1. A method to balance power in a synchronous generator system, the method comprising:
determining a first output power characteristic of a first synchronous generator driven by a prime mover;
comparing the first output power characteristic to a value derived from output power of a plurality of synchronous generators to determine a deviation of the first output power characteristic from the value, wherein the plurality of synchronous generators are driven by the prime mover; and
providing a correction signal to the first synchronous generator to adjust the output power thereof, wherein the correction signal is based on the first deviation.
2. The method of claim 1, wherein determining the first output power characteristic comprises measuring real output power of the first synchronous generator.
3. The method of claim 2, wherein a power factor of the first synchronous generator is substantially equal to or greater than 0.85.
4. The method of claim 1, wherein determining the first output power characteristic comprises measuring apparent output power of the first synchronous generator.
5. The method of claim 4, wherein a power factor of the first synchronous generator is substantially equal to or less than 0.85.
6. The method of claim 1, wherein determining the first output power characteristic comprises measuring reactive output power of the first synchronous generator.
7. The method of claim 4, wherein a power factor of the first synchronous generator is substantially equal to or less than 0.50.
8. The method of claim 1, wherein the plurality of synchronous generators includes the first synchronous generator.
9. The method of claim 1, further comprising:
determining an output power of each synchronous generator of the plurality of synchronous generators driven by the prime mover;
comparing each output power of the respective synchronous generators to the average output power of the plurality of synchronous generators to determine a difference between each output power and the average output power; and
providing a correction signal to each synchronous generator, wherein the respective correction signal for each synchronous generator depends upon the respective difference between the output power of the synchronous generator and the average output power of the plurality of synchronous generators.
10. The method of claim 1, wherein the plurality of synchronous generators consists of six synchronous generators.
11. The method of claim 1, wherein providing the correction signal to the first synchronous generator comprises providing the correction signal to a field controller of the first synchronous generator and an error compensation or integration process is performed following the provision of the correction signal.
12. The method of claim 1, wherein the correction signal includes a power balancing correction component and a bus voltage correction component.
13. The method of claim 1, wherein the value is an average output power of the plurality of synchronous generators.
14. A synchronous generator system comprising:
a prime mover;
a mechanical power divider coupled to the prime mover and configured to receive mechanical power therefrom;
a plurality of synchronous generators coupled to the mechanical power divider to receive mechanical power therefrom;
a control unit coupled to the plurality of synchronous generators, the control unit configured to compare output power of each synchronous generator of the plurality of synchronous generators to an average output power of the plurality of synchronous generators, and to provide an adjustment signal to each synchronous generator, wherein the provision of the respective adjustment signal effects modification of a deviation between the output power of each synchronous generator and the average output power of the plurality of synchronous generators.
15. The system of claim 14, wherein the control unit is configured to compare real power of the synchronous generator to the average real power of the plurality of synchronous generators.
16. The system of claim 14, wherein the control unit is configured to compare reactive power of the synchronous generator to the average reactive power of the plurality of synchronous generators.
17. The system of claim 14, wherein the control unit is configured to compare apparent power of the synchronous generator to the average apparent power of the plurality of synchronous generators.
18. The system of claim 17, wherein the control unit is configured to compare real power of the synchronous generator to the average real power of the plurality of synchronous generators.
19. The system of claim 18, wherein the control unit is configured to compare either real power or apparent power depending upon a power factor threshold.
20. The system of claim 19, wherein the control unit is configured to compare real power if a power factor of the system exceeds the power factor threshold and to compare apparent power if the power factor is below the power factor threshold.
21. The system of claim 20, wherein the power factor threshold is substantially equal to 0.85.
22. The system of claim 20, wherein the power factor threshold is substantially equal to 0.80.
23. The system of claim 14, wherein the adjustment signal effects modification of the deviation by increasing or decreasing the back EMF of an exciter of the synchronous generator.
24. The system of claim 14, wherein the control unit is configured to provide an adjustment signal to a field controller of each synchronous generator.
25. A method to balance power in a synchronous generator system, the method comprising:
determining a first output power of a first synchronous generator driven by a prime mover;
determining a second output power of a second synchronous generator driven by the prime mover;
comparing the determined first and second output powers to desired first and second output powers, respectively;
applying a first correction signal to the first synchronous generator to effect reduction of a deviation of the determined first output power from the desired first output power; and
applying a second correction signal to the second synchronous generator to effect reduction of a deviation of the determined second output power from the desired second output power.
26. The method of claim 25, wherein the first desired output power is different than the second desired output power.
27. The method of claim 25, further comprising:
determining a respective output power for each synchronous generator of a plurality of synchronous generators, the plurality including the first and second synchronous generators and at least one additional synchronous generator, wherein each of the plurality of synchronous generators is driven by the prime mover and the plurality of synchronous generators produces an aggregate output power;
adjusting a power output of one synchronous generator of the plurality of synchronous generators;
applying a correction signal to another synchronous generator of the plurality of synchronous generators, wherein applying the respective correction signal facilitates power compensation such that the aggregate output power produced by the plurality of synchronous generators remains substantially constant irrespective of the adjustment of the power output of the one synchronous generator.
28. The method of claim 27, wherein adjusting the power output of the one synchronous generator comprises deactivating the one synchronous generator.
29. The method of claim 27, wherein adjusting the power output of the one synchronous generator comprises disconnecting the one synchronous generator from an output bus common to the plurality of synchronous generators to provide power to an independent load.
30. The method of claim 25, wherein the first synchronous generator is a member of a first plurality of synchronous generators and the second synchronous generator is a member of a second plurality of synchronous generators, and wherein the first and second pluralities of synchronous generators provide output power to a first output bus and a second output bus respectively.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of transmitting a pilot in a multi-carrier communication system, comprising: selecting a group of frequency subbands from among M groups of frequency subbands for each of a plurality of time intervals, wherein each group includes a different plurality of frequency subbands selected from among N frequency subbands usable for transmission in the system, where M and N are integers greater than one, wherein the M groups of frequency subbands are of equal size, wherein at least approximately three-fourths of the N usable frequency subbands are included among the M groups of frequency subbands, and wherein the M groups of frequency subbands are selected in the plurality of time intervals; and
for each time interval, multiplexing pilot symbols onto the frequency subbands in the group selected for the, time interval.
2. The method of claim 1, wherein the M groups are non-overlapping and each of the N usable frequency subbands is included among the M groups.
3. The method of claim 2, wherein the plurality of frequency subbands in each group are uniformly distributed across the N frequency subbands.
4. The method of claim 1, wherein different groups of frequency subbands among the M groups of frequency subbands are selected in different time intervals.
5. The method of claim 1, wherein the M groups of frequency subbands are selected in M time intervals based on a staggering pattern that indicates a particular group of subbands to use for each of the M time intervals.
6. The method of claim 5, wherein the M groups of frequency subbands are assigned indices of 1 through M, and wherein the group of frequency subbands selected for each time interval is determined as follows: mt=(mt\u22121\u22121+\u0394 m) mod m+1, where t is an index for time interval; mt\u22121is an index for the group of frequency subbands selected for time interval t\u22121; mt is an index for the group of frequency subbands selected for time interval t; m1 is an index for the group of frequency subbands selected for a first time interval; \u0394 m and M are relatively prime; and \u201cmod M\u201d denotes a modulo-M operation.
7. The method of claim 6, wherein \u0394 m in is an integer value closestto M2.
8. The method of claim 1, wherein each time interval corresponds to one symbol period.
9. The method of claim 1, wherein the multi-carrier communication system utilizes orthogonal frequency division multiplexing (OFDM).
10. An apparatus in a multi-carrier communication system, comprising:
a controller operable to select a group of frequency subbands from among M groups of frequency subbands for each of a plurality of time intervals, wherein each group includes a different plurality of frequency subbands selected from among N frequency subbands usable for transmission in the system, where M and N are integers greater than one, wherein the M groups of frequency subbands are of equal size, wherein at least approximately three-fourths of the N usable frequency subbands are included among the M groups of frequency subbands, and wherein the M groups of frequency subbands are selected in the plurality of time intervals; and
a modulator operable to, for each time interval, multiplex pilot symbols onto the frequency subbands in the group selected for the time interval.
11. The apparatus of claim 10, wherein each of the N usable frequency subbands is included among the M groups, and wherein the plurality of frequency subbands in each group are uniformly distributed across the N frequency subbands.
12. The apparatus of claim 10, wherein the M groups of frequency subbands are assigned indices of 1 through M and are selected in M time intervals, one group of frequency subbands for each of the M time intervals, and wherein the group of frequency subbands selected for each time interval is determined as follows: mt=(mt\u22121\u22121+\u0394m) mod M+1, where t is an index for time interval; mt\u22121 is an index for the group of frequency subbands selected for time interval t\u22121; mt is an index for the group of frequency subbands selected for time interval t; m1 is an index for the group of frequency subbands selected for a first time interval; \u0394 m and M are relatively prime; and \u201cM\u201d denotes a modulo-M operation.
13. A base station comprising the apparatus of claim 10.
14. An apparatus in a multi-carrier communication system, comprising: means for selecting a group of frequency subbands from among M groups of frequency subbands for each of a plurality of time intervals, wherein each group includes a different plurality of frequency subbands selected from among N frequency subbands usable for transmission in the system, where M and N are integers greater than one, wherein the M groups of frequency subbands are of equal size, wherein at least approximately three-fourths of the N usable frequency subbands are included among the M groups of frequency subbands, and wherein the M groups of frequency subbands are selected in the plurality of time intervals; and
means for multiplexing pilot symbols, for each time interval, onto the frequency subbands in the group selected for the time interval.