Life degradation mitigation for transient response energy storage

Patent metadata

Field	Value
Publication number	US-9729008-B2
Application number	US-201414263233-A
Country	US
Kind code	B2
Filing date	Apr 28, 2014
Priority date	May 14, 2013
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

A variable speed genset system is provided that may include a primary power source, an electric machine, an energy storage device, a boost converter, and a controller. The electric machine may be coupled to the primary power source and electrically coupled to a load through a common bus. The boost converter may be in electrical communication with the common bus and the energy storage device. The controller may determine a State of Health (SOH) for the energy storage device, selectively engage the energy storage device to provide a first power amount to the common bus, and selectively change the operating speed of the primary power source to provide a second power amount to the common bus, the speed based on the SOH, a temperature of the energy storage device, and the load demand. The combination of the first and second power amounts substantially meet a load power demand.

First claim

What is claimed is:

1. A variable speed genset system, comprising:
a primary power source;
a common bus having a DC bus voltage;
an electric machine mechanically coupled to the primary power source, the electric machine electrically coupled to a load through the common bus;
an energy storage device;
a boost converter in electrical communication with each of the common bus and the energy storage device, the boost converter configured to boost a DC voltage supplied by the energy storage device into a DC voltage which approximates the DC bus voltage of the common bus; and
a controller in operable communication with the primary power source, the energy storage device, and the common bus, the controller configured to:
determine a State of Health (SOH) for the energy storage device;
selectively engage the energy storage device to provide a first power amount to the common bus; and
selectively change an operating speed of the primary power source from a first speed to a second speed to provide a second power amount to the common bus, the second speed based on the SOH, a temperature of the energy storage device, and a load power demand, wherein a combination of the first power amount and the second power amount substantially meets the load power demand.

2. The variable speed genset system of claim 1 , wherein the controller is further configured to:
determine a State of Charge (SOC) of the energy storage device; and
use the SOC to determine the SOH.

3. The variable speed genset system of claim 2 , wherein the SOC is a summation of fatigue-adjusted capacity changes for a plurality of preceding time periods of discharge of the energy storage device.

4. The variable speed genset system of claim 1 , wherein the SOH is based at least in part on a State of Charge (SOC) of the energy storage device, a lowest voltage of the energy storage device during a discharge period, a peak current supplied by the energy storage device during the discharge period, and a derate scaling factor.

5. The variable speed genset system of claim 1 , wherein the second speed of the primary power source is determined from a set of power-speed curves, corresponding to the temperature of the energy storage device, that define different adjusted operating speeds of the primary power source in relation to different load power demands and the SOH of the energy storage device.

6. A method for optimizing an operating speed of a variable speed genset system, the method comprising:
determining a State of Health (SOH) and a temperature for an energy storage device;
selectively engaging the energy storage device to provide a first power amount to a common bus of the variable speed genset system; and
selectively changing, by a controller, the operating speed of a primary power source of the variable speed genset system from a first speed to a second speed to provide a second power amount to the common bus,
wherein the second speed is based on the SOH, the temperature of the energy storage device, and a load power demand, and
wherein a combination of the first power amount and the second power amount substantially meets the load power demand.

7. The method according to claim 6 , further comprising:
determining a State of Charge (SOC) of the energy storage device; and
using the SOC to determine the SOH.

8. The method according to claim 7 , wherein the SOC is a summation of fatigue-adjusted capacity changes for a plurality of preceding time periods of discharge of the energy storage device.

9. The method according to claim 7 , further comprising using a charging system to increase the SOC of the energy storage device.

10. The method according to claim 6 , wherein the SOH is based at least in part on a State of Charge (SOC) of the energy storage device, a lowest voltage of the energy storage device during a discharge period, a peak current supplied by the energy storage device during the discharge period, and a derate scaling factor.

11. The method according to claim 6 , wherein the SOH is a percentage (SOH %) defined by an equation
SOH %=1−{[( V (n−1) t (n−1) )/(Δ T (n−1 ) I (n−1) SOC (n−1) )]−[ V n t n /(Δ T n I n SOC n )]} K,

wherein
n is a last discharge of the energy storage device,
n−1 is a discharge prior to the last discharge of the energy storage device,
ΔT n is an elapsed time during n,
ΔT (n−1) is an elapsed time during n−1,
V (n−1) is a lowest voltage of the energy storage device during ΔT (n−1) ,
t (n−1) is the temperature of the energy storage device during ΔT (n−1) ,
I (n−1) is a peak current supplied by the energy storage device during ΔT (n−1) ,
SOC (n−1) is a State of Charge of the energy storage device at a start of n−1,
V n is the lowest voltage of the energy storage device during ΔT (n) ,
t n is the temperature of the energy storage device during ΔT (n) ,
I n is the peak current supplied by the energy storage device during ΔT (n) ,
SOC n is the State of Charge of the energy storage device at a start of n, and K is a derate scaling factor for the energy storage device.

12. The method according to claim 6 , further comprising:
adjusting the operating speed of the variable speed genset system to a target speed that substantially meets the load power demand, if the temperature of the energy storage device is less than a temperature limit.

13. The method according to claim 6 , wherein the second speed of the primary power source is determined from a set of power-speed curves, corresponding to the temperature of the energy storage device, that define different adjusted operating speeds of the primary power source in relation to different load power demands and the SOH of the energy storage device.

14. The method according to claim 6 , further comprising displaying a flag to indicate a health condition of the energy storage device.

15. A transient assist system for a variable speed genset system having a primary power source, a variable speed generator, and a common bus, the transient assist system comprising:
an energy storage device;
a boost converter in electrical communication with each of the common bus and the energy storage device, the boost converter configured to boost a DC voltage supplied by the energy storage device into a DC voltage which approximates the DC bus voltage of the common bus; and
a controller in operable communication with the primary power source, the energy storage device, and the common bus, the controller configured to:
determine a State of Health (SOH) for the energy storage device;
selectively engage the energy storage device to provide a first power amount to the common bus; and
selectively change an operating speed of the primary power source from a first speed to a second speed to provide a second power amount to the common bus, the second speed based on the SOH, a temperature of the energy storage device, and a load power demand, wherein a combination of the first power amount and the second power amount substantially meets the load power demand.

16. The transient assist system of claim 15 , wherein the controller is further configured to:
determine a State of Charge (SOC) of the energy storage device based on a summation of fatigue-adjusted capacity changes for a plurality of preceding time periods of discharge of the energy storage device.

17. The transient assist system of claim 15 , wherein the SOH is a percentage (SOH %) defined by an equation
SOH %=1−{[( V (n−1) t (n−1) )/(Δ T (n−1) I (n−1) SOC (n−1) )]−[ V n t n /(Δ T n I n SOC n )]} K,

where

Assignees

• Caterpillar Inc

Inventors

• Votoupal John J
• Yu Dachuan
• Hasler Gregory S
• Speckhart Gregory J

Classifications

• H02J7/875

  Charging or discharging for charge maintenance, battery initiation or rejuvenation · CPC title

• H02J9/066 Primary

  characterised by the use of dynamo-electric machines (H02J9/08 takes precedence) · CPC title

• H02J7/0075

  Electricity · mapped topic

• Y10T307/352

  Cross-Sectional Technologies · mapped topic