System for stabilizing synchronous machines
First Claim
1. System for stabilizing a synchronous machine through excitation control to dampen out the machine oscillations by direct modulation of the voltage fed back to an automatic voltage regulator, comprisingcurrent and potential transformer means for obtaining a measure of terminal current and voltage of said synchronous machine;
- analog to digital conversion means for sampling the values of A.C. voltages and currents on said potential and current transformer means to obtain instantaneous values of sampled voltage and current, and for converting said sampled values into digitized form;
accelerating power signal processing means responsive to said instantaneous values of voltage and current for deriving values of inferred measure of the accelerating power of said synchronous machine, said accelerating power signal processing means including slip frequency deriving means, responsive to said instantaneous values of voltage, to develop values of slip frequency of said voltage in relation to the rated frequency of said machine;
a stabilizer signal generator means responsive to said values of inferred measure of accelerating power for producing digital stabilizer signals corresponding to said values of accelerating power; and
autotransformer means connected between said stabilizer signal generator means and said automatic voltage regulator, including solid state tap switching means responsive to said digital stabilizer signals for selecting the taps on said autotransformer and thereby controlling and modulating its output to said automatic voltage regulator in synchronism with the rate of sampling of said voltages and currents;
whereby damping of machine oscillations is provided by calculation of the accelerating power through the voltage and current values, and calculation of the rotor slip from the present and past computed values of internal voltage to effect the solid state switching of autotransformer taps to said automatic voltage regulator.
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Accused Products
Abstract
A microprocessor based, power systems stabilizer operating through excitation control wherein all required stabilizing information is derived from sampled values of voltage and current taken from potential and current transformers. The instantaneous values of terminal voltage and current are processed using algorithms in the accelerating power signal digital processor portion of the microprocessor to thereby develop a value of instantaneous internal voltage, the value of slip frequency of such voltages in relation to rated frequency and a digitally filtered value of electrical power. The accelerating power is calculated from the rate of change of slip and electrical power. The values of accelerating power are processed with digital algorithms in a stabilizing signal compute section of the microprocessor to yield a stabilizing signal which provides the desired modulating action for damping the machine oscillations of the synchronous generator. This modulating action is provided by switching the taps in an autotransformer being supplied from the potential transformer secondary measuring generator terminal voltage and feeding the voltage regulator and exciter for the generator. The selection of taps on the autotransformer is controlled by the microprocessor based stabilizer system at an appropriate rate, such as every one to ten milliseconds.
51 Citations
17 Claims
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1. System for stabilizing a synchronous machine through excitation control to dampen out the machine oscillations by direct modulation of the voltage fed back to an automatic voltage regulator, comprising
current and potential transformer means for obtaining a measure of terminal current and voltage of said synchronous machine; -
analog to digital conversion means for sampling the values of A.C. voltages and currents on said potential and current transformer means to obtain instantaneous values of sampled voltage and current, and for converting said sampled values into digitized form; accelerating power signal processing means responsive to said instantaneous values of voltage and current for deriving values of inferred measure of the accelerating power of said synchronous machine, said accelerating power signal processing means including slip frequency deriving means, responsive to said instantaneous values of voltage, to develop values of slip frequency of said voltage in relation to the rated frequency of said machine; a stabilizer signal generator means responsive to said values of inferred measure of accelerating power for producing digital stabilizer signals corresponding to said values of accelerating power; and autotransformer means connected between said stabilizer signal generator means and said automatic voltage regulator, including solid state tap switching means responsive to said digital stabilizer signals for selecting the taps on said autotransformer and thereby controlling and modulating its output to said automatic voltage regulator in synchronism with the rate of sampling of said voltages and currents; whereby damping of machine oscillations is provided by calculation of the accelerating power through the voltage and current values, and calculation of the rotor slip from the present and past computed values of internal voltage to effect the solid state switching of autotransformer taps to said automatic voltage regulator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. Method for stabilizing a synchronous machine through excitation control to dampen out the machine oscillations by direct modulation of the voltage fed back to an automatic voltage regulator, comprising:
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providing current and potential transformer means at the output of said machine for obtaining a measure of terminal current and voltage of said synchronous machine; sampling the output voltages and current on said potential and voltage transformer means to obtain instantaneous, digital values of sampled voltage and current, and converting said sampled values into digitized form; processing said instantaneous values of voltage and current for deriving values representing an inferred measure of the accelerating power of said synchronous machine including the steps of developing values of slip frequency of said voltage in relation to the rated frequency of said machine, combining said intantaneous values of voltage and current for computing the instantaneous power output of said machine, and combining values of said slip frequency and said instantaneous power for calculating values of the accelerating power of said machine;
converting said values of inferred measure of accelerating power into a form used as a digital stabilizer signal; andapplying said digital stabilizer signal to an autotransformer tap switching means for selecting the taps on said autotransformer and thereby controlling and modulating its output to said automatic voltage regulator in synchronism with the rate of sampling of said voltages and currents; whereby damping of machine oscillations is provided by calculation of accelerating power to compensate for phase lags in the excitation control. - View Dependent Claims (14, 15, 16, 17)
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Specification