Bipolar Output Voltage Control Strategy for Three-Level Neutral-Point Clamped Converter for Low-Voltage DC Distribution System

This paper proposes a bipolar output voltage control strategy for a 3-level NPC converter for LVDC systems. The proposed method compensates for the DC and AC imbalance between the bipolar outputs by injecting DC and AC offsets into the PWM reference. The effectiveness of the proposed method has been verified with simulation results compared to the conventional bipolar output voltage control methods and experimental results using a 400-kW 3-level NPC converter prototype.