The nonlinear modes analysis of multi-infeed AC/DC parallel system based on norm form theory

Traditional eigenvalue analysis can not reveal the nonlinear interaction of power system. However, norm form theory makes nonlinear system 2-order or n-order equivalent to one linear system, when used in analysis of power system stability, it has the advantage of eigenvalue analysis widely used in power system and takes the nonlinear interaction between different oscillatory modes into account, so it can be suitable for low-frequency oscillation study after power system is subject to large disturbance. So in this paper, the norm form theory is applied to the nonlinear mode interaction of power oscillation for a dual-infeed AC/DC system. The result shows that the interactions between several oscillating modes are different in different operating condition, and when the system is heavily stressed with DC power modulation, the interaction between interarea oscillating mode and DC power control mode is the strongest, and the time simulation validates the conclusion.