Verification of current sensorless control for single-phase NPC multilevel inverter

The current control is becoming a challenging task for switched mode power supplies, while current sensorless control solutions can avoid the instantaneous current measurements that has been applied for mostly used power factor correction topologies. However, multilevel type of converters haven´t been considered to use with current sensorless control (CSC). Hereby, the CSC is applied to three level neutral point clamped converter, where special volt-second balance is applied to inductor in order to keep average inductor´s current value to track the reference signal during both discontinuous and continuous current modes. The explanation of post-fitting and pre-fitting current trajectories is done that are necessary for proper transition between voltage levels. Experimental results have confirmed the theoretical model.