Power processing unit and related method for regulating a voltage despite voltage fluctuations across an energy storage device

1. A power processing unit configured to be coupled to an energy storage device, the energy storage device configured to deliver electrical energy to a load, and configured to receive electrical energy from a source, the power processing unit comprising:

a. a switching module including:

i. an inductor, and

ii. a plurality of switches coupled to the inductor;

b. a control module including a pulse generator that is coupled to the plurality of switches;

c. a first terminal; and

d. a second terminal;

e. wherein the power processing unit is configured to regulate a voltage that corresponds to the voltage measured across the first and second terminals, the voltage being regulated to be at approximately a prescribed value despite a fluctuation in voltage across the energy storage device while electrical energy is received by the energy storage device, or while electrical energy is delivered from the energy storage device to the load.

2. The power processing unit according to claim 1 , wherein the energy storage device is a capacitor.

3. The power processing unit according to claim 2 , wherein the capacitor is an ultracapacitor.

4. The power processing unit according to claim 2 , further comprising a dissipative element coupled in parallel with the capacitor.

5. The power processing unit according to claim 2 , wherein:

a. the capacitor includes a first lead and a second lead;

c. the inductor includes a first lead and a second lead; and

d. the plurality of switches includes:

i. a first switch that is coupled between the inductor's first lead and the capacitor's first lead,

ii. a second switch that is coupled between the inductor's first lead and the capacitor's second lead,

iii. a third switch that is coupled between the inductor's second lead and the power processing unit's first terminal, and

iv. a fourth switch that is coupled between the inductor's second lead and the power processing unit's second terminal.

6. The power processing unit according to claim 5 , wherein:

a. the control module further includes:

i. a first adder having a first input, a second input, and an output;

ii. a voltage regulator having an input that is coupled to the first adder's output, and an output;

iii. a second adder having a first input that is coupled to the voltage regulator's output, a second input, and an output; and

iv. a current regulator having an input that is coupled to the second adder's output, and an output; and

b. the pulse generator has an input that is coupled to the current regulator's output, and a first output, second output, third output, and fourth output.

7. The power processing unit according to claim 6 , wherein:

a. a reference voltage is coupled into the first adder's first input;

b. the voltage that corresponds to the voltage measured across the power processing unit's first and second terminals is coupled into the first adder's second input; and

c. a voltage that corresponds to an amount of current flowing through the inductor is coupled into the second adder's second input.

8. The power processing unit according to claim 6 , wherein:

a. the pulse generator's first output is coupled to the first switch;

b. the pulse generator's second output is coupled to the second switch;

c. the pulse generator's third output is coupled to the third switch; and

d. the pulse generator's fourth output is coupled to the fourth switch.

9. The power processing unit according to claim 8 , wherein:

a. the pulse generator generates a switch control signal that is coupled into one switch of the first, second, third, and fourth switches; and

b. the switch control signal enables the flow of a current through the one switch.

10. A method for regulating a voltage, the method comprising:

a. providing an energy storage device;

b. providing a power processing unit coupled to the energy storage device, the power processing unit including

i. a switching module that is coupled to the energy storage device and includes a plurality of switches,

ii. a control module that is coupled to the switching module,

iii. a first terminal, and

iv. a second terminal;

c. using the control module to generate a switch control signal;

d. coupling the switch control signal into one of the plurality of switches; and

e. using the switch control signal to control the one of the plurality of switches so that a voltage that corresponds to the voltage measured across the first and second terminals is regulated to be at approximately a prescribed value despite a fluctuation in voltage across the energy storage device as electrical energy is received by the energy storage device, or as electrical energy is delivered from the energy storage device to a load.

11. The method according to claim 10 , wherein the energy storage device is a capacitor.

12. The method according to claim 11 , wherein the capacitor is an ultracapacitor.

13. The method according to claim 11 , further comprising providing a dissipative element coupled in parallel with the capacitor.

14. The method according to claim 11 , wherein:

a. the capacitor includes a first lead and a second lead;

b. the switching module includes an inductor having a first lead and a second lead; and

c. the plurality of switches includes:

i. a first switch that is coupled between the inductor's first lead and the capacitor's first lead,

ii. a second switch that is coupled between the inductor's first lead and the capacitor's second lead,

iii. a third switch that is coupled between the inductor's second lead and the power processing unit's first terminal, and

iv. a fourth switch that is coupled between the inductor's second lead and the power processing unit's second terminal.

15. The method according to claim 14 , wherein the control module includes:

a. a first adder having a first input, a second input, and an output;

b. a voltage regulator having an input that is coupled to the first adder's output, and an output;

c. a second adder having a first input that is coupled to the voltage regulator's output, a second input, and an output;

d. a current regulator having an input that is coupled to the second adder's output, and an output; and

e. a pulse generator having an input that is coupled to the current regulator's output, and a first output, second output, third output, and fourth output.

16. The method according to claim 15 , wherein:

a. a reference voltage is coupled into the first adder's first input;

b. the voltage that corresponds to the voltage measured across the power processing unit's first and second terminals is coupled into the first adder's second input; and

c. a voltage that corresponds to an amount of current flowing through the inductor is coupled into the second adder's second input.

17. The method according to claim 15 , wherein:

a. the pulse generator's first output is coupled to the first switch;

b. the pulse generator's second output is coupled to the second switch;

c. the pulse generator's third output is coupled to the third switch; and

d. the pulse generator's fourth output is coupled to the fourth switch.

18. A power processing unit configured to control a fluctuation in voltage across a capacitor having a first lead and a second lead as electrical energy is received by the capacitor, or as electrical energy is delivered from the capacitor to a load, the power processing unit comprising:

a. a switching module including:

i. an inductor having a first lead and a second lead, and

ii. a plurality of switches coupled to the inductor;

b. a control module including a pulse generator that is coupled to the plurality of switches;

c. a first terminal; and

d. a second terminal;

e. wherein the plurality of switches includes:

i. a first switch that is coupled between the inductor's first lead and the capacitor's first lead,

ii. a second switch that is coupled between the inductor's first lead and the capacitor's second lead,

iii. a third switch that is coupled between the inductor's second lead and the power processing unit's first terminal, and

iv. a fourth switch that is coupled between the inductor's second lead and the power processing unit's second terminal.

19. The power processing unit according to claim 18 , wherein:

a. the control module further includes:

i. a first adder having a first input, a second input, and an output;

ii. a voltage regulator having an input that is coupled to the first adder's output, and an output;

iii. a second adder having a first input that is coupled to the voltage regulator's output, a second input, and an output; and

iv. a current regulator having an input that is coupled to the second adder's output, and an output; and

b. the pulse generator has an input that is coupled to the current regulator's output, and a first output, second output, third output, and fourth output.

20. The power processing unit according to claim 19 , wherein:

a. a reference voltage is coupled into the first adder's first input;

b. a voltage that corresponds to a voltage measured across the power processing unit's first and second terminals is coupled into the first adder's second input; and

c. a voltage that corresponds to an amount of current flowing through the inductor is coupled into the second adder's second input.

21. The power processing unit according to claim 19 , wherein:

a. the pulse generator's first output is coupled to the first switch;

b. the pulse generator's second output is coupled to the second switch;

c. the pulse generator's third output is coupled to the third switch; and

d. the pulse generator's fourth output is coupled to the fourth switch.

22. The power processing unit according to claim 21 , wherein:

a. the pulse generator generates a switch control signal that is coupled into one switch of the first, second, third, and fourth switches; and

b. the switch control signal enables the flow of a current through the one switch.