Abstract: To address the performance degradation of three-phase single-stage isolated PFC converters under parameter mismatch in model predictive control, this paper improves their predictive control strategy. First, a mathematical model of the converter is established, and its ultra-local model is analyzed. Based on this, a model-free predictive current control (MFPCC) with delay compensation is introduced into the current inner loop, thereby reducing the control system’s dependence on parameters and enhancing its robustness. For estimating unknown disturbances in MFPCC, an extended state observer combined with sliding mode control (ESMO) is adopted to achieve fast and accurate observation. Meanwhile, the switching control function in the sliding mode observer is improved to reduce chattering. The stability of the proposed extended sliding mode observer is further verified, demonstrating its effectiveness. Finally, to examine the robustness of the model-free control system, simulations and experiments are conducted to compare the responses of model predictive control (MPC) and model-free control under different disturbances. The results confirm the advantages and feasibility of the model-free control method proposed in this paper.