Hybrid energy storage system and methods
A system includes a first DC rail configured to be coupled to a first terminal of a first energy storage device (e.g., a battery), a second DC rail configured to be coupled to a first terminal of a second energy storage device (e.g., an ultracapacitor), and a plurality of converter legs coupled between the first and second DC rails and including at least one first converter leg configured to be coupled to a second terminal of the first energy storage device and at least one second converter leg configured to be coupled to second terminal of the second energy storage device. The system further includes a switch configured to couple and decouple the second terminals of the first and second energy storage devices. The at least one first converter leg and the at least one second converter leg provide different current capacities to deal with differences in power density of the energy storage devices.
1. A system comprising:
a converter comprising three legs coupled between first and second DC rails;
a first energy storage device having a first terminal coupled to the first DC rail and a second terminal coupled to a first one of the converter legs;
a second energy storage device having a first terminal coupled to the second DC rail and a second terminal coupled to second and third ones of the converter legs; and
a switch configured to couple and decouple the second terminals of the first and second energy storage devices.
2. The system of claim 1 , wherein the first energy storage device comprises at least one battery and wherein the second energy storage device comprises at least one capacitor.
3. The system of claim 1 , wherein each of the three legs comprises first and second switches coupled in a half-bridge configuration.
4. The system of claim 1 , wherein the switches operate responsive to a voltage of the first and second DC rails.
5. The system of claim 1 , further comprising a diode coupled between the first and second energy storage devices and in parallel with the switch.
6. A system comprising:
a plurality of converter legs coupled between first and second DC rails;
at least one battery having a first terminal coupled to the first DC rail and a second terminal coupled to at least one first converter leg of the plurality of converter legs;
at least one capacitor having a first terminal coupled to the second DC rail and a second terminal coupled to at least one second converter leg of the plurality of converter legs; and
a switch configured to couple and decouple the second terminals of the at least one capacitor and the at least one battery.
7. The system of claim 6 , wherein the at least one second converter leg provides a greater current capacity than the at least one first converter leg.
8. The system of claim 6 , wherein the at least one second converter leg comprises at least two converter legs and wherein the at least one first converter leg is a single converter leg.
9. The system of claim 6 , wherein each of the three legs comprises first and second switches coupled in a half-bridge configuration.
10. The system of claim 6 , wherein the switches operate responsive to a voltage of the first and second DC rails.
11. The system of claim 6 , further comprising a diode coupled in parallel with the switch.
12. A system comprising:
a first DC rail configured to be coupled to a first terminal of a first energy storage device;
a second DC rail configured to be coupled to a first terminal of a second energy storage device;
a plurality of converter legs coupled between the first and second DC rails and including at least one first converter leg configured to be coupled to a second terminal of the first energy storage device and at least one second converter leg configured to be coupled to second terminal of the second energy storage device; and
a switch configured to couple and decouple the second terminals of the first and second energy storage devices.
13. The system of claim 12 , wherein the at least one first converter leg and the at least one second converter leg provide different current capacities.
14. The system of claim 12 , wherein the at least one first converter leg comprises a different number of converter legs than the at least one second converter leg.
15. The system of claim 14 , wherein the at least one second converter leg comprises at least two converter legs and wherein the at least one first converter leg is a single converter leg.
16. The system of claim 12 , further comprising the first and second energy storage devices.
17. The system of claim 16 , wherein the first energy storage device comprises at least one battery and wherein the second energy storage device comprises at least one capacitor.
18. The system of claim 12 , wherein the switches operate responsive to a voltage of the first and second DC rails.
19. The system of claim 12 , further comprising a diode coupled in parallel with the switch.