Multiple Harmonic Suppression Method for Induction Motor Based on Hybrid Morphological Filters

In order to solve the problem of torque ripple caused by current harmonic of induction motors (IMs) in electric vehicles (EVs) drive system, this paper presents a novel control method in the feedback channel based on morphological filters (MFs) to suppress the current harmonics. First, an analytical model of current harmonics is established, and the current harmonic composition to be filtered in the feedback channel of motor control systems is provided. Second, on the basis of filtering requirements on the feedback channel and the basic idea of mathematical morphology, a hybrid digital MF is designed. The MF is subsequently added on the current loop to suppress the current harmonic components. The shape, width and height of the structural elements of the filter are optimized by parameters comparison methods to improve the performance of the filter in harmonic suppression. Finally, compared with the method based on Butterworth Filter and without filters, simulation and experimental results verify the feasibility and effectiveness of the proposed method for suppressing harmonics.