6. Overmodulation Methods with Low Distortion

This chapter delves into the challenges of voltage distortion in electrolytic capacitor-less motor drive systems, particularly when using traditional overmodulation strategies. The analysis focuses on the impact of DC-link voltage fluctuations on stator voltage distortion and the resulting increase in Total Harmonic Distortion (THD) of motor current. The core innovation presented is an overmodulation strategy based on dynamic voltage boundary regulation, which optimizes the overmodulation voltage boundary to mitigate switching aliasing and enhance system performance. The text provides a detailed explanation of the conventional dual-mode overmodulation strategy's limitations and introduces a fixed voltage boundary approach to address these issues. Experimental results demonstrate the effectiveness of the proposed strategy in reducing THD and improving the utilization of DC-link voltage. The chapter concludes with a summary of the main findings, highlighting the significance of the dynamic voltage boundary strategy in suppressing motor voltage and current harmonics and preventing modulation switching aliasing.