Positive-Net-Damping Stability Criterion in Subsynchronous Oscillation

In recent years, the subsynchronous oscillation has arouse wide attention, and the oscillation of turbo-generator will cause serious influence. In general, the eigenvalue method and time domain simulation method are often used to analyze. The two methods focus on the system overall stability, and detailed structure and parameters of each element are required. However, the influence of components on oscillation is often difficult to obtain. In this paper, the positive-net-damping method is used to analyze the influence of the line on the torsional vibration. This method combines the complex torque coefficient method and Nyquist criterion, and divides the whole system into mechanical and electrical subsystems. Then the influence of each component on the damping coefficient can be obtained explicitly. After derivation and simulation verification, the system stability becomes worse at complementary frequency of line resonance frequency, and the line resistance may lead to poor stability.