Capacitor Units Research Articles

Demonstration Experiment for Energy Storage and Rapid Charge System for the Solar Light Rail

An application of renewable energy is expected. However, renewable energy such as solar and wind is unstable. Therefore, thermal power plants are necessary to operate solar power plants and wind turbines on commercial power supply. In this paper, a rechargeable system for renewable energy application is proposed and a demonstration experiment using rideable model railroad is reported. The electric double layer capacitor (EDLC) unit of 17.5V - 171.4 F is charged by solar panels, and another EDLC unit of 15.0V - 100 F mounted on the railcar is charged rapidly from EDLC unit connected to solar panels. A railcar run by charged energy on 9 meters of strait rail. Although the experiment was carried out in January–only two weeks after of the winter solstice, rapid charge was carried out 56 times and railcar ran for 9hours a day. It was confirmed that this method–using EDLC as energy storage device and rapid charge from EDLC to EDLC–is effective through a day.

Comparative Study of Arc-Quenching Capabilities of Different Ablation Materials

Gases released from polymers placed near a burning electric arc are known to influence the behavior of the arc. In switching equipment, such ablation materials can be used to improve the interrupting capability. Current interruption experiments have been carried out with the purpose of comparing the arc-quenching capabilities of four common polymers. The test setup has static electrodes and two ablation polymer plates placed in parallel on both sides of the arc. Each ablation material is tested according to an “up-and-down” procedure that determines the current magnitude giving 50% probability for successful interruption. Current is supplied from a capacitor unit, and a sinusoidal waveform is created by means of a damped RLC circuit. The electrodes and the ablation materials are replaced after each interruption test. Polypropylene shows the best arc-quenching performance among the tested materials and interrupts about 2.7 times as high current as polyetetrafluoroethylene (PTFE), which is used as a reference material due to its low gassing. Polycarbonate and poly(methyl methacrylate) also greatly improve the current interrupting properties, interrupting a 2.2-2.3 times higher current compared to PTFE. As also pointed out by others, the arc-quenching capabilities of the polymers seem to increase with an increasing content of hydrogen in the ablation polymer.

Analysis on Unbalance Protection of SCB

Shunt capacitor is a main measure to reactive power compensation of power system, which has the advantages of flexibility and economy. In order to guarantee the safety of shunt capacitor, the methods for protecting against over-voltage, under-voltage, over-current and unbalance in circuits according to the different operation modes are used. This paper in detail introduces unbalance protection ways under different connection modes of capacitor group. It is analyzed and calculated that the unbalanced current and voltage with the effects of fault capacitor units, components and fuses on capacitor bank as well through a case of unbalance computation of shunt capacitor banks (SCB) of ungrounded single star with external fuse. It is indicated by PSCAD simulation analysis that the result of theory calculation is the same as the simulation, which provides theory basis of setting the tripping point and alarm point of relay protection.

Integrated Capacitor Array Matching Characterization

A novel characterization methodology for integrated capacitor array mismatch determination is presented. The circuit allows multiplexed biasing of 20 capacitor units and the selection of a specific array on chip. Information about the spatial matching behavior is provided for an entire poly-Si capacitor array, where the relevant parameters are the standard deviations σ(ΔC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> /C) and the offsets μ(ΔC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> /C) of units i. The circuit design and the measurement strategy are discussed in detail. Furthermore, the measurement reproducibility is determined quantitatively and correlations introduced by the extraction method are investigated. The corresponding test chips were successfully realized in 0.35- and 0.18-μm standard CMOS technologies. Results for the poly-Si capacitor array (0.35-μm technology) are presented in this paper.

A Rack-and-Pinion Pumping Unit Design

This paper presents a rack-and-pinion pumping unit. A type of SRD (switched reluctance driver) motor is utilized as the driving unit of the pumping unit. The rotation direction of the output shaft of the motor can change automatically, without reversing mechanism，so it can directly dive the gear box and then drive the rack-and-pinion in which the rack connected with the suck rod. Additionally, a super capacitor unit and control unit of charge and discharge is used to design the balance of the pumping unit. Due to the special balance design and no crank-rocker mechanism in the rack-and-pinion pumping unit, it has features of simple structure, less floor area, well balanced and high running efficiency. The most important is that the stroke and number of punching can be adjusted in a wide range which can adapt to different oil wells.

Capacitive matching of pore size and ion size in the negative and positive electrodes for supercapacitors

The capacitive behavior of activated carbons with different pore structures in two kinds of electrolytes, Bu 4NBF 4 and Et 4NBF 4 in propylene carbonate (PC) was studied using three kinds of cell configuration. The correlations between adsorbed ion size and pore size on the positive and negative electrodes were investigated. The matching of pore size and cation size was more predominant in the capacitor unit, especially for the electrode materials with less developed porosity. The asymmetric capacitance distribution of 7 F g −1 in the negative electrode and 113 F g −1 in the positive electrode occurred for electrode materials with less developed porosity. This could be ascribed to the surface saturation of the negative electrode by electrolyte ions, limiting the overall capacitance and working voltage of device. However, very developed porosity could not profit from the sufficient unitization of surface area, due to a weakened interaction between ions and pores wall. The specific area capacitance experienced a significant decrease from 11.3 to 6.7 μF cm −2 with the pore volume increasing. Since the different pore sizes were required for different electrolytes ion on the negative and positive electrodes, the optimal matching between pores size and ions dimension with respect to each electrode should be considered for the maximum capacitance value of the capacitor unit.

Distribution Networks with Linear and Nonlinear Loads: Cost-Based Method for Planning Dispersed Generation and Capacitor Units under Uncertainty

This paper discusses the optimal allocation of capacitors and dispersed generation units in a medium-voltage distribution system with linear and nonlinear loads. An optimization problem is formulated and solved for optimal siting and sizing, with the objective of minimizing costs sustained by the distributor for reactive power service, even containing the impact of the waveform distortions. A three-step procedure, based on genetic algorithm and decision theory, is applied to obtain a solution for the optimization problem that takes into account the unavoidable uncertainties that the dispersed generation production and the loads introduce. The numeric applications performed on an 18-bus test distribution system demonstrate of the effectiveness of the proposed procedure.

Fabrication of micropatterned ferroelectric gamma poly(vinylidene fluoride) film for non-volatile polymer memory

We describe a facile and robust method for fabricating ferroelectric γ-type poly(vinylidene fluoride) (PVDF) thin films useful for non-volatile polymer memory. Our method is based on heating and cooling rate-independent melt-recrystallization of a thin PVDF film confined under a surface-energy-controlled top layer that strictly forbids paraelectric α crystals. Thin and uniform PVDF films with ferroelectric γ crystals consisting of characteristic twisted lamellae are formed with versatile top layers including metals, oxides, and even polymers. Micropatterns of ferroelectric γ PVDF domains isolated by paraelectric α domains are readily developed when pre-patterned top layers are employed. Our ferroelectric films are conveniently incorporated into arrays of either capacitor or transistor-type non-volatile memory units. Arrays of ferroelectric transistors with vacuum deposited pentacene channels are fabricated with micropatterned γ PVDF films. Furthermore, arrays of bottom-gate ferroelectric transistor memories are demonstrated, in which our ferroelectric PVDF film is directly micropatterned during crystallization under the patterned poly(3-hexyl thiophene) active channels.

A Novel High-Voltage Pulsed-Power Supply Based on Low-Voltage Switch–Capacitor Units

This paper presents a high-voltage pulsed-power system based on low-voltage switch-capacitor units that are connected to a current source for several applications such as plasma systems. A modified positive buck-boost converter topology is used to utilize the current source concept, and a series of low-voltage switch-capacitor units is connected to the current source in order to provide a high voltage with a high voltage stress (dv/dt) as demanded by the loads. This pulsed-power converter is flexible in terms of energy control because the stored energy in the current source can be adjusted by changing the current magnitude to significantly improve the efficiency of various systems with different requirements. The output-voltage magnitude and stress (dv/dt) can be controlled by a proper selection of components and control algorithm to turn on and off the switching devices.

Capacitor units with air insulation for linear transformers

The design of two capacitor units intended for use in high-power pulsed generators is described and the results of their tests are presented. Each unit is an assembly consisting of a multichannel spark gap and two capacitors with a total capacitance of 80 or 16 nF and a charging voltage of up to 100 kV. The use of air at atmospheric pressure as the insulating and working medium of the spark gap is a feature of the capacitor units. The following parameters of the output pulses were obtained at a resistive load for the 80- and 16-nF units: currents of ∼48 and ∼20 kA, voltages of ∼55 and ∼52 kV, and times of energy deposition into the load of ∼140 and ∼60 ns, respectively. A model for numerical calculation of the transient discharge process in the capacitor units is presented and the influence of the capacitance of the capacitors and the number of spark channels in the spark gap on the parameters of the generated pulse is analyzed.

Printable Ferroelectric PVDF/PMMA Blend Films with Ultralow Roughness for Low Voltage Non‐Volatile Polymer Memory

AbstractHere, a facile route to fabricate thin ferroelectric poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) blend films with very low surface roughness based on spin‐coating and subsequent melt‐quenching is described. Amorphous PMMA in a blend film effectively retards the rapid crystallization of PVDF upon quenching, giving rise to a thin and flat ferroelectric film with nanometer scale β‐type PVDF crystals. The still, flat interfaces of the blend film with metal electrode and/or an organic semi‐conducting channel layer enable fabrication of a highly reliable ferroelectric capacitor and transistor memory unit operating at voltages as low as 15 V. For instance, with a TIPS‐pentacene single crystal as an active semi‐conducting layer, a flexible ferroelectric field effect transistor shows a clockwise I–V hysteresis with a drain current bistability of 103 and data retention time of more than 15 h at ±15 V gate voltage. Furthermore, the robust interfacial homogeneity of the ferroelectric film is highly beneficial for transfer printing in which arrays of metal/ferroelectric/metal micro‐capacitors are developed over a large area with well defined edge sharpness.

Power Points

This article discusses various aspects of nanoscale materials that are seen to revolutionize energy storage. Teams of researchers working around the globe are finding that as the materials in batteries and capacitors become more finely engineered, they increase their energy storage capabilities. Within a decade, nanomaterial-based batteries and capacitors could find themselves not just in power tools and cell phones, but in uninterruptible power supplies, electric vehicles, and even the electric grid, to help handle wind and solar energy. The new lithium-ion battery relies on nanoparticles in its electrolyte to provide greater energy density and longer cycle life than conventional batteries. As batteries are playing such a prominent role, researchers are working hard to improve them, eliminating such headaches as recharge memory and packing more energy into each cubic inch. Studies show that distributed electricity generation from solar panels or combined heat and power systems could be backed up with a refrigerator-size capacitor unit that could store excess energy. The promise of nanotechnology-enhanced energy storage is enough to make anyone see a limitless future. A123’s Fulop cautions that nano-based storage systems ought to be looked at with optimism tempered by caution.

Unbalance Protection of Fuseless, Split-Wye, Grounded, Shunt Capacitor Banks

In recent years, a large number of electric utilities have been implementing fuseless split-wye grounded capacitor banks in lieu of the traditional externally fused bank. This change in philosophy has forced many protection engineers to research new methods of calculating the quantities needed to apply unbalance protection. This paper presents a novel method of calculating the unbalance current produced by fuseless capacitor unit failures as well as some general background information regarding fuseless split-wye grounded capacitor bank technology and unbalanced protection.

Micromachined accelerometer with area-changed capacitance

A new accelerometer based on the principle of area-changed capacitance is presented. The movable mass is designed as many bars connected together and suspended by elastic beams. Two comb-shaped fixed electrodes with their fingers side by side are alternately placed under the mass. The mass moves in the direction parallel with the substrate plane under the effect of acceleration. The bars and fixed electrodes fingers compose a differential capacitor unit. A quasi-LIGA technology is used to fabricate the sensor chip. And a linear differential capacitance related with the acceleration is obtained.

Surface field dynamics in dc film capacitors under an impulse voltage perturbation

For metalized polymer film capacitors, the dynamics of electric field on the electrode surface and its resulting energy dissipation influence the onset and scale of breakdown discharges within the capacitor unit, which in turn is indicative of the reliability and lifetime. To gain an understanding of the dependence of surface electric field on key system parameters, an equivalent circuit model is developed to simulate the temporal evolution of the, electric field distribution within a dc film capacitor subjected to an external impulse electric stress. A mosaic pattern of electrode segmentation is taken into account by means of an effective surface resistance and its effects on surface electric field and energy dissipation are computed numerically. Also considered are the effects of the number of electrode segments across a given length. In addition, electric energy dissipation is calculated to assess the level of possible temperature rise within the capacitor. By addressing these two issues, it is shown that the numerical code developed and its underlying methodology can serve as a complimentary tool to the present practice of capacitor designs and performance assessment.

Failure Analysis of Composite Dielectric of Power Capacitors Used in Distribution Systems

This paper describes the study of the reliability of capacitor units installed and operated in distribution system during the period 1980 through 1990. Failures of capacitor units in distribution substations can be very costly to the supply of reliable power to consumers. To enhance utility reliability, failure analysis, and rates, failure origin and physical damage causes were performed for these capacitor units. Two approaches, statistical and physical, were utilized in this study. In the statistical area, failure modes, reliability levels and failure causes are analyzed. The physical study mainly deals with the mechanism of deterioration of the composite dielectric. This paper models capacitor's failure mathematical mode and calculates their failure rate. The results of the study of 2912 capacitor banks including 8736 capacitors installed at 153 distribution substations showed that the failure mode of capacitor units may be represented by Weibull distribution and each capacitor manufacturer has a different failure rate. Analysis showed that partial discharge properties are a critical indicator for capacitor failure mechanism. Useful conclusions are presented both for power system operators and manufacturers. The methodology used in this study also applies to other equipment in the distribution system such as oil switches, transformers, and insulators.

Failure analysis of composite dielectric of power capacitors used in distribution systems

This paper describes the study of the reliability of capacitor units installed and operated in distribution systems during the period from 1980 through to 1990. Failures of capacitor units in distribution substations can be very costly to the supply of reliable power to consumers. To enhance utility reliability, failure analysis and rates, failure origin and physical damage causes were performed for these capacitor units. Two approaches, statistical and physical, were utilized in this study. In the statistical area, failure modes, reliability levels and failure causes are analyzed. The physical study mainly deals with the mechanism of deterioration of the composite dielectric. This paper models capacitor's failure mathematical mode and calculates their failure rate. The results of the study on 2912 capacitor banks including 8736 capacitors installed at 153 distribution substations showed that the failure mode of capacitor units may be represented by Weibull distribution and each capacitor manufacturer has different failure rate. Analysis showed that partial discharge properties are a critical indicator for capacitor failure mechanism. Useful conclusions are presented both for power system operators and manufacturers. The methodology used in this study also applies to other equipment in the distribution system such as oil switches, transformers and insulators.

Failure analysis of composite dielectric of power capacitors in distribution systems

This paper describes the study of the reliability of capacitor units installed and operated in a distribution system during the period 1980 through 1990. Failures of capacitor units in distribution substations can be very costly to the supply of reliable power to consumers. To enhance utility reliability, failure analysis and rates, failure origin and physical damage causes were performed for these capacitor units. Two approaches, statistical and physical, were utilized in this study. In the statistical area, failure modes, reliability levels and failure causes are analyzed. The physical study mainly deals with the mechanism of deterioration of the composite dielectric, The results of the study on 2912 capacitor banks including 8736 capacitors installed at 153 distribution substations showed that the failure mode of capacitor units may be represented by a Weibull distribution and each capacitor manufactures has different failure rate. Analysis showed that partial discharge properties are a critical indicator for capacitor failure. Useful conclusions are presented both for power system operators and manufacturers. The methodology used in this study also applies to other equipment in the distribution system such as oil switches, transformers and insulators.

Survey of harmonic voltage and current at distribution substation in Northern Taiwan

This paper presents a survey of voltage and current harmonic distortion levels at 40 power transformers and 10 power capacitor units in Northern Taiwan. Through one year of measurements, about 12,000 sets of harmonic voltage and current data were recorded and analyzed. The types and levels of harmonics are shown in each power transformer which supplies different residential, commercial and industrial customers with various loads. At the same time, a suggestion is given to the representative value of the background level of harmonic voltages with 95% cumulative probability which is adopted by Taipower. In conclusion, the effects of harmonics on capacitors and power transformers are discussed.

Modulation and SSR tests performed on the BPA 500 kV thyristor controlled series capacitor unit at Slatt substation

Field experience is reported for a thyristor controlled series capacitor (TCSC) recently commissioned at BPA's Slatt substation. Subsynchronous resonance tests show that TCSC interactions with shaft dynamics of PGE's Boardman steam generator are well understood and are effectively avoided by normal TCSC valve firing logic. Modulation tests, performed with the Boardman plant offline, show that the TCSC can be a powerful and responsive actuator for swing damping. Security considerations did not permit lightly damped operation of the controlled plant. Close analysis indicates that the TCSC damping contribution, though small, was measurable. The best estimate is that damping for the McNary mode is 7.33% and 8.55%, for the TCSC damper loop open and closed respectively. TCSC testing and monitoring is facilitated by an advanced interactive measurement network representing BPA's approach to the information requirements of major control systems.