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 system for precharging an ultracapacitor energy storage cell pack, comprising:
an ultracapacitor pack, a high power DC bus, an electro-magnetic braking regeneration system, and a breaking resistor to dissipate power from the electro-magnetic braking regeneration system;
means for switching the braking resistor in series with the ultracapacitor pack;
means for switching the braking resistor in series with the ultracapacitor, with the high power DC bus;
means for determining when to disconnect the braking resistor in series with the ultracapacitor pack and connect the ultracapacitor pack directly with the high power DC bus;
means for disconnecting the braking resistor in series with the ultracapacitor pack and connecting the ultracapacitor pack directly with the high power DC bus.
2. The system of claim 1 , wherein the high power DC bus is powered from a power source including at least one of an engine/generator set, a fuel cell, a turbine generator set, a power grid, a propulsion motor in braking regeneration mode, and a battery pack.
3. The system of claim 1 , wherein the system is a system of at least one of an electric vehicle and a hybrid-electric vehicle.
4. The system of claim 1 , wherein the determining means includes means for identifying an ultracapacitor pack in a state of discharge.
5. The system of claim 1 , wherein the determining means includes means for monitoring the ultacapacitor pack voltage.
6. The system of claim 1 , wherein the determining means includes means for monitoring the power bus voltage.
7. The system of claim 1 , wherein the determining means includes means for determining when an ultracapacitor pack voltage and a power bus voltage are matched.
8. The system of clam 1 , further including a timing system to determine when an ultracapacitor pack precharge is complete.
9. The system of claim 1 , wherein the switching means include at least one of high power contactor relays and Insulated Gate Bipolar Transistors (IGBTs).
10. The system of claim 1 , wherein the switching means are liquid cooled.
11. The system of claim 1 , further including means for increasing the voltage across the braking resistor, to control the charge current, after the braking resistor is connected in series with the ultracapacitor pack to shorten the precharge time.
12. The system of claim 2 , wherein the power source, the braking resistor, and the ultracapacitor pack are liquid cooled.
13. The system of claim 2 , wherein the power source is a generator, and the generator is a permanent magnet generator.
14. The system of claim 2 , further including a power source input circuit with a power conditioning inverter, the power conditioning inverter being a DC to DC converter.
15. The system of claim 14 , wherein the inverter is a Pulse Width Modulated (PWM) inverter.
16. The system of claim 14 , wherein the inverter includes IGBT switching.
17. The system of claim 1 , further including the traction motor control circuit with a power controlling inverter.
18. The system of claim 17 , wherein the inverter is a PWM inverter.
19. The system of claim 17 , wherein the inverter includes IGBT switching.
20. The system of claim 17 , further including traction motors, and the traction motors are at least one of AC induction motors and permanent magnet motors.
21. The system of claim 1 , wherein the ultracapacitor pack is a plurality of ultracapacitor packs connected in at least one of a series combination and a parallel combination.
22. The system of claim 1 , wherein the braking resistor is a plurality of resistors connected in at least one of a series combination and a parallel combination.
23. The system of claim 1 , wherein the braking resistor is a heating element for liquids.
24. The system of claim 1 , wherein the ultracapacitor pack is any type of energy storage pack that requires a precharge function including a flywheel.
25. The system of claim 1 , further including means for determining the current charge rate of the ultracapacitor pack.
26. The system of claim 25 , wherein the determining means includes means for monitoring the voltage across the braking resistor.
27. A method of precharging an ultracapacitor energy storage cell pack, comprising:
providing a drive system including an ultracapacitor pack, a high power DC bus, an electro-magnetic braking regeneration system, and a breaking resistor to dissipate power from the electromagnetic braking regeneration system;
switching the braking resistor in series with the ultracapacitor pack;
switching the braking resistor in series with the ultracapacitor, with the high power DC bus;
determining when to disconnect the braking resistor in series with the ultracapacitor pack and connect the ultracapacitor pack directly with the high power DC bus;
disconnecting the braking resistor in series with the ultracapacitor pack and connecting the ultracapacitor pack directly with the high power DC bus.
28. The method of claim 27 , further including determining the ultracapacitor pack is in a state of discharge.
29. The method of claim 27 , further including monitoring the ultracapacitor pack voltage.
30. The method of claim 27 , further including monitoring the power bus voltage.
31. The method of claim 27 , further including determining when the ultracapacitor pack voltage is matched to the power bus voltage.
32. The method of claim 27 , further including using a timer to determine when an ultracapacitor precharge is complete.
33. The method of claim 27 , wherein the drive system includes at least one of software and firmware with control logic therein.
34. The method of claim 33 , wherein the control logic is implanted by means of a Programmable Logic Controller (PLC).
35. The method of claim 27 , further including reporting control commands and status reporting over a Control Area Network (CAN) data bus, the CAN data bus being a SAE Standard J1939.
36. The method of claim 35 , wherein the control commands are part of the control strategy of a hybrid-electric vehicle drive system.
37. The method of claim 27 , wherein the drive is a hybrid electric vehicle drive system.