Mechanism and Measurement of Ultra-Low-Frequency Oscillations in Asynchronous Networks

The asynchronous interconnection mode between the Yunnan Province Power Grid and China Southern Power Grid was implemented in 2016. However, during the practical experiment of raising HVDC power in the asynchronous mode, the frequency of the Yunnan Power Grid oscillated at ultra-low frequency for a long period. The present study includes a detailed analysis of experimental data, which indicates that the hydro unit governor system is the direct reason for the oscillation. Furthermore, the mechanism of governor systems for negative damping during oscillation is analyzed. A measure to optimize the proportional and integral (PI) parameters of the hydro unit governor is proposed using off-line simulation tools. Experiments on the actual power grid verified the effectiveness of the measure.