Enhancing Efficiency and Robustness of a Photovoltaic Power System under Partial Shading

Yanzhi Wang1,  Xue Lin1,  Younghyun Kim2,  Naehyuck Chang2,  Massoud Pedram1
1University of Southern California, 2Seoul National University


Photovoltaic power systems have been widely applied in commercial and domestic facilities, and electrical energy storage systems are mandatory in standalone PV systems for continuous power supply. In this paper we address efficiency and robustness enhancement methods under partial shading. Partial shading due to moving clouds and shadows of nearby obstacles on a PV array causes significant efficiency degradation, since shaded and non-shaded PV modules have large discrepancy in their maximum power points. Use of Individual charger for each PV module may mitigate the negative effect from partial shading. However, this method alone may still face severe energy efficiency degradation caused by 1) the energy loss due to parasitic effects in the EES elements and 2) the energy loss in the chargers. This paper proposes three methods to enhance the PV system efficiency and robustness under partial shading: 1) incorporation of a HEES (hybrid electrical energy storage) system into the PV system, 2) extension of the MPTT (maximum power transfer tracking) approach, and 3) dynamic PV module reconfiguration. The three methods can be effectively combined together, thereby yielding a significant efficiency gain ranging from 17.1% to 53.3% compared with the baseline systems.