Voltage balancing strategy based on reference vector angle prediction for three-level shunt APF

In order to maintain the neutral-point voltage balance of neutral-point-clamped (NPC) shunt active power filter(APF), a neutral-point voltage balance strategy based on reference vector angle prediction is proposed in this paper. The proposed approach considers the effect of every vector on neutral-point voltage and corresponding switching sequences for the reference vector in each sector. By modifying the reference vector angle to select optimized switching sequences, the approach maintains dc-bus capacitor voltage balance and reduces neutral-point voltage ripples. Simulation is performed in Matlab to verify the validity and effectiveness of the proposed approach.