Grid Connected Modes of Sensorless PUC Inverter

In this paper a new mode of operation has been introduced for Packed U-Cell (PUC) inverter. A sensor-less voltage control based on redundant switching states is designed for the PUC5 inverter which is integrated into switching process. The sensor-less voltage control is in charge of fixing the DC capacitor voltage at half of the DC source value results in generating symmetric five-level voltage waveform at the output with low harmonic distortion. The sensor-less voltage regulator reduces the complexity of the control system which makes the proposed converter appealing for industrial applications. An external current controller has been applied for grid-connected application of the introduced sensor-less PUC5 to inject active and reactive power from inverter to the grid with arbitrary power factor while the PUC auxiliary DC bus is regulated only by sensor-less controller combined with new switching pattern. Experimental results obtained in stand-alone and grid-connected operating modes of proposed PUC5 inverter prove the fast response and good dynamic performance of the designed sensor less voltage control in balancing the DC capacitor voltage at desired level.