1,720,975 research outputs found
A method for the analytical extraction of the single-diode PV model parameters
No full textDetermination 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.</p
Simple PV Performance Equations Theoretically Well Founded on the Single-Diode Model
Full text linkThere are several photovoltaic (PV) performance models in the literature, but most of them either employ complex and tedious calculations or require additional measurements apart from datasheet information. In this paper, a new set of performance equations to evaluate the short-circuit current, open-circuit voltage, and maximum power point at any operating conditions is introduced. The proposed expressions are simple functions of the irradiance and temperature, while they are generally applicable to any crystalline PV module and require only datasheet information as input data. This is achieved by introducing new formulas to determine the irradiance and temperature coefficients that are not provided in the datasheet, thus avoiding empirical constants or additional measurements. The novelty of the performance equations is their solid theoretical background, as they are in excellent agreement with the single-diode PV model, combined with simple and easy application. The proposed PV model is validated and compared with other methods found in the literature through simulations in MATLAB and outdoor measurements on commercial PV modules
Statistical Analysis of Solar Irradiance Variability
No full textSolar photovoltaic (PV) generation forecasting is an important tool to power system operators, but struggles under conditions of intermittent solar irradiance. Although studying and forecasting irradiance itself has been the subject of muchresearch, little progress has been made on the variability (or fluctuation) of irradiance and its statistical properties, despite it being an important parameter in generation forecasting, state estimation and other power system applications. This paper takes a close look into the statistical nature of irradiance variability and shows that it can be sufficiently modeled by a Gaussian Mixture Model (GMM) of six components. Furthermore, an investigation on the required time resolution demonstrates that sub-minute resolution is necessary to accurately capture irradiance variability.The analysis is performed on a one-second resolution irradiancedataset provided by NREL
An explicit pv string model based on the lambert w function and simplified mpp expressions for operation under partial shading
No full textIn this paper, a reformulation of the widely used one-diode model of the photovoltaic (PV) cell is introduced, employing the Lambert W function. This leads to an efficient PV string model, where the terminal voltage is expressed as an explicit function of the current, resulting in significantly reduced calculation times and improved robustness of simulation. The model is experimentally validated and then used for studying the operation of PV strings under partial shading conditions. Various shading patterns are investigated to outline the effect on the string I-V and P-V characteristics. Simplified formulae are then derived to calculate the maximum power points of a PV string operating under any number of irradiance levels, without resorting to detailed modeling and simulation. Both the explicit model and the simplified expressions are intended for application in shading loss and energy yield calculations.</p
Electrical modeling of bifacial PV modules
No full textAlthough the bifacial photovoltaic (PV) module is now a mature technology, there still exists a gap in the literature on its electrical modeling and equivalent circuit representation. Most published studies have mainly focused on the photocurrent while overlooking other crucial parameters for the electrical response of the module. Even so, the photocurrent of the bifacial module is simplistically treated as the sum of individual currents of the front and rear sides, a hypothesis challenged in this study. Notably, our research has uncovered a discrepancy that can exceed 15%, and we address this issue by introducing a correction factor in this paper. This paper introduces a comprehensive electrical model that effectively integrates bifacial PV modules’ front and rear sides into a single−circuit representation. This novel model adopts the single−diode equivalent circuit, formulating each of the five parameters as a function of the individual side’s parameters. Indoor and outdoor measurements validate the accuracy improvement brought by this model, which can benefit energy yield studies and our theoretical understanding of bifacial PV systems
Partial shading analysis of multistring PV arrays and derivation of simplified MPP expressions
No full textIn this paper, the electrical response of a partially shaded photovoltaic (PV) array, comprising several strings connected in parallel, is investigated. The PV array is simulated by employing an enhanced version of the widely used single-diode model, reformulated in an explicit manner employing the Lambert W function. The multiple maximum power points (MPPs) that appear on the P-V characteristic of the array in partial shading conditions are analyzed, in terms of their number and properties. Simplified empirical expressions are then derived to calculate the voltage, current, and power for each local MPP, at any irradiance level and temperature, using only datasheet information, in a most simple and straightforward manner, without resorting to detailed modeling and simulations. The derived formulae are validated using both simulation and experimental results
Universal active power control converter for DC-Microgrids with common energy storage
No full textThis paper presents a battery integrated Power Flow Controller (PFC) which is found effective for the interconnection of several dc microgrids. The configuration offers delicate control over load-flow and also provides a way for the integration of Common Energy Storage (CES) to the adjacent grids. The CES is more effective when both the grids have surplus or deficit of power compared to their individual storage capacity (if any). In this paper, a Universal Active Power Control Converter (UAPCC) is proposed (which is basically a three-port converter), where port-1 is connected in parallel with the line, port-2 is connected in series with the line, and port-3 is connected to the CES through a bidirectional dc-dc converter. Relevant control algorithms have been developed for the operation of such system satisfying various system requirements that are inevitable for the interconnection of dc microgrids. The proposed control methods allow decoupled operation of three ports to control power flow between dc grids and CES independently. The complete system along with control methods are initially verified through computer simulation using MATLAB/SIMULINK. Thereafter, a prototype is developed in the laboratory at 380 V level to experimentally validate the concept. The results show effectiveness of the UAPCC for interconnection of dc microgrids with CES
MPP estimation of PV systems keeping power reserves under fast irradiance changes
No full textMaintaining power reserves in a photovoltaic (PV) system, i.e. operating at a curtailed power level, is a promising method towards grid support functions without energy storage. A major challenge in this approach is to monitor the maximum power (i.e. the available headroom) as it changes over time with the irradiance and temperature. This paper presents a new method to estimate the maximum power point (MPP) power and voltage in real-time, designed for very fast irradiance changes. While keeping reserves, the single-diode PV model equations are applied to voltage and current samples to estimate the conditions and maximum power, rather than using potential erroneous irradiance and temperature sensors. This is the first model-based method to guarantee estimation robustness regardless of the irradiance transient. Furthermore, the operating point perturbation is infrequent and limited, resulting in near-perfect MPPT efficiency at zero reserve levels. The effectiveness of the proposed method is validated via simulations in MATLAB/Simulink on a 10 kW PV system assuming noisy measurements. </p
Energy models for photovoltaic systems under partial shading conditions: a comprehensive review
Full text linkThe partial shading phenomenon and its implications on the electrical response and energy yield of photovoltaic (PV) systems have received increased attention in the last years. In order to study, foresee and mitigate such effects, several energy models are proposed in the bibliography, presenting different degrees of complexity, accuracy and applicability. This study presents an overview of the state of the art in the development of models for PV systems under partial shading conditions. Alternative modelling approaches are analysed, highlighting their advantages and shortcomings and models available in the literature are reviewed and classified according to important attributes, related to their accuracy and implementability. Current research trends, as well as topics that warrant further investigation, are identified and discussed
Direct MPP Calculation in Terms of the Single-Diode PV Model Parameters
Full text linkIn 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
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