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

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.