A torque improving stationary frame controller for permanent magnet synchronous machines: Feedback linearizing decoupling control

Permanent magnet synchronous motors are often used in a self-commutated mode of operation. This may be accomplished through the use of a resolver or other means of position feedback. In most cases, the phase angle of the applied voltage is configured to be 90° out of phase with the rotor permanent magnet flux (the optimal torque angle) for all operating conditions. However, the current flowing in the motor windings will lag the applied voltage due to inductive and nonlinear effects. To resolve this problem, many manufacturers have developed control circuitry which, in the past, has been rather complex. This paper describes an inexpensive, easily implementable, stationary frame, nonlinear control circuit applicable to permanent magnet synchronous motors. This control was derived using rotating frame theory. The proposed theory is supported by experimental results