High-voltage system with active discharge of x-capacitors

Abstract

The invention relates to a high-voltage system (1) for an electrified motor vehicle, comprising: - a high-voltage on-board electrical system (7) which is connected to HV terminals (HV+, HV-) and has a high-voltage consumer (8) and an X-capacitor (Cx) connected in parallel, - a high-voltage battery (2) which is connected to the HV terminals (HV+, HV-) and has a battery system (3) comprising two battery units (3a, 3b), a switching device (4) which is connected between the battery units (3a, 3b), and a main switching unit (5a, 5b) which is connected between the respective battery unit (3a, 3b) and the respective HV terminal (HV+, HV-), and a second main switching unit (5b) which is connected between the second battery unit (3b) and the second HV terminal (HV-), - at least one first electronics component (6a) which is connected to the first HV terminal (HV+) and the switching device (4), and at least one second electronics component (6b) which is connected to the second HV terminal (HV-) and the switching device (4), and - a control device (9) which, in order to actively discharge X-capacitors (Cx, Cxa, Cxb) of the high-voltage on-board electrical system (7) and the electronics components (6a, 6b), is designed to open the main switching units (5a, 5b) in order to disconnect the battery system (3), to interconnect the X-capacitors (Cxa, Cxb) of the electronics components (6a, 6b) by means of the switching device (4) and thus to connect them in parallel to the high-voltage consumer (8) and to transfer the high-voltage consumer (8) to an operating mode which increases the power loss and reduces the energy (E1, E2) of the X-capacitors (Cx, Cxa, Cxb).

Description

[0001] High-voltage system with active discharge of X-capacitances

[0002] The invention relates to a high-voltage system for an electrified motor vehicle comprising HV connections, a high-voltage electrical system connected to the HV connections, and a high-voltage battery connected to the HV connections. The invention also relates to a motor vehicle with a high-voltage system.

[0003] The focus here is on high-voltage systems for electrified vehicles, such as electric vehicles, hybrid vehicles, or fuel cell vehicles. These high-voltage systems typically include a high-voltage battery designed to supply high-voltage components, such as an electric motor, to the vehicle's high-voltage electrical system. This electrical system may also include a charging port, allowing the high-voltage battery to be connected to an external charging station. The high-voltage battery comprises a battery system, which may, for example, consist of several interconnected battery units. This battery system is typically connected to the high-voltage potential-carrying terminals of the high-voltage battery via main switching units, such as high-voltage contactors.These main switching units allow the high-voltage electrical system to be switched off by isolating the battery system, particularly galvanically, from the high-voltage electrical system.

[0004] The high-voltage electrical system also contains capacitances, which are either intentionally introduced, for example in the form of interference suppression capacitors or DC link capacitors, or parasitically, for example due to the design. An X-capacitor is connected to the high-voltage terminals of the high-voltage system when the main switching units are closed. In addition, a discharge resistor is usually provided, connected in parallel to the X-capacitor, and designed to discharge it, for example, after the main switching units are opened. However, discharging the X-capacitor via the discharge resistor takes a considerable amount of time, making the discharge resistor unsuitable for rapid or emergency discharge of the X-capacitor, which must be completed quickly.Furthermore, the high-voltage system may contain additional electronic components whose internal X-capacitances also need to be discharged and therefore often have their own discharge circuits. These discharge circuits increase the cost, weight, and space requirements of the electronic components and thus of the high-voltage system.

[0005] The object of the present invention is to provide a simple, cost-effective, space-saving and fast discharge for X capacities of a high-voltage system of a motor vehicle.

[0006] This problem is solved according to the invention by a high-voltage system and a motor vehicle with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description, and the figures.

[0007] A high-voltage system according to the invention for an electrified motor vehicle comprises HV connections and a high-voltage electrical system with at least one high-voltage consumer and with an X-capacitance connected in parallel to the at least one high-voltage consumer. The high-voltage system also includes a high-voltage battery, a battery system with two battery units connected between the HV connections, a switching device connected between the battery units, a first main switching unit connected between the first battery unit and the first HV connection, and a second main switching unit connected between the second battery unit and the second HV connection. The switching device is designed to connect the battery units in series in a first switching state, in parallel in a second switching state, and to disconnect them from each other in a third switching state.The main switching units are designed to connect the battery system to the HV terminals in a closed state and to disconnect it from the HV terminals in an open state.

[0008] Furthermore, the high-voltage system comprises at least one first electronic component connected to the first HV terminal and the switching device and connected in parallel to the first battery unit and the first main switching unit, and at least one second electronic component connected to the second HV terminal and the switching device and connected in parallel to the second battery unit and the second main switching unit.Furthermore, the high-voltage system includes a control unit designed for the active discharge of the X-capacitance of the high-voltage electrical system and the X-capacitances of the electronic components, to put the main switching units into the open state for switching off the battery system, to transfer the switching device for series or parallel connection of the electronic components into the first or second switching state, and thus to connect the connected X-capacitances of the electronic components in parallel to the at least one high-voltage consumer and to transfer the at least one high-voltage consumer into an operating mode that increases power loss and reduces the energy of the X-capacitances.

[0009] The invention also relates to an electrified motor vehicle with a high-voltage system according to the invention. The high-voltage electrical system of the high-voltage system comprises at least one high-voltage component, which is designed, in particular, as an electric drive motor for the motor vehicle. Furthermore, the high-voltage electrical system comprises the X-capacitance, which is connected in parallel to the at least one high-voltage component. The X-capacitance can encompass all parasitic and non-parasitic capacitances that are connected between the high-voltage terminals on the electrical system side and thus have no connection to ground potential. Such a non-parasitic X-capacitance can, for example, be a DC link capacitor.

[0010] The high-voltage battery is a rechargeable high-voltage energy storage device and functions as a traction battery, supplying the electric drive motor with electrical energy. The high-voltage battery system comprises two battery units or battery packs. Each battery unit contains a network of battery cells and provides a high voltage, for example, 400 V, between its positive and negative terminals. The battery units can be connected via the switching device. To connect the battery units in series, the switching device can be switched to the first switching state, in which the negative terminal of the first battery unit is connected to the positive terminal of the second battery unit. In this configuration, one positive terminal of the battery system is connected to the positive terminal of the first battery unit, and one negative terminal of the battery system is connected to the negative terminal of the second battery unit.In this configuration, the output voltage of the battery system, applied between the positive and negative terminals, corresponds to the sum of the high-voltage voltages of the individual battery units, for example, 800 V. Such a series connection of the battery units is advantageous, for example, for HPC charging or ultra-fast charging of the high-voltage battery, as well as for ferry operation of the vehicle, in which the drive engine provides torque.

[0011] To connect the battery units in parallel, the switching device can be switched to the second switching state, in which the positive and negative terminals of the battery units are electrically connected. The positive terminal of the battery system is connected to the connected positive terminals of the battery units, and the negative terminal of the battery system is connected to the connected negative terminals of the battery units. In this state, the output voltage of the battery system corresponds to the respective high-voltage voltage of the battery units, for example, 400 V. The 400 V operation is used primarily for backward-compatible charging at 400 V charging stations. In a third switching state, the so-called neutral position, the battery units are disconnected from each other.

[0012] The switching device can be designed as a switching matrix with several switches, which can be moved into specific switching positions to provide the three switching states. In particular, the switching device is designed as an integrated component with at least one electromagnetic switching unit, the working contact of which can be moved by the control unit into three different positions to provide the three switching states.

[0013] The battery system, with its individual battery unit connections, can be connected to the high-voltage (HV) terminals via the main switching units. Each main switching unit includes a contactor or HV relay. The first main switching unit is connected in series with the first battery unit, and the second main switching unit is connected in series with the second battery unit. When the first main switching unit is closed, the positive terminal of the battery system is connected to the first HV terminal, and when the second main switching unit is closed, the negative terminal of the battery system is connected to the second HV terminal. When the main switching units are open, the positive and negative terminals are galvanically isolated from their respective HV terminals.The main switching units can be arranged together with the battery system in a housing of the high-voltage battery and connected to output terminals of the high-voltage battery. These output terminals can be formed, for example, by a connector, such as an HV connector, which is located in a housing wall of the high-voltage battery and can be connected to input terminals of the high-voltage components via connecting lines, such as an HV cable. A positive-pole output terminal of the high-voltage battery, a positive-pole connecting line, and a positive-pole input terminal of the high-voltage component are at a first HV potential, thus forming the first HV connection.A negative terminal output connection of the high-voltage battery, a negative terminal connecting line and a negative terminal input connection of the high-voltage component are at a second HV potential and thus form the second HV connection.

[0014] The high-voltage system also includes two electronic components, one connected to the switching device and the other to one of the HV terminals, thus connecting them in parallel to the respective series circuit of battery unit and main switching unit. The electronic components are preferably DC-DC converters. For example, the DC-DC converters are connected in parallel to the input side of the respective battery unit and the respective main switching unit, and their output side can be connected to a low-voltage electrical system to convert the high-voltage voltage provided by the battery units into a low-voltage voltage for supplying the low-voltage electrical system. The DC-DC converters can, for example, form a single unit with the high-voltage battery and be located, for instance, in an electronics housing attached to the high-voltage battery casing.The DC / DC converters can also be part of an on-board charger for the high-voltage electrical system and be connected on the input side to a charging port of the high-voltage electrical system and on the output side in parallel to the respective battery unit and the respective main switching unit.

[0015] The electronic components possess internal X-capacitances. These internal X-capacitances, as well as the high-voltage system's X-capacitance, must be discharged within a predetermined time period under certain circumstances, such as after a vehicle accident, for maintenance work on the high-voltage system, or in the event of improper intervention in the high-voltage system. The active discharge of the high-voltage system's X-capacitance is achieved via the parallel-connected high-voltage component. First, the main switching units are opened to disconnect the battery system and prevent the battery units from discharging via the high-voltage component. To utilize the high-voltage component for discharging the internal X-capacitances of the electronic components, the electronic components are connected in series or parallel, and the series or parallel connection is then connected in parallel with the high-voltage component.For this purpose, the switching device is switched to the first or second switching state, which connects both the battery units disconnected from the HV terminals by means of the open main switching units and the electronic components connected in parallel but still connected to the HV terminals despite the open main switching units. This allows energy from the internal X-capacitances of the electronic components, as well as from the vehicle electrical system's X-capacitance, to flow via the HV terminals to the high-voltage component, which converts the energy into power loss, such as waste heat. This discharges the X-capacitances and thus brings the high-voltage system into a safe state. After the active discharge is complete, the control unit can switch the device to the third switching state and disconnect the battery units.

[0016] It proves advantageous if the control device is designed to operate the electric drive motor in a power-loss-increasing mode such that it does not generate any torque. In this operating mode, which can also be called trimming mode, the electric drive motor is operated without generating any torque to propel the vehicle. The vehicle is stationary in this operating mode. The trimming mode can be provided, for example, by supplying the energy of the X-capacitances to the stator windings of the electric drive motor's stator in the form of a field-generating current. This field-generating current is converted into power loss in the stator windings.

[0017] The control unit may be designed to receive a signal from the vehicle's high-voltage interlock and then actively discharge the X-capacitances. The high-voltage interlock monitors the correct connection of plugs in the high-voltage system to prevent electrical hazards caused by unintentional, improper, or otherwise unavoidable disconnection of an HV plug. Such disconnection could occur when a service disconnect plug is pulled, for example, by maintenance personnel, or when a rescue disconnect plug is activated, for example, by rescue personnel in the event of a vehicle accident. This disconnection of the HV plug is detected by the high-voltage interlock, which then transmits a signal to the control unit.Based on this signal, the control unit initiates active discharge within a predetermined time period, for example, within a few seconds. The embodiments and advantages presented with reference to the high-voltage system according to the invention apply accordingly to the motor vehicle according to the invention.

[0018] Further features of the invention will become apparent from the claims, the figure, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown in the figure alone, can be used not only in the combinations specified, but also in other combinations or individually. The invention will now be explained in more detail with reference to a preferred embodiment and the drawing.

[0019] Figure 1 shows a circuit diagram of a high-voltage system 1 for an electrified motor vehicle. The high-voltage system 1 comprises a high-voltage battery 2 with a battery system 3. The battery system 3 includes a first battery unit 3a and a separate second battery unit 3b. Each of the battery units 3a, 3b has a connection of battery cells BZ. The battery units 3a, 3b can be connected in series by means of a switching device 4 of the high-voltage battery 2 by switching the switching device 4 into a first switching state Z1. By switching the switching device 4 into a second switching state Z2, the battery units 3a, 3b can be connected in parallel, and by switching the switching device 4 into a third switching state Z3, the battery units 3a, 3b can be disconnected from each other. The switching device 4 is designed here as an integrated switching unit.Furthermore, the high-voltage battery 2 has two main switching units 5a and 5b, which can, for example, be configured as HV contactors. A first switching unit 5a is connected between the first battery unit 3a and a first HV terminal HV+ of the high-voltage system 1. A second switching unit 5b is connected between the second battery unit 3b and a second HV terminal HV- of the high-voltage system 1. By means of the main switching units 5a and 5b, the battery units 3a and 3b, and thus the entire battery system 3, can be disconnected from the HV terminals HV+ and HV-.

[0020] A first electronic component 6a is connected in parallel to the series circuit consisting of the first main switching unit 5a and the first battery unit 3a. A second electronic component 6b is connected in parallel to the series circuit consisting of the second main switching unit 5b and the second battery unit 3b. The electronic components 6a and 6b are specifically designed as DC-DC converters for converting a high-voltage voltage U1, U2 provided by the respective battery units 3a and 3b into a low-voltage voltage for the vehicle's low-voltage electrical system. The electronic components 6a and 6b each have an internal X-capacitance Cxa and Cxb, respectively.

[0021] The high-voltage system 1 also includes a high-voltage electrical system 7, which is also connected to the HV terminals HV+ and HV- and which includes at least one high-voltage load 8. This high-voltage load 8 is, in particular, an electric drive motor M, which is supplied with energy from the high-voltage battery 2 to provide torque. In a torque-providing operating mode of the drive motor M, the battery units 3a and 3b are connected in series, in particular by means of the switching device 4. The high-voltage electrical system 7 also includes an X-capacitance Cx, which is connected in parallel to the electric drive motor M at the two HV terminals HV+ and HV-. The X-capacitance Cx is, in particular, an intermediate circuit capacitor ZKK of the high-voltage electrical system 7.

[0022] In an emergency, for example in the event of a vehicle accident, or for maintenance work, the X-capacities Cxa, Cxb, Cx should be discharged quickly. For this purpose, a control unit 9 of the high-voltage system 1 receives a trigger signal, for example from an HV interlock of the high-voltage system 1, and first opens the main switching units 5a, 5b to disconnect the battery system 3 from the HV terminals HV+, HV- and to de-energize the high-voltage electrical system 7. Subsequently, the switching device 4 is transferred by the control device 9 to the first switching state Z1 or held in the first switching state Z1, by which the electronic components 6a, 6b connected to the HV terminals HV+, HV- and thus the X-capacitances Cxa, Cxb are connected in series. Alternatively, the electronic components 6a, 6b and thus the X-capacitances Cxa, Cxb can also be connected in parallel.For this purpose, the switching device 4 is switched to the second switching state Z2 by means of the control device 9. This connects the interconnected X-capacitances Cxa, Cxb, as well as the X-capacitance Cx, in parallel to at least one high-voltage load 8. This high-voltage load 8 is switched by the control device 9 to a power-loss-increasing, inefficient operating mode, in which the high-voltage load 8 converts energy E1, E2 stored in the X-capacitances Cx, Cxa, Cxb into power loss. In the case of the electric drive motor M, for example, the control device 9 controls it such that the energy E1, E2 of the X-capacitances Cx, Cxa, Cxb is supplied to the electric motor M in the form of a field-generating current only. After the energy E1, E2 has dissipated, the control device 9 can switch the switching device 4 to the third switching state Z3.

Claims

Patent claims 1. High-voltage system (1) for an electrified motor vehicle, comprising: - HV connections (HV+, HV-), - a high-voltage electrical system (7) connected to the HV terminals (HV+, HV-) with at least one high-voltage consumer (8) and an X-capacitance (Cx) connected in parallel to the at least one high-voltage consumer (8), - a high-voltage battery (2) connected to the HV terminals (HV+, HV-) comprising a battery system (3) with two battery units (3a, 3b), a switching device (4) connected between the battery units (3a, 3b), a first main switching unit (5a) connected between the first battery unit (3a) and the first HV terminal (HV+), and a second main switching unit (5b) connected between the second battery unit (3b) and the second HV terminal (HV-), wherein the switching device (4) is designed to connect the battery units (3a, 3b) in series in a first switching state (Z1), in parallel in a second switching state (Z2), and to disconnect them from each other in a third switching state (Z3), and wherein the main switching units (5a, 5b) are designed to connect the battery system (3) to the HV terminals (HV+, HV-) in a closed state and in to separate an open state from the HV connections (HV+, HV-), - at least one first electronic component (6a) connected in parallel to the first battery unit (3a) and the first main switching unit (5a) to the first HV terminal (HV+) and the switching device (4), and at least one second electronic component (6b) connected in parallel to the second battery unit (3b) and the second main switching unit (5b) to the second HV terminal (HV-) and the switching device (4), and - a control device (9) designed for actively discharging the X-capacitance (Cx) of the high-voltage electrical system (7) and X-capacitances (Cxa, Cxb) of the electronic components (6a, 6b) to switch the main switching units (5a, 5b) off the battery system (3) into the open state, to switch the switching device (4) for series or parallel connection of the electronic components (6a, 6b) into the first or second switching state (Z1, Z2) and thus to connect the connected X-capacitances (Cxa, Cxb) of the electronic components (6a, 6b) in parallel to the at least one high-voltage consumer (8) and to discharge the at least one to convert high-voltage consumers (8) into an operating mode that increases power loss and reduces the energy (E1, E2) of the X-capacities (Cx, Cxa, Cxb).

2. High-voltage system (1) according to claim 1, characterized in that the electronic components (6a, 6b) are DC-DC converters.

3. High-voltage system (1) according to claim 2, characterized in that the DC voltage converters are connected on the input side in parallel to the respective battery unit (3a, 3b) and the respective main switching unit (5a, 5b) and can be connected on the output side to a low-voltage on-board network for converting the high-voltage voltage (U1, U2) provided by the battery units (3a, 3b) into a low-voltage voltage for supplying the low-voltage on-board network.

4. High-voltage system (1) according to claim 2 or 3, characterized in that the DC voltage converters are part of an on-board charger of the high-voltage electrical system and can be connected on the input side to a charging port of the motor vehicle and are connected on the output side in parallel to the respective battery unit and the respective main switching unit.

5. High-voltage system (1) according to one of the preceding claims, characterized in that the at least one high-voltage consumer (8) is an electric drive machine (M) for driving the motor vehicle.

6. High-voltage system (1) according to claim 5, characterized in that the control device (9) is designed to control the electric drive machine (M) in the power loss-increasing operating mode in such a way that it does not generate any torque.

7. High-voltage system (1) according to one of the preceding claims, characterized in that the control device (9) is designed to receive a signal of a high-voltage interlock of the high-voltage system (1) and thereupon initiate the active discharge of the X- To carry out capacities (Cx, Cxa, Cxb).

8. High-voltage system (1) according to one of the preceding claims, characterized in that the switching device (4) is designed as an integrated component with at least one electromagnetic switching unit, the working contact of which can be moved into three different positions to provide the three switching states (Z1, Z2, Z3).

9. Motor vehicle with a high-voltage system (1) according to one of the preceding claims.

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