Modulation strategy is one of the most important issues for three-level neutral-point-clamped inverters in three-phase transformerless photovoltaic systems. A challenge for modulation is how to keep the common-mode voltages constant to reduce the leakage currents. A single-carrier modulation strategy is proposed. It has a very simple structure, and the common-mode voltages can be kept constant with no need of complex space-vector modulation or multicarrier pulsewidth modulation. Experimental results verify the theoretical analysis and the effectiveness of the presented method.
I E E E Transactions on Power Electronics, 2013, Vol 28, Issue 6, p. 2635-2637
Common-mode voltage , modulation , neutral-point-clamped inverter , transformerless photovoltaic (PV) system