Neutral-point Voltage Control of Three-level NPC Inverter for Three-phase APF based on Zero-sequence Voltage Injection

Active Power Filters (APF) have already adopted the three-level inverter topology in medium-voltage and high-power applications for solving power-quality problems. The Neutral-point voltage clamped (NPC) Inverter because of its robustness has become a matured and broadly used topology. It is necessary to maintain the neutral-point voltage at the DC-side as close to zero as possible. The focus of this paper is on the neutral-point voltage control of the three-level NPC inverter based on multicarrier PWM by manipulating the dwell time of small vectors by injecting a zero-sequence voltage into the modulating signal. The effectiveness of the presented method on a three-level NPC inverter is validated via simulation in MATLAB/ Simulink. The results confirm the efficacy of the method in maintaining the neutral-point voltage at a minimum value with the desired overall good APF compensation characteristics.