Energy Method for Torque Control of a Synchronous Traction Motor

The problem of increasing the accuracy of determining the torque and the load angle of the permanent magnet synchronous motor of an electric traction drive to the predicted level (2.5...3)% of the full-scale error is solved by an indirect method. We considered the algorithms for calculating the generalized current and voltage of the electric motor, the total power, the instantaneous values of the power factor, and the sine of the phase angle between the first harmonics of voltages and currents. We determined the requirements for the accuracy of determining these values at the level of 1% of the full-scale error. We considered the algorithms for determining the total instantaneous power losses by the indirect method at the predicted level (15...20)% of the full-scale error with the efficiency of the motor (90...95)%. The obtained results are integrated into the energy model of the electric motor as differential equations of the instantaneous active and reactive power balance of the electromagnetic system and the single-mass mechanical load. The equation of active power balance underlies the algorithms for controlling the torque and the voltage amplitude of the motor. Basing on the reactive power balance equation, we formed the algorithm for monitoring the inductances of the electrical machine stator. The obtained algorithms are adapted to the mode of power-efficient control of the motor by the criterion of the zero-equal phase angle between the first harmonics of voltage and current and to the mode of the zero-equal phase angle between the electromotive force and the stator current. We considered the problems of adapting the algorithm for controlling the voltage amplitude to the mode of power limitation of the permanent magnet synchronous motor at the nominal level. The work contains the results of modeling the control modes of the real traction motor.