Modified variable step size affine algorithm for grid integrated PV system

Abstract

This paper proposes a Modified Variable Step Size Affine (MVSA) algorithm for a single stage grid integrated photovoltaic (GIPV) system. Integration of photovoltaic (PV) system to utility grid encounters many control issues like nonlinearities, disturbances and unbalanced loading. The proposed algorithm not only improves the overall performance of the system despite all the adverse conditions but also improves the power quality as per IEEE-519 standard. The proposed algorithm is developed to eliminate harmonics caused by nonlinear loads, to transfer active power from PV source to load as well as to grid under unity power factor condition, to maintain constant voltage profile at the point of common coupling and to provide a controlled reference signal to the hysteresis controller so as to produce suitable gate pulse to voltage source converter (VSC). In this paper, a PI control is used to maintain dc link voltage and P&O method is used to extract optimum power from PV source irrespective of all disturbances in the utility grid. The system under consideration is modelled and simulated using MATLAB/Simulink software. Comparing the performances of the said variable step size control algorithm with that of fixed step size algorithm like Fixed Step Size Affine (FSA) Projection Algorithm and Least Mean Fourth (LMF), it is observed that the mean square error in MVSA is less as compared to FSA and LMF.