Comparative assessment of PWM strategies for three phase trinary source nine level inverter with rectified sine carriers [articol]

Abstract

This paper presents the performance assessment of various bipolar rectified sine Multi-Carrier Pulse Width Modulation (MCPWM) strategies with Trapezoidal reference for three phase Nine level cascaded Trinary Source multilevel inverter (TSMLI). TSMLI have been developed using MATLAB-SIMULINK and tested for different modulation indices 0.8-1 and real time implementation for same modulation strategies have been carried out using Field-Programmable Gate Array (FPGA) and results are presented and analyzed. The most popular cascaded multilevel inverter exhibits several other attractive features such as simple circuit layout, less component counts and modular structure which prevents unbalance in capacitor voltage. Two unequal Direct Current (DC) sources in the ratio 1:3 with twenty four switches are used in the chosen three phase trinary source multilevel inverter which produces nine voltage levels at the output whereas the conventional symmetric three phase nine level inverter uses 48 switches. Performance factors such as Percentage Total Harmonic Distortion (%THD), Voltage Root Mean Square (VRMS) where measured and harmonic spectra Percentage Distortion Factor (%DF) of output voltage are calculated for above different modulation indices. The results are compared both virtually and experimentally which reveals that Phase Disposition Pulse Width Modulation (PDPWM) strategies provides low THD and less Distortion Factor (DF) whereas Carrier Overlapping Pulse Width Modulation (COPWM) strategy is found to perform better since it provides relatively higher fundamental VRMS output voltage.