Three-level four-leg Voltage Source Inverter modulation techniques comparison for smart grids.

When developing smart grids applications, it is often desirable to generate unbalanced voltages in order to compensate different events in the grid. Besides, the power converters used in smart grids applications must be able to manage high power levels up to several MVA. In this sense, four-leg Neutral-Point-Clamped (NPC) power converters offer a suitable option for generating unbalanced voltages in applications within the power range of smart grids. Several modulation strategies can be found for this kind of power converters but a deep analysis is still needed in order to choose the best modulation technique in terms of voltage THD, power losses, computational load, etc when unbalanced voltages are generated. In this paper, different modulation strategies for four-leg NPC power converters are compared specially when generating unbalanced voltages. Simulation and experimental results validate the main conclusions obtained in the work.