This work presents an improved perturb and observe with adaptive perturbation size (IAP&O) algorithm for harnessing maximum power from a double stage solar photovoltaic (PV) energy conversion system (SPVECS) interfaced to a three phase distribution grid. Among various MPPT (Maximum Power Point Technique) techniques, the P&O method is most popular technique in industrial and domestic applications because of its simplicity. However, its performance is affected from drift problem and it is increased in quick changes of environmental conditions. In this double stage SPVECS, a VSI (Voltage Source Inverter) to a three phase distribution grid is deployed. To ensure the quality of power as per an IEEE-519 std. on harmonics, it has maintained the power quality norms in three phase distribution feeder network. Therefore, to feed the real power to the three phase distribution network and to maintain the sinusoidal grid currents, this system performs well. The Matlab/Simulink is utilized for simulation purpose and the performance of proposed system is examined in different environmental situations on an experimental prototype, which is established in the laboratory. AN IMPROVED ADAPTIVE P&O TECHNIQUE FOR TWO STAGE GRID INTERFACED SPVECS