Active Thermal Control and Power Loss Reduction Scheme for Three-level Active Neutral-Point-Clamped Inverters with Hybrid Modulation

High power density and long service life are always the development requirements of power converters. This purpose has affected the selection of the power converter stage. Among many mature topologies, neutral point clamped (NPC) and its derived topologies are widely applied because of their superior performance, such as low voltage stress, low harmonic distortion, et al. However, a major disadvantage of NPC topology is the unbalanced losses between power switch devices, which leads to an unbalanced thermal distribution of switches. Thermal unbalance will limit the improvement of power density and shorten the service life of the converter. In this article, an active thermal control (ATC) scheme with hybrid modulation is proposed for the active NPC (ANPC) topology, where replacing the two clamping diodes of NPC topology with controllable power devices. It can reduce the total power loss of inverters and keep the thermal balance of the switches. The proposed scheme is verified and compared with the traditional control and modulation schemes on a low-power experimental platform. Experimental results have verified the effectiveness of the proposed ATC method.