SYSTEM AND METHOD FOR ENERGY MANAGEMENT IN AN ELECTRIC VEHICLE

• US 20130138279A1
• Filed: 11/29/2011
• Published: 05/30/2013
• Est. Priority Date: 11/29/2011
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Shi, Ruijie, King, Robert Dean, Gemin, Paul Robert, Berry, Irene Michelle, Espinel Porras, Augusto
• Granted Patent: US 9,290,107 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60L 1/00 Supplying electric power to auxiliary equipment of vehicles circuit arrangements for charging batteries H02J7/00
• CPC Class Codes: B60L 2210/30 AC to DC converters
• CPC Class Codes: B60L 2210/40 DC to AC converters
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 2240/642 Slope of road
• CPC Class Codes: B60L 2250/26 by pedal actuation
• CPC Class Codes: B60L 50/40 using propulsion power supplied by capacitors
• CPC Class Codes: B60L 58/13 Maintaining the SoC within a determined range
• CPC Class Codes: B60L 58/20 having different nominal voltages
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• 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
• CPC Class Codes: Y02T 90/16 Information or communication technologies improving the operation of electric vehicles

Abstract

A vehicular energy management system (EMS) determines a net total power from a traction drive load, an auxiliary device load, and a regenerative power. If the net total power is a net supply power, the EMS causes regenerative power to be provided to a power source and energy source in a controlled manner to initially charge the power source to a desired state-of-charge (SOC) and then subsequently charge the energy source. If the net total power comprises a net power load, the EMS causes power to be drawn from the power source and the energy source, with a split of the power being drawn from the power source and the energy source being based on a magnitude of the net power load. The EMS adjusts/maintains the SOC set-point of the power source and the DC link voltage based on vehicle speed and relative altitude of travel of the vehicle.

Claims

1. A system comprising:

a vehicle;

a power system onboard the vehicle and configured to provide power to drive the vehicle, the power system comprising;

a traction drive including an inverter and an AC motor;

a direct current (DC) link electrically coupled to the traction drive;

a first energy storage device (ESD) electrically coupled to the traction drive to provide power thereto, the first ESD comprising a high specific-power energy storage device; and

a second energy storage device (ESD) electrically coupled to the traction drive to provide power thereto, the second ESD comprising a high specific-energy energy storage device; and

an energy management system (EMS) configured to;

determine a net total power of the vehicle, the net total power comprising a sum of a traction drive load demand, an auxiliary device load demand, and a regenerative power provided by regenerative braking of the traction drive;

cause regenerative power to be provided to each of the first ESD and the second ESD if the net total power comprises a net supply power, with providing of the net supply power being controlled so as to initially charge the first ESD to a desired state-of-charge (SOC) and subsequently charge the second ESD;

cause power to be drawn from the first ESD and the second ESD if the net total power comprises a net power load, with a split of the power being drawn from the first ESD and the second ESD being based on a magnitude of the net power load;

maintain a desired voltage on the DC link based on a speed of the AC motor; and

maintain a desired SOC of the first ESD based on a speed and a relative altitude or slope of travel of the vehicle.

2. The system of claim 1 wherein the EMS, in being programmed to cause regenerative power to be provided to each of the first ESD and the second ESD, is further programmed to

compare the net power load to a first power load threshold and a second power load threshold;

cause power to be drawn only from the second ESD if the net power load is below the first power load threshold;

cause power to be drawn from each of the first ESD and the second ESD if the net power load is between the first power load threshold and the second power load threshold; and

cause power to be drawn from one of the first ESD and second ESD up to a maximum power or capacity limit thereof if the net power load is above the second power load threshold, with any additional power needed to meet the net power load being drawn from the other of the first ESD and the second ESD.

3. The system of claim 1 wherein the EMS is further programmed to cause a portion of the regenerative power to first be provided to meet the auxiliary load demand, with a remainder of the regenerative power comprising the net supply power that is provided to each of the first ESD and the second ESD individually or split between the first ESD and the second ESD up to their respective power or capacity limits.

4. The system of claim 1 wherein the EMS, in being programmed to maintain a desired voltage on the DC link, is further programmed to:

increase the voltage on the DC link as the speed of the AC motor increases; and

decrease the voltage on the DC link as the speed of the AC motor decreases.

5. The system of claim 1 wherein the EMS, in being programmed to maintain a desired SOC of the first ESD, is further programmed to:

set a SOC set-point for the first ESD; and

adjust the SOC set-point based on the speed and the relative altitude or slope of travel of the vehicle;

wherein the SOC set-point is adjusted downward as the speed increases, the relative altitude increases, or the slope of travel is ascending, and the SOC set-point is adjusted upward as the speed decreases, the relative altitude decreases, or the slope of travel is descending.

6. The system of claim 5 wherein the EMS is further programmed to:

determine a kinetic energy and gravity potential energy based on the speed and relative altitude or the slope of travel of the vehicle, respectively; and

adjust the SOC set-point by an amount proportional to a sum of the kinetic energy and gravity potential energy.

7. The system of claim 1 wherein the EMS is further programmed to adjust the split of the power to be drawn from the first ESD and the second ESD based on efficiency and life cycle costs of the first ESD and the second ESD, where the efficiency of the first ESD is the product of charging efficiency and the discharging efficiency, with the product of the charging efficiency and the discharging efficiency being a round-trip efficiency, and efficiency of the second ESD being the discharging efficiency, respectively.

8. The system of claim 1 wherein a net supply power is present when the regenerative power is greater than a sum of the fraction drive load demand and the auxiliary load demand;

and

wherein a net power load is present when the sum of the traction drive load demand and the auxiliary load demand is greater than the regenerative power.

9. The system of claim 1 wherein the EMS is further programmed to have a variable max recharging power limit to regulate SOC of the first ESD when the system has a net power load, so that the sum of this variable max recharging power limit, the auxiliary load demand, and the traction drive load demand is no more than the max power output limit of the second ESD.

10. The system of claim 1 wherein the first ESD comprises one of a high performance lithium-ion battery, a bank of ultracapacitors, or a combination thereof;

and

wherein the second ESD comprises one of a lithium-ion, sodium-metal halide, sodium nickel chloride, sodium-sulfur, nickel-metal hydride or zinc-air battery.

11. The system of claim 1 further comprising one or more bi-directional boost converters configured to manage a power provided to and drawn from at least one of the first ESD and the second ESD, with operation of the bi-directional boost converters being controlled by the EMS.

12. A system for optimizing energy storage component usage in a vehicle comprising one of a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle, the system comprising an energy management system (EMS) programmed to:

determine a net total power of the vehicle, the net total power comprising a combination of an inverter load demand for driving a traction drive, an auxiliary load demand, and a regenerative power provided by regenerative braking of the traction drive;

determine if the net total power comprises a net supply power or a net power load;

if the net total power comprises a net supply power, then cause the net supply power to be provided to each of a power source and an energy source in the vehicle that provide traction power, wherein the net supply power is first supplied to the power source so as to bring the power source to a state-of-charge (SOC) set-point and is then subsequently supplied to the energy source;

if the net total power comprises a net power load, then;

compare the net power load to at least one power load threshold; and

control a drawing of power from the power source and the energy source to meet the inverter and auxiliary load demands, with an amount of power being drawn from each of the power source and the energy source being based on the comparison of the net power load to the at least one power load threshold;

maintain a desired voltage on a DC link in the vehicle based on a speed of a motor in the traction drive; and

maintain the power source at the SOC set-point, which is adjusted based on a speed of the vehicle and an altitude and grade of terrain the vehicle is traveling on.

13. The system of claim 12 wherein the EMS, in being programmed to control the drawing of power from the power source and the energy source, is further programmed to:

compare the net power load to a first power load threshold and a second power load threshold;

cause power to be drawn only from the energy source if the net power load is below the first power load threshold;

cause power to be drawn from each of the power source and the energy source if the net power load is between the first power load threshold and the second power load threshold; and

cause power to be drawn from one of the power source and the energy source up to a maximum power or capacity limit thereof if the net power load is above the second power load threshold, with any additional power needed to meet the net power load being drawn from the other of the power source and the energy source.

14. The system of claim 12 wherein the EMS, in being programmed to control the drawing of power from the power source and the energy source, is further programmed to maximize the efficiency of power source and the energy source, wherein the efficiency of the power source is the product of charging efficiency and discharging efficiency, with the product of the charging efficiency and the discharging efficiency being a round-trip efficiency, and efficiency of the energy source is the discharging efficiency, respectively.

15. The system of claim 12 wherein the EMS is further programmed to first cause regenerative power to be provided to the auxiliary load before causing regenerative power to be provided to the power source and the energy source.

16. The system of claim 12 wherein the EMS, in being programmed to maintain the desired voltage on the DC link, is further programmed to increase the voltage on the DC link as the speed of the motor increases and decrease the voltage on the DC link as the speed of the motor decreases.

17. The system of claim 12 wherein the EMS, in being programmed to determine and maintain the SOC set-point of the power source, is further programmed to adjust the SOC set-point downward as the speed and altitude of the terrain increase and adjust the SOC set-point upward as the speed and altitude of the terrain decrease.

18. The system of claim 12 wherein the EMS is further programmed to have a variable max recharging power limit to regulate SOC of the power source when the system has a net power load, so that the sum of this variable max recharging power limit, the auxiliary load demand, and the traction drive load demand is no more than the max power output limit of the energy source.

19. A method for optimizing energy storage component usage in a vehicle having a high specific-power energy storage device and a high specific-energy energy storage device coupled to a traction drive by way of a direct current (DC) link, the method comprising:

determining a desired operating voltage for the DC link in the vehicle based on a speed of a motor in the fraction drive;

determining a state-of-charge (SOC) set-point for the high specific power energy storage device (ESD) based on a speed of the vehicle and an altitude of the road being traveled by the vehicle;

determining a power state of the vehicle based on a summation of a traction drive load demand, an auxiliary device load demand, and a regenerative power supply provided by regenerative braking of the traction drive, the power state comprising one a net power supply or a net power load;

selectively providing a charging power to the high specific-power ESD and the high specific-energy ESD if the vehicle has a net power supply, wherein charging power is provided so as to initially charge the high specific-power ESD to the determined SOC set-point before charging the high specific-energy ESD; and

selectively drawing power from the high specific-power ESD and the high specific-energy ESD if the vehicle has a net power load, wherein power is drawn from one of, or split between, the high specific-power ESD and the high specific-energy ESD based on a magnitude of the net power load.

20. The method of claim 19 further comprising:

comparing the net power load to a first power load threshold and a second power load threshold;

causing power to be drawn only from the high specific-energy ESD if the net power load is below the first power load threshold;

causing power to be drawn from each of the high specific-power ESD and the high specific-energy ESD if the net power load is between the first power load threshold and the second power load threshold; and

causing a maximum power to be drawn from one of the high specific-power ESD and the high specific-energy ESD if the net power load is above the second power load threshold, with any additional power needed to meet the net power load being drawn from the other of the high specific-power ESD and the high specific-energy ESD.

21. The method of claim 19 further comprising causing regenerative power to be provided to meet the auxiliary load demand before causing regenerative power to be provided to the high specific-energy ESD and the high specific-power ESD.

22. The method of claim 19 further comprising:

increasing the voltage on the DC link as the speed of the motor increases;

decreasing the voltage on the DC link as the speed of the motor decreases;

increasing the SOC set-point as the speed of the vehicle decreases and the road altitude and road grade decreases; and

decreasing the SOC set-point as the speed of the vehicle increases and the road altitude and road grade increases.

23. The method of claim 19 further comprising have a variable max recharging power limit to regulate SOC of the high specific-power ESD when the vehicle has a net power load, so that the sum of the variable max recharging power limit, the auxiliary device load demand and the traction drive load demand is no more than the max power output limit of the high specific-energy ESD.