Identification of Partial Shading Conditions for Photovoltaic Strings

Abstract

Under partial shading conditions (PSC), the power-voltage (P-V) characteristic curve of photovoltaic (PV) strings exhibits multiple peaks. Such mismatching phenomenon brings challenges in controlling the output power. To analyze the electrical characteristics of PV strings in complex environments, a quantitative analysis method is required to characterize the PSC. This paper introduces the shading matrix to describe the shading rate and shading strength information. The proposed shading matrix would provide maximum power point tracking (MPPT) controllers with the essential environmental information to improve the global maximum power point (GMPP) tracking performance. A modified Tabu search (MTS) based identification method is proposed to estimate the shading matrix. The proposed modified method involves a preselection process of updating the Tabu list to optimize the searching efficiency. The accuracy and efficiency of the proposed analytical estimation expression are validated through simulations and experiments. By comparing with binary search (BS), golden-section search (GS) and Tabu search (TS) algorithms, the proposed MTS algorithm is demonstrated to perceive the shading information at least 18.75% faster.