Comparative Study of Sinusoidal PWM Strategies in Cascaded Multilevel Inverters

This paper presents a comparative study of four Sinusoidal Pulse Width Modulation (SPWM) strategies Phase Disposition (PD-PWM), Phase Opposition Disposition (POD-PWM), Alternate Phase Opposition Disposition (APOD-PWM), and a Modified SPWM applied to Cascaded H-Bridge Multilevel Inverter (CHMI) systems. MATLAB/Simulink is used to simulate both 5-level and 11-level CHMI configurations, focusing on output voltage quality and total harmonic distortion (THD) as performance metrics. The analysis is conducted by varying two key control parameters: modulation index (0.5 to 1.0) and switching frequency (5 kHz, 10 kHz, 20 kHz). The results show that increasing voltage levels is the most effective way to improve waveform quality, while modulation strategy plays a minor role. POD and APOD offer slight THD advantages, and Modified SPWM performs almost identically to PD-PWM, making it a simpler alternative for practical CHMI applications. The findings provide a practical guideline for selecting appropriate SPWM strategies in high-performance inverter applications such as electric vehicles, industrial drives, and renewable energy systems.