Comparative evaluation of modulation strategies for a single-phase PV micro-inverter with high-frequency transformer

摘要

Micro-inverter topologies have several advantages for grid-connected photovoltaic (PV) power generation systems, such as: flexible system design, simplified installation and enhanced safety characteristics. In this paper, a single-phase micro-inverter with a high-frequency transformer is introduced. The micro-inverter is composed by: an isolated high-frequency full bridge dc-dc converter, an inverter and LCL filter. Performance evaluation of the converter using three modulation strategies are analyzed by comparing harmonic distortion of injected current and semiconductor losses. The aforementioned modulation strategies (MS) are: phase-shift with unipolar PWM (MS1), phase-shift with hybrid PWM (MS2), and sinusoidal phase-shift with unfolding stage (MS3). Simulation results using PSIM corroborate the feasibility of the micro-inverter adopting different modulation strategies, being MS2 more equilibrated between semiconductor losses and injected current THD. Finally, a 250 W prototype was manufactured to validate the performance of the micro-inverter.