An Unlikely Combination of Experiments with a Novel High-Voltage CIGS Photovoltaic Array

A new high-voltage array comprising bipolar strings of copper indium gallium diselenide (CIGS) photovoltaic (PV) modules was inaugurated in 2005. It is equipped with a unique combination of tests, which likely have never before been deployed simultaneously within a single array: full current-voltage (I-V) traces, high-voltage leakage current measurements, and peak-power tracking or temporal stepped-bias profiling. The array nominally produces 1 kW power at 1 sun. The array´s electrical characteristics are continuously monitored and controlled with a programmable electronic load interfaced to a data acquisition system (DAS), that also records solar and meteorological data. The modules are mounted with their frames electrically isolated from earth ground, in order to facilitate measurement of the leakage currents that arise between the high voltage bias developed in the series-connected cells and modules and their mounting frames. Because the DAS can perform stepped biasing of the array as a function of time, synchronous detection of the leakage current data with alternating bias is available. Leakage current data and their dependence on temperature and voltage are investigated. Array power data are analyzed across a wide range of varying illuminations and temperatures from the I-V traces. Array performance is also analyzed from an energy output perspective using peak-power tracking data