The solar cell characteristics are non-linear and largely influenced by solar radiation, temperature and load condition. The power output of a PV array changes with varying temperature and irradiation. A maximum power point algorithm is investigated to obtain maximum power from a PV array on varying operating conditions. So far various methods have been proposed to achieve the maximum power from PV module. The incremental conductance (INC) and perturb and observe (P&O) algorithm are more noteworthy. In this paper two high performance and simple maximum power point tracker (MPPT) are proposed. These algorithms are modified P&O and INC algorithms. These modified algorithms are capable to track maximum power under rapidly changing atmospheric conditions with higher accuracy than their conventional methods. They increase the harvested power from PV array and thus improve the efficiency of MPPT algorithm. The algorithms using a high step-up-DC/DC converter are implemented on MATLAB/SIMULINK tool. The results demonstrate a good performance and accurate tracking under rapidly changing atmospheric conditions