Variable Step Perturb and Observe Algorithm for Standalone Solar Photovoltaic (PV) System

To extract the maximum power from available solar energy, the Maximum Power Point Tracking (MPPT) technique is used in solar photovoltaic system. Due to its simplicity and ease of implementation, the Perturb and Observe (P and O) technique is a commonly used approach to track the maximum power point (MPP). However, P and O algorithm oscillates near MPP point and give slow dynamic response. This paper presents a modified P and O method with a variable step size. This modified method is an effort towards overcoming the two major limitations of the conventional P and O method, first is oscillations near MPP and the second is loss of a tracking of MPP point during sudden change in irradiance. Here, the change in the step size is different according to the region of voltage, which will be decided by the difference between a voltage of the current operating point and MPP at desired irradiance. The proposed P and O gives good tracking accuracy in dynamic conditions and very less oscillations near the MPP as accepted. Detailed simulation analysis is done considering various steady-state and dynamic irradiance conditions for both the conventional and modified P and O methods and detail comparative result analysis is presented to validate the effectiveness of proposed algorithm. Proposed method improves the power quality and increase the efficiency of power conversion. Real time implementation is also easy.