Study On Shaft Torque Amplification Caused By Subsynchronous Oscillation

It is determined by the geographical distribution of power source and load that the power grid must be capable with long distance and high capacity transmission. In order to enlarge the static stability limit of lines, series capacitive compensators are commonly used in high capacity turbine generator systems, which may raise the risk of subsynchronous oscillations. Especially, it could cause serious damage to the rotor when large disturbance occurs. Due to the complexity and non-linearization of power system, researches on transient amplification effect of torque mostly rely on the time-domain simulation which can not reveal its mechanism. Therefore, it is particularly important to research the mechanism of transient amplification effect of torque.Transient torque is generated at the moment of short circuit. Due to the big inertia of the mechanical part, the changes of velocity and angle of the rotor can be ignored. Taking the series capacitive compensators into account, the theoretical derivation originally focused on the network of fault components. The derivation shows that series capacitive compensators may alter the frequency and amplitude of AC components of transient torque. By simulations, the author verified and compared the influence on initial transient torque by series capacitive compensators.Transient torque leads to shaft torsional vibration response. Based on the decoupled multi-block model, the analytical solution of torsional vibration response is given and the amplitude trend caused by sinusoidal damp parameters. By simulations of an actual generator shaft model under a single shock and continuous shocks, the theory and analysis was verified.The transient amplification effect of torque is influenced by multiple factors in actual power system. Combined with the conclusions above, the impact factors including compensating rate, operating modes and disturbance are analyzed systematically.