Adaptive Virtual Admittance Based Current Harmonic Suppression Strategy for Totem-pole Bridgeless PFC Converter

In GaN totem-pole bridgeless power factor correction (PFC) converters, LC resonance from the electromagnetic interference (EMI) filter transforms grid voltage distortion into current harmonics, degrading power quality. A novel adaptive virtual admittance based current harmonic suppression method is proposed to improve the grid current quality across a wide load range. The input impedance model, accounting for the EMI filter and digital control delay, is established to reveal impedance variation patterns. The virtual admittance vector is decoupled in the polar coordinate system and optimized under different load conditions. Furthermore, a load-power-adaptive virtual admittance mechanism based on the piecewise cubic Hermite interpolation method is presented to suppress specific grid current harmonics. To ensure the robustness of the proposed method, the sensitivity of the virtual admittance and the influence of the system delay are analyzed. The experimental results show that the proposed method exhibits a better harmonic current suppression effect compared with conventional methods.