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When a fault occurs on the dc side of the voltage source converter based high voltage direct current (VSC-HVDC) transmission system, the fault current rises quickly due to the low damping of the dc system. Using a dc fault current limiter (DC-FCL) to limit the rise of the fault current can significantly reduce the breaking requirements of the DCCB. A topology of a bidirectional active dc fault current limiter (BA-FCL) based on coupled inductor is proposed in this paper. No expensive full-controlled power electronic devices are used in this topology. Only a few half-controlled power electronic devices are used to achieve active control of the current limiting unit. Compared with many topologies of current limiter at present, the fault current limiting effect of BA-FCL is improved significantly while the cost, volume, topology complexity, and control complexity are reduced. The stress analysis and parameter design of the proposed current limiter are carried out. Finally, the simulation case study and hardware experiment are implemented to verify the good economy and current limiting performance of the proposed topology. [ABSTRACT FROM AUTHOR]

The capacitor energizing transient as a kind of typical disturbance is used in the studies of power quality, condition monitoring, and other fields, and all studies heavily rely on transient characteristics. However, most characteristics are established based on the three-phase capacitor synchronous energizing (SE), and the effect of asynchronous energizing (AE) is neglected, which may affect the relevant studies. In this paper, the main characterizations of the capacitor AE transient, such as the oscillation frequency, time constant, and transient magnitude are analyzed considering the operation modes of the system and capacitor neutral points. The effect of the three-phase circuit asymmetry on the characterizations is investigated. The downstream voltage magnification phenomena in not only positive-sequence circuit but also zero-sequence circuit caused by the capacitor AE are also revealed. The theoretical analysis, computer simulation and lab experiment results have verified the effectiveness of the characteristics. [ABSTRACT FROM AUTHOR]

In this paper, fully inkjet printed multilayer capacitors and inductors are fabricated and characterized using poly 4-vinylphenol (PVP) ink as the dielectric layer and silver nanoparticle ink as the conductor. Inkjet printed through vias, created with a novel dissolving method are used to make RF structures in a multilayer inkjet printing process. The vias have been realized in a 350-nm PVP film and exhibit resistance better than 0.1 $\Omega $ . Spiral inductors from 10 to 75 nH have been realized with maximum quality factors around five. The 10-nH inductor exhibits a self-resonant frequency slightly below 1 GHz. Metal–insulator–metal capacitors are realized with densities of 50 pF/mm ^{2} . These capacitors demonstrate values ranging from 16 to 50 pF. The 16-pF capacitor shows a self-resonant frequency over 1.5 GHz. The successful implementation of inductors and capacitors in an all inkjet printed multilayer process with vias is an important step toward fully inkjet-printed large area and flexible RF systems. [ABSTRACT FROM AUTHOR]

Aluminum electrolytic capacitors are standard components in power electronic equipment. Their performance and lifetime strongly depend on their operation temperature. Hence, controlling their temperature is essential for the reliable operation of the equipment. For standard snap-in type capacitors, which are common in low-power converters ( < \sim20 kW), direct air cooling is the standard solution. This paper presents ways to improve the cooling performance by attaching the capacitor to a heat sink. Two different configurations are investigated: heat removal through the base of the capacitor and heat removal through its sidewalls. When applied with an aluminum heat sink in natural convection, both methods provide significantly reduced thermal resistances, approximately 57% lower compared to direct air cooling by natural convection. [ABSTRACT FROM PUBLISHER]

Capacitor sizing is a crucial step when designing charge-scaling digital-to-analog converters (DACs). Larger capacitor size can achieve better circuit accuracy and performance due to less impact from process gradient, parasitic mismatch, and local variation. However, it also results in larger chip area and higher power consumption. The size of binary-weighted capacitors in charge-scaling DACs is highly sensitive to the routing parasitics. Unmatched routing parasitics among binary-weighted capacitors will lead to large capacitor size for satisfying circuit accuracy and performance. Previous work focuses on the study of generating high-quality common-centroid placement of unit capacitor arrays while ignoring routing parasitics. None of them address the sizing of binary-weighed capacitors. This paper presents the first problem formulation in the literature which simultaneously considers capacitor sizing and parasitic matching during common-centroid capacitor layout generation such that the power consumption is minimized while the circuit accuracy/performance is also satisfied. Experimental results show that the proposed approach can achieve very significant chip area and power reductions compared with the state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

In this paper, we describe an ultrasensitive differential capacitive dilatometer (ΔL/L ~ 10−9) and novel ratiometric measurement method in the temperature range of 1.9 K < T < 400 K for the investigation of thermal expansion and magnetostriction of single crystal as well as polycrystalline samples. The dilatometer provides a capacitive measurement based on a differential capacitance or the capacitance ratio measured between two parallel plate capacitors of the dilatometer. In this regard, an absolute capacitance bridge is not required, and even more advantageously, the effect of adsorbed gas on the capacitor plates is greatly reduced compared to conventional dilatometers. The differential capacitive dilatometer provides a symmetrical configuration which reduces the effect of temperature gradients. The capabilities of the dilatometer are demonstrated by the measurement of magnetic ordering of a URu2Si2 sample, and of de Haas–van Alphen oscillations in an aluminum sample. [ABSTRACT FROM AUTHOR]

The development of new sensing platforms could offer exciting opportunities for healthcare and environmental applications. In the last few decades, sensor device configurations have been limited owing to the use of electrochemical electrodes, resistors, and transistors. Capacitors are widely used for constructing various electronic devices. Here, we report for the first time the construction of a transparent interdigital transparent capacitor and its use for sensing ethanol. When the ethanol concentration changes, the dielectric properties of the capacitor change, resulting in the response of the impedance and capacitance. The capacitor shows a detection range of 0.1–1 volume fraction. It is expected that this paper could open up new opportunities for fundamental studies of more complex sensor configurations with a capacitor as one of the components and advance related healthcare and environmental applications. [ABSTRACT FROM AUTHOR]

Reliability analysis is an important tool for assisting the design phase of a power electronic converter to fulfill its life-cycle specifications. Existing converter-level reliability analysis methods have two major limitations: 1) being based on constant failure rate models; and 2) lack of consideration of long-term operation conditions (i.e., mission profile). Although various studies have been presented on power electronic component-level lifetime prediction based on wear-out failure mechanisms and mission profile, it is still a challenge to apply the same method to the reliability analysis of converters with multiple components. Component lifetime prediction based on associated models provides only a $B_{X}$ lifetime information (i.e., the time when X% items fail), but the time-dependent reliability curve is still not available. In this paper, a converter-level reliability analysis approach is proposed based on time-dependent failure rate models and long-term mission profiles. Two different methods to obtain the component-level time-to-failure are illustrated by a case study of dc/dc converters for a 5 kW fuel cell-based backup power system. The reliability analysis of the converters with and without redundancy is also performed to assist the decision making in the design phase of the fuel cell power conditioning stage. [ABSTRACT FROM AUTHOR]

A quasi-continuous high magnetic field is a special kind of pulsed magnetic field with a flat-top field longer than 100 ms. This paper proposes a hybrid power supply that consists of a capacitor power supply and a generator-rectifier power supply. A dual-coil magnet is powered to generate a 65 T/100 ms quasicontinuous high magnetic field with a ripple less than 500 ppm at the Wuhan National High Magnetic Field Center, Wuhan, China. A protection circuit consists of an R-C branch and a diode array is discussed for the worst short-circuit fault, which occurs between the first turns of inner coil and outer coil. This type of faultwill produce oscillation voltage with a high peak value and high frequency on the rectifiers. A self-adaptive PI controller with the coefficients corrected by a back propagation neural network is adopted to reduce the ripple of a flat-top. [ABSTRACT FROM AUTHOR]

The power supply based on pulse step modulation technology has been widely used as the high-voltage power supply (HVPS) for additional heating systems. The topology contains numbers of converters and multisecondary transformers. For the magnetizing inrush of the transformer and charging current of the converters connecting with the secondary windings of transformer, the power up of the power supply system is quite complex. There are resistor branches series with the transformer and each converter is used to limit the inrush current. A lot of resister branches and parallel contactors in the converter modules are required, and as a result the dissipation and electromagnetic interference inside the module are serious. In this paper, the soft-start circuit is simplified to only one resistor branch. The precharge circuits of the converters, which are connected to the secondary, are diverted from the inside of the modules to the primary winding of transformer. Since the multisecondary transformer powers up at the same time as converters, the capacitors in all converters will limit the ramp up rate of the transformer voltage, and the magnetic inrush current can be ignored. To analyze the characters of the precharge branches, all converters can be equaled as parallel during the soft-start process. The equivalent circuit, a series $RLC$ circuit, is proposed in this paper. A 1.2-kV power supply, contains 12 converters, with soft start has been built up in laboratory. Simulation and experiment results are shown to verify the theoretical analysis. A new soft-start circuit of 100-kV HVPS system was designed. [ABSTRACT FROM PUBLISHER]

The intrinsic properties of vertical InAs nanowire (NW) capacitors are investigated. The band structure is simulated using a Schrödinger–Poisson solver, taking the conduction band nonparabolicity into account. This is combined with a distributed RC model to simulate the current–voltage characteristics. It is found that the influence from the nonparabolicity is substantial for devices with a small nanowire diameter, resulting in an increased carrier concentration, a shift in the threshold voltage, and a higher intrinsic capacitance. These NW capacitors may be a suitable alternative in high frequency applications approaching 100 GHz, while maintaining a quality factor above 100. [ABSTRACT FROM PUBLISHER]

This paper proposes a method to boost the terminal voltages using a capacitive network. The boosted voltage can improve the power capability of an interior permanent magnet synchronous motor (IPMSM). In the conventional drive system fed by a voltage-source inverter, the terminal voltages of the motor are limited by the dc-link voltage. Such a voltage limitation reduces the torque capability at high speeds. Thereby, the maximum output power is limited. To overcome this feature, series capacitor network between the inverter and the motor is introduced in the proposed IPMSM drive system. The series capacitors boost the motor terminal voltages higher than the inverter voltages to increase the rated speed, resulting in improved power capability. The rated speed in the proposed drive system can be redefined to the desired value through a capacitive network. The enhanced power capability and design freedom in the rated speed are particularly advantageous in fan-load applications where the load torque is proportional to the square of speed. This article presents the structure, d–q equivalent model, operating characteristics, and operable area of the proposed drive. Experimental results are given to verify the feasibility and effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

The temperature of electrolytic capacitor in light-emitting diode (LED) drivers continuously increases under operation conditions, thus the capacitors degrade faster than that with constant temperature assumption. In this paper, a physics-of-failure (PoF)-based reliability prediction methodology is developed for LED drivers to consider the temperature change of electrolytic capacitor. SPICE simulation, compact thermal modeling, and Monte Carlo simulation are integrated to predict the failure rate distribution of an electrolytic capacitor of given LED driver systems. The simulation results agree well with the accelerated test results for an RC linear AC–DC converter. Furthermore, a single inductor buck–boost DC–DC converter is simulated to understand the degradation behavior of electrolytic capacitor. It has been found that the temperature of an output stage capacitor increases significantly during operation time. The capacitor's performance without taking temperature change into account results in an overestimated driver lifetime by more than 38% for the selected case study. [ABSTRACT FROM AUTHOR]

We investigate p-type GaSb MOS capacitors with various HfO2 thicknesses grown using an atomic layer deposition. GaSb surfaces treated with ex-situ chemical solution and in situ remote hydrogen plasma are inspected. After a series of etching steps, the GaSb surfaces exhibit smooth topography, indicating that this combination of treatments is capable of realizing ultrathin dielectric deposition. After etching processes, the ultrathin (approximately 3 nm) HfO2 layer deposited successfully on GaSb exhibit high-permittivity (approximately 21) properties as well as equivalent oxide thickness (EOT) of 0.75 nm, which can be attributed to the flat surface. To the best of our knowledge, the EOT of GaSb capacitor prepared using the exploited approach is record low. Furthermore, we find that the interlayer present after hydrogen plasma treatment and forming gas annealing could efficiently passivate interface state density and achieve high $C$ – $V$ modulation. Compared with the benchmark of gate leakage current versus EOT, the electrical performance with low gate leakage current of the GaSb MOS capacitors demonstrates the high feasibility of the proposed treatments. [ABSTRACT FROM AUTHOR]

This paper presents a novel method for detecting defective ac-coupling capacitors in high-speed differential signaling connections by designing a circuit with null detectors at the differential receiver. The design parameters of selecting the null ranges in the receiver buffer are proposed to efficiently detect the voltage droop that creates erroneous jitter. The null detectors in the proposed method enable the use of a lower test signal speed than the mission data rate at differential connections to detect defective capacitors. The proposed design method of null detectors combines four design and test factors, namely, regular null, voltage doubling, fail-safe, and defect sensitization, to determine the stretched null used for test purposes. The null-detection scheme has been implemented and verified in the design using a regular current-mode logic (CML) differential buffer in the 0.18-μm complementary metal-oxide-semiconductor (CMOS) process. The detection capability of the proposed method to check for traditional defects with the same null detector is also demonstrated through SPICE-based fault simulations. The proposed method is also verified with the board developed for parameter measurements. The parameters proposed in this paper showed excellent agreement among calculated, simulated, and measured values. In particular, measured parameters showed strong closeness up to 99% to its calculated values. [ABSTRACT FROM AUTHOR]

Capacitive dc-links are widely used in voltage source converters for power balance, voltage ripple limitation, and short-term energy storage. A typical solution, which uses aluminum electrolytic capacitors for such applications, is assumed to be one of the weakest links in power electronic systems, therefore, also becoming one of the lifetime bottlenecks of power electronic systems. Various passive and active capacitive dc-link solutions have been proposed intending to improve the reliability of the dc-links qualitatively, making great effort to diverting the instantaneous pulsating power into extra reliable storage components. In this paper, a generic topology derivation method for single-phase power converters with active capacitive dc-link integrated has been proposed, which can derive all existing topologies, and identify a few new topologies. According to the synthesis results, the main achievements in research on capacitive dc-link solutions are reviewed and presented chronologically as well as thematically ordered. Furthermore, the reliability-oriented design procedure is applied to size the chip area of active switching devices and the passive components to fulfill a specific lifetime target and system specification, as well as compare the overall capacitive energy storage, energy buffer ratio, and the cost of different solutions. The cost comparisons are performed with a scalable lifetime target and power rating. It reveals that different conclusions can be drawn with different lifetime targets in terms of cost-effectiveness. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to describe several different methods of protection of tuned capacitor banks and how the relay protection settings for each are determined. Problems with the different schemes are described, and a new protective scheme is proposed. [ABSTRACT FROM AUTHOR]

The decoupling of modern printed circuit boards introduces a very complex task. Powerful stochastic optimizers are usually used to determine values and positions of decoupling capacitors on the board. The number of capacitors used has to be determined a priori by the user which brings problems with convergence of the optimization process or can lead to a waste of resources when the noises are to be attenuated to a certain level. In this paper, an approach based on the combination of time-domain contour integral method and optimization with variable number of dimensions is introduced. The optimizer works with models having variable dimensions and searches for the optimal one. The approach is tested on two example power circuit boards with various noise attenuation limits and constraints on capacitor positions and values. [ABSTRACT FROM AUTHOR]

This paper presents an energy-efficient buck-type capacitor charger integrated circuit (IC) that can deliver high instantaneous power from a low-capacity battery using a capacitor as an energy buffer. The prototype IC, which was designed and fabricated in 250-nm CMOS, reduces capacitor charging losses by driving the buck converter with gradually increasing pulsewidths and then recycles the remaining energy by operating the buck converter in the reverse direction. The presented digital pulsewidth modulator (DPWM) supports a wide range of duty cycles from 4% to 96% with a fine resolution of 0.36% and a high switching frequency of 1.5 MHz. The optimal switching frequency and transition time that can minimize the charging/discharging losses are analyzed. The prototype charger IC can charge a 10\text-\upmuF capacitor to 4.2 V with a transition time of 1.25 ms with a peak charging efficiency of 93% while operating at a 1.5-MHz switching frequency. [ABSTRACT FROM PUBLISHER]

This paper presents a set of temperature-controlled standard capacitors that are developed via novel nanoceramic materials and new processes. The set of capacitors can ensure the high accuracy and accomplish high stability (maintained to 10^-6 ) and low dissipation, with capacitance range of 1 pF– 1~\mu \textF and an accuracy of 5–50 ppm (1 kHz). On the basis of this research, a standard capacitance box with high accuracy and a low zero-position capacitance has been developed with a capacitance range of 1 pF–0.1 \mu \textF and an accuracy of 50 ppm (1 kHz). [ABSTRACT FROM PUBLISHER]

The voltage coefficient of compressed gas capacitors is a relevant parameter in high-voltage calibrations. These capacitors, used as standards, are calibrated at low voltages so that it is necessary to know their variation when they are used at high voltages. Although several methods have been proposed to determine that coefficient, their implementation is very difficult. In this paper, a simplified method that does not need any special equipment is proposed, so that it is easy to carry out for most high-voltage laboratories. It only requires geometric data on the radius of the electrodes and the mass of the internal ones but it is not necessary to know them with high accuracy. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. Reliability is one of the most important challenges for the MMC consisting of a large number of submodules (SMs). The capacitor monitoring is one of the important issues in the MMC. This paper proposed a reference submodule (RSM)-based capacitor monitoring strategy for the capacitance estimation in the MMC, where the capacitances in the monitoring SMs can be estimated based on the capacitor voltage relationship between the RSM and the monitoring SMs. The proposed monitoring strategy does not rely on the information of all capacitor voltage and current, which effectively simplifies the algorithm for capacitance estimation. The simulation studies with the time-domain professional tool PSCAD/EMTDC are conducted and a down-scale MMC prototype is also tested in the laboratory with the proposed capacitor monitoring strategy. The study results confirm the effectiveness of the proposed capacitor monitoring strategy. [ABSTRACT FROM AUTHOR]

This paper presents nonisolated single-switch high step-up converters with low voltage stress. Based on the conventional flyback converter, one single-switch high step-up converter is derived. The voltage stresses on the switch and diodes are limited by using a clamping diode and voltage doubler structure. Also, to further reduce the voltage stresses of them, another single-switch high step-up converter is proposed simply by using one additional capacitor and rearranging the components. Thus, lower voltage-rated switch and diodes can be used, which results in higher efficiency. The operational principle, analysis and design considerations of each converter are presented in this paper. The validity of this study is confirmed by the experimental results from 24 V input and 250 V/125 W output prototype. [ABSTRACT FROM AUTHOR]

This paper presents the derivation and experimental verification of the closed-form subharmonic instability condition of the constant-frequency peak-current-controlled buck converter with closed voltage feedback loop. The well-known open-voltage-loop instability condition becomes a special case. The instability limits in the converter parameter space are readily obtained from the result. It is found that closing the voltage feedback loop tends to degrade the stability margin. One can clearly see the effects of all converter parameters (such as the pole, zero, and gain of the voltage-loop compensator, the equivalent series resistance of the output capacitor, the presence of a second output capacitor, and the switch turn-off delay) on the instability. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG) technology has emerged as a new mechanical energy harvesting technology with numerous advantages. This paper analyzes its charging behavior together with a load capacitor. Through numerical and analytical modeling, the charging performance of a TENG with a bridge rectifier under periodic external mechanical motion is completely analogous to that of a dc voltage source in series with an internal resistance. An optimum load capacitance that matches the TENGs impedance is observed for the maximum stored energy. This optimum load capacitance is theoretically detected to be linearly proportional to the charging cycle numbers and the inherent TENG capacitance. Experiments were also performed to further validate our theoretical anticipation and show the potential application of this paper in guiding real experimental designs. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, packaging, and experimental characterization of the first temperature-sensitive MEMS capacitors for health monitoring applications up to 275 ^\circ\C. The capacitive sensor chip is 2 \times 2\ \mm^2 fabricated on a 500-\mu\m-thick Si wafer and comprises an array of 220 individual 10 \times 250 \ \mu\m^2 inherently robust bimorphs. This first part focuses on the fabrication and packaging, thermomechanical design, electromagnetic modeling, and technology of the unpackaged and packaged bimorph beams. On the thermomechanical part, the measured profiles match theoretically predicted profiles from 20 ^\circ\C to 250 ^ \circ\C within 4% and 3% at the beam midpoints and tips, respectively. Similarly, experimentally obtained capacitance changes for five separate packaged devices show a mean error of less than 3% and a maximum error of less than 5% from the theoretical model up to 165 ^\circ \C. The packaged sensors simultaneously achieve for the first time: 1) high temperature operation; 2) monotonic capacitance–temperature response from 20 ^\circ \C to 300 ^\circ\C; 3) hermetic sealing; 4) miniature size of 5.4 \times 5.4 \times 3.6\ \mm^3; and 5) capacitance quality factor of over 5000 at 20 ^\circ \C and 1000 at 160 ^\circ\C. Experimental results underline the tradeoffs between beam arrangement, attachment method to the package, and package to the quality factor of the device.\hfill[2011-0316] [ABSTRACT FROM AUTHOR]

This paper exhibits the generation of an operational transconductance amplifier and capacitor (OTA-C) arbitraryphase-shift sinusoidal oscillator (APSO) for an order n ≥ 3 for various advanced applications. A new nth-order quadrature oscillator (QO) is obtained via the algebraic quadrature manipulations of an oscillatory characteristic equation. Based on a phase shift transformation from a quadrature, an APSO is then generated by superposing OTAs with required +/- transconductance(s) in parallel with some grounded capacitor(s) on the QO. For eliminating nonideal and parasitic effects to improve phase accuracy, phase compensation schemes are proposed. A new native amplitude control exploiting the nonlinearity of all employed OTAs of the APSO is presented as well to lead to rather low THD and a lower variation of THD with respect to amplitude enlargement. A fourth-order APSO is demonstrated and simulated using Hspice with a 0.35-μm process for validation. In addition, its real application to a polyphase rectifier is improved. Finally, an experiment using LM13700s shows favorable potential of APSOs. [ABSTRACT FROM AUTHOR]

This paper describes the procedure to qualify an admittance meter as a permittivity meter and a conductivity meter σsensor through validation with liquids over a range of relative permittivity εr values from 1 to 80 and with operating frequencies f between 1 and 20 MHz. The sensor is a capacitor which consists of two parallel cylinders of 10-cm typical dimension. A circuit-based model of the sensor was previously calibrated against accurate electronic components. A discrepancy of 10% is found between the calibration with components and the validation with liquids. All potential errors have been carefully examined: parasitic impedances of the electronic circuit and leads, modifications of liquid permittivity εrliq due to temperature influence, water contamination or relaxation effects, and possible fringing effects with the help of numeric simulations. Forty percent of the discrepancy results from the finite dimensions of the liquid-filled recipient. The fringing effects due to insulating rings at each end of the capacitor seem to be discarded. The analysis of the uncertainty on εrsensor and σsensor shows a relative uncertainty of 3%-5% due in large part to the numerical acquisition of high frequency. [ABSTRACT FROM PUBLISHER]

Over the last years, more and more SiC power semiconductor switches have become available in order to prove their superior behavior. A very promising device is the 1200 V 30 A JFET manufactured by SemiSouth. It features a very low on-resistance per die area (2.8 mΩ-cm2), switching within 20 ns, normally off characteristic, high-temperature operation and has already been commercialized in contrast to many other SiC switches. To fully exploit the potential of the SiC normally off JFET, conventional gate drivers for unipolar devices must be adapted to this device due to its special requirements. During on-state, the gate voltage must not exceed 3 V, while a current of around 300 mA (depending on the desired on-resistance) must be fed into the gate; during switching operation, the transient gate-source voltage should be around ±15 V and the low threshold voltage of less than 0.7 V requires a high noise immunity which is a severe challenge as the device has a comparably low gate-source but high gate-drain capacitance. To meet these requirements, several concepts have been published recently. They deal with the challenges mentioned, but they still show certain limitations (e.g., frequency and duty cycle limitations or need for additional cooling due to high gate driver losses). In this paper, a novel gate driver consisting of only one standard gate driver IC, resistors, capacitors, and diodes is designed and experimentally validated. It supplies enough gate current for minimum on-resistance, allows fast switching operation, features a high noise immunity, and can be used for any duty cycle and typical switching frequencies without significant self-heating. [ABSTRACT FROM AUTHOR]

Most research work in current-source inverter (CSI) fed motor drives has focused on general control strategies, pulsewidth modulation schemes, topologies, and efficiency evaluation. This paper, however, is dedicated to investigating zero-speed operation characteristics of CSI-fed induction motor drives (IMDs). Zero-speed operation can greatly increase the competitive value of the drive and expand its range of applications to include cranes, hoists, and draglines. The motor drive is controlled with rotor flux orientation, where stator currents and motor speed are employed for the rotor flux estimation. Unlike voltage-source-inverter-based drives, filter capacitors are required at the output of the CSI for current commutation and harmonics filtering. The influence of these capacitors on the system dynamic performance is comprehensively evaluated. Moreover, a classic load torque observer with feedforward control is employed to improve the speed dynamic response. Simulated and experimental results show that the CSI-fed IMD works well at zero speed with promising speed dynamic performance. [ABSTRACT FROM AUTHOR]

Active power-factor correctors (PFCs) are needed to design ac-dc power supplies with universal input voltage range and sinusoidal input current. The classical method to control PFCs consists in two feedback loops and an analog multiplier. Hence, the input current is sinusoidal and it is in-phase with the input voltage. However, a bulk capacitor is needed to balance the input and the output power. Due to its high capacitance, an electrolytic capacitor is traditionally used as a bulk capacitor in PFCs. As a consequence, the lifetime of the ac-dc power supply is limited by the electrolytic capacitor's, which becomes insufficient to some applications (e.g., high-brightness LEDs). This paper proposes a reduction of the output voltage ripple (which allows reduction of the output capacitance) by distorting the input current, but maintaining the harmonic continent compatible with EN 61000-3-2 regulations. The limits of this output capacitor reductions are deduced. Also, a control strategy based on a low-cost microcontroller is developed to put the proposed study into practice. Finally, the theoretical results are validated in a 500-W prototype. [ABSTRACT FROM AUTHOR]

In this paper, a new zero-current switching pulse width modulation forward converter is introduced using a new switching algorithm for the auxiliary circuit. In the proposed converter, transformer core is reset through a resonance, and thus, reset winding is not required which is the main advantage of this converter over existing zero-current switching forward converters. The simple auxiliary circuit of this converter is just composed of an auxiliary switch and a capacitor that provides zero-current switching for the main switch and also resets the transformer core. Furthermore, the proposed auxiliary circuit uses the leakage inductance of the transformer for the resonant inductor and does not require any additional inductor which is another advantage of the proposed converter over conventional zero-current switching forward converters. Also, the auxiliary switch is soft switched. The proposed converter is analyzed and design procedure of the auxiliary circuit is discussed. The presented experimental results confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

Filter capacitors in an HVDC converter station produce audible noise, which can be as loud as that of converter transformers and, therefore, needs to be reduced. Compressible space component (CSC) absorbers can be used to reduce the audible noise due to their broadband frequency and outstanding performance. In this paper, a mechanical model of a CSC absorber is proposed as an audible noise reduction measure for the filter capacitor in the HVDC converter station and then three CSC absorbers with different gas volumes are designed and installed at the bottoms of capacitors, respectively. Audible noise experiments of the filter capacitors with different CSC absorbers are performed and the experimental results are compared with those of a regular filter capacitor. Results indicate that the CSC absorber is a broadband absorber and is effective to reduce audible noise of the filter capacitors. [ABSTRACT FROM AUTHOR]

This paper investigates voltage and reactive power control in distribution systems and how the presence of synchronous machine-based distributed generation (DG) affects the control. A proper coordination among the onload tap changer (OLTC), substation switched capacitors and feeder-switched capacitors in order to obtain optimum voltage and reactive power control is proposed. It is assumed that there is no communication link between the OLTC and the capacitors, a normal case in distribution system operation these days. The results indicate that the proposed method decreases the number of OLTC operations, losses, and voltage fluctuations in distribution systems, with and without DG present. The power-flow reversal due to the lJG is shown not to interfere with the effectiveness of the OLTC operation. Further, it is also shown that as long as the available capacitors are enough to compensate the reactive power demand, the DG operation mode does not give a significant effect to the distribution system losses. However, DG operating at a constant voltage is beneficial for a significant reduction of OLTC operation and voltage fluctuation in the distribution system. [ABSTRACT FROM AUTHOR]

This paper first investigates a local voltage and reactive power control (local control) in a distribution system based on local control of on-load tap-changer (OLTC), substation capacitors, and feeder capacitors, and how the presence of induction machine based distributed generation (DG) affects it. A proper coordination among those available voltage and reactive power control equipment to minimize losses in the distribution system, with and without DG, is formulated. Secondly, a combined local and remote voltage and reactive power control (local-remote control), which is based on automated remote adjustment to the local control in order to minimize the losses even more, is proposed. The automated remote adjustment in the local-remote control is also intended to keep the operating constraints fulfilled all the time, which cannot be achieved by using the local control when DG is present in the system. The OLTC and substation capacitors are assumed to be remotely controllable, while the feeder capacitors are not. DG with both constant power and varying power are investigated. [ABSTRACT FROM AUTHOR]

This paper proposes a bandwidth-compensation method for miniaturized filters based on short-ended parallel coupled lines. Capacitive loading of such coupled lines is a relatively simple means of reducing the line lengths. In this study, a method is developed that predicts exactly the degree of reduction in the fractional bandwidth due to miniaturization. Using this method, the fractional bandwidth of the prototype coupled line filter can be adjusted, enabling miniaturized filters to maintain the targeted fractional bandwidth. The proposed bandwidth-compensation method applies for any type of filters with coupled lines realized with various transmission lines, with uniform or nonuniform line lengths. Experimental results are also presented that verify the validity of the method. [ABSTRACT FROM AUTHOR]

Advances in high-power-density batteries have rekindled interest in using inductive store as a pulse compression system. Although these batteries are considered very power dense, they lack over an order of magnitude of power density to drive a deployable electric gun. However, one can add an inductive circuit to a battery bank to make a hybrid system that has a much higher power density than batteries alone. A battery-inductor hybrid pulsed-power supply boasts several advantages over pulsed alternators, as inductors are static and relatively easy to cool. Inductors are potentially more energy dense than capacitors, making a battery-inductor hybrid pulsed-power supply an attractive alternative to capacitor-based pulsed-power supplies. The opening switch has been a major obstacle in previous inductive store projects, but in simulation, a new circuit topology—the Slow Transfer of Energy Through Capacitive Hybrid (STRETCH) meat grinder—greatly attenuates the problem. This paper discusses the design, construction, and testing of a small-scale STRETCH meat grinder system, which was successfully used to power a miniature railgun. [ABSTRACT FROM AUTHOR]

This paper describes the design, fabrication and testing of a quasi-static electromagnetic cavity resonator fabricated using potassium-hydroxide (KOH) etching, shallow reactive-ion etchiing (RIE), metalization and wafer bonding. The resonator is distinguished by its simultaneous high-Q near 200, and wide high-frequency tuning range, 2.5–4.0 GHz for the experimental resonator presented here. When combined with an integrated actuator, it should be suitable for use in electronically tunable radio-frequency (RF) bandpass filters and oscillators. The experimental resonator, however, is tuned with an external piezoelectric actuator for simplicity. [ABSTRACT FROM AUTHOR]

Electrical filters are important for attenuating electrical ripple, eliminating electromagnetic interference (EMI) and susceptibility, improving power quality, and minimizing electromagnetic signature. Capacitors are critical elements in such filters, and filter performance is strongly influenced by the capacitor parasitics. This paper introduces a new design technique that overcomes the capacitor parasitic inductance that limits filter performance at high frequencies. Coupled magnetic windings are employed to effectively cancel the parasitic inductance of capacitors, and to add inductance in filter branches where it is desired. The underlying basis of the new technique is treated in detail, and its application to the design of both discrete filters and integrated LC filter components is described. Numerous experimental results demonstrating the high performance of the approach in both discrete filters and integrated filter elements are provided. [ABSTRACT FROM AUTHOR]

Lifetime is an important performance factor in the reliable operation of power converters. However, the state-of-the-art LC filter design of a buck dc–dc converter is limited to the specifications of voltage and current ripples and constrains in power density and cost without reliability considerations. This paper proposes a method to optimize the design of the LC filters from a reliability perspective, besides other considerations. An enhanced model is derived to quantify the lifetime of the capacitor in the filter considering the electrothermal stress on it. Furthermore, the influence of different design aspects such as the value of capacitance, the value of inductance, and the type of the capacitor have been discussed, focusing on their impacts on the key design objectives, which are the cutoff frequency, lifetime, and volume. Based on the analysis, an optimized design is proposed among different parameter sets. A 1-kW converter prototype is applied to verify the theoretical analysis and simulation. [ABSTRACT FROM AUTHOR]

Reliability improvement of the Photovoltaic (PV) inverter has a high potential for reducing the cost of PV energy. The DC-link capacitor is one of the main components influencing the reliability of PV inverter systems. Various pulse-width modulation (PWM) methods have been proposed to increase the lifetime of the DC-link capacitor by reducing its ripple current. However, state-of-the-art PWM methods for reducing capacitor ripple current increase the output current THD. Nevertheless, its optimal application to achieve the target lifetime without unnecessary deterioration in output current THD has not been discussed. This paper proposes a PWM method for improving the lifetime of the DC-link capacitor of the NPC inverter. In addition, a mission-profile-based optimal application of the proposed PWM method with conventional Space Vector Modulation (SVM) called a hybrid MLZSVM method is presented for achieving the target lifetime of the DC-link capacitor with minimized negative effect on the output THD of the NPC inverter. The proposed hybrid PWM concept is verified by the case study based on an annual mission profile of the PV system. Finally, the feasibility and effectiveness of the proposed method are verified through experiments.

We propose a pair of techniques to lower the energy consumed by driving 1-pixel liquid-crystal displays (LCDs). The first one employs multiple capacitors while the other divides the LCD into two to lower the drive voltage. Simulations show that large capacitance values and many capacitors reduce the energy consumed, and stacking two thin low voltage LCDs maximizes the effect by decreasing the overhead consumed by the microcontroller. Actual polymer-dispersed LCDs (PDLCDs) are tested to confirm that the techniques work as effectively as the simulations imply. The results show that the overall energy consumption of large PDLCDs is reduced more than 70% using multiple capacitors, and the combination of the two techniques successfully reduces the driving energy even for small LCDs. While the polarity reversal of the proposed technique does incur some delay, it was confirmed by a flicker test that the technique does not degrade image quality. [ABSTRACT FROM AUTHOR]

This paper presents a novel integrated magnetic boost converter (IMBC) with both input/output current ripple cancellation and right-half-plane (RHP) zero elimination. The input inductor, output inductor, and the ripple cancellation network auxiliary inductor of the proposed IMBC have been integrated in one magnetic core. Two extra capacitors were added to achieve input and output current ripple cancellation. Therefore, the input current ripple of the IMBC dropped to one-twelfth of the original in a conventional boost converter, and the output current worked in continuous-conduction-mode with very small ripple. Meanwhile, the proposed IMBC has eliminated the RHP zero of the boost converter, which means higher bandwidth can be reached. The using of the integrated magnetic technique not only performs above advantages but also shows great potential for reducing the weight and volume of dc-dc converter. Finally, three 36 V input, 50 V output and 500 W prototypes operating at 100 kHz are implemented to verify the expected performance. The experimental results show that the proposed IMBC can achieve both input and output current ripple cancellation and RHP zero elimination with the maximum efficiency of 96.8%. All these advantages of the IMBC are very important especially in high dynamic response, high efficiency, and high-power application. [ABSTRACT FROM AUTHOR]

This paper addresses on-chip solar energy harvesting and proposes a circuit that can be employed to generate high voltages from integrated photodiodes. The proposed circuit uses a switched-inductor approach to avoid stacking photodiodes to generate high voltages. The effect of parasitic photodiodes present in integrated circuits (ICs) is addressed and a solution to minimize their impact is presented. The proposed circuit employs two switch transistors and two off-chip components: an inductor and a capacitor. A theoretical analysis of a switched-inductor dc-dc converter is carried out and a mathematical model of the energy harvester is developed. Measurements taken from a fabricated IC are presented and shown to be in good agreement with hardware measurements. Measurement results show that voltages of up to 2.81 V (depending on illumination and loading conditions) can be generated from a single integrated photodiode. The energy harvester circuit achieves a maximum conversion efficiency of 59%. [ABSTRACT FROM AUTHOR]

With the aim to increase the competitiveness of solar energy, the high reliability of photovoltaic (PV) inverters is demanded. In PV applications, the inverter reliability and lifetime are strongly affected by the operating condition that is referred to as the mission profile (i.e., solar irradiance and ambient temperature). Since the mission profile of PV systems is location-dependent, the inverter reliability performance and lifetime can vary considerably in practice, that is, from the reliability perspective, PV inverters with the same design metrics (e.g., component selection) may become over or underdesigned under different mission profiles. This will increase the overall system cost, e.g., initial cost for overdesigned cases and maintenance cost for underdesigned cases, which should be avoided. This article, thus, explores the possibility to adapt the control strategies of PV inverters to the corresponding mission profiles. With this, similar reliability targets (e.g., component lifetime) can be achieved even under different mission profiles. Case studies have been carried out on PV systems installed in Denmark and Arizona, where the lifetime and the energy yield are evaluated. The results reveal that the inverter reliability can be improved by selecting a proper control strategy according to the mission profile. [ABSTRACT FROM AUTHOR]

Failure analysis revealed that capacitor short-circuit failures were related to a MIM metal missing/peeling defect. During subsequent investigation a correlation between MIM top metal defects and Knudsen flow conditions within the metal deposition system was revealed. MIM surface condition prior to and after top metal deposition was extensively studied. MIM surface characterization showed large size particles formed on the MIM feature after the wafer experienced Knudsen flow. Experiments show such defects could also be produced after multiple oxygen plasma cleans and long staging time of exposed MIM features. These same changes of the MIM surface condition occurred at an accelerated rate under Knudsen flow conditions in the metal deposition system. Inline AOI results showed that when the Knudsen number was at or greater than ~0.2 during vacuum load lock pumping, MIM metal missing/peeling defects were formed, affecting up to 20% of die. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency high power density LLC resonant converter with a matrix transformer is proposed. A matrix transformer can help reduce leakage inductance and the ac resistance of windings so that the flux cancellation method can then be utilized to reduce core size and loss. Synchronous rectifier (SR) devices and output capacitors are integrated into the secondary windings to eliminate termination-related winding losses, via loss and reduce leakage inductance. A 1 MHz 390 V/12 V 1 kW LLC resonant converter prototype is built to verify the proposed structure. The efficiency can reach as high as 95.4%, and the power density of the power stage is around 830 W/in3. [ABSTRACT FROM AUTHOR]