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Chilakapati Nagamani

Bio: Chilakapati Nagamani is an academic researcher from National Institute of Technology, Tiruchirappalli. The author has contributed to research in topics: AC power & Stator. The author has an hindex of 19, co-authored 100 publications receiving 1633 citations. Previous affiliations of Chilakapati Nagamani include Central Power Research Institute & Indian Institute of Technology Kanpur.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the physical location of the modules in a total cross-tied (TCT) connected PV array is arranged based on the Su Do Ku puzzle pattern so as to distribute the shading effect over the entire array.
Abstract: Partial shading of PV arrays reduces the energy yield of PV systems and the arrays exhibit multiple peaks in the P-V characteristics. The losses due to partial shading are not proportional to the shaded area but depend on the shading pattern, array configuration and the physical location of shaded modules in the array. This paper presents a technique to configure the modules in the array so as to enhance the generated power from the array under partial shading conditions. In this approach, the physical location of the modules in a Total Cross Tied (TCT) connected PV array are arranged based on the Su Do Ku puzzle pattern so as to distribute the shading effect over the entire array. Further, this arrangement of modules is done without altering the electrical connection of the modules in the array. The Su Do Ku arrangement reduces the effect of shading of modules in any row thereby enhancing the generated PV power. The performance of the system is investigated for different shading patterns and the results show that positioning the modules of the array according to “Su Do Ku” puzzle pattern yields improved performance under partially shaded conditions.

390 citations

Journal ArticleDOI
TL;DR: In this article, the suitability of using a normal three-phase induction motor as a capacitor self-excited induction generator (SEIG) is illustrated, and the thermal limit of the stator windings being the limiting factor, the capacity of the SEIG is determined.
Abstract: The suitability of using a normal three-phase induction motor as a capacitor self-excited induction generator (SEIG) is illustrated. The thermal limit of the stator windings being the limiting factor, the capacity of the SEIG is determined. The steady-state performance of such induction generators, maintaining a constant terminal voltage, is analyzed under resistive and reaction loads. Typical experimental results are also presented. It was found that, for low power motors, the maximum power that can be extracted as generators is 148% to 160% of the motor rating for resistive loads and 118% to 128% of the motor rating for 0.8 lagging power factor loads. Capacitive reactive volt-ampere (VAR) required to maintain constant voltage at 1.0 p.u. speed is in the range 85% to 140% of the power rating of the motor with resistive loads and 100% to 140% with lagging reactive loads. >

153 citations

Journal ArticleDOI
TL;DR: A fixed interconnection scheme for PV arrays that enhances the PV power under different shading conditions and facilitates distribution of the effect of shading over the entire array thereby reducing the mismatch losses caused by partial shading is presented.
Abstract: A major challenge in photovoltaic (PV) systems is making them energy efficient. One of the major factors that contribute to the reduction of PV power is partial shading. The reduction in power depends on module interconnection scheme and shading pattern. Different interconnection schemes are used to reduce the losses caused by partial shading. This paper presents a fixed interconnection scheme for PV arrays that enhances the PV power under different shading conditions. The proposed scheme facilitates distribution of the effect of shading over the entire array thereby reducing the mismatch losses caused by partial shading. The performance of the system is investigated for different shading conditions and the MATLAB/SIMULINK results are presented to show that the power extracted from the PV arrays under partial shading conditions is improved. Experimental results are provided to validate the proposed approach using a laboratory experimental setup. A comparison is also made between the electrical array reconfiguration scheme and the proposed scheme for a 5 × 5 PV array.

150 citations

Journal ArticleDOI
TL;DR: A new GMPPT technique combining the PSO and Perturb and Observe algorithms has been presented, and the effectiveness of the proposed algorithm in tracking the GMPP, both under uniform and nonuniform irradiance conditions, is demonstrated experimentally.
Abstract: Maximum power point tracking (MPPT) is essential for photovoltaic (PV) string inverter systems. Partially shaded PV strings with bypass diodes exhibit multiple peaks in the power–voltage characteristic. Under partial shading conditions, conventional algorithms get trapped in a local maximum power point, and fail to track the global MPP (GMPP). To overcome this problem, global search algorithms such as particle swarm optimization (PSO) have been proposed. However, these can cause excessive oscillations in the output power before converging onto the GMPP. In this paper, a new GMPPT technique combining the PSO and Perturb and Observe (P&O) algorithms has been presented. The P&O technique is used to track the MPP under uniform irradiance, and the same is used to detect the occurrence of partial shading. Only on the onset of partial shading conditions, PSO is employed. Furthermore, the search space of PSO is reduced by using a window-based search in order to reduce the power oscillations and convergence time. The effectiveness of the proposed algorithm in tracking the GMPP, both under uniform and nonuniform irradiance conditions, is demonstrated experimentally.

141 citations

Journal ArticleDOI
TL;DR: A method to detect faults and partial shading under all irradiation conditions using the measured values of array voltage, array current, and irradiance is proposed.
Abstract: Abnormal conditions such as faults and partial shading lead to a reduction in the maximum available power from a photovoltaic (PV) array. Thus, it is necessary to detect partial shading and faults in a PV array for improved system efficiency and reliability. Conventional protection devices fail to detect faults under cloudy and low irradiance conditions, leading to safety issues and fire hazards in the PV field. This paper proposes a method to detect faults and partial shading under all irradiation conditions using the measured values of array voltage, array current, and irradiance. The proposed method enables classification of the status of the PV array into three possible scenarios, viz., normal operating condition, partial shading, and fault. The proposed method is tested experimentally to verify its effectiveness under different irradiation conditions.

131 citations


Cited by
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Journal ArticleDOI
TL;DR: This paper presents an exhaustive review of three-phase improved power quality AC-DC converters configurations, control strategies, selection of components, comparative factors, recent trends, their suitability, and selection for specific applications.
Abstract: Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

1,691 citations

Journal ArticleDOI
TL;DR: A phase-locked loop (PLL) is a nonlinear negative feedback control system that synchronizes its output in frequency as well as in phase with its input PLLs are now widely used for the synchronization of power-electronics-based converters and also for monitoring and control purposes in different engineering fields as mentioned in this paper.
Abstract: A phase-locked loop (PLL) is a nonlinear negative-feedback control system that synchronizes its output in frequency as well as in phase with its input PLLs are now widely used for the synchronization of power-electronics-based converters and also for monitoring and control purposes in different engineering fields In recent years, there have been many attempts to design more advanced PLLs for three-phase applications The aim of this paper is to provide overviews of these attempts, which can be very useful for engineers and academic researchers

563 citations

Journal ArticleDOI
TL;DR: A comprehensive review of the approaches proposed and used by authors of many papers is conducted in this paper, which includes both the standalone hybrid renewable energy systems and the grid-connected hybrid renewable systems.
Abstract: Variability and intermittency are some of the main features that characterize renewable energy sources. Intermittency usually includes both predictable and unpredictable variations. The many drawbacks of intermittency of renewable sources can be overcome by considering some special design considerations. Integrating more than one renewable energy source and including backup sources and storage systems are among the few measures to overcome these drawbacks. These additional design considerations usually increase the overall cost of the renewable system. Furthermore, the presence of more than one energy supply/storage system requires the control of energy flow among the various sources. Therefore, optimizing the size of the components and adopting an energy management strategy (EMS) are essential to decreasing the cost of the system and limiting its negative effects. The energy management strategy is commonly integrated with optimization to ensure the continuity of load supply and to decrease the cost of energy production. Therefore, energy management is a term that collects all the systematic procedures to control and minimize the quantity and the cost of energy used to provide a certain application with its requirements. The energy management strategy usually depends on the type of energy system and its components. Various approaches and techniques have been used to develop a successful energy management strategy. In this paper, a comprehensive review of the approaches proposed and used by authors of many papers is conducted. These approaches include both the standalone hybrid renewable energy systems and the grid-connected hybrid renewable systems. More attention is focused on popularly used techniques to address the features of each system. The selected papers in this review cover the various configurations of the hybrid renewable energy systems for electric power generation only.

422 citations

01 Jan 1982
TL;DR: An analytical technique using the `Newton-Raphson' method is presented to identify the saturated magnetising reactance and the generated frequency of a self-excited induction generator for a given capacitance, speed and load.
Abstract: An analytical technique using the `Newton-Raphson' method is presented to identify the saturated magnetising reactance and the generated frequency of a self-excited induction generator for a given capacitance, speed and load. The technique is shown to be very efficient in analysing such systems under steady state. Computed results are compared with the experimentally obtained values on a laboratory machine, and a reasonable correlation has been observed. Effects of various system parameters on the steady-state performance have been studied, and the results presented provide guidelines for optimum design of such systems.

368 citations

Journal ArticleDOI
TL;DR: A novel overall distribution MPPT algorithm to rapidly search the area near the global maximum power points, which is further integrated with the particle swarm optimization (PSO) MPPT algorithms to improve the accuracy of MPPT.
Abstract: Solar photovoltaic (PV) systems under partial shading conditions (PSCs) have a nonmonotonic P – V characteristic with multiple local maximum power points, which makes the existing maximum power point tracking (MPPT) algorithms unsatisfactory performance for global MPPT, if not invalid. This paper proposes a novel overall distribution (OD) MPPT algorithm to rapidly search the area near the global maximum power points, which is further integrated with the particle swarm optimization (PSO) MPPT algorithm to improve the accuracy of MPPT. Through simulations and experimentations, the higher effectiveness and accuracy of the proposed OD-PSO MPPT algorithm in solar PV systems is demonstrated in comparison to two existing artificial intelligence MPPT algorithms.

345 citations