Improved Loss Minimization Control Based on Time-Harmonic Equivalent Circuit for Linear Induction Motors Adopted to Linear Metro

Abstract

By the supply of two-level voltage source converter with low switching frequency, the linear induction motor (LIM) adopted to linear metro suffers from time harmonics greatly, which would aggravate the airgap flux density, cause extra harmonic loss, and reduce working efficiency for the LIM and drive. In order to quantitatively analyze and reduce the neglective influence of time harmonics, one loss minimization control (LMC) scheme based on improved loss model is proposed in this paper. First, the traditional loss model under sinusoidal excitation is introduced. Second, after analyzing the main harmonic components of converter, one improved loss model based on the equivalent circuit under harmonic excitation is innovatively proposed in this work. Third, one novel LMC scheme with loss minimization cost function is developed, which can find out the optimal flux linkage to get the minimal loss for the LIM. Finally, the proposed loss model considering harmonic and LMC scheme have been fully validated by comprehensive simulation and experiments in terms of one 3 kW prototype.