| Summary: | In the high voltage power supply of the negative ion source neutral beam injection system (NNBI) accelerator, the three-phase three-level neutral point clamping (NPC) inverter, as an inverter module, has a detectable DC component in its output. When it flows into the step-up transformer, it will lead to increased transformer loss and excitation saturation, thus reducing the service life of the transformer and increasing potential safety hazards. This paper analyzes the causes of the DC component of the NPC inverter, and a reliable DC component suppression method based on double-loop control is proposed. A suitable PI controller can effectively suppress the output DC component during the power supply operation by establishing the transfer function between the output DC component and the regulation rate of the switch’s duty cycle. Finally, the prototype experiments verify the effectiveness of the control method successfully.
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