System and method for precharging and discharging a high power ultracapacitor pack
View Patent ↗This invention is a system and a method that uses the braking resistor, commonly used and available in electrically or hybrid-electrically propelled vehicles, to limit the precharge current during the startup of a high power ultracapacitor pack energy storage device and/or safely and rapidly discharge an ultracapacitor pack for maintenance work or storage to lengthen the life of the individual ultracapacitor cells and, correspondingly, the whole pack. The use of the braking resistor for precharging an ultracapacitor energy storage pack is an effective and less expensive method compared to other methods such as a separate DC-to-DC converter. This method includes the control logic sequence to activate and deactivate switching devices that perform the connections for the charging and discharging current paths.
1. A method for rapidly discharging an ultracapacitor energy storage cell pack in a drive system, wherein the drive system includes a braking resistor and a power bus, and wherein the ultracapacitor energy storage cell pack and the braking resistor may be selectably connected to the power bus, the method comprising:
determining the ultracapacitor energy storage cell pack requires discharging;
connecting the braking resistor to the power bus;
discharging the ultracapacitor energy storage cell pack through the braking resistor; and
cooling the braking resistor.
2. The method of claim 1 , wherein the discharging the ultracapacitor energy storage cell pack through the braking resistor comprises connecting the ultracapacitor energy storage cell pack to the power bus.
3. The method of claim 1 , wherein the cooling the braking resistor comprises circulating a cooling liquid.
4. The method of claim 1 , wherein the drive system further includes an engine and a generator, the engine capable of driving the generator, and wherein the generator may be selectably disconnected from the power bus, the method further comprising:
determining the engine is running; and,
disconnecting the generator from the power bus.
5. The method of claim 1 , wherein the drive system further includes an engine and a generator, the engine capable of driving the generator and the generator capable of driving the engine, wherein the generator may be selectably connected to the power bus, the method further comprising:
determining the engine is not running;
shutting off fuel to the engine;
connecting the generator to the power bus; and,
driving the engine via the generator with the energy stored in the ultracapacitor energy storage cell pack.
6. The method of claim 5 , further comprising shutting the drive system down when the ultracapacitor energy storage cell pack is sufficiently discharged.
7. The method of claim 1 , wherein the discharging the ultracapacitor energy storage cell pack through the braking resistor may include discharging at least 60 kW of power.
8. The method of claim 1 , wherein the discharging the ultracapacitor energy storage cell pack through the braking resistor is completed in less than one minute.
9. A rapid discharge system for an ultracapacitor energy storage cell pack in a drive system, the system comprising:
a power bus;
a motor selectably connected to the power bus;
a braking resistor selectably connected to the power bus;
a pump configured to circulate cooling fluid through the braking resistor;
a first switch configured to disconnect the ultracapacitor energy storage cell pack from the motor;
a second switch configured to connect the ultracapacitor energy storage cell pack to the braking resistor;
a controller configured to discharge the ultracapacitor energy storage cell pack by disconnecting the ultracapacitor energy storage cell pack from the motor via the first switch, and connecting the ultracapacitor energy storage cell pack to the braking resistor via the second switch.
10. The rapid discharge system of claim 9 , further comprising:
a generator selectably connected to the power bus;
an engine connected to the generator;
a third switch configured to disconnect the ultracapacitor energy storage cell pack from the generator;
wherein the controller is further configured to determine that the engine is running, and to disconnect the ultracapacitor energy storage cell pack from the generator via the third switch.
11. The rapid discharge system of claim 9 , further comprising:
a fuel shut off device configured to shut off fuel to the engine;
wherein the controller is further configured to determine that the engine is not running, to connect the ultracapacitor energy storage cell pack to the generator, and thus to drive the engine via the generator with the energy stored on the ultracapacitor energy storage cell pack.
12. The rapid discharge system of claim 11 , further comprising shutting the drive system down when the ultracapacitor energy storage cell pack is sufficiently discharged.
13. The rapid discharge system of claim 9 , wherein the controller is further configured to discharge the ultracapacitor energy storage cell pack in less than one minute.
14. The rapid discharge system of claim 9 , wherein the drive system is configured to propel a heavy-duty vehicle.
15. A method for rapidly discharging an ultracapacitor energy storage cell pack in a drive system, wherein the drive system includes an engine, a generator, and a power bus, and wherein the ultracapacitor energy storage cell pack and the generator may be selectably connected to the power bus, the method comprising:
determining the ultracapacitor energy storage cell pack requires discharging;
determining the engine is not running;
shutting off fuel to the engine;
connecting the generator to the power bus; and
discharging the ultracapacitor energy storage cell pack by driving the engine via the generator with the energy stored in the ultracapacitor energy storage cell pack.
16. The method of claim 15 , further comprising shutting the drive system down when the ultracapacitor energy storage cell pack is sufficiently discharged.
17. The method of claim 16 , wherein the shutting the drive system down when the ultracapacitor energy storage cell pack is sufficiently discharged comprises shutting the drive system down when the ultracapacitor energy storage cell pack is discharged down to a minimum operating voltage of the generator.
18. The method of claim 15 , wherein the discharging the ultracapacitor energy storage cell pack by driving the engine may include discharging at least 30 kW of power.
19. The method of claim 15 , wherein the drive system further includes a braking resistor, the method further comprising
connecting the braking resistor to the power bus;
wherein the discharging the ultracapacitor energy storage cell pack further comprises discharging the ultracapacitor energy storage cell pack through the braking resistor.
20. The method of claim 19 , wherein the discharging the ultracapacitor energy storage cell pack through the braking resistor may include discharging at least 60 kW of power.
21. The method of claim 19 , wherein the discharging the ultracapacitor energy storage cell pack is completed in less than one minute.
22. A rapid discharge system for an ultracapacitor energy storage cell pack in a drive system, the rapid discharge system comprising:
a power bus;
a generator selectably connected to the power bus;
an engine connected to the generator;
a motor selectably connected to the power bus;
a first switch configured to disconnect the ultracapacitor energy storage cell pack from the motor;
a second switch configured to connect the ultracapacitor energy storage cell pack to the generator;
a fuel shut-off; and,
a controller configured to determine that the engine is not running, to shut off fuel to the engine via the fuel shut-off, and to discharge the ultracapacitor energy storage cell pack by disconnecting the ultracapacitor energy storage cell pack from the motor via the first switch, and connecting the ultracapacitor energy storage cell pack to the generator via the second switch.
23. The rapid discharge system of claim 22 , wherein the controller is further configured to shut the drive system down when the ultracapacitor energy storage cell pack is discharged down to a minimum operating voltage of the generator.
24. The rapid discharge system of claim 22 , further comprising:
a braking resistor selectably connected to the power bus;
a pump configured to circulate cooling fluid through the braking resistor; and,
a third switch configured to connect the ultracapacitor energy storage cell pack to the braking resistor;
wherein the controller is further configured to connect the braking resistor to the power bus via the third switch, to circulate cooling fluid through the braking resistor via the pump, and to further discharge the ultracapacitor energy storage cell pack by also connecting the ultracapacitor energy storage cell pack to the braking resistor.
25. The rapid discharge system of claim 24 , wherein the controller is further configured to discharge the ultracapacitor energy storage cell pack in less than one minute.
26. The rapid discharge system of claim 22 , wherein the drive system is configured to propel a heavy-duty vehicle.