Adaptive power electronics interface for hybrid energy systems

1. An adaptive hybrid energy system, the system comprising:

a first DC electrical energy source that generates a first DC electrical output by converting energy from a first energy source into an electrical output;

at least a second DC energy source that generates a second DC electrical output by converting energy from a second energy source into an electrical output; and

a cascaded multilevel converter electrically connected to the first and second DC energy sources to convert a DC electrical output into a time-varying electrical output when at least one of the first and second DC energy sources is operable,

wherein the converter comprises a first H-bridge connected to the first DC energy source and a second H-bridge and comprising a capacitor connected to the second DC energy source in a cascade arrangement with the first H-bridge, wherein a plurality of switching elements in the first and second H-bridges are configured to operate using a fundamental frequency switching method when the second DC energy source is inoperable so that the capacitor remains balanced over a complete energy cycle, and wherein a capacitor-load time constant of the converter is at least ten times the time of the complete energy cycle.

2. The system of claim 1 , wherein the time-varying electrical output is an electrical output having a sinusoidal waveform.

3. The system of claim 1 , wherein the energy from the second energy source is a type different than a type of the energy from the first energy source.

4. The system of claim 3 , wherein the second energy source is a stochastic source of energy.

5. The system of claim 4 , wherein the second energy source comprises a source of wind power.

6. The system of claim 1 , wherein the first DC energy source comprises at least one wind turbine, and wherein the second DC energy source comprises one of a battery, a fuel cell, or a solar-based energy source.

7. The system of claim 1 , wherein the first DC energy source charges the capacitor during a charging cycle when the second DC energy source is inoperable.

8. The system of claim 1 , wherein the at least a second DC energy source comprises a third DC energy source, and wherein the cascaded multilevel converter further comprises a third H-bridge electrically connected to the third DC energy source such that the adaptive hybrid energy system is configured to generate a three-phase electrical output.

9. The system of claim 8 , further comprising a bi-level bridge connected in a cascade arrangement to the first, second, and third H-bridges.

10. The system of claim 9 , wherein the bi-level bridge comprises a six-switch bridge converter.

11. The system of claim 1 , wherein the capacitor discharges during a discharging cycle when the second DC energy source is inoperable.

12. The system of claim 1 , wherein the capacitor has a voltage equal to one-half times a voltage of the first DC energy source.

13. An electronic interface for controlling a hybrid energy system, the interface comprising:

a first H-bridge converter that connects to a first DC energy source; and

in a cascade arrangement with the first H-bridge converter, a second H-bridge converter that connects to a second DC energy source;

wherein the second H-bridge converter comprises a capacitor, and wherein a plurality of switching elements in the first and second H-bridges are configured to operate using a fundamental frequency switch method so that the capacitor remains balanced over a complete electrical output cycle when the second DC energy source is inoperable, and wherein a capacitor-load time constant of the converter is at least ten times the time of the complete energy cycle.

14. The electronic interface of claim 13 , wherein the first energy source provides a voltage V dc to the first H-bridge converter and the capacitor is configured to hold a voltage 1/2V dc , and wherein the plurality of switching elements are configured to cause said first H-bridge converter to selectively output a first voltage equal to one of 0V, V dc , and −V dc and to cause said second H-bridge converter to selectively output a second voltage equal to one of 0V, 1/2V dc , and −1/2V d , when the second DC energy source is inoperable, and wherein said cascade of said first and second H-bridges is configured to combine the first and second voltages to output said sinusoid waveform with voltage steps equal to one of −3/2V dc , −V dc , −1/2V dc , 0V, 1/2V dc , V dc , and 3/2V dc .

15. The electronic interface of claim 14 , wherein said cascade of said first and second H-bridges is configured to combine the first and second voltages to output a sinusoid waveform with voltage steps equal to one of −3/2V dc , −V dc , −1/2V dc , 0V, 1/2V dc , V dc , and 3/2V dc .

16. The electronic interface of claim 13 , wherein the first energy source provides a voltage V dc to the first H-bridge converter and the capacitor is configured to hold a voltage 1/2V dc , and wherein the plurality of switching elements are configured to cause said first H-bridge converter to selectively output a first voltage equal to one of 0V, V dc , and −V dc and to cause said second H-bridge converter to selectively output a second voltage equal to one of 0V, 1/2V dc , and −1/2V dc , when the second DC energy source is inoperable.

17. The electronic interface of claim 13 , further comprising a third H-bridge connected to a third DC energy source that cooperatively operates with the first and second DC energy sources to supply energy for a three-phase output of the hybrid energy system.

18. The electronic interface of claim 17 , further comprising a bi-level bridge in cascade arrangement with the first, second, and third H-bridge converters.

19. The electronic interface of claim 13 , wherein the first DC energy source charges the capacitor during a charging cycle when the second DC energy source is inoperable.

20. The electronic interface of claim 13 , wherein the capacitor discharges during a discharging cycle when the second DC energy source is inoperable.

21. The electronic interface of claim 13 , wherein the capacitor has a voltage equal to one-half times a voltage of the first DC energy source.