Generation of 42-sided polygonal Voltage Space Vector Structure for suppression of lower order harmonics in IM Drive Applications

The work proposes a new power circuit topology to generate a 42-sided polygonal space vector structure for filtering out the lower order harmonics up to 39th order from motor phase voltage through out the modulation range. In the proposed scheme, the open stator winding of the induction motor is fed with a primary inverter from one end and a secondary inverter from the other end. The primary inverter is fed with a single DC source for suppling the active power for the drive operation. The secondary inverter works as the switched capacitive filter to eliminate the lower order harmonics generated by the primary inverter. The machine phase voltage is devoid of all the lower order harmonics (5th, 7th,....39th) which results in smoother torque profile for motor operation. The proposed scheme also extends the linear modulation range till 99.82%. A unique pulse width modulation technique is used to reduce switching transitions in the primary inverter, causing lower switching losses in the proposed inverter scheme. Also, the proposed scheme is studied extinsively with MATLAB simulation and validated with hardware results.