Cross-Timescale Interaction Analysis Between Current Control and Rotor Speed Control Timescale Dynamics in a High-Proportion DFIG-WT System

Abstract

Power electronics (PE) equipment contains multiple timescale energy storage components and control loops. As a result, the dynamic process presents multiple timescale characteristics in PE-dominated power systems. For simplicity, single timescale dynamics are often the focus of corresponding analysis, and the influence of different timescales (i.e., cross-timescale analysis) is rarely considered. However, there is an interaction effect between multiple timescale controls and energy storage components, which complicates system dynamics. In this study, the cross-timescale impact of current control on the dynamics of rotor speed control timescale are evaluated. First, based on a two-machine two-area system comprising a phase-locked loop (PLL)-synchronized doubly fed induction generator (DFIG)-based wind turbine (WT), the influence of the PLL on cross-timescale interactions is revealed via modal analysis. Then, a current control equivalent circuit is derived for analyzing its cross-timescale influence on rotor motion, and the LC resonance mechanism related to the current control is revealed. Moreover, the impact of the PLL on cross-timescale interactions is elucidated. Finally, the cross-timescale influence phenomena and mechanisms are verified via real-time digital simulations.