Neutral point voltage balancing of five-level inverter fed by twelve-pulse rectifier

The paper presents 5-level, neutral point clamped, H-bridge inverter fed by 12-pulse rectifier. Two configurations of rectifier and inverter neutral point connection are studied: the first configuration with disconnected neutral points and the second configuration with connected neutral points. Furthermore, novel neutral point voltage balancing methods suitable for the presented configurations are proposed. Extensive simulation results of the proposed configurations with the neutral point voltage balancing methods are presented. The simulation results deal with aspects such as total harmonic distortion (THD) Factor of the inverter output currents, and voltages, grid current, harmonic content, frequency spectrum distribution. The results confirm the effectiveness of the proposed methods. The voltage balancing methods are compared and their advantages and disadvantages are explained.