A SOGI-Q based control algorithm for multifunctional grid connected SECS

Abstract

This paper deals with a three phase multifunctional grid connected SECS (Solar Energy Conversion system). A two stage power circuit topology is used in this work, in which the first stage is a boost converter, which serves the purpose of MPPT (Maximum Power Point Tracking) and the second stage is a 4-leg VSC (Voltage Source Converter) which serves the purpose of feeding extracted energy along with power quality improvement in the distribution system. The SECS not only feeds solar PV (Photo-Voltaic) energy into the grid but also serves purpose of grid currents balancing, reactive power compensation, harmonics elimination and neutral current mitigation. A feed-forward term for the solar contribution is used to improve the dynamic response for climatic changes. The PV array voltage is continuously adjusted with the help of boost converter to achieve MPPT whereas the DC link voltage of VSC is kept constant with the help of a PI (Proportional-Integral) controller. A SOGI-Q (Second Order Generalized Integrator - Quadrature) based algorithm is proposed for control of four-leg VSC. The system is modeled and simulated on MATLAB based platform. A wide range of simulation results are shown to demonstrate all features of proposed system. The simulation results show the feasibility of the proposed control algorithm. The THD (Total Harmonics Distortion) of grid current has been found well under IEEE-519 standard.