Current Mode Control of a Solar Inverter with MPPT Algorithm

In the last decade, grid-connected photovoltaic systems were studied and developed due to advance in the technology of solar panels, their price drop and the climatic crisis. This work will study, analyze and design a low power solar inverter. The most important design constraints for a solar inverter are: efficiency, maximum power point tracking (MPPT) performance and synchronization with the utility grid. The objective of this project is to find a solution for each (minimization of power losses, precise tracking of grid frequency). To achieve a satisfying efficiency, a current mode control loop in a two-dimensional control frame was implemented, with an enhanced phase-lock loop (EPLL) as the synchronization mechanism with the utility grid. For tracking the maximum point on the power curve of the solar cell, a classical hill climbing method was improved and integrated into the system. For simulations, Matlab Simulink software was used and input power versus output power was examined along with total harmonic distortion (THD) of the inverter's output current, while for experimental testing a dSPACE controller board and two Suntec Power solar panel. The paper is focused on the current mode control loop mathematical equations providing a simplified step by step design process.