High-voltage system energy management in drive mode, function

P08.00-2035-81

Function requirements, general

 Terminal 15 ON

 The terminal status of terminal 15 is transmitted by the SAM control unit via the engine compartment CAN to the powertrain control unit.

High-voltage system energy management in driving mode, general points

The high-voltage system energy management in driving mode secures high-voltage on-board electrical system stability.

During implementation of the request, for example over the accelerator pedal sensor, a lowest possible energy consumption is sought. The goal is to achieve the highest possible range of the vehicle.

The high-voltage system energy management driving mode function comprises the following partial functions:

 Function sequence for determination of the output capacity of the high-voltage system

 Function sequence for electric drive system operation under load

 Function sequence for electric drive system decel mode

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Function sequence for determination of the output capacity of the high-voltage system

The requests made by the driver, for example over the accelerator pedal sensor, should be implemented, wherever possible, one to one. A lowest possible energy consumption is sought in the process. Continuous monitoring serves to determine the current power output capacity and the therefore possible following implementation of the requests from the driver.

The following control units are involved:

– battery management system control unit

– Powertrain control unit

– power electronics control unit

 The powertrain control unit takes on the master function.

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The following signals from the battery management system control unit are read in by the powertrain control unit via the electric vehicle CAN:

- permissible cell charging voltage

– discharge current

– discharge voltage

- current maximum charge level of high-voltage battery (G5)

- current maximum charge level of high-voltage battery

- actual current of the high-voltage battery

- actual voltage of the high-voltage battery

The following signals from the power electronics control unit are read in by the powertrain control unit via the electric vehicle CAN:

- operating mode and temperature of the DC/DC converter in the power electronics control unit

- temperature of the electric motor drive

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The following signals are read in directly by the powertrain control unit:

- accelerator pedal position from accelerator pedal sensor

- coolant temperature from coolant temperature sensor 1 drive (B11) for controlling the thermal management

 Further to the above-mentioned signals, signals are sent between the control units which concern the thermal management. These signal also serve to determine the current current power output capacity and the therefore possible following implementation of the requests from the driver.

All transmitted and read in signal which concern the thermal management are described in the separate partial function "thermal management function".

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Function sequence for electric drive system operation under load

The electric motor drive is connected over direct lines with the power electronics control unit.

The high voltage supply for the electric motor drive takes place over the high-voltage on-board electrical system.

The high voltage is stored in the high-voltage battery as a direct voltage and passes over the high voltage adapter plate fuse box (F34/6) to the power electronics control unit. The direct voltage is converted there into an AC voltage and fed to the electric motor drive.

Actuation of the electric motor drive over the power electronics control unit and evaluation of its feedback take place by the powertrain control unit.

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The following signals from the powertrain control unit are read in by the power electronics control unit via the electric vehicle CAN:

- ideal engine rpm curve

- engine torque request

- minimal engine deceleration torque

- electric motor drive rotation direction request

- electric motor drive dynamic intervention request 1

- electric motor drive dynamic intervention request 2

- electric motor drive dynamic intervention request 3

- electric motor drive nominal rotational speed

- electric motor drive discharge request

- electric motor drive operating mode

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The following signals from the power electronics control unit are read in by the powertrain control unit via the electric vehicle CAN:

- operating mode and temperature of the DC/DC converter in the power electronics control unit

- rotor position of the electric motor drive

- current torque of the electric motor drive

- current rotational speed and direction of rotation of the electric motor drive

- temperature of the electric motor drive

Function sequence for electric drive system decel mode

The electric motor drive acts as an alternator in decel mode and thus generates the energy which it passes as an AC voltage over the high-voltage on-board electrical system to the power electronics control unit.

The generated AC voltage is converted there into a direct voltage and led to the high-voltage battery in the high-voltage on-board electrical system over the high voltage adapter plate fuse box.

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The high-voltage battery can be charged in this way during driving mode.

The electric motor drive is connected over direct lines with the power electronics control unit.

Actuation of the electric motor drive over the power electronics control unit and evaluation of its feedback take place by the powertrain control unit.

The following signals from the powertrain control unit are read in by the power electronics control unit via the electric vehicle CAN:

- minimal engine deceleration torque

- electric motor drive rotation direction request

- electric motor drive operating mode

- electric motor drive discharge request

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The following signals from the power electronics control unit are read in by the powertrain control unit via the electric vehicle CAN:

- rotor position of the electric motor drive

- current recuperation torque of the electric motor drive

- current rotational speed and direction of rotation of the electric motor drive

- temperature of the electric motor drive

- current recuperations voltage and recuperation current strength