Asymmetric SVPWM and Error Suppression Method for Current Reconstruction of T-type Three-Level Inverter

Phase current is crucial for closed-loop control and system monitoring of a T-type three-level inverter (TThLI). However, the traditional space vector pulse width modulation (SVPWM) method cannot fully meet the minimum sampling time, which leads to the emergence of unobservable areas (UAs) in the neutral current sensor (NCS) phase current reconstruction system of TThLI. Moreover, the current zeropoint drift (ZPD) caused by temperature drift, aging, and noise affects the accuracy of NCS sampling. Regarding the issues above, this paper investigates the impact of UAs and ZPD on the NCS phase current reconstruction system and proposes an asymmetric SVPWM and error suppression (APES) phase current reconstruction method. The proposed method comprises two links: asymmetric SVPWM (ASVPWM) and ZPD error suppression. Firstly, the ASVPWM regulates the PWM waveforms according to composite zero vector and volt-second balancing principles and then generates three observable vectors whose dwell time is greater than the minimum sampling time to eliminate the UAs. Secondly, the ZPD errors are obtained and suppressed through the dynamic current triple sampling mechanism to improve reconstruction accuracy. Finally, experimental results show that the proposed APES method achieves an accuracy of 3.51% at the expense of a slight increase in total harmonic distortion.