A Modified Perturb and Observe Maximum Power Point Tracking Technique for Single-Stage Grid-Connected Photovoltaic Inverter

There is an inherent tracking-oscillations trade-off problem in Perturb and Observe (P&O) maximum power point tracking (MPPT) technique for photovoltaic (PV) system. Higher perturbation step-size increases the tracking speed at the cost of greater oscillations around maximum power point (MPP); whereas, smaller step-size slows down the tracking while reducing the oscillations around MPP. In this paper, a modification in P&O method is proposed to reduce this tracking-oscillations trade-off problem by setting an initial approximate perturbation value whenever irradiance changes and continuing tracking with adaptive stepsize. Detail simulation results of the modified P&O method are presented and compared with the results obtained considering different values of fixed step sizes. The P&O method with the proposed modifications clearly shows maximum tracking speed with minimum oscillations around MPP. Moreover, due to the modifications, the algorithm can track MPP efficiently in case of sudden irradiance change. Key-Words: -Photovoltaic (PV), Perturb and Observe (P&O), Maximum Power Point Tracking (MPPT), Gridconnected PV, Inverter, Modulation Index, Phase Angle.