Adaptive Modulation and Harmonic Mitigation in Grid-Connected CHB PV Inverters

The power flow control strategies of three-phase multilevel Cascaded H-Bridge (CHB) inverters used in grid-connected photovoltaic (PV) systems are compared in this paper. Analyzing and improving the modulation performance under different irradiance conditions—such as uniform, partial shading, and dynamic variations—is the goal. Based on their modulation index and the resulting Total Harmonic Distortion (THD) of the grid current, three modulation techniques are evaluated: Fundamental Voltage Reconstruction (FVR), Third Harmonic Injection (THI), and Hybrid PWM (HPWM). According to simulation results conducted in MATLAB/Simulink, FVR pro-vides a straightforward design; however, under non-uniform irradiance, its performance drastically deteriorates. THI uses moderate complexity to achieve better harmonic suppression. HPWM exhibits exceptional robustness and dynamic adaptability, consistently delivering the lowest THD in all cases. The results back up the application of sophisticated modulation techniques, such as HPWM, for improved power quality and grid standard compliance in practical PV systems.