Electromechanical energy conversion systems
An exemplary power system may include an electric machine with multiple sets of stator windings, each set of windings being coupled through a separate switch matrix to a common voltage bus, and each of which may be spatially arranged in full pitch around the stator such that stator flux harmonics are substantially reduced. The reduced stator flux harmonics may be associated with phase current harmonic content. In an example application, such power systems may operate in a generating mode to transfer mechanical energy to electrical energy on a DC voltage bus. In some illustrative embodiments, the power system may provide both high-power and high-speed (e.g., 1 MW at 8000 rpm or above) motoring and/or generating capability suitable, for example, for on-board (e.g., marine, aviation, traction) power systems.
1. A system comprising:
an electric machine that comprises:
a stator with a plurality of winding locations distributed substantially evenly across a surface of the stator; and
a plurality of conductors defining a plurality of coils arranged substantially symmetrically among the plurality of winding locations and connected to form a number (N) of sets of multiple (M) phase windings, wherein for each of the windings, each of the coils spans a single pole to form a full pitch winding, and wherein each of the N sets of windings are offset with respect to each other so as to substantially reduce a harmonic content of a magnetic flux within a first frequency range during operation; and
a plurality of switch matrices configured to provide electrical power to the N sets of windings during operation.
2. The system of claim 1 , further comprising a voltage bus configured to provide electrical power to the plurality of switch matrices.
3. The system of claim 1 , the switch matrices configured to operate at a switching frequency substantially equal to a fundamental electrical frequency of the electric machine during operation.
4. The system of claim 1 , the plurality of switch matrices comprising N active switch matrices, each of the N active switch matrices coupled to one of the N sets of windings.
5. The system of claim 1 , wherein N is equal to 4 and M is equal to 3.
6. The system of claim 1 , wherein N is equal to 2 and M is equal to 3.
7. The system of claim 1 , wherein N is equal to 3.
8. The system of claim 1 , wherein the windings carry a current having a π/(M*N) electrical phase difference between adjacent winding locations during operation.
9. The system of claim 1 , wherein the switch matrices include one or more switch matrices connected in series.
10. The system of claim 1 , wherein each of the N sets of windings is electrically isolated from the other sets.
11. The system of claim 1 , wherein the N sets of windings carry current during operation, and the current carried by each of the N sets of windings is phase-shifted with respect to the current carried by the other sets of windings.
12. A method for providing for providing mechanical energy conversion, comprising:
providing an electric machine that comprises:
a stator with a plurality of winding locations distributed substantially evenly across a surface of the stator; and
a plurality of conductors defining a plurality of coils arranged substantially symmetrically among the plurality of winding locations and connected to form a number (N) of sets of multiple (M) phase windings, wherein for each of the windings, each of the coils spans a single pole to form a full pitch winding, and wherein each of the N sets of windings are offset with respect to each other so as to substantially reduce a harmonic content of a magnetic flux within a first frequency range during operation; and
operating the electric machine.
13. The method of claim 12 , wherein operating the electric machine comprises providing electrical power from a plurality of switch matrices to the N sets of windings.
14. The method of claim 13 , wherein N is equal to 4 and M is equal to 3.
15. The method of claim 13 , wherein N is equal to 2 and M is equal to 3.
16. The method of claim 12 , wherein N is equal to 3.
17. The method of claim 13 , wherein operating the electric machine further comprises providing electrical power from a voltage bus to the plurality of switch matrices.
18. The method of claim 13 , wherein providing electrical power from the plurality of switch matrices to the N sets of windings comprises operating the switch matrices at a switching frequency substantially equal to a fundamental electrical frequency of the electric machine.
19. The method of claim 12 , wherein operating the electric machine comprises energizing the windings with current having a π/(M*N) electrical phase difference between adjacent winding locations.
20. A system comprising:
an electric machine that comprises:
a stator with a plurality of winding locations distributed substantially evenly across a surface of the stator; and
a plurality of conductors defining a plurality of coils arranged substantially symmetrically among the plurality of winding locations and connected to form a number (N) of sets of multiple (M) phase windings, wherein for each of the windings, each of the coils spans a single pole to form a full pitch winding, and wherein each of the N sets of windings are offset with respect to each other so as to reduce a harmonic content of a magnetic flux within a first frequency range during operation; and
a processing stage that comprises N substantially independent modules coupled to the N sets of windings.
21. The system of claim 20 , wherein each of the N modules comprises an active switching matrix.
22. The system of claim 20 , wherein N is equal to 4.
23. The system of claim 20 , wherein N is equal to 3.
24. The system of claim 20 , wherein N is equal to 2.
25. The system of claim 20 , wherein each of the N modules is configured to operate at a switching frequency substantially equal to a fundamental electrical frequency of the electric machine.
26. The system of claim 20 , wherein multiple output ports of each of the N modules are connected in series between nodes of a voltage bus.
27. A method comprising:
providing an electric machine that comprises:
a stator with a plurality of winding locations distributed substantially evenly across a surface of the stator;
a plurality of conductors defining a plurality of coils arranged substantially symmetrically among the plurality of winding locations and connected to form windings; and
a plurality of switch matrices configured to provide electrical power to the windings; and
operating the electric machine at a fundamental electrical frequency of the electric machine by switching the switch matrices at a switching frequency substantially equal to the fundamental electrical frequency.
28. The method of claim 27 , wherein:
the plurality of coils are connected to form a number (N) of sets of multiple (M) phase windings, wherein for each of the windings, each of the coils spans a single pole to form a full pitch winding, and wherein each of the N sets of windings are offset with respect to each other so as to substantially reduce a harmonic content of a magnetic flux within a first frequency range during operation; and
the plurality of switch matrices including N active switch matrices configured to provide electrical power to the N sets of windings during operation.
29. The method claim 28 , wherein N is equal to 4.
30. The method claim 28 , wherein N is equal to 3.
31. The method claim 28 , wherein N is equal to 2.