Control device for activating and deactivating a y-capacitor, inverter and electric drive system

Abstract

The invention relates to a circuit arrangement that makes it possible to activate or deactivate a Y-capacitor in a galvanically isolated manner and at the same test a switch state of the switch element for activating or deactivating the Y-capacitor.

Description

[0001] Description

[0002] title

[0003] Control device for activating and deactivating a Y-capacitor, power converter and electric drive system

[0004] Technical area

[0005] The present invention relates to a control device for activating and deactivating a Y capacitor, as well as a power converter and an electric drive system with such a control device.

[0006] State of the art

[0007] Although the present invention is described below in connection with an electric drive system for an electric vehicle, the invention is not limited thereto. Rather, the present invention can also be applied to any other systems in which Y capacitors are to be specifically activated or deactivated.

[0008] Electric drive systems typically include a power converter that converts an electrical voltage provided at the input into another voltage suitable for driving an electrical machine. So-called Y capacitors can be provided at the input terminals of such a power converter, with each Y capacitor being arranged between an input terminal and a reference potential.

[0009] The document DE 10 2020 121 248 A1 describes a circuit arrangement for charging an electric vehicle with switchable Y capacitors between phase connections and a neutral conductor, wherein the Y capacitors can be deactivated in a rest state of the circuit arrangement.

[0010] Disclosure of the Invention The present invention discloses a control device for activating and deactivating a Y capacitor, as well as a power converter and an electric drive system having the features of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

[0011] Accordingly, it is provided:

[0012] 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 comprises a transformer, a first control device, a second control device, and a diode. The transformer has a primary side and a secondary side. The first control device is designed to provide predetermined control pulses to 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 designed to control the semiconductor switching element using the voltage signals present at the 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.

[0013] Furthermore, it is planned:

[0014] An electrical power converter with an input terminal and a power converter circuit. The input terminal is designed to be connected to an electrical DC voltage source at a first connection point and a second connection point. The power converter circuit is designed to convert an electrical DC voltage provided at the input terminal into an AC voltage and to provide this AC voltage at an output terminal. Furthermore, a series circuit comprising a Y capacitor and a semiconductor switching element is arranged between a reference potential and the first connection point, and between the reference potential and the second connection point. Furthermore, a control device according to the invention is provided for each Y capacitor.

[0015] Finally, it is planned:

[0016] An electric drive system, in particular an electric drive system for an electric vehicle with an electric machine and an electric power converter according to the invention.

[0017] Advantages of the invention

[0018] As the capacitance of Y capacitors increases, so does the electrical energy stored in them. Especially for electric drive systems powered by a high-voltage DC source, it is essential that these capacitors be able to discharge as quickly as possible when the drive system is switched off.

[0019] Therefore, one idea of ​​the present invention is to activate Y capacitors only when they are actually needed. In this case, it is desirable to be able to reliably verify the respective switching state, ie, the activation or deactivation of the Y capacitors.

[0020] Against this background, the present invention creates a control device for activating or deactivating Y capacitors, which can easily verify the respective state of the Y capacitors. This makes it possible, on the one hand, to make the capacitance of the Y capacitors available when required, for example in order to minimize high-frequency interference. On the other hand, the capacitance of the Y capacitors can be deactivated or switched off when they are not needed. This means that no electrical energy, which could potentially pose a danger to people, is stored in the deactivated Y capacitors. In addition, the option of verifying the current state, i.e. the activation or deactivation, makes it possible toDeactivating the Y capacitors also ensures that the desired configuration is present in each case. Consequently, on the one hand, it can be ensured that the Y capacitors can also provide the necessary filtering of high-frequency interference when required, and on the other hand, it can be ensured that the Y capacitors are also reliably decoupled when they are not needed.

[0021] Thus, the diode between a terminal on the secondary side of the transformer and the node where the Y capacitor is connected to the semiconductor switching element for activating / deactivating the Y capacitor can achieve current feedback to the primary side of the transformer, which makes it possible to draw conclusions about the switching state of the semiconductor switching element on the primary side of the transformer. This allows a galvanically isolated check of the switching state of the semiconductor switching element to be implemented on the primary side of the transformer, allowing the function of the Y capacitor to be analyzed.

[0022] According to one embodiment, the first control device is designed to detect an electrical current on the primary side of the transformer and to determine a switching state of the semiconductor switching element using the detected electrical current. In particular, the control device can evaluate the electrical current while the primary side of the transformer is being subjected to the control pulses. As already explained above, the diode according to the invention between the secondary side of the transformer and the node at which the Y capacitor and semiconductor switching element are connected can achieve a current feedback on the primary side of the transformer, which allows conclusions to be drawn about the switching state of the semiconductor switching element.

[0023] According to one embodiment, the first control device is designed to detect a malfunction of the semiconductor switching element if the determined switching state of the semiconductor switching element deviates from the switching state signaled by means of the control pulses. In other words, if there is a discrepancy between the integrated result of the switching state of the semiconductor switching element and the requested switching state, this indicates a malfunction. This can be indicated by appropriate signaling, for example, an analog or digital output signal. If necessary, further measures can then be initiated, such as shutting down the system, continuing operation at reduced power or in an emergency operating mode, or similar. Furthermore, such an error can also be stored in an error memory and read out at a later time, for example in a workshop.

[0024] According to one embodiment, the control pulses each comprise a first time period and a second time period. In the first time period, the control pulses each have a predetermined first voltage level. Furthermore, the control pulses in the second time period have a voltage curve that signals the desired switching state of the semiconductor switching element. In this case, the maximum voltage level during the second time period can be lower than the voltage level during the first time period. For example, a longer pulse with a predetermined voltage level can signal a state during the second time period in which the semiconductor switching element is to be closed in order to activate the Y capacitor.Furthermore, a shorter pulse within the second time period can be used to request a switching state in which the semiconductor switching element is to be opened in order to deactivate the Y capacitor.

[0025] According to one embodiment, the control device is designed to close the semiconductor switching element of the series circuit comprising the Y capacitor and the semiconductor switching element in a first operating mode. Correspondingly, in a second operating mode, the semiconductor switching element of the series circuit comprising the Y capacitor and the semiconductor switching element can be opened. For example, the first operating mode can be set with the activated Y capacitor if another component connected to the Y capacitor, such as an electrical power converter, is active. If, however, this connected component is not active, the Y capacitor can also be deactivated. In particular, for example, in an electric vehicle, the first operating mode can be set with the activated Y capacitor if the vehicle is in a driving mode in which the vehicle's electric drive system is active.If the vehicle is parked or is being charged, for example, the Y capacitors at the input of an electrical power converter of the drive system can be deactivated.

[0026] The above embodiments and further developments can be combined with one another as desired, where appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention not explicitly mentioned above or described below with respect to the exemplary embodiments. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0027] Short description of the drawings

[0028] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0029] Fig. 1 : a basic circuit diagram of an electric drive system with a control device according to an embodiment;

[0030] Fig. 2: a schematic diagram of a control device according to an embodiment;

[0031] Fig. 3: a voltage-time diagram illustrating control pulses as they may be provided in a control device according to an embodiment; and

[0032] Fig. 4: a voltage-time diagram illustrating further control pulses as may be provided in a control device according to one embodiment. Description of Embodiments

[0033] Figure 1 shows a basic circuit diagram of an electric drive system according to one embodiment. The electric drive system comprises, for example, a power converter 2 and an electric machine 3. The electric power converter 2 can be supplied with a DC voltage on the input side at a DC voltage connection from a DC voltage source 1, for example a traction battery of an electric vehicle. The power converter 2 can convert this DC voltage, for example according to setpoint specifications, into a single-phase or multi-phase AC voltage and provide this AC voltage to the electric machine 3. If necessary, the power converter 2 can also convert the electrical AC voltage provided by the electric machine 3 in generator mode into a DC voltage in recuperation mode, which is suitable for charging the battery connected to the DC voltage connection.

[0034] Furthermore, a charging circuit 4 may be provided if necessary. By means of this charging circuit 4, the DC voltage source 1, in particular the traction battery, can be charged from an external energy source. The switching elements provided for this purpose for separating the connections between the charging circuit 4, the DC voltage source 1, and the power converter 2 are not shown in Figure 1 for clarity.

[0035] So-called Y-capacitors Cy can be provided at the DC voltage connection of the power converter 2. In this case, one such Y-capacitor Cy can be provided between each of the two DC voltage lines at the DC voltage connection of the power 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. By closing this semiconductor switching element M, the respective Y-capacitor Cy can thus be activated. Correspondingly, by opening the semiconductor switching element M, the respective Y-capacitor Cy can be deactivated.

[0036] For example, the Y-capacitors Cy can be activated by closing the semiconductor switching elements M when the power converter 2 is active, in particular when the electric drive system is in an active state. If the electric drive system is, for example, the drive system of an electric vehicle, the Y-capacitors Cy can be activated by closing the semiconductor switching elements M when the vehicle is in a driving mode. If, on the other hand, the vehicle is parked and, for example, charged, the Y-capacitors Cy can be deactivated by opening the semiconductor switching elements M. In principle, it is also possible, in addition to the activatable / deactivatable Y-capacitors Cy, to provide a further, preferably smaller capacitance in parallel to the series circuits comprising a Y-capacitor Cy and the corresponding switching element M.Thus, by activating the Y capacitors and the resulting parallel connection with the other capacitor, a large total capacitance can be achieved, while when the Y capacitor is deactivated, only the small capacitance of the other capacitor remains effective.

[0037] The semiconductor switching elements M can be controlled to open or close, for example, by means of the control device 100, which will be explained in more detail below.

[0038] Figure 2 shows a schematic diagram of a control device 100 for activating and deactivating Y capacitors Cy according to one embodiment. The control device 100 comprises a first control device 10, a second control device 20, a transformer T, and a diode D.

[0039] The first control device 10 comprises a control element 11, which generates control pulses explained in more detail below and provides them on the primary side of the transformer T.

[0040] The secondary side of the transformer T is connected to the second control device 20. In particular, the second control device 20 can comprise a voltage supply component 21 and a control component 22. The voltage supply component 21 can generate an electrical voltage from the electrical voltage provided on the secondary side of the transformer T, which is suitable for supplying the control component 22 with electrical energy. For example, the electrical voltage provided on the secondary side of the transformer T can be rectified in the voltage supply component 21 and stored in a capacitor.

[0041] The control component 22 evaluates the voltage signal provided on the secondary side of the transformer T. In particular, the control component 22 can open or close the semiconductor switching element M depending on the signal waveform of the voltage signal on the secondary side of the transformer T. For this purpose, a corresponding control signal can be provided by the control component 22 at the control terminal of the semiconductor switching element.

[0042] Furthermore, a diode D is provided between the node K, at which the Y capacitor Cy is connected to the semiconductor switching element M, and a first connection point of the secondary side of the transformer T.

[0043] In particular, an electrical resistor R can also be provided in series with this diode D. This electrical resistor R can, for example, limit or adjust the electrical current in this current path. The second connection point on the secondary side of the transformer can, for example, be connected to a reference potential.

[0044] When the semiconductor switching element M is closed, an electric current can flow through the current path with the diode D between the first connection point on the secondary side of the transformer T and the node K. This electric current causes a feedback effect on the primary side of the transformer T.

[0045] The first control device 10 includes a current sensor 12 that can detect the electrical current on the secondary side of the transformer T. The current sensor 12 can provide its sensor signal to the control element 11. Thus, the control element 11 can evaluate the sensor value of the current sensor 12 and determine the switching state of the semiconductor switching element M. Furthermore, the control element 11 can compare the determined switching state of the semiconductor switching element M with the requested switching state. If there is a discrepancy between the determined switching state and the requested switching state, a malfunction can be detected. A corresponding error message can then be signaled. For example, in such a case, the functionality of the system with the Y capacitors Cy can be restricted or completely deactivated.

[0046] Figures 3 and 4 each show voltage-time diagrams of the control pulses as they can be provided by the first control device 10, for example, on the primary side of the transformer T. Figure 3 illustrates an exemplary course of the voltage pulses for closing the semiconductor switching element M, and Figure 4 illustrates an exemplary course of the voltage pulses for opening the semiconductor switching element M.

[0047] As can be seen in Figure 3, the control pulses can be divided into two time periods t1 and t2. In the first time period t1, the control pulse can assume a predetermined first voltage value. This can ensure, for example, that a sufficient amount of electrical energy is transferred from the primary side to the secondary side of the transformer T by means of the control pulses in order to supply the second control device 20 with electrical energy. In the subsequent second time period t2, a signal can then be given about the desired switching state of the semiconductor switching element. For this purpose, for example, to close the semiconductor switching element M, a voltage pulse with a second voltage value can be output over the entire length of the second time period t2. This second voltage value can be lower than the first voltage during the first time period t1.

[0048] After outputting the voltage waveform with positive voltages described above, a voltage waveform with negative voltages of the same magnitude can then be output. This can be repeated periodically as long as the desired switching state for the semiconductor switching element M is to be maintained. Figure 4 illustrates a possible voltage waveform for opening the semiconductor switching element M. The first time period t1 with the voltage pulse of the first voltage value is identical to the voltage pulse for closing the semiconductor switching element M described above.In the subsequent second time period t2, however, only a short time period ta with the second voltage value takes place to signal the opening of the semiconductor switching element M, which is followed by a further time period tb with a voltage of approximately 0 volts. Here, too, the described voltage curve can be output alternately with positive and negative voltages.

[0049] In this way, it is possible, on the one hand, to supply the second control device 20 on the secondary side of the transformer T with electrical energy by means of the output voltage pulses and, in the process, to additionally signal the desired switching state for the semiconductor switching element M.

[0050] Due to the feedback of the electric current through the current path with the diode D, a conclusion about the switching state of the semiconductor switching element M can be drawn by measuring the current on the primary side of the transformer T.

[0051] In summary, the present invention relates to a circuit arrangement which makes it possible to activate or deactivate a Y capacitor galvanically separately and at the same time to check a switching state of the switching element for activating or deactivating the Y capacitor.

Claims

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, comprising: a transformer (T) having a primary side and a secondary side; a first control device (10) designed to provide predetermined control pulses to the primary side of the transformer (T), the control pulses being 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 designed to control the semiconductor switching element (M) using voltage signals applied to the secondary terminal of the transformer (T);and a diode (D) arranged between a terminal of the secondary side of the transformer (T) and the node (K); 2. Control device (100) according to claim 1, wherein the first control device (10) is further configured to detect an electric current on the primary side of the transformer (T) and to determine a switching state of the semiconductor switching element (M) using the detected electric current.

3. Control device (100) according to claim 2, wherein the first control device (10) is designed to detect a malfunction of the semiconductor switching element (M) if the determined Switching state of the semiconductor switching element (M) deviates from the desired switching state signaled by means of the control pulses 4. Control device [100) according to one of claims 1 to 3, wherein the control pulses each comprise a first time period (t1) and a second time period (t2), wherein the control pulses in the first time period (t1) each have a predetermined first voltage level and the control pulses in the second time period (t2) have a voltage curve which in each case signals the desired switching state of the semiconductor switching element (M).

5. An electrical power converter having an input terminal configured to be connected to a DC electrical voltage source (1) at a first terminal and a second terminal; and a power converter circuit (2) configured to convert a DC electrical voltage provided at the input terminal into an AC voltage and to provide it at an output terminal; wherein a series circuit comprising a Y capacitor (Cy) and a semiconductor switching element (M) is arranged between a reference potential and the first terminal and between the reference potential and the second terminal, and wherein a control device (100) according to one of claims 1 to 4 is provided for each Y capacitor (Cy).

6. Electrical power converter according to claim 5, wherein the control devices (100) are designed to close the semiconductor switching elements (M) of the series circuit comprising the Y capacitor (Cy) and the semiconductor switching element (M) in a first operating mode, and In a second operating mode, the semiconductor switching elements (M) of the series circuit comprising the Y capacitor (Cy) and the semiconductor switching element (M) are opened.

7. An electric drive system for an electric vehicle, comprising: an electric machine (3); and an electric power converter according to claim 5 or 6, which is designed to control the electric machine (3).

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