Novel field test design for acquisition of DC and AC parameters during service

Being able to monitor early signs of PV module degradation, is needed to ensure stable power production throughout the service life of a PV installation. Recently, impedance spectroscopy is proven to be a useful tool for detection of the presence and location of significant errors, and may have potential for more. In this work we describe a field test design where the modules are operating at their maximum power point, and via relays is switched out one by one for acquisition of an IV curve and an impedance spectrum. Some of the modules involved will undergo stimuli to accelerate certain degradation mechanisms, and fitting parameters extracted from the field test will be correlated with irradiance and compared to similar parameters of virgin modules of same kind, and conventional laboratory measurements on the same modules. The proposed method will provide data for exploration of early degradation signs using impedance measurements.