High-Torque Density and Voltage Overmodulation for Five-Phase Induction Motor Drives

The torque density of a multiphase motor can be increased without exceeding the admissible current of the drive if the high-order spatial harmonics of the magnetic field in the air gap are appropriately synchronized with the fundamental one. Notably, due to the converter voltage limitation, this method is feasible only if the speed of the rotor is below its base speed. As the speed of the rotor increases, the voltage must correspondingly increase to sustain the field harmonics in the air gap. Above the base speed, the prevalent strategy in motor control focuses on regulating only the fundamental component of the magnetic field in the air gap. Nevertheless, this paper presents a new method that employs the injection of voltage harmonics to extend the linear modulation range of the fundamental voltage vector, thereby improving motor performance. In the field weakening region, an increase in the magnitude of the stator voltage vector improves the motor power and torque by over 40%. Experimental tests on a five-phase induction motor drive confirm the feasibility and the effectiveness of the developed control scheme. Overall, this approach shows great potential for improving motor performance and has applications in various sectors of motor control.