Stray Capacitance Research Articles

Body-based capacitive coupling and conductive channel power transfer for wearable and implant electronics

Wearable and implant electronic devices have been widely utilized for healthcare and medicine. However, powering these devices for long duration with stable performance is extremely challenging. Here, we propose a body-based capacitive coupling and conductive channel power transfer (BC4PT) technology for this application. The BC4PT could unintentionally harvest the 50/60 Hz electricity using daily electronic devices. Large stray capacitances exist between electronic device such as phones and hand. When a person uses a plugged-in device, a high amount of 50/60 Hz electricity could be coupled to the hand, and transferred to wearable devices via the body conductive channel. The BC4PT could light up a 120 LEDs array directly, charge a 1mF capacitor to ∼ 23 V in 10 min. The harvested energy is utilized to power a wireless multivariable physiological sensor chip continuously or an implant device via the resonance-coupled wireless power transmission. The technology has a great application prospect for the self-powered wireless wearable and implant systems.

Effect of Stray Capacitance in a Distribution Network on the Accuracy of Fault Location Based on Electromagnetic Time Reversal Method

The existing electromagnetic time reversal (EMTR) method for determining the location of faults in a distribution system does not consider stray capacitors in the system, leading to inaccurate fault location results. In this article, the influence of stray capacitors at the end and middle of the line on the EMTR method without considering the capacitance in the backward-time process was analyzed, the current signal energy of the fault location was derived, and the fault location was determined. A reduced-scale experimental platform of the EMTR method was built, and the influence of stray capacitors at observation points and middle of lines on the fault location results was verified. Finally, a fault location platform for a 33-node distribution network was built in power systems computer aided design (PSCAD) to explore the impact of stray capacitance on the fault location accuracy. The results showed that the error increases with the increase of the stray capacitance. This article found that considering the stray capacitance in the backward-time process can help determine the fault location more accurately. Besides, the signal observation point setting at low time constant area can also improve the accuracy when stray capacitance cannot be determined.

Analysis and Design of Bidirectional Parallel-Series DAB-Based Converter

Unprecedented expansion of renewable, energy storage and fast charger system applications has diversified the bidirectional converter designs over the past decade. This paper presents a new dual-active bridge (DAB) converter topology which employs parallel and series switches arrangements for low-voltage (LV) bridge configurations. The additional switch inclusion provides high dc conversion gain, which enables attractive fast charger applications. The performance of the proposed DAB-based converter with wide dc range has been investigated through several design techniques and comparisons. The use of use of silicon carbide devices (SiC) in higher power conversion significantly improves switching losses. However, unsupervised design will result in significant switching losses and increased electromagnetic emissions. Since the DAB-based converter's high switching frequency allows operation with smaller magnetics, the system stray capacitance plays a critical role. The common-mode current (CMC) propagated through the system's stray capacitance generates undesired electromagnetic interferences (EMI) and impacts the soft-switching achievable range. To overcome the common-mode current circulation issue, design solutions have been employed to reduce the emergence of system stray capacitance. A harmonic analysis is further discussed along with evaluation of transformer design comparisons. The experimental results show the performance of the DAB-based converter in bidirectional operation and improved common mode current generation with respect to EMI emissions. The simulation and experimental results have been performed using a 5kW rated power DAB-based converter with SiC power semiconductors.

A proposed optimized equivalent circuit and performance analysis of dielectric barrier discharge ozone generator

<span lang="EN-US">Traditionally, low-frequency power supplies are used in dielectric barrier discharge (DBD) ozone generators. These generators require a very high output voltage. This may limit ozone production due to limitations imposed by the dielectric strength of the insulating material. Low-frequency generators also present low efficiency, large volumes, and difficulty in controlling ozone production. On the other hand, the advantages of high frequency DBD ozone generators are the increased power density applied to the chamber electrodes, and the voltage applied to the ozone chamber decreases, allowing for higher ozone production efficiency. From this point of view, in order to enhance and control the DBD ozone generator operating at high frequency, it is necessary to determine all parameter values and optimize the equivalent model for this type of generator. This work presents and proposes the practical methodologies used to extract all parameters of the high voltage high frequency (HVHF) transformer which can be used in these systems. Resonant frequency control techniques are presented in this paper. Elimination of the stray capacitance effect will also be implemented in this paper.</span>

Capacitance Estimation for Electrical Capacitance Tomography Sensors Using Digital Processing of Time-Domain Voltage Response to Single-Pulse Excitation

In this paper, a new approach for capacitance measurement for electrical capacitance tomography (ECT) sensors is proposed. The method is based on the digital processing of the time-domain voltage measurements at the sensor electrodes. Furthermore, a robust capacitance estimation algorithm is developed to convert the measured voltage time-series to inter-electrode capacitances. The proposed measurement technique simplifies the electronic design of the ECT sensor and is suitable for use in applications requiring a compact device with a fast scan time. The accuracy and sensitivity of the method are investigated numerically and experimentally using a prototype sensor. In particular, the sensitivity of the estimated capacitance to measurement noise levels is analyzed in detail. Additionally, an analysis of the parameters that affect the accuracy of estimated capacitances is carried out from which we are able to demonstrate that the method is immune to effects such as stray capacitances between the electrodes and the ground. A prototype sensor with an open curved geometry on a millimeter scale is used to test the method empirically. Experimental results obtained for measurements with mineral oil and water are shown and compared against capacitances obtained using a physics-based forward model of the sensor. The inter-electrode capacitances in the range of tens of femtofarads to a few picofarads are estimated and a close match with the forward model results is obtained.

Stray capacitances influences of various parallel primary windings in input-series transformer-integration flyback converters

Stray capacitances influences of various parallel primary windings in input-series transformer-integration flyback converters

Assessment of traveling wave-based functions in inverter-based resource interconnecting lines

In this paper, the behavior of traveling waves (TWs) on transmission lines which interconnect inverter-based resources (IBRs) is investigated, assessing the performance of well-known TW functions applied in protection and fault location schemes. To do so, traditional synchronous generators and wind turbine-based IBRs of types III and IV are investigated, allowing comparative studies regarding the shape of fault-induced transients measured at the monitored line terminals. Then, the impacts of typical terminations of IBR-interconnecting lines on the classical double-ended TW-based fault location method, as well as on directional, overcurrent and differential TW-based protections are analyzed, highlighting the effects of busbar and transformer stray capacitances on the performance of these functions. The obtained results reveal that TW solutions are promising for IBR-interconnecting lines. However, a significant influence of busbar and transformer stray capacitances on the performance of TW functions is also identified, revealing the need for taking these capacitances into account during the definition of settings used in TW protection and fault location schemes.

Quasiepitaxial Aluminum Film Nanostructure Optimization for Superconducting Quantum Electronic Devices

In this paper, we develop fabrication technology and study aluminum films intended for superconducting quantum nanoelectronics using AFM, SEM, XRD, HRXRR. Two-temperature-step quasiepitaxial growth of Al on (111) Si substrate provides a preferentially (111)-oriented Al polycrystalline film and reduces outgrowth bumps, peak-to-peak roughness from 70 to 10 nm, and texture coefficient from 3.5 to 1.7, while increasing hardness from 5.4 to 16 GPa. Future progress in superconducting current density, stray capacitance, relaxation time, and noise requires a reduction in structural defect density and surface imperfections, which can be achieved by improving film quality using such quasiepitaxial growth techniques.

A Carrier-Based Discontinuous PWM for an 80 Kw PV Inverter With the Reduction of the DC-Link Voltage Ripple and Common Mode Current

Discontinuous pulse width modulation (DPWM) method is broadly used in three-phase inverter to achieve high efficiency through the reduction of the switching loss. The high-power rating photovoltaic (PV) inverter with DPWM has its intrinsic issues such as large DC-link voltage ripple and high-frequency resonant current due to the large stray capacitance proportional to the power rating. To extend the application of DPWM from 10 kW to 80 kW PV inverter, a new DPWM method (DPWMn) which divides the clamping period into <i>n</i> intervals is proposed to achieve the three objectives simultaneously: 1) reduction of the DC-link voltage ripple; 2) suppression of the high-frequency current oscillation; 3) improve the efficiency compared to the continuous space vector PWM (SVPWM). The proposed DPWMn is validated by an 80 kW three-phase T-type PV inverter. Compared to the SVPWM, the DPWMn has reduced 30&#x0025; switching loss while maintaining the similar power quality and the common mode current. Compared to the existing DPWM methods, DPWMn reduces the voltage ripple by 52&#x0025; and has the minimum energy ripples. Furthermore, the carrier-based DPWMn only utilizes the measured voltage and can be easily implemented.

Analytical Methods for Estimating the Equivalent Stray Capacitance of Single-Layer Core Windings

The analytical methods for estimating the equivalent stray capacitance (ESC) in a single-layer iron core winding include the capacitance network method (CNM) and the energy equivalence method (EEM). The CNM is limited to applications in symmetrical windings, and the EEM is restricted to use in multiconductor systems (MCSs) with fully known potential distributions. These methods are improved in this paper. The winding symmetry limitation of the CNM is eliminated, and the EEM is used to calculate the ESC of MCSs containing floating potential conductors. ESC calculations are found to differ between the CNM and the EEM. The accuracies of the hypotheses used in the CNM and the EEM and the ESCs calculated with each approach are assessed and compared based on finite element simulations, circuit simulations and experiments. The results show that at the first resonant frequency condition, the EEM hypothesis is more consistent with reality than that of the CNM, and the ESC calculated with the EEM is more accurate. The ESC errors incurred when using the CNM and the EEM are mainly due to model errors introduced by the discrepancies between the assumptions and the actual conditions.

High-frequency oscillation mechanism analysis of wind farm-side MMC station considering converter transformer stray capacitance

High-frequency oscillation is one of the critical issues threatening the stability of modular multilevel converter (MMC) based high-voltage direct current (HVDC) system. A new 2 kHz high-frequency oscillation has occurred in the wind farm-side MMC station of Rudong wind farm integrated MMC-HVDC project of China during no-load charging process. The mechanism of this high-frequency oscillation is different to previous ones. Apart from the time delay of MMC, the stray capacitance of converter transformer makes a significant contribution to the high-frequency oscillation. This paper investigates the high-frequency oscillation mechanism of wind farm-side MMC station during no-load charging process. First, the harmonic state space (HSS) model of a wind farm-side MMC station is established. In addition to the leakage inductance, the stray capacitance is considered in the converter transformer model. To reveal the significance of the converter transformer stray capacitance in this new high-frequency oscillation, the root loci of the system are calculated with varying stray capacitance. Then, the state variables with high degree of participation in the high-frequency oscillation modes are determined by the participation factor analysis. A reduced-order model suitable for the high-frequency oscillation analysis is further established based on the participation factor analysis results. Next, the high-frequency oscillation mechanism is revealed by impedance analysis. Finally, the effects of system parameters are analyzed by the combination of eigenvalue analysis and impedance analysis. The analysis results are validated by electromagnetic transient simulations.

In-air experimental achievement of high-voltage DC power supply to be installed in a tandem electrostatic accelerator system for boron neutron capture therapy application.

The boron neutron capture therapy (BNCT) system developed by the Korea Institute of Radiological and Medical Sciences is a compact neutron source that can be installed at medical institutes. The target energy was accelerated to a maximum of 2.4 MeV-20 mA by introducing a gas stripping device that converts negative hydrogen ions into positive ions. By using the tandem-type accelerator in this way, a high-voltage DC power supply was designed with 1.2 MV-45 mA as the maximum capability. The design was improved to reduce the number of stages of a Cockcroft-Walton voltage multiplier. Hence, the ripple risk of the DC flat top resulting from unwanted stray capacitance was lowered. The overall height and volume of the Cockcroft-Walton voltage multiplier were reduced to less than half those of the existing design method, making miniaturization possible. After such advanced design and manufacturing, performance tests were performed at 750 kV-45 mA under 23 stages of the Cockcroft-Walton voltage multiplier, which is the highest level that can perform at its maximum under in-air conditions. It demonstrated stable performance under in-air conditions without breakdown for 2h, even at 620 kV-35 mA. To reach the final target of 1.2 MV-45 mA, the groundwork is laid for achieving experimental performance while satisfying the optimal requirements in SF6 gas.

Equivalent circuit of high frequency inductor to consider eddy currents and resonance

The resistance and inductance of an inductor working at high frequencies depend on frequency because of eddy currents caused by the skin and proximity effects. In addition, the stray capacitance among winding coils would give significant influence. This paper proposes an equivalent circuit model which can consider the displacement and eddy currents simultaneously in frequency and time domain. In the proposed circuit model, the capacitance and complex inductance are determined by solving electrostatic and magnetostatic equations with finite element method (FEM). It is shown that the input impedance of an air-core coil is consistent with that computed by FEM at low frequencies. Moreover, the former is shown to be consistent with the measured result.

A New Electrical Resistance Measurement Method of Carbon Fiber-Reinforced Polymer Tubes Based on C⁴D Technique

This work introduces the capacitively coupled contactless conductivity detection ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{C}^{{4}}\text{D}$ </tex-math></inline-formula> ) technique into nondestructive testing (NDT) of carbon fiber-reinforced polymer (CFRP) and proposes a new resistance measurement method of CFRP tubes. The proposed method does not require direct contact between the electrodes and the carbon fiber. Therefore, the electrical resistance of CFRP can be measured without the treatments required by traditional electrical methods that may lead to surface or structural damage. The equivalent circuit model of the new method is established, and the challenges are analyzed. Simulation and experiment are conducted with woven fabric CFRP tubes to verify the feasibility of the proposed method, including the range of workable frequency, the effectiveness of the circuit model, and the capability of damage detection. Research results show that a relatively high working frequency is required to accurately measure the interested resistance and sense the resistance change. By selecting a workable frequency, the effectiveness of the circuit model is verified. Research results indicate that the stray capacitance between the electrodes has little effect on resistance measurement, and the capacitor–resistor–capacitor model is still applicable. Research results also verify the feasibility of the proposed method for damage detection. It is able to sense the resistance change resulted from the damage of CFRP, either the conductivity changes in simulation or actual cutting damage in experiment.

On the Application of Extended Grounded Slot Electrodes to Reduce Noncirculating Bearing Currents

Power-electronic-converter-induced motor bearing currents are a widespread problem in the field of electrical drives. Parasitic capacitances between the electrical machine's parts provide a path for leakage currents, which finally harm metallic ball bearings. Remembering that end-windings have a significant contribution in building up stray capacitances, a countermeasure affecting both the lamination stack and end-winding areas is needed. This article focuses on a countermeasure against the noncirculating bearing currents in the cluster of solutions at the motor side. The electrostatic shielding approach, which is a known principle to reduce capacitive couplings, is applied in electrical machines every now and then. In this article, the principle of slot-embedded grounded electrodes is extended to cover also the end-windings. Thus, the electrodes provide a better shaft-to-ground voltage mitigating effect compared to the case where electrodes are applied only in the lamination stack area. The feasibility and effectiveness of such a countermeasure are investigated. Different options in terms of scaling of both the machine size and diameter of the electrodes were analyzed and corresponding conclusions were pointed out.

Power Decoupling Rectifier With Common-Ground Concept for Lighting Applications

The lightweight and the electrolytic capacitor-less are the development trends of microconverters for transportation lighting applications. Some solutions available to address the power fluctuations are caused by electrolytic capacitor-less. However, the leakage currents caused by nonisolated converters have been little studied. Given this, an improved transformerless single-phase rectifier based on the virtual dc-bus concept is proposed in this letter. This solution connects the negative of the LED array directly to the grid neutral, thus shorting the stray capacitance to the ground, suppressing leakage currents, and improving system reliability. In addition, the active pulsating power buffering solution is introduced with only one additional power switch due to the sharing of cells. Finally, the experimental results verify the correctness and superior performance of the proposed solution.

A Novel Single Phase Three Level Triple Boost CG Switched-Capacitor Based Grid-Connected Transformerless PV Inverter

A new three-level inverter based on the switched capacitor (SC) with a common grounding (CG) configuration has been introduced in this article, which is capable of boosting the input voltage up to three times. Therefore, this inverter is configured without any boost dc/dc converter stage for low voltage PV application. To step up the input PV voltage and facilitate three level in output voltage, two SC cells are connected in parallel. This inverter's common grounding configuration helps in bypassing the stray capacitance, which eliminates the leakage current and consequently reduces electro-magnetic interference (EMI) considerably. Hence, for electro-magnetic compatibility (EMC), this inverter does not require any EMI filter. Additionally, this inverter handles reactive power during the grid's lagging/leading power factor (pf) condition. A proportional resonant (PR) current controller is designed to regulate active and reactive grid power. The proposed modulation strategy helps in balancing capacitor voltages at their base values with allowable ripple. The inverter circuit details, control technique, PWM scheme, thermal modeling, and loss analysis with component design guidelines are described in detail. Experimental results are presented to validate the effectiveness and feasibility of this proposed inverter.

전기저장장치의 배터리 기생커패시턴스 및 SOC에 따른 절연저항 변동 메커니즘 및 모델링에 관한 연구

Recently, due to the significant growth of RES(renewable energy source), the capacity of ESS (energy storage system) interconnected to RES is increasing rapidly. Especially, it is mandatory to install IMD (insulation monitoring device) in order to monitor insulation resistance of ESS and detect faults such as ground fault. However, there are no specific regulations on numerous IMD being operated in actual ESS, and particularly the issues that insulation resistance dramatically varies depending on the stray capacitance and SOC (state of charge) of batteries are being occurred in large scaled ESS. Therefore, in order to operate ESS in a stable manner, this paper performs surveys on actual measurement data of ESS insulation resistance, which varies according to the operation environment and conditions in distribution system. Based on the evaluation on influence of stray capacitance and SOC to insulation resistance from the survey results, this paper proposes a mechanism of variation in insulation resistance depending on the stray capacitance and SOC of battery and performs modeling of DC distribution system with ESS to evaluate the variation characteristics of insulation resistance according to each mechanism. From the simulation result based on the proposed mechanism and modeling, it is confirmed that the leakage current and CMV (common mode voltage) increases along with stray capacitance and SOC but insulation resistance decreases. Therefore, in order to operate large scaled ESS in a stable manner, it is confirmed that proper measures to enhance insulation level depending on the capacity and SOC of battery and mitigate leakage current and CMV.

A study of the signal rising edge produced by a charge sensitive preamplifier connected to a 4H-SiC detector

In a general semiconductor detector system, the output amplitude of the charge-sensitive preamplifier (CSA) is proportional to the total charge induced by incident particles. The rising edge of the output signal provides information on the input current. The shape of the rising edge is not only affected by the carrier drifting but the discharge process of the equivalent capacitance (the detector capacitance and the capacitance caused by the detector package and the connecting cable, namely the stray capacitance) and the input resistance of the CSA. The equivalent capacitance and the input resistance often has a time constant of tens nanoseconds, which significantly affects the rising edge, particularly for fast detectors such as silicon carbide or diamond. This paper describes an α-particle testing system based on a Schottky 4H-SiC detector. The junction capacitance of the detector can be adjusted by changing the bias voltage, and the derivative waveforms of the CSA output are analyzed using an equivalent circuit. The results show that the falling edge of the derivative waveform corresponds to the discharge process of the equivalent capacitance and the input resistance in the circuit. The parameters of the detector capacitance, the stray capacitance and the input resistance can be obtained through fitting the decay time. The duration of the induced current of the detector can be measured from the rising edge of the derivative waveform. By comparing the theoretical and the measured value, the carrier mobility at different bias voltages can be derived.

Accounting for stray capacitances in impedance measuring cells — A mandatory step in the investigation of solid ion conductors

The determination of the dielectric response properties is essential to the investigation of solid ion conductors. The stray capacitance contributions of the measuring cell must be systematically determined and subtracted from the acquired data. Hereby, we report and discuss a general method that can be used for the accurate determination of stray capacitance in impedance measuring cells. Our method can be applied to all commercial or custom-made impedance cells or sample holders used for variable temperature conductivity measurements of fast ion conductors. After the description of the method, we present the experimental calibration done for a 2032-type coin cell sample holder. The 2032-type coin cell is a highly reliable sample holder for impedance measurements of air sensitive materials. We tested the method on a known sample and we validated it by comparing with the results obtained in a simple reference configuration. Our simple, efficient and robust method for the determination of parasitic capacitive contributions may serve as an example of good practice in the field of solid electrolytes, solid state batteries and dielectric materials investigations.