Partial shadowing of photovoltaic systems can overproportionally
reduce the energy yield and lead to early ageing
and failure of the shadowed cells. Large area shadows are
relatively easy to detect due to the eminent power reduction and
decrease of fill factor. However, small area partial shadows in a
larger system do not have a very obvious effect on the output
power or fill factor of the PV array and can remain undetected,
leading to failure. In this paper a method for detecting small
area partial shadows, based on equivalent thermal voltage, is
presented. A simplified expression of the equivalent thermal
voltage is proposed, which increases the robustness against
measurement errors and model limitations at low irradiation
conditions. Experimental results confirm the high sensitivity of
the method even to a relatively small area shadow, while showing
very good robustness against increase in series resistance.
CitacióSera, D.; Teodorescu, R.; Rodriguez, P. Partial shadowing detection based on equivalent thermal voltage monitoring for PV module diagnostics. A: International Conference on Industrial Electronics, Control, and Instrumentation. "IECON2009". Porto: 2009, p. 708-713.