This article proposes an improved nonlinear extended state observer-based model-free predictive current control (MFPCC) with an extended control set. First, the nonsmoothness problem of conventional nonlinear extended state observer model-free solutions is explained. By constructing a high-smoothness polynomial series at the transition points of the piecewise nonlinear function, an improved nonlinear extended state observer is designed to enhance the performance of the MFPCC, and relevant stability proofs are derived by the Routh criterion. Furthermore, a newly designed extended control set based on the voltage vectors (VVs) at the center of triangular subregions (TSs) of the modulation area is proposed to improve the output voltage accuracy. Based on the geometrical characteristics of the subregion center VVs, a fast-layering selection method is proposed to reduce the complexity of determining the optimal VV. Finally, experimental results are presented to verify the proposed method's feasibility and effectiveness.