Non-linear control of a boost PFC converter with a small inductor based on feedforward correction and frequency variation

To reduce total harmonic distortion (THD) and improve the power factor (PF) of a boost power factor correction (PFC) converter, here, the authors propose a non-linear control algorithm that includes the feedforward correction (FC) algorithm in the continuous conduction mode (CCM) and the non-linear frequency variation (FV) algorithm in the mixed conduction mode (MCM). The proposed FC algorithm achieves current out of distortion through zero crossing with a lower current loop bandwidth. The proposed non-linear FV algorithm achieves high PF and low THD under minimal load conditions. The non-linear FV algorithm comprises a third harmonic extraction algorithm, a harmonic control loop for reducing THD and a frequency production algorithm. By using this non-linear FV algorithm, the inductor size is reduced, which leads to lower cost and also achieves better THD and PF. The proposed algorithms are verified experimentally in terms of current tracking, current THD, PF, heating and loss on a 2000-W boost PFC converter hardware prototype.