Diagnostics of PID Early Stage in PV Systems

Abstract

Potential induced degradation (PID) is a serious threat for the photovoltaic (PV) industry. The risk of PID may increase with increasing operating voltage of PV systems. Although PID tests are currently standard tests, the expansion of floating PV power plants and installation in humid climates show that PID-free modules are still sensitive to this type of degradation. Therefore, a method that can detect PID in the initial phase before standard tests reveal it, is necessary to increase the reliability of PV systems and maintain their lifetime. One possible tool for revealing early-stage PID manifestations is impedance spectroscopy and I-V dark curves measurements. Both IS and dark current measurement methods are sensitive to cell shunt resistance (RSH), which is strongly influenced by PID before significant power loss and can act as an early stage PID detection mechanism. The paper describes the differences of the common P-type PV module parameters both during the degradation process and also during the regeneration process when diagnosed by conventional and IS and dark current measurement methods.