Withstand Voltage Research Articles

Preparation of highly condensed porous carbon used in EDLCs with high voltage and high volumetric energy density

Conventional porous carbons as the electrode material for electric double layer capacitors (EDLCs) normally have low volumetric energy density due to the low density and poor withstanding voltage characteristic. Therefore, it is very meaningful to construct porous carbon with high density and high voltage resistance. In this paper, using sulfonated pitch and graphene oxide as precursors, highly condensed porous carbon (SGx) with improved withstanding voltage characteristic is prepared by the π-π conjugated interaction and simple chemical activation with secondary high temperature treatment. The prepared porous carbon material with 3 wt% graphene oxide (SG3%) well-balances the specific surface area (SSA) and packing density, exhibiting high SSA of 2700 m2 g−1 and high packing density of 0.53 g cm−3. Besides, low oxygen content (9.82 at.% of surface O atoms) and stable surface chemical composition (ether bonds dominating) avoid the side reactions between the oxygen-containing functional groups and electrolyte, thus improving the withstanding voltage characteristics. At 3.2 V voltage in TEABF4/PC electrolyte, Cv and the maximum energy density reach 80.6 F cm−3 (1 A g−1) and 31.1 Wh L−1, respectively. Almost no capacity fading is found after 20,000 cycles testing. This work provides a new strategy for the development of high withstanding voltage EDLCs.

Research on Traveling Wave Detection Performance Based on Optical Voltage Transformer

Traditional transformers cannot effectively transmit high-frequency traveling wave signals, which leads to the fact that traditional voltage transformers cannot fully reflect the panoramic information of fault traveling waves and ensure fault location accuracy. This paper mainly analyzes the working principle of optical voltage transformers. The Jones matrix models the optical path system and its optical components, and the output model of the optical path system is obtained. The principle of photoelectric signal conversion is analyzed. The test principle, experimental method, and data results are studied and analyzed by power frequency, withstand voltage, lightning impulse, and arc tests. The transmission effect of fault traveling wave signal is verified, which provides the theoretical and experimental basis for the fault location of the distribution network.

Study on Directivity of Underwater Circular Transducer Array

At present, in the detection and identification of underwater noise sources, one of the most commonly used transducer arrays is the circumferential transducer array. The circumferential transducer array is symmetrical in space and has high withstand voltage capability and small sound pressure fluctuation in the horizontal beam. Its directivity is an important index that affects the performance of the array. This paper focuses on the directivity maps of circular arrays with different sizes and numbers of elements. From the graph, it is concluded that the undulation of the directivity graph of the circular array is directly related to the array element spacing. The smaller the array element spacing is, the smaller the undulation is, and vice versa. The directivity formula and law can provide technical guidance for the design of a uniform circular transducer array.

A Novel Word Line Driver Circuit for Compute-in-Memory Based on the Floating Gate Devices

In floating gate compute-in-memory (CIM) chips, due to the gate equivalent capacitance of the large-scale array and the parasitic capacitance of the long-distance transmission wire, it is difficult to balance the switching speed and area of the word line driver circuit (WLDC). The difference among multiple voltage domains required for floating gate CIM devices has also far exceeded the withstand voltage range of a single transistor in the WLDC. This paper proposes a novel WLDC based on the working principle of the CIM array. A multi-level pre-processing voltage control method is adopted to carry out an optional hierarchical transmission of multiple high voltages, significantly reducing the propagation delay. The proposed WLDC is based on the Wilson current mirror structure, which substantially reduces the physical design area. The simulation results show that the circuit can convert a 1.2 V low-voltage domain input signal with a frequency of 10 MHz into a high-voltage domain output voltage, and the output voltage range of a single WLDC can reach −10 V to 10 V. With a capacitive load within 5 pF, the transmission delay is less than 10 ns. The layout area is 594.88 µm2, which is suitable for a large-scale CIM array.

Research on characteristics of large-capacity metal-oxide surge arrester at long-duration current impulse for HVDC converter stations

Arrester is the basis for the insulation coordination. Depending on the installation location of Metal-oxide Surge arrester for HVDC converter stations, there are significant differences in the rated voltage, energy absorption capacity of an arrester. In addition to limiting lightning and switching overvoltage in system, huge energy is also absorted by arresters for HVDC converter stations. DC transfer switch arrester and neutral bus arrester are a kind of typical large-capacity arresters. The energy absorption of large-capacity arrester is much greater and the failure probability of large-capacity arresters is also greater than others for HVDC converter stations. Some experiments of long-duration current impulse were carried out by selfdeveloped test devicer. The voltage and energy withstand of long-duration current impulse versus time characteristic were studied and empirical formula was fitted. The test results show that voltage and energy withstand of long-duration current impulse are going down with the increase of duration. The insufficient energy absorption capacity is the reason for the frequent failure of large-capacity arresters. These conclusions can be used as a reference for the design of arresters for HVDC converter stations.

Optimization design of multi-layer metal box-type pre-insertion resistance for VSCUHVDC

In a ±800kV VSC-UHVDC transmission project, due to the uneven voltage distribution of multi-layer metal box-type preinsertion resistance, several breakdown and flashover faults occurred in type and debugging tests. The paper studies the overvoltage characteristic of two types of multi-layer metal box-type resistances. Firstly, for A-type pre-insertion resistance, the voltage distribution without stray capacitance is preliminarily analyzed based on PSCAD. The preliminary analysis shows that the recommended voltage non-uniformity coefficient for VSC-UHVDC pre-insertion resistance is 1.3, and the optimization method for A-type is proposed. Then, the difference of B-type is analyzed on the basis of the research on A-type. The electrostatic field solver is used to calculate B-type stray capacitance, and the PSCAD circuit model with stray capacitance is built. The uneven voltage distribution is obtained by simulation calculations and experiments. The results show that the terminal voltage of resistance unit is significantly higher than the average voltage, and withstand voltage reference values of the mica rod and the wall bushing are also calculated. Based on practical engineering problems, this paper combines theoretical calculations with simulations and experiments. The research results can provide some research directions and data references for the insulation optimization design of VSC-UHVDC pre-insertion resistance.

Lifetime Analysis of Mica Paper Capacitors Under Microsecond Pulse

In recent years, the development of mica paper capacitor (MPC) technology has dramatically improved the withstand voltage and energy storage density of capacitors, which is suitable for pulse power systems. The lifetime of capacitors is a key factor that ensures the reliability of a system. In this article, the investigation of the lifetime characteristics of MPCs under microsecond pulse is presented. The structure of an MPC is analysed, and two numerical simulations are performed to study its characteristics. A lifetime test platform is established to test MPCs, which has stable operation performance. Essential electrical degradation parameters of MPCs are obtained and analyzed. The operational factors that influence the lifetime of MPCs are analysed, and a lifetime empirical model under given operational factors is proposed based on the lifetime test results. The results suggest that the lifetime empirical model could match well with lifetime test results. Furthermore, the structure of a pulse forming network (PFN)-Marx is analyzed by the lifetime model, and constructive suggestions are proposed. This article is devoted to studying the characteristics of MPCs and analyzing the lifetime under various operational factors, which finally helps the device to specify operating conditions and ensure reliability.

High-Power Microwave Limiters Using Recess-Free AlGaN/GaN Schottky Barrier Diodes

In this letter, a thin-barrier AlGaN/GaN Schottky barrier diode (SBD) is proposed and implemented in a three-stage high-power RF limiter module. Benefited from the thin-barrier epitaxy, a recess-free process in the Schottky region is allowed to avoid the plasma damage, resulting in low ON-resistance of 5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> and high withstand voltage characteristics. In addition, the proposed SBDs have achieved a low junction capacitance of 0.35 pF at 0 V bias and a turn-on voltage of 0.5 V. With the optimized SBD and well-designed matching circuits, the limiter has reached a high power capacity of over 10 W in continuous wave (CW), 20 W in pulse mode, and a fast recovery time of 30 ns at a frequency of 3.5 GHz, exhibiting better characteristics than traditional limiters. Both simulation and measured results agree with each other. It indicates that the AlGaN/GaN-based SBD is promising for high-power and high-frequency limiters.

AC/DC Side Split Capacitor Power Decoupling Circuit

Single-phase inverters have a wide range of applications in many fields, but there are inherent double frequency problems, and double frequency fluctuations can easily cause system instability. This paper proposes a mid-point common-mode injection power decoupling circuit. The advantage of this topology is that there are no additional switching devices and only the original DC side support capacitors and filter capacitors of the H-bridge inverter can be used to buffer the double frequency power. The half-bridge structure of this topology enables the AC side capacitors to operate positively and negatively, which can reduce the selection of the withstand voltage of the decoupling capacitor. Simulation and experimental results prove that the method can effectively suppress the secondary ripple on the DC side. The final data shows that the topology can effectively improve the system efficiency after decoupling.

The regulation of the withstand voltage performance of ZnO/GaN vertical heterostructures using external electric field and vacancy defects

The band gap of the heterostructure determines the withstand voltage. It is very important to regulate the band gap of heterojunctions and to investigate their electrical properties by applying external electric field. Based on density functional theory (DFT), ZnO/GaN vertical heterostructures with two stacking configurations (AB/BA and AB/AB, named H1 and H2, respectively) are constructed. The external electric field and vacancy defects of Zn, Ga, O and N atoms (VZn, VGa, VO and VN) are applied to analyze the electrical properties. The band gap can be tuned from 2.07 eV to 0 eV in H1 and 1.53 eV–0 eV in H2. As the electric field increases, H1 has stronger withstand voltage (−0.84–0.56 V/Å) than H2 (−0.26–0.26 V/Å). In addition, the structures deform obviously with the effect of vacancy defects, but remain stable. The presence of VGa and VN enables H1 and H2 to exhibits metal conductivity and VO change the band types of H1 and H2 from direct to indirect. The results of charge density difference (CDD) prove that a zero potential region and a weak electric field occur at the position of VZn and VO, respectively. Likewise, the external electric field is applied to the defective heterostructures. The bandgap also exhibits strong tunability, and the heterostructure with VO has the largest electric field modulation width. The above results indicate that ZnO/GaN exhibits excellent electrical properties with the influence of VO, which represents potential applications in electronic devices.

A novel high‐efficient step‐up converter with continuous input current, common ground, and minimum stress on semiconductors

AbstractThis study proposes a comprehensive analysis of a novel non‐isolated step‐up converter with continuous input current and common ground. The proposed topology provides high voltage gain besides insignificant voltage and current stress across switches and diodes. Consequently, using switches and diodes with low current and voltage withstanding is achievable, leading to high converter efficiency and cost reduction. The voltage and current stress besides steady‐state and efficiency analysis are surveyed. Moreover, the converter's non‐ideal voltage gain analysis employing different components is discussed and compared with recently suggested converters. Additionally, the component losses, efficiency, normalized voltage, and current stresses of the studied converters are collected in tables to simplify the comparison between different topologies. Finally, a 100 W prototype converter is implemented to confirm theoretical performance, and the results are investigated in detail.

A double-break current injection vacuum DCCB: Principle and analysis

To improve the breaking performances of current injection vacuum DC circuit breaker (DCCB), a double-break current injection DCCB proposed. The opening moments of the two breaks are not simultaneously, one of the breaks is arc breaking, which is used for cut off the fault current, and the other is non-arc breaking, which is used to enhance the transient recovery voltage (TRV) withstand capability. During the interruption process, let the arc-breaking contact first open, the contact starts to separate and produce arcs, then the pre-charged capacitor injects a reverse current to extinguish the arc, meanwhile, the current commutation of non-arc-breaking contact is realized by a coupling inductor. In addition, freewheeling diodes connected in parallel at the contacts to delay the occurrence of transient recovery voltage, thereby further increasing the voltage withstand capability of the CB. The principle and analysis of proposed DCCB scheme are discussed. Finally, the effectiveness of the proposed DCCB scheme is verified by simulation

Electrochemical Properties of Aqueous Electric Double Layer Capacitors using Sodium Polyacrylate

Electric double layer capacitors (EDLCs) are attracting attention as a type of storage battery with high-speed charge-discharge and long life. However, the withstand voltage of the aqueous electrolyte is approximately 1.2 V, which is the voltage at which electrolysis of water occurs, and there is a problem that it lacks energy density. In this study, sodium polyacrylate was added to the electrolyte to gelatinize it and prevent electrolysis of water, thereby improving the withstand voltage up to 3.5 V and obtained energy density of 4.6 Wh/kg.

Analysis of AC breakdown strength of vegetable oils and effect of mineral oil

• AC breakdown strength of coconut oil is studied as against commercial soybean oil. • Analyzed the effect of aging (120 °C, 2 weeks) and mineral oil on AC breakdown strength. • AC breakdown data are statistically analyzed using Normal and Weibull distributions. • Aging or mineral oil reduces the withstand voltage, but the effect is less intense in coconut oil. • Coconut oil can be a potential replacement for traditional mineral oils. The effect of residual mineral oil on the AC breakdown strength of vegetable oil is widely studied to understand vegetable oil's reliability and dielectric integrity in retro-fitting a mineral oil-filled transformer. This paper describes the analysis of experimental results on two types of vegetable oil, namely –refined, bleached, and deodorized (RBD) coconut oil and commercial vegetable oil (MIDEL eN1215) derived from soybean oil seeds. The latter is also to act as a benchmark in analyzing the breakdown performance of RBD coconut oil, which is recently studied as a potential alternative to replace mineral oil from transformers located in tropical countries. The AC breakdown voltage tests were conducted using ASTM D1816 method at normal ambient conditions for both fresh and aged oils and considering 10 and 30% mineral oil in these vegetable oils. It is found that the distributions of breakdown voltages in RBD coconut oil, especially the lowest AC breakdown voltage, are similar to those of commercial vegetable oil for transformers. Therefore, from the viewpoint of AC withstand voltage, RBD coconut oil is equivalent to commercial vegetable oil under new conditions and even better under aged conditions or when mixed with mineral oil.

パワーモジュールの絶縁基板における三重点の電界強度と絶縁破壊電圧に関する研究

Silicon carbide (SiC) devices exhibit several advantages such as high withstand voltage, high temperature operation, and low losses compared to conventional Si devices. However, in order to take full advantage of SiC devices, it is necessary to improve the characteristics of the power module package. In particular, the electrical insulation properties of the package depend on the insulating substrates. In this study, we focused on the difference in the electric field strength distribution when the front and back copper foils are moved horizontally relative to the aluminum nitride substrate.

Electrical and Mechanical Properties Research of Key Winding Materials in Dry Type Air-core Reactors at Low Temperature

The low-temperature environment affects the physical properties of various materials in dry type air-core reactors, which affects the performance of the whole reactor. Therefore, when the reactor is put into operation, the insulating properties or mechanical properties of the reactor will not meet the requirements for normal operation, thus creating local defects and causing major accidents. In this paper, the insulating properties and mechanical properties of epoxy transposed wire and winding insulation are studied through AC withstand voltage tests and tensile tests under different low-temperature environments. Analysis of the test results shows that the low temperature has no significant effect on the electrical insulating properties of key materials in the reactor, but weakens the mechanical properties such as tensile strength.

Design of the GaN based CAVET with SiO2–InGaN hybrid current blocking layer

The emergence of vertical GaN devices solves the problem of insufficient voltage withstand capacity of horizontal GaN devices. However, the current output capability of vertical GaN devices is not comparable to that of lateral GaN devices. So we propose a Al0.3Ga0.7N/GaN current-aperture vertical electron transistor with a SiO2–In0.05Ga0.95N hybrid current-blocking layer (CBL). Through simulation and in-depth study of the proposed device, the results show that the GaN/InGaN secondary channel enhances the saturation output current of the device, achieving a saturated output current (I DSS) of 985 mA mm−1 and a transconductance (G m) of 256 mS mm−1, which are 30% and 25% higher than that of the single-channel SiO2 CBL device, respectively. The breakdown voltage is 230 V and the on-resistance (R on) is only 0.58 mΩ cm2.

Microwave Plasma Assisted Aerosol Deposition (μ-PAD) for Ceramic Coating Applications

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or more) deposition. However, there are problems associated with the phase transition of the coating film and poor film quality due to formation of voids. To solve these problems, the aerosol deposition (AD) method has been developed. This method provides nice ceramic film quality. However, the coating rate is quite slow and has difficulty producing thick films (&gt;30 µm). To overcome these limitations, microwave plasma-assisted aerosol deposition (μ-PAD) is applied at low vacuum conditions without the AD nozzle. This method uses a microwave plasma source during the AD process. After enduring a long-term durability test, as a trial run, μ-PAD has been applied on the actual process site. With the Al2O3 powder, μ-PAD shows a coating rate that is 12 times higher than the AD method. In addition, the formation of a thicker film (96 µm) deposition has been demonstrated. On the other hand, the coating film hardness, porosity, adhesion, and withstand voltage characteristics were confirmed to be less than the AD method.

Research and application of high voltage measurement technology in DC UHV preventive test

With the state’s high attention to clean energy and the requirement to reduce the loss of power grid transmission lines, DC UHV has developed rapidly in recent years. It refers to DC transmission and related technologies with voltage levels of ±800 kV (±750 kV) and above. In the power system, DC high-voltage transmission is inseparable from power equipment, but the higher the transmission voltage level, the higher the voltage of DC withstand voltage preventive test. Before the transmission of UHV DC transmission lines, if the DC voltage withstand device is 800 kV or above, the voltage withstand test shall not be carried out for the high-voltage line. The traditional direct comparison method using voltage divider cannot be used to measure the DC output voltage of DC UHV withstand voltage device on site. This paper analyzes the method of full coverage of DC UHV system in limited voltage range and the method of out of range calibration using scale factor. In order to solve the problem of voltage traceability in the DC high voltage generator, especially the voltage traceability of the field DC UHV device, when the voltage output range of the calibrated DC high voltage generator exceeds the measurement range of the standard, the standard value of the voltage calibration point beyond the range can be determined by comparison and obtained through the linearity test. The comparison with the standard shall be conducted at a voltage not lower than 20% of the rated voltage of the calibrated DC high voltage generator, and compared to the maximum voltage of the standard voltage divider. The comparison is carried out at a (a ≥ 2) voltage point. When comparing at a point, the highest voltage level is equal to the upper limit of the standard. Under a voltage point, according to the mathematical relationship between the voltage standard value of the tested device and the current flowing through the linear load resistance, the fitting function can be obtained through the linear regression method. For b (b ≥ 4) calibration points beyond the measurement range of DC standard voltage divider, the standard value can be “extrapolated” from the linear load resistance current and the fitting function Yang (2002). Through comparison and verification, the method is feasible, which is of great significance to promote the compilation of calibration specification for DC high voltage generator.

Self-Powered Gate Drive Circuits With Optical Signal Isolation for In-Vehicle Marx Circuit of Ozonizer

Reducing the cost of a Marx circuit as a high-voltage power supply for nitrogen oxide (NOx) decomposition for diesel vehicles is required. The Marx circuit with MOSFETs has an advantage in size compared to the Marx circuit with gap switches. However, the Marx circuit with MOSFETs needs gate drive circuits on the gate of each MOSFET. The gate signal and drive power must be supplied to each gate with isolation in a low-cost way. However, the transformer for the isolation with high withstand voltage, such as 10 kV or more, is typically high cost because of the low demand. This article proposes the self-powered gate drive circuit using the charging path of the Marx circuit. The proposed gate drive circuit only requires a low withstand voltage because the power for the MOSFET on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> th stage is supplied from the ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n -1$ </tex-math></inline-formula> )th stage via a low-voltage transformer. Besides, the gate signal is transmitted through pairs of LEDs and photodiodes instead of high-cost optical fibers. The proposed gate drive circuits are developed and implemented into a prototype of the Marx circuit with an output voltage of 4 kV. From the experiments, it is demonstrated that the proposed drive circuits provide both drive power and gate signal.