Direct Torque and Flux Control of Synchronous Reluctance Motor Drives in the Rotor Reference Frame Using Normalized Deviation Equations

This paper presents an enhanced direct torque and flux control method for synchronous reluctance motor (SynRM) drives based on normalized deviation values of the two-axis stator current components in the rotor reference frame. The proposed method is independent of the machine inductances, and only requires the stator resistance to estimate the amplitude of the stator flux. To derive the control relationship based on deviations, partial derivatives are used instead of time derivatives, thereby eliminating the flux angle from the equations. The analytical formulation using normalized quantities ensures that the control system is independent of the machine's parameters and rated capacity, which simplifies the coefficient tuning of two PI controllers. Thus, the proposed control method reduces the tuning time needed for the motor startup process. Simulation results of a 370-watt (W) three-phase SynRM demonstrate smooth operations and rapid dynamic responses using the proposed control scheme.