Space Vector Modulated Direct Torque Control of PM Synchronous Motor with Initial Rotor Estimation

The direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) has become attractive because of its simplicity and fast torque response. However, mechanical sensors have caused problems to the system. It is possible to overcome the disadvantage if the initial rotor position is known. For the initial rotor position detection, the structural and magnetic saturation saliencies are frequently used. Since the conventional PMSM model does not incorporate the saturation saliency, this paper presents a nonlinear model of PMSMs which incorporates both the structural and saturation saliencies, which will enable the numerical simulation of new rotor position detection algorithms. In this model, the self and mutual incremental inductances of the phase windings are expressed as functions of the stator currents and rotor position. The incremental inductances of a surface mounted PMSM are measured. In addition to mechanical sensors, there are other problems of DTC, such as large torque and flux ripples. In order to overcome these disadvantages, space vector modulated (SVM) DTC has been applied. Based on the proposed motor model, the dynamic performance of a SVM DTC drive system is simulated. To verify the effectiveness of the proposed model, the simulation results are compared with those obtained by the conventional PMSM model in the Simulink power system toolbox library. Finally, an initial rotor position estimation scheme is investigated. Experiments based on the scheme are carried out and the effectiveness of the scheme is verified.