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A cascaded generalized integral control algorithm is presented in this article for a solar energy transfer system (SETS), connected to the grid. The control algorithm introduces a two part fundamental component extraction such as, primary harmonics filter with higher order harmonic reduction and dc-offset rejection, and secondary fine fundamental component tuning with fractional order and lower harmonics rejection property. This SETS transfers electrical energy converted from solar radiant energy, efficiently to the three-phase distribution grid. The two-stage system consists of a boost type dc–dc converter on the primary side. Moreover, the incremental conductance algorithm-based operation of the boost converter ensures maximum power output from the photovoltaic (PV) array. This system is designed to meet load demands and feeds remaining power to the grid. It mitigates the reactive power and harmonics requirements of the load at any irradiance level, and thereby keeps the balanced sinusoidal grid currents, in-phase with the respective grid voltages. As the PV array power and load power are varying, performance of SETS with adverse operating conditions is validated in this work. A prototype is developed and tested under varying irradiance conditions as well as nonlinear unbalanced load. The steady-state and dynamic behaviors of the system during transient operating conditions are expressed to substantiate the acceptability of the control technique for multiobjective grid-connected SETS.

A mixed solution of 2-aminopyridine and succinic acid, with a 1:1 molar ratio, was kept at room temperature to develop a 2-aminopridinium succinate succinic acid (2APSS) crystal. The crystal structure was confirmed and cell parameter values were carried out using single-crystal XRD analysis. A FTIR spectrometer was used to identify the various functional groups in the 2APSS crystal. UV–Vis–NIR spectral analysis displayed optical parameters of the 2APSS crystal, namely lower cut-off wavelength, percentage of optical transmittance and band gap energy. The estimated values of lower cut-off wavelength and band gap energy are 354 nm and Eg = 5.77 eV, respectively. The dielectric behaviour of the 2APSS crystal was analysed. The thermal properties, namely thermal stability and melting point of the crystal (159 °C), were found by employing differential scanning calorimetry. The 2APSS crystal soft material category was confirmed by Vicker’s microhardness study. A photoluminescence study was implemented to find out the emission spectrum of 2APSS. To demonstrate the third-order susceptibility of the produced crystal, Z-scan technique were used. It is important that the title material has a variety of excellent physicochemical and nonlinear optical characteristics, which assist it in gaining recognition as a prospective candidate for nonlinear optical device applications.

An organic conjugated chromophore 2-aminopyridinium malonate (2APM) single crystal was synthesized and grown-up by means of slow solvent evaporation method. The unit cell parameters were assessed from single-crystal X-ray diffraction analysis. The various characteristic fundamental vibration frequencies were identified by FTIR spectroscopic studies. Optical parameters like nature of transmittance, lower cut-off wavelength, and band gap (Eg) were found using UV–Vis–NIR spectrum. The mechanical property like microhardness of the 2APM sample was studied using a Vickers microhardness tester. The thermal stability nature of the grown crystal was determined using differential scanning calorimeter examination. The dielectric behavior of the 2APM crystal was studied at various frequencies and temperature. A Z-scan technique was used to investigate the third-order NLO response in 2APM.

Nonlinear optical single crystals of pure potassium dihydrogen phosphate and potassium chloride-doped potassium dihydrogen phosphate were grown by slow evaporation technique at room temperature. The powder X-ray diffraction analysis shows the reflection lines of the doped KDP crystal correlate well with the observed individual parent compound pure KDP with a slight shift in the intensity of the diffracted peaks. The crystal structure lattice parameters and space group was determined by single-crystal XRD studies. The existences of several functional groups were extricated by shifting of peaks in FTIR spectral inspections. The UV cut-off wavelength is found to be 381 nm for pure KDP 383 nm for potassium chloride-doped KDP crystals, respectively, using UV–Vis-NIR studies. The permittivity and dielectric loss tangent of the grown crystals are less at elevated frequencies with different temperatures. The correlative second harmonic (SHG) potency was evaluated by the Kurtz and Perry method for the doped crystal, and it was found to be 0.34 times higher than that of the pure KDP. The thermal stability measurement was carried out by TG/DTA study. Mechanical stability was found from load-dependent Vickers micro-hardness analysis.

This paper proposes a multifunctional grid-tied solar photovoltaic (PV) system with a multifeatured adaptive control using a two-leg voltage source converter (VSC). This topology provides multifunctions such as injection of real power output from a PV array and improvements of power quality. It provides reactive power compensation; hence, unity power factor (UPF) is realized at the grid. Moreover, it performs various functions such as balancing of grid currents, harmonics mitigation and compensation of neutral current. The maximum power point tracking (MPPT) algorithm is used for harvesting the peak PV array power. The proposed topology is simulated using MATLAB/SIMULINK toolbox. Simulated responses are validated through experimental results.

In this article, a novel single-layer decoupled multiple-order generalized integral-based control algorithm is used for a single-stage solar energy grid integrator (SEGI) with maximum power extraction. The single-layer decoupled structure is used to extract the fundamental component of load current. Moreover, the online grid frequency estimation is carried out for an accurate band-pass filtering. The single-layer architecture of the control for the three-phase load current estimation, reduces the control complexity, and improves the response time. Moreover, the single-stage system is operated with the maximum power point tracking based on the residual incremental conductance algorithm. Hence, the cost of a new conversion stage and additional control are saved. This system is operated under three operating modes. In “normal-mode,” it feeds power to the load and the grid. Wherein the “sharing mode,” SEGI and grid supply the load power. During the night, SEGI functions as an active filter, which is termed as “filter-mode.” The steady-state and dynamic performances of SEGI during each operating mode and transition between the modes due to irradiation variation as well as load fluctuation are verified experimentally on a developed prototype. Moreover, test results under dynamic load variations such as nonlinear and unbalanced load conditions are presented to validate the theoretical claims.

The high power grid integrated solar energy system (GISES) prefers multilevel inverters for reduced switching losses and lower harmonics in the injected current. The integration of solar PV array with multilevel inverters (MIs) requires a proper selection of multioutput dc–dc converters. Moreover, the performance of two-stage GISES with isolated multioutput dc–dc converters and dc–ac multilevel inverters are less investigated in the literature. In this article, a cascaded H-bridge multilevel inverter with isolated multiple-output zeta converter is used. It exhibits reduced switching stresses and improved efficiency, concerning to multiple dc–dc converters fed MI. The maximum power point tracking method, based on the firefly algorithm, is implemented on the isolated multiple output zeta converter to ensure maximum power extraction at adverse irradiation conditions. The power quality improvement and active power exchange through a band stop generalized integral control, and the grid synchronization is achieved through an enhanced phase-locked loop method. The proposed system is designed and simulated in MATLAB/Simulink, and the results validate the theoretical claims. The performance of the GISES is verified using an experimental prototype developed with the help of a dSPACE Micro Lab Box and a solar PV simulator.

Organic nonlinear optical l-phenylalanine d-mandelic acid (LPDMA) single crystals have been harvested adopting slow solvent evaporation solution growth technique (SSEST) with growth period of 15 days. The XRD studies of the crystal confirm the non-centrosymmetric nature of the crystal. The presence of functional groups for the formation of the compound was confirmed by Fourier Transform Infrared (FTIR) analysis. The UV–Visible spectral studies ascertained linear optical quality and estimation of optical parameters. The nonlinear optical property was studied from Kurtz-Perry powder technique and Z-scan technique. The quantum chemical calculations such as HOMO–LUMO and Molecular Electrostatic Potential (MEP) were calculated and presented. In order to find out various mechanical parameters such as Vicker’s hardness number (Hv), Mayer’s index (n), yield strength (σy) and stiffness constant (C11), Vicker’s microhardness tester was utilized.

Glycine and its related compounds play a prominent role in the field of nonlinear optical studies and of fibre optical communication. In the present work, glycine sodium nitrate (GSN) crystal was grown using the method of slow evaporation method. The GSN crystal belongs to space group Cc in the monoclinic system. Using the FTIR spectrophotometer, the different functional groups have been qualitatively identified. A UV–Vis–NIR spectroscopy was used to record the optical absorption spectra, and the optical energy bandgap of GSN crystal is reported. The SHG conversion efficiency of GSN is determined by Kurtz and Perry technique. The Z-scan experiment was conducted to analyze GSN crystal for third-order NLO behavior and it is used to calculate the values of the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility. Third-generation harmonic studies reveal that GSN is an excellent material useful in the fabrication of NLO devices due to its nonlinear response characteristics. The thermal stability of the grown crystal was determined through TG/DTA examination. Also photoconductivity studies confirm the negative photoconductive behavior of GSN and I–V characteristics measurement that have been carried out. The dielectric loss is significantly low and this supports defect-free growth of the crystal. These properties of GSN make it a good candidate in the fabrication of NLO devices.

Single crystals of l-arginine sodium nitrate semiorganic nonlinear optical crystal were grown by slow evaporation process at room temperature. The single crystal X-ray diffraction study confirms that the unit cell parameters of the grown l-arginine sodium nitrate crystal. Fourier transform infrared spectrum analysis was used to identify the functional groups of the grown crystal. The thermal stability of the l-arginine sodium nitrate was determined using thermogravimetric analysis and differential thermal analysis. The linear optical property of LARSN crystal has been studied using Ultraviolet–visible spectroscopy studies in the wavelength range 200–800 nm. The relative second harmonic efficiency of the l-arginine sodium nitrate compound is found to be 0.49 times that of Potassium Di-hydrogen phosphate. The mechanical property of the grown crystals was determined by Vicker’s micro hardness test and it proved the hard nature of the grown crystal. Dielectric study reveals that both dielectric constant and dielectric loss decreases with increase in frequency.

l-Malic acid sodium nitrate, a novel semi organic nonlinear optical crystal was grown from aqueous solution by slow evaporation method at room temperature. The cell parameters for the grown crystal were determined by using single crystal X-ray diffraction method. The different functional groups with different modes of vibrations were confirmed by FTIR spectral analysis. The optical absorption studies show that the crystal has wide optical transparency in the entire visible region. From UV absorption profile, the electronic optical band gap and Urbach energy is calculated as 5.0 eV and 0.1401 eV. The photoluminescence spectra exhibit different peaks to indicate the single transitional band structure and high purity of the grown crystal. The EDAX and SEM study shows the presence of elements in the grown crystal and growth of second layer over the surface. The second harmonic generation efficiency was confirmed by the Kurtz powder method using Nd:YAG laser with fundamental wavelength of 1064 nm. DSC study shows that the grown crystal was thermally stable up to 273 °C. The dielectric behavior of the grown crystal was measured in the frequency range 50 Hz–5 MHz at different temperatures. The Vickers micro hardness studies were carried out on the grown crystals and there by Vickers hardness number (Hv) and work hardening coefficient (n) were calculated.

l-Alanine dl-mandelic acid hemihydrate (LADLMAH) an organic nonlinear optical chromophore crystal was synthesized using water as solvent and the crystals were grown by a slow solvent evaporation method. The single crystal X-ray diffraction study reveals that the crystals possess to triclinic system with acentric space group P1. The coordination of different moieties present in the compound and molecular structure were elucidated by vibrational and NMR spectroscopic studies. The lower cut-off wavelength is observed down to 258 nm and direct optical band gap was calculated as 5.20 eV. Second harmonic generation was confirmed by Kurtz–Perry powder method. Discrete thermodynamic properties were carried out by TG–DTA techniques. A multiple shot laser technique was adopted to investigate the surface laser damage of the crystal. The microhardness test was carried out employing one of the as-grown hard crystals and there by hardness number (Hv) and Meyer’s index (n) were assessed. The dielectric behaviour of the grown crystal was studied for different temperatures at different frequencies. The third-order optical nonlinearity parameters of LADLMAH were investigated in detail using a Z-scan technique with Nd:YAG laser at 532 nm.

Optically active single crystals of L -phenylalanine D -methionine (LPDM) were grown by slow evaporation technique by co-crystallization of amino acids L -phenylalanine and D -methionine in water. The unit cell dimensions have been identified from single crystal X-ray diffraction technique. The existences of various hydrocarbyls were examined by FTIR and FT-Raman spectroscopy. The carbon and hydrogen environment of the grown crystals were analyzed by FT NMR spectrum. The optical absorption studies show that the crystal is transparent in the visible region with a lower cut-off wavelength of 259 nm and there by optical band gap energy E g is calculated to be 5.35 eV. The Urbach energy, extinction coefficient, reflectance were calculated from UV-absorption data. Further, the thermal stability and accurate melting point has been investigated by TG/DSC techniques. The Kurtz powder SHG was confirmed using Nd:YAG laser with fundamental wavelength of 1064 nm. The dielectric behavior of the specimen has been determined for various temperatures (313 K, 333 K, 353 K, 373 K) at different frequencies. Fluorescence study and the time resolved decay calculation was also performed for the LPDM crystal. Optical nonlinear susceptibility was measured in LPDM and the real and imaginary part of χ 3 was evaluated by Z-scan technique using open and closed apertures.

An organic nonlinear optical (NLO) single crystal of l-asparagine monohydrate admixtured dl-mandelic acid (LAMDLMA) has been grown by slow evaporation technique. Single crystal XRD ascertained orthorhombic system with noncentrosymmetric space group for LAMDLMA. The occurrence of prospective functional groups was initially identified by FTIR and FT-Raman spectroscopic studies. UV–visible spectral study assessed the optical quality and band gap energy was evaluated. The title crystal shows excellent resistance to laser radiation with threshold up to 1.36 GW/cm2. The thermal stability and mechanical behavior of LAMDLMA was investigated. The dielectric analysis of the sample reveals the electric field response as a function of frequency. The second order and third-order nonlinear optical response of LAMDLMA was confirmed by Kurtz–Perry and Z-scan technique recommended its suitability in NLO applications.

A nonlinear optical bulk single crystal of L-methionine admixtured D-mandelic acid (LMDMA) has been grown by slow solvent evaporation technique using water as solvent at ambient temperature. The crystallized LMDMA single crystal subjected to single crystal X-ray diffraction study confirmed monoclinic system with the acentric space group P2 1 . The FTIR analysis gives information about the modes of vibration in the various functional groups present in LMDMA. The UV–visible spectral analysis assessed the optical quality and linear optical properties such as extinction coefficient, reflectance, refractive index and from which optical conductivity and electric susceptibility were also evaluated. The frequency doubling efficiency was observed using Kurtz Perry powder technique. A multiple shot laser was utilized to evaluate the laser damage threshold energy of the crystal. Discrete thermodynamic properties were carried out by TG-DTA studies. The hardness, Meyer's index, yield strength, elastic stiffness constant, Knoop hardness, fracture toughness and brittleness index were analyzed using Vickers microhardness tester. Layer growth pattern and the surface defect were examined by chemical etching studies using optical microscope. Fluorescence emission spectrum was recorded and lifetime was also studied. The electric field response of crystal was investigated from the dielectric studies at various temperatures at different frequencies. The third-order nonlinear optical response in LMDMA has been investigated using Z-scan technique with He-Ne laser at 632.8 nm and nonlinear parameters such as refractive index (n 2 ), absorption coefficient (β) and susceptibility (χ 3 ) investigated extensively for they are in optical phase conjucation, high-speed optical switches and optical dielectric devices.

An efficient nonlinear optical semiorganic material L -valinium L -valine chloride (LVVCl) was synthesized and grown-up by means of slow evaporation process. Single crystal XRD evince that LVVCl corresponds to monoclinic system having acentric space group P21. The diverse functional groups existing in LVVCl were discovered with FTIR spectral investigation. The UV-Visible and photoluminescence spectrum discloses the optical and electronic properties respectively for the grown crystal. Several optical properties specifically extinction coefficient, reflectance, linear refractive index, electrical and optical conductivity were also determined. The SEM analysis was also carried out and it portrayed the surface morphology of LVVCl. The calculated value of laser damage threshold was 2.59 GW/cm2. The mechanical and dielectric property of LVVCl was investigated employing microhardness and dielectric studies. The second and third order nonlinear optical characteristics of LVVCl was characterized utilizing Kurtz Perry and Z scan technique respectively clearly suggest its suitability in the domain of optics and photonics.

Single crystals of L -phenylalanine dl-mandelic acid [C9H11NO2. C8H8O3], have been grown by the slow evaporation technique at room temperature using aqueous solution. The single crystal XRD study confirms monoclinic system for the grown crystal. The functional groups present in the grown crystal have been identified by FTIR and FT-Raman analyses. The optical absorption studies show that the crystal is transparent in the visible region with a lower cut-off wavelength of 257 nm and the optical band gap energy Eg is determined to be 4.62 eV. The Kurtz powder second harmonic generation was confirmed using Nd:YAG laser with fundamental wavelength of 1064 nm. Further, the thermal studies confirmed no weight loss up to 150°C for the as-grown crystal. The photoluminescence spectrum exhibited three peaks (414 nm, 519 nm, 568 nm) due to the donation of protons from carboxylic acid to amino group. Laser damage threshold value was found to be 4.98 GW/cm2. The Vickers microhardness test was carried out on the grown crystals and there by Vickers hardness number (Hv), work hardening coefficient (n), yield strength (σy), stiffness constant C11 were evaluated. The dielectric behavior of the crystal has been determined in the frequency range 50 Hz–5 MHz at various temperatures.

In this paper, different Distribution Static Compensators (DSTATCOMs) topologies, state of the art, their performance, design considerations, future developments, and potential applications are investigated for power quality improvement. These DSTATCOMs for three-phase three-wire systems and three-phase four-wire systems are developed and installed in the distribution system for many functions, such as reactive power compensation, harmonics elimination, load balancing, and neutral current compensation. This paper is aimed to explore a broad perspective on DSTATCOMs to researchers, engineers, and the community dealing with the power quality improvement. A classified list of some latest research publications is also provided for quick reference.

In this paper, different voltage injection schemes for dynamic voltage restorers (DVRs) are analyzed with particular focus on a new method used to minimize the rating of the voltage source converter (VSC) used in DVR. A new control technique is proposed to control the capacitor-supported DVR. The control of a DVR is demonstrated with a reduced-rating VSC. The reference load voltage is estimated using the unit vectors. The synchronous reference frame theory is used for the conversion of voltages from rotating vectors to the stationary frame. The compensation of the voltage sag, swell, and harmonics is demonstrated using a reduced-rating DVR.

In this paper, a neural-network (NN)-controlled distribution static compensator (DSTATCOM) using a dSPACE processor is implemented for power quality improvement in a three-phase four-wire distribution system. A three-leg voltage-source-converter (VSC)-based DSTATCOM with a zig-zag transformer is used for the compensation of reactive power for voltage regulation or for power factor correction along with load balancing, elimination of harmonic currents, and neutral current compensation at the point of common coupling. The Adaline (adaptive linear element)-based NN is used to implement the control scheme of the VSC. This technique gives similar performance as that of other control techniques, but it is simple to implement and has a fast response and gives nearly zero phase shift. The zig-zag transformer is used for providing a path to the zero-sequence current in a three-phase four-wire distribution system. This reduces the complexity and also the cost of the DSTATCOM system. The performance of the proposed DSTATCOM system is validated through simulations using MATLAB software with its Simulink and Power System Blockset toolboxes and hardware implementation.

A detailed investigation is made into the causes, standards, and remedies of the excessive neutral current. A reduced-rating voltage-source converter with a zig-zag transformer as a distribution static compensator is proposed for power-quality improvement in the three-phase four-wire distribution system. The proposed DSTATCOM is employed for the compensation of reactive power, harmonics currents, neutral current, load balancing and the voltage regulation at the point of common coupling. The zig-zag transformer is used for providing a path to the zero-sequence current. The performance of the DSTATCOM is validated through extensive simulations using MATLAB software with its Simulink and power system blockset toolboxes.