# US 4,393,345 A · Circuit for damping hunting by electric machines

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- Number: US 4,393,345 A
- Document ID: US4393345A
- Status: Granted
- Kind: A
- Application number: 06/199,685
- Filed: 1980-10-22
- Granted: 1983-07-12
- Earliest claimed: 1979-11-12
- Assignees: Siemens Aktiengesellschaft
- Inventors: Kurt Fork; Wolfgang Kaufhold; Wolfgang Meusel; Hermann Waldmann
- Web page: https://patentgrep.com/patent/US4393345A

## CPC

- H02P 9/10: Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
- Y10S 505/851: Control circuit for electromagnetic device
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A circuit for damping hunting oscillations of controlled electric machines. The circuit is provided with a measuring circuit for determining the hunting oscillations and an identifier circuit for determining the angle components of such hunting oscillations. A phase shifter circuit is provided for receiving the angle components produced by the identifier circuit and forming a hunting oscillation correction signal which is shifted in phase from the hunting oscillations by a predetermined phase angle. The hunting oscillation correction signal is conducted to a control unit of the electric machine. The invention is particularly useful in damping hunting by the rotors of voltage controlled synchronous generators.

## Claims

### Claim 1

A circuit for damping hunting oscillations of a controlled electric synchronous machine of the type having a rotor and a stator, the circuit being of the type which determines the hunting oscillation and combines a phase-shifted oscillation correction signal with a control signal of the circuit, the circuit further comprising:
identification circuit means for producing a first signal having a frequency which corresponds to a frequency of the hunting oscillation and a second signal having saId frequency and shifted in phase by 90.degree. with respect to said first signal;
phase shift means for forming the phase-shifted oscillation correction signal, said phase-shifted oscillation correction signal being shifted in phase with respect to said first and second signals by a selectable amount, said first and second signals being combined with one another in accordance with their respective amplitudes.

### Claim 2 (depends on 11)

The circuit of claim 11 wherein said identification circuit means comprises a power measuring circuit for measuring electrical power related to the controlled electric machine.

### Claim 3 (depends on 1)

The circuit of claim 1 wherein said measuring means comprises a rotor position transmitter.

### Claim 4 (depends on 1)

The circuit of claim 1 wherein said identification circuit means comprises a vector identifier for identifying angle components of the hunting oscillations.

### Claim 5 (depends on 4)

The circuit of claim 4 wherein said vector identifier further comprises means for eliminating a steady-state signal component in said first signal.

### Claim 6 (depends on 1)

The circuit of claim 1 wherein said identification circuit means comprises a vector filter for identifying angle components of the hunting oscillations.

### Claim 7 (depends on 1)

The circuit of claim 1 wherein said phase shift means forms said phase-shifted oscillation correction signal which is shifted in phase with respect to the hunting oscillations by a phase angle which is responsive to a selectable one of a load condition of the controlled electric synchronous machine and an analysis of the hunting oscillations.

### Claim 8 (depends on 1)

The circuit of claim 1 wherein there are further provided controller means for controlling electrical conduction through the stator of the controlled electric synchronous machine; and
comparator means having a first input terminal for receiving said phase-shifted oscillation correction signal, and an output terminal for conducting a fourth signal to said controller means.

### Claim 9 (depends on 8)

The circuit of claim 8 wherein said comparator means is provided with a second input terminal for receiving a signal corresponding to a voltage at a network to which the controlled electric synchronous machine is connected.

### Claim 10 (depends on 1, 2, 3, 4, 5, 6, 7, 8, 9)

The circuit of claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 wherein the controlled electric synchronous machine is a voltage controlled synchronous generator, said hunting oscillation correction signal being responsive to hunting oscillations of the rotor of said voltage controlled synchronous generator.