Capacitance Of Capacitor Research Articles

Determination of inductor parameters of induction charging device for contactless method of charging electric transport

THE PURPOSE. The lack of charging infrastructure is one of the main reasons for the refusal to use electric vehicles in Russia. The solution could be the development of mobile electric vehicle charge units (MCSEU). To implement a truly competitive product, it is necessary to take into account all possible types of electric vehicle charging, and not only standard ones, CHAdeMO, CCS, etc., but also wireless charging based on an induction charger (IC). Therefore, the purpose of this work is to model the two main types of IC implementation, compare the results obtained, and develop a physical modeling model for the selected scheme.MATERIALS. IC is based on the principle of magnetic induction, so the simulation was carried out for two options for implementing contactless charging, the frequency and value of the inductances of the coupled coils were calculated, and based on the results obtained, conclusions were drawn about the optimal distance at which the required efficiency value is maintained. For physical modeling of the process of non-contact charging of electric vehicles, a calibrator model has been developed, and ferrite plates have been calculated.RESULTS. Based on the simulation, a scheme for the implementation of the IC with adjustable capacitor capacitance was chosen, the topologies of antennas and the geometry of ferrite plates and a design documentation of a 6-axis calibrator for testing were developed. R&D was carried out at the Federal State Budgetary Educational Institution of Higher Education "KSPEU".CONCLUSION. The use of IC provides great opportunities for the development of mobile charging stations, as it increases the number of possible connections. However, efficiency and charging distance are critical for this equipment, therefore, already at the modeling stage, it is necessary to select the parameters of the coils as accurately as possible, and the circuit used. For the developed MCSEU, within the framework of Resolution 218, optimal solutions were identified in the field of modeling and testing of IC.

Mitigation of power oscillations for energy harvesting capability improvement of grid-connected renewable energy systems

The increasing penetration of renewable energy sources in the power system raises several challenges from the power quality and output power fluctuations point of view. However, the output power oscillations and power quality problems caused by the low order harmonic oscillations at the second-order frequency of the utility grid on the dc-link capacitor are emerging as major issues for the efficient operation of power converters. In this manner, a novel method based on modification in the control algorithm to alleviate the output power oscillation and reduce the output current total harmonic distortion is proposed. The proposed control approach seems as a promising solution for the satisfactory grid operation of renewable energy sources regarding not requiring any additional circuit and increment in the capacity of the dc-link capacitor. Moreover, mitigation of oscillations enhances the active power reference tracking capability of the controller that enables the overall efficiency improvement of the system. The performed case studies reveal that the overall efficiency rate of the system is increased by 1.3%. On the other hand, the output current harmonic distortion is decreased below 3% even under low power operating conditions. Also, the complexity level of the control algorithm is quite low for real-time implementation.

Single and Double Input DC Sources Multilevel Inverter Topologies With Reduced Components Counts and Voltage Boosting Property for Grid-Connected Photovoltaic Converters

This article proposes a single-source nine-level multilevel inverter topology that handles a reduced number of components. Moreover, it utilizes the virtual dc sources in terms of the switched capacitors to reduce the number of the active dc source. Those capacitors have a self-charging with naturally balancing capability. The proposed topology can be upgraded to a 19-level configuration. This modification is performed by adding a single supply and a pair of switches. To highlight the good features of the proposed structures, a set of comparative studies are held with other structures based on some of the performance evaluating parameters. The comparison results prove the superiority of the proposed configurations over the other comparative references. A simple method is presented to estimate the boundary for the capacitance of capacitors. The performance of the proposed configurations is validated through the practical prototypes for these structures, which are implemented and tested based on the dSPACE (DS-1103) hardware. For further validation, the proposed topology is integrated with a photovoltaic (PV) system to study its performance with a high output power system.

Home-made pulse magnet power supply for magnetizing permanent magnets and magnetic measurements

In this article, we propose a home-made pulse magnetic field generation system constructed using a thyristor and large capacitance capacitors to generate high magnetic fields to investigate magnetic properties and magnetize the magnet and high-performance magnetic materials at room temperature. The proposed system produced a magnetic induction (magnetic field) μ 0 H of 15.6 T with the 33.6 mF capacitor and an excitation voltage of 600 V. Further, we designed a new power supply system and a pulse magnet using the commercially available pulse magnet and power supply. We found that the duration time of the magnetic fields (t d) and the generated magnetic fields were three and four times larger than those for a conventional system, respectively. We also performed magnetization of a NEOMAX permanent magnet; the coercivity (Β CJ) was 2.0 T, and the magnetization saturated at ∼4.0 T. These results suggest that we can magnetise a permanent magnet such as NEOMAX with strong magnetic fields using this system. Further, the magnetic measurements of these magnets can be performed as well. The merit of our system is that the capacitance of the capacitor bank is larger than that of other studies or general commercial power supplies. Therefore, relatively high magnetic fields with long duration time can be generated. We also performed experiments on the magnetization process (M-H) of Gd to investigate the magnetocaloric effect in high magnetic fields. The magnetic entropy change was comparable to the result of former investigation. We believe that our research can contribute to the development of permanent magnets and magnetic materials for scientific and industrial use because our system allows the generation of strong magnetic fields at room temperature.

Coherent construction of recovered γ-Al2O3 embedded N-doped activated carbon by supercritical-CO2 pathway: Robust hybrid electrode material for energy storage device

Electrochemical energy storage application is one of the most impressive solutions to the problem of fossil fuel depletion. However, the lower capacitance in electric double-layer capacitors and poor stability in pseudocapacitors remain significant challenges. State of an art, we demonstrated the fabrication of hybrid electrode material with aluminium oxide nanoparticles (Al2O3 NPs) embedded in N-doped activated carbon (AC) by supercritical-CO2 approach. The N-doped activated carbon and Al2O3 NPs were prepared by Dracaena trifasciata biomass and the strategic recovery of domestic aluminium waste. The prepared materials were inspected through microscopic and various spectroscopic techniques. The morphological observation of Al2O3@DT-AC manifested well impregnation of Al2O3 NPs to DT-AC surface, resulting in a higher capacitance of 1031.6 F/g at 0.5 A/g than Al2O3 (258.5 F/g). Further, the respectable capacitance retention signifies that Al2O3@DT-AC are promising electrode materials for supercapacitors. The material preparation and processing techniques are eco-friendly and considered to be green processing.

Precise calculation of electrical capacitance by means of quadruple integrals in method of moments technique

In this paper, the capacitance of a parallel plate air-gap rectangular capacitor, and a unit cube capacitor have been calculated. Because of its generality and simplicity, the method of moments (MOM) Technique is utilized. In order to improve the accuracy of the calculations, the use of quadratic integrals instead of binary integrals has been proposed. A neat form is provided for the analytical solution of the integrals required for the method of moment. The results show that there is a very small error in calculating the capacity even with coarse boundary division. The described formulas and codes can easily be used for similar purposes.

High-performance self-powered integrated system of pressure sensor and supercapacitor based on Cu@Cu2O/graphitic carbon layered porous structure

With the rapid development of human-machine technology, self-powered pressure sensor integrated systems have been extensively studied. However, there are only a few reports on such multifunctional devices using a single active material. In this work, we report a flexible integrated system, which consists of flexible pressure sensors and supercapacitors. Both of the devices were fabricated based on layered porous Cu@Cu2O/graphitic carbon (Cu@Cu2O/GC) composites, which were obtained by a one-step simple polymer heat treatment method. Due to the discontinuous conductive paths and effective stress concentration relief in the composite, the pressure sensor shows a high sensitivity of 90 kPa−1 in a wide working range of 0–150 kPa, a fast response time of 90 ms, and a detection limit of 2.4 Pa. Moreover, the layered porous structure Cu@Cu2O/GC can not only maintain the integrity of the electrode material, but also promote the diffusion of electrons, enabling super capacitors to obtain excellent electrochemical performance. The specific capacitance of the super capacitor is 17.8 mF cm−2. More importantly, the flexible self-powered integrated system could be directly attached to the human body to detect human motions, showing its great potential application in wearable devices.

Theoretical investigation of the nanoinclusions shape impact on the capacitance of a nanocomposite capacitor

A first-principles theoretical approach to the effective dielectric permittivity of a nanocomposite, which contains nanoinclusions dispersed in a host dielectric enclosed between two parallel metallic electrodes, is developed. The inclusions are modeled by spheroids, and their response to the external electric field is found using the point dipole approximation and Green’s function approach. As a result, besides the mutual interactions between the induced dipoles, the local field in the nanocomposite contains also a contribution from the dipole field reflected from the capacitor electrodes. It is shown that the nanocomposite dielectric permittivity is determined by an average inclusion polarizability density, and its dependence on the aspect ratio and orientations of inclusions is found analytically and investigated. The theoretical predictions derived in the paper are in excellent agreement with the available experimental data and can be used for a proper design of nanocomposite capacitors.

Method of calculation of electromagnetic torque and energy losses of three-phase induction motors when powered by a regulated single-phase voltage

Introduction. Single-phase power supply of induction motors is used in public utilities, in microclimate control systems for remote agricultural consumers, in water supply and pipeline transport systems, etc. In practice, there is the use of induction motors with three-phase stator winding in the conditions of single-phase power supply. Starting and operating capacitors are used to enable their operation when powered by a single-phase network. Problem. There are many fairly accurate methods for calculating the characteristics of an induction motor in asymmetric, including single-phase, modes of operation, but they are based on differential equations, which does not allow to obtain analytical expressions for preliminary analysis and synthesis of such systems. Goal. The purpose of this article is to develop the analytical method of definition of electromagnetic torque and energy losses of voltage-regulated three-phase induction motors working according to the scheme of single-phase inclusion with the phase-shifting capacitor. Methodology. The method is based on the theory of symmetric components and analysis of replacement schemes of induction machine in motor and generator modes. Results. The analysis of the obtained data shows that at a constant value of the phase-shifting capacitor capacity induction motor working according to the scheme of single-phase inclusion has a minimum of losses at one value of slip at different values of supply voltage. Therefore, if you keep this slip constant when the load changes, you can achieve a mode of minimizing losses at a constant value of the capacity, optimal for this slip. This shows that the thyristor voltage regulator can be used as an energy-saving element under variable load, while the capacitance of the phase-shifting capacitor can remain constant when changing the load in a wide range provided that this slip is stabilized. Originality. The developed method allows to obtain analytical expressions for comparative analysis of electromagnetic torque and energy losses of three-phase induction motors powered by a single-phase network at different values of the capacity of the phase-shifting capacitor, supply voltage for different variants of schemes for including three-phase induction motors in a single-phase network. Practical value. Based on the developed analytical method, the optimal parameters of phase-shifting capacitors and rational schemes for including three-phase induction motors in a single-phase network can be determined.

Optimization of Sintering Conditions to Enhance the Dielectric Performance of Gd3+ and Ho3+ Codoped BaTiO3 Ceramics

BaTiO3 dielectric capacitors, one of the important energy storage devices, play critical roles in storing electricity from renewable energies of water, wind, solar, etc. The synthesis of BaTiO3 ceramics with weak temperature dependence and a high dielectric constant at room temperature (εRT') is an urgent problem to meet the miniaturization and large capacity of dielectric capacitors. Doping rare earth elements into BaTiO3 can solve this problem, but it is still challenging. In this work, we adopt a synergistic strategy of increasing εRT' and improving the temperature stability by codoping Gd3+ and Ho3+, respectively, to address this challenge. By carefully adjusting the synthesis conditions in the solid-state reaction, codoping 7% Gd3+ and 7% Ho3+ in BaTiO3 (BGTH7) ceramics were synthesized. The temperature-dependent dielectric constant reveals that the obtained optimal BGTH7 ceramic satisfies the X7U specification and displays a stable ε' in the temperature range of -55~125 °C. The optimal BGTH7 ceramic after sintering at 1400 °C for 6 h exhibits a high dielectric constant of 5475 and low dielectric loss (tan δ) of 0.0176, hitherto exhibiting the best performance in X7U ceramics. The findings in this work are conducive to the miniaturization and stabilization of dielectric energy storage devices.

Multi-stage voltage droop compensation based on resonant circuit for unipolar solid-state Marx Generators.

The low-voltage droop of high-voltage pulses is required to provide stable pulsed electric fields in many applications. Increasing the capacitance of energy storage capacitors increases both the size and the cost of the system. In this paper, four compensation stages based on the resonant circuit have been inserted into a 16-stage solid-state Marx generator to compensate for the voltage droop in different conditions. The nearly linear part of the sinusoidal voltage is precisely added to the load during discharging as compensation, and the rectangular pulsed voltage with little droop can be realized. Different numbers of compensation stages and different resonant inductances can compensate the droop to different levels, which means the compensation effect is also adjustable. Moreover, these compensation stages can operate as common stages in Marx generators as long as we open-circuit the resonant circuits. Since the capacitors in resonant compensation stages are also charged in parallel with capacitors in common stages, no auxiliary power supply is required. Simulating and experimental results show that the droop of a 9kV pulse can be ideally compensated over a 500Ω resistive load at various pulse widths. The pulse width should be shorter than the length of the nearly linear part of the sinusoidal voltage.

DC Link Capacitor 열화에 따른 태양광 인버터 입출력 특성

The DC-Link capacitor, which is the input terminal of the PV inverter, plays a role in charging/discharging and smoothing the DC voltage and smoothing the ripple. These capacitors are inexpensive, and most aluminum electrolytic capacitors are used due to their relatively fast charging/discharging characteristics. However, in DC-Link capacitors, accidents occur due to electrolyte ejection and explosion due to aging and deterioration due to increased usage time. Also PV inverter manufacturers provide status information according to usage time and related circuit design is not reflected. Therefore, in this paper, a circuit capable of simulating the occurrence of capacitor deterioration was proposed in order to examine the input/output state of the PV inverter according to the capacitance change of the DC-Link stage capacitor. By diagnosing the current state of the photovoltaic inverter due to aging and deterioration due to the change in the capacity of the DC-Link capacitor, it is possible to prevent failures in the photovoltaic system and accidents due to fire in advance. In addition, by monitoring the condition of capacitors according to the progress of deterioration, the contents of the study were proposed so that the safety and reliability of new and renewable energy facilities can be secured by obtaining appropriate information such as the life expectancy of parts and replacement time for maintenance.

Toward Advanced High‐k and Electrode Thin Films for DRAM Capacitors via Atomic Layer Deposition

AbstractDynamic random access memories (DRAMs) are currently used as the core memory in computing systems because of their high speed and density. Their demand should continue to grow owing to increased data usage. A unit cell in a DRAM consists of one transistor and one capacitor, and the data are stored in the capacitor. As the size of the unit cell decreases to improve the memory density by aggressive scaling, it is important to secure sufficient capacitance in the capacitor. In this regard, technological advances in the fabrication of capacitors are of great importance; accordingly, the materials and processing of high‐k thin films require developmental innovations. Besides, it is necessary to develop electrode materials that optimize the function of high‐k thin films. In this review, recent advances in achieving sufficient capacitance in DRAM capacitors are summarized from structural and material/process perspectives, and the future direction of DRAM capacitor development is discussed. Atomic layer deposition (ALD) is a key technique that enables the growth of functional thin films for DRAM capacitors; thus, recent advances in the deposition of high‐k and electrode thin films grown using the ALD technique are addressed.

Characterization of ALD Ta2O5, Al2O3, and Ta2O5/Al2O3 Nanolaminate as Metal-Insulator-Metal Capacitor Dielectric for GaAs HBT Technology

In order to reduce die size and increase capacity, the metal-insulator-metal (MIM) capacitor area in circuit designs fabricated using GaAs hetero-junction bipolar transistor (HBT) technology has to be reduced. This can be achieved by using a capacitor dielectric material that has a high dielectric constant or high capacitance density. In GaAs HBT technology, the MIM capacitor dielectric film is typically also required to have a high breakdown voltage (>20 V) and low leakage current. Furthermore, the deposited dielectric film has to be compatible with GaAs processing and has to be deposited at a temperature of < 300oC, due to the limited process thermal budget in the HBT technology. As a result of these requirements, there are only a few materials available for MIM capacitor dielectric application in GaAs HBT technology.In this study, 60 nm tantalum pentoxide (Ta2O5), aluminum oxide (Al2O3), and Ta2O5/Al2O3 nanolaminate deposited using atomic layer deposition (ALD) have been characterized and evaluated as MIM capacitor dielectric for GaAs HBT technology. The results show that the capacitor with 60 nm of ALD Ta2O5 has the highest capacitance density (3.84x10-15 F/μm2), followed by the capacitor with 60 nm Ta2O5/Al2O3 nanolaminate, and the capacitor with 60 nm Al2O3 capacitor dielectric film with a capacitance density of 2.40x10-15 F/µm2 and 1.37x10-15 F/μm2, respectively. The calculated dielectric constant of ALD Ta2O5 and Ta2O5/Al2O3 nanolaminate is 26.1 and 16.3, respectively, while that of ALD Al2O3 is 9.3, as shown in Figure 1.Figure 2 shows the I-V characteristics of MIM capacitors with 4055 μm2 area and with 60 nm of ALD Ta2O5, Ta2O5/Al2O3 nanolaminate, and Al2O3 capacitor dielectric. As can be seen, the capacitor with Al2O3 capacitor dielectric has significantly lower leakage and higher breakdown voltage (46 V), while the capacitor with Ta2O5/Al2O3 and Ta2O5 capacitor dielectric has higher leakage current and lower breakdown voltage of 32.7 V and 22.4 V, respectively. Figure 3 shows the C-V characteristics of capacitors with the 3 ALD capacitor dielectric films. The results show that the capacitance of MIM capacitor using these three films increased marginally by 2.2% to 4.3%, when the temperature was increased from 25oC to 125oC. No significant change in capacitance density of these ALD capacitor dielectric films was observed, when the applied voltage was varied from -5 V to +5 V. Figure 1

Harmonic suppression and uniformity improvement of plasma density in capacitively coupled plasma

A method for improving plasma uniformity in capacitively coupled plasma (CCP) is developed. Plasma contains harmonics due to the nonlinear characteristics of the sheath. Because high-frequency harmonic components in the plasma have short wavelengths, high-frequency harmonics components have a bad influence on plasma uniformity. This is because the electromagnetic standing wave effect (SWE) is severe at high frequencies. To improve plasma uniformity, a CCP using a parallel capacitor that is connected to the powered electrode is developed. By adjusting the capacitance of the parallel capacitor, a parallel resonance between the parallel capacitor and the reactor, which is net inductive, is generated. As the parallel loop approaches the parallel resonance, the currents of other harmonic frequency components in the plasma are greatly reduced. Therefore, the waveform of the plasma bulk current also becomes sinusoidal, and the amplitude of the plasma current becomes almost constant, regardless of the radial position at the parallel resonance condition. Moreover, the voltage applied across the plasma is greatly increased. Consequently, plasma uniformity and the voltage applied to the plasma along the electrode are significantly improved under the parallel resonance condition due to a greatly reduced SWE.

Parameter Identification Method With Dynamic Impedance Modulation for the DWPT System

A novel parameter identification method with dynamic impedance regulation is proposed to maintain constant output voltage of dynamic wireless power transfer (DWPT) system under varied loads and mutual inductance conditions. The resonant capacitor in the receiver side is replaced with a switched-controlled capacitor (SCC) structure, which enables the system to work under two operation modes. And then a comprehensive mathematical model is established according to these two modes to achieve the parameter identification. To avoid the deterioration of identification accuracy caused by the capacitors’ parameter drift, a dynamic impedance regulation method is introduced. The SCC is under dynamic closed-loop modulation to realize precious control of the equivalent capacitance of resonant capacitor in the receiver side. An experimental prototype is built in the laboratory, and the experimental results clearly demonstrate the accuracy of the proposed parameter identification.

A Self-Tuning Adaptive Control Scheme for a Grid-Connected Three-Phase PV System

This article presents a new self-tuning sinusoidal recursive controller (STSRC) for handling the uncertainties and disturbances in a three-phase grid-connected photovoltaic system (GCPVS). The performance of a GCPVS is greatly influenced by the uncertainties, such as intermittency in solar irradiation, change in capacitance and equivalent series resistance (ESR) of dc-link capacitor, and variation of impedance between the inverter and the grid. This STSRC comprises improved linear sinusoidal tracer-based recursive least-square estimation (IRLS) to achieve robust performances, despite the parametric uncertainties through real-time estimation of its parameters, and updation of its gains. The efficacy of the proposed STSRC is verified through simulation using MATLAB/Simulink and experimental studies pursued on a 2.5-kW prototype. It is observed that STSRC exhibits superior tracking of PV voltage with reduced ripple and improved grid current with reduced total harmonic distortion (THD) of 1.66%. The estimation accuracy is found above 92%.

Determine the Location for Reactive Power Compensation in the Microgrid Based on the Hybrid Neural Network

This paper presents a method to determine the capacity and location of compensating capacitors to reduce power loss and improve voltage quality in the Microgrid. At each bus location, the compensating capacitor capacity is varied to determine the bus location and capacitor capacity. In case of small power loss and good voltage quality, compensation position and capacity will be chosen. The construction of the neural network training dataset is done with load levels from 50% to 100%. For each load level, the reactive power compensation position and the compensation capacity will be determined. The improved PSO algorithm is proposed to improve the traditional neural network structure. The Microgrid 9-Bus power system is used to simulate and test the effectiveness of the proposed method. The results show that power loss and voltage quality achieve positive results. From the simulation results, we can conclude that the proposed neural network model is suitable for controlling the voltage quality of the Microgrid system.

Structurally integrated 3D carbon tube grid-based high-performance filter capacitor.

Filter capacitors play a critical role in ensuring the quality and reliability of electrical and electronic equipment. Aluminum electrolytic capacitors are the most commonly used but are the largest filtering components, limiting device miniaturization. The high areal and volumetric capacitance of electric double-layer capacitors should make them ideal miniaturized filter capacitors, but they are hindered by their slow frequency responses. We report the development of interconnected and structurally integrated carbon tube grid-based electric double-layer capacitors with high areal capacitance and rapid frequency response. These capacitors exhibit excellent line filtering of 120-hertz voltage signal and volumetric advantages under low-voltage operations for digital circuits, portable electronics, and electrical appliances. These findings provide a sound technological basis for developing electric double-layer capacitors for miniaturizing filter and power devices.

High-specific-capacitance electrolytic capacitors based on anodic TiO2 nanotube arrays

Electrolytic capacitors have been increasingly used in almost all electronic devices because of their large specific capacitance, broad operating voltage range and good price to performance ratio. To satisfy the continuing miniaturization trend of electronic devices, researchers have continuously maintained efforts to increase the specific capacitance of electrolytic capacitors. Herein, we report a novel way to achieve high-specific-capacitance electrolytic capacitors starting from titanium dioxide nanotube arrays (TDNAs) formed by anodization. The anodized TDNAs are first transformed into titanium nitride nanotube arrays (TNNAs) by nitridation. Then TNNAs covered with a BaTiO3 film (BaTiO3@TNNAs) are obtained through electrochemical deposition and subsequent annealing. Thus, the fabricated BaTiO3@TNNAs are employed as anode of an electrolytic capacitor. The capacitor cathode is also derived from the anodized TDNAs by an electrochemical doping approach. The capacitor made of the BaTiO3@TNNAs anode and TDNAs cathode shows excellent electrical properties with a high specific capacitance of 292.8 μF cm−2, considerably higher than previously reported values for the modified aluminum anode foils. This study can provide new directions in increasing specific capacitance of electrolytic capacitors.