Hybrid conditioner for a power system

1. A hybrid conditioner for filtering harmonics in a power system having a non-linear load and an AC source generating AC power at a fundamental frequency f, comprising:

an active filter structured and controlled to filter one or more high-order harmonic currents of said fundamental frequency f; and

a passive filter structured to filter one or more low-order harmonic currents of said fundamental frequency f;

wherein said active filter and said passive filter are electrically connected in parallel with one another and with said non-linear load, said hybrid conditioner also being for providing oscillation dampening for said power system, wherein said active filter is further controlled to provide an oscillation compensating current that is 180 degrees out of phase with respect to an oscillating current between said passive filter and said AC source to damp said oscillating current.

2. The hybrid conditioner according to claim 1 , further comprising one or more additional active filters, each of said additional active filters being connected in parallel with said active filter and being adapted to filter one or more additional high-order harmonic currents of said fundamental frequency f.

3. The hybrid conditioner according to claim 1 , further comprising one or more additional passive filters, each of said additional passive filters being connected in parallel with said passive filter and being adapted to filter one or more additional low-order harmonic currents of said fundamental frequency f.

4. The hybrid conditioner according to claim 1 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 5th order harmonic of said fundamental frequency f.

5. The hybrid conditioner according to claim 1 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 7th order harmonic of said fundamental frequency f.

6. The hybrid conditioner according to claim 1 , said hybrid conditioner also being for providing reactive power compensation for said power system, wherein said active filter is further controlled to provide a second reactive power for compensating for a first reactive power consumed by said load.

7. The hybrid conditioner according to claim 6 , further comprising a controller operatively coupled to and controlling said active filter, said controller being programmed to receive voltage and current information relating to said power system and determine said first reactive power and said second reactive power using said voltage and current information.

8. The hybrid conditioner according to claim 1 , wherein said non-linear load is a variable frequency drive.

9. A power system structured to receive AC power from an AC source at a fundamental frequency f, comprising:

a non-linear load; and

a hybrid conditioner including:

an active filter structured and controlled to filter one or more high-order harmonic currents of said fundamental frequency f; and

a passive filter structured to filter one or more low-order harmonic currents of said fundamental frequency f;

wherein said active filter, said passive filter and said non-linear load are electrically connected in parallel with one another and said non-linear load, and wherein said active filter is further controlled provide an oscillation compensating current that is 180 degrees out of phase with respect to an oscillating current between said passive filter and said AC source to damp said oscillating current.

10. The power system according to claim 9 , further comprising one or more additional active filters, each of said additional active filters being connected in parallel with said active filter and being adapted to filter one or more additional high-order harmonic currents of said fundamental frequency f.

11. The power system according to claim 9 , further comprising one or more additional passive filters, each of said additional passive filters being connected in parallel with said passive filter and being adapted to filter one or more additional low-order harmonic currents of said fundamental frequency f.

12. The power system according to claim 9 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 5th order harmonic of said fundamental frequency f.

13. The power system according to claim 9 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 7th order harmonic of said fundamental frequency f.

14. The power system according to claim 9 , wherein said active filter is further controlled to provide a second reactive power for compensating for a first reactive power consumed by said load.

15. The power system according to claim 14 , further comprising a controller operatively coupled to and controlling said active filter, said controller being programmed to receive voltage and current information relating to said power system and determine said first reactive power and said second reactive power using said voltage and current information.

16. The power system according to claim 9 , wherein said non-linear load is a variable frequency drive.

17. A variable frequency drive structured to receive AC power from an AC source at a fundamental frequency f and provide output power to an AC motor, comprising:

a rectifier; and

a hybrid conditioner including:

an active filter structured and controlled to filter one or more high-order harmonic currents of said fundamental frequency f; and

a passive filter structured to filter one or more low-order harmonic currents of said fundamental frequency f;

wherein said active filter, said passive filter and said rectifier are electrically connected in parallel, and wherein said active filter is further controlled to provide an oscillation compensating current that is 180 degrees out of phase with respect to an oscillating current between said passive filter and said AC source to damp said oscillating current.

18. The variable frequency drive according to claim 17 , further comprising one or more additional active filters, each of said additional active filters being connected in parallel with said active filter and being adapted to filter one or more additional high-order harmonic currents of said fundamental frequency f.

19. The variable frequency drive according to claim 17 , further comprising one or more additional passive filters, each of said additional passive filters being connected in parallel with said passive filter and being adapted to filter one or more additional low-order harmonic currents of said fundamental frequency f.

20. The variable frequency drive according to claim 17 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 5th order harmonic of said fundamental frequency f.

21. The variable frequency drive according to claim 17 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 7th order harmonic of said fundamental frequency f.

22. The variable frequency drive according to claim 17 , wherein said active filter is further controlled to provide a second reactive power for compensating for a first reactive power consumed by said rectifier.

23. The variable frequency drive according to claim 22 , further comprising a controller operatively coupled to and controlling said active filter, said controller being programmed to receive voltage and current information relating to said variable frequency drive and determine said first reactive power and said second reactive using said voltage and current information.

24. A method of filtering harmonics in a power system having a non-linear load and an AC source generating AC power at a fundamental frequency f, comprising:

receiving said AC power;

filtering one or more high-order harmonic currents of said fundamental frequency f in said power system using one or more active filters; and

filtering one or more low-order harmonic currents of said fundamental frequency f in said power system using one or more passive filters;

wherein said one or more active filters and said one or more passive filters are provided in a hybrid conditioner, wherein said one or more active filters and said one or more passive filters are electrically connected in parallel with one another and said non-linear load; and

controlling at least one of said one or more active filters to provide an oscillation compensating current that is 180 degrees out of phase with respect to an oscillating current between said one or more passive filters and said AC source to damp said oscillating current.

25. The method according to claim 24 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 5th order harmonic of said fundamental frequency f.

26. The method according to claim 24 , wherein said fundamental frequency f is 60 Hz, and wherein a predetermined threshold harmonic for determining what is a high-order harmonic and what is a low-order harmonic is a 7th order harmonic of said fundamental frequency f.

27. The method according to claim 24 , the method also being for providing reactive power compensation for said power system, the method further comprising determining a first reactive power consumed by said load, determining a second reactive power for compensating for said first reactive power and controlling at least one of said one or more active filters to provide said second reactive power.

28. The method according to claim 24 , wherein said non-linear load is a variable frequency drive.