Overvoltage protection for a motor vehicle electrical system in the event of load shedding

Patent metadata

Field	Value
Publication number	US-2016294181-A1
Application number	US-201415037279-A
Country	US
Kind code	A1
Filing date	Nov 10, 2014
Priority date	Nov 26, 2013
Publication date	Oct 6, 2016
Grant date	—

Abstract

A method for operating a motor vehicle electrical system which includes an electric machine, and an active bridge rectifier connected to the electric machine via phase connections. After the bridge rectifier has been operated at least once in a short circuit operating mode, a determination is made, based on at least one feature of a signal which characterizes a voltage that drops between the direct voltage terminals of the bridge rectifier, whether the signal has exceeded the upper threshold value due to a cable break at at least one of the direct voltage terminals. If so, the bridge rectifier is subsequently operated in the short circuit operating mode for an extended period of time, and/or a control signal having a second switching time greater than that in the first method phase is used for controlling the active switching elements.

First claim

1 - 11 . (canceled)

12 . A method for operating a motor vehicle electrical system which includes an electric machine which is operable in a generator mode, and an active bridge rectifier which is connected to the electric machine via phase connections and which is operable in a rectifier operating mode and a short circuit operating mode, the method comprising:
in the rectifier operating mode, converting phase voltages present at the phase connections into an output voltage, outputting the output voltage at direct voltage terminals of the bridge rectifier by controlling active switching elements of the bridge rectifier; in the short circuit operating mode, short-circuiting the phase connections by controlling the active switching elements so that no output voltage is output by the bridge rectifier at the direct voltage terminals of the bridge rectifier, the short circuit operating mode being initiated as soon as a signal which characterizes a voltage that drops between the direct voltage terminals of the bridge rectifier exceeds an upper threshold value; in a first method phase, discontinuing the short circuit operating mode as soon as the signal subsequently falls below a lower threshold value, and using a control signal having a first switching time for controlling the active switching elements; after the bridge rectifier has been operated at least once in the short circuit operating mode in the first method phase, determining, based on at least one feature of the signal, whether the signal has exceeded the upper threshold value due to a cable break at at least one of the direct voltage terminals, and if so:
at least one of: i) in a second method phase, the bridge rectifier is subsequently operated in the short circuit operating mode for an extended period of time, and ii) in the second method phase, a control signal having a second, shorter switching time is used for controlling the active switching elements, in which a duration of the at least one short circuit operating mode in which the bridge rectifier has been operated in the first method phase is used as the at least one feature of the signal.

13 . The method as recited in claim 12 , wherein a lack of a voltage dip after a start of the at least one short circuit operating mode in which the bridge rectifier has been operated in the first method phase is used as the at least one feature of the signal.

14 . The method as recited in claim 12 , wherein an exceedance of a detection threshold value after a start of the at least one short circuit operating mode in which the bridge rectifier has been operated in the first method phase is used as the at least one feature of the signal.

15 . The method as recited in claim 12 , wherein in the second method phase, the bridge rectifier is operated in the short circuit operating mode for 0 s to 1.5 s.

16 . The method as recited in claim 15 , wherein in the second method phase, the bridge rectifier is operated in the short circuit operating mode for 0.5 s to 1 s.

17 . The method as recited in claim 12 , wherein in the second method phase, the bridge rectifier is operated in the short circuit operating mode for an extended period of time in such a way that the lower threshold value is reduced.

18 . The method as recited in claim 12 , wherein in the second method phase, a control signal having a second, shorter switching time is used for controlling the active switching elements, the first switching time being in a range of 10 μs to 200 μs and the second switching time being in a range of 0 μs to 20 μs.

19 . The method as recited in claim 12 , wherein the signal os filtered, a first filtering time being used in the first method phase and a second filtering time being used in the second method phase.

20 . A motor vehicle electrical system which includes an electric machine which is operable in a generator mode, and an active bridge rectifier which is connected to the electric machine via phase connections and which is operable in a rectifier operating mode and a short circuit operating mode, and which includes a control device which is configured to
in the rectifier operating mode, convert phase voltages present at the phase connections into an output voltage, the output voltage being output at direct voltage terminals of the bridge rectifier by controlling active switching elements of the bridge rectifier; in the short circuit operating mode, short-circuit the phase connections by controlling the active switching elements so that no output voltage is output by the bridge rectifier at the direct voltage terminals of the bridge rectifier; initiate the short circuit operating mode as soon as a signal which characterizes a voltage that drops between the direct voltage terminals of the bridge rectifier exceeds an upper threshold value; in a first method phase, discontinue the short circuit operating mode as soon as the signal subsequently falls below a lower threshold value, and use a control signal having a first switching time for controlling the active switching elements; and after the bridge rectifier has been operated at least once in the short circuit operating mode in the first method phase, determine, based on at least one feature of the signal, whether the signal has exceeded the upper threshold value due to a cable break at at least one of the direct voltage terminals, and if so:
at least one of: i) in a second method phase, subsequently operate the bridge rectifier in the short circuit operating mode for an extended period of time, and ii) in the second method phase, use a control signal having a second, shorter switching time for controlling the active switching elements, in which a duration of the at least one short circuit operating mode in which the bridge rectifier has been operated in the first method phase is used as the at least one feature of the signal.

21 . A control device for a motor vehicle electrical system, the motor vehicle electrical system including an electric machine which is operable in a generator mode, and an active bridge rectifier which is connected to the electric machine via phase connections and which is operable in a rectifier operating mode and a short circuit operating mode, the control device configured to:
in the rectifier operating mode, convert phase voltages present at the phase connections into an output voltage, the output voltage being output at direct voltage terminals of the bridge rectifier by controlling active switching elements of the bridge rectifier; in the short circuit operating mode, short-circuit the phase connections by controlling the active switching elements so that no output voltage is output by the bridge rectifier at the direct voltage terminals of the bridge rectifier; initiate the short circuit operating mode as soon as a signal which characterizes a voltage that drops between the direct voltage terminals of the bridge rectifier exceeds an upper threshold value; in a first method phase, discontinue the short circuit operating mode as soon as the signal subsequently falls below a lower threshold value, and use a control signal having a first switching time for controlling the active switching elements; and after the bridge rectifier has been operated at least once in the short circuit operating mode in the first method phase, determine, based on at least one feature of the signal, whether the signal has exceeded the upper threshold value due to a cable break at at least one of the direct voltage terminals, and if so:
at least one of: i) in a second method phase, subsequently operate the bridge rectifier in the short circuit operating mode for an extended period of time, and ii) in the second method phase, use a control signal having a

Assignees

• Bosch Gmbh Robert

Inventors

• Otte Christopher
• Mehringer Paul

Classifications

• H02M7/219

  in a bridge configuration · CPC title

• H02P9/006

  Means for protecting the generator by using control (control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10) · CPC title

• H02H7/067 Primary

  on occurrence of a load dump (control on sudden change of load H02P9/10) · CPC title

• H02P3/22

  by short-circuit or resistive braking · CPC title

• H02M7/30

  by dynamic converters · CPC title