A double stage grid integrated pv system employing fixed frequency nonlinear controller with active power filter functionality

Abstract

At present situation, pollution free energy generation sources with user friendly environment has become one of the main challenges for researchers and engineers. Photovoltaic (PV) power systems for stand alone and grid connected modes of operation are increased attention in today electricity generation with reduced emissions when compared to all other pollution free energy sources. Recently among the various types of Distribution Generation (DG) system, double-stage grid integrated PV system becomes more popular because of its own MPPT capabilities, cost reduction in end users, simplified system installation and fulfillment of voltage gain requirement. Even though PV systems have more advantages, it addresses poor conversion efficiency due to non-linear characteristic of solar cell. The output power of PV cells will change due to the variation in climatic conditions such as temperature and irradiations. Therefore for maximizing the PV array output power and to improve the efficiency of PV systems, a new conception called Maximum Power Point Tracking (MPPT) technique is derived. Various MPPT methods have been proposed for tracking the maximum available power even under poor atmospheric conditions. However in two-stage PV system, the dynamic interaction among the dc-dc converter, inverter and MPPT controller may decrease the system performances in terms of system efficiency and disturbance in voltage oriented MPPT techniques, e.g., Perturb and Observe (PandO) method. This is mainly due to PV voltage oscillations caused by the second harmonics frequency of the grid and nonlinear characteristics of PV cells. The most of the control algorithm implementation involves direct linear control techniques which do not ascertain stable operating region addresses poor static and dynamic performance under irradiation variations. Moreover, the nonlinear controllerbased on Sliding Mode Control (SMC) can provide a consistently good dynamic performance to nonlinear systems against uncertainties in load and environmental pertur