In the present study, some perturbation methods are applied to Duffing equations having a displacement time-delayed variable to study the stability of such systems. Two approaches are considered to analyze Duffing oscillator having a strong delayed variable. The homotopy perturbation method is applied through the frequency analysis and nonlinear frequency is formulated as a function of all the ...

power system blackouts have become a serious problem for electric utilities especially in recent years. different forms of system instability have emerged in recent blackouts, such as voltage instability and frequency instability. to counteract each form of system instability, special algorithms have been designed in the protection system, e.g. under frequency load shedding (ufls) and under vol...

The hydrogen maser is currently one of the most stable frequency standards currently available, providing frequency stabilities of several parts in 1 0 ' for averaging times of lo3 lo4 seconds. Further improvement to the stability of hydrogen masers requires a comprehensive understanding of the relative magnitudes of physical processes that influence frequency stability. We discuss an approach ...