Architecture and Control Algorithms for Combating Partial Shading in Photovoltaic Systems

Abstract

Partial shading is a serious obstacle to the effective utilization of photovoltaic (PV) systems since it can result in a significant degradation in the PV system output power. A PV system is organized as a series connection of PV modules, each module comprising a number of series-parallel connected PV cells. Backup PV cell employment and PV module reconfiguration techniques have been proposed to improve the performance of the PV system under the partial shading effects. However, these approaches are not very effective since they are costly in terms of their PV cell count and/or cell connectivity requirements. In contrast, this paper presents a cost-effective, reconfigurable PV module architecture with integrated switches in each PV cell. This paper also presents a dynamic programming algorithm to adaptively produce near-optimal reconfigurations of each PV module so as to maximize the PV system output power under any partial shading pattern. We implement a working prototype of reconfigurable PV module with 16 PV cells and confirm 45.2% output power level improvement. Using accurate PV cell models extracted from prototype measurement, we have demonstrated up to a factor of 2.36X output power improvement of a large-scale PV system comprised of three PV modules with 60 PV cells per module.