Current Sharing Analysis of Three-Phase Interleaved LLC and Optimization Method to Reduce the Influence of Stray Inductance

Three-phase interleaved LLC is widely used because it can increase power capacity and reduce output current ripple. However, this paper found that the three-phase interleaved LLC with all the resonant components using the delta connection (full- 11111111111111 type) has poor current sharing characteristic. This paper establishes the current sharing analysis model of three-phase interleaved LLC, explains the reasons for its poor current sharing effect, and proposes that changing the resonant capacitor to Ytype (111111111111-Cr-Y type) can improve the current sharing effect. Furtherly, to reduce the influence of stray inductance asymmetry on the current sharing, taking the 111111111-Cr-Y type as an example, this paper deduces the equivalent circuit model including stray inductance and proposes a current sharing optimization method without additional components. The proposed method can obtain the stray inductance of the three-phase resonant tank. Based on the stray inductance, the resonant inductance can be adjusted to obtain a better current sharing effect. Finally, the proposed model and optimization method are verified by simulation and experiments. Compared with the full-11111111111 type, the proposed 111111111111111-Cr-Y type shows higher current balance performance, and the proposed optimization method can further reduce the line current unbalance factor by more than 85%, and the phase current unbalance factor by more than 60%.