Design of Current Control Loop for Permanent Magnet Synchronous Servo System

Abstract

The principle of the vector control for permanent magnet synchronous motor (PMSM) is presented. Various factors that affect the vector control current loop of PMSM are analyzed, including the zero drift of all parts of the current loop and electro motive force (EMF) of the motor to constitute high performance current loop for the servo system. The zero drift in current loop influences the adjusting capability of the current regulator, and affect the smooth movement of the motor operated in low-speed range. Because the EMF is in proportion to the rotation speed of the motor, the net voltage of the motor winding, imposed by the inventor, decreases with speed risen, thus weaken the tracking ability as well as its dynamic performance of the current loop in high speed range. In this paper, the parameters of current regulators are revised, jointly with the adaptations of differential regulation and over modulation in PWM modulators, to improve the dynamic response performance. With the help of over modulation, the direct voltage using rate can be enhanced and the interference of EMF be restrained in high-speed range. Both experimental and simulation results show that the adopted measures are valid, the system can be assuringly stabilized, and the dynamic performance of the system is effectively improved, which provide a basis for realizing high performance permanent magnet synchronous servo system.