An Improved Auxiliary Resonant Pole TNPC Inverter and Its Modulation Strategy

The modulation strategy of the auxiliary resonant commutation circuit (ARCC) of the original auxiliary resonant pole three-level T-type inverter (ARPT-TNPC) is complicated and the main switch of the ARPT-TNPC cannot realize soft switching. To address the issues, this article proposes an improved ARPT-TNPC inverter and gives a suitable modulation strategy for the improved ARCC. Compared with the original ARPT-TNPC inverter, this inverter can first ensure the soft-switching of all switches, avoiding the problem that the main switch cannot realize the soft-switching, which can further improve the inverter efficiency. Second, the ARCC operates only during the dead time, thus reducing the auxiliary switch operation time. Meanwhile, the modulation strategy of this ARCC is not affected by the phase commutation process. Finally, this ARCC does not participate in the control of the main circuit, the control of the ARCC and the main circuit is independent of each other, which helps to reduce the overall control complexity of the inverter. The topology, operating principle and corresponding design principles are given in the article, and finally the effectiveness of the ARPT-TNPC is experimentally verified.