Degradation of photovoltaic panels induced by electric potential: Theoretical survey and computational study on the inverter operation influence

This work presents a thorough survey on the Potential Induced Degradation (PID) of solar panels, describing its actuation mechanisms, influencing factors, resulting damages and impact of the electric system characteristics (grounding type, presence of inverters, cell association, etc) on its severity, among other issues. Along the development of this work, the authors formulated the hypothesis that the common voltage produced by the PWM switching of the inverter bridge could propagate over the photovoltaic installation and be combined with the voltage between the module terminals (poles) and the ground, eventually resulting in substantial voltage shifts. Since the TCO corrosion and the polarization phenomenon are strongly dependent on the poles potential in relation to the (grounded) module frame, the inverter could then worsen the PID. In this context, in order to investigate such suspicion, a computational case study was performed, where a complete photovoltaic system was implemented in Matlab/Simulink, with seven different configurations. For each of them, the common mode voltage and currents, which are produced by the inverter and propagate over the installation, had their profile determined at the connection point of the panels and analyzed under the PID phenomenon context.