Minimization of Current THD of Single-Phase PFC using Variable Switching Frequency

The current total harmonic distortion(THD) in grid-connected converters must be lowered to improve efficiency and meet grid connection standards. In this study, closed-loop current control was performed by applying variable switching frequency, which minimizes THD at the same average number of switching times per fundamental period for full-bridge PFC. To achieve this, the switching frequency maintaining a constant current ripple size was calculated. Then, the pulse width of the PWM carrier wave changes in time to implement variable switching frequency. The results of the offline simulation and hardware-in-the-loop simulation showed that, compared with the fixed frequency method, THD was reduced by applying the proposed variable switching frequency.