Digital control for a three-phase transformerless bi-directional photovoltaic inverter with wide inductance variation

This paper presents a digital control taking into account wide inductance variation for a 3ψ transformerless bi-directional PV inverter in dc distribution applications. The proposed control, combining feedback and feedforward controls, is derived with an equivalent three-phase NPC circuit model (i.e., three single-phase inverters) and based on D-Sdigital control, instead of the conventional space-vector approach and abc to dq transformation. Experimental results measured from a 3.3 kVA three-phase bi-directional NPC inverter have been presented to confirm the proposed control approach.