Keywords: harmonics, multilevel inverters, SVPWM, PWM generation, pulse width modulation, hexagonal voltage space vector generation, dodecagonal voltage space vector generation, induction motor drives, power circuits, simulation
Multilevel voltage space vector generation with hexagonal and dodecagonal voltage space vectors for induction motor drives
The proposed power circuit that can perform multilevel inverter operation consists of three cascaded two level inverters with asymmetric DC link voltages and results in hexagonal voltage space vector structure in lower modulation region and a 12–sided polygonal space vector structure in the higher modulation region. The proposed topology reduces torque pulsations and losses due to the complete elimination of the 5th and 7th harmonic voltages. In the lower modulation region, inner space vectors may be switched, and in higher modulation region the 12–sided polygonal space vectors and hexagonal voltage space vectors are used for the PWM generation. FFT analysis is proposed to verify the reduction in harmonics in the output wave form. A detailed simulation study using Simulink is presented in this paper. The first part of the study uses a dodecagonal space vector structure for the PWM generation. The computer simulation result is experimentally verified using resistive load.