Two methods to control neutral-point voltage fluctuation for a hybrid VIENNA rectifier

This study presents two neutral-point balance control methods for a hybrid VIENNA rectifier, which is composed of a parallel system of a single-switch three-phase Boost rectifier and a VIENNA rectifier. Each rectifier in this topology processes part of the output power, therefore, a highly efficient and reliable performance is achieved in this rectifier system. However, the unbalance voltage of two DC-link capacitors in the VIENNA-type three level rectifier is also reflected in this hybrid rectifier. The fluctuation reason in neutral-point has been analysed using a mathematical model, meanwhile, the two methods with a hybrid algorithm and a simplified method based on zero-sequence component injection are proposed to control neutral-point fluctuation in this hybrid rectifier system. Furthermore, the performance comparison between these two methods is provided. The effectiveness of the two control methods has been verified using experimental results.