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A Simplified Three Phase Three-level Zero-Current-Transition Active Neutral-Point-Clamped Converter with Three Auxiliary Switches

Fig. 1. Propose three-level ZCT ANPC inverter.
A novel three-level zero-current-transition active neutral-point-clamped inverter is presented in this paper. The proposed soft-switching topology employs only one auxiliary switch, one LC resonant tank to assist the main switching devices in one phase leg. The zero-current turning-off of all the main and auxiliary switches are achieved, meanwhile the turning-on losses of switches and reverse recovery losses of diodes are reduced without increasing the voltage stress of switching devices. What's more, the current rating of auxiliary device is much smaller than the main devices. The control scheme is simple and no additional sensor is needed and no need modification to the normal PWM strategy. The operation principles are analyzed and simulation results verify the analysis.

Fig. 2. Control timing of switches.
Fig. 3. Simulation waveform in one switching cycle for Iload>0.
Fig. 4. Simulation waveform in one switching cycle for Iload<0.