AC Grid Connected Photovoltaic Systems—A review

This paper focuses on the control of grid-connected photovoltaic arrays, which are required to provide the maximum of power irrespective of the solar irradiance conditions. The energy provided by the arrays is sent to the single-phased utility grid by means of a two-stage conversion system, composed of a DC-DC boost converter and a DC-AC inverter. The whole system is controlled through a two-level structure: the upper layer establishes the global scope, i.e., the desired operating regime, which is effectively implemented by the low control layer, i.e., by low-level controlling the two power electronics converters. Thus, the operating regime of the PV arrays is imposed by controlling the DC-DC converter, whereas the inverter is in charge with ensuring the power transfer to the grid. In this case, the global scope of tracking the maximum power point under variable conditions of irradiance is achieved by using a simple and robust extreme seeking control scheme. MATLAB/Simulink numerical simulations are presented and discussed in order to prove the effectiveness of the approach.