A direct torque control scheme of ALA synchronous reluctance machine and its DSP-based implementation

Recently much more attention has been paid to the axially laminated anisotropic (ALA) synchronous reluctance machine (SRM), for its high power factor, great power density and high efficiency, and so on. However, to increase the saliency ratio, the starting cages on the rotor are omitted so that the motor could not start up directly. In the inverter-driven applications, the synchronism between the rotor and the flux could be maintained by making use of the position/speed sensor. But the utilization of sensor will increase the cost and degrade the reliability, or not be applicable in some applications. In this paper, the sensorless direct torque control (DTC) scheme will be applied to ALA-SRM for good robustness and least parameter requirement excluding the stator resistance. It avoids the manipulation of complicated control scheme due to the saturation of parameters, especially the direct axis inductance L_d. The improvements of the integral of stator flux and the hysteresis control of flux magnitude are stated in detail. To validate the theoretical analysis, the whole system was simulated with Matlab and an experimental investigation on a DSP (TMS320LF2407A) controlled 2.2 kW ALA-SRM was implemented. The results verified that the DSP-based control of ALA-SRM is a competitive candidate.