A Robust Control of Two-Stage Grid-Tied PV Systems Employing Integral Sliding Mode Theory

Abstract

This contribution considers an improved control scheme for three-phase two-stage grid-tied photovoltaic (PV) power systems based on integral sliding mode control (ISMC) theory. The proposed control scheme consists of maximum power point tracking (MPPT), DC-Link voltage regulation and grid current synchronization. A modified voltage-oriented maximum power point tracking (VO-MPPT) method based on ISMC theory is proposed for design of an enhanced MPPT under irradiation changes. Moreover, a novel DC-Link voltage controller based on ISMC theory is proposed to achieve good regulation of DC-Link voltage over its reference. To inject the generated PV power into the grid with high quality, a voltage-oriented control based on space vector modulation (SVM) and ISMC (VOC-ISMC-SVM) has been developed to control the grid current synchronization. Numerical simulations are performed in a MATLAB/SimulinkTM (R2009b, MathWorks, Natick, MA, USA) environment to evaluate the proposed control strategy. In comparison with conventional control schemes, the developed control strategy provides an accurate maximum power point (MPP) tracking with less power oscillation as well as a fast and an accurate DC-Link regulation under varying irradiation conditions. Moreover, the transfer of the extracted power into the grid is achieved with high quality.

Keywords

• grid-tied photovoltaic system
• maximum power point tracking (MPPT)
• voltage-oriented control (VOC)
• integral sliding mode control (ISMC)theory
• DC-Link control