Abstract: Considering to that the output voltage of Boost power factor correction（PFC）converter must be higher than the peak AC voltage,a cascaded DC/DC converter is needed when the load voltage is low,and two-stage power conversion is not conducive to the improvement of system efficiency.A single-phase three-port PFC converter is studied to optimize the instantaneous efficiency of the PFC converter within the grid voltage period and further improve the overall efficiency.Quasi single-stage power conversion between the AC input side and the DC load side is realized by directly using the low-voltage side capacitor of the traditional three-level Boost converter as load port and constructing a high-voltage port,which also effectively reduces the power conversion stages of the system and thus improves the overall efficiency.In addition,the characteristics of quasi single-stage power conversion are also conducive to reducing the voltage stress,current stress and power loss of the rear DC/DC converter,which further improves the overall efficiency of AC/DC converter.The working principle and control strategy of the three-port PFC converter are analyzed in detail,and the loss analysis model is established and verified by simulation.Finally,a 2 kW experimental prototype is used to verify the effectiveness of the proposed converter in system efficiency.