Fault Current Analysis Method for IIRES Considering the Transient Processes of both the PLL and the Current Inner Loop

To address the challenges posed by the high proportion of renewable energy integration in new type power systems on protection, it is essential to analyze the fault characteristics of renewable energy sources. Renewable energy is often integrated into the grid in the form of inverter-interfaced renewable energy sources (IIRES), and the phase-locked loop (PLL), as a crucial control component for grid integration, directly affects the fault characteristics of these inverters. This paper proposes a fault current analysis method for IIRES that accounts for the transient processes of both the PLL and the current inner loop. By examining the impact of the PLL on the Park transformation, the paper clarifies the influence path of the PLL on the fault current of IIRES. Additionally, it simplifies the effect of the PLL on the transient process of the current inner loop, deriving fault current analytical expressions related to the parameters of both the PLL and the current inner loop. The results are validated through comparison with simulation waveforms.