Parallel Capacitor Research Articles

Quasi Power Factor Correction for High Efficient AC/DC Converter

Harmonic pollution and low power factor in power systems caused by power converters have been of great concern. To overcome these problems several converter topologies using advanced semiconductor devices and control schemes have been proposed. This investigation is to identify a low cost, small size, efficient and reliable ac to dc converter to meet the input performance index of UPS. The performance of single phase and three phase ac to dc converter along with various control techniques are studied and compared. This project presents a novel ac/dc converter based on a quasi-active power factor correction (PFC) scheme. In the proposed circuit, the power factor is improved by using an auxiliary winding coupled to the transformer of a cascade dc/dc fly back converter. The auxiliary winding is placed between the input rectifier and the lowfrequency filter capacitor to serve as a magnetic switch to drive an input inductor. Since the dc/dc converter is operated at high-switching frequency, the auxiliary windings produce a high frequency pulsating source such that the input current conduction angle is significantly lengthened and the input current harmonics is reduced. Since the use of a single inductor, the cost z reduced a lot and the efficiency of the system is improved. The power factor is maintained constant by using a buffer capacitor in parallel to the system for compensating the inductive components. It eliminates the use of active switch and control circuit for PFC, which results in lower cost and higher efficiency. Finally an R- load is applied and simulation results are presented

Structural and Dielectric Analysis of La<sub>0.88</sub>Bi<sub>0.12</sub>Mn<sub>0</sub>.<sub>80</sub>Ni<sub>0.20</sub>O<sub>3</sub> Composite

Composite La0.88Bi0.12Mn0.80Ni0.20O3 was synthesized using the conventional solid-state reaction method with sintering temperature of 1200 °C for 12 hours and the dielectric properties investigated. The X-ray diffraction result shows that the composite has a rhombohedral structure with lattice parameter of a = b = c = 5.5136 Ǻ. Scanning electron microscope shows grains with approximately from 0.8 to 5.4 μm in size with presence of voids. The dielectric permittivity, εʹ and dielectric loss, εʺ were measured in the range of 298 K to 473 K where both are temperature and frequency dependent. At 1 kHz to 100 kHz, the εʹ is around 10000 and the dielectric loss tangent, tan δ is below 1.5. The electric behavior of this composite is best represented by Quasi-dc model which consists of two universal capacitors in parallel. Parameters value from the fitting indicated that high correlations of electrons between inter and intra-clusters. The activation energy, Ea calculated from the conductivity of the sample gives a value of 0.116 eV. Vibrating sample magnetometer shows that the La0.88Bi0.12Mn0.80Ni0.20O3 has a magnetic coercivity, Hc of 36.109 G and retentivity, Br, valued 2.7504 x 10-3 emu/g.

High‐Output Force Electrohydraulic Actuator Powered by Induced Interfacial Charges

Herein, a novel soft actuator design is presented that simultaneously enables a high‐output force at a low operating voltage and an adjustable large normal displacement. The electrohydraulic actuator powered by induced interfacial charge (EPIC) uses the amplified electrostatic force when the surface charge‐inducing phenomenon of the polyvinyl chloride (PVC) gel and the geometrical gradient of the actuator are combined to reinforce the zipping motion of the liquid layer. This actuator produces a more than 50‐fold higher blocking force than conventional dielectric liquid‐coupled electrostatic actuators at 2 kV. This implies the possibility of expanding the applicability of soft actuators to high‐power transducers. This actuator is modeled as parallel capacitors by considering the interfacial‐induced charge; the ratio of the dielectric constant of the polymer film to that of the dielectric liquid is analyzed as the principal design criterion for optimizing the performance characteristics. The actuator prototype exerts a force as high as 16 times its body weight (25.5 g) and exhibits a large normal displacement of more than 20% of its height (8.5 mm). Furthermore, four actuators can lift a weight of 1.25 kg and one actuator can be used as a large‐aperture (diameter: 30 mm) varifocal lens (374% focal length variation).

Research on Key Technologies of Intelligent Control Switches in Distribution Networks

With the development and widespread application of high-power power electronics technology, there is an interaction between distribution network voltage and reactive power and power quality. It is prone to operating over-voltage and closing inrush when closing, and reignition often occurs during opening. The voltage is too high, which far exceeds the voltage and insulation performance that the equipment can withstand, resulting in damage to the equipment. In response to the above problems, this article proposes an intelligent control switch closing and opening strategy to reduce the impact on the equipment during the reactive power compensation switching process. Considering the different dispersion of the intelligent control switch, the process of closing the parallel capacitor is simulated, and the effect of the intelligent control switch on the overvoltage and inrush current limitation is compared, which proves that the strategy is effective.

Eddy Current Non-Destructive Characterization of Carbon Fiber Reinforcement Composites Considering Capacitive Effect

This paper presents a modelling procedure to take into account the capacitive effect at high frequencies, in Eddy Current Non-Destructive Characterization (EC-NDC) of Unidirectional Carbon Fiber Reinforcement Composite (UD-CFRC) rods. To simulate the complete EC-NDC systems, first, the multilayer circular air coil is physically modeled by a finite element (FE) axisymmetric eddy current model coupled to equivalent RL circuit. Each layer of the coil is represented by an equivalent resistance (R) in series with the equivalent inductance (L). Secondly, R and L of the coil layers are computed for several frequencies up to 5Mhz, and then introduced into the equivalent RLC circuit with considering inter-turn and interlayer capacitances. Then the inversion problem is solved in order to identify all inner capacitances of the coil. Finally, the UD-CFRC rod is introduced into the FE eddy current axisymmetric model coupled to an equivalent RLC circuit, as a homogenized conductive material with an equivalent transverse conductivity. The coil with the presence of the homogenized UD-CFRC rod is then modeled as a transformer with a secondary connected to a capacitor in parallel with a resistance in order to evaluate the inner capacitor of the UD-CFRC. All evaluated parameters are then introduced in the last model. The comparison between the computed impedance parts and the measured ones shows a mean error less than 2% and a maximum one of 5% according to the frequency.

A C-band low-power sub-1volt current-reused multiphase oscillator

A new sub-1V and low power multiphase voltage-controlled oscillator (QVCO) with current-reused structure is proposed. The proposed core oscillator consists of two N-metal oxide semiconductor (NMOS) and P-metal oxide semiconductor (PMOS) transistors and an additional NMOS-only cross-coupled pair that enhances the effective negative transconductance and facilities the start-up condition at sub-1V supply voltages in modern nm CMOS technologies. In the proposed coupling scheme, the gate of cross-coupled transistors is used for coupling in an ‘in-phase−anti-phase’ manner. Parallel capacitors to the drain-source of transistors have been used for further enhancement of effective transconductance and thus lower power consumption; though the increase of parallel capacitors reduces the tuning range, indicating a trade-off in the proposed QVCO. The proposed quadrature oscillator is designed and simulated in a standard 0.18 μm RF-CMOS technology. The results of the simulation show that the QVCO has a 9% tuning range from 5.35 GHz to 5.88 GHz, and the phase noise is −119.6 dBc/Hz at 1-MHz offset from the 5.7 GHz carrier while consumes only 1.4 mW from a 0.85-V supply voltage; yielding an excellent figure-of-merit (FOM) of −193.3 dBc that is amongst the best FOMs. Several Monte Carlo and PVT analyses verify the robust performance of the QVCO.

Timing strategy for boosting energy extraction from triboelectric nanogenerators

Abstract An unexpected additional energy generation by the triboelectric nanogenerator (TENG), due to its capacitive behavior, is discovered in this work. This discovery was inspired by some interesting interaction between the TENG and a power management system (PMS) developed in a recent paper (Harmon et al., 2020). After a desirable output was reported in (Harmon et al., 2020), an unusual output response with unexpectedly high output power was observed. This output response cannot be explained by the working principle of the PMS since it suggests a greater than 100% power conversion efficiency for the buck converter employed by the PMS. Detailed investigation reveals that the TENG has more energy to offer than expected from the original design of the PMS. As the buck converter transfers the energy stored in a temporary capacitor to the output, the TENG acts as a capacitor in parallel with the temporary storage capacitor, and contributes an additional amount of energy proportional to its capacitance. Since the internal capacitance of the TENG is time varying and takes the maximum value when the two triboelectric surfaces are in contact, the optimal timing for energy transfer is when the separation distance approaches 0. In practice, suboptimal timing strategies will be implemented via passive switches for simplicity and reliability.

Study on Local Measurement Method of Bus Short Circuit Capacity in Substation

The short-circuit capacity of the bus is a key parameter required for the operation and control of the power system. Online measurement of the short-circuit capacity is crucial for the observability and controllability of the power grid. In this paper, it is proposed that the bus voltage disturbance can be caused by switching on and off the parallel capacitor. According to the voltage disturbance, the on-line measurement of the short circuit capacity of the power grid can be performed. Based on the circuit model of the substation, using the substitution theorem and superposition principle of the linear circuit, the accurate calculation method of bus short-circuit capacity measurement is derived. It is revealed that the phase change of the voltage vector caused by the capacitor switching is the key factor affecting the measurement accuracy. It breaks through the approximate formulas of previous studies. The proposed measurement method has high accuracy; an iterative calculation method for the phase difference of the voltage vector is proposed. The method is more convenient and reliable than direct measurement. Based on MATLAB / Simulink, the substation bus and online measurement model are established. Simulation analysis of various scenarios shows that the proposed method has a measurement error of less than 1%, which is technically easy to implement and practically promote.

Design and Simulation Multilevel Boost Converter Using PI Controller Ziegler Nichol Method

This Paper is explain about how to design a Multilevel Boost Converter (MLBC). This Converter is a Boost Converter with an upgrade of Parallel Diode Circuit and Capacitors Circuit. MLBC (Multi Level Boost Converter) have more advantages with low voltage input change to high voltage output. The Principle of MLBC is like the Boost Converter, but they have high ratio conversion without adding transformation for step up the voltage, the setting Output will stabilize if they always get the minimum input range for reduce the drop voltage from input who used Solar Panel, it is used MISO (Multiplied Input Single Output), the MISO contains Solar Panel and Battery with the parallel circuit set. DC Micro Grid using as DC BUS for distributed the voltage from the source to load for the maximum output power it used 100-200 Watt. The Method of control voltage it used PI - Ziegler Nichols-1 for controlled the Multi Input Single Output (MISO) block, the first control used to make the input of MLBC stabilize for 30 - 40 V being step up to 200 - 250 Volt. The Load of DC BUS example: Inverter, 3 Phase Motor, Led DC, Battery Energy Storage at this project used a inverter with 3 phase motor for load of converter. The Maximum Output Power from a design of this converter is 234.87 Watt according the DC load and the efficiency of converter is maximum 86 %.

Locating and Sizing of Distributed Generation Sources and Parallel Capacitors Using Multiple Objective Particle Swarm Optimization Algorithm

In this paper, the MOPSO algorithm has been used to locate and determine the capacity of distributed generation sources and capacitor banks in the distribution system. The intended objective function is a combination of different objective functions. The first goal is to reduce losses, and the second goal is to improve the voltage profile and the third goal is to reduce costs, which has been used by placing weight coefficients in the form of an objective function in the algorithms. For this purpose, the standard 33-bus system has been used to conduct studies. Studies have been repeated in three scenarios. In the first scenario, the locating and determination of the capacity of active and reactive resources has been accomplished with the approach of reducing losses and improving the voltage profile. However, in the second scenario, the locating and determining the capacity of these resources has been accomplished with loss and cost reduction approach and it was considered as constraint in voltage profile. In the third scenario, the simultaneous reduction of all three objective functions has been performed simultaneously. To validate the results obtained by the MOPSO algorithm, its results were compared with genetic and particle swarm algorithms. The results indicate better and more accurate performance of MOPSO algorithm in minimizing objective functions relative to other two algorithms.

강압형 LCC 공진형 컨버터의 기생 인덕턴스로 인한 주파수-출력 특성 변화 관찰

In the practical LCC resonant converter, the parasitic inductance between the parallel resonant capacitor and the output stage on the secondary side of the transformer is one of various parasitic components. The parasitic inductance induces relatively substantial influences in the step-down LCC resonant converter for which the rated output voltage is lower than the input voltage, and this cause additional resonance. In addition, when the parasitic is not affected, the switching frequency and output have a constant inverse relationship when switching frequency is above the resonant frequency, but the influence of the parasitic inductance cause a variation in the frequency-output characteristic. This paper describes the observations on the variations of major waveform and frequency-output characteristic with or without parasitic inductance using PSPICE simulation of the LCC resonant converter whose input voltage is 44V and rated output voltage is 17V.

Synthesis and study of the structural and dielectric properties of La0.67Ca0.2Ba0.13Fe1−xMnxO3 ferrites (x = 0, 0.03 and 0.06)

The La0.67Ca0.2Ba0.13Fe1−xMnxO3 perovskite compounds with different manganese concentrations (x = 0.0, 0.03, 0.06) were synthesized by the autocombustion method and annealed at 700 °C. The X-ray diffraction (XRD) data indicated that all obtained compounds crystallize in the cubic structure with the Pm $$\overline{3}$$ m space group. The increase in the substitution rate has been found to lead to the decrease in the crystallite size value characterized by X-ray diffraction. The dielectric properties of these samples, using a complex impedance spectroscopy technique, were also performed as a function of frequency and temperature. A suitable equivalent electrical circuit was used to assess the contributions of electrode, grains, and grain boundaries in the complex impedance results. Activation energies were determined from different methods. Nyquist plots were consistent with three circuits in series, each one with a capacitance in parallel with a resistance. The conduction mechanism follows the NSPT model for the three samples at T < 280 K, in which the rise in substitution rate increases the binding energy of carriers. Above 280 K, the appropriate model is the Correlated Barrier Hopping (CBH) for x = 0, while the overlapping large polaron tunneling (OLPT) process has been confirmed for both samples x = 0.03 and x = 0.06. Our compounds have high electrical properties, and good thermal and chemical stability. They are susceptible to many technological applications, such as gas sensors, capacitors, filters, resonators, new read heads, and solid oxide fuel cells.

Process for generating high purity synthesis gas hydrogen from heavy oil or hydrocarbons.

Capacitance sensor is a non-intrusive devices used for the void fraction measurement in two-phase flows. Capacitance sensor is formed by two electrodes placed at the outside walls of a dielectric pipe, through which a two-phase medium flows. The capacitance of the sensor depends on the geometric arrangement of electrodes and distribution of the electrical field, which depends on the electrical permittivity of the medium around the electrodes and in the pipe. For a two-phase gas–liquid​ flow, the effective permittivity of dielectric between the electrodes varies due to the variation in the percentage of gas and liquid in the pipe. In this paper, the variation of sensor capacitance were determined numerically for the annular-flow pattern. The capacitance was calculated by the integration of electric field distribution around two symmetrical concave electrodes in the form of cylinder fragments using the Gauss law. This shape of electrodes was chosen because the sensitivity of this type of sensor is the highest, and is the most often used in practice. The results of numerical simulations were compared with experimental results. The capacitance changes due to void fraction variation were determined experimentally by the method of frequency deviation. It was noticed that regardless of complex geometry of the electric field between two concave electrodes, the electric field lines within the pipe walls do not deviate much from the parallel distribution. From the simulations for various arc lengths of the electrodes resulted that the changes of relative capacitance of the sensor are almost the same for all arc lengths, although the absolute value of capacitance of the sensor depends on this arc length of the electrodes. The numerical results on electric field distribution for annular flow also indicated that the model of two parallel capacitances, representing the liquid and gas phases, usually assumed in various papers as the most consistent with experimental results, can be used for the representation of two separate phases in two-phase flows.

Effect of void fraction on capacitance of sensor for void fraction measurement

Capacitance sensor is a non-intrusive devices used for the void fraction measurement in two-phase flows. Capacitance sensor is formed by two electrodes placed at the outside walls of a dielectric pipe, through which a two-phase medium flows. The capacitance of the sensor depends on the geometric arrangement of electrodes and distribution of the electrical field, which depends on the electrical permittivity of the medium around the electrodes and in the pipe. For a two-phase gas–liquid​ flow, the effective permittivity of dielectric between the electrodes varies due to the variation in the percentage of gas and liquid in the pipe. In this paper, the variation of sensor capacitance were determined numerically for the annular-flow pattern. The capacitance was calculated by the integration of electric field distribution around two symmetrical concave electrodes in the form of cylinder fragments using the Gauss law. This shape of electrodes was chosen because the sensitivity of this type of sensor is the highest, and is the most often used in practice. The results of numerical simulations were compared with experimental results. The capacitance changes due to void fraction variation were determined experimentally by the method of frequency deviation. It was noticed that regardless of complex geometry of the electric field between two concave electrodes, the electric field lines within the pipe walls do not deviate much from the parallel distribution. From the simulations for various arc lengths of the electrodes resulted that the changes of relative capacitance of the sensor are almost the same for all arc lengths, although the absolute value of capacitance of the sensor depends on this arc length of the electrodes. The numerical results on electric field distribution for annular flow also indicated that the model of two parallel capacitances, representing the liquid and gas phases, usually assumed in various papers as the most consistent with experimental results, can be used for the representation of two separate phases in two-phase flows.

A dual-mode successive approximation register analog to digital converter to detect malicious off-chip power noise measurement attacks

An on-chip noise monitor using a dual-mode analog to digital converter (ADC) is developed to detect the insertion of off-chip components as malicious attempts of power noise measurement attacks. A two-step sampling scheme selecting either synchronous or asynchronous clocking enables both real-time monitoring and high-resolution diagnosis of power supply noise, respectively. The monitor detects the change in power-line impedance and assumes the happening of physical contacts by an attacker’s device. A wide-band ADC with the bandwidth of 1 GHz facilitates the analysis of on-chip captured waveforms and the recognition of potentially inserted devices. Fabricated in 65 nm CMOS, the on-chip noise monitor is examined for the detectability of series resistors as well as parallel capacitors that are intentionally inserted on power lines. The experiments demonstrated the detection of a power current sensor in series to power lines, and also the attachment of an oscilloscope probe, through the analysis of on-chip captured power noise waveforms.

Rapid detection of catechins during black tea fermentation based on electrical properties and chemometrics

Catechins are important to evaluate the quality of black tea. In this study, a quantitative prediction model was established based on the measurement of electrical properties and a chemometrics method to detect the catechin content in fermented black tea. The effects of different preprocessing, variable screening methods, and nonlinear algorithms on the model were studied. Results show that the electrical parameters most sensitive to catechin content are equivalent parallel capacitance, loss factor, and reactance mainly at low frequencies (0.05–0.1 kHz). Normalization processing (Zscore), variable combinations' population analysis and the iterative retained information variable algorithm (VCPA-IRIV), and the nonlinear intelligent algorithm random forest (RF) can all effectively improve the performance of a catechin prediction model. In the VCPA-IRIV-RF model, the number of introduced variables was reduced from 162 to 9 with a compression ratio of 94.5%; the root mean square error of prediction and the root mean square error of validation of this model were only 0.269 and 0.214, respectively. The predictive correlation coefficient, correlation coefficient of calibration, and residual predictive deviation increased to 0.988, 0.994, and 5.47, respectively, indicating the good performance of the model. The rapid and nondestructive determination of catechin content in black tea fermentation using a method to detect the electrical properties seems to be practical.

Parallel Hybrid Converter-Based STATCOM and Capacitor Voltage Control Technique

The parallel-hybrid converter (PHC) is a promising high-power topology. Smaller capacitor size, lower capacitor and switch counts, and low-energy storage requirement are some of its important features. However, it requires a large dc-filter inductor to filter the dc-side harmonics. Moreover, since its dc and ac sides are strongly coupled, only a single stable operating point in terms of a fixed modulation-index (MI) value is possible. Even with an additional dedicated control effort, the obtained MI variation remains still limited. This article proposes the PHC-static compensator (STATCOM) configuration that eliminates the dc-filter inductor requirement and can also operate at any MI value without necessitating additional control efforts. A detailed power analysis of the PHC-STATCOM for balanced and unbalanced grid conditions (UGCs) is performed in this article. A new control technique for PHC-STATCOM is proposed, which effectively balances the capacitor voltages of its chain-links even during UGCs. The energy storage requirement of PHC-STATCOM is evaluated to obtain the capability curve and determine its capacitor size. The PHC-STATCOM is compared with the popular STATCOM configurations in terms of the capacitor and switch counts. The proposed principles of PHC-STATCOM for several three-phase balanced and UGCs are verified using simulation and experimental studies.

Comparison between Thyristor Switched Series Capacitors and Thyristor Switched Parallel Capacitors for wind power systems - A Simulation Study

This paper compares by simulation the Thyristor Switched Series Capacitors (TSSC) Circuit with the Thyristor Switched Parallel Capacitors (TSPC) Circuit for wind turbines. The well-known TSSC circuit belongs to the Controlled Series Capacitor (CSC) circuits that have been used in power transmission lines in order to correct the power factor and improve the performance of the electrical system. Such a circuit can be used in wind power systems to improve and maximize the efficiency of a wind turbine. A typical direct-drive wind power system employs variable speed electric generators, but the downside is that systems like that suffer from high inductive reactance. A TSSC circuit, therefore, is able to counteract for any reactive losses, and improve the power factor as well as the efficiency. The main issue with the TSSC circuit is the use of a high number of capacitors that must be connected in series, which can increase the cost and the maintenance of the controller. This paper introduces a novel circuit with different control technique than the TSSC that employs capacitors in parallel configuration. The novel TSPC circuit was simulated in PSPICE and the benefits as well as the drawbacks are described

Low-loss bidirectional buck-boost DC-DC converter

For DC energy systems there is reversible buck/boost pulse converter (RPC) in the classic converter circuit. The maximum efficiency of the RPC without additional mechanisms to reduce the dynamic energy losses in the power semiconductor keys (PSK) during their commutation is about 92%. Improved efficiency is achieved by providing «soft switching» of the transistors RPC, i.e. in zero current/voltage switching. These methods require the introduction of supporting links in the RPC, which have a negative impact on the performance of reversible buck/boost pulse converter. Due to the increase in the number of components, this leads to degradation of mass-size characteristics of the product and decrease in its reliability. New RPC transistors control algorithm RPC provides an opportunity to use transistors at zero voltage without additional elements. Because of the relative novelty of this technical solution, the energy exchange processes in the reactive elements of power semiconductor devices (PSD) are poorly studied. By reason of insufficient studying of power exchange processes in reactive elements of converter, it seems important to study these processes and use the received results for recommendations about reversible buck/boost pulse converter designing. As a result of research it was found out that the recuperation of energy stored in parasitic capacitance of drain-source transistors acting as PSD. At designing of RPC the account of the revealed phenomenon of energy, recovery will allow additionally to raise its efficiency at the expense of decrease in losses of energy on PSK in shutdown state. For this purpose, it is necessary to use transistors with high value of parasitic capacitance of drain-source or include additional capacitors in parallel with PSK.

A Plethysmography Capacitive Sensor for Real-Time Monitoring of Volume Changes in Acute Heart Failure

A small, wearable, low-weight, and low-power-consumption device for plethysmography capacitive sensing is proposed herein. The device allows carrying out real-time monitoring of leg volume changes in patients suffering from heart failure (HF) conditions. The dynamic of fluid overload in patients with acute HF serves as a prognosis marker for this type of severe disease and, consequently, these patients can benefit from a wearable monitoring system to measure their body volume evolution during and after hospitalization. Our approach is based on contactless capacitive wearable structures implemented by two different sensor realizations located in the ankle: 180°-parallel capacitor plates (two modes of operations are compared, with the patient’s body connected to ground and to the average voltage between plates) and planar-parallel capacitor plates whose overlapped surface varies with the volume of the patient’s leg. Both realizations exhibit good sensitivity to leg volume changes. The acquisition of capacitance values is performed via a simple circuit that achieves notable performance in simulated volume analysis. A preliminary pilot clinical prototype is described as well.