Interior point method based efficiency optimization for an induction motor drive

In the last decades efficiency improvement in induction motor drives (IMD) has been an important key against environmental pollution due to they are widely used in industry and transport facilities. This paper shows efficiency optimization of IMD using interior point method (IPM) and direct vector control (DVC) in order to adjust rotor flux, magnetizing current and torque current magnitudes. Therefore efficiency is the objective function to be maximized which consists of the mechanical power (output power) and the input power (output power plus losses). The losses which are taken into account are: switching and conduction losses, in the inverter and stator copper, rotor copper, core, windage and stray losses of the induction motor; all of them in function of slip. At steady state the IPM looks for an slip which minimizes the losses or maximizes the efficiency, once the slip is known, the rotor flux is calculated and given as a reference of the PI flux regulator in the vector control. The parameters which are given to the IPM are the estimated torque and reference mechanical speed. Finally, the efficiency optimization has been simulated in Python and the vector control system with optimum rotor flux has been simulated in Matlab Simulink®.