Computational Intelligence for Modeling, Control, Optimization, Forecasting and Diagnostics in Photovoltaic Applications

This book is a Special Issue Reprint edited by Prof. Massimo Vitelli and Dr. Luigi Costanzo. It contains original research articles covering, but not limited to, the following topics: maximum power point tracking techniques; forecasting techniques; sizing and optimization of PV components and systems; PV modeling; reconfiguration algorithms; fault diagnosis; mismatching detection; decision processes for grid operators

A power and energy procedure in operating photovoltaic systems to quantify the losses according to the causes

Recently, after high feed-in tariffs in Italy, retroactive cuts in the energy payments have generated economic concern about several grid-connected photovoltaic (PV) systems with poor performance. In this paper the proposed procedure suggests some rules for determining the sources of losses and thus minimizing poor performance in the energy production. The on-site field inspection, the identification of the irradiance sensors, as close as possible the PV system, and the assessment of energy production are three preliminary steps which do not require experimental tests. The fourth step is to test the arrays of PV modules on-site. The fifth step is to test only the PV strings or single modules belonging to arrays with poor performance (e.g., I-V mismatch). The sixth step is to use the thermo-graphic camera and the electroluminescence at the PV-module level. The seventh step is to monitor the DC racks of each inverter or the individual inverter, if equipped with only one Maximum Power Point Tracker (MPPT). Experimental results on real PV systems show the effectiveness of this procedure

Neighboring-Pixel-Based Maximum Power Point Tracking Algorithm for Partially Shaded Photovoltaic (PV) Systems

In this paper, a neighboring-pixel-based virtual imaging (NPBVI) technique is developed to comprehensively detect the shading conditions on PV arrays. The proposed VI technique is then merged with a probabilistic mechanism of shaded module currents. Finally, a mathematical model is presented, which predicts the current voltage (I-V) region corresponding to the global maximum (GM) of the shaded PV array. The effectiveness of the proposed NPBVI MPPT is validated through numerous experiments that were carried out using a hardware prototype with a 150 W power rating. For the experiments, a PV array consisting of 3 × 2 (Np× Ns ) 20 W PV modules was utilized. The experiments showcase agreement that the proposed method successfully identified the GM region of a partially shaded PV array

Research on MPPT methods for photovoltaic system based on microgrid

This thesis introduces some basic concepts about a microgrid. Then it discusses the structure of photovoltaic system (PVS) which contains a solar panel and simplified PV models. Next, it discusses and compares different methods for Maximum Power Point Tracking (MPPT) with PVS. It presents three types of DC-DC converters -- Buck, Boost and Buck-Boost converter. This work proposes to apply a DC-DC converter of Buck-Boost type to make PVS controllable because this type of converter has the largest range for operational region so that it can get the best result on MPPT. Finally, this thesis presents a kind of new MPPT method based on fuzzy logic theory. It concludes that the proposed method is effective in achieving MPPT in comparison with the prior arts

Modelling CPV

A methodology for the simulation of CPV systems is presented in four distinct sections: input, optics, uncertainty and electrical output. In the input section, existing methods of describing the solar irradiation that is incident at the primary optical element of a CPV system are discussed, the inadequacies of the existing methods are explored and conditions of validity for their use drawn. An improved and spectrally extended model for a variable, spatially resolved solar image is arrived at. The model is used to analyse losses at the primary concentration device stage under varying solar profiles and air masses. A contextual analysis of an example Seattle based CPV system operating with constant solar tracking errors of 0.3-0.4° show a corresponding loss in isolation available to the optical system of 5-20%, respectively. In the optics section, an optical ray trace model is developed specifically for this work. The optical ray trace model is capable of the spectrally resolved ray tracing of all insolation input models discussed above. Plano-convex and Fresnel lenses are designed, investigated and compared using each of the insolation models described in the input section. Common CPV component material samples for the plano-convex and Fresnel lenses are analysed for their spectrally resolved optical properties. The computational expense of high resolution spatial and spectral modelling is addressed by means of a spectrally weighted banding method. The optical properties parameter spectral weighting method can be applied to any arbitrary spectral band. The bands used herein correspond to the active ranges of a typical triple-junction solar cell. Each band shows a different spectral dependency. Banded beam irradiation proportions are shown to change by as much as 10% in absolute terms within the air mass range of 1 to 3. Significant variations in spectrally banded illumination profiles are found with the extended light source insolation model. These banded variations are mostly unaccounted for with the use of approximated insolation models, further compounding the argument for extended light source Sun models in CPV system simulations. In the uncertainty section, the limitations of the manufacturing process are explored. Manufacturing tolerance errors from manufacturer datasheets are presented. These production uncertainties are used in the design of an erroneous plano-convex lens which is then analysed with the optical modelled presented in the optics section and compared to the ideal design specification. A 15% variation in maximum intensity value is found alongside a linear shift in the focal crossover point of approximately 0.2mm, although the optical efficiency of the lens remains the same. Framing manufacture errors are investigated for a square Fresnel lens system resulting in a linear shift of the focal centre of approximately 0.85mm. A process for the calculation of wind loading force on a CPV array is also presented. The process uses real 2 second resolution wind data and highlights the chaotic nature of loading force. A maximum force of 1.4kN was found on an example day for a 3m by 3m by 0.1m cuboid (i.e. CPV array); corresponding to a wind speed of approximately 13m/s, which is well within the typical operating range of a CPV tracking system. In the electrical output section, a spatially resolved solar cell model is identified and used for the investigation of solar cell performance under the inhomogeneous cell illumination profiles produced in the uncertainty section. Significant differences in the maximum power point of the cell IVs are found for the ideal and erroneous system illumination profiles. Approximately, a 15% variation is found in the plano-convex lens example, with a relative difference of 4% attributable to illumination profile distortion, and a 6% variation in the module framing component example. These results further highlight the need for the consideration of production uncertainties in CPV system simulation

A unique radiometric measurement station design incorporating spectral and image data collection

Thesis (MEng)--Stellenbosch University, 2022.ENGLISH ABSTRACT: The performance of photovoltaic (PV) panels is determined under standard test condi tions (STC). However, in practical PV installations, it is rare for PV panels to operate under the STC at which they are rated. The variation in spectral irradiance under dif ferent atmospheric conditions significantly i mpacts t he p erformance of P V p anels. The output of a PV power plant is also significantly a ffected a s a l arge c loud b ank travels across the sky above. The passing clouds attenuate the received solar spectral irradiance and reduce the output power. Sudden changes in output power of a grid connected plant, as a result of clouds, may lead to voltage and frequency oscillations and result in system instability. Accurate short-term irradiance prediction models are important tools used to manage these power fluctuations. However, many irradiance prediction models and software tools used in the PV industry do not take these spectral impacts on PV performance into account. There is a lack of measurement stations dedicated to collecting the data necessary to improve these prediction models and software tools. A unique radiometric measurement station is designed and built in this thesis for the collection of data required by researchers to improve upon irradiance forecasting models and PV software tools. The instruments on the measurement station include: a pyranometer, a pyrheliometer, a wide field-of-view (FOV) spectral irradiance meter, a narrow FOV spectral irradiance meter and a digital camera. The instruments are mounted on a pan/tilt unit that is able to accurately track the position of the sun in the sky throughout the day for solar elevation angles greater than 10◦ . The data collected by the station includes temperature, humidity, air pressure, broadband irradiance and spectral irradiance. Images of the sky correlating to the various irradiance measurements are captured by the onboard digital camera. The measurement station is designed to be solar powered, compact and weather-resistant, allowing it to be deployed in remote locations for data collection. The station is configured t o c apture a m easurement s et o f d ata o nce e very 1 0 minutes in 4 distinct measurement positions: facing directly towards the sun, facing north with optimal tilt, facing north with a fixed 30◦ tilt, and facing north with a 0◦ tilt. The mea surement frequency and measurement positions can be configured by the user as necessary. The broadband irradiance measurements are validated by comparison to data collected by an independent measurement station nearby. The correlation between the spectral irradiance measurements and the AM1.5 reference spectrum is shown, as well as the vari ation of the solar spectrum during different seasons, different times of day and different cloud conditions. The measurement station is found to fulfil all requirements and successfully collects the data required to improve irradiance prediction models and PV software tools. This station has the potential to help optimize PV power stations as well as domestic PV installations.AFRIKAANSE OPSOMMING: Die werkverrigting van fotovoltaïese (FV) panele word by standaard toets toestande bepaal. In praktiese toepassings is dit selde dat daar aan standaard toets toestande voldoen word. Die variasie in spektrale bestraling onder verskillende atmosferiese toestande beïnvloed die werkverrigting van FV-panele aansienlik. Die uitset van ’n FV-kragstasie word aansienlik geaffekteer soos groot wolkbanke deur die lug beweeg. Die verbygaande wolke verswak die sonbestraling wat ontvang word en verminder die totale FV uittree drywing. Skielike veranderinge in uittree drywing as gevolg van wolke kan lei tot spanning en frekwensie ossillasies, wat lei tot stelsel onstabiliteit. Akkurate korttermyn bestraling voorspellingsmodelle is belangrike gereedskap wat gebruik word om hierdie krag fluktuasies te bestuur. Baie bestraling voorspellingsmodelle en sagteware wat in die FV-industrie gebruik word, neem egter nie hierdie spektrale impakte op FV-prestasie in ag nie. Daar is ’n tekort aan meetstasies wat toegewy is om die data in te samel wat nodig is om hierdie voorspellings modelle en sagteware te verbeter. ’n Unieke radiometriese meetstasie is in hierdie tesis ontwerp en gebou. Die meetstasie is verantwoordelik vir die insameling van data wat deur navorsers benodig word om die huidige bestraling voorspellingsmodelle en FV sagteware te verbeter. Die instrumente op die meetstasie sluit in ’n pyranometer, ’n pirheliometer, ’n wye gesigsveld spektrale bestralingsmeter, ’n nou gesigsveld spektrale bestralingsmeter en ’n digitale kamera. Die instrumente is op ’n sonvolgeenheid gemonteer wat die posisie van die son regdeur die dag akkuraat kan volg vir sonhoogte hoeke groter as 10 grade. Die data wat die meetstasie insamel sluit temperatuur, humiditeit, lugdruk, breëband bestraling en spektrale bestraling in. Beelde van die lug wat verband hou met die verskillende bestralingsmetings word deur die digitale kamera aan boord gestoor. Die meetstasie is ontwerp om sonkrag-aangedrewe, kompak en weerbestand te wees, sodat dit in afgeleë plekke vir data-insameling ontplooi kan word. Die meetstasie is opgestel om een keer elke 10 minute data op te neem in 4 verkillende metingsposisies. Dit sluit in ’n meting wat direk na die son kyk, ’n meting wat noord kyk met optimale kanteling, ’n meting wat noord kyk met ’n vaste 30 grade kantel, en ’n meeting wat noord kyk met ’n 0 grade kantel. Die metingsfrekwensie en metingsposisies kan deur die gebruiker verander word soos nodig. Die breëband-bestralingsmetings word geverifieer deur dit te vergelyk met data wat deur ’n nabye onafhanklike meetstasie ingesamel is. Die korrelasie tussen die spektrale bestra lingsmetings en die AM1.5-verwysingspektrum word getoon, sowel as die variasie van die sonspektrum gedurende verskillende seisoene, verskillende tye van die dag, en verskillende wolktoestande. Daar word gevind dat die meetstasie aan alle vereistes voldoen. Die nodige data om die bestraling voorspellings modelle en FV-sagteware te verbeter word suksesvol versamel deur die gebruik van die meetstasie. Hierdie stasie het die potensiaal om FV-kragstasies sowel as huishoudelike FV-installasies te help optimeer.Master

Performance evaluation of the photovoltaic system

The various renewable energy source technologies, Photovoltaics (PV) transforming sunlight directly into electricity, have become standard practice worldwide, especially in countries with high solar radiation levels. PV systems have been developed rapidly over recent years, and many new technologies have emerged from different producers. For each type of PV module, manufacturers provide specific information on rated performance parameters, including power at maximum power point (MPP), efficiency and temperature factors, all under standard solar test conditions (STC) 1000 W/m2. Air. In addition, the mass (AM) of 1.5 and the cell's temperature was 25 ̊C. Unfortunately, this grouping of environmental conditions is infrequently found in outdoor conditions. Also, the data provided by the manufacturers are not sufficient to accurately predict the performance of photovoltaic systems in various climatic conditions. Therefore, monitoring and evaluating the performance of the off-site systems is necessary. This thesis aims to overview various photovoltaic technologies, ranging from crystalline silicon (c-SI) to thin-film CdTe and GiCs. The following are the main parameters for evaluating the external units' performance to describe the PV systems' operation and implementation. In addition, a review of the impacts of various environmental and operational factors, such as solar radiation, temperature, spectrum, and degradation

Performance Study of Solar Power Source for Wireless Systems

Photovoltaic (PV) technology is an attractive power source for systems with no wired connections to any network. Because of seasonal variations of solar irradiation, designing such a system requires careful analysis in order to provide required level of reliability. In this paper we present results of 16-month measurements of experimental PV system located in Poland. Obtained irradiation values have been verified with reference data from independent sources. The results of this work may be helpful in forecasting the performance of similar PV systems in the same region and allow to make more precise forecasts of power system performance than based only on average monthly irradiation tables

Random Finite Sets Based Very Short-Term Solar Power Forecasting Through Cloud Tracking

Tracking clouds with a sky camera within a very short horizon below thirty seconds can be a solution to mitigate the effects of sunlight disruptions. A Probability Hypothesis Density (PHD) filter and a Cardinalised Probability Hypothesis Density (CPHD) filter were used on a set of pre-processed sky images. Both filters have been compared with the state-of-the-art methods for performance. It was found that both filters are suitable to perform very-short term irradiance forecasting