Torque-Ripple reduction in Permanent Magnet Synchronous Motor Based on LADRC and Repetitive control

A brand new compensation approach for voltage source inverters (VSIs), which is applied in PMSM and causes harmonic due to the dead-time, is presented in this paper. In terms of theory, a smooth torque can be acquired by tracking the accurate current in the synchronous reference frame. However, precise tracking requires strict bandwidth in the current loop, which is unrealistic to implement in conventional controllers. The presented method is based on the revised repetitive controller (RRC) and LADRC. The specific frequency harmonics caused by inverters can be reappeared by RRC. And the Extended State Observer (ESO) in LADRC can estimate the total unpredictable disturbance. This new compensation method is to parallel the repetitive controller with the current loop and replace the traditional PI controller with LADRC. The 6th harmonic ripple of torque is realized, and the control accuracy is improved. Finally, experiments and simulations have verified the feasibility of the scheme.