Repetitive Control of Neutral-Point Voltage in NPC Three-Level Inverters Based on EID Compensation

Neutral-Point clamped (NPC) three-level inverters have a broad application prospect. However, the voltage imbalance of the capacitors and the drafting of its neutral-point voltage will generate voltage stresses on the switches and even increase the total harmonic distortion (THD) rate in their output. In this paper, an improved repetitive control method based on the idea of equivalent input disturbance (EID) compensation is adopted. By adding an additional neutral-point branch, the neutral-point voltage control problem is transformed into a disturbance suppression problem. The case studied are tested using MATLAB/SIMULINK software and the experiment results show that this proposed control strategy can overcome both periodic and non-periodic disturbance, restraining the voltage fluctuation at the neutral point to a lower level. Copyright (C) 2020 The Authors.