Shaded Modules Research Articles

Reconfiguration and Analysis of PV Array based on Particle Swarm Optimization of Solar Plant

Abstract The major shortcoming in the extraction of electrical energy occurs due to partial shading over a limited area of vast spread solar panels underpinning reduction of efficiency. A number of panels are interconnected in series and parallel to form a photovoltaic (PV) array for large power plants and a shadow over a single cell deteriorates overall performance. As a consequence, several peaks are added to the P-V curve causing hotspots in PV panels, degradation of the PV system, and collapse of tracking algorithms. In order to minimize such issues in PV panels, an effective optimization technique is developed by reconfiguring the panels which are capable of reaching the full global power point in a PV system under partial shading conditions. The study proposes particle swarm optimization (PSO) using PV characteristics of Quaid-e-Azam Solar Plant (QASP) in Punjab, Pakistan1. In PSO, electrical connections of PV modules are changed keeping their physical locations unaltered aiming to improve the performance of the PV system. After reconfiguration, the algorithm finds the best combination of PV modules by equalizing the row currents followed by the comparison of row current, voltages, and power of panels. The proposed PSO is proved to be an efficient method for reconfiguring PV modules in very less computational time by increasing the output power of shaded modules.

A novel PV array reconfiguration approach to mitigate non-uniform irradiation effect

The extraction of power at global maximum power point (GMPP) has been affected due to non-uniform row-current generation leading to the formation of multiple peaks in power-voltage (P-V) curve. This issue booms out due to set of factors referred to as partial shading condition (PSC). To root-out this issue, puzzle-game based strategies were developed based on physical relocation of shaded modules with the unshaded one. This has a limitation when considering the size as a parameter which is non-effective for larger shade-dispersion. Thus, to alleviate this issue, this research paper intends to execute a novel reconfiguration topology based on idea of permutation and combination (P-C). This novel metaheuristic approach is focussed on building a fitness function in terms of efficiency (Ƞ), fill-factor (FF) and power loss (PLOSS). A connection list has been prepared to evaluate for optimal combination of solar modules. Hence, this approach excels in providing an optimum solar array attenuating the complexity of the photovoltaic (PV) system. The effectiveness of this approach has been validated through MATLAB tool on 4 × 4, 6 × 4 and 9 × 9 solar array size under various shading patterns. To bring out more efficacy, this suggested novel approach has been elaborately compared with traditional Total cross tied (TCT) topology and two other puzzle-based topology Ken-Ken (K-K) and L-shape (L-S) topology for 4 × 4 solar array size on the basis of 16 performance parameters; maximum voltage (VMAX), maximum current (IMAX), GMPP, local maximum power point (LMPP; its values and number of peaks generated on the P-V curve), misleading power loss (MLPL), mismatch loss (MLOSS), current and voltage loss (ILOSS, VLOSS), PLOSS, execution ratio (ER), Ƞ, FF, %power improvement (%PI), thermal voltage (TV) and power enhancement ratio (PER). Results for 4 × 4 solar array size portray that P-C has enhanced GMPP by 5.64 W, 5.64 W and 6.61 W reducing PLOSS by 7%, 6% and 8.26% respectively over L-S, K-K and TCT under border shading. Validation of the novel P-C for 6 × 4 solar array size has been done with TCT and L-S. Its results conclude that GMPP of P-C is incremented by 12.99 W and 0.70 W reducing the PLOSS by 11.16% and 0.99% respectively over TCT and L-S under corner shading. Further, the novel P-C for 9 × 9 solar array size has been validated with TCT, K-K, L-S, Ancient Chinese (A-C) and Skyscraper (S-S) topologies. GMPP of the novel P-C is improved by 16.19 W, 12.34 W, 12.34 W, 12.11 W and 2.75 W minimizing the PLOSS by 5.80%, 5.75%, 5.75%, 5.73% and 4.23% over TCT, K-K, L-S, A-C and S-S under zigzag shading. The comparative results under all the three considered solar array size strongly suggests the increased ability of the proposed novel P-C approach in enhancing the performance parameters and an effective shade dispersion over the entire PV array under PSC as compared to other considered reconfigurations.

Global Maximum Power Point Tracking of Photovoltaic Module Arrays Based on Improved Artificial Bee Colony Algorithm

In this paper, an improved artificial bee colony (I-ABC) algorithm for the maximum power point tracking (MPPT) of a photovoltaic module array (PVMA) is presented. Even though the P-V output characteristic curve with multi-peak was generated due to any damages or shading discovered on the PVMA, the I-ABC algorithm could get rid of stuck on tracking the local maximum power point (LMPP), but quickly and stably track the global maximum power point (GMPP), thereby improving the power generation efficiency. This proposed I-ABC algorithm could search for the higher power point of a PVMA by a small bee colony, determine the next tracking direction through the perturb and observe (P&O) method, and keep tracking until the GMPP is obtained. This method could prevent tracking the GMPP for too long due to applying a small bee colony. First, in this study, the photovoltaic modules produced by Sunworld Co., Ltd. were used and were configured as a PVMA with four series and three parallel connections under different numbers of shaded modules and different shading ratios, so that corresponding P-V output characteristic curves with multi-peak values were generated. Then, the GMPP was tracked by the proposed MPPT method. The simulation and experimental results showed that the proposed method performed better both in dynamic response and steady-state performance than the traditional artificial bee colony (ABC) algorithm. According to the experimental results, it showed that the tracking accuracy for the GMPP based on the proposed MPPT with 100 iterations under 5 different shading ratios was about 100%; on the other hand, that of the traditional ABC algorithm was 70%, and that of the P&O method was lower at about 30%.

Power recovery of the PV arrays under partial shading by a power electronic compensator

The partial shading phenomenon in some modules of the PV arrays limits the total current of the series modules and reduces the total output power. In this paper, a power electronic compensator with a multi-winding transformer is presented to recover the undelivered energy of the shaded modules. The proposed configuration compensates reduced currents due to the partial shading on the series modules by injecting the required currents into parallel circuits of the shaded modules. The unshaded modules provide the compensatory currents by creating a common flux into the core of the multi-winding transformer. The average current and the output power of the PV array are considerably improved under partial shading conditions. The proposed configuration has a very simple and sensorless control structure, and its power electronic elements are less than other improving configurations. The simulation and experimental results confirm the presented analytical relations and desirable performance of the proposed configuration to recover the undelivered energy of the PV array under the partial shading conditions.

Non-Symmetrical (NS) Reconfiguration Techniques to Enhance Power Generation Capability of Solar PV System

At present, primary power generation depends on non-renewable energy resources, which will become extinct. Solar is the best option in renewable energy sources to achieve clean and green power extraction. Solar PV transforms light energy into electrical energy. However, the output power of solar PV changes with solar insolation. It is also affected by environmental factors and the shading effect. One of the key factors that can reduce the PV system output power is partial shading condition (PSC). The reduction in power output not only depends on shaded region but also depends on pattern of shading and physical position of shaded modules in the array. Due to PSCs, mismatch losses are induced between the shaded modules which can cause several peaks in the output power-voltage (P-V) characteristic. This article describes the non-symmetrical reconfiguration technique and compares it with the primary total cross tied connection. The performance of non-symmetrical reconfiguration techniques is evaluated and compared in terms of global maximum power (GMP), voltage and currents at GMP, open and short circuit voltage and currents, mismatch power loss (MPL), fill factor, efficiency, and number of local maximum power peaks (LMPPs) on a 9 × 9 PV array.

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.

Comparative Study of the Effect of Shading Rate on the Electrical Parameters of CIGS and CdTe/CdS Solar Modules

In this paper, a comparative study of the maximum power on the shading rate on the maximum power of thin film PV modules. Thus two thin film PV modules of type Copper indium gallium selenide, CIGS, of 90W power and a CdTe (Cadmium telluride)/CdS (Cadmium sulfide) module, of maximum power 75 W. These modules, reference SN-CIGS90 and CX3 75 were tested under the conditions of the installation site to ensure their proper functioning and to determine the initial values of electrical parameters before shading. The results obtained are as follows: for the CIGS: Pm (80.717 W); Vco (23.06 V), Icc (3.5 A) and for the CdTe:Pm (54.914 W); Vco (35.52 V), Icc (1.546 A). After this characterization test, the modules are exposed to real operating conditions at the Center for Study and Research on the renewable energy (CERER), Cheikh Anta Diop University in Dakar. Four types of shading are performed on each module with the same mask: partial shading at 25%, 50%, 75% and complete shading at 100%. The comparison of the variation rates obtained on the experimental values of the 4 types of shading carried out on each module, shows that, the phenomenon of shading constitutes an environmental factor which influences negatively the maximum power of the thin film PV modules. But this reduction depends on the surface of the shaded module, the nature of the mask but also the technology used. Indeed, for a shading of 25% of the surface of the two modules, we note a reduction of 21.32% of power for the CIGS, against 40.53% for the CdTe/CdS, that is to say a difference which approaches 20%.

Investigation into the impacts of design, installation, operation and maintenance issues on performance and degradation of installed solar photovoltaic (PV) systems

Poor performance and high degradation of photovoltaic (PV) systems reduce the expected power generation and shorten the lifetime of the systems. This study highlighted the design, installation, operation and maintenance issues, and their impacts on the performance and degradation of installed PV systems. The study covered 16 installed PV systems in different climatic zones in Ghana, comprising 104 PV modules of different technologies and ages. Interviews, observation and current-voltage (I-V) curve tracing were used. The results of the study revealed that the installers disregarded the PV system design procedures, leading to undersized systems against the desire demand discussed and agreed on between the owners and installers, and systems whose PV panel capacities exceeded that of the batteries. Consequently, 69% of the systems were improperly sized, resulting in lower power output than expected and failure of some systems. The median power degradation rates were 1.94%/year and 1.34%/year for the shaded and unshaded modules respectively. Four systems had been abandoned while two were partially functioning due to malfunctioning of batteries, inverters and charge controllers, resulting from the use of low-quality components and over-discharged of the batteries due to persistent use of these systems with faulty charge controllers. More than 70% of the systems were installed without easy access to the panels for inspection and cleaning. Consequently, these modules degraded faster than the frequently cleaned modules. The 37.5% of the systems subjected to preventive maintenance degraded at 1.38%/year while the remaining 62.5% subjected to responsive maintenance (maintained only when problems occurred) degraded at 1.61%/year. The disregard of proper procedures by the installers led to undersized systems, panel-battery mismatch and improper installation which resulted in low power output than promised by the installers. The improper operation and maintenance practices such as overloading of systems with inappropriate appliances, over-discharging of batteries, panel shading and lack of regular cleaning resulted in low power output, high degradation rates and components breakdown. The dissatisfaction with the systems performance discouraged the system owners from replacing defective components, leading to abandonment of some of the systems.

A novel prime numbers-based PV array reconfiguration solution to produce maximum energy under partial shade conditions

Non-uniform solar irradiance on the photovoltaic arrays decreases the output power due to the partial shading conditions. In this paper, the distribution of shade in the photovoltaic array rows is done by reconfiguring the shaded modules related to the photovoltaic array. The method proposed in this paper is a static approach based on prime numbers. Due to the pattern of prime numbers, it reconfigures the shaded modules in each row. The effectiveness of the proposed procedure is done by testing five different shading patterns in 9×9 and one 23×23 Total-Cross-Tied PV arrays. The ability and superiority of the proposed method are tested by comparing the results of the suggested method of prime numbers with the results of the Total-Cross-Tied, Sudoku, optimal Sudoku, improved Sudoku, and Dominance square methods. Comparison and evaluation of the results are done by different statistical performance indicators. The evaluations showed that the prime numbers procedure with the values of 9.15%, 7.72%, 8.21%, 8.83%, 8.95%, and 8.77% for cases 1 to 6, respectively, had the highest power factor compared to other methods employed. In addition, the suggested method has the lowest mismatch power losses compared to other procedures by achieving the values of 3.84%, 4.87%, 4.53%, 4.10%, 3.97%, and 4.19% in cases 1–6, respectively. The results of the comparisons strongly emphasize the high ability of the proposed method compared to other methods studied. It should be noted that scalability, high-performance speed, and low cost are important advantages of the prime number method so that this method can be implemented on real-world PV arrays.

Investigation of the major internal and external factors that affect photovoltaic modules energy production and systems performance

Photovoltaic conversion is an optimal solution for the electrification of rural areas, especially deserts for the abundance of solar energy in these regions. In recent years, many studies have been carried out to maximize the energy productivity of a PV array system and increase its efficiency. However, the arid and semi-arid region is characterized by a climate whose parameters significantly influence the operation of PV installations. This paper presents an overview investigation of the major internal and external factors significantly affecting both the efficiency and the performance of solar cells and the power of PV systems. These factors include the type of PV material, solar radiation intensity received, cell temperature, parasitic resistances, cloud, and other shading effects, inverter efficiency, dust, module orientation, weather conditions, geographical location, and cable thickness. Simulation of a PV system has been carried out in MATLAB-SIMULINK to prove the effectiveness of the proposed modeling method. These simulation results are useful to predict the production of the PV module under real operating conditions.

A new methodology for the assessing of power losses in partially shaded SPV arrays

This paper describes a novel methodology for estimating the shading factor and the irradiance in partially shaded photovoltaic arrays. The results indicate that the monitoring of short circuit currents obtained from the IV curves of shaded and unshaded modules can be used to calculate the overall irradiance on partially shaded and not shaded photovoltaic arrays. This new methodology avoids the need to use several irradiance sensors to map the shaded and unshaded regions. Besides that, this paper presents a simple mathematical model to estimate shading losses on SPV arrays at the points of maximum global and local power. The methodology can be described in five steps: the measurement of the IV curve and cell temperature, pre-processing of the IV curve, calculation of the shading factor and irradiance on the shaded and unshaded areas, use of the photovoltaic array model to obtain the simulated IV curve and the shading level distribution in the array. The proposed model was developed using the methodology presented in this work, demonstrating how useful it can be to validate and develop models applied to evaluate the shading effects. Calculated losses are compared to those obtained with models found in the literature. The proposed model is useful for calculating the instantaneous power losses, requiring less information as input than other detailed models, and requiring low computational effort.

Switching Matrix Enabled Optimal Topology Reconfiguration for Maximizing Power Generation in Series–Parallel Organized Photovoltaic Systems

Mismatch losses (ML) problem can directly reduce the power generation of a photovoltaic (PV) array as well as complicate maximum power point tracking (MPPT) algorithms by causing multiple peaks to appear in the P-V characteristic. Hence, PV array reconfiguration techniques have become highly popular to minimize the ML of PV arrays. In this article, an optimal dynamic topology reconfiguration method based on a switching matrix is presented for series–parallel (SP) interconnected PV array to mitigate the ML, thereby maximizing the power generation of the PV array. The design of the switching matrix is presented that enables each string of the PV array to be divided into two sections to carry out the efficient dynamic topology reconfiguration with improved flexibility and scalability. The proposed reconfiguration method is assessed and compared with the SP scheme and the recently developed cross diagonal view method. The effectiveness of the proposed solution for the TCT scheme is also confirmed through simulation experiments. The numerical results indicate that the multiple peaks on P-V curves can be reduced and MPPT can be implemented with a simple control algorithm. Additionally, the maximum power generation improved by 20.13% and 14.39% on average compared to the SP scheme and TCT scheme, respectively, for different mismatch conditions of partial shading and random PV module failures.

Enhance the Output Power of a Shaded Solar Photovoltaic Arrays with Shade Dispersion based TCT Configuration

Partial shading has a negative impact on the performance parameters of a Solar Photovoltaic (PV) array, because it shades certain panels while leaving others un-shaded. This article focuses on modeling, comparing and performance assessment of 6×6, 6×5 and 5×6 size shadowed solar PV arrays under different partial shading cases in the MATLAB/ Simulink software. For this purpose, the simulation of series-parallel (SP), Total-Cross-Tied (TCT) and proposed shade dispersion based TCT (SD-TCT) type of array configurations was carried out under few shading cases. The proposed SD-TCT was designed using the shades dispersion technique, which is based on a number logic approach. In this technique, in order to effectively remove the row-current mismatches in the TCT PV array configuration, the shaded and un-shaded modules in an array were re-arranged, so that the shading on modules expands across the whole array. The physical placement of the TCT array modules has been reordered in accordance with the proposed number logic pattern exclusive of altering the electrical links among the panels. The simulation results showed that the performance of the SD-TCT type was superior to that of conventional array configurations.

Optimal carbon partitioning helps reconcile the apparent divergence between optimal and observed canopy profiles of photosynthetic capacity.

Photosynthetic capacity per unit irradiance is greater, and the marginal carbon revenue of water (∂A/∂E) is smaller, in shaded leaves than sunlit leaves, apparently contradicting optimization theory. I tested the hypothesis that these patterns arise from optimal carbon partitioning subject to biophysical constraints on leaf water potential. In a whole plant model with two canopy modules, I adjusted carbon partitioning, nitrogen partitioning and leaf water potential to maximize carbon profit or canopy photosynthesis, and recorded how gas exchange parameters compared between shaded and sunlit modules in the optimum. The model predicted that photosynthetic capacity per unit irradiance should be larger, and ∂A/∂E smaller, in shaded modules compared to sunlit modules. This was attributable partly to radiation-driven differences in evaporative demand, and partly to differences in hydraulic conductance arising from the need to balance marginal returns on stem carbon investment between modules. The model verified, however, that invariance in the marginal carbon revenue of N (∂A/∂N) is in fact optimal. The Cowan-Farquhar optimality solution (invariance of ∂A/∂E) does not apply to spatial variation within a canopy. The resulting variation in carbon-water economy explains differences in capacity per unit irradiance, reconciling optimization theory with observations.

Shading Module With Buckling as Driver for Shape Morphing

The recent requirements in construction for lower energy consumption have accelerated the trend towards the use of high performance buildings. In these Nearly Zero Energy Buildings (NZEB), simple measures such as natural light control are practiced for maximising the light intake and minimising the heat gain, as required. These modern building envelopes interact with the external environment and are designed to respond to occupant demand, achieving the target energy efficiency and comfort needs. In these kinetic facades, shape morphing triggered by buckling is targeted for energy-saving structural applications. Among the structural forms that are suitable for such applications are thin plates, which are prone to buckling under small in-plane strains. This study presents a novel concept with application in shading control modules. In the proposed models, buckling of slender plates are configured to create a bistable mechanism with closed and open states. The proposed mechanism is simulated using finite element software to validate the feasibility of the core concept and to evaluate buckling as a reliable mechanism in kinetic facade control modules.

Modeling of Photovoltaic Modules Under Common Shading Conditions

Common shading conditions will leads to power loss and even result in hotspots, which influence the reliability of PV systems. Therefore, it is necessary to model for PV modules under common shading conditions in the PV station. Modeling of the shaded module relies on the appropriate model for the (partial) shaded cell. We observe that shaded region and unshaded region in a PV cell work quite differently. In the shaded region, the photoinduced current will decrease, and the shunt resistance will increase. In the unshaded region, the temperature rise can be even higher than 100 ℃. Consequently, it is essential to model for the shaded region and unshaded region respectively. In this paper, a physically explicable parallel model is proposed for the shaded cell and modeling of PV modules under common shading conditions are studied. We conduct extensive experiments, shading PV modules by area-measurable shade cloth with regular shape to analyze their I-V characteristics. PV modules are also shaded by uniformly accumulated dust, and leaf / soil / shadow with arbitrary shape and location to simulate the situation in real PV station. Experimental results verify the effectiveness of our method.

Numerical simulation and verification of adaptive shading modules with buckling as the driver for functionality

In conventional design paradigm, buckling of slender structural members is seen as a route toward failure and measures are taken to avoid its onset. In recent years, a new challenging approach is emerging where the mechanical instability of slender elements is utilised to achieve novel modes of functionality. Adapting such framework, the flexural-torsional buckling of frame geometries can be exploited as driver to change the shape of slender structural frames to fulfil specific function of shading. This study is concerned with numerical simulation of novel developed systems in which outof-plane buckling of members of a frame is judiciously harnessed to construct adaptive shading modules. Advanced numerical simulations are conducted using Abaqus software to gain better understanding of the factors that affect the behaviour and performance of the proposed solutions. Building on the gained insight a comprehensive search strategy is devised for finding optimum solutions for the governing material, geometrical, and actuation parameters. Within the constructed search space, nonlinear buckling analyses are carried out to determine the resultant shading area, and to quantify the influence of the governing parameters.

Improved performance of partially shaded photovoltaic array with reformed-total cross tied configuration

Abstract Renewable energy sources are receiving wide popularity due to the shortage of fossil fuels and environmental problems caused by conventional energy sources. Solar photovoltaic energy is a widely used sustainable energy source. The power developed by a solar cell is greatly influenced by the insolation level. Partial shading occurs when one or more photovoltaic (PV) cells receive lesser radiation as compared to other cells, which in turn affects the overall electrical performance of PV cells including reduced generated power. This paper proposes a newly developed configuration known as Reformed-Total cross-tied (R-TCT) to improve the power generation during partially shaded conditions in small-scale PV systems, especially for urban and rural area applications. The basic idea of this paper is to redistribute the shaded modules of a row to other rows such that the number of shaded solar PV modules of each row are nearly same. The proposed method is validated by simulation and also by hardware implementation. The simulations and experiments are done on eight different shading cases and found that the proposed method gives either superior or same performance as that of existing TCT, LS (Latin Square)-TCT, and D-TCT configurations.

Shading fault detection in a grid-connected PV system using vertices principal component analysis

Partial shading severely impacts the performance of the photovoltaic (PV) system by causing power losses and creating hotspots across the shaded cells or modules. Proper detection of shading faults serves not only in harvesting the desired power from the PV system, which helps to make solar power a reliable renewable source, but also helps promote solar versus other fossil fuel electricity-generation options that prevent making climate change targets (e.g. 2015’s Paris Agreement) achievable. This work focuses primarily on detecting partial shading faults using the vertices principal component analysis (VPCA), a data-driven method that combines the simplicity of its linear model and the ability to consider the uncertainties of the different measurements of a PV system in an interval format. Data from a grid-connected monocrystalline PV array, installed on the rooftop of the Power Electronics and Renewable Energy Research Laboratory (PEARL), University of Malaya, Malaysia, have been used to train the VPCA model. To prove the effectiveness of this VPCA method, four partial shading patterns have been created. The obtained performance has, then, been tested against a regular PCA. In addition to its ability to acknowledge the uncertainty of a PV system, the VPCA method has shown an enhanced performance of detecting partial shading fault in comparison with the standard PCA. Also, included in the article is an extension of the contribution plot diagnosis-based method, of the Q-statistic, to the interval-valued case aiming to pinpoint the out-of-control variables.

Enhanced performance of partially shaded photovoltaic arrays using diagonally dispersed total cross tied configuration

ABSTRACT Partial shading on photovoltaic (PV) systems causes a reduction in generated power and multiple peaks on their electrical characteristics. These adverse effects depend on the types of interconnection between modules and the intensity of insolation. This paper proposes a new configuration of PV modules, known as Diagonally dispersed Total Cross Tied (D-TCT), to achieve an enhanced performance under partial shading conditions. The unequal distribution of the shaded modules in various rows of TCT configuration produces greater power loss and more number of peaks in the electrical characteristics. The basic idea of this method is to disperse shaded modules to various rows such that an approximate-balanced distribution of shaded modules is possible for almost all practical shading patterns resulting in the enhanced performance. The performance of D-TCT is analyzed and compared with existing TCT and odd-even configurations and is found that the proposed method gives better performance over the existing methods. An experimental study is also carried out using 16 number of 20 W solar panels connected in 44 arrays and it is observed that the proposed method gives an enhanced power of and as compared to TCT configuration for various shading patterns.