An Oscillation Modal Analysis Method for Power Systems Under Stochastic Continuous Disturbances

The large-scale integration of renewable energy has introduced significant stochastic continuous disturbances (SCDs) into power systems, fundamentally altering their oscillation modal characteristics. These disturbances cause originally finite oscillation modes to expand into infinite sheet-like regions on the complex plane and may generate new modes, rendering traditional eigenvalue-based modal analysis inadequate. To address this issue, a novel oscillation modal analysis method is developed based on the Fokker–Planck–Kolmogorov (FPK) equation derived from the stochastic differential equations governing system dynamics under SCDs. Through variable separation, the modal analysis is reformulated as an eigenvalue problem of a partial differential operator. An estimation approach is then proposed to identify the distribution ranges of the resulting sheet-like eigenvalues, including the procedure for locating and traversing these ranges. Validation on modified IEEE 39-bus and 118-bus systems confirms the method's accuracy and effectiveness in capturing oscillation modes under SCDs.