Control device for activating and deactivating Y capacitor, converter and electric drive system

Abstract

The invention relates to a circuit arrangement capable of activating or deactivating a Y capacitor in an electrically isolated manner while checking the switching state of a switching element for activating or deactivating the Y capacitor.

Description

Technical Field

[0001] The present invention relates to a control device for activating and deactivating a Y capacitor, and a converter and an electric drive system having such a control device. Background Art

[0002] Although the present invention will be described below in conjunction with an electric drive system for an electric vehicle, the present invention is not limited thereto and can in principle also be applied to any other system requiring targeted activation or deactivation of Y capacitors.

[0003] Electric drive systems typically include a converter, which converts the voltage provided at the input into another voltage suitable for operating the electric motor. So-called Y capacitors can be provided at the input terminals of such converters, with each Y capacitor being arranged between the input terminals and a reference potential.

[0004] Document DE 10 20 20 121 248 A1 describes a circuit arrangement for charging an electric vehicle, which has switchable Y capacitors located between the phase terminals and the neutral conductor, wherein the Y capacitors can be deactivated in an idle state of the circuit arrangement. Summary of the Invention

[0005] The invention discloses a control device for activating and deactivating a Y-capacitor, as well as a 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] Based on this, it is proposed that:

[0007] A control device for activating and deactivating a Y capacitor, wherein the Y capacitor is arranged between a voltage supply line and a node, and a semiconductor switching element for activating and deactivating the Y capacitor is arranged between the node and a reference potential. The control device includes a transformer, a first control device, a second control device, and a diode. The transformer includes a primary side and a secondary side. The first control device is configured to provide predetermined control pulses on the primary side of the transformer. The control pulses are adapted to signal a desired switching state of the semiconductor switching element. The second control device is electrically coupled to the secondary side of the transformer. Furthermore, the second control device is configured to control the semiconductor switching element using a voltage signal applied to a secondary terminal of the transformer. The diode is arranged between a first terminal of the secondary side of the transformer and the node. The second terminal of the secondary side of the transformer can be connected to a reference potential.

[0008] In addition, it is proposed that:

[0009] A power converter includes input terminals and a converter circuit. The input terminals are configured to be connected to a DC voltage source at a first connection point and a second connection point. The converter circuit is configured to convert a DC voltage provided at the input terminals into an AC voltage and provide the AC voltage at an output terminal. Furthermore, a series circuit consisting of a Y capacitor and a semiconductor switching element is disposed between a reference potential and the first connection point, and between the reference potential and the second connection point, respectively. Furthermore, a control device according to the present invention is provided for each Y capacitor.

[0010] Finally, it is proposed that:

[0011] An electric drive system, in particular an electric drive system for an electric vehicle, comprises an electric machine and a power converter according to the invention.

[0012] Advantages of the invention

[0013] As the capacity of the Y capacitors increases, the energy stored in them also increases. Especially for electric drive systems powered by high-voltage DC power supplies, these capacitors need to be discharged as quickly as possible when the drive system is shut down.

[0014] Therefore, one idea of ​​the present invention is to activate the Y capacitor only when it is actually needed. Here, it is desirable to be able to reliably verify the corresponding switching state, ie the activation or deactivation of the Y capacitor.

[0015] Against this background, the present invention provides a control device for activating and deactivating Y capacitors, which can verify the corresponding state of the Y capacitors in a simple manner. Thus, on the one hand, the capacity of the Y capacitors can be provided when needed, for example, to minimize the influence of high-frequency interference. On the other hand, when the capacity of the Y capacitors is not needed, they can be deactivated or switched off. In this way, no electrical energy that could pose a danger to personnel is stored in the deactivated Y capacitors. In addition, since the current state (i.e., activation or deactivation of the Y capacitors) can be verified, it can also be ensured that the desired configuration exists in each case. Thus, on the one hand, it can be ensured that the Y capacitors can also provide the required filtering of high-frequency interference influences when needed, and on the other hand, it can be ensured that the Y capacitors can also be reliably decoupled when not needed.

[0016] By providing diodes between the terminals of the transformer's secondary side and the node at which the Y capacitor is connected to the semiconductor switching element used to activate / deactivate the Y capacitor, current feedback can be implemented on the transformer's primary side. This allows the switching state of the semiconductor switching element to be inferred on the transformer's primary side. This allows for electrically isolated testing of the switching state of the semiconductor switching element on the transformer's primary side, allowing analysis of the function of the Y capacitor.

[0017] According to one embodiment, the first control device is configured to detect the current in the primary side of the transformer and use the detected current to determine the switching state of the semiconductor switching element. In particular, the control device can analyze the current during the application of control pulses to the primary side of the transformer. As previously mentioned, by providing a diode according to the present invention between the secondary side of the transformer and the node at which the Y capacitor and the semiconductor switching element are interconnected, current feedback can be generated on the primary side of the transformer, which enables the switching state of the semiconductor switching element to be inferred.

[0018] According to one embodiment, the first control device is configured to detect a semiconductor switching element fault if the determined switching state of the semiconductor switching element does not correspond to the switching state signaled by the control pulse. In other words, a discrepancy between the integrated result of the switching state of the semiconductor switching element and the requested switching state indicates a fault. This can be indicated by a corresponding signal (e.g., an analog or digital output signal). If necessary, further measures can be taken based on this, such as shutting down the system, continuing operation at reduced power, or initiating an emergency operating mode. Furthermore, such a fault can optionally be stored in a fault memory and retrieved at a later time (e.g., in a repair shop).

[0019] According to one embodiment, the control pulses each include a first time period and a second time period. The control pulses each have a predetermined first voltage level during the first time period. Furthermore, the control pulses each have a voltage waveform (voltage profile) during the second time period, which voltage waveform indicates a desired switching state of the semiconductor switching element. The maximum voltage level during the second time period can be lower than the voltage level during the first time period. For example, during the second time period, a longer pulse having a preset voltage level can be used to signal a state in which the semiconductor switching element should be closed to activate the Y capacitor. Furthermore, during the second time period, a shorter pulse can be used to request a switching state in which the semiconductor switching element should be opened to deactivate the Y capacitor.

[0020] According to one embodiment, the control device is configured to close the semiconductor switching element in the series circuit consisting of the Y capacitor and the semiconductor switching element in a first operating mode. Correspondingly, in a second operating mode, the semiconductor switching element in the series circuit consisting of the Y capacitor and the semiconductor switching element can be disconnected. For example, when other components connected to the Y capacitor (such as a power converter) are activated, a first operating mode with an activated Y capacitor can be set. Conversely, if the connected components are not activated, the Y capacitor can also be deactivated. For example, in an electric vehicle, when the vehicle is in driving mode (in which the vehicle's electric drive system is activated), a first operating mode with an activated Y capacitor can be set. If the vehicle is stopped or, for example, is being charged, in this case, the Y capacitor at the input of the power converter of the drive system can be deactivated.

[0021] The above-described designs and improvements can be combined in any manner where appropriate. Other designs, improvements, and embodiments of the present invention also include combinations of features of the present invention described above or below with respect to the exemplary embodiments, not explicitly mentioned. In particular, those skilled in the art will also consider various aspects to be improvements or supplements to the corresponding basic form of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features and advantages of the present invention will be described below with reference to the accompanying drawings, wherein:

[0023] Figure 1 : shows a principle circuit diagram of an electric drive system having a control device according to one embodiment;

[0024] Figure 2 : shows a principle circuit diagram of a control device according to one embodiment;

[0025] Figure 3 : shows a voltage-time diagram for illustrating a control pulse, which can be provided in a control device according to one embodiment; and

[0026] Figure 4 : Shows a voltage-time diagram for illustrating further control pulses that can be provided in a control device according to one embodiment. DETAILED DESCRIPTION

[0027] Figure 1The schematic diagram of an electric drive system according to one embodiment is shown. The electric drive system includes, for example, a converter 2 and a motor 3. The power converter 2 can be supplied with a DC voltage at its input terminals from a DC voltage source 1 (e.g., the traction battery of an electric vehicle). The converter 2 can convert the DC voltage into a single-phase or multi-phase AC voltage according to preset target values ​​and supply this AC voltage to the motor 3. If necessary, the converter 2 can also convert the AC voltage provided by the motor 3 in generator mode into a DC voltage suitable for charging a battery connected to the DC voltage terminals during regenerative operation.

[0028] Furthermore, a charging circuit 4 can be provided if necessary. With the aid of this charging circuit 4, the DC voltage source 1 (in particular the traction battery) can be charged from an external energy source. Figure 1 Any switching elements provided for disconnecting the connection between the charging circuit 4 , the DC voltage source 1 and the converter 2 are not shown.

[0029] So-called Y-capacitors Cy can be provided at the DC voltage terminals of the converter 2. In this case, such Y-capacitors Cy can each be provided between two DC voltage lines at the DC voltage terminals of the converter 2 and a reference potential. Furthermore, a switching element, in particular a semiconductor switching element M, can be provided between each Y-capacitor Cy and the reference potential. Closing the semiconductor switching element M activates the corresponding Y-capacitor Cy. Similarly, opening the semiconductor switching element M deactivates the corresponding Y-capacitor Cy.

[0030] For example, when the converter 2 is activated, in particular when the electric drive system is in an active state, the Y capacitor Cy can be activated by closing the semiconductor switching element M. If the electric drive system is, for example, the drive system of an electric vehicle, then when the vehicle is in driving mode, the Y capacitor Cy can be activated by closing the semiconductor switching element M. Conversely, if the vehicle is stopped and, for example, being charged, the Y capacitor Cy can be deactivated by disconnecting the semiconductor switching element M. In principle, in addition to the activatable / deactivatable Y capacitor Cy, if necessary, another (preferably smaller capacity) capacitor can be arranged in parallel next to each series circuit consisting of a Y capacitor Cy and a corresponding switching element M. In this way, by activating the Y capacitor and thereby forming a parallel circuit with the other capacitor, a larger total capacity can be obtained, and when the Y capacitor is deactivated, only the small capacity of the other capacitor is effective.

[0031] The semiconductor switching element M can be actuated to open or close, for example, by means of a control device 100 , which will be described in greater detail below.

[0032] Figure 2FIG2 shows a schematic circuit diagram of a control device 100 for activating and deactivating a Y-capacitor Cy according to an embodiment. The control device 100 includes a first control means 10 , a second control means 20 , a transformer T, and a diode D.

[0033] The first control device 10 comprises a control element 11 which generates control pulses, which will be described in detail below, and supplies them to the primary side of the transformer T.

[0034] The secondary side of the transformer T is connected to a second control device 20. The second control device 20 may include, in particular, a power supply component 21 and an actuation component 22. The power supply component 21 can generate a voltage suitable for powering the actuation component 22 from the voltage provided by the secondary side of the transformer T. For example, to this end, the voltage provided by the secondary side of the transformer T can be rectified in the power supply component 21 and stored in a capacitor.

[0035] The control component 22 evaluates the voltage signal provided by the secondary side of the transformer T. In particular, the control component 22 can open or close the semiconductor switching element M based on the signal waveform of the voltage signal on the secondary side of the transformer T. To this end, the control component 22 can provide a corresponding control signal at the control port of the semiconductor switching element.

[0036] Furthermore, a diode D is provided between node K (at which the Y capacitor Cy and the semiconductor switching element M are connected) and the first connection point of the secondary side of the transformer T. In particular, a resistor R can be provided in series with the diode D. This resistor R can, for example, limit or control the current in the current path. The second connection point of the secondary side of the transformer can, for example, be connected to a reference potential.

[0037] When the semiconductor switch element M is closed, current may flow through a current path having a diode D between the first connection point of the secondary side of the transformer T and the node K. This current may generate feedback to the primary side of the transformer T.

[0038] A current sensor 12 is provided in the first control device 10. This current sensor detects the current on the secondary side of the transformer T. The current sensor 12 provides its sensing signal to the control element 11. The control element 11 then evaluates the sensor value of the current sensor 12 and determines the switching state of the semiconductor switching element M. Furthermore, the control element 11 compares the determined switching state of the semiconductor switching element M with the requested switching state. If a discrepancy exists between the determined switching state and the requested switching state, a fault is detected. A corresponding fault reporting signal is then issued. In this case, for example, the functionality of the system with the Y-capacitor Cy can be limited or the system can be completely deactivated.

[0039] Figure 3 and Figure 4The voltage-time diagrams of the control pulses provided by the first control device 10, for example, on the primary side of the transformer T are shown. Figure 3 shows an example waveform of a voltage pulse for closing a semiconductor switching element M, Figure 4 An example waveform of a voltage pulse for turning off the semiconductor switching element M is shown.

[0040] like Figure 3 As shown, the control pulse can be divided into two time periods t1 and t2. During the first time period t1, the control pulse can exhibit a predetermined first voltage value. For example, this can ensure that sufficient electrical energy is transferred from the primary side of the transformer T to the secondary side via the control pulse to supply electrical energy to the second control device 20. Subsequently, during the subsequent second time period t2, a signal regarding the desired switching state of the semiconductor switching element can be issued. For example, to close the semiconductor switching element M, a voltage pulse having a second voltage value can be output throughout the second time period t2. This second voltage value can be lower than the first voltage value during the first time period t1.

[0041] After the above-mentioned voltage waveform with a positive voltage is output, a voltage waveform with a negative voltage having the same value may be output next. If the desired switching state of the semiconductor switching element M is to be maintained, this process may be repeated periodically.

[0042] Figure 4 A possible voltage waveform for turning off the semiconductor switching element M is shown. Here, the first time period t1 of the voltage pulse having the first voltage value is identical to the voltage pulse described above for turning on the semiconductor switching element M. Subsequently, in the subsequent second time period t2, only a short time period ta having the second voltage value follows to signal the turning off of the semiconductor switching element M, followed by a further time period tb at a voltage of approximately 0 volts. The voltage waveform can also be output alternately with positive and negative voltages.

[0043] In this way, on the one hand, the second control device 20 on the secondary side of the transformer T can be supplied with electrical energy by means of the output voltage pulses, while at the same time a signal regarding the desired switching state of the semiconductor switching element M can be issued.

[0044] Due to the current feedback via the current path having the diode D, the switching state of the semiconductor switching element M can be inferred by measuring the current on the primary side of the transformer T.

[0045] In summary, the present invention relates to a circuit arrangement that can activate or deactivate a Y capacitor in an electrically isolated manner while checking the switching state of a switching element used to activate or deactivate the Y capacitor.

Claims

1. A control device (100) for activating and deactivating a Y capacitor (Cy), wherein The Y capacitor (Cy) is arranged between a voltage supply line and a node (K), and a semiconductor switching element (M) for activating and deactivating the Y capacitor (Cy) is arranged between the node (K) and a reference potential, the control device comprising: A transformer (T) having a primary side and a secondary side; a first control device (10) configured to provide predetermined control pulses at the primary side of the transformer (T), wherein the control pulses are adapted to signal a desired switching state of the semiconductor switching element (M); a second control device (20) electrically coupled to the secondary side of the transformer (T) and configured to control the semiconductor switching element (M) using a voltage signal applied to the secondary side terminal of the transformer (T); and A diode (D) is arranged between a terminal of the secondary side of the transformer (T) and the node (K).

2. The control device (100) according to claim 1, wherein The first control device (10) is further configured to detect the current on the primary side of the transformer (T) and determine the switching state of the semiconductor switch element (M) using the detected current.

3. The control device (100) according to claim 2, wherein: The first control device (10) is designed to detect a fault of the semiconductor switching element (M) if the determined switching state of the semiconductor switching element (M) does not correspond to an expected switching state signaled by the control pulse.

4. The control device (100) according to any one of claims 1 to 3, wherein: The control pulses respectively include a first time period (t1) and a second time period (t2), wherein the control pulses respectively have a predetermined first voltage level in the first time period (t1), and the control pulses respectively have a voltage waveform in the second time period (t2), and the voltage waveforms respectively indicate the desired switching state of the semiconductor switching element (M).

5. Power converter, having: an input terminal configured to be connected to a DC voltage source (1) at a first connection point and a second connection point; and a converter circuit (2) configured to convert a DC voltage provided at the input terminal into an AC voltage and provide the AC voltage at an output terminal; in, A series circuit consisting of a Y capacitor (Cy) and a semiconductor switching element (M) is arranged between the reference potential and the first connection point and between the reference potential and the second connection point, respectively, and A control device (100) according to any one of claims 1 to 4 is provided for each Y capacitor (Cy).

6. The power converter according to claim 5, wherein: The control device (100) is configured to close the semiconductor switching element (M) in a series circuit consisting of a Y capacitor (Cy) and a semiconductor switching element (M) in a first operating mode, and to open the semiconductor switching element (M) in a series circuit consisting of the Y capacitor (Cy) and the semiconductor switching element (M) in a second operating mode.

7. Electric drive systems for electric vehicles, having: a motor (3); and The power converter according to claim 5 or 6, being configured to control the electric machine (3).

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