Abstract-Determination of PV model parameters usually requires time consuming iterative procedures, prone to initialization and convergence difficulties. In this paper, a set of analytical expressions is introduced to determine the five parameters of the single-diode model for crystalline PV modules at any operating conditions, in a simple and straightforward manner. The derivation of these equations is based on a newly found relation between the diode ideality factor and the open circuit voltage, which is explicitly formulated using the temperature coefficients. The proposed extraction method is robust, cost-efficient and easy-to-implement, as it relies only on datasheet information, while it is based on a solid theoretical background. Its accuracy and computational efficiency is verified and compared to other methods available in the literature through both simulation and outdoor measurements.
-In order for a PV system to provide a full range of ancillary services to the gird, including frequency response, it has to maintain active power reserves. In this paper, a new control scheme for the dc/dc converter of a two-stage PV system is introduced, which permits operation at a reduced power level, estimating the available power (maximum power point -MPP) at the same time. This control scheme is capable of regulating the output power to any given reference, from near-zero to 100% of the available power. The proposed MPP estimation algorithm applies curve fitting on voltage and current measurements obtained during operation to determine the MPP in real time. This is the first method in the literature to use the non-simplified singlediode model for the determination of the MPP and the five model parameters while operating at a curtailed power level. The developed estimation technique exhibits very good accuracy and robustness in presence of noise and rapidly changing environmental conditions. The effectiveness of the control scheme is validated through simulation and experimental tests using a 2 kW PV array and a dc/dc converter prototype at constant and varying irradiance conditions. Index Terms -Active power control, curve fitting, linearized converter model, maximum power point tracking (MPPT), photovoltaic (PV), power reserves, single-diode model.
In this paper, new expressions are introduced for the determination of the maximum power point (MPP) of photovoltaic (PV) systems as explicit functions of the five parameters of the single-diode model employing the Lambert W function. These equations provide the voltage and current at MPP in a direct and straightforward manner, thus dispensing with any need for iterative solution. They are initially derived for a PV system operating under uniform conditions, and subsequently extended for mismatched conditions at the PV string level. The novelty of these formulae lies in their solid theoretical foundation, which supports their validity in the general case and offers a well-founded symbolic formulation for the MPP evaluation problem. Extended simulations and experimental validation are performed to verify the accuracy and computational efficiency of the proposed equations compared with other methods available in the literature. Index Terms-Direct calculation, explicit expressions, five parameters, Lambert W function, maximum power point (MPP), partial shading, photovoltaic (PV), single-diode model.NOMENCLATURE a Modified diode ideality factor of the single-diode model. I mp Current at MPP. I mp I Current at MPP I . I ph Photocurrent of the single-diode model. I s Diode saturation current of the single-diode model. I sc Short-circuit current. MPP Maximum power point. MPP I Near-MPP operating point, where the output of the ideal component of the PV device model is maximized. P mp Output power at MPP. P mp I Output power at MPP I . R L I Load resistance connected to the PV device terminals for operation at MPP I . R ideal I Apparent load resistance at the terminals of the ideal component of the PV device model, for operation at MPP I . R s Series resistance of the single-diode model. Manuscript
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