A New Switching Strategy for a GaN-based Three-Level Active Neutral Point Clamped Converter

This paper investigates a suitable switching strategy for a GaN-based three-level active neutral point clamped (3L-ANPC) converter. The 3L-ANPC operation is considered at 800V DC bus with the use of 650V GaN devices. The different switching modes for obtaining the zero state result in short-loop and long-loop commutations. A parallel operation of zero states termed full-mode is preferable for reducing conduction losses. However, this results in a multi-loop commutation producing high voltage stress across the inner devices. This paper proposes a modified full-mode switching strategy to mitigate this issue by a timed switching sequence involving clamping devices. The proposed switching mode involves active switching of the clamping device in 3L-ANPC for coupling and decoupling the long loop path. The commutation process for the proposed switching mode is explained in detail in this paper. Simulation results are presented using the device Spice model and parasitic inductances of a designed 3L-ANPC phase leg. The voltage stress and loss results determined from simulation results are compared with existing switching modes. A three-level double pulse test circuit is presented, and experimental test results are provided for the proposed switching mode.