Influencing factors and propagation mechanisms of sub-synchronous oscillations in complex AC–DC grid

The modern power system exhibits typical “double-high” characteristics as a result of the extensive use of new energy sources like wind and photovoltaics that are connected to the electrical grid, and as a result of this development, sub-synchronous oscillations are becoming an increasingly significant issue. There is an urgent need to research the main influencing factors and propagation mechanism of SSO in complex AC–DC grid since they have a wide range of propagation properties. In this article, the propagation mechanism based on the sub-synchronous power propagation divider coefficient is proposed, and a quantitative analysis approach based on the maximal information coefficient (MIC) of the influencing factors of sub-synchronous oscillation propagation is clarified. The results demonstrate that the power flow on AC transmission is the key factor affecting the propagation of the SSO power’s AC component, the AC transmission resistance characteristics at the frequency of the sub-synchronous oscillation is the main factor affecting the propagation of SSO power’s DC component, and the sub-synchronous power propagates in the complex system according to the diversion coefficient of circuit branch. The efficiency of the method and mechanism proposed in this paper is confirmed by the simulation results.