Mitigation of MPPT Generated Interharmonics in Grid Connected PV Systems by Modified P and O Algorithm

The high penetration of renewable energy systems like photovoltaic (PV)systems in the distribution network gives rise to several power quality issues. The causes and effects of interharmonics generated from PV side is addressed in recent literature and the perturbation of the Maximum Power Point Tracking (MPPT) algorithm is identified as the major cause for inducing interharmonics in the grid current. In this paper, the effect of perturbation step size of MPPT algorithm on different MPPT performance factors like tracking speed, efficiency and interharmonics is studied. Usually, a compromise is to be made between these factors while choosing step size. In this paper, P & O algorithm with two fixed step sizes, an adaptive step size P & O algorithm and a hybrid P & O algorithm is proposed to reduce interharmonics generated from MPPT. The algorithms are simulated in MATLAB and results are compared with conventional fixed step size P & O algorithm with small as well as big perturbation step size. Analysis of the results show that the Hybrid P and O MPPT method reduces interharmonics introduced by the MPPT operation without much compromising the other performance factors of the algorithm.