MPPT techniques applied to the control of a module-integrated inverter grid-connected based on Zeta converter for PV panels

Abstract

This paper presents the study and implementation of maximum power point tracking techniques (MPPT) applied to a module-integrated inverter based on a Zeta converter. The module-integrated inverter allows electricity generated by a PV solar panel to be injected into the commercial power grid. This structure provides significant advantages over the structure that employs the combination of multiple panels connected to a large single inverter (central inverter). Among the advantages offered by the module-integrated structure can be highlighted: modularity, allowing the natural parallelism of the systems, increased system reliability, because in case of failure of a module the plant remains powered after all energy is provided by several PV panels and their module-integrated inverters that work independently, and finally, there is the possibility of obtaining the MPPT individually, which is quite interesting in large systems, where shading may occur in only a few panels. The system employed in this work consists in the association of a PV array to a Zeta converter in cascaded with a single phase full-bridge inverter operating synchronized with the power grid at the same frequency. A Zeta converter working in DCM is responsible for the synthesis of a rectified sinusoidal current waveform synchronized with the grid. The CSI is used to invert the current every 180°. In this study three MPPT techniques were examined, namely Constant Voltage, Perturb and Observe and Hill Climbing. A prototype was built using digital signal processing. The obtained results validated the presented study, described in the work.