OptimalI-VCurve Scan Time of Solar Cells and Modules in Light of Irradiance Level

摘要

High-efficiency solar cells and modules exhibit strong capacitive character resulting in limited speed of transient responses. A too fastI-Vcurve measurement can thus introduce a significant error due to its internal capacitances. This paper analyses theI-Vcurve error of a measured solar cell or module in light of scan time and irradiance level. It rests on a two-diode solar cell model extended by two bias-dependent capacitances, modelling the junction, and the diffusion capacitance. A method for determination of all extended model parameters from a quasistaticI-Vcurve and open-circuit voltage decay measurement is presented and validated. Applicability of the extended model and the developed parameter extraction method to PV modules is demonstrated and confirmed. SPICE simulations of the extended model are used to obtain theI-Vcurve error versus scan time dependence and theI-Vcurve hysteresis. Determination of the optimal scan time is addressed, and finally the influence of the irradiance level on theI-Vcurve scan time and error is revealed. The method is applied but is not limited to three different wafer-based silicon solar cell types.