Torque Maximizing and Flux Weakening Control of Synchronous Machines

In this thesis, the torque maximizing and field weakening control strategies for synchronous machines with magnetically anisotropic structure such as synchronous reluctance machines (SyRMs) and interior permanent magnet machines (IPMs) are studied. In order to obtain maximum torque using minimum stator current, the maximum torque per ampere (MTPA) control strategy is employed below the base speeds. The MTPA control is limited by the maximum available voltage of the motor. Therefore, field weakening (FW) control is employed in order to achieve speeds higher than base speed. To obtain maximum torque while effectively reducing the stator flux at the same time the maximum torque per volt (MTPV) is employed at high speeds. The control techniques are realized using direct flux vector control (DFVC) strategy. Performance of the DFVC technique is analysed in unsaturated and saturated magnetic conditions. Robustness of the technique against parameter variation is evaluated by a series of loading tests. Performance of the DFVC is then evaluated by comparing it with the rotor oriented current vector control. Simulations are performed from experimental data of 7.5 kW IPM drive