Battery current limiter for a high voltage battery pack in a hybrid electric vehicle powertrain

• US 6,727,670 B1
• Filed: 12/12/2002
• Issued: 04/27/2004
• Est. Priority Date: 12/12/2002
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Grabowski, John Robert, Degner, Michael W.
• Primary Examiner(s): Leykin, Rita
• Application Number:
  US10/248,035
• Time in Patent Office: 502 Days
• Field of Search: 318/432, 318/139, 701/22, 320/121
• US Class Current: 318/432
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A battery current limiter and current-limiting method for a battery system and an electric motor in a hybrid automotive vehicle powertrain. The battery current limiter monitors measured battery current and torque commands. A modified current is developed to take a predetermined current margin into account. The modified current reduces battery current in a closed loop fashion simultaneously with a reduction in commanded torque by a feed-forward torque value.

Claims

1. A control method for limiting battery current in an electromotive powertrain for a vehicle, the powertrain including a high voltage battery system in an electric power circuit for an electric drive motor system and a vehicle controller that is responsive to a commanded power input signal, the method comprising the steps of:

monitoring battery system conditions including battery current, voltage, temperature, maximum current limit and state of charge;

delivering to the vehicle controller the monitored conditions;

developing a torque command and delivering it to the electric drive motor system whereby electric driving power for the vehicle is developed;

developing a feed-forward torque signal that is a function of commanded torque, maximum current limit and a current marginal value equal to a calibrated difference between maximum current and measured current, and delivering the feed-forward torque signal to the vehicle controller whereby a modified torque signal is delivered to the electric drive motor system, the modified torque signal being an estimate of the amount of torque reduction needed to prevent the commanded torque from exceeding a torque corresponding to the maximum current limit.

4. The method set forth in claim 1 wherein the step of developing a feed-forward torque signal includes calculating the feed-forward torque signal in accordance with the algorithm:

$T_{\mathrm{ff}}=T_{\mathrm{cmd}}·<br><br>\left[\frac{I_{\max }}{I_{\mathrm{mod}}}-1\right],$

where

T_ff=torque feed-forward;

T_cmd=commanded torque;

I_max=maximum current;

I_mod=modified current.

2. A control method for limiting battery current in an electromotive powertrain for a vehicle, the powertrain including a high voltage battery system in an electric power circuit for an electric drive, and a vehicle controller that is responsive to a commanded power input signal, the method comprising the steps of:

monitoring battery system conditions including battery current, voltage, temperature, maximum current limit and state of charge;

developing a torque commanded and delivering it to the electric drive motor system whereby electric driving power for the vehicle is developed;

developing a summation of a measured battery current and a calibrated marginal current to obtain a modified battery current;

developing a feed-forward torque signal that is a function of commanded torque, maximum current limit and modified battery current, and delivering the feed-forward torque signal to the vehicle controller whereby a modified limited torque signal is delivered to the electric drive motor, the modified torque signal being an estimate of the reduction in torque that is needed to prevent the modified battery current from exceeding the maximum current limit.

5. The method set forth in claim 2 wherein the step of developing a feed-forward torque signal includes calculating the feed-forward torque signal in accordance with the algorithm:

$T_{\mathrm{ff}}=T_{\mathrm{cmd}}·<br><br>\left[\frac{I_{\max }}{I_{\mathrm{mod}}}-1\right],$

where

T_ff=torque feed-forward;

T_cmd=commanded torque;

I_max=maximum current;

I_mod=modified current.

3. A battery current limiter for an electromotive powertrain for a vehicle, the powertrain having an electric drive, a vehicle powertrain controller with a commanded torque input, a high voltage battery system, the current limiter comprising:

a battery current sensor;

a maximum current sensor;

a sensor for determining a current marginal value for a given sensed maximum current;

a first comparator for developing a modified current value that is equal to measured battery current increased by the current marginal value;

a second comparator for developing a comparator signal equal to the difference between a maximum current and the modified current;

a proportional integral controller having a comparator signal input for developing a limited torque signal; and

a power plant control for developing a feed-forward torque signal which is added to the output of the proportional integral controller whereby the modified current value is prevented in a closed-loop fashion from exceeding the maximum current.

6. The battery current limiter set forth in claim 3 wherein the power plant control includes a means for developing a feed-forward torque signal which is added to the output of the proportional integral controller in accordance with the algorithm:

$T_{\mathrm{ff}}=T_{\mathrm{cmd}}·<br><br>\left[\frac{I_{\max }}{I_{\mathrm{mod}}}-1\right],$

where

T_ff=torque feed-forward;

T_cmd=commanded torque;

I_max=maximum current;

I_mod=modified current.