Output current balancing method for three-phase interleaved LLC resonant converter employing Y-connected rectifier

Abstract

This paper presents the output current balancing method for three-phase interleaved full-bridge LLC resonant converter which employs a Y-connected rectifier. The proposed Y-connected rectifier is capable of boosting the output voltage without increasing the transformer's turn ratio. Especially, the frequency of the output ripple of the rectifier is six times higher than the switching frequency, thereby reducing the output capacitor and the secondary transformer's RMS current. However, imperfections of resonant components cause the unbalance of output ripple current, and there are the limitations of individual control capability for each three-phase interleaving structure. To solve the current unbalance problem, a current balancing method is proposed for the output rectifying current. The performance of the proposed converter and the current balancing method has been verified through experiments using a 10 kW (300 V/33.3 A) prototype converter.