Virtual Admittance Feedforward Compensation and Phase Correction for Average-Current-Mode-Controlled Totem-Pole PFC Converters

Featured Application This paper proposes virtual admittance feedforward compensation and phase correction for average-current-mode-controlled totem-pole PFC converters. It can effectively reduce total harmonic distortion (THD) and improve the power factor (PF) of the converter. The proposed control strategy can be directly used in on-board chargers (OBCs) for electric vehicles, power supplies for server clusters, communication equipment, industrial equipment, etc.Abstract This paper explores a current distortion problem in totem-pole bridgeless power factor correction (PFC) converters with average current mode (ACM) control. With in-depth modeling for the current and voltage loops, it was found that the current distortion is caused by the limited current loop bandwidth and input filter capacitor. These factors lead to the presence of a susceptance component in the input admittance, which degrades the power factor (PF) and total harmonic distortion (THD) of the PFC converter. To solve this problem, this paper proposes virtual admittance feedforward compensation (VAFC) and phase correction methods to adjust the input admittance to pure conductance. The VAFC can generate virtual admittance that compensates for susceptance components in the input admittance, while phase correction can generate an equivalent current source that offsets the current in input capacitors. Furthermore, a phase lock loop (PLL) is introduced to realize the VAFC, which reduces the feedforward interference caused by input voltage sampling noise. Finally, an experimental prototype was built to verify the effectiveness of the proposed strategies. According to the test results, the proposed compensation strategy improves the PF by 1.23%, while reducing the THD by 2.52% and achieving a peak efficiency of 98.69%.