Split Capacitor Ripple Reduction Method of 3-Level NPC Converter Using Zigzag Transformer

In the case of Neutral Point Clamped (NPC) converter, the 3
^rd
harmonic component of the capacitor neutral point current causes voltage ripples to each DC link capacitor. The capacitor’s low-order harmonic voltage ripples cause distortion in the converter output and reduce the stability of the system. Therefore, when the output of the converter increases, the ripple component of the capacitor also increases, so that a capacitor with a higher capacitance is required to ensure the reliability of the NPC converter. In this paper, a technique to reduce DC link capacitor voltage ripples by compensating the 3
^rd
harmonic voltage of the DC link capacitor of a 3-level NPC converter with the output offset voltage using a zigzag transformer is proposed. The proposed technique was verified through both simulations.