Dynamic stabilizer for synchronous machines having torsional oscillations and method

• US 3,999,115 A
• Filed: 05/02/1974
• Issued: 12/21/1976
• Est. Priority Date: 05/02/1974
• Status: Expired due to Term

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: South, William H., Kilgore, Lee A.
• Primary Examiner(s): Miller, J D
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/466,318
• Time in Patent Office: 964 Days
• Field of Search: 322/29-32, 322/25, 322/58, 322/17
• US Class Current: 322/25
• CPC Class Codes: H02P 9/105 for increasing the stability

Abstract

A dynamic stabilizer which includes a voltage generator connected in series with the output terminals of a synchronous AC generator provides compensation for voltages produced by the main AC synchronous machine which compensation is provided to overcome the effects of torsional oscillation between masses in the main AC generator system. Torsional oscillations may exist between the masses of turbines driving the AC generator, the exciter mass for the AC generator, and the mass of the rotor of the generator. Shaft angular velocity is sensed and provided to a frequency discriminating filter since the speed is proportional to the torsional oscillation and since a reference signal is provided to the frequency discriminating filter, the frequency discriminating filter provides an output signal which is proportional to the reference signal plus and minus the frequency of the torsional oscillation. This signal is provided to the previously named series connected generator where a 180° phase shift is effectuated between the output signal of the frequency discriminating filter and the output power from the AC synchronous generator. Scaling means is provided to conveniently match the peak amplitudes of the last named signals. The effect of the phase shift of the signal from the frequency discriminating filter as it is applied to the series connected generator is to compensate for the effect of the torsional oscillations in the output power signal of the AC synchronous generator thus providing a power signal for use in a load which is generally without modulating torsional oscillation.

Claims

1. A dynamic stabilizer for compensating for the effect on output electrical power of torsional oscillation in a resilient shaft between masses of an electrical power generating system which is capable of generating electrical power at a nominal frequency, comprising:

a. torsional oscillation sensing means for sensing said torsional oscillation, said torsional oscillation sensing means having an output, said torsional oscillation sensing means providing a torsional oscillation output signal at said latter output which latter signal is related to said torsional oscillation;

b. transfer means for operating on said torsional oscillation output signal, said transfer means having an input and an output, said transfer means input being connected to said torsional oscillation sensing means output to receive said torsional oscillation output signal, said transfer means operating on said torsional oscillation output signal in such a manner as to provide a resulting transfer means output, signal at said transfer means output which is characterized as being related to said nominal frequency of said electrical power and said torsional oscillation; and

c. compensating means for directly compensating for the effect of said torsional oscillation on said generating system output electrical power, said compensating means having a first input which is connected to an electrical power output terminal of said power generating system where said output electrical power is available, said compensating means having a second input which is connected to said output of said transfer means, said compensating means having an output which is connectable with a load, said compensating means receiving said output electrical power from said generating system at said first input which power is affected by said torsional oscillation, said compensating means receiving said transfer means output signal, said later signal being utilized by said compensating means to operate directly on said output electrical power to thereby make available to said load electrical power which is generally unaffected by said torsional oscillation even though said torsional oscillation is present in said shaft.

2. The combination as claimed in claim 1 wherein said output of said sensing means is electrical terminal means, said output and said input of said transfer means are electrical terminal means, and said compensating means second input is electrical terminal means.

3. The combination as claimed in claim 1 wherein said torsional oscillation sensing means comprises shaft velocity sensing means.

4. The combination as claimed in claim 2 wherein said torsional oscillation sensing means comprises velocity sensing means for measuring the velocity of said resilient shaft, said torsional oscillation sensing means output signal comprising an electrical signal which is related to the variation in said velocity of said shaft.

5. The combination as claimed in claim 4 wherein said velocity of said shaft varies at a fixed frequency for a period of time, said electrical output signal of said velocity sensing means varies in proportional to said shaft velocity.

6. The combination as claimed in claim 5 wherein said velocity sensing means comprises tachometer means, said shaft velocity changing generally sinusoidally, said tachometer torsional oscillation output electrical signal being generally of the same sinusoidal frequency as said shaft, said amplitude of said tachometer output signal being proportional to the amplitude of said torsional oscillation.

7. The combination as claimed in claim 1 wherein said transfer means operates on said torsional oscillation sensing means output signal by providing a reference signal which is related to said nominal frequency of said electrical power, said reference signal being multiplied by said torsional oscillation output signal to thus provide said transfer means output signal in the form of said reference signal modulated by said torsional oscillation sensing means output signal.

8. The combination as claimed in claim 6 wherein said transfer means operates on said tachometer means output signal by utilizing a reference electrical signal which is related to said nominal frequency of said electrical power which reference signal is multiplied by said tachometer means output signal to thus provide said transfer means output signal in the form of said reference signal modulated by said tachometer output signal.

9. The combination as claimed in claim 8 wherein said nominal frequency of said electrical power and thus said frequency of said related electrical reference signal is 60 hz.

10. The combination as claimed in claim 8 wherein said nominal frequency of said electrical power and thus said frequency of said related electrical reference signal is 50 hz.

11. The combination as claimed in claim 1 wherein said compensating means operates on said output electrical power by utilizing said transfer means output signal torsional oscillation and cancelling the torsional oscillation in said output electrical power.

12. The combination as claimed in claim 8 wherein said compensating means comprises a power generator means.

13. The combination as claimed in claim 8 wherein said transfer means output signal is different in phase by 180°

from said shaft velocity signal and is added to said output electrical power in said compensating means to thereby cancel the effect of torsional oscillation in said output electrical power.

14. The combination as claimed in claim 1 wherein said torsional oscillation in said shaft generally causes voltage oscillation in said output electrical power output, said electrical power being generally of the alternating type, said compensating means operating on said output electrical power to thereby make of generally peak amplitude available to said load by operating on the voltage component of said power.

15. The combination as claimed in claim 1 wherein said torsional oscillation in said shaft generally causes electrical current oscillation in said output electrical power, said electrical power being generally of the alternating type, said compensating means operating on said output electrical power to thereby make electrical power of generally fixed peak amplitude available to said load by operating on the current component of said power.

16. The combination as claimed in claim 12 wherein the component of voltage of said output electrical power related to said torsional oscillation is cancelled.

17. The combination as claimed in claim 12 wherein the component of current of said output electrical power related to said torsional oscillation is cancelled.

18. An electrical power generating system, comprising:

an alternating current electrical generator which is capable of generating electrical power of generally nominal fixed frequency and generally nominal fixed voltage amplitude at output terminals thereof and supplying said power to a load, said generator having a rotor of predetermined mass;

energy supply means for driving said rotor to thereby generate said power, said energy supply means having a rotatable portion of predetermined mass;

resilient shaft means interconnecting said rotor and said energy supply means rotatable portion, the rotational velocity of said shaft means being capable of changing periodically in relation to torsional oscillation in said resilient shaft means thus causing said nominal fixed amplitude of said electrical voltage to be in fact modulated in relation to said periodic change of said shaft velocity;

tachometer means disposed adjacent said shaft means to measure said rotational velocity of said shaft means and provide an electrical output signal at an output terminal thereof which signal is proportional to said rotational velocity;

frequency discriminating filter means having an input terminal and an output terminal, said input terminal being connected to said output terminal of said tachometer means, said tachometer means output signal being multiplied within said frequency discriminating filter by a reference signal having the same nominal frequency as said electrical power to thereby provide a signal at the output terminal of said frequency discriminating filter which has a resulting wave shape related to said frequency of said reference signal plus said frequency of said tachometer means output signal, said resulting wave shape also being related to said frequency of said reference signal minus said frequency of said tachometer means output signal; and

voltage compensating means interconnected between one terminal of said alternating current electrical generator and said load, said voltage compensating means having an input terminal connected to said output terminal of said frequency discriminating filter means, said output signal of said frequency discriminating filter means being utilized by said voltage compensating means to compensate for said modulation of said electrical power by said torsional oscillation to thereby generally provide electrical power of said nominal fixed frequency and said nominal fixed voltage amplitude to said load.

19. The combination as claimed in claim 18 wherein said voltage compensating means comprises a separate source of power the voltage amplitude and frequency of which are controlled by said output signal from said frequency discriminating filter means, the resulting modulated compensating voltage signal having a carrier frequency which is thus generally the same as the carrier frequency of said modulated output electrical power but the modulation envelope of which is generally 180 degrees out of phase from the modulation envelope of said output electrical power to thus cancel said effect of said torsional oscillation.

20. The combination as claimed in claim 19 wherein said voltage compensating means comprises a cyclo-converter which controls a separate source of compensating power, said cyclo-converter having a control terminal electrically controlled by said frequency discriminating filter means output signal to thereby provide a modulated compensating voltage signal the carrier frequency of which is the same as the carrier of said modulated electrical output power but the modulation envelope of which is 180 degrees out of phase from the modulation envelope of said output electrical power to thus cancel said effect of said torsional oscillation.

21. The combination as claimed in claim 18 wherein said voltage compensating means comprises a power filter connected in circuit relationship with said load and with said terminal of said power generating system, said power filter being tuned to the carrier frequency of said power minus at least one frequency component of said torsional oscillation frequency, a cyclo-converter means, said power filter being magnetically interconnected by transformer means to said cyclo-converter means, said cyclo-converter means controlling a separate source of compensating power, said cyclo-converter means having a control terminal electrically controlled by said frequency discriminating filter means output signal to thereby enhance operation of said power filter by generally cancelling that component of output power characterized by said carrier frequency of said output power minus said frequency component of said torsional oscillation.

22. A method for compensating for the effect of torsional oscillation between rotating masses in an electrical generating system which is capable of providing electrical power to a load, comprising the steps of:

sensing said torsional oscillation and providing a signal related thereto;

multiplying said last signal in a transfer means by a reference frequency signal which is generally related to the output frequency desired of said power generating system and providing an output signal related to said reference signal plus and minus said torsional oscillation signal; and

utilizing said last named output signal in a compensating means connected in circuit relationship with the output terminal of said generator means to compensate for the effect of torsional oscillation in the output power of said generating means by utilizing the last named signal from said transfer means to compensate for the effect of said oscillation in said power signal.

23. A dynamic stabilizer for compensating for an effect of the change in relative motion between the rotor and stator of an electrical power generating system which generates electrical power of a generally given frequency, comprising:

a. sensing means for sensing said change in relative motion, said sensing means having an output, said sensing means providing an output signal at said output which is related to said change in relative motion;

b. transfer means for operating on said output signal from said sensing means, said transfer means having an input and an output, said transfer means input being interconnected to said sensing means output to receive said output signal, said transfer means operating on said output signal from said sensing means to provide a transfer means output signal at said transfer means output which is related both to said frequency of said electrical power from said power generating system and said change in relative motion between said rotor and said stator; and

c. compensating means for compensating for said effect of said change in relative motion, said compensating means having a first input which is connected to an electrical power output terminal of said power generating system, said compensating means having an output which is interconnectable with a load, said compensating means receiving electrical power from said generating system at said first input which power is affected by said change in relative motion, said compensating means receiving said output signal from said transfer means at a second input of said compensating means, said later signal being utilized by said compensating means to operate on said electrical power from said generating system to thereby tend to resist the effect upon said electrical power of said change in relative motion between said rotor and said stator.

24. The combination as claimed in claim 23 wherein said change in relative motion between said rotor and stator is periodic and of a given frequency, said sensing means sensing said later frequency, said transfer means output signal being related to the difference between said later frequency and said frequency of the electrical power from said power generating system.