Shaded Array Research Articles

Falcon optimiser for optimal design of Even-Odd column for shaded PV array reconfiguration

ABSTRACT The operation of Photo-Voltaic (PV) arrays is often negatively impacted by the presence of shadows, which significantly reduce the generated power. Shadows create multiple local Maximum Power Points (MPP) and a unique global MPP within the shaded array. Therefore, it is crucial to distribute shadows evenly across the PV array surface to optimise power extraction by reconfiguring the shaded modules. This paper presents a novel approach for reconfiguring Solar Photovoltaic (PV) systems using the Falcon optimiser, specifically focusing on Even-Odd column reconfiguration. The objective is to optimise the performance of the PV system by strategically rearranging the columns of PV modules. The proposed technique aims to minimise shading effects and maximise power generation efficiency by identifying the optimal placement of modules. The Falcon optimiser, known for its efficient and effective optimisation capabilities, is utilised to determine the optimal configuration. Extensive simulations and comparisons with other reconfiguration methods are conducted to evaluate the performance of the proposed approach. The results demonstrate that the Even-Odd column reconfiguration based on the Falcon optimiser significantly improves the overall power output and efficiency of the solar PV system compared to alternative methods.

Binary firefly algorithm based reconfiguration for maximum power extraction under partial shading and machine learning approach for fault detection in solar PV arrays

The functioning of a photovoltaic (PV) array in the shadow presents significant issues owing to power loss, which affects the harvested power. One of the greatest promising methods for reducing the effect of shadow over the array is reconfiguration. Therefore, this work proposes a modern metaheuristic Binary Firefly Algorithm (BFA) technique for solving the reconfiguration mechanism of a partial shade PV array. The proposed BFA is tested on a 9 × 9 panel PV array with four established shadow arrangements: short wide (SW), long wide (LW), short narrow (SN), and long narrow (LN). The proposed BFA approach yields configurations superior when compared to existing reconfigurations. The best GMP boost obtained with the proposed BFA concerning TCT configuration is 36% in the SW shadow pattern, 30 in the LW arrangement, while the least is 7% in the SN and LN patterns. To evaluate the ability of the proposed system, it is compared with other reconfiguration methods tested across various performance metrics such as fill factor, mismatch power loss, percentage of power loss, and power enhancement. The energy estimates and revenue generation demonstrate that the proposed BFA approach generates 15% more power than the TCT setup and other methods. Furthermore, the Nave Bayes based Machine Learning (ML) approach is applied to detect physical degradation in PV panels. To validate the performance proposed ML method and other techniques are undergone with both faulty and non-faulty conditions. The output of the proposed ML technique-based identification of faults approach is compared to existing techniques. The acquired results supported the proposed BFA with ML's ability and superiority in optimally reconfiguring the shaded array.

MBOA based PV Array Interconnection Scheme for Enlarging the Harvested Power under PS Condition

Massive penetration of Photovoltaic (PV) systems into the electric supply system poses several problems in the current era, as PV systems have become a feasible alternative to non-renewable energy supplies. On the other hand, partial shading (PS) is a critical issue that impacts the production and lifespan of PV plants. The interconnection of PV is an effective approach for dealing with the PS issues. It is accomplished by arranging the PV modules, based on their temperature and shading stages. In this paper, the Modified Butterfly Optimization Algorithm (MBOA) is proposed to reorganise the PV array. Several criteria are used to assess the performance of the proposed algorithm, including mismatch losses, fill factor, power loss, and percent of power enhancement. Furthermore, the achieved results are related to a standard Total-Cross-Tied (TCT), SuDoKu, Competence Square (CS), and Butterfly Optimization Algorithm (BOA). The highest increase in Global Maximum Power (GMP) has been attained by the proposed MBOA corresponding to the TCT array is 35.76% in the short wide shadow arrangement, while the least increase of 6.59% occurs in the short narrow arrangement. The acquired results reveal that the proposed MBOA’s capability and predominance in optimising the shaded array interconnection.

On the sound fields of oblate and prolate hemispheroids in infinite baffles for directivity control.

The hemispheroid is presented as an apodized form for controlling the beam width of a sound source by varying its height-to-radius ratio. Directivity patterns, on-axis responses, and radiation impedances are calculated for various height-radius ratios of the oblate hemispheroid using spheroidal wave functions. It turns out that, for smaller angles at least, there is a direct relationship between the internal angle of the semi-elliptic cross section and the half-cone angle within which the far-field pressure is largely contained at high frequencies. The hemispheroid is compared with both a spherical cap, which produces a much less regular response, and a high-frequency asymptotic approximation. The high-frequency asymptotic approximation is in the form of a flat circular radiator with a delay that increases radially from the center to the perimeter, as used in some electrostatic loudspeakers. With the almost complete absence of lobes, this appears to be an effective alternative means of apodization to a shaded array and is more efficient because, unlike a shaded array, constant axial velocity is maintained over the whole surface. A high-frequency approximation is also derived for a prolate hemispheroid. Since this may be formed from a planar array, a beam steering option is added.

A robust photovoltaic array reconfiguration strategy based on coyote optimization algorithm for enhancing the extracted power under partial shadow condition

The operation of photovoltaic (PV) array under shade faces great challenges due to the power loss that reduces the extracted power. Reconfiguration process is one of the most promising solutions to reduce the effect of shadow on the array. However, the physical array relocation methods like total cross-tied (TCT) and Su Do Ku have some limitations due to their complicated arrangements. Therefore, this paper presents a recent metaheuristic approach of coyote optimization algorithm (COA) to solve the reconfiguration process of the partially shaded PV array. The main target is maximizing the global maximum power (GMP) extracted from the array. The proposed COA is applied on 9×9 PV array operated under four standard shadow patterns which are short wide (SW), long wide (LW), short narrow (SN), and long narrow (LN). The obtained configurations via the proposed COA method are compared to TCT, Su Do Ku, flower pollination algorithm (FPA), marine predators algorithm (MPA), and butterfly optimization algorithm (BOA) based arrangements. The best enhancement of GMP obtained via the proposed COA with respect to TCT configuration occurs in SW shadow pattern of 26.58% while the least on is 7.68% placed in SN pattern. The obtained results confirmed the competence and superiority of the proposed COA in reconfiguring the shaded array optimally.

Multi-Objective Grey Wolf Optimizer for Optimal Design of Switching Matrix for Shaded PV array Dynamic Reconfiguration

One of the worst negative phenomena faced by photovoltaic (PV) array is the operation under the shadow phenomenon, which significantly affects the generated power. Multiple local maximum power point (MPP) and unique global MPP are generated from the shaded array. Therefore, regular dispersion of the shadow falling on the PV array surface is a vital issue to extract the GMP via reconfiguration of the shaded modules in the array. This article proposes a recent approach based on Multi-objective grey wolf optimizer (MOGWO) to reconfigure the shaded PV array optimally. The main objective of the proposed MOGWO is providing the optimal structure for the switching matrix to minimize the row current difference and maximize the output power. The benefits of the proposed strategy is performing a dynamic reconfiguration process which closes to the reality. The proposed method is validated across $9 \times 9$ PV array with six shade patterns. MOGWO schemes results are compared with TCT and modified SuDoKu based on several statistical metrics. The comparison reveals the superiority of MOGWO in tackling the multi-peak issue in the P-V characteristics with harvesting the highest power levels.

Investigation of the losses of photovoltaic solar systems during operation under partial shading

The article deals with research in solar power plants and Renewable Energy Laboratory. The purpose of research was to study the influencing of partial shading on the energy efficiency of photovoltaic installations in various connection options. As the title implies the article describes a study of the possibilities of increasing their energy efficiency when operating under different conditions. It is spoken in detail about replacement of "block connection" panels to the "in-line connection", in case of partial shading by the previous string. It is shown that substitution allows to obtain a significantly higher power - up to 8 times. It is examined that the horizontal arrangement of the panels instead of the vertical, under the same conditions, also allows up to 5 times the power of the partially shaded array in the case "in-line connection" and by 34% in the case of a "block connection". It is analyzed that parallel connection of partially shaded photovoltaic array with normally illuminated, requires voltage matching, for the selection of electrical energy at the point of maximum power, which makes it possible to obtain much more energy from the shaded array. It is experimentally shown that when using the "Intelligent maximum power selection device" that implements the voltage matching, it is possible to increase the array power up to 4 times with partial shading of 3 panels of 18. It should be noted that the choice of methods that allow receiving energy from shaded panels through individual matching converters does not permit significantly increasing the energy production of partially shaded array. It is experimentally shown that as a result of their use the array power does not increase by more than 2.5%. The results of research can be used in the design of new installations based on photovoltaic cells and the modernization of existing ones.

Matlab/Simulink Based Modeling to Study Effect of Partial Shadow on Solar Photovoltaic Array

Solar module is considered as fundamental power transformation unit of Photovoltaic (PV) generation system. The performance of a PV array strongly depends on operating environmental conditions such as operating temperature, solar insolation, shading array configuration. Often PV arrays get shadowed fully or partially by passing cloud, building, poles, trees, etc. Under such partial shading conditions, the operation of PV arrays get more complicated with more than one peak and it is very important to predict the characteristics to obtain possible maximum power. Furthermore, the mismatch losses and hotspot effects caused by partially shading cannot only affect the output power of solar system also can bring security and reliability problem. However, it is quite expensive and takes much time to get operating output characteristics of PV arrays under non uniform working conditions. Therefore, it is necessary to have a simulation model to study the effect of partial shading on solar PV arrays’ working characteristics. A 100 W solar panel is used as reference. The study also focuses on position of output peak power with varying location of shaded modules, different levels of solar irradiation as well as role of bypass diodes in this system. The I–V and P–V output curves of the solar PV arrays under partially shading conditions are given. The simulation results indicate that the higher number of shaded solar modules is, the lower value of power output is and the position of maximum power point does not depend on location of modules under shadow. The paper provides an easy method to study the response of solar PV arrays under non uniform working conditions: partial shadow. In addition, the following points were also investigated:

Communicating the uncertainty in estimated greenhouse gas emissions from agriculture

In an effort to mitigate anthropogenic effects on the global climate system, industrialised countries are required to quantify and report, for various economic sectors, the annual emissions of greenhouse gases from their several sources and the absorption of the same in different sinks. These estimates are uncertain, and this uncertainty must be communicated effectively, if government bodies, research scientists or members of the public are to draw sound conclusions. Our interest is in communicating the uncertainty in estimates of greenhouse gas emissions from agriculture to those who might directly use the results from the inventory. We tested six methods of communication. These were: a verbal scale using the IPCC calibrated phrases such as ‘likely’ and ‘very unlikely’; probabilities that emissions are within a defined range of values; confidence intervals for the expected value; histograms; box plots; and shaded arrays that depict the probability density of the uncertain quantity. In a formal trial we used these methods to communicate uncertainty about four specific inferences about greenhouse gas emissions in the UK. Sixty four individuals who use results from the greenhouse gas inventory professionally participated in the trial, and we tested how effectively the uncertainty about these inferences was communicated by means of a questionnaire. Our results showed differences in the efficacy of the methods of communication, and interactions with the nature of the target audience. We found that, although the verbal scale was thought to be a good method of communication it did not convey enough information and was open to misinterpretation. Shaded arrays were similarly criticised for being open to misinterpretation, but proved to give the best impression of uncertainty when participants were asked to interpret results from the greenhouse gas inventory. Box plots were most favoured by our participants largely because they were particularly favoured by those who worked in research or had a stronger mathematical background. We propose a combination of methods should be used to convey uncertainty in emissions and that this combination should be tailored to the professional group.

Characterization of Power Optimizer Potential to Increase Energy Capture in Photovoltaic Systems Operating Under Nonuniform Conditions

Power optimizers, which perform power conversion and distributed maximum power point tracking (DMPPT) at the subarray level, are available to mitigate losses associated with nonuniform operating conditions in grid-tied photovoltaic (PV) arrays, yet there is not a good understanding of their potential to increase energy capture. This paper develops and demonstrates a methodology for the use of a detailed software tool that can accurately model both partial shading and electrical mismatch at the subpanel level in a PV array. Annual simulations are run to examine the device-independent opportunity for power recovery in arrays with light, moderate, and heavy shading, and subpanel electrical mismatch variations based on measurements from a monocrystalline silicon array. It is found that in unshaded arrays, the potential energy gain is <; 1% using power optimizers, but in shaded arrays it increases to 3-16% for panel-level DMPPT and 7-30% for cell-level DMPPT. In the set of simulated cases, panel-level power optimization recovers 34-42% of the energy that is lost to partial shading.

Modeling of the photovoltaic cell circuit parameters for optimum connection model and real-time emulator with partial shadow conditions

Photovoltaic (PV) power has been successfully used for over five decades. The output characteristics of a PV array vary nonlinearly when temperature or irradiance conditions change. At the beginning of this paper, the performance of PV panel is analyzed, for parallel and series connections of solar cell elements exposed to the same light conditions and temperature by using the Brune’s conditions of interconnection. Therefore the parameters of the equivalent circuits for each typical PV cell connections are characterized by a new set of matrix equations. A Lab View application is implemented to prove the theoretical models. Moreover, the grid connected PV systems have become more popular because they do not need battery back-ups to ensure maximum power point tracking (MPPT). However, partial shading is one of the main causes that reduces energy yield of PV array. In this respect, the second part of the paper refers to the influences of different irradiance conditions on the PV array performance in order to achieve MPPT under shaded array conditions. Consequently, PV array emulator is crucial for the operational evaluation of system components. The purpose of this study extension is to design and develop a new real-time emulator of PV array output characteristics based on closed-loop reference model.

Analysis and control of mismatch power loss in photovoltaic arrays

AbstractConnecting photovoltaic cells to form an array can cause problems when the characteristics of the cells are not matched. This problem, known as mismatch, can reduce the power output of the array and lead to cell degradation through localized heating of individual cells. Such problems can arise simply through the shading of a single cell. In this paper, which has a substantial tutorial content, three methods of reducing the effects of mismatch are investigated and compared; the use of integral bypass diodes (IBDs), series/paralleled circuit designs and reduced cell shunt resistance.Experiments were performed on arrays incorporating cells with IBDs and their tolerance to shading was tested and compared to arrays with other cell designs. the potential benefits and costs of using IBDs are then assessed and conclusions drawn about the relative effectiveness of this strategy. the circuit design strategy known as series/paralleling is described and analysed and its effect on minimizing mismatch power loss is evaluated. Also, an expression for the optimum cell shunt resistance in a general shaded array is derived and the technique of reducing cell shunt resistance to minimize mismatch effects is assessed.

Passive ranging with focusing beamformers and shaded arrays

We consider focused beamforming using passive arrays as a means of achieving rapid range solutions and demonstrate that a new class of geometry‐dependent amplitude shading distributions can improve range resolution. The distribution is determined by treating the array as if it were a set of samples distributed in a hypothetical curved wave front originating from the array focus and by projecting the hydrophone coordinates onto the spherical surface along radii emanating from the focus. We define a continuous shading distribution on this surface to assign weights to each hydrophone input and divide the shading distribution by the wave front sample density. This technique is called “wave front sample density compensated (WSDC) shading.” Simulated performance is presented for a large surveillance towed array with a target whose signature contains a characteristic tonal and is located broadside to the array. A comparison among unit shading, a simple element placement scheme, and the WSDC method shows that, although there is some loss in gain, the focused beamforming method with the WSDC shading provides greater resolution and computational speed and lower side‐lobe levels than the other methods. [Work supported by ONR.]

Near Field of a Shaded Radiator

The near field of a bizonally shaded rectangular transducer is investigated theoretically and experimentally. The theoretical radiation integral is solved first for a shaded piston using Fresnel integrals. The radiation from a shaded array of pulsating spheres is also solved exactly. Both theoretical directivity patterns are determined for a certain transducer at various near field separations using the Datatron 220 digital computer. Experimental results are also given for the transducer. Excellent agreement between theory and experiment to very short ranges is obtained.