METHOD FOR SMOOTHING ALTERNATING ELECTRIC CURRENT FROM A NUMBER OF POWER GENERATING UNITS AND WIND POWER PLANT INCLUDING A NUMBER OF WIND MILLS WITH VARIABLE ROTATIONAL SPEED

• US 20090267419A1
• Filed: 12/11/2006
• Published: 10/29/2009
• Est. Priority Date: 02/03/2006
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Stiesdal, Henrik
• Granted Patent: US 7,990,113 B2
• Time in Patent Office: Days
• US Class Current: 307/80
• CPC Class Codes: H02J 2300/20 The dispersed energy generation being of renewable origin
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy
• CPC Class Codes: H02J 2300/40 wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/0043 Converters switched with a phase shift, i.e. interleaved non-isolated DC/DC converters H02M3/1586
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects

Abstract

A method and a wind power plant are provided for smoothing alternating electric current from a number of power generators. Generators are electrically connected to an electric network. Each power generator includes a transformer with pulse width modulation for converting direct current to pulse width modulated alternating current for feeding to the network. The time for feeding the pulses of the pulse width modulated alternating current is different for each generator in order to achieve a more even alternating current as a sum of respective outputs of alternating current from the generators.

Claims

1-11. -11. (canceled)

12. A method for smoothing alternating electric current from a plurality of power generating units, where the power generating units are electrically connected to an electric network, comprising:

converting direct current to pulse width modulated alternating current for feeding to the network, the conversion by a transformer with pulse width modulation and which is included in each power generating unit,

wherein times for feeding pulses of the pulse width modulated alternating current are different for respective power generating units in order to achieve a more even alternating current as a sum of respective outputs of alternating current from the power generating units.

13. The method according to claim 12, wherein at least one of the power generating units is a windmill with variable rotational speed.

14. The method according to claim 12, wherein power generating units are part of a wind power plant.

15. The method according to claim 12, wherein power generating units are part of a water wave power plant.

16. The method according to claim 12, wherein the pulse width depends on the time of feeding.

17. The method according to claim 16, wherein the time of feeding is determined from a GPS time signal.

18. The method according to claim 16, wherein the times of feeding for the respective power generating units are determined by respective feeding frequency, wherein the feeding frequencies are different for each power generating unit.

19. The method according to claim 16, wherein the times of feeding for the respective generating units are determined by respective feeding frequency, wherein the feeding frequency for each generating unit is varying.

20. The method according to claim 12, wherein the time of feeding is determined from a GPS time signal.

21. The method according to claim 12, wherein the times of feeding for the respective power generating units are determined by respective feeding frequency, wherein the feeding frequencies are different for each power generating unit.

22. The method according to claim 12, wherein the times of feeding for the respective generating units are determined by respective feeding frequency, wherein the feeding frequency for each generating unit is varying.

23. The method according to claim 12, wherein the times of feeding for the respective power generating unit involves a signal from a random generator.

24. A wind power plant, comprising:

a plurality of windmills having variable rotational speed, the windmills connected to an electric network, and each windmill includes;

a generator for producing an electric current,

a converter for pulse width modulated conversion of direct current to pulse width modulated alternating current for feeding to the network, and

a time controller determines a time for feeding the pulses of the pulse width modulated alternating current,

wherein the time controllers are programmed for feeding the pulses from the each windmill at different times in order to achieve a more even alternating current.

25. The wind power plant according to claim 24, wherein at least one time controller includes a GPS receiver for receiving the time signal from a GPS transmitter in order calibrate the feeding time.

26. The wind power plant according to claim 24, wherein the times controller are programmed for feeding the pulses at feeding frequencies that are mutually different for the generating units.