Low-voltage Capacitor Research Articles

Development of an efficient pulsed magnet for improvement of inertial electrostatic confinement fusion

In this paper thin Aluminum strip has been used to construct a low resistance low inductance magnet. This new magnet has relatively high bore diameter designed for magnetization of plasma in small sized fusion neutron generators; e.g. electrostatic confinement devices. This magnet enables us to use 900 Volts/33 mFarad capacitor bank. The small sized and comparatively low voltage capacitors are able to produce more than 2400A current to produce more than 2 Tesla magnetic field inside the 11 cm diameter bore without any coolant. The maximum current density for this coil was measured as 12 kA/cm2 that lasts for about 60 ms (with rise time of 7.5 ms). This relatively low current density decreases the destructive magnetic stress. Analytical and simulation results of the magnetic field profile and the experimental performance of the magnet are described in the paper.

A Novel Seven-Level Hybrid-Clamped (HC) Topology for Medium-Voltage Motor Drives

This letter proposes a novel seven-level (7L) hybrid-clamped converter, which has competitive performance and lower device count compared to existing topologies. It can easily balance the floating capacitor voltage at the switching frequency, and therefore ensure low capacitor voltage ripples even under very low fundamental frequencies. Both multipulse diode front-end and active front-end structures can be used with the proposed 7L converter, where the 7L active front end has the ability to balance the dc-link capacitors. The proposed 7L converter is very suitable for medium voltage drives (4.16 to 6.6 kV) that feature low costs, high-performance, and low-speed operation capability. Simulation and experiment results are obtained to verify the feasibility of the proposed topology.

An Integrated 3-mW 120/230-V AC Mains Micropower Supply

The maintenance issue of batteries and the limited power level of energy harvesting is addressed by the presented integrated micropower supply. Connected to the 120/230- $\text {V}_{\text {RMS}}$ mains, it provides a 3.3-V ac output voltage, suitable for applications such as the Internet-of-Things and smart homes. The micropower supply consists of a fully integrated ac–dc and dc–dc converter with one external low-voltage surface mount device buffer capacitor, resulting in an extremely compact size. Fabricated in a low-cost 0.35- $\mu \text {m}~700$ -V complimentary metal-oxide-semiconductor technology, it covers a die size of 7.7 mm2. The ac–dc converter is a direct coupled, full-wave rectifier with a subsequent series regulator. The dc–dc stage is a fully integrated capacitive 4:1 converter with up to 17-V input and 47.4% peak efficiency. The power supply comprises several high-voltage control circuits including level shifters and various types of charge pumps (CPs). A source-supplied CP is utilized that supports a varying switching node potential. The overall losses are discussed and optimized, including flying capacitor bottom-plate losses. The power supply achieves an output power of 3 mW, resulting in a power density of 390 $\mu \text {W}/ \text {mm}^{2}$ . This exceeds prior art by a factor of 11.

Digital Fuzzy Current Mode Controlled Integrated PFC Converter with External Ramp Compensation

This paper propounded a novel method of design and realization of a digital fuzzy controlled buck integrated power factor correction (PFC) converter. It derives its advantages through the low buck capacitor voltage and single control switch (SW1), which leads to reduced complex control and price. Sub-harmonic oscillations generated in the peak current mode technique can be nullified by using the ramp signal, thereby improving the overall performance of the converter. The fuzzy logic controller (FLC) is robust and effective than the conventional linear controllers like P, PI, PID. In this paper, the digital fuzzy current mode controlled integrated PFC converter with external ramp compensation signal for 100 W load operating in the universal range of voltage (90[Formula: see text]V–265[Formula: see text]V), 50[Formula: see text]Hz has been designed and implemented using MATLAB/Simulink, verified in hardware using the TMS320F2812 digital processor board, and the results are found to be complying with international regulatory standards (IEC 6100-3-2 and IEEE 519-1992).

Modified hybrid modulation strategy with power balance control for H‐bridge hybrid cascaded seven‐level inverter

Compared with the traditional cascaded H-bridge multi-level inverters, the hybrid cascaded multi-level inverters have been receiving attention because they can generate more levels with the same number of power cells. However, with the general hybrid pulse width modulation (PWM), the output power distribution between the high-voltage and low-voltage H-bridge cells is extremely uneven in low amplitude modulation, and it may appear that the high-voltage cell feeds power into the low-voltage cell in some modulation ratio intervals causing the low-voltage cell capacitor voltage boost. To avoid this problem, a method of a modified hybrid PWM strategy with power balance control is proposed. It has achieved the output power balance of H-bridge cells in full amplitude modulation, the occurrence of the phenomena of extremely uneven output power distribution between the high- and low-voltage cells in low amplitude modulation is avoided, and the performance of the inverter is improved. Simulation and experimental results verify the correctness and feasibility of the proposed strategy.

Hybrid Bidirectional DC–DC Converter With Low Component Counts

In this paper, a hybrid bidirectional dc–dc converter is presented, which is a combination of a switched-capacitor converter and an inductor-based converter with low component counts. The input current ripple and peak charging current are small with the help of the inductor. The proposed converter is applicable in the battery charge/discharge systems, such as the distributed renewable energy systems, battery equalizer, auxiliary power supplies, traction drive system, and dual-voltage automotive systems based in new electrical architecture concept, where common ground is not required and within the voltage-gain range of 2–6. A comprehensive analysis of the steady-state operation, small-signal model, and component stress is given. The comparison with an alternative topology shows the advantages of low component counts, low total capacitor voltage stress, low inductor current, and low total active switch stress for the 42/14 V voltage level. A 42/14 V prototype rated at 20–120 W with a peak efficiency of 97.8% in boost mode and 97.62% in buck mode was built to verify the analysis.

Fuzzy peak current controlled integrated PFC convert-er with slope compensation

This propounded a novel method of design and implementation of a fuzzy peak current mode (PCM) controlled Buck Integrated Power Factor Correction (PFC) Converter with compensation ramp. It derives its advantages through low buck capacitor voltage and single control switch, which leads to reduced complex control and price. Sub-harmonic oscillations generates in peak current controller can be nullified by using ramp signal, there by improves the overall performance of the converter. The fuzzy controller (FLC) robust and effective than conventional linear controllers like P, PI, PID, hence in this work a (90 – 265V), 50Hz AC, 48V DC and 100 kHz frequency converter is implemented in MATLAB/Simulink software and results are presented. Results show that converter meets international regularity commission regulations.

Fuzzy LPCM controlled buck integrated PFC convert-er for Class-C&D appliances

This propounded a novel method of design and implementation of a fuzzy linear peak current mode (LPCM) controlled Buck Integrated Power Factor Correction (PFC) Converter. It derives its advantages through low buck capacitor voltage and single control switch, which leads to reduced complex control and price. Sub-harmonic oscillations generates in peak current controller can be nullified by using ramp signal, there by improves the overall performance of the converter. The fuzzy controller (FLC) robust and effective than conventional linear controllers like P, PI, PID, hence in this work a (90 – 265V), 50Hz AC, 48V DC and 100 kHz frequency converter is implemented in MATLAB/Simulink software and results are verified experimentally. Results show that converter meets international regularity commission regulations.

A Branch Current Reallocation Based Energy Balancing Strategy for the Modular Multilevel Matrix Converter Operating Around Equal Frequency

The modular multilevel matrix converter (M3C) is a promising topology for medium-voltage, high-power applications. Due to the modular structure, it is scalable and capable to produce high quality output waveforms and can be fault tolerant. However, the M3C suffers from low frequency capacitor voltage fluctuation if the output frequency is close to the input voltage frequency, which limits its application in adjustable speed drive fields. This paper presents a theoretical analysis in the phasor domain to find the branch-energy equilibrium point of the M3C when operating with equal input and output frequency first. Then, a branch energy balancing control method based on branch current reallocation is proposed to equalize the energy stored in the nine converter branches. With the proposed method, the M3C can effectively suppress the capacitor voltage fluctuation without injecting common-mode voltage or applying reactive power to the input side. Experimental results are presented to validate the proposed method.

Single‐phase bidirectional ac/dc converter for plug‐in electric vehicles with reduced conduction losses

Here, a non-isolated-based single-stage integrated bidirectional converter has been proposed for plug-in electric vehicles, which has the capability to achieve all modes of vehicle operation, i.e. plug-in charging, propulsion, and regenerative braking. This integrated converter has improved efficiency of 2-2.5% in propulsion boost and regenerative braking buck modes over existing non-isolated integrated converters which leads to a long run of vehicle and saves the electricity usages. Despite the proposed converter has two inductors, the size of the second inductor is approximately reduced by 35-40% compared with single-inductor converters. A detailed loss analysis of the proposed converter is investigated in propulsion boost and regenerative buck modes. Further, the design considerations of passive components are presented to achieve continuous conduction operation in each mode as well as low capacitor voltage ripple. Experimental results confirm the effectiveness of the proposed converter.

Measurement Error Estimation for Capacitive Voltage Transformer by Insulation Parameters

Measurement errors of a capacitive voltage transformer (CVT) are relevant to its equivalent parameters for which its capacitive divider contributes the most. In daily operation, dielectric aging, moisture, dielectric breakdown, etc., it will exert mixing effects on a capacitive divider’s insulation characteristics, leading to fluctuation in equivalent parameters which result in the measurement error. This paper proposes an equivalent circuit model to represent a CVT which incorporates insulation characteristics of a capacitive divider. After software simulation and laboratory experiments, the relationship between measurement errors and insulation parameters is obtained. It indicates that variation of insulation parameters in a CVT will cause a reasonable measurement error. From field tests and calculation, equivalent capacitance mainly affects magnitude error, while dielectric loss mainly affects phase error. As capacitance changes 0.2%, magnitude error can reach −0.2%. As dielectric loss factor changes 0.2%, phase error can reach 5′. An increase of equivalent capacitance and dielectric loss factor in the high-voltage capacitor will cause a positive real power measurement error. An increase of equivalent capacitance and dielectric loss factor in the low-voltage capacitor will cause a negative real power measurement error.

Three‐level neutral‐point‐clamped quasi‐Z‐source inverter with reduced Z‐source capacitor voltage

A new three-level neutral-point-clamped quasi-Z-source inverter topology is proposed. The topology can effectively reduce the Z-source network capacitor voltage stress and inhibit the start inrush current, thus low-voltage capacitors can be selected to reduce the volume and cost of the inverter. In addition, the changed structure will not affect the boost ability and all existing modulation methods can be used directly. The proposed topology is validated by simulations.

Effect of the ion-beam bombardment and annealing temperature on sol-gel derived yttrium aluminum oxide film as liquid crystal alignment layer

We demonstrated a homogeneous liquid-crystal (LC) alignment state on yttrium aluminum oxide (YAlO) films, where the alignment was induced by ion-beam (IB) irradiation. Topographical analysis was performed by atomic force microscopy as a function of annealing temperature. Higher annealing temperatures yielded a smoother surface, accompanied by reduced light scattering. Transparency in the visible region increased on the surface fabricated at higher annealing temperatures. LC alignment mechanism was determined by X-ray diffraction (XRD) analysis. Moreover, IB-irradiated YAlO films annealed at temperatures greater than 200 °C exhibited good thermal stability and low capacitance–voltage hysteresis. The IB-irradiated YAlO films are suitable as alternative alignment layers in advanced LC display applications.

DSP based current controlled single stage single phase integrated converter with external compensating signal for Class-C & Class-D appliances

AbstractDesign and implementation of a current controlled single stage single phase integrated AC/DC isolated Power Factor Correction (PFC) converter is presented in this paper. With the integrated topology reduces the number control switches. The proposed converter has the advantage of low bulk capacitor voltage and only single control switch hence reduce in complexity in control and cost. Sub-harmonic oscillations which are produced in conventional current controller. By adding an external compensating signal effect of oscillations are reduced and performance of the converter is improved. The proposed scheme is implemented in real time by TMS320F2812 digital signal processor (DSP) board. The performance of converter is verified both experimentally and by simulation at different load and line conditions. The proposed converter is designed for 90–230 V, 50 Hz AC input, 48 V DC output and operating at 100 kHz switching frequency. The Experimental results shows that the DSP-based fuzzy controlled single pha...

A Three-Level Dodecagonal Space Vector-Based Harmonic Suppression Scheme for Open-End Winding IM Drives With Single-DC Supply

This paper presents a harmonic elimination technique based on a three-level dodecagonal space vector structure for open-end winding induction motor (IM) drives with a single-dc supply. Advantages of dodecagonal space vector switching and multilevel inverters are achieved with a single-dc supply. A dc supply-fed three-level flying capacitor (FC) inverter feeds active power to one end of the IM winding terminals and H-bridge connected capacitors eliminate fifth- and seventh-order harmonics from the other end. A pulsewidth modulation (PWM) technique is developed to switch the three-level dodecagonal space vectors and simultaneously control the H-bridge capacitors at $0.1445V_{\text{dc}}$ . The fifth- and seventh-order harmonics are eliminated for the full modulation range of the three-level FC inverter, including the extreme 6-step operation. An increase in the linear modulation range has been achieved, resulting in improved dc bus utilization. Harmonic elimination is achieved by increasing switching frequency of the low-voltage capacitor connected H-bridge inverter; thus, switching frequency for the high-voltage dc supply-fed FC inverter is not increased. Using the proposed scheme, the instantaneous phase voltage never exceeds $\frac{2}{3}V_{\text{dc}}$ (maximum phase voltage applied for hexagonal space vector structure) for which the machine windings are rated. Additionally, the proposed inverter has also been shown to operate for field oriented control of the open-end winding IM drive.

Epitaxially grown crystalline Al2O3 interlayer on β-Ga2O3(010) and its suppressed interface state density

Al2O3 films were deposited on β-Ga2O3(010) and β-Ga2O3 substrates by atomic layer deposition at 250 °C, and their interface state densities (Dit) at shallow energies were evaluated using a high–low capacitance–voltage (C–V) method. Al2O3/β-Ga2O3(010) showed lower Dit values (5.9 × 1010 to 9.3 × 1011 cm−2 eV−1) than Al2O3/β-Ga2O3 (2.0 × 1011 to 2.0 × 1012 cm−2 eV−1) in an energy range of −0.8 to −0.1 eV. Cross-sectional transmission electron microscopy analysis indicated the formation of a uniform amorphous Al2O3 layer on the β-Ga2O3 substrate. In contrast, a crystalline Al2O3 interlayer with a thickness of 3.2 ± 0.7 nm with an amorphous Al2O3 top layer was formed on the β-Ga2O3(010) substrate, which effectively decreased Dit. Moreover, thicker interlayers showing lower Dit values at deep state levels were formed at deposition temperatures higher than 100 °C, which were evaluated by shifts in the C–V curves.

Single-Stage Bridgeless AC–DC PFC Converter Using a Lossless Passive Snubber and Valley Switching

A single-stage bridgeless ac–dc PFC converter using a lossless passive snubber and valley switching is proposed. The proposed converter is based on a two-stage bridgeless boost-flyback converter. In the proposed converter, the conduction losses are reduced by removing an input full-bridge diode rectifier. The boost inductor is designed to be operated in the discontinuous–conduction mode for achieving high power factor. In the flyback module, the couple inductor that provides input–output electrical isolation for safety is designed to be operated in the critical-conduction mode for low RMS current and low turn-on switching loss by using valley-switching operation. Because of the lossless snubber circuit, the voltage spike of switch is clamped, and the leakage inductor energy is recycled. The snubber capacitor is used as a dc-bus capacitor, which is divided into two capacitors. In addition, some input power is directly conducted to the output, and the remaining power is stored in dc-bus capacitor. So, low-voltage rating capacitors can be used as the dc-bus capacitor and power transfer efficiency is improved. The presented theoretical analysis is verified on an output 48-V and 60-Wexperimental prototype.

DC-Link Voltage Balance Control in Three-phase Four-wire Active Power Filters

The three-phase four-wire shunt active power filter (APF) is an effective method to solve the harmonic problem in three-phase four-wire power systems. In addition, it has two possible topologies, a four-leg inverter and a three-leg inverter with a split-capacitor. There are some studies investigating DC-link voltage control in three-phase four-wire APFs. However, when compared to the four-leg inverter topology, maintaining the balance between the DC-link upper and lower capacitor voltages becomes a unique problem in the three-leg inverter with a split-capacitor topology, and previous studies seldom pay attention to this fact. In this paper, the influence of the balance between the two DC-link voltages on the compensation performance, and the influence of the voltage balance controller on the compensation performance, are analyzed. To achieve the balance between the two DC-link capacitor voltages, and to avoid the adverse effect the voltage balance controller has on the APF compensation performance, a new DC-link voltage balance control strategy for the three-phase four-wire split-capacitor APF is proposed. Representative simulation and experimental results are presented to verify the analysis and the proposed DC-link voltage balance control strategy.

Switched-Mode Active Decoupling Capacitor Allowing Volume Reduction of the High-Voltage DC Filters

This paper describes active shunt LC decoupling circuit with ceramic capacitors, allowing volume reduction and lifetime improvement of the high-voltage dc filters. Active filtering is based on the energy exchange between high-voltage coupling and low-voltage auxiliary capacitors. The coupling capacitor enables use of the low-voltage switched-mode power stage and low-voltage auxiliary decoupling capacitor. Advantageously, this allows to reduce power dissipation, switching frequency ripple current, and to reduce volume of the circuit. Additionally, power efficiency and capacitor lifetime are improved by using recent high-voltage coupling multilayer ceramic capacitors, reaching very low ESR. This paper provides description of the active decoupling capacitor, and shows an example of the feedback control. Obtained performances are demonstrated on the prototype of 1300-μF/450-V capacitor, allowing to reduce volume by three, when compared to ordinary 450-V electrolytic capacitor.

Design OF FPEZ-Source Network with Reduced Switches FED Induction Motor

This Project deals with an fully parallel Embedded Z-source inverter(FPEZ) to control the three phase induction motor. Z-Source inverter is a single-stage converter which performs both buck-boost energy conversions using the LC impedance network. The further advancement in the Z-Source inverter is the partially parallel Embedded ZSource(PPEZS) inverter that can produce same gain as Z-Source inverter but with lower capacitor voltage and ripples . In order to overcome the drawbacks of PPEZS, Fully parallel EZ-(FPEZS) Source inverter is proposed. The proposed inverters provide a high boost voltage inversion ability, a lower voltage stress across the active switching devices and capacitors with a continuous input current. In addition, they can suppress the startup inrush current, which otherwise might destroy the devices. The proposed system reduces six switch three phase inverter to four switch three phase inverter. This makes system compact which reduces cost and switching losses, line harmonics, improves power factor, reliability and extends the output voltage range. The system is modeled using Proteus and Simulink simulation. This paper presents the operating principles, analysis, and simulation results of FPEZ Source inverter. Keyword: Boost inversion ability, Buck-boost ,Embedded Z source, Motor drives, PEZS, PWM, voltage boost, Z Source Inverter.