In the background of "double high", the oscillation accidents of the new energy grid-connected system are common, the equations contain quadratic nonlinear terms making the nonlinear coupling relationship between the oscillation modes, which cannot be completely decoupled, on this basis, the analytical equations for the interaction of nonlinear oscillation modes are derived to reveal its nonlinear oscillation mechanism, and the mechanism of the system generating internal resonance phenomenon is elaborated; With the development of new energy, different types of random excitations increase, and the "facing point ".Therefore, based on the general forced oscillation theory, the conditions for triggering internal resonance are further extended, and the phenomenon that the system oscillation mode frequency does not strictly satisfy integer multiples before internal resonance can occur under the action of narrow-band random excitation is found. Finally, the accuracy of the theoretical analysis is verified by Matlab simulation and semi-physical experimental platform.

high proportion of renewable energy power system,nonlinear interaction,oscillation mode interaction,internal resonance,general forced oscillations