Prediction of available torque and power from battery-powered traction motor

• US 6,831,429 B2
• Filed: 03/10/2003
• Issued: 12/14/2004
• Est. Priority Date: 03/10/2003
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Fu, Zhenxing
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US10/384,962
• Publication Number:
  US 20040178756A1
• Time in Patent Office: 645 Days
• Field of Search: 318/139, 318/430-434, 318/459, 318/471, 318/478-479, 388/903, 388/934, 180/65.2
• US Class Current: 318/139
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60L 15/025 using field orientation; Vector control; Direct Torque Control [DTC]
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/525 Temperature of converter or components thereof
• CPC Class Codes: B60L 2260/56 Temperature prediction, e.g. for pre-cooling
• CPC Class Codes: B60L 50/60 using power supplied by batteries in combination with fuel cells B60L50/75
• CPC Class Codes: B60L 58/20 having different nominal voltages
• CPC Class Codes: B60W 20/11 using model predictive control [MPC] strategies, i.e. control methods based on models predicting performance utilising navigation and traffic information in the control strategy B60W20/12
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: B60W 50/0097 Predicting future conditions
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• 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

Available torque output from a battery-powered traction motor system in a vehicle is estimated, wherein the system includes a high-voltage battery coupled to a traction motor by an inverter, wherein the inverter is controlled in response to a torque/speed command within an inverter controller, and wherein the system further includes a DC-to-DC converter coupled to the high-voltage battery to provide a reduced voltage to charge a low-voltage battery. Battery operating conditions of the high-voltage battery are determined including available battery power and battery voltage. Traction motor operating conditions including a flux linkage and other electrical parameters are determined. The battery information including voltage, current, and internal resistance is transformed into synchronous coordinates. An available quadrature current corresponding to the maximum available torque is determined in response to the traction motor operating conditions and the battery voltage in the synchronous coordinates. The available quadrature current is clamped in response to predetermined clamping limits. A first estimated available torque is determined in response to the clamped available quadrature current and the traction motor operating conditions. A high-voltage power usage is determined including power consumed in the DC-to-DC converter, power loss in the DC-to-DC converter, and power loss in the traction motor and inverter. An angular speed of the traction motor is measured. A second estimated available torque is determined in response to the available battery power, the high-voltage power usage, and the angular speed. A lesser one of said first and second estimated available torques is selected as the available torque output from the battery-powered traction motor system.

Claims

1. A method of estimating available torque output from a battery-powered traction motor system in a vehicle, said system including a high-voltage battery coupled to a traction motor by an inverter, said inverter controlled in response to a torque/speed command within an inverter controller, said system further including a DC-to-DC converter coupled to said high-voltage battery to provide a reduced voltage to charge a low-voltage battery, said method comprising the steps of:

determining battery operating conditions of said high-voltage battery

including available battery power and battery voltage;

determining traction motor operating conditions including electrical

parameters of said fraction motor;

transforming said battery operating conditions into synchronous coordinates;

determining an available quadrature current corresponding to a maximum available torque in response to said electrical parameters and said battery voltage in said synchronous coordinates;

clamping said available quadrature current in response to predetermined clamping limits to prevent said traction motor system from exceeding maximum current and voltage limits, to protect said traction motor and said inverter from excessive thermal heating, and to protect said high voltage battery from excessive charging or discharging;

determining a first estimated available torque in response to said clamped available quadrature current and said traction motor operating conditions;

determining high-voltage power usage including power consumed in said DC-to-DC converter, power loss in said DC-to-DC converter, and power loss in said traction motor and inverter;

measuring an angular speed of said traction motor;

determining a second estimated available torque in response to said available battery power, said high-voltage power usage, and said angular speed; and

selecting a lesser one of said first and second estimated available torques as said available torque output.

2. The method of claim 1 further providing an estimated available power output, said method including the step of:

determining said estimated available power output in response to multiplying said available torque output by said angular speed.

3. The method of claim 1 wherein said available battery power is comprised of a maximum output power in a discharge mode of said high-voltage battery and wherein said available torque output is comprised of an estimated maximum torque output that can be produced by said battery-powered traction motor system in said discharge mode.

4. The method of claim 1 wherein said available battery power is comprised of a maximum input power in a charge mode of said high-voltage battery and wherein said available torque output is comprised of an estimated maximum torque load that can be consumed by said battery-powered traction motor system in said charge mode.

5. The method of claim 1 wherein said available battery power is comprised of a transient capacity of said high-voltage battery and wherein said available torque output is a corresponding transient torque capacity.

6. The method of claim 1 wherein said available battery power is comprised of a substantially continuous capacity of said high-voltage battery and wherein said available torque output is a corresponding continuous torque capacity.

7. The method of claim 1 wherein said battery operating conditions further include battery current and battery internal resistance and wherein said transforming step includes transforming said battery internal resistance into said synchronous coordinates.

8. The method of claim 1 wherein said traction motor operating conditions further include motor temperature and magnetic saturation, and wherein said method further comprises the step of:

estimating a motor stator resistance, a motor inductance, and a flux linkage in response to said motor temperature and magnetic saturation using a motor thermal saturation model.

9. The method of claim 8 wherein said available quadrature current is determined in a system model in response to a current command, said flux linkage, said battery voltage, said motor stator resistance, said motor inductance, and said angular speed.

10. The method of claim 1 wherein said traction motor operating conditions further include motor temperature, and wherein said clamping limits are determined in response to a current command and said motor temperature.

11. The method of claim 1 wherein said traction motor operating conditions further include motor magnetic saturation, and wherein said first estimated available torque is determined in response to said clamped available quadrature current, a flux linkage, and a motor inductance.

12. The method of claim 1 wherein said vehicle is a hybrid electric vehicle including an internal combustion engine coupled to said battery-powered traction motor system.

13. A torque estimator for an electric vehicle having a battery-powered traction motor system wherein said system includes a high-voltage battery coupled to a traction motor by an inverter, wherein said inverter is controlled in response to a torque/speed command from an inverter controller, and wherein said system further includes a DC-to-DC converter coupled to said high-voltage battery to provide a reduced voltage to charge a low-voltage battery, said torque estimator comprising:

a synchronous coordinate battery model for transforming a value proportional to a measured voltage and internal resistance of said high-voltage battery into a synchronous battery voltage and internal resistance;

a motor thermal saturation model for generating a flux linkage signal in response to a quadrature current limit and a temperature of said traction motor;

a battery/inverter/motor model for generating an available quadrature current signal corresponding to a maximum available torque in response to a current command, said flux linkage signal, and said synchronous battery voltage;

a clamp for generating a clamped quadrature current signal in response to said available quadrature current signal and predetermined clamping limits to prevent said traction motor system from exceeding maximum current and voltage limits, to protect said traction motor and said inverter from excessive thermal heating, and to protect said high voltage battery from excessive charging or discharging;

a first torque estimator for generating a first estimated available torque in response to said clamped quadrature current signal and said flux linkage;

a power usage estimator for generating a power usage signal in response to power consumed in said DC-to-DC converter, power loss in said DC-to-DC converter, and power loss in said traction motor and inverter;

a second torque estimator for generating a second estimated available torque in response to said power usage signal, an available battery power of said high-voltage battery, and an angular speed of said traction motor; and

a selector for selecting a lesser one of said first and second estimated available torques as an estimated available torque value.

14. The torque estimator of claim 13 further comprising:

a multiplier for generating an estimated available power value in response to said estimated available torque value and said angular speed.

15. The torque estimator of claim 13 wherein said available battery power is comprised of a maximum output power in a discharge mode of said high-voltage battery and wherein said estimated available torque value is comprised of an estimated maximum torque output that can be produced by said battery-powered traction motor system in said discharge mode.

16. The torque estimator of claim 13 wherein said available battery power is comprised of a maximum input power in a charge mode of said high-voltage battery and wherein said estimated available torque value is comprised of an estimated maximum torque load that can be consumed by said battery-powered traction motor system in said charge mode.

17. The torque estimator of claim 13 wherein said available battery power is comprised of a transient capacity of said high-voltage battery and wherein said estimated available torque value corresponds to a transient torque capacity.

18. The torque estimator of claim 13 wherein said available battery power is comprised of a substantially continuous capacity of said high-voltage battery and wherein said estimated available torque value corresponds to a continuous torque capacity.

19. An electric vehicle comprising:

a battery-powered traction motor system including a high-voltage battery coupled to a traction motor by an inverter, wherein said inverter is controlled in response to a torque/speed command from an inverter controller;

a low-voltage battery;

a DC-to-DC converter coupled to said high-voltage battery to provide a reduced voltage to charge said low-voltage battery; and

a torque estimator comprising;

a synchronous coordinate battery model for transforming a value proportional to a measured voltage and internal resistance of said high-voltage battery into a synchronous battery voltage and internal resistance;

a motor thermal saturation model for generating a flux linkage signal in response to a quadrature current limit and a temperature and magnetic saturation of said traction motor;

a battery/inverter/motor model for generating an available quadrature current signal corresponding to a maximum available torque in response to said torque/speed command, said flux linkage signal, and said synchronous battery voltage;

a clamp for generating a clamped quadrature current signal in response to said available quadrature current signal and predetermined clamping limits to prevent said traction motor system from exceeding maximum current and voltage limits, to protect said traction motor and said inverter from excessive thermal heating, and to protect said high voltage battery from excessive charging or discharging;

a first torque estimator for generating a first estimated available torque in response to said clamped quadrature current signal and said flux linkage signal;

a power usage estimator for generating a power usage signal in response to power consumed in said DC-to-DC converter, power loss in said DC-to-DC converter, and power loss in said traction motor and inverter;

a second torque estimator for generating a second estimated available torque in response to said power usage signal, an available battery power of said high-voltage battery, and an angular speed of said traction motor; and

a selector for selecting a lesser one of said first and second estimated available torques as an estimated available torque value.

20. The electric vehicle of claim 19 further comprising:

an internal combustion engine coupled to said traction motor system.