Abstract: The unbalanced capacitor voltage will lead to the inconsistent pressure of the internal and external switches of the three-level converter topology, resulting in the distortion of the output voltage, which seriously affects the safe and stable operation of the device. In this paper, the neutral point voltage regulation of the multi-phase three-level H-bridge converter for ship propulsion is studied. First, the causes of neutral point voltage imbalance in three-level H-bridge inverter circuit are analyzed. Then, a conventional neutral-point voltage control method suitable for three-level multi-phase H-bridge topology is studied. However, the controllable region of neutral-point voltage under this method is limited by load power factor, thereby limiting the balance ability of low-speed and low-power factors. On this basis, a neutral-point voltage balance control method under full power factor range is proposed. The injected zero-sequence component is determined according to the voltage signal sector, and then the component in phase with the load current is added, which has faster balance speed and higher steady-state accuracy under low power factor conditions. Finally, the feasibility and correctness of the optimization method are verified by simulation and experiment.