Velocity Control for Sideband Harmonics Compensation in Permanent Magnet Synchronous Motors With Low Switching Frequency Inverter

The existing methods for improving the control performance of permanent magnet synchronous motors (PMSMs) do not consider the effect of sideband harmonics during the intrinsic switching process in inverters. Undesirable sideband harmonics increase when the switching frequency of inverters is not sufficiently high compared to the fundamental frequency. These large sideband harmonics lead to torsional oscillations, which may severely damage motion control systems. In this article, we propose velocity control to reduce sideband harmonics in PMSMs with a low switching frequency inverter. The proposed method consists of a velocity controller and a sideband harmonics compensator. The desired dynamics for velocity tracking are developed via a PMSM model. The velocity controller is developed to improve velocity control performance using the desired dynamics. The sideband harmonics compensator is designed by utilizing sideband harmonics dynamics, which are proposed to suppress the main components of the sideband harmonics. First, a sideband harmonics observer is developed to estimate the sideband harmonics using sideband harmonics dynamics. Then, the sideband harmonics are rejected by the sideband harmonics compensator. The stability of the closed loop is proven by employing the input-to-state stable property. The performance of the proposed method is validated via experiments.