High Voltage Research Articles

Partial discharge characteristics of thermally aged mineral oil and eco-friendly vegetable oil under uniform electric field

Partial discharge (PD) detection plays an important role in the life assessment of liquid insulation in transformers. This paper investigates on the PD activity and characteristics in thermally aged mineral oil and eco-friendly rice bran and Sesame oils. To simulate surface discharges, plane-plane electrode configuration with pressboard of 1mm and 3mm thickness was used. The phase resolved PD patterns of thermally aged rice bran oil, sesame oil and mineral oil with pressboard were recorded and analyzed. From the results it is observed that the inception voltage of eco-friendly vegetable oils is higher than mineral oil. Also vegetable oil shows better PD characteristics hence they can be used for high voltage insulation applications.

Imine-Based Polymeric Mixed Ionic-Electronic Conductors Featuring Degradability and Biocompatibility for Transient Bioinspired Electronics.

Degradable features are highly desirable to advance next-generation organic mixed ionic-electronic conductors (OMIECs) for transient bioinspired artificial intelligence devices.It is highly challenging that OMIECs exhibit excellent mixed ionic-electronic behavior and show degradability simultaneously.Specially,in OMIECs,doping is often a tradeoff between structural disorder and charge carrier mobilities. Here, we describe a regiochemistry-driven backbone curvature approach to prepare OMIECs, enabling doped state ordered within efficient ionic-electronic conduction in organic electrochemical transistors (OECTs) and presenting degradable characteristics. Significantly, i-3gTIT shows an outstanding mobility (1.99 cm2 V-1 s-1) and μC* (302 F V-1 cm-1 s-1), and presents higher disorder-tolerance upon doping and faster degradation behavior than its regioisomer, o-3gTIT. Especially, the resulting OECT-based inverter shows a high voltage gain of 31.6 V V-1 at a low driving voltage of 0.6 V. Moreover, we demonstrate an application of transient OECT, i.e., biodegradable solid-state electrolyte of OECT-based artificial synapses. Remarkably, the regiochemistry-driven film crystallinity modulation enables the conversion from volatile to non-volatile operation in such synapses. The transient synapse based on i-3gTIT achieves over 90% recognition accuracy for small digit handwritten images, showing potential in security neuromorphic computing. Our work is the first presentation enabling excellent mixed conduction of OMIECs with degradable features for transient bioinspired electronics.

Use of Resonant Acoustic Fields as Atmospheric-Pressure Ion Gates.

Ion optics are crucial for spectrometric methods such as mass spectrometry (MS) and ion mobility spectrometry (IMS). Among the wide selection of ion optics, temporal ion gates are of particular importance for time-of-flight MS (TOF-MS) and drift-tube IMS. Commonly implemented as electrostatic ion gates, these optics offer a rapid, efficient means to block ion beams and form discrete ion packets for subsequent analysis. Unfortunately, these devices rely on pulsed high voltage sources and are not fully transparent, even in their open state, which can lead to ion losses and contamination. Here, a novel atmospheric-pressure ion gate based on a resonant acoustic field structure is described. This effect was accomplished through the formation of a resonant, standing acoustic wave of alternating nodes and antinodes. Alignment of an atmospheric-pressure gaseous ion beam with an antinode, i.e. a region of transient pressure, of the acoustic structure acted as a gate and blocked ions from impinging on ion-selective detectors, such as a mass spectrometer and a Faraday plate. The velocity of the ion stream and acoustic power were found to be critical parameters for gating efficiency. In the presence of an acoustic field (i.e., a closed gate), ion signals decreased by as much as 99.8% with a response time faster than the readout of the ion-measurement devices used here (ca. 75 ms). This work demonstrates the basis for a low-cost, acoustic ion gate, which is optically transparent and easily constructed with low-power, off-the-shelf components, that could potentially be used with MS and IMS instrumentation.

Dimensional Regulation of Organic n-Type Dopants for Highly Efficient Perovskite Solar Cells and Modules.

A strong n-type perovskite layer is crucial in achieving high open-circuit voltage (VOC) and power conversion efficiency (PCE) in the p-i-n solar cells, as the weak n-type perovskites result in a loss of VOC, and the p-type perovskites contain numerous electron traps that cause the severe carrier recombination. Here, three types of perylene diimide (PDI) based small molecule dopants with different dimensions, including 1D-PDI, 2D-PDI, and 3D-PDI are designed, to produce heavier n-type perovskites. The PDI-based molecules with Selenium atoms have a strong electron-donating ability, effectively enlarging the quasi-Fermi level splitting within the perovskites. Besides, the PDI molecules can coat the surface of the perovskite crystal to form the lattice cage through their conjugate skeletons, which passivates the trap states and improves the n-doping efficiency, as well as the stabilities of perovskites and related devices. With the addition of the 2D-PDI, the small-area solar cells achieved a PCE of 26.06% (25.44% certified) with a high VOC of 1.18V and a remarkable fill factor of 87.23%. Furthermore, the rigid and flexible perovskite solar modules yielded high PCEs of 21.48% and 20.71%, respectively. This dimensional regulation strategy provides useful guidance for effective n-type doping and high-performance p-i-n solar cells.

Study on the Preparation and Electrochemical Properties of LiFe0.4Mn0.6PO4 Coated with Bamboo Shaving-Based Carbon.

LiFe1-xMnxPO4 (0 < x < 1) has a high operating voltage range and theoretical energy density, but its actual capacity decreased due to its low electronic conductivity. To overcome this problem, we successfully prepared LiFe0.4Mn0.6PO4/C (LFMP/C) with a uniform carbon coating by a one-step solvothermal method using bamboo shavings as the carbon source. The results showed that heating at a reaction temperature of 180 °C for 18 h was the optimal synthesis condition to obtain LFMP/C. The addition of bamboo shaving-based carbon was effective in inhibiting excessive grain growth and reducing particle size. The disordered carbon layer enhanced the surface conductivity by connecting the surfaces of the particles. The synergistic effect of the nanoparticle size and the pores distributed around the particles increased the specific surface area and thus improved the contact area between the active substance and the electrolyte. Furthermore, there were improvements in electronic conductivity and ionic mobility. LFMP/C-16 showed initial discharge capacities of 150.1 and 143.5 mAh·g-1 at rates of 0.1 and 0.2C, respectively, with a capacity retention rate of 97.73% after 100 cycles, indicating excellent cyclic performance.

Research on Optimized Multi‐Objective FCS‐MPC Without Weighting Factors of NPC Three‐Level Inverter

ABSTRACTTo address a series of issues in the application of finite control set model predictive control (FCS‐MPC) strategy for neutral point clamped (NPC) three‐level inverters, such as large amount of rolling optimization calculation, poor midpoint voltage balance effect, high common mode voltage, and complex design of weighting coefficients, this paper proposes an optimized multi‐objective FCS‐MPC strategy without weighting factors. First, the method applies the idea of space vector region division, to obtain the optimal region based on Lyapunov function, and combines with delay compensation, reducing the system's optimization time and enhancing the control precision of the system. Second, aiming at the issue of multi‐objective control for inverters, by constructing the objective function to control tracking reference current, midpoint voltage balance, and reduce common mode voltage, a hierarchical optimization control method is adopted. This approach eliminates the need to design complex weighting coefficients constrained in the objective function as constraints, thereby improving the accuracy of predicted currents. Finally, the optimized multi‐objective FCS‐MPC control strategy is validated through simulation and experimentation to achieve a better balance of midpoint voltage and reduce common mode voltage and harmonic content, thereby enhancing the control precision and dynamic/static performance of the system.

A three-stage plasma model based on one-way coupling of plasma dynamics, ionic motion, and fluid flow: Application to DBD plasma actuators

The scope of this paper is to present a comprehensive approach for simulating low-temperature atmospheric dielectric barrier discharge plasmas. The proposed methodology categorizes the primary physical phenomena: (i) discharge dynamics, (ii) ionic motion, and (iii) fluid flow, according to their respective time scales and simulates each independently. This allows for the use of distinct solution procedures tailored to each of the three stages of the problem. Such separation offers significant flexibility in choosing appropriate models and numerical schemes for each stage, enabling the simulation of complex geometries and large-scale applications without the excessive computational costs associated with a monolithic approach. As a case study, we apply the proposed algorithm to the surface dielectric barrier discharge plasma actuator for flow control, which is powered by alternating high voltages. The algorithm successfully described the actuator’s behavior while maintaining low computational cost. Additionally, a parametric study is conducted to examine the effect of key input parameters on the generated electrohydrodynamic force and the resulting velocity. Finally, an overall assessment of the three-stage model is provided, highlighting its efficiency and accuracy.

Constructing Anion Solvation Microenvironment Toward Durable High-Voltage Sodium-Based Batteries.

Sodium-based rechargeable batteries are some of the most promising candidates for electric energy storage with abundant sodium reserves, particularly, sodium-based dual-ion batteries (SDIBs) perform advantages in high work voltage (≈5.0V), high-power density, and potentially low cost. However, irreversible electrolyte decomposition and co-intercalation of solvent molecules at the electrode interface under a high charge state are blocking their development. Herein, a high-salt concentration microenvironment is created and proposed by tailoring the solvation structures of charge carriers including both cations and anions, which maintains highly oxidation-resistant contact ion pairs and ion aggregates and provides a high ion conductivity. The tailored solvation structure makes a great contribution to protecting the graphite cathode from electrolyte oxidation, solvent co-intercalation, and structural degradation by constructing a robust cathode-electrolyte interphase with standout electrochemical stability. Based on this, the SDIBs achieved an excellent high-voltage cycling stability with 81% capacity retention after 10000 cycles and the battery showed an improved rate performance with 97.4 mAh g-1 maintained at 100C. It is identified that regulating anion solvation structure is responsible for the stable interface chemistry and enhanced reaction kinetics, which provides deep insight into the compatibility design between the electrolyte and specialized charge storage in electrodes.

Experimental Study on Efficient Short Electric Arc Turning of Titanium Alloy

This study investigates a novel short electric arc vertical turning method for machining titanium alloy shafts. The method was successfully applied to titanium alloy rods, and its effects on material removal rate (MRR), surface roughness, roundness, and cross-sectional morphology were analyzed at varying processing voltages. The results indicate that the MRR and surface quality improve with increased voltage, reaching a maximum of 231 mm3/min and 26 μm surface roughness at 32 V. However, surface roughness deteriorates with higher duty cycles and voltages due to unstable discharges. Roundness deviations are minimized with higher rotational speeds, which enhance uniform material removal and arc stability. Metallographic analysis revealed an increased heat-affected zone and recast layer thickness at higher voltages. This method demonstrates high machining efficiency and improved surface quality, making it suitable for titanium alloy shaft manufacturing in advanced engineering applications.

Grid-Forming: A Control Approach to Go Further Offshore?

Offshore wind farms are increasingly being commissioned farther from shore, and high voltage alternating current (HVAC) transmission systems are preferred because of their maturity and reliability. However, as cable length increases, ensuring system stability becomes more challenging, making it essential to investigate shunt reactor compensation configurations and converter control strategies. This study examines three different shunt reactor compensation arrangements and two control strategies, grid-forming (GFM) and grid-following (GFL), across three cable lengths (80 km, 120 km, and 150 km). The systems were evaluated based on small-signal stability using disk margins for different active power operating points, and later for different short-circuit ratios (SCR) and X/R. The results demonstrate that the GFM is preferable for longer cables and enhanced stability. The most robust configuration includes a shunt reactor placed in the mid-cable with additional reactors at both ends of the cable, followed by an arrangement with reactors at the beginning and end. The GFM converter control maintained stability across all operating points, cable lengths, and configurations, whereas the stability of the GFL unit was highly dependent on active power injection and struggled under weaker grid conditions. Thus, for longer HVAC cables, it is necessary to employ GFM control units, and it is recommended to use shunt reactors at the cable start and end, as well as at mid-cable, for optimal stability.

Low-cost single-source 17 level multilevel inverter with reduced switch count

Abstract This paper introduces an innovative multi-level inverter (MLI) topology operating with a single DC source. The proposed structure consists of a DC-DC rectifier (HFL), a switched capacitor (SC) unit and a Packaged U-Cell (PUC) module. The topology synthesizes 17 voltage levels at the output with only 10 power switches, offering low control complexity and high power efficiency. The high number of levels at the output voltage provides a high quality output voltage wave. A soft charging cell (SCC) is used to suppress impulsive charging currents in the switched capacitors. Experimental results show that SCC effectively suppresses impulsive currents in switched capacitors. The high frequency link (HFL) used to provide high voltage gain improves the cost efficiency of the system by reducing transformer sizes and costs. Simulation and experimental results show that the proposed topology achieves 96.92% efficiency, near sinusoidal current output and total harmonic distortion (THD) values between 4.99% and 1.23%. Moreover, with a low cost function (CF) value of 1.60, it is proven to offer a viable alternative for applications such as Renewable Energy Systems (RES) and Electric Vehicles (EVs). These findings demonstrate the applicability of the proposed MLI topology in these areas with low cost, high efficiency and quality power output.&amp;#xD;

The Effect of Sodium Dodecyl Sulphate Additives on the Electrochemical Performance of Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries are considered one of the most promising energy storage devices due to their high safety, low cost, and ease of fabrication. However, the growth of anode dendrites and continuous side reactions during cycling limit the practical application of zinc ion batteries. In this paper, sodium dodecyl sulfate (SDS) was used as an aqueous electrolyte additive to improve the surface deposition of Zn2+. The experimental results show that the SDS electrolyte additive forms a protective layer on the anode surface through electrostatic action and inhibits the growth of dendritic protruding dendrites by increasing the zinc deposition overpotential, as well as by limiting the two-dimensional diffusion of Zn2+ on the negative electrode surface of the aqueous zinc ion battery. As a result, adding SDS improves the discharge specific capacity of NVP/Zn batteries at high voltages and results in improved capacity retention. The cycling stability of NVP/Zn batteries was greatly enhanced by using a battery containing 1% SDS that still had a discharge specific capacity of 71 mAh/g after 100 cycles at a charging current density of 1 C, with a capacity retention rate of 89%. This work provides a simple and feasible solution to the anode problem of aqueous zinc ion batteries.

Tannic Acid Modulates Voltage-gated K+ Channels to Promote Neuritogenesis in Neuronal N2A Cells.

In a previous report, we showed that voltage-gated K+ (Kv) Kv1 and Kv2 channels are involved in cAMP-induced neuritogenesis of mouse neuronal N2A cells. In this report, we examined the effects of tannic acid (TA) on Kv channels and neuritogenesis in N2A cells. TA (15 μM) mildly enhanced Kv currents at -30 to -20 mV but strongly inhibited Kv currents at higher voltages, causing a preferential activation of currents at low voltages. When enhancement and suppression of Kv currents (at -20 and +70 mV, respectively) by different concentrations of TA were analyzed, TA at 4 μM produced strong enhancement at -20 mV with relatively mild suppression at + 70 mV. TA (4 μM) also promoted neuritogenesis; such promotion was suppressed by a Kv channel blocker tetraethylammonium ion, or a combination of hongotoxin-1 (blocker of Kv1.1), UK 78282 (blocker of Kv1.4) and guangxitoxin 1E (blocker of Kv2.1). Our results demonstrate, for the first time, TA at low concentrations could modulate Kv channels and thereby promote neuritogenesis.

Enhanced Efficiency and Stability in Blade-Coated Perovskite Solar Cells through Using 2,3,4,5,6-Pentafluorophenylethylammonium Halide Additives.

The power conversion efficiency (PCE) of perovskite solar cells is sensitive to their method of fabrication as well as the combination of materials in the perovskite layer. Air knife-assisted blade coating enables good quality perovskite films to be formed but the device efficiencies still tend to lag behind those fabricated using spin-coated perovskite layers. Herein we report the use of three 2,3,4,5,6-pentafluorophenylethylammonium halides (FEAX, where X = I-, Br- or Cl-) as additives in nitrogen knife-assisted blade-coated methylammonium lead iodide (MAPbI3) perovskite solar cells. The additives were all found to passivate defects in the MAPbI3 films. The use of chloride as the counteranion led to additive containing films with the largest crystal size and fewest defects and consequently the FEACl film was found to have the highest photoluminescence (PL) intensity, longest average PL lifetime and lowest trap density. These features led to the devices having a high open-circuit voltage (Voc) of 1.17 V and a PCE of 21.4%. In addition, the hydrophobic fluorinated cations led to the additive containing devices being more stable, with those containing FEACl having the best thermal stability and performance under maximum-power-point (MPP) tracking in a humid (≈65%) environment at 50 ± 1 °C.

Preliminary considerations and challenges of proton-boron fusion energy extraction on the EHL-2 spherical torus

Abstract EHL-2 spherical torus (ST) is one of the key steps of p-11B (proton-boron or hydrogen-boron) fusion energy research in ENN. The fusion produced energy is carried mainly by alpha particles of average energy 3 MeV, which ideally can be converted to electricity with high efficiency (&gt; 80%). However, there exist serious difficulties to realize such conversion in a fusion device, due to the high energy density and high voltage required. To comprehensively describe the progress of the EHL-2 physics design, this work presents preliminary considerations of approaches for achieving energy conversion, highlighting critical issues for further investigation. Specifically, we provide an initial simulation of alpha particle extraction in the EHL-2 ST configuration as a starting point for p-11B fusion energy conversion.

Effect of Changes in Mains Voltage on the Operation of the Low-Power Pellet Boiler

Modern low-power boilers with automatic burners require electricity for proper operation. The electricity voltage in the network is not constant and is subject to fluctuations. Variations in voltage will have the most significant impact on the operation of electric motors since their speed is controlled by changing the voltage. The purpose of this research was to assess the impact of supply voltage deviations within the range allowed by the EN 60038:2012 standard (230 V ±10%, i.e., 207 V and 253 V) on boiler operation. This study analysed the effects of these variations on flue gas and dust emissions during boiler operation at full load, as well as on the boiler firing process. Tests were conducted on a boiler with a nominal output of 25 kW. Changes in voltage significantly influenced the blower fan speed. For the nominal boiler output, at 253 V the speed increased by 17.6%, and at 207 V it decreased by 20.4%. Variations in voltage affected the volume of air supplied to the combustion chamber, altering the excess air ratio (λ): 1.8 at 230 V, 2.1 at a higher voltage, and 1.4 at a lower voltage. Changes in voltage translated into changes in exhaust gas temperature and flue gas and dust emissions. Boiler operation at 253 V increased CO emissions by 77.2%, NOx by 31.2%, and dust by 12.5%. In contrast, at 207 V, emissions were lower, with CO decreasing by 17.3%, NOx by 11.7%, and dust by 18.8%. Fluctuations in voltage further influenced the boiler’s ignition time; the ignition process was four times longer at a higher voltage and twice as long at a lower voltage. The results of these studies underscore the necessity of adapting boiler designs to fluctuating voltage conditions.

Highly bright perovskite light-emitting diodes enabled by retarded Auger recombination

One of the key advantages of perovskite light-emitting diodes (PeLEDs) is their potential to achieve high performance at much higher current densities compared to conventional solution-processed emitters. However, state-of-the-art PeLEDs have not yet reached this potential, often suffering from severe current-efficiency roll-off under intensive electrical excitations. Here, we demonstrate bright PeLEDs, with a peak radiance of 2409 W sr−1 m−2 and negligible current-efficiency roll-off, maintaining high external quantum efficiency over 20% even at current densities as high as 2270 mA cm−2. This significant improvement is achieved through the incorporation of electron-withdrawing trifluoroacetate anions into three-dimensional perovskite emitters, resulting in retarded Auger recombination due to a decoupled electron-hole wavefunction. Trifluoroacetate anions can additionally alter the crystallization dynamics and inhibit halide migration, facilitating charge injection balance and improving the tolerance of perovskites under high voltages. Our findings shed light on a promising future for perovskite emitters in high-power light-emitting applications, including laser diodes.

Enhanced COVID-19 Optimization Algorithm for Solving Multi-Objective Optimal Power Flow Problems with Uncertain Renewable Energy Sources: A Case Study of the Iraqi High-Voltage Grid

The optimal power flow (OPF) problem is a critical component in the design and operation of power transmission systems. Various optimization algorithms have been developed to address this issue. This paper expands the use of the coronavirus disease optimization algorithm (COVIDOA) to solve a multi-objective OPF problem (MO-OPF), incorporating renewable energy sources as distributed generation (DG) across multiple scenarios. The main objective is to minimize fuel costs, emissions, voltage deviations, and power losses. Due to its non-convex nature and computational complexity, OPF poses significant challenges. While COVIDOA has been utilized to solve engineering problems, it faces difficulties with non-linear and non-convex issues. This paper introduces an enhanced version, the enhanced COVID-19 optimization algorithm (ENHCOVIDOA), designed to improve the performance of the original method. The effectiveness of the proposed algorithm is validated through testing on IEEE 30-bus, 57-bus, and 118-bus systems, as well as a real-world 28-bus system representing Iraq’s standard Iraq super grid high voltage (SISGHV 28-bus). The two-point estimation method (TPEM) is also applied to manage uncertainties in renewable energy sources in some cases, leading to cost reductions and annual savings of ($70,909.344, $817,676.64, and $5,608,782.144) for the IEEE 30-bus, 57-bus, and reality 28-bus systems, respectively. Thirteen different cases were analyzed, and the results demonstrate that ENHCOVIDOA is notably more efficient and effective than other optimization algorithms in the literature.

Ternary NASICON-Type Na3.25VMn0.25Fe0.75(PO4)3/NC@CNTs Cathode with Reversible Multielectron Reaction and Long Life for Na-Ion Batteries.

Na superionic conductor (NASICON)-structure Na4MnV(PO4)3 (NVMP) electrode materials reveal highly attractive application prospects due to ultrahigh energy density originating from two-electron reactions. Nevertheless, NVMP also encounters challenges with its poor electronic conductivity, Mn dissolution, and Jahn-Teller distortion. To address this issue, utilizing N-doped carbon layers and carbon nanotubes (CNTs) for dual encapsulation enhances the material's electronic conductivity, creating an effective electron transport network that promotes the rapid diffusion and storage of Na+. On this basis, partially substituting Mn in NVMP with Fe, a new sodium superionic conductor (NASICON) structured cathode material has been designed to alleviate Jahn-Teller distortion and prolong the cycling life. The synergistic effect of N-doped double nanocarbon encapsulation and multielectron reactions is employed to promote the optimized Na3.25VMn0.25Fe0.75(PO4)3/NC@CNTs (NVMn0.25Fe0.75P/NC@CNTs) electrode material to deliver fast Na+ diffusion kinetics, high reversible capacity (110.2 mAh g-1 at 0.1 C), and long-term cyclic stability (80.1% of the capacity at 10 C over 2000 cycles). Besides, the electrochemical properties of NVMn0.25Fe0.75P/NC@CNTs composites were investigated in detail at high loads and high window voltages to evaluate their potential for practical applications. The reduction/oxidation processes involved in Fe2+/Fe3+, Mn2+/Mn3+, and V3+/V4+ redox couples and a solid-solution and biphasic reaction mechanism upon repeated de- and re-intercalation processes are revealed via ex-situ XRD and XPS characterization. Finally, the assembled NVMn0.25Fe0.75P/NC@CNTs ∥ hard carbon full cell manifests high capacity (101.1 mAh g-1 at 0.1 C) and good cycling stability (98.2% capacity retention at 1 C after 100 cycles). The rational design with multimetal ion substitution regulation has the potential to open up new possibilities for high-performance sodium-ion batteries.

Mechanically Resilient and Highly Efficient Flexible Perovskite Solar Cells with Octylammonium Acetate for Surface Adhesion and Stress Relief.

Flexible perovskite solar cells (FPSCs) have advanced significantly because of their excellent power-per-weight performance and affordable manufacturing costs. The unsatisfactory efficiency and mechanical stability of FPSCs are bottleneck challenges that limit their application. Here, we explore the use of octylammonium acetate (OAAc) with a long, intrinsic, flexible molecular chain on perovskite films for surface adhesion and mechanical releasing. The results showed that OAAc with high structural flexibility and strong molecular interactions can act as a mechanical release layer in releasing residual tensile stress, confirmed by the film and device characterizations as well as finite-element simulation. Moreover, the passivation of the OAAc could increase the formation energy of defects including I vacancy, Pb vacancy, and Pb-I antisite. The experimental results showed that the trap states of perovskites were significantly suppressed after OAAc modification, which is beneficial to the construction of high-quality films. With a high open-circuit voltage of 1.196 V, the efficiency of the OAAc-treated devices increased from 23.14% to 25.47% on a rigid substrate (23.12% on a flexible substrate), yielding superior long-term and mechanical durability. The corresponding flexible device retains 74% of the initial value even after 8000 bending cycles at a bending radius of 5 mm.