Damping Torque Analysis of the Influence of Different Types of Dead Band on Ultra-low Frequency Oscillation

Abstract

The asynchronous interconnection between Yunnan Power Grid and the main grid of China Southern Power Grid has brought a series of frequency stability problems to the main grid of China Southern Power Grid. In the asynchronous network test in Yunnan and the subsequent DC blocking fault, two forms of frequency oscillation appear in the power grid. One type of oscillation is the divergence oscillation occurring near the rated frequency (f=50Hz), and Another type of oscillation occurs in the vicinity of the governor dead band (f = 0.05 Hz). In this paper, the causes of these two forms of oscillation are analyzed. When comparing the effects of different types of dead band, it is found that different types of governor dead band have different effects on the same input signal. Different output signals are analyzed by Fourier analysis method, and then analyzed by damping torque method. It is concluded that the two types of dead band have different amplitude reduction effects on the mechanical power of the system, which affects the system damping size and stable operation. And in the modified four-machine two-zone system model for time domain simulation, the results also prove the above conclusions.