FPGA Realization of Trapezoidal PWM for Generalized Frequency Converter

Combining concept of cyclo-converter and cyclo-inverter, a generalized frequency converter has been developed where undesirable harmonic components are minimized using nonsinusoidal carrier-based PWM, which is a trapezoidal pulsewidth modulation technique. The study begins by establishing a model of frequency converter to obtain the firing sequence for cyclo-converter and cyclo-inverter mode of operation. The converter is simulated using the well-known software Matlab and simulations results are presented for a single-phase ac supply. It has been found that, for cyclo-inverter operation, the minimum total harmonic distortion in the output voltage is found to be 4.8%, while during cyclo-converter operation it is only 2%. Simulation results are validated with the experimental results. A prototype of frequency converter is developed where a field-programmable gate array is used to generate the PWM trigger signal through Xilinx 9.2i. The results are also compared with other existing carrier-based modulation techniques.