Electrical Isolation Research Articles

The Optimal Control Method of Test Power Supply for DC Distribution Network

Background:: The test power supply is one of the key devices in the DC distribution network, which is necessary to supply power with high quality for testing other devices' performance. The double active bridge (DAB) converter is a common circuit topology for test power supply, which has the advantages of high-frequency electrical isolation, bi-directional power flow, and high power density. For the converter, control methods, such as single-phase-shift (SPS) control, and single-current stress or single-return power optimization under extended-phase-shift (EPS) control, have their limitations, which influences efficiency. Objective:: This paper aims to propose a dual-objective optimal control method, which can effectively improve efficiency of the test power supply. Methods:: This paper addresses the limitations of SPS control, and single-current stress or singlereturn power optimization under EPS control of the DAB converter, and proposes a dual-objective optimal control method based on the idea of using objective planning in the full power range under the condition of satisfying soft switching, which effectively improves efficiency of the test power supply. Results:: With the proposed dual-objective optimal control method, the converter achieves a smaller current stress similar to that with the single-current stress optimal control, and the return power is also reduced by 29.51%. Efficiency of the test power supply reaches 86.9%, which is better than 82.5% with SPS control and 85.3% with single-current stress optimization under EPS control. The experimental results fully verify the effectiveness of the proposed control method. Conclusion:: A dual-objective optimal control method is proposed. By using the presented method, current stress and return power are both optimally designed, so the efficiency of the test power supply can be effectively improved.

A Design and Construction of the Vibration Perception Threshold Measurement Device for Diabetes

A Design and Construction of the Vibration Perception Threshold Measurement Device for Diabetes

Safety and efficacy of the second-generation cryoballoon for left atrial appendage electrical isolation in canines.

Left atrial appendage electrical isolation (LAAEI) has demonstrated a significant enhancement in the success rate of atrial fibrillation (AF) ablation. Nevertheless, concerns persist about the safety of LAAEI, particularly regarding alterations in left atrial appendage (LAA) flow velocity and the potential risks of thrombus. This study aimed to assess the efficacy and safety of LAAEI, investigating changes in LAA flow velocity in canines. The study comprised a total of 10 canines. The LAAEI procedure used by a 23 mm cryoballoon of the second generation was conducted at least 180 s. Intracardiac ultrasonography (ICE) was employed to quantify the velocity flow of the LAA both prior to and following LAAEI. Following a 3-month period, subsequent evaluations were performed to assess the LAA velocity flow and the potential reconnection. Histopathological examination was conducted. Left atrial appendage electrical isolation was effectively accomplished in all canines, resulting in a 100% acute success rate (10/10). The flow velocity in the LAA showed a notable reduction during LAAEI as compared with the values before the ablation procedure (53.12 ± 5.89 vs. 42.01 ± 9.22 cm/s, P = 0.007). After the follow-up, reconnection was observed in four canines, leading to a success rate of LAAEI of 60% (6/10). The flow velocity in the LAA was consistently lower (53.12 ± 5.89 vs. 44.33 ± 10.49 cm/s, P = 0.006), and no blood clot development was observed. The histopathological study indicated that there was consistent and complete injury to the LAA, affecting all layers of its wall. The injured tissue was subsequently replaced by fibrous tissue. The feasibility of using cryoballoon ablation for LAAEI was confirmed in canines, leading to a significant reduction of LAA flow velocity after ablation. Some restoration of LAA flow velocity after ablation may be linked to the passive movement of the LAA and potential reconnecting. However, this conclusion is limited to animal study; more clinical data are needed to further illustrate the safety and accessibility of LAAEI in humans.

Design of 3-level LLC converter voltage controller for wide input voltage fluctuations

The auxiliary power supply unit for railway vehicles delivers various power to the passenger car. Maintaining isolation between the catenary power line and the auxiliary power in the compartment is typically essential. To ensure electrical isolation, an efficient LLC resonant converter is utilized among isolated DC-DC converters. Generally, LLC resonant converter primarily employ PFM control method. However, there is a limitation in increasing the switching frequency at high input voltages, making it difficult to handle wide input voltage fluctuations from the overhead catenary power line. To overcome this limitation, the PFM control method is introduced alongside the existing PFM control method, resulting in the presence of two controllers. However, since these two controllers regulate the output voltage differently, there is a potential for output voltage overshoot due to significant input voltage fluctuations. This paper proposes a method that combines PFM and PWM controllers, along with feed-forward compensation, to address these issues. The effectiveness of this proposed method is validated through PSIM simulation and experimentation.

Analysis of the effectiveness of the latest 4th-generation cryoballoon catheters in pulmonary vein isolation using high-resolution mapping

BackgroundLong-term data showed that up to 27% of pulmonary veins are reconnected using cryoballoon ablation. This study aimed to evaluate the efficacy of the latest 4th-generation cryoballoon catheters using ultra high-resolution mapping. MethodsIn patients with atrial fibrillation, a standard pulmonary vein isolation (PVI) with the latest 4th-generation cryoballoon catheter (Arctic Front Advance PRO, Medtronic Minneapolis, USA) and the spiral mapping catheter (Achieve Advance, Medtronic, Minneapolis, MN, USA) was performed. Subsequently, high-resolution mapping was achieved using the novel multipolar grid mapping catheter (Advisor HD Grid SE, Abbott Laboratories, USA). Follow-up was obtained after 6 months by means of a 7-day Holter electrocardiogram. ResultsIn our study, acute PVI was successfully achieved in all 31 patients. The latest 4th-generation cryoballoon catheter is safe in the acute phase of PVI. Additional high-resolution mapping (mean points per map 21,001 ± 4911) using the multipolar grid mapping catheter enabled us to identify residual gaps only in the carina pulmonary vein region; therefore, no additional ablation was performed. Three of 31 patients (10%) presented with atrial arrhythmia recurrence always related with pulmonary vein reconnection; using high-resolution mapping had no additional benefit in identifying pulmonary veins in which reconnection will occur. ConclusionThe utility of additional high-density mapping, facilitated by the HD Grid catheter after PVI with the 4th-generation cryoballoon catheter do not substantiate a discernible advantage over conventional mapping methodologies, particularly, the spiral mapping catheter. Residual carinal conduction was observed in a substantial cohort of patients (48%), highlighting a persistent challenge in achieving complete electrical isolation.

Evaluation of left ventricular function in patients with mitral annular disjunction using speckle tracking echocardiography.

Mitral annular disjunction (MAD) is a structural abnormality characterized by the systolic detachment of the posterior mitral annulus and the ventricular myocardium. It is usually observed coexistent with mitral valve prolapse (MVP) and associated with a mechanical dysfunction despite preserved electrical isolation function of the mitral annulus. This study aimed to evaluate left ventricular (LV) function using speckle tracking echocardiography in MVP patients with MAD. This study was designed as a prospective, single-center study including 103 patients with MVP and 40 age- and sex-matched control subjects. Transthoracic echocardiography and cardiac magnetic resonance imaging were performed to assess LV function and MAD presence. MAD (+) MVP (n=34), MAD (-) MVP (n=69), and control (n=40) groups were enrolled in the study. Among the MVP patients, 34 (33%) had MAD. T-negativity in the inferior leads on electrocardiography was more frequent in the MAD (+) group than in the MAD (-) patients (4.3%vs. 20.6%, p=.014). Mitral regurgitation degree, Pickelhaube sign (17.6%vs. 1.4%, p=.005), and late gadolinium enhancement frequency (35.3%vs. 10.6%, p=.002) were significantly higher in MAD (+) patients. MAD (+) patients had significantly impaired global longitudinal strain (-23.1±2.1vs. -23.5±2.3, p<.001), basal longitudinal strain (BLS) (-19.6±1.5vs. -20.5±1.9, p<.001), Mid-Ventricular Longitudinal Strain (-22.2±1.7vs. -23.2±2.2, p<.001) and LA strain (-24.5±3.9vs. -27.2±3.6, p<.001) when compared to MAD (-) MVP patients, despite similar LV ejection fraction. All these values of MVP patients were also significantly lower than the control group. The mean MAD distance was 7.8±3.2mm in MAD (+) patients. Patients with two or more symptoms were higher in the MAD (+) group than in the MAD (-) group (4.3%vs. 44.1%, p<.001). This study demonstrated a significant decrease in longitudinal strain in MVP patients with MAD, indicating myocardial dysfunction. These findings suggest that MAD may contribute to LV dysfunction and highlight the importance of early detection in younger patients. Further research is needed to explore the functional implications and long-term outcomes of MAD.

A concurrent fault diagnosis method for electric isolation valves in nuclear power plants based on rule-based reasoning and data-driven methods

In order to improve the fault diagnosis ability of electric isolation valves in nuclear power plants, especially for the diagnosis of concurrent faults, a novel concurrent fault diagnosis method based on rule reasoning and data-driven methods is proposed in this study. The concurrent fault diagnosis method is divided into two layers: the rule-based reasoning layer and data-driven layer. In order to realize the diagnosis of most concurrent faults, the rule-based reasoning layer is established by a rule inference model according to the failure mode and effects analysis (FMEA) of the electric isolation valve. In order to diagnose concurrent faults with mutual interference of fault features that cannot be diagnosed by rule-based reasoning layer, the data-driven layer is established by variational mode decomposition (VMD) and fast independent component analysis (Fast-ICA) method to separate concurrent fault signals and gate recurrent unit (GRU) method to identify fault patterns. After testing on the electric valve test bench and simulation data, multiple concurrent faults of the electric isolation valve are diagnosed accurately by the proposed concurrent fault diagnosis framework, including complex concurrent faults such as internal leakage and external leakage, and the framework can also work in a single fault diagnosis scenario without changing models. Compared with the concurrent fault diagnosis based on multi-label support vector machine, the accuracy of concurrent fault diagnosis is improved by about 25.3%. The research can provide a new idea for the concurrent fault diagnosis of electric isolation valves and other equipment.

A polymer trench filling based silicon isolation technique and its application to two-axis scanning comb-drive micromirrors

Electrostatic micromirrors can be widely used in LiDAR, displays, AR/VR and medical imaging. Electrically insulated silicon enabled by trenches filled with thermal oxide and polysilicon is commonly used for 2-axis electrostatic comb-drive scanning mirrors made on SOI (silicon-on-insulator) wafers. These trenches provide both electrical isolation and mechanical stability. However, this method has drawbacks such as high deposition temperature, voids, and high residual stress. In this work, a polymer filling method is proposed to form electrical insulation trenches in the silicon device layer of SOI wafers. Only low-temperature processes are used in this method and the silicon trenches can be fully filled up reliably. Furthermore, the filling polymer not only relieves residual stresses but also significantly increases the shock resistance of the micromirrors made with this method. In particular, Benzocyclobutene (BCB) is employed and a process has been developed to effectively fill deep silicon trenches. Using this method, two-axis electrostatic micromirrors have been successfully fabricated and tested. Experimental results show that the BCB-filled trenches demonstrate excellent electrical insulation performance and mechanical stability and the fabricated 2-axis mirrors can achieve a large field of view of 60°×40° and stand high impact over 2500 g.

Machine Learning Aided Optimization of P1 Laser Scribing Process on Indium Tin Oxide Substrates

Present study employes a picosecond laser (532 nm) for selective P1 laser scribing on the indium tin oxide (ITO) layer and subsequent fine‐tuning of P1 scribing conditions with machine learning (ML) techniques. Initially, the scribing is performed by varying different laser parameters and further evaluate them via an optical microscope and two probe resistivity measurements. The corresponding scribing width and sheet resistance data are used as input databases for ML analysis. The classification and regression tree (CART)‐based ML analysis revealed that median pulse energy &lt;5.7 μJ insufficient to separate the adjacent scribing regions. While pulse energy &gt;5.7 μJ, APL &gt; 35%, LSO &gt; 46%, and processing speed ≥1250 mm s−1 gives ≥16 μm of scribing width. Further, the decision tree (DT) analysis showed that pulse energy of ≥8.1 μJ, and LSO ≥ 37% are required for electrically isolated lines. The feature importance score suggests that laser fluence and pulse energy determined the scribing width, whereas electrical isolation strongly depends on LSO and processing speed. Finally, the ML achieved conditions experimentally validated and reassessed via scanning electron microscope, and atomic force microscopy aligns well with optical microscope measurements.

Practicality and Safety of Electrical Pulmonary Vein Isolation and Left Atrial Appendage Ligation in Lung Transplant Recipients With Pretransplant Atrial Fibrillation.

Lung transplant surgery creates surgical pulmonary vein isolation (PVI) as a routine part of the procedure. However, many patients with pretransplant atrial fibrillation continue to have atrial fibrillation at 1 y. We hypothesized that the addition of electrical PVI and left atrial appendage isolation/ligation (LAL) to the lung transplant procedure restores sinus rhythm at 1 y in patients with pretransplant atrial fibrillation. We retrospectively reviewed all adult lung transplant recipients at the University of California Los Angeles from April 2006 to August 2021. All patients with pretransplant atrial fibrillation underwent concomitant PVI/LAL and were compared with lung transplant recipients without preoperative atrial fibrillation. In-hospital outcomes; 1-y survival; and the incidence of stroke, cardiac readmissions, repeat ablations, and sinus rhythm (composite endpoint) were examined at 1 y for the PVI/LAL cohort. Sixty-one lung transplant recipients with pretransplant atrial fibrillation underwent concomitant PVI/LAL. No patient in the PVI/LAL cohort required cardiac-related readmission or catheter ablation for atrial fibrillation within 1 y of transplantation. Freedom from the composite endpoint of death, stroke, cardiac readmission, and repeat ablation for atrial fibrillation at 1 y was 85% (95% confidence interval, 73%-92%) for lung transplant recipients treated with PVI/LAL. The addition of PVI/LAI to the lung transplant operation in patients with pretransplant atrial fibrillation was safe and effective in maintaining sinus rhythm and baseline risk of stroke at 1 y.

Cardiac Pulsed Field Ablation Lesion Durability Assessed by Polarization-Sensitive Optical Coherence Reflectometry.

Pulsed field ablation uses electrical fields to cause nonthermal cell death over several hours. Polarization-sensitive optical coherence reflectometry is an optical imaging technique that can detect changes in the tissue ultrastructure in real time, which occurs when muscular tissue is damaged. The objective of this study was to evaluate the ability of a polarization-sensitive optical coherence reflectometry system to predict the development of chronic lesions based on acute changes in tissue birefringence during pulsed field ablation. Superior vena cava isolation was performed in 30 swine using a biphasic, bipolar pulsed field ablation system delivered with a nonirrigated focal tip catheter. Acute changes in tissue birefringence and voltage abatement were analyzed for each individual lesion. A high-resolution electroanatomical map was performed at baseline and 4 to 12 weeks after ablation to locate electrical gaps in the ablated area. A total of 141 lesions were delivered and included in the analysis. Acute electrical isolation based on the electroanatomical map was achieved in 96% of the animals, but chronic isolation was only seen in 14 animals (46%). The mean voltage abatement of lesions that showed recovery was 82.8%±14.6% versus 84.4%±17.4% for those that showed fibrosis (P=0.7). The mean acute reduction in tissue birefringence in points demonstrating fibrosis was 63.8%±11.3% versus 9.1%±0.1% in the points that resulted in electrical gaps. A threshold of acute reduction of birefringence of ≥20% could predict chronic lesion formation with a sensitivity of 96% and a specificity of 83%. Acute tissue birefringence changes assessed with polarization-sensitive optical coherence reflectometry during pulsed field ablation can predict chronic lesion formation and guide the ablation procedure although limited by the tissue thickness.

Probing Leakage Current Suppression Techniques for Non-Isolated Photovoltaic Inverters

The evolution of photovoltaic (PV) inverters has witnessed distinct trade-offs between isolated and non-isolated configurations. While isolated PV inverters grapple with challenges such as increased volume and suboptimal system efficiency due to transformer inclusions, their non-isolated counterparts offer a solution by eliminating these transformers. However, this lack of electrical isolation in non-isolated inverters engenders a distinct predicament: significant leakage currents. Such currents not only impede system operation but also curtail operational efficiency. Recognizing this, the suppression of leakage current has catapulted to the forefront of contemporary research. This manuscript elucidates the operational intricacies of non-isolated PV inverters. It then embarks on a panoramic review of prevailing leakage current suppression techniques, both domestic and international, contextualizing them with state-of-the-art inverter topologies such as the H7, H10, three-level neutral point clamped (NPC) and three-phase four-bridge arm configurations. The paper culminates with a prospective glance at future research trajectories in leakage current suppression, proffering seminal recommendations for academic and industry fraternities.

A Wide-Output-Range DC-DC Converter and Minimum Loss Collaborative Control Strategy

In response to the challenges faced by traditional LLC resonant converters in simultaneously achieving a wide output voltage and high efficiency, this paper proposes a cascaded DC-DC converter. The front stage of the converter adopts a new LLC topology, and it is cascaded with a boost converter through a reutilization of the output-side inductor. The proposed DC-DC converter leverages the electrical isolation and wide output voltage range advantages of LLC and boost converters, enabling the overall system to achieve broad output voltage regulation and high-efficiency operation. The reutilization of the inductor design further enhances the integration density of the DC-DC converter. A minimum loss collaborative control strategy is introduced for the proposed DC-DC converter. When determining the output voltage and operating the circuit in step-up mode, the duty cycles of the switch in the proposed LLC converter and the switch in the boost converter are adjusted to minimize overall circuit losses while ensuring the rated output voltage. Ultimately, the correctness and practicality of the proposed DC-DC converter and its control strategy are validated through a simulation and an experiment. The overall efficiency of the DC-DC converter can reach up to 94% under optimal conditions.

Outcomes of pulmonary vein electrical isolation in patients younger than and older than 70 years

Outcomes of pulmonary vein electrical isolation in patients younger than and older than 70 years

Innovative Engineering Solutions for Short Neutral Section Maintenance Reduction in Railway Overhead Lines

This work addresses the challenges associated with the development of short neutral sections (SNS) for overhead lines of high-speed moving trains. A crucial function of a short neutral section is to provide electrical isolation between the different phases of AC traction. These sections are typically located in proximity to the traction substation and sectioning posts. The current SNS design presents several issues, including pantograph arcing, wear and tear of the overhead line system, and the need for manual rotation during periodic maintenance. To address these challenges TRIZ is used, a problem-solving methodology that leverages inventive principles to generate innovative solutions. The work outlines the use of several TRIZ tools and techniques, including the Interaction Matrix, Functional Analysis, Function-Body Diagram (FBD), Trimming, and the Contradiction Matrix [1]. With the application of these tools, the author presents several potential solutions for improving the SNS design to eliminate periodic maintenance and services. One proposed solution involves the use of a segmented overhead line system with an insulating cylinder-shaped discrete insulator to ensure smooth contact of the pantograph. Another solution involves the use of a twisted strip-based insulator to replace linear motion with rotating movement, eliminating the need for manual rotation. The work emphasizes the importance of considering various factors, such as design, material, wear rate, maintenance, and creepage distance, when evaluating the feasibility of these solutions. By leveraging TRIZ to generate innovative solutions, the author demonstrates the potential of this methodology to drive innovation and overcome complex challenges in the development of short neutral sections for high-speed rails.

Outcomes of pulmonary vein electrical isolation in patients younger than and older than 70 years

The objective of this study is to compare the clinical characteristics and outcomes of contemporary cohorts of patients undergoing catheter ablation for atrial fibrillation (AF), stratified by age (< 70 years and ≥ 70 years). This retrospective cohort study included patients who underwent catheter ablation for refractory AF. The minimum follow-up duration per patient was 12 months. A total of 239 patients were included in the study, with 171 (71.5%) in the < 70 years group and 68 (28.5%) in the ≥ 70 years group. The mean age of the study population was 62.4 years (SD 10.87). The < 70 years group had a mean age of 58.03 years (SD 9.71), while the ≥ 70 years group had a mean age of 73.4 years (SD 3.05). Furthermore, a higher proportion of paroxysmal AF was observed in patients < 70 years, whereas a higher proportion of persistent AF was found in patients ≥ 70 years. These differences were statistically significant. The recurrence rates after the initial ablation procedure were similar between the two groups (21.43% in the < 7 0 years group vs. 23.53% in the ≥ 70 years group, p = 0.79). Additionally, there were no significant differences in terms of complications. The < 70 years group experienced 18 complications, while the ≥ 70 years group had 5 complications (p = 0.472). The findings of this study suggest that patients aged 70 years and older who undergo their first catheter ablation procedure for AF demonstrate similar clinical outcomes compared to patients younger than 70 years.

Hybrid LLC Resonant Converter With Partial-Power Auxiliary Unit for Improved Performance

DC-DC converters used in on-board chargers (OBC) of electric vehicles need to meet the requirements of high efficiency, wide output range, and electrical isolation. In this paper, a partial-power processing topology with a wide output range is proposed to overcome the drawbacks of traditional single-stage and two-stage LLC converters. The LLC resonant converter operates near the resonant frequency to maintain high efficiency. While only the partial power is processed by the Buck converter to offer the wide-range output voltage capability. The triangular current mode (TCM) operation is implemented in the Buck converter to minimize the efficiency sacrifice. In addition, to reduce the adverse effect of the second harmonic voltage ripple (SHVR) generated by the AC port on the LLC resonant converter in OBC. A ripple compensation method is proposed to eliminate the SHVR of the LLC resonance converter. Through the dual predictive control for the Buck converter, the SHVR of the LLC resonant converter is offset by the Buck converter. A 2kW rated experimental prototype is designed to convert 400V wide input to 200-500V output. The prototype demonstrates more than 96% efficiency from 30% load to full load at 60-120V input and a 98.2% peak efficiency.

Study pertaining to leak simulations in electrical leak location dipole testing. A better understanding of dipole testing calibration using various plate sizes and shapes

According to standard ASTM D7007 for geoelectrical leak location (ELL) surveys on earth materials, a hole simulation or calibration must be performed before starting the actual survey. The standard also states that a 1/4 in diameter metal plate must be detectable based on specific signal strengths, if not, the survey cannot be considered completed by the ASTM standard and must be conducted on a 1 m x 1 m grid. Most ELL companies only perform the 1/4 inch test to see if the surveying speed will be fast or slow. The better the signal, the larger the grid, the faster the survey. Usually, leak location practitioners will then proceed to the leak location either way. The number of projects that fail the 1/4 inch test is quite important, so how do we push things further to ensure the best efficiency on site? What information is necessary to understand how the site responds to the test and what can we do to improve the quality of the survey? Here we will compare data gathered within 11 years with various calibration plate sizes and will explain the effects of field specific parameters, such as the simulation’s position, moisture, thickness, cover material homogeneity, and the most important factor of all: peripherical electrical isolation.

Диагностическое устройство одноэлементных изоляторов воздушной линии электропередачи по температуре

Insulator, electrical device designed for electrical isolation and mechanical fastening of electrical installations or their separate parts, which are under different electrical potentials. As an element of the power system, it plays an important role in ensuring its reliable operation. At present the issue of diagnostics and monitoring of insulators is still topical. The article provides statistical data of failures on overhead lines and lists methods and devices for detecting insulation damage. The research problem is the lack of a reliable and cost-effective device for early detection of insulator failure under voltage. The solution is the previously proposed method of diagnosing single-element insulators by temperature. The author proposed a scheme of the diagnostic device, described its principle of operation in normal and emergency modes. The diagnostic device made according to the proposed scheme is simple, works under voltage and without the intervention of operating personnel.

Constructing a zero leak landfill cell

Engineered landfill barriers are the last line of defence in protecting precious groundwater resources from contamination. A landfill cell without any leaks at the conclusion of construction is the exception rather than the rule. From design to materials testing to installation practices and contractor care, all of these elements contribute to both the short and long-term integrity of the lining system. Electrical leak location (ELL) methods can be used to detect leaks in installed landfill cells after construction so that leaks can be repaired before a landfill cell begins filling operations. However, the thorough testing of landfill cells using ELL can be complicated by their complex configuration. The dipole method, employed after cover material placement, requires electrical isolation of the cover material, which is difficult to achieve with a landfill expansion cell configuration. Additionally, employing only this type of testing can leave the tie-in area untested, which is a critical area prone to damage. This paper provides solutions for complete landfill expansion cell testing, including a relatively new testing methodology (ASTM D8265, [1]), which provides protocol for verifying that a geomembrane has been successfully installed with no leaks. A case study is included to show how ASTM D8265 can be used to provide documentation of a zero-leak condition of a landfill cell after construction. Common elements of design, geomembrane installation, and quality assurance are discussed in order to provide a road map of how to reach a zero-leak condition at the end of a landfill expansion cell construction project. This paper can be used as a guide to constructing a zero-leak landfill cell using state-of-the art construction practices and ELL testing methodologies.