Reconnection patterns of photovoltaic cells to reduce power loss due to detrimental conditions

Abstract

Defective or under illuminated photovoltaic (PV) cells on an array affect the performanceof the whole panel. In this work, the best connection design among cells is investigated for various shading situations. It is assumed that the photo-voltaic module enables internal disconnection and reconnection of neighboring cells. A methodology was developed to search the connection pattern that yields less power loss, assisted by an algorithm that takes into account the cell model and the effect of the degrading factors, e.g. shading, to manage the reconfiguration of the cells on the array. Three simulation sets were developed to mimic possible shading schemes in a 36 series-parallel-connected panel. For each case, the algorithm analyzed the IV-characteristics of the panel and suggested the best cell-connection pattern to achieve the highest power output under the current conditions. When less than 15 of the 36 PV cells were affected by shading, the algorithm was able to reduce the power loss due to shading by up to 30% when compared to the standard configuration and by up to 20% when compared to complex connection patterns. For shading patterns where 15 or more PV cells were affected, reconnection of the cells did not result in power loss reduction. However,if the PV panel isproperly laid, only marginal shading should be expected and therefore the algorithm is a promising tool to be used dynamically with switches and a management unit integrated to the panel.