Dynamic Simulation and Harmonic Evaluation of a Hybrid Multilevel Inverter for Photovoltaic Systems Using Pulse Width Modulation Strategies

The current work proposes a novel design of Cascaded H-bridge (CHB) and half-bridge for an asymmetric hybrid Multi-Level Inverter (MLI) to generate a nine-level output using a reduced number of power switches. By utilizing three unequal DC voltage sources, the proposed topology achieves an extended range of nine-level output voltages while maintaining a simplified and compact architecture. A comprehensive evaluation of the proposed asymmetric MLI was conducted, namely, the cost function, component count per level, and total standing voltage. The output performance of the proposed MLI was evaluated using three carrier-based Pulse Width Modulation (PWM) techniques: Phase Disposition (PD), Phase Opposition Disposition (POD), and Alternate Phase Opposition Disposition (APOD), and by simulating in MATLAB Simulink a Photovoltaic (PV) system under variable irradiance. The simulation results revealed that the PD technique demonstrated superior performance in achieving the lowest Total Harmonic Distortion (THD) of 13.98% at a modulation index of 0.95. A comparative analysis was performed with other existing topologies. The proposed topology achieved a Total Standing Voltage per unit (TSVPU) of 18 VDC and cost function values of 4.75 and 6.25, while the total component count per level was calculated as 1.67, which is comparatively lower than that of the existing topologies. In conclusion, the reduction of the switch count significantly decreases the switching losses, system complexity, and installation costs compared to traditional MLI configurations.