Three-Phase 12-Step Seven-Level Inverter with Planar Transformers for High-Frequency Applications

The demand for efficient and compact inverter solutions in electric drive systems, particularly in electric aircraft and other high-frequency applications, has prompted significant interest in multilevel inverter (MLI) topologies. Conventional MLIs are constrained by high switching losses and the complexity of modulation strategies, especially at fundamental frequencies above 2 kHz, the pulse-width modulation (PWM) techniques may become inefficient, as they require carrier frequencies nearly ten times the fundamental frequency or higher, significantly increasing switching losses in the converter. To overcome these challenges, this paper presents a new seven-level twelve-step inverter (SLTSI) that eliminates the need for high-frequency carrier-based PWM. The proposed inverter utilizes three planar high-frequency transformers and twelve switches to deliver high performance with a simplified control structure. Operating at the fundamental frequency, the SLTSI topology improves DC source utilization and achieves a peak phase voltage of 4 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{dc}$</tex> /3, leading to an enhanced levels-to-source ratio of 7/1. Comprehensive simulations and experimental measurements validate the inverter's performance and demonstrate its suitability for compact, high-speed motor drive systems.