Performance Evaluation of Modified 5-Level T-Type H-Bridge Inverter Utilizing Different PWM Modulation Schemes

In this paper comparative study of a recently proposed 5-Level T-Type Asymmetrical-H-Bridge (5-L-T-AHB) inverter is carried out for different modulation schemes based on PWM switching. The THD and the fundamental component of the output voltage for different modulation schemes at different frequencies is recorded and compared. The main advantage of high frequency PWM switching is that it reduces the THD in output current and voltages of a multi-level inverter. Matlab/Simulink is used for the simulation purpose. The results show that the variable frequency Phase-Opposite-Disposition PWM (PODPWM) modulation scheme based on triangular carrier wave have the minimum THD of 20.06% in voltage at unity modulation index. While the Third-Harmonic-Injected (THI) reference based PWM shows the highest THD of 25.97%. THI based PWM however, offers the highest fundamental component with 12% more output. Variation of THD and fundamental component is also seen for the varying modulation index (0.6-0.9). THD shows the decreasing trend while the fundamental component increases with increment in modulation index.