Component damping evaluation in sub‐synchronous oscillation based on transient energy flow method

Abstract

In recent years, sub-synchronous oscillations have occurred frequently. Torsional interactions may cause oscillations in turbo-generator rotor shafts and thus huge losses. Conventional studies focus on the damping of system oscillation modes, but little on the damping of components, which could aid in finding out the source of a poorly damped or undamped oscillation. This study aims at a quantitative evaluation method of the damping characteristics of each component in torsional interaction. The transient energy flow method successfully applied in component damping evaluation and source location of low-frequency and ultra-low-frequency oscillations is further developed for that of sub-synchronous oscillation. The transient energy flow method evaluates the damping of a component by its dissipation rate of transient energy. A method of computing the transient energy flow in sub-synchronous oscillation is proposed. It is found that the rate of energy flow is relevant to the difference between the super-synchronous and sub-synchronous powers. The relation between the transient energy dissipation and the damping of a component is validated by both mathematical deduction and simulation results. The transient energy flow method can evaluate component damping and therefore locate oscillation sources effectively in sub-synchronous oscillation.