Partially shaded operation of a grid-tied PV system

Abstract

Partial shading of a PV installation has a disproportionate impact on its power production. This paper presents background and experimental results from a single string grid-tied PV system, operated under a variety of shading conditions. In this configuration a shadow can represent a reduction in power over 30 times its physical size. Results are presented relating size and positions of shading to power reduction of the PV system. A simulation method is also described that provides an accurate description of shade based on a single site survey. This process can provide the basis for an accurate simulation of power reduction in a partially shaded PV system.

Evaluation of the impact of partial shading and its transmittance on the performance of crystalline silicon photovoltaic modules

“…The crystalline solar cells of the modules are forced to work under partial shading with percentages: 25, 50, 75 and 100% on different parts of the module. However, the shading of a cell or group of cells does not have enough impact on the output power of a photovoltaic module (Deline, 2009) as some of the power is dissipated as heat by the shaded cell. The duration of the power drop is related to the type of shadow on the PV dule such as dirt, building environment, leaves, dust etc.…”

Partial Shading of PV System Simulation with Experimental Results

“…When a bypass diode begins conducting, the module voltage will drop by an amount corresponding to the sum of cell voltages protected by the same bypass diode plus the diode forward voltage, but current from surrounding un-shaded groups of cells continues around the group of shaded cells. The effect of shade on power output of typical PV installation is nonlinear in that a small amount of shade on a portion of an array can cause a large reduction in output power [8][9][10].…”

Design and evaluation of a modular resonant switched capacitors equalizer for PV panels

“…An intuitive overview of the equalization operation can be obtained by considering a simplified equivalent circuit (Fig. 2); in the circuit each panel is emulated as a current source with passive circuitry [21] and each EQSCC as an isolated 1:1 "DC transformer" emulated as two dependent sources with series resistances (R e (1) , R e (2) ) that represent the internal losses. This arrangement equalizes the voltage of the two adjacent panels and, consequently, of all the panels in the string (to within the voltage drop caused by the losses).…”

“…Full or partial shading of PV panels, which are part of a serially connected array, limits the power that can be extracted from the chain [1,2]. Two groups of solutions have been proposed to remedy the shading problem: solutions that are based on a dedicated converter/inverter per panel [3][4] and those that keep the series connection of the panels, but replenish the lower current of the shaded panel(s) with parallel feedback circuitry [5][6][7].…”