Efficiency-Optimizing Direct Torque Control of Permanent Magnet Synchronous Machines

Direct torque control (DTC) appears as an effective and practical control scheme for permanent magnet synchronous (PMS) motor drives. Different optimization methods are proposed to enhance the performance of conventional DTC. To the best of authors´ knowledge, the efficiency optimization of PMS motors under DTC has not yet been reported. The main contribution of this paper is an off line control method for optimization of steady state efficiency of permanent magnet synchronous machine under DTC. In the proposed DTC approach, the flux command is obtained based on an optimization procedure to yield a maximum efficiency over a wide motor operating range. Analytic determination of optimum stator flux linkage for loss minimization has been introduced. In addition, graphical interpretation of optimization procedure has been presented. Simulation results confirm the effectiveness of the proposed DTC