Maximum power point tracking for single stage grid-connected PV system under partial shading conditions

Photovoltaic (PV) panels are subject to partial shading in many practical situations due to nearby obstacles like trees, buildings and the adjacent PV panels. Multiple peaks can exist on the resulting power-voltage (P-V) characteristics of the PV panel under partial shading conditions. This may disturb the efficient maximum power point tracking (MPPT) operation as many existing MPPT methods can converge to local peaks. In this paper, effects of different shading conditions on the characteristics of the PV panel have been investigated. Based on the results and observations, a simple MPPT technique is proposed to circumvent the trappings into the local peaks. The proposed method is based on several critical observations under common shading conditions. The proposed method uses variable step approach which considerably reduces the time to track the global peak. Effectiveness of the proposed method has been verified by computer simulations and experimental results.