1,720,961 research outputs found
An intelligent off-line MPPT technique for PV applications
No full textHarnessing energy from the abundant and free sunlight is now a days a hot topic among the research community. The availability of cheap solar modules has made it possible to harvest solar energy with better efficiency. The nature of solar modules is non linear and therefore the process of impedance matching is essential. The proper impedance matching ensures extraction of the maximum power from solar PV module. Several algorithms are reported in literature that are used to operate the DC-DC converter around Maximum Power Point (MPP). Among those algorithms off-line techniques are considered the easiest to implement. However, intermittent measurement of Short Circuit Current (SCC)/Open Circuit Voltage (OCV) results in the power loss. The decision about the measurement of SCC/OCV is often based on the irradiance/temperature sensors. In this paper we propose a modified algorithm for off-line MPPT techniques. The proposed technique decides intelligently about the measurement of SCC/OCV. The technique is modeled and simulated in Matlab/Simulink and the results shows satisfactory performance against test conditions
Comparative analysis of maximum power point tracking techniques for PV applications
No full textIn the wake of the growing energy requirements the use of Photovoltaic (PV) systems is increasing around the world. PV systems are not linear in nature therefore special methods are used to extract the maximum available power. The non linear characteristic of the IV curve of PV module has a unique single point of maximum power. In order to operate at that power point power electronic converters are used. These power electronic converters are controlled with the help of algorithms known as Maximum Power Point Tracking (MPPT) techniques. Various unique algorithms are found in the literature with their specific advantages and drawbacks. Keeping in view that an efficient tracking of Maximum Power Point (MPP) can increase the usability of a PV system by many folds, in this paper we present a comparison of four widely used MPPT techniques i.e 1) Fractional Short Circuit Current (FSCC), 2) Fractional Open Circuit Voltage (FOCV), 3) Perturb & Observe (P&O) and 4) Incremental Conductance (IC) MPPTs are discussed. The comparative analysis provides the pros and cons of each MPPT with a resistive load. The analysis is about the time required for each algorithm to track the maximum power and the system efficiencies
Optimization of the perturb and observe maximum power point tracker for a distributed photovoltaic system
No full textWith everyday passing, power generation from photovoltaic (PV) systems are getting increased around the globe. One of the drawbacks of PV systems is that they exhibit non-linear I-V curves with respect to atmospheric conditions. Therefore, maximum power point tracker (MPPT) technique is installed in every PV system. One of the most popular technique is perturb & observe (P&O) but this technique has some shortcomings. In this paper, MPPT technique is proposed which will optimize the P&O with respect to distributed PV (DPV) plant. Such that the deficiencies of P&O are removed. The proposed technique is designed for DPV and is working in two modes. In mode-1, decision making of the proposed technique revolves around the mutual co-ordination between two modules/arrays. During this mode, one array will behave as leader (L) while other array as follower (F). In mode-2, proposed technique utilizes the individual P&O for both arrays. Model is the superior performance mode in which efficiency of the proposed technique is better than P&O. While, in mode-2 both techniques have same efficiency. Finally, the proposed technique is modeled in Matlab/Simulink. The proposed technique is tested under various weather conditions and superior performance of the proposed technique is proved through simulation results
A novel hybrid MPPT technique for solar PV applications using perturb & observe and fractional open circuit voltage techniques
Get PDFSolar photovoltaic (PV) systems have been an area
of active research for the last few decades to improve the
efficiency of solar PV module. The non-linear nature of IV
curve of solar PV module demands some technique to track
the maximum voltage and maximum current point on IV curve
corresponding to Maximum Power Point(MPP). Thus, Maximum
Power Point Tracking (MPPT) techniques are widely deployed
for this purpose. Lot of MPPT techniques have been developed
in recent past but still most commercial systems utilizes the
perturb & observe (P&O) MPPT technique because of its simple
algorithm, low cost and ease of implementation. However, this
technique is slow in tracking MPP under rapidly changing
irradiance conditions and it also oscillates around the MPP. This
paper addresses this problematic behavior of P&O technique
and hence presents a novel MPPT hybrid technique that is
combination of two basic techniques i.e. P&O and Fractional
Open Circuit Voltage (FOCV) technique in order to overcome
the inherited deficiencies found in P&O technique. The proposed
MPPT technique is much more robust in tracking the MPP even
under the frequent changing irradiance conditions and is less
oscillatory around the MPP as compared to P&O. The technique
is verified using MATLAB/SIMULNK and simulation results
show a clear improvement in achieving the MPP when subjected
to change in irradianc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A two stage hybrid maximum power point tracking technique for photovoltaic applications
No full textPhotovoltaic (PV) systems are widely used now a days for coping the growing energy demands all across the globe. The non-linear behavior of the characteristic curve of solar module requires special arrangement to harvest maximum amount of power. To track the Maximum Power Point (MPP) across the non linear IV curve of PV module, techniques are used in addition to the power electronic circuit and are called Maximum Power Point Tacking (MPPT). Various methods of MPPT exists in literature, each bearing its own pros and cons. In this paper we presents a novel technique to improve the performance of conventional Perturb and Observe (P&O) algorithm of MPPT. Our technique removes the drawbacks of P&O under rapidly changing environmental conditions. It also executes less power oscillations under steady state conditions. The algorithm is a hybrid of Fractional Short Circuit current (FSCC) and P&O algorithms. The system takes the advantage of rapid tracking near to MPP using the FSCC and then carry on to track the exact MPP using the traditional P&O technique. The technique is verified through simulation using Matlab/SIMULIN
A New Sensorless Hybrid MPPT Algorithm Based on Fractional Short-Circuit Current Measurement and P&O MPPT
Get PDFThis paper presents a new maximum power point tracking (MPPT) method for photovoltaic (PV) systems. The proposed method improves the working of the conventional perturb and observe (P&O) method in changing environmental conditions by using the fractional short-circuit current (FSCC) method. It takes the initial operating point of a PV system by using the short-circuit current method and later shifts to the conventional P&O technique. The advantage of having this two-stage algorithm is rapid tracking under changing environmental conditions. In addition, this scheme offers low-power oscillations around MPP and, therefore, more power harvesting compared with the common P&O method. The proposed MPPT decides intelligently about the moment of measuring short-circuit current and is, therefore, an irradiance sensorless scheme. The proposed method is validated with computer software simulation followed by a dSPACE DS1104-based experimental setup. A buck-boost dc-dc converter is used for simulation and experimental confirmation. Furthermore, the reliability of the proposed method is also calculated. The results show that the proposed MPPT technique works satisfactorily under given environmental scenario
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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