Frequency-locked and quasiperiodic (QP) oscillations in power systems

It is known that quasiperiodic (QP) oscillations can occur when an unloaded power transformer at the end of a long line is energised [10]. This occurs when the effect of the core loss of the transformer 'becomes negligible' due to stiff nonlinear characteristic of the core [4]. Usually such a system is known to exhibit periodic or frequency-locked behaviour. Such a system is an equivalent form of 'two nonlinearly coupled oscillators' and the transition from frequency-locked to quasiperiodic behaviour and vice versa depends on the strength of nonlinear coupling between the oscillators. This aspect is being examined in this paper.