Narrow Results

Samples with the nominal composition Bi₂Sr₂GdCu₂O_y in Bi-2212 where Gd replaces Ca as well as samples without Gd were prepared by solid-state reaction method. From the room temperature X-ray diffraction data, the samples were found to be similar to the single phase Bi-2212 structure. Impedance studies were performed from room temperature to 423 K at different frequencies in the range of 10 to 700 KHz. The AC conductivity increases with temperature and frequency, exhibiting frequency dispersion at low temperature region. The activation energy from AC conductivity in the high temperature region is found to be 0.432 eV. The permitivity increases with the increase in temperature and at 373 K it shows a maximum value exhibiting a dielectric loss. Complex impedance spectra are analyzed in terms of bulk relaxation and interfacial effects. The activation energy of the dipoles involved in the relaxation was estimated to be 0.482 eV. The universal power law of Jonscher is verified in the present system.

Detailed structural and dielectric properties of Lanthanum-doped barium titanate ${\text{Ba}}_{1-x}$La_x${\text{Ti}}_{(1-x∕4)}$O₃ ceramic powders BLTx (where $x=0.00$; 0.10; 0.20; 0.30 and 0.40)/BT, BLT10, BLT20, BLT30 and BLT40, synthesized by the sol gel process, calcined at 900^∘C for 3h and sintered at 1250^∘C for 6h, have been investigated. The phase formation and crystal structure of the samples were checked by X-ray diffraction (XRD) and Raman spectroscopy. The samples crystallize in the pure perovskite structure that transforms from tetragonal to pseudocubic under doping with La; results that have been confirmed by Rietveld Refinement technique. The estimated average crystallite size of the samples was about 23nm. Dielectric parameters (dielectric permittivity and losses) were determined in the temperature range room temperature (RT) — 280^∘C and in the frequency range 500Hz–2MHz. La doping gives rise to a strong decrease of the ferro-to-paraelectric transition temperature, and the frequency dependence of the permittivity shows that the samples with $x=0.00$ and $x=0.10$ reach their resonance frequency. The frequency dependence of impedance and electric modulus properties were studied over a wide frequency range from 1kHz to 2MHz at various temperatures to confirm the contributions from grains and grain-boundaries. The complex impedance analysis data have been presented in the Nyquist plot which is used to identify the corresponding equivalent circuit and fundamental circuit parameters; it was found that the grain boundaries resistance is dominant at room temperature. The frequency dependence of the parameters permittivity, losses and AC conductivity reveals that the relaxation process is of the Maxwell–Wagner type of interfacial polarization.

Frequency-dependent dielectric constant, dielectric loss, AC conductivity values and complex impedance spectra of V₂O₅-added Ni–Co–Zn ferrites (${\text{Ni}}_{0.62}$${\text{Co}}_{0.03}$${\text{Zn}}_{0.35}$Fe₂${\text{O}}_4+$$x$V₂O₅, where $x=$ 0, 0.5, 1 and 1.5 wt.%) have been investigated at room temperature. The dielectric properties of the samples follow the Maxwell–Wagner polarization model. An inverse relationship was found between dielectric constant and AC electrical resistivity for all the samples. The dielectric constants decreased with the addition of V₂O₅, while the electrical resistivities of V₂O₅-added Ni–Co–Zn ferrites are found to be larger than that of pure Ni–Co–Zn ferrite. The AC conductivity was reduced with the addition of V₂${\text{O}}_5$to Ni–Co–Zn ferrite at lower-frequency region. However, AC conductivity shows a sharp increase at higher-frequency region, which could be attributed to the enhancement of electron hopping between the Fe${}^{2+}$ and Fe${}^{3+}$ ions in the ferrite matrix due to the activity of the grains. The complex impedance spectroscopy results through Cole–Cole/Nyquist plot have demonstrated a single semicircular arc. It indicates that conduction mechanism takes place predominantly through the grain/bulk property, which could be ascribed to the larger grain size of V₂O₅-added Ni–Co–Zn ferrites.

The relaxation property of sodium silicate $({\mathrm{\text{Na}}}_2{\mathrm{\text{SiO}}}_3)$ (SS) was investigated by complex impedance spectroscopy (CIS) in a wide range of frequency (100kHz–5MHz) and temperature $(50^{\circ }\mathrm{\text{C}}\text{–}450^{\circ }\mathrm{\text{C}})$. Orthorhombic crystal phase was synthesized by a sintering process. The CIS study shows high complex impedance in low-frequency region due to strong dispersion and controls the relaxation mechanism of ions or cations in the crystal lattice. A decrease of the energy loss $(tan\delta )$ occurs with increasing frequency for all temperatures showing the normal behavior of SS. Relaxation time was calculated using the dielectric functions $Z^{\prime \prime }(\omega )$ and $M^{\prime \prime }(\omega )$. The temperature dependent relaxation plot follows the Arrhenius law, where the slope represents the activation energy.

Microgrid technology provides an effective solution for industrial flexible electricity consumption and promotes the utilization of renewable energy. In this paper, to achieve the active and reactive power sharing in industrial microgrids with complex impedances, a distributed adaptive virtual impedance control method is proposed. For the power coupling, an impedance-power droop equation is proposed to generate virtual resistance and inductance, thereby eliminating the effect of mismatches among line impedances. It is highly resilient to power and line changes in industrial scenarios. On this basis, the practical consensus is used to obtain the desired power representing power sharing conditions. Finally, simulations have been carried out in MATLAB/Simulink to illustrate the validity of theoretical results.