DC-DC converter in a non-steady system
Multiphase electromagnetic machines, such as free-piston engines or compressors, may require, or supply, a pulsed power profile from or to a DC bus, respectively. The pulsed power profile may include relatively large fluctuations in instantaneous power. Sourcing, sinking, or otherwise exchanging power with an AC grid, via an inverter, may be accomplished by using an energy storage device and a DC-DC converter coupled to a DC bus. The energy storage device may aid in smoothing the pulsed power profile, while the DC-DC converter may aid in reducing fluctuations in voltage across a DC bus due to energy storage in the energy storage device.
1. A power management system that receives a power output from a free-piston power generator comprising:
a first DC bus controlled by an inverter;
a first DC-DC converter coupled to the first DC bus and configured to provide a second DC bus, wherein the first DC-DC converter is configured to output a smoothed power output to the inverter relative to the power output;
at least one energy storage device coupled to the second DC bus;
a second DC-DC converter coupled to the second DC bus and to the free-piston power generator, wherein the second DC-DC converter is configured to receive the power output from the free-piston power generator.
2. The power management system of claim 1 , wherein the second DC-DC converter is coupled to the free-piston power generator by a third DC bus, further comprising circuitry coupled to the third DC bus and configured to:
control a plurality of currents in a plurality of respective phases of the free-piston power generator to generate the power output.
3. The power management system of claim 1 , wherein the second DC bus comprises:
a first bus at a first voltage; and
a second bus at a second voltage lower than the first voltage.
4. The power management system of claim 1 , wherein the inverter is coupled to at least one of a power grid and a load.
5. The power management system of claim 1 , wherein the at least one energy storage device comprises at least one capacitor.
6. The power management system of claim 1 , wherein the at least one energy storage device is configured to store and release electrical energy from the second DC bus.
7. The power management system of claim 1 , wherein the smoothed power output has a corresponding voltage, and wherein the first DC-DC converter is configured to regulate the voltage.
8. The power management system of claim 1 , wherein the first DC-DC converter is adjustable, the power management system further comprising a control system configured to adjust one or more operating characteristics of the first DC-DC converter.
9. The power management system of claim 1 , wherein the first DC-DC converter comprises a step-down converter.
10. A power management system that receives power from a power input and provides a pulsed power output to a free-piston machine comprising:
a first DC bus controlled by an inverter coupled to the power input;
a first DC-DC converter coupled to the first DC bus and configured to provide a second DC bus;
at least one energy storage device coupled to the second DC bus;
a second DC-DC converter coupled to the second DC bus, wherein the second DC-DC converter is configured to output the pulsed power output to the free-piston machine relative to the power input.
11. The power management system of claim 10 , wherein the second DC-DC converter is coupled to the free-piston machine by a third DC bus, further comprising circuitry coupled to the third DC bus and configured to:
control a plurality of currents in a plurality of respective phases of an electric motor of the free-piston machine to provide the pulsed power output.
12. The power management system of claim 10 , wherein the second DC bus comprises:
a first bus at a first voltage; and
a second bus at a second voltage lower than the first voltage.
13. The power management system of claim 10 , wherein the inverter is coupled to a power grid.
14. The power management system of claim 10 , wherein the at least one energy storage device comprises at least one capacitor.
15. The power management system of claim 10 , wherein the at least one energy storage device is configured to store and release electrical energy from the second DC bus.
16. The power management system of claim 10 , wherein the pulsed power output has a corresponding voltage, and wherein the second DC-DC converter is configured to regulate the voltage.
17. The power management system of claim 10 , wherein the second DC-DC converter is adjustable, the power management system further comprising a control system configured to adjust one or more operating characteristics of the second DC-DC converter.
18. The power management system of claim 10 , wherein the second DC-DC converter comprises a step-down converter.