Adaptive control scheme for maximum power point tracking of a photovoltaic system connected to the grid.

An adaptive control scheme for maximum power point tracking of a single-phase single-stage photovoltaic system connected to the grid is presented. The maximum power point depends on temperature and solar irradiance, ambient conditions that are time-varying and difficult to measure. Two solutions are presented. Each solution derive an estimator that approximate three different parameters. These parameters are functions of solar irradiance and temperature. In this manner, we eliminate the necessity of climatic sensors. The first solution, uses an adaptive estimator that is able to estimate constant parameters, and the second one uses a sliding mode estimator that is capable of estimate time-varying parameters. A complete analysis was done taking into account the nonlinearities showed by the closed-loop system. The Lyapunov redesign technique was used to derive a controller that gives globally asymptotically stable trajectories of the closed-loop system. Computer simulations are presented to compare the performance of both estimators and also to show the good performance of the controller.