Validation of In-Situ I-V Measurement Unit for PV System Monitoring Applications

Electrical output measurement of PV reference modules in an array is used for a variety of applications in PV system monitoring, including measurements of irradiance and soiling as well as detection of degradation and faults. Using currently available measurement equipment, reference modules are typically standalone modules installed alongside the array, which results in extra costs for system engineering and racking. New products will allow measuring I-V curves on power-producing PV modules in-situ within a PV array, simplifying implementation. However, for in-situ use it is critical that the I-V measurement unit does not disturb inverter operation or reduce energy output. In this work we developed a test protocol to quantify impacts of the I-V unit on inverter energy output and evaluated a new in-situ I-V measurement product in multiple arrays. In initial results, we found no adverse impact of the I-V unit on inverter operation, with minimal power loss approximately as expected from the series resistance and duty rate of the I-V measurement.