The New High-Efficiency Hybrid Neutral-Point-Clamped Converter

This paper introduces a novel three-level voltage-source converter (VSC) as an alternative to known three-level topologies, including the conventional neutral-point-clamped converter (NPCC), many T-type VSCs, and active NPCC. It is shown that, operating in the low converter dc-link voltage range, this new solution not only can achieve higher efficiency than many typical three-level structures but also can overcome their drawback of asymmetrical semiconductor loss distribution for some operating conditions. Therefore, a remarkable increase of the converter output power capability and/or system reliability can be accomplished. The switching states and commutations of the converter, named here as hybrid NPCC (H-NPCC), are analyzed, and a loss-balancing scheme is introduced. Five- and seven-level H-NPCC topologies with loss-balancing features are also presented. Finally, a semiconductor-area-based comparison is used to further evaluate many three-level VSC systems. Interestingly, the total chip area of the proposed H-NPCC is already the lowest for low switching frequencies.