Small-Signal Stability of RPG Grid-Tied System Considering the LPF Structure of DDSRF Control

Negative sequence control has been the grid core of renewable power generation (RPG) grid-tied system. As a commonly used control for positive and negative sequence separation process, the dynamic of the decoupled double synchronous reference frame phase-locked loop (DDSRF-PLL) has drawn much attention. As a core structure of DDSRF, low-pass filters (LPFs) introduce phase delays, reduce system response speed, and may even lead to system instability. Although existing studies have focused on the parameter optimization of LPFs, their structural impact remains underexplored. Therefore, this paper employs the trajectory linearization method to establish the linear time-periodic (LTP) small-signal model of the RPG grid-tied system considering DDSRF, addressing the challenges posed by nonlinearities and time-varying dynamic coupling in modeling. Then, we investigate the impact of the structure effect of DDSRF on system stability. Through comparative analysis, it reveals that eliminating a specific LPF can significantly enhance system stability. Finally, the analysis results are verified by time-domain simulation.