8-Shaped trajectory control for rugged rural PV inverters

This paper presents the derivation and analysis of a high-performance control scheme referred to as 8-Shaped Trajectory Control (8-STC) applied to grid-tie inverters for photovoltaic (PV) applications. The characteristic low-frequency variations in the dc-link of these systems (100Hz/120Hz and harmonics) present a challenge to traditional controllers. The study of the behavior of the converter is performed in a normalized geometrical domain that provides generality to the analysis. The target operating trajectory described by the varying references is also characterized. The insight gained from the previous study creates the foundation for the proposed control strategy, being constant switching frequency a remarkable feature of it. Simulations and experimental results of a 1kW grid-tie inverter are presented to verify the enhanced properties of the 8-STC scheme, providing low-THD current injected into the grid.