Browsing by Author "Ramesh, D."

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    A novel reduced-cross-tied configuration for extracting maximum power output from a symmetrical PV array under partial shading conditions
    (Springer Science and Business Media Deutschland GmbH, 2024) Ramesh, D.; Karthikeyan, A.; Gaonkar, D.N.
    The primary reason for the decrease in power output from the PV array is partial shading. During partial shading conditions (PSCs) PV modules experience a mismatch in current and voltage generated. Also, the power voltage (P–V) characteristics of the PV array possess multiple peaks under PSCs. To mitigate the effects caused by PSCs, the configuration of the PV array is the finest solution. This paper proposes a novel Reduced Cross Tied (RCT) configuration to enhance maximum power output from a symmetrical PV array under PSCs. The RCT configuration has fewer cross-ties compared to the TCT configuration and is applicable to a square array of any size. The proposed RCT configuration along with conventional configurations such as Total Cross Tied (TCT), Series–Parallel, Bridge-Link, and Honey-Comb are validated in simulation and hardware for 7×7 and 8×8 symmetrical PV arrays under Short and Narrow (SN), Short and Wide (SW), Long and Narrow (LN) and Long and Wide (LW) shading patterns. A comparative analysis is done between the proposed configuration and conventional configurations in terms of mismatch loss (ML), fill factor, efficiency (η), Wiring Loss, and Global Maximum PowerPoint (GMPP). The proposed RCT configuration is able to achieve GMPP equal to the TCT configuration under the LN shading pattern and on par with the TCT configuration under SN, SW, and LW shading patterns. RCT-configured PV array possesses a minimum reduction of 25% in wiring loss for any array size. RCT configuration applies to a square array of any size.The results replicate the efficacy of the proposed RCT configuration compared to existing configurations. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.
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    A Workflow Scheduling Approach With Modified Fuzzy Adaptive Genetic Algorithm in IaaS Clouds
    (Institute of Electrical and Electronics Engineers Inc., 2023) Rizvi, N.; Ramesh, D.; Wang, L.; Annappa, B.
    The emergence of the cloud platform with substantial resources to offer on-demand instigated the researchers to migrate the scientific workflows to the cloud environment. The scheduling of workflows with diverse QoS parameters is not a trivial task, but an NP-Complete problem. Several heuristics for QoS constrained workflows have been investigated. However, most of them focus only on time and cost and do not guarantee high resource utilization. The scheduling of the workflow tasks over the minimum cloud resources under the defined time limit is a grave concern. In this article, an algorithm named MFGA (Modified Fuzzy Adaptive Genetic Algorithm) has been formulated to minimize the makespan and improve resource utilization under both deadline and budget constraints. A fuzzy logic controller has also been devised to control the crossover and mutation rates that prevent MFGA from getting stuck in a local optimum. MFGA has a novel crossover technique that adds the fittest solutions in the population. Additionally, a new mutation technique has also been introduced, which minimizes the makespan and increases the reusability of the resources. The simulation experiments with the real workflows show that the proposed MFGA outperforms other state-of-the-art algorithms. © 2008-2012 IEEE.
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    Cyclic back shift method for maximizing PV array power under partial shading
    (Springer Science and Business Media Deutschland GmbH, 2025) Ramesh, D.; Karthikeyan, K.
    Partial shading leads to reduction in power output and efficiency of photovoltaic (PV) systems. The physical arrangement of PV modules without changing electrical circuitry plays vital role in reducing the effects caused by partial shading. This paper presents a cyclic back shift (CBS) method to enhance the PV power under partial shading conditions (PSCs). In this method, relocation of modules is based on row positions of modules in a particular column. The proposed CBS method is cost-effective, simple and applicable for both square and non-square array. The proposed CBS method is implemented on 9×9 PV array and tested in both software (20.25 kW system) and hardware (0.81 kW system) environments under various shading patterns. The performance parameters such as fill factor (FF), mismatch loss (ML) and efficiency (?) are plotted. Further, a comparative analysis is carried between the proposed CBS method, total cross tied (TCT) and different existing reconfiguration schemes. From the experimental results, it is observed that the proposed CBS method is able to enhance the GMPP by minimum 11.83% under shading pattern-II and maximum of 18.78 under shading pattern-III compared to TCT configuration. Hence, the CBS method of module arrangement is an effective solution in reducing the partial shading effects. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
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    Modified Odd–Even–Prime pattern for effective dispersion of shade over the PV array under partial shading conditions
    (Elsevier Ltd, 2024) Ramesh, D.; Karthikeyan, A.
    Photovoltaic (PV) arrays are extensively used for power generation being the most abundant renewable energy sources available. Partial shading of the PV array leads to mismatch between the modules and decrease in output power. A new Modified Odd–Even–Prime (MOEP) method of module arrangement for total cross tied (TCT) connection is presented in this paper to mitigate the effects of partial shading. The proposed MOEP method is a physical relocation method where the modules of PV array are relocated without altering the electrical connections. MOEP method of module rearrangement is based on row positions of the PV array. In this method, the row positions of PV modules in the first column are filled with odd, even and prime numbers in ascending order. The row positions of further columns are formed based on MOEP method. The proposed MOEP method is implemented on 9 × 9 and 8 × 8 PV arrays under various shading patterns. Further, the results are compared with TCT, Odd Even (OE) and Odd–Even–Prime (OEP) patterns. MATLAB/Simulink is used to validate the results. An experimental setup of 9 × 9 and 8 × 8 PV array is developed and tested in real time environment to validate the effectiveness of MOEP method over TCT, OE and OEP methods. The performance of proposed MOEP method is evaluated in terms of GMPP, mismatch power loss (MPL), Fill Factor (FF), Efficiency (η) and Shade Dispersion Ratio (SDR). A detailed study on energy savings from the proposed MOEP method is made on hourly, daily and yearly basis. From the experimental results obtained, it is observed that MOEP method generates a significant improvement in GMPP, efficiency and reduces the mismatch loss compared to TCT, OE and OEP methods. © 2024 International Solar Energy Society