Optimal Control of Induction Motor in Field Weakening Region Considering Inverter Nonlinearity

Optimal control of induction motors in the field weakening region considering measured inverter voltage drop with low current nonlinearities is presented in this paper. The low current nonlinearity on the threshold voltage is usually neglected in generating optimal control references of electric machines. In this paper, nonlinear voltage drops of the inverter at both low and high current regions are measured and formed a look-up table. This lookup table in abc frame is transformed to dq frame and incorporated in optimal control algorithm of the induction motor to illustrate the effects on the voltage curves, torque-speed characteristic and operating point trajectory, especially in the field weakening region. The effectiveness of considering inverter nonlinear voltage drop on operating point trajectory of induction machine is verified with both simulations and experimental results.