A novel efficient T type Three level Neutral-Point-Clamped inverter for renewable energy system

The I type 3L-NPC (Three-level Neutral-Point-Clamped) converter is the most popular multilevel converter used in the renewable energy system for its low switching loss, reduced devices voltage stress. However, it suffers from problems of high conduction losses. The T type 3L-NPC is researched in the literatures to overcome the drawbacks of I type inverter. But, the high side and low side power devices of T type 3L-NPC need to block the whole dc link voltage. The switching frequency is significantly limited due to the high switching losses caused by the high voltage rated power devices. In this paper, based on the drawbacks of both the I and T type 3L-NPC, a novel efficient T type 3L-NPC for renewable energy system is proposed to achieve both low conduction losses and switching losses with high switching frequency. The proposed topology and control strategy are successfully applied in the solar inverter system.