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DE-102025114249-B3 - Method and system for integrity testing of a high-voltage system of an electrically powered motor vehicle

DE102025114249B3DE 102025114249 B3DE102025114249 B3DE 102025114249B3DE-102025114249-B3

Abstract

Method and system (10) for integrity testing of a high-voltage system (11) of an electrically driven motor vehicle, in which electrical energy is transferred between a high-voltage bus (13) and an electric machine (14) by means of an inverter (12) via an electrically effective intermediate circuit energy storage device (15) for the temporary storage of at least a portion of the electrical energy, wherein in a freewheeling operating state of the electric machine, in which it induces an electric current ( I1 ), the induced current is supplied to the intermediate circuit energy storage device by means of the inverter, and an electric current ( I2 ) flowing between the intermediate circuit energy storage device and the high-voltage bus is alternately interrupted and allowed by means of an electronic switching element (17) controlled by a control device (16) with at least one predeterminable switching frequency, in order to determine an electrically effective impedance (18) on the bus side at the inverter for the at least one switching frequency, wherein the freewheeling operating state of the electric machine is maintained as long as the bus-side impedance is within a permissible impedance range; otherwise, the electric machine is actively short-circuited by means of the inverter and the freewheeling operating state is terminated.

Inventors

  • Martin HÜTTL
  • Wolfgang Poisel

Assignees

  • AUDI AKTIENGESELLSCHAFT

Dates

Publication Date
20260513
Application Date
20250410

Claims (10)

  1. Method for integrity testing of a high-voltage system (11) of an electrically driven motor vehicle, in which electrical energy is transferred by means of an inverter (12) between a high-voltage bus (13) for supplying the motor vehicle with a high-voltage direct current and an electric machine (14) for the electric drive of the motor vehicle, with an electrically effective intermediate circuit energy storage device (15) for the temporary storage of at least a portion of the electrical energy, wherein in a freewheeling operating state of the electric machine (14), in which it induces an electric current ( I1 ), the induced current ( I1 ) is supplied to the intermediate circuit energy storage device (15) by means of the inverter (12), and an electric current ( I2 ) flowing between the intermediate circuit energy storage device (15) and the high-voltage bus (13) is alternately interrupted and allowed by means of an electronic switching element (17) controlled by a control unit (16) with at least one predeterminable switching frequency. is used to determine an electrically effective impedance (18) on the bus side of the inverter (12) for at least one switching frequency, whereby the freewheeling operating state of the electric machine (14) is maintained as long as the determined bus-side impedance (18) is within a predetermined permissible impedance range, and otherwise the electric machine (14) is actively short-circuited by means of the inverter (12) and the freewheeling operating state is terminated.
  2. Procedure according to Claim 1 , in which the induced current (I 1 ), the current (I 2 ) flowing between the DC link energy storage (15) and the high-voltage bus ( 13 ) and an DC link voltage (U 1 ) applied to the DC link energy storage (15) are each recorded by means of current measuring instruments (A) or voltage measuring instruments (V) for at least one switching frequency and corresponding current and voltage measurement values are provided to the control unit (16), on the basis of which the electrically effective impedance (18) on the bus side at the inverter (12) is determined.
  3. Procedure according to Claim 1 or 2 , in which the electrically effective impedance (18) on the bus side of the inverter (12) is determined separately for several predeterminable switching frequencies.
  4. Method according to one of the preceding claims, in which, by comparison with impedance values stored in a loop-up table characterizing the high-voltage system (11), it is determined whether the electrically effective impedance (18) on the bus side of the inverter (12) is within the permissible impedance range or not.
  5. Method according to one of the preceding claims, wherein the at least one switching frequency is selected from a megahertz range.
  6. Method according to one of the preceding claims, wherein the control device (16) is further configured to control power switching elements (22) of the inverter (12) for converting the high-voltage direct current into a machine alternating current.
  7. System (10) for integrity testing of a high-voltage system (11) of an electrically driven motor vehicle, comprising an inverter (12) for the controlled transfer of electrical energy between a high-voltage bus (13) for the electrical supply of the motor vehicle with a high-voltage direct current and an electric machine (14) for the electric drive of the motor vehicle with an electrically effective intermediate of a DC link energy storage device (15) for the temporary storage of at least a part of the electrical energy to be transferred, wherein the inverter (12) is configured to supply the induced current ( I1 ) to the DC link energy storage device (15) in a freewheeling operating state of the electric machine (14) in which it induces an electric current ( I1 ), further comprising a control device (16) which is configured to alternately interrupt and allow an electric current (I 2 ) flowing between the intermediate circuit energy storage device (15) and the high-voltage bus (13) during the freewheeling operating state of the electric machine (14) by means of an electronic switching element (17) with at least one predetermined switching frequency, in order to determine an electrically effective impedance (18) on the bus side of the inverter (12) for the at least one switching frequency and to maintain the freewheeling operating state of the electric machine (14) as long as the determined bus-side impedance (18) is within a predetermined permissible impedance range, and otherwise to actively short-circuit the electric machine (14) by means of the inverter (12) and to end the freewheeling operating state.
  8. System according to Claim 7 , in which the switching element (17) is part of the inverter (12).
  9. System according to Claim 7 or 8 , in which the control unit (16) is part of the inverter (12).
  10. system according to one of the Claims 7 until 9 , in which the electrical machine (14) is a permanent magnet synchronous machine (PMSM).

Description

The invention relates to a method and a system for integrity testing of a high-voltage system of an electrically powered motor vehicle. In a high-voltage vehicle, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a fuel cell electric vehicle (FCEV), or a pure electric vehicle (EV), a high-voltage bus typically serves to distribute and provide high voltage within the vehicle. This is used, for example, to supply electrical energy to an electric motor for propelling the vehicle and other high-voltage devices (HV devices) connected to the high-voltage bus. Such vehicles may have a high-voltage battery (HV battery) that feeds the high-voltage bus and provides the necessary high voltage. High voltage is defined as a direct current voltage greater than 60 V, particularly greater than 200 V, e.g., 400 V or 800 V up to approximately 1500 V. In contrast, low voltage is defined as an electrical voltage less than or equal to 60 V, e.g., 6 V, 12 V, 24 V, 48 V, or 60 V. In high-voltage vehicles, a safe state of the high-voltage system (HV system) must be established in the event of a fault. Such a state can be achieved by opening battery contactors to disconnect the HV battery from the high-voltage bus and/or via a so-called freewheeling of the electric motor or an active short circuit (ACS). For reasons of coasting capability, freewheeling is usually preferred over engaging an automatic locking system (ACS). However, freewheeling may only be used if it is ensured that the vehicle's high-voltage system is undamaged, i.e., that all high-voltage lines are correctly connected to the high-voltage components and that there are no broken wires. The testing of the high-voltage (HV) system is typically performed by evaluating an interlock network or by centrally evaluating an HV voltage measurement from each HV device. The result of the integrity test by a central HV coordinator (HVK) is usually transmitted via bus communication to the HV devices and also to an inverter (e.g., pulse inverter, PWR), which controls the safe state of the electrical machine. However, if the high-voltage bus or the HV system is not connected to the HV battery with closed battery contactors, a central evaluation of the HV system's integrity is not possible. Furthermore, bus communication between the HV bus and the inverter may fail, for example, after a crash. This means that the centrally generated integrity status of the HV system does not reach the inverter and cannot be evaluated. This loss of information from the inverter means that, for HV safety reasons, the electric machine may only operate in freewheeling mode up to a limited, low induced voltage and must enter freewheeling mode if this limit is exceeded. The permissible limit is the touch-hazardous voltage, typically 60 VDC, which must not be exceeded. A switching device for switching an electrical connection of an electrical energy storage device to a vehicle's power grid is known from the prior art, as described, for example, in the publication DE 10 2016 109 862 A1 The document describes a switching device with parallel conductors in which protective switching elements are arranged, wherein at least one of the protective switching elements is designed as a semiconductor switch. By controlled actuation of the semiconductor switch, a DC link capacitor can be pre-charged before the energy storage device is fully connected to the power grid, in order to avoid current spikes. The known solution thus serves for the safe switching and pre-charging of a vehicle's high-voltage power grid. Against this background, the invention is based on the objective of providing solutions for the integrity testing of a high-voltage system of an electrically driven motor vehicle, which maximize the possibilities of a safe freewheeling of an electric machine in the event of an operational malfunction of the motor vehicle. This problem is solved by a method having the features of claim 1 and by a system having the features of claim 7. Further particularly advantageous embodiments of the invention are disclosed in the respective dependent claims. It should be noted that the features listed individually in the claims can be combined with one another in any technically meaningful way (even across category boundaries, for example between method and apparatus) and demonstrate further embodiments of the invention. The description characterizes and further specifies the invention, particularly in connection with the figures. It should also be noted that the conjunction “and/or” used herein, which stands between two features and links them together, is always to be interpreted in such a way that in a first embodiment of the object according to the invention only the first feature may be present, in a second embodiment only the second feature may be present, and in a third embodiment both the first and the second feature may be present. The use of the term "approximately" herein is intende