Minimizing the Current of Permanent Magnet Synchronous Motors with a Vector Control System

Permanent magnet synchronous motors (PMSM) are a promising choice for use in transport and various industries. It has been found that PMSM with magnetic asymmetry have a number of advantages in comparison with motors with magnetic symmetry. The aim of the article is to minimize the stator winding current of a PMSM with a vector control system. Based on the methods of electric drive theory, an equivalent circuit of PMSM with magnetic asymmetry in the dq coordinate system was compiled, on the basis of which the motor mathematical model was developed. The model takes into account nonlinear effects associated with the stator magnetic circuit saturation, power loss in the stator magnetic circuit, and the effect of temperature on the equivalent circuit parameters. For a vector control system with orientation by the PMSM stator flux linkage, an extreme dependence of the stator winding current on its projection on the d axis was obtained. A formula for setting the stator winding current projection on the d axis, which ensures the minimum value of the stator winding current in the constant torque zone, has been derived analytically. Based on the methods of automatic control theory, an algorithm and a system for searching the minimum value of the stator winding current in the constant torque zone have been developed, which is insensitive to changes in the equivalent circuit parameters. The stator winding current projection on the d axis is used in the search system as the control output. The operability of the developed control system has been confirmed by computer simulation of an electric drive with a 132 kW PMSM. Conclusions have been drawn on the use of these systems in various electric drives.