Characteristics Analysis of Current-Controlled VSCs for Periodic Forced Oscillations Excited by Grid Frequency Disturbance

Uncontrolled forced oscillations can jeopardize the power system security. Most modeling and analysis methods for forced oscillations in previous publications were linearization methods such that some new nonlinear oscillation phenomenon can not be reproduced powerfully. Based on the considerations above, this paper hopes to provide clearer understandings and recognitions to forced oscillations by theoretically reveal the characteristics. First, a dynamic model of the current-controlled VSCs system based periodic forced oscillations is established to describe the relationships between system parameters and intrinsic quantities. Then, the multi-scale method is introduced to derive the mathematical expressions of approximate analytical solutions and relationship equation. Next, these characteristics, containing jumping phenomenon, frequency shift, doubling frequency response, and frequency coupling, are found and described by analyzing the mathematical expressions. Final, all the results are tested and verified on simulations and experiments.