A robust sliding mode controller for a grid-connected photovoltaic source is proposed in this paper. The objective of the presented control scheme is to force both the output voltage of the photovoltaic PV source and the power factor at the inverter output to follow a certain trajectory reference. The main idea is to apply the robust sliding mode controller directly to the nonlinear state model of the system composed of the PV source and the inverter with its input and output filters. In order to operate the PV system at the maximum power point and to satisfy the environmental factors, such as solar irradiance and temperature, we included a rigorous maximum power point tracker based on an artificial neural network. Simulation results are presented to illustrate the performance of the proposed control scheme. In addition, we show that the grid current satisfies the harmonic limits of the IEEE standard for interconnecting distributed energy sources with electric power systems. KEYWORDS artificial neural network, grid connection, harmonic distortion, maximum power point tracker, photovoltaic source, sliding mode control 1 | INTRODUCTIONRenewable energy sources are candidates for future electric energy due to their independence from fossil and nuclear fuels and given their low impact on the environment. Nowadays, photovoltaic (PV) sources contribute more and more in the generation of electric energy around the world. Photovoltaic power generation converts the sun's irradiation directly into electrical energy. To avoid the problems common in autonomous systems, such as costly and bulky batteries that require regular maintenance, it is necessary to operate the PV system in gridconnected mode; this allows injecting energy excess and covering for demand where production is not sufficient [1].Currently, grid-connected PV systems are the subject of many research works. The most important points of study are: the maximum power point tracking (MPPT) of solar arrays [2][3][4][5], the control of reactive energy injected in the network using suitable control techniques [2,4,5] and the reduction of harmonic pollution of the network by means of appropriate power electronic converters [4,5]. Commonly, grid connected PV sources use two cascaded power electronic converters: a DC-DC converter allows the control of the maximum power point (MPP) of the PV source and a DC-AC converter allows the control of the output voltage and the power factor as well as the reduction of the harmonic pollution of the output current [1,2,6].In [7], a basic proportional-integral (PI) controller is used to investigate the performance of a grid connected PV system by means of two cascaded DC-DC and DC-AC converters. The use of powerful control techniques ---

No abstract

In this paper, a robust model-free controller for a grid-connected photovoltaic (PV) system is designed. The system consists of a PV generator connected to a three-phase grid by a DC/AC converter. The control objectives of the overall system are to extract maximum power from the PV source, to control reactive power exchange and to improve the quality of the current injected into the grid. The model-free control technique is based on the use of an ultra-local model instead of the dynamic model of the overall system. The local model is continuously updated based on a numerical differentiator using only the input–output behavior of the controlled system. The model-free controller consists of a classical feedback controller and a compensator for the effects of internal parameter changes and external disturbances. Simulation results illustrate the efficiency of the controller for grid-connected PV systems.