Design and implementation of Nineteen level three-phase inverter for constant torque three phase induction motor

Multilevel inverters (MLI) have a wide range of applications in industry due to their efficiency. In this work, a three-phase inverter with 19 levels of phase voltages and 33 levels line voltages was designed and implemented to control the speed of a three-phase induction motor for constant torque operation using a V/F approach. The Gray Wolf Optimization (GWO) algorithm is adopted as the brain of the 3E Spartan FPGA Kit to gate the 36 MOSFETs power switches in the inverter circuit. For different reference speeds, the results are shown in the form of the output voltages, currents, speeds and torques. The torques are shown to be constant for all reference speeds when the three-phase induction motor is subjected to the external load torque. Results in the form of frequency spectrum and results show significantly reduce in the THD compared with traditional sinusoidal pulse width modulation SPWM. The three-phase MLI can be easily extended to more than 19 phase voltage with a slight modification in the inverter circuit.