Virtual Current Constraint Based Segmented Trajectory Control Strategy for Flux-Weakening Operation of SPMSM Drives

This article proposes a virtual current constraint based segmented trajectory control strategy for surface-mounted permanent-magnet synchronous motor drives, to improve the transient performance under the flux-weakening operation. In the conventional scheme, the operating points (OPs) are arranged on the current constraint circle during the speed-rising process to provide the maximum electromagnetic torque. After the target speed is reached, there still exists an inevitable transition process that moves OP from the current constraint circle to the steady-state operating point (SSOP), leading to the speed overshoot, oscillation, and prolonged settling time. To solve this issue, a variable virtual current constraint is proposed to replace the fixed one. Based on the developed virtual current constraint, a novel operating point trajectory is designed, where SSOP and the target speed can be reached simultaneously without extra transition processes. Furthermore, to generate the virtual current constraint, a dual-variable based constraint method is put forward and applied to the output limitation of the speed controller. Compared to the conventional schemes, the transient performance can be significantly improved, where the speed overshoot and oscillation are eliminated, and the settling time is greatly shortened. Simulations and experiments are carried out to validate the effectiveness of the proposed scheme.