Application of Flexible OMTHD Technique to Cascaded Multi-level Inverter and the FPGA Based Implementation of Control System

Atmospheric Science Department, University of Nevada-Reno, Reno, Nevada. ---------------------------------------------------------------------***--------------------------------------------------------------------Abstract Generating controllable output voltage is a key factor in designing the motor speed control techniques. Providing desirable output voltage with less Total Harmonic Distortion (THD) is also necessary while utilizing renewable energy sources, configured to produce low voltage output. In this paper, a multi-objective optimization problem is performed to minimize THDs corresponding to desired output fundamental voltages simultaneously, while the output fundamental voltage is exactly produced as the required value. Both multi-objective genetic algorithm and a multi-objective approach to the Stochastic Fractal Search algorithm is utilized in two case studies. First, a common set of switching angles for a wide range of output fundamental voltages would be defined. Second, different sets of switching angles corresponding to low, medium and high values of output fundamental voltage would be determined. The results are compared to those obtained from THD minimization for the range of 0-1 P.U. as the benchmark. The results show better THD for the first case, similar to the benchmark. The experimental results are demonstrated on one phase seven and eleven-level inverter controlled by Xilinx SPARTAN3 FPGA (XC3S400-PQG208).