DC voltage terminal of the power converter can be discharged.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009022167 A1 [0003]

Claims (7)

Filter device (1) for an electric power converter (2), comprising: a first capacitor (11) disposed between a first input terminal (E1) of the power converter (2) and a node (K); a second capacitor (12) disposed between a second input terminal (E2) of the power converter (2) and the node (K); a third capacitor (13) disposed between the first input terminal (E1) and the second input terminal (E2) of the power converter (2); a first switching element (21), which is arranged between the first input terminal (E1) of the power converter (2) and the node (K) and which is adapted to provide an electrical connection between the first input terminal (E1) of the power converter (2) and to provide the node (K); and a second switching element (22), which is arranged between the second input terminal (E2) and the node (K), and which is adapted to an electrical connection between the second input terminal (E2) of the power converter (2) and the node (K ). Filter device (1) after Claim 1 comprising a control device (50) which is designed to jointly control the first switching element (21) and the second switching element (22). Filter device (1) after Claim 1 or 2 wherein the first switching element (21) and the second switching element (22) each comprise a semiconductor switching element. Filter device (1) according to one of Claims 1 to 3 with a first electrical resistor (41) arranged between the first input terminal (E1) and the node (K); and a second electrical resistance (42) disposed between the second input terminal (E2) and the node (K). Filter device (1) according to one of Claims 1 to 4 in which the filter device (1) can be coupled to a DC voltage source (3), and wherein the filter device (1) comprises a circuit breaker (30) which is designed to establish an electrical connection between the filter device (1) and the DC voltage source (3). to interrupt. Electric power converter (2) with a filter device (1) according to one of Claims 1 to 5 , Method for driving a filter device (1) for an electric power converter (2), wherein the filter device (1) comprises a first capacitor (11) arranged between a first input terminal (E1) of the power converter (2) and a node (K) is a second capacitor (12) disposed between a second input terminal (E2) of the power converter (2) and the node (K) and a third capacitor (13) connected between the first input terminal (E1) and the second input terminal (E2), the method comprising the following steps: Providing (S1) an electrical connection between the first input terminal (E1) and the node (K); and Providing (S2) a further electrical connection between the second input terminal (E2) and the node (K).

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