Analysis of neutral-point voltage with fundamental oscillation for three-level PV converter under imbalanced grid conditions

In low-voltage ride-through or unbalance grid voltage condition, the fundamental fluctuation in the neutral-point (NP) voltage of three-level voltage source converter will appear under imbalanced grid voltage situation and has not been researched in detail. A new NP current model under imbalanced grid is developed to investigate the limitations of conventional nearest-vector modulation and to give a more intuitive insight to solve this problem.