Harmonic performance evaluation of multicarrier PWM in a three-level three-switch PV microinverter

This paper presents a comparative performance evaluation of level-shifted pulse-width modulation (PWM) techniques applied to a three-level T-type photovoltaic (PV) inverter configured as a single-stage microinverter. Unlike conventional microinverter topologies that typically require a greater number of power semiconductor switches or an external output filter, the proposed configuration employs a reduced-switch three-level architecture intended for low-voltage self-consumption (SELCO) applications. The topology was modelled and evaluated in MATLAB/Simulink under Standard Test Conditions of 1000 W/m² solar irradiance and a cell temperature of 25 °C. A single PV module configuration (Np = 1, Ns = 1) provides a 48 Vdc input suitable for residential applications. The primary contribution of this work lies in the application and comparative evaluation of level-shifted PWM strategies within a reduced-switch three-level microinverter topology. Three level-shifted PWM strategies, namely Phase Disposition (PD-PWM), Phase Opposition Disposition (POD-PWM), and Alternative Phase Opposition Disposition (APOD-PWM), are implemented and benchmarked against a conventional Pulse Generator modulation strategy. The output-voltage and output-current harmonic characteristics were evaluated using fast Fourier transform analysis. The simulation results demonstrate that PD-PWM achieves the lowest current total harmonic distortion, reducing the THDi from 16.36% with the conventional PG method to 2.16%, corresponding to an 86.8% reduction. These findings demonstrate that appropriate multicarrier PWM selection can substantially improve the simulated current harmonic performance of the reduced-switch three-level T-type microinverter while preserving its compact circuit configuration.