Steady-state performance analysis for optimal operation determination of doubly fed induction motors

Doubly fed induction machines (DFIMs) are less commonly used as motors in the industry. DFIMs are more commonly designed as doubly fed induction generators (DFIGs) and used as variable speed generators in wind turbines. In this paper, a large-scale DFIM is studied in steady-state operation. In this study, using the steady-state models and equivalent circuits, a comprehensive analysis of the DFIM performance in motor operation mode is performed. Using the simulation results, the behaviour of the motor in all three synchronous, super-synchronous, and sub-synchronous modes is analyzed and evaluated in detail. Adjusting and controlling the rotor voltage in DFIMs is very essential. Therefore, a simple method for optimally adjusting the amplitude and angle of the rotor voltage in steady state is proposed for three different optimization scenarios that maximize output power, efficiency, and power factor, respectively. The results show that by properly determining the rotor voltage, the DFIM can perform optimally in a wide range of speed variations.