Common-Mode Resonance Current Suppression Method for the Transformerless Reduced Switch Count Three-Level Inverter With LCCL Filter

The LCCL filter can be employed with the transformerless inverter to mitigate the leakage current, which however generates the common-mode resonance current (CMRC) and oscillations in the inverter-side currents. Owing to the inherent features of the reduced switch count three-level inverter (RSC-TLI), the medium vectors are unable to be generated, which implies that the conventional method cannot be applied straightforward. This article presents a novel strategy to suppress the CMRC in the RSC-TLI with LCCL filter, which regulates the duty cycles of small vectors by using distribution factors. Compared to conventional passive damping technique, the CMRC and leakage current are restrained by the presented strategy. As a result, the oscillations of inverter-side currents are mitigated, while the system cost is reduced. Evaluation results confirm the feasibility of the presented method.