Mitigating Circulating Currents of Parallel Three-Phase Vienna Rectifiers with Unbalanced Filter Inductors

Parallel connections of three-phase Vienna rectifiers are commonly used to increase the power ratings of electric vehicle charging stations in recent years. However, parallel operation can create a path for zero sequence circulating current (ZSCC), particularly when the rectifiers are operating under interleaved modes with unbalanced filter inductors. To tackle out this issue, an integrated control scheme is proposed in this article. Based on these frequency components of the ZSCC, the proposed control scheme has two layers. The low frequency component of the ZSCC is mitigated by using PIR control in the inner current control loop under the rotational reference frame, while the high frequency component of the ZSCC is reduced by applying the Discontinuous Pulse Width Modulation (DPWM) technique with proper zero sequence injections. The effectiveness of the proposed control scheme is validated through both numerical simulations and hardware experiments.