Fault-tolerant operation of hybrid electric vehicle

• US 9,834,206 B1
• Filed: 03/29/2017
• Issued: 12/05/2017
• Est. Priority Date: 03/29/2017
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Yang, Shuitao, Zhou, Yan, Newman, Kevin L., Chen, Lihua, Xu, Fan, Alam, Mohammed Khorshed
• Primary Examiner(s): Gurari, Erez
• Application Number:
  US15/472,718
• Time in Patent Office: 251 Days
• CPC Class Codes: B60K 6/34 characterised by the absence of energy storing means
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60L 2210/42 Voltage source inverters
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/441 Speed
• CPC Class Codes: B60L 2240/526 Operating parameters
• CPC Class Codes: B60L 2240/527 Voltage
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 50/13 using AC generators and AC motors
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• CPC Class Codes: B60L 58/21 having the same nominal voltage
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 20/50 Control strategies for responding to system failures, e.g. for fault diagnosis, failsafe operation or limp mode
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/083 Torque
• CPC Class Codes: B60W 2510/244 : Charge state
• CPC Class Codes: B60W 2710/0644 : Engine speed
• CPC Class Codes: B60W 2710/0666 : Engine torque
• CPC Class Codes: B60W 2710/083 : Torque
• CPC Class Codes: H02M 1/007 : Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/008 : Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 1/325 : with means for allowing continuous operation despite a fault, i.e. fault tolerant converters
• CPC Class Codes: H02M 7/5387 : in a bridge configuration
• CPC Class Codes: H02M 7/53875 : with analogue control of three-phase output
• 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 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y10S 903/907 : Electricity storage, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/91 : Orbital, e.g. planetary gears
• CPC Class Codes: Y10S 903/93 : Conjoint control of different elements

Abstract

A hybrid drive system has a battery and a combustion engine for energy sources. The system has a traction motor, a generator, a variable voltage converter (VVC), a motor inverter, a generator inverter, a bus coupling the VVC to the inverters, and a controller. The controller regulates engine speed, motor torque, and generator torque. The engine speed is determined according to a driver torque demand. In normal conditions, 1) the controller regulates the engine speed by modifying a generator torque command, and 2) the bus voltage is regulated using the VVC and battery. When the controller detects a fault in which the battery and VVC become unavailable for regulating the bus voltage, then the controller regulates a motor inverter power output to match a sum of a generator inverter power output and an estimated power loss of the inverters in order to regulate the bus voltage.

Claims

1. A hybrid drive system comprising:

a DC power source;

an internal combustion engine;

a traction motor;

a generator;

a variable voltage converter (VVC) selectably coupled to the power source;

a motor inverter;

a generator inverter;

a bus coupling an output of the VVC to the inverters; and

a controller regulating an engine speed, a motor torque, and a generator torque;

wherein the controller detects a fault in which the power source and VVC are unavailable for regulating a bus voltage on the bus; and

wherein upon detecting the fault, the controller regulates a motor inverter power output to match a sum of a generator inverter power output and an estimated power loss of the inverters.

2. The hybrid drive system of claim 1 wherein the controller further regulates the motor inverter power output according to an error between the bus voltage and a predetermined voltage.

3. The hybrid drive system of claim 1 wherein the DC power source is a battery pack, wherein the regulated engine speed is determined according to a state of charge of the battery pack when the fault is not detected, and wherein the controller regulates the engine speed without regard to the state of charge of the battery pack when the fault is detected.

4. A hybrid drive system comprising:

a DC power source;

an internal combustion engine;

a traction motor;

a generator;

a variable voltage converter (VVC) selectably coupled to the power source;

a motor inverter;

a generator inverter;

a bus coupling an output of the VVC to the inverters; and

a controller regulating an engine speed, a motor torque, and a generator torque;

wherein the controller detects a fault in which the power source and VVC are unavailable for regulating a bus voltage on the bus; and

wherein upon detecting the fault, the controller generates a motor torque command according to A) an error between the bus voltage and a predetermined voltage, and B) a generator inverter power output.

5. The hybrid drive system of claim 4 wherein the controller further generates the motor torque command during detection of the fault according to an estimated power loss of the inverters.

6. The hybrid drive system of claim 4 wherein the DC power source is a battery pack, wherein the regulated engine speed is determined according to a state of charge of the battery pack when the fault is not detected, and wherein the controller regulates the engine speed without regard to the state of charge of the battery pack when the fault is detected.

7. A DC balancing control in a hybrid vehicle having a motor inverter and a generator inverter, comprising:

a voltage regulator providing a control signal according to a difference between a voltage at an inverter bus and a reference voltage when the bus is isolated from a vehicle battery; and

a combiner generating a motor inverter power target according to a difference between the control signal and a power output from the generator inverter.

8. The control of claim 7 wherein the combiner generates the motor inverter power target according to a difference between the control signal and a sum of the power output from the generator inverter and an estimated power loss of the inverters.

9. The control of claim 7 further comprising a command generator converting the power target to a motor torque command using a motor speed.

10. A method of controlling a hybrid drive system having a battery, an internal combustion engine, a traction motor, a generator, a variable voltage converter (VVC) selectably coupled to the battery, a motor inverter, a generator inverter, a bus coupling an output of the VVC to the inverters, and a controller, the method comprising the steps of:

detecting whether the battery and VVC are available for regulating a voltage on the bus;

when the battery and VVC are available, then performing the steps of;

determining an engine speed command according to a driver torque command, an actual vehicle speed, and a battery state of charge;

regulating engine speed to the engine speed command by modifying a generator torque command for the generator inverter; and

determining a motor torque command for the motor inverter according to the driver torque command and the generator torque command; and

when the battery and VVC are not available, then performing the steps of;

determining an engine speed command according to the driver torque command and the actual vehicle speed, without regard to the battery state of charge;

regulating engine speed to the engine speed command by modifying a generator torque command for the generator inverter; and

regulating the motor torque command to obtain a motor power output that matches a power loss of the inverters plus a generator power output that results from the modified generator torque command.

11. The method of claim 10 wherein the matching motor power output is determined by the steps of:

using a voltage regulator to generate a control signal according to a difference between a voltage at the bus and a reference voltage with the bus being isolated from the battery; and

generating a motor inverter power target according to a difference between the control signal and the generator power output.

12. The method of claim 11 wherein the motor inverter power target is further determined according to the power loss of the inverters.