Harmonic Current Control of OW-PMSM for Low-Voltage Traction by Nonlinear Disturbance Rejection with Improved Modulation Scheme

The open-winding permanent magnet synchronous motor (OW-PMSM) has been developed, mostly potential for low-voltage traction in electric vehicles. Yet, both the disturbance from vehicle system under driving and the motor with low-reactance (LR) feature expose the limits of traditional controllers that are prone to great current harmonics. Therefore, the current control for LR OW-PMSM becomes challenging. The main objective of this research is to provide a current harmonic control strategy for LR OW-PMSM by the nonlinear lumped disturbance observer (NLDO) combined with improved space vector modulation (SVM) scheme. The existence of nonlinear, unknown, unmodeled factors has been confirmed by current measurement and harmonic analysis in full operation range, and thus is considered in proposed controllers. The NLDO is designed for all the three axes under the dq0 frame. The SVM algorithm is adjusted to two switching patterns in order to get widened linear voltage modulation range. In addition, in the 3-D voltage space is the possible modulation area investigated. Ultimately, the target LR OW-PMSM has been designed, prototyped, and tested. The proposed NLDO, juxtaposed with ordinary PI and deadbeat controllers, reduces current harmonics on both the motor and inverter sides, possesses high robustness, and is practical for LR motors, according to experimental results.