A method of detecting oscillations is disclosed. An input signal is received. A time delay is added to the input signal. A coherence between the input signal and the time-delayed input signal is estimated. The coherence is greater than a predetermined threshold. The time delay may be greater than or equal to one sampling interval.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 The invention was made with Government support under Contract DE-ACO5-76RLO1830, awarded by the U.S. Department of Energy. The Government has certain rights in the invention.