Modeling and Management of Overmodulation-Induced Harmonics for Induction Motor Field-Weakening Control

Overmodulation is essential for maximizing torque output of induction motor drives in the field-weakening region. However, it inherently introduces low-order voltage harmonics that degrade current quality and cause torque pulsations, accelerating insulation aging and bearing wear in high-power drives. Existing methods lack quantitative harmonic-torque tradeoff analysis and systematic management. This article proposes a three-level harmonic management framework with three contributions. 1) A vector-analysis-based harmonic model quantifies how torque gain and harmonic distortion vary with modulation index and speed. This enables derivation of a practical modulation boundary that maximizes torque while constraining harmonics at source level. 2) A complex vector generalized integrator scheme extracts harmonic components from both current controller and flux observer feedback paths. This preserves regulation accuracy and field-orientation consistency at feedback level. 3) An adaptive torque-harmonic tradeoff mechanism adjusts torque demand based on harmonic severity at reference level rather than suppressing harmonics. This mechanism operates transparently above the underlying space vector pulse width modulation layer. Experimental results show that the proposed method reduces slip angular frequency oscillation by 60.9% under load disturbance and sixth-order torque harmonic by 91.3%, significantly suppresses d–q current pulsations while preserving dynamic response, and maintains comparable torque capability with only a slight reduction in maximum sustainable load from 50% to 45% rated load. The method is well-suited for wide-speed-range applications such as electric vehicles, traction drives, and high-power industrial drives, where lower harmonic losses and smoother torque delivery enhance reliability, outweighing the marginal torque reduction.