Current-limiting Effect Research Articles

Enhancing low voltage ride-through capability of grid-connected photovoltaic plants using superconducting fault current limiters

Photovoltaic (PV) plants are playing an increasingly important role in the power system, and research focuses on their reliability and security have notably grown in recent years. To ensure the stable operation of PV plants, the low voltage ride-through (LVRT) strategy is attracting lots of academic and industrial interest. This is because the LVRT can prevent PV plants from being immediately disconnected during grid faults, which helps avoid slower recovery and extended power outages. Hence, this work proposes to enhance the LVRT capability of the PV plant using superconducting fault current limiters (SFCLs). Besides, the impacts of various types of SFCLs on the LVRT characteristics of the PV plant are thoroughly analyzed. Moreover, this work investigates the performance of various types of SFCLs in enhancing the LVRT capability of PV plants and achieving current-limiting effects, providing valuable insights for the design of SFCLs. A model of a real 35 kV grid-connected PV plant with SFCLs is built, and the theoretical analysis is validated. The results demonstrate the feasibility and superiority of using SFCL in enhancing the LVRT capability of PV plants, serving as a reference for the application of SFCLs in renewable energy stations.

Nucleation bubble boundary layer theory for ultra-fast electrochemical polishing of additive manufacturing components

The application of electrochemical-based polishing techniques, including electrochemical polishing (ECP) and plasma electrolytic polishing (PEP), to improve the surface quality of additive manufacturing (AM) components is challenged by the high amplitudes and long spatial wavelengths of roughness, which cause pre-polishing procedures to be indispensable. In this study, a nucleation bubble boundary layer (NBBL) mechanism for enhanced electrochemical-based polishing performance is revealed to solve this problem, namely nucleation bubble electrochemical polishing (NBEP). The NBBL is constructed on the anode surface via electrolytic oxygen evolution and nucleate boiling, and is activated by regulating the temperature and electric potential. The experiments verify a model of NBBL consisting of an inner adherent layer and outer diffusion layer (ODL). Simulations and experiments demonstrate that the polishing mechanism is based on the combined current-limiting effect of individual adherent bubbles and the ODL, which differentiates the anodic dissolution rates at the peaks and valleys of a wide range of spatial wavelengths with their electrical resistance. The bubble dynamics also enhance mass transfer, further improving the polishing efficiency. The experimental results show that NBEP is capable of reducing the surface roughness of AM stainless steel 316 L from Ra of 10.22 μm to 0.71 μm, and eliminating the spatial wavelengths of 200–400 μm in 8 min, which cannot be achieved by either ECP or PEP. The polishing current density also increased from 0.25 (ECP) and 0.48 (PEP) to 2 A/cm2 in NBEP. Finally, a prediction model that accurately describes the ultimate roughness achieved by NBEP as a function of the minimum cavity size is established. The NBEP can be directly followed by PEP or ECP to achieve an optimal surface finish of Ra <70 nm for AM parts. The NBEP method considerably enhances the polishing performance of electrochemical-based systems for AM components, as well as expands the application range of electrochemical-based polishing techniques.

A novel hybrid magnetic material based on three-phase saturated core fault current limiter

Installing a three-phase saturated core fault current limiter (TSFCL) is an effective method to limit the increasing short-circuit current in high-voltage alternating current (HVAC) systems. However, the traditional TSFCL uses silicon steels as its working material for the iron core, resulting in poor current-limiting effects, requiring a large DC excitation current, and having a slow response speed. Nanocrystalline alloys have advantages such as a lower saturation point, higher permeability in the unsaturated zone, and a steep B–H curve, making them highly suitable for TSFCL’s applications. However, their poor capability which withstands fault hindered their large-scale commercialization. Therefore, this paper proposes a novel hybrid magnetic material based on TSFCL (HMTFCL), where the materials of the working limbs are replaced by nanocrystalline alloys. Compared to TSFCL, the DC excitation current of HMTFCL decreases by 60.5%. And, the HMTFCL reduces the peak short-circuit current by 23%. Last, the magnetic flux intensity inside the working limb of HMTFCL is reduced to zero more quickly.

Microplasma Breakdown in GaAs‐Based Avalanche S‐Diodes Doped with Deep Fe Acceptors

The article reports investigations into the microplasma breakdown in GaAs‐based avalanche S‐diodes doped with deep Fe acceptor impurities. The experiment shows the effect of current limitation in a reverse I–V curve with “soft” avalanche breakdown. It proposes 2D single microplasma models and calculates I–V curves of diodes with a deep impurity during microplasma breakdown. By comparing experimental and calculation data, authors propose an explanation for the effect of current limitation during avalanche breakdown. The effect is associated with capture of avalanche holes at negatively charged Fe centers, which enhances the depletion region and minimizes the maximum electric field in a reverse‐biased p–n junction of an S‐diode.

Fault Transient Study of a Meshed DC Grid With High-Temperature Superconducting DC Cables

This paper presents the DC fault transient study of a meshed DC grid with high-temperature superconducting (HTS) HVDC cables to integrate offshore wind power. A four-terminal meshed DC grid model with a ±100 kV DC voltage rating is developed. DC circuit breakers (DCCBs) are implemented in the DC grid to deal with DC cable faults. To conduct the fault transient study, the fault scenarios with different fault locations and protection delays are studied. The sensitivity study versus different DC fault locations reveals that the faults on the faulted cable will not cause the quenching of healthy cables. The sensitivity study considering different DC fault protection delays demonstrates that the HTS cables have a current-limiting effect and the long delay of DC fault protection does not result in large fault current and the quenching of healthy cables. Extensive simulations in PSCAD/EMTDC validate the founding.

Research on a Secondary Active Limiting DC Fault Current Limiter Topology

The current-limiting performance of the smoothing reactor is weak. The traditional saturated core-type fault current limiter (TFCL) is better, but will cause the dc circuit breaker (DCCB) to endure high overvoltage, energy absorption and also increase the current fall time. When DCCB recloses on the permanent fault, the whole dc system will face a harmful second shock that cannot be solved effectively by TFCL. To solve the above problems, a secondary active limiting fault current limiter (SAFCL) topology is proposed. It can reduce the DCCB overvoltage and energy absorption greatly. Meanwhile, it can store fault energy and uses it to active limit the current when the DCCB recloses on the permanent fault. The secondary active current limiting effect is better than the first and the DCCB breaking electric stress is lower than the first. First of all, the topology and principle of the SAFCL are introduced. The main electromagnet parameters are then analyzed. The performance of different FCLs are simulated comparatively to verify the superiority of the SAFCL. Final, the experiment is carried out, the comparison with simulations verifies the feasibility of the SAFCL.

Progress on Second-Generation High-Temperature Superconductor Tape Targeting Resistive Fault Current Limiter Application

The resistive superconducting fault current limiter is well known for its simple structure and outstanding current-limiting effect, and it is broadly applied in power grid systems. The second-generation high-temperature superconductor (HTS) tape, of higher structural strength and greater room-temperature resistance, is well suited for application in resistive superconducting fault current limiters. The quenching caused by overcurrent in the HTS tape is a complexed coupling effect of several physical factors. The tape structure and properties directly impact the ultimate HTS tape’s quench performance. In this study, various SS316-laminated HTS tapes, of different critical currents, room-temperature resistances, and masses, were prepared. The pulse impact parameters of the various tape samples were measured using the RLC high-current impact test platform. By analyzing the resultant data, a quantitative assessment methodology to measure a tape’s tolerance toward impact was developed. The dependence of the HTS tape’s tolerance toward impact on its critical current, room-temperature resistance, and mass was studied. This provides numerical guidance on HTS material selection for resistive superconducting fault current limiters.

Placement optimization of Multi-Type fault current limiters based on genetic algorithm

The fault current limiter (FCL) is an effective measure for improving system stability and suppressing short-circuit fault current. Because of space and economic costs, the optimum placement of FCLs is vital in industrial applications. In this study, two objectives with the same dimensional measurement unit, namely, the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents, are considered. The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life. The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem. The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm (GA) method. Comparative and sensitivity analyses are performed. The results of the optimized plan are validated through simulations, indicating the significant potential of the GA for such optimization.

Design and Test Analysis of Small-Scale Direct Current Superconducting Current-Limiting Switch Prototype

Medium voltage direct current (MVDC) shipboard power system (SPS) is the development trend of future ships. With the characteristics of compact structure and high-power density, the short circuit is much more serious than land-based power system, which seriously restricts the development of MVDC SPS. Therefore, there is an urgent need for prospective research on fault-protection. According to the fault characteristics of MVDC SPS, a DC superconducting current-limiting switch (SCLS) is proposed, so as to realize the current limiting protection of MVDC SPS. In this paper, a small-scale SCLS superconducting coil is wound, and a current limiting experiment of the prototype is completed. The results show that SCLS has a fast current-limiting response speed and a good current-limiting effect. The experiment summarizes the characteristics of the two current limiting modes of SCLS and it is concluded that R-type current limiting mode is more suitable for MVDC SPS.

Fault current limiting method based on virtual impedance for hybrid high‐voltage direct current with cascaded MMC inverters

The hybrid high-voltage direct current (HVDC) with cascaded multi-infeed MMC inverters is proposed in recent years, and it will be put into reality in near future. But the commutation failure of the line-commutated converter (LCC) inverter will make the whole HVDC system to be blocked because the DC fault current could reach beyond the safety region of the MMC inverter. To solve such problem, this letter proposes a novel fault current limiting method based on the LCC control strategy, namely, the virtual impedance method. Such method can limit the fault current effectively and need no extra devices, which can avoid the block of the whole HVDC system on one side, and save the cost of the construction on the other side. The theoretical analysis shows that the proposed method can improve the high-frequency characteristic of the DC system and realise the fault current limitation effect. The simulations validate the analysis finally.

Topology Modeling and Design of a Novel Magnetic Coupling Fault Current Limiter for VSC DC Grids

In a voltage-source converter dc grid, a dc fault current limiter (FCL) is a key apparatus. When faults occur, it is supposed to effectively and immediately suppress transient short-circuit current to protect other equipment, e.g., converters. Additionally, it is required to bring as little negative effect as possible under normal operation. Although the respective advantages are highlighted in different FCLs, one or two key disadvantages can significantly decrease the overall performance. In this article, a novel magnetic coupling FCL (MCFCL) is proposed and achieves a good balance among its advantages and disadvantages. An MCFCL consists of a mutual inductor and some power electronic switch modules. The mutual inductor metallic primary winding is connected in series to the transmission line and magnetically coupled with the secondary winding. The secondary side impedance is controlled by the power electronic switch modules. The novel 4-segment model is proposed to demonstrate the current-limiting physics, formulate the current-limiting effect, and support the design. One medium voltage (10 kV) case study is carried out based on the numerical simulation. The MCFCL shows a better current-suppressing effect and a lower impedance under normal operation than the benchmark Reactor FCL. Finally, this article is validated on a scaled-down experimental facility.

Impact of organic solvents in combination with redox-couples on magnitude of seebeck coefficient, and electrical current in thermoelectric generators

In previous work it was shown that Ionic Liquids as active substances in thermoelectric generators have the potential to reduce the thermal conductivity as compared to Solid State materials used in conventional TEGs. Furthermore, it was observed that the Seebeck coefficient could be significantly increased. After a large variety of experiments, it appears that the remaining bottleneck coming to high performance TEGs is, first finding ILs with increased negative Seebeck coefficient, and, second sufficient current extraction. Looking at the current it appears, that higher extractions for a given redox-couple concentration are favoured at reduced viscosity. On the way to explore the effect of viscosity-induced current limitation, in a first step, the Ionic liquids are substituted by a low-viscosity organic solvent such as propylene carbonate (PC). The results showed that, indeed, the thermo-current increases significantly. It was further found that the Seebeck coefficient (SE) using PC exhibited values as high as 1.7 mV/K. Such high values were in previous work rather attributed to the use of ionic liquids. Surprisingly, by adding up to 10% of water to PC, the increased current allowed doubling the power, compared to pure PC. The paper studies the effect of combinations of solvent and redox-couples and tries to correlate the effect of water in PC looking at physical properties such as viscosity, but also the effects of charged carrier-attachment at the electrodes.

Optimal Configuration of Fault Current Limiter Based on Multi-objective Decision

To perfect the application of the fault current limiter in grid and improve the use efficiency, an optimal configuration method of fault current limiter based on multi-objective decision is proposed. Firstly, use rate of current change to select alternative branches, then taking the cost and current-limiting effect of fault current limiter as the targets, considering installation location, quantity of fault current limiter comprehensively, using α-method to determine the weight coefficient, establish multi-objective optimization model, and use immune algorithm to obtain the optimal scheme of branch installation. Next, by comparing the configuration of fault current limiter in the bus connection, the best configuration scheme is obtained. Finally, this method is verified by analyzing the IEEE39 node standard network.

Unveiling the Electric-Current-Limiting and Photodetection Effect in Two-Dimensional Hydrogenated Borophene

The electronic transport and photoelectric properties of hydrogenated borophene B4H4, which was realized in a recent experiment by Nishino [J. Am. Chem. Soc. 139, 13761 (2017)], are systematically investigated using the density functional theory and non-equilibrium Green's function methods. We find that B4H4 exhibits a perfect current-limiting effect and has high (along the zigzag direction) and low (along the armchair one) optional levels due to its strong electrical anisotropy. Moreover, B4H4 can generate sizable photocurrents under illumination, with strong photoelectronic response to blue/green light along the zigzag/armchair direction. Our work demonstrates that B4H4 is promising for the applications of current limiter and photodetectors.

Location and size determination method of SFCLs in multi‐terminal VSC‐HVDC using iterative current reduction ranking

Superconducting fault current limiter (SFCL) is a promising technology to suppress fault current in multi-terminal VSC-HVDC. However, the location and size of SFCLs determination have become a problem to be studied. This study proposes a location and size determination method of SFCLs in multi-terminal VSC-HVDC. In the proposed method, the current reduction ranking is developed to quantify the current limiting effect, and iterative process is utilised to deal with the non-linear characteristics of current reduction. With the iterative current reduction ranking, the location and size could be determined collaboratively under mathematical guidance, ensuring the optimality of current limiting effect. Fast calculation of current reduction is investigated to accelerate the determination process. Finally, the effectiveness and feasibility of the proposed method are validated in a four-terminal VSC-HVDC.

Current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

A common method to examine the current-limiting performance of saturated iron-core fault current limiter (SI-FCL) in high-voltage direct-current transmission based on voltage source converter (VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the current-limiting effect of the SI-FCL. In this paper, the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are examined. Based on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.

Unified computational model of transport in metal-insulating oxide-metal systems

A unified physics-based model of electron transport in metal-insulator-metal (MIM) systems is presented. In this model, transport through metal-oxide interfaces occurs by electron tunneling between the metal electrodes and oxide defect states. Transport in the oxide bulk is dominated by hopping, modeled as a series of tunneling events that alter the electron occupancy of defect states. Electron transport in the oxide conduction band is treated by the drift–diffusion formalism and defect chemistry reactions link all the various transport mechanisms. It is shown that the current-limiting effect of the interface band offsets is a function of the defect vacancy concentration. These results provide insight into the underlying physical mechanisms of leakage currents in oxide-based capacitors and steady-state electron transport in resistive random access memory (ReRAM) MIM devices. Finally, an explanation of ReRAM bipolar switching behavior based on these results is proposed.

Coverglass Radiation-Induced Multijunction Solar Cell Current-Limiting Effects

The implications of ionizing radiation-induced coverglass darkening on the current-limiting characteristics of presently flown multijunction (MJ) solar cells are discussed. An interesting relationship between displacement damage and ionizing radiation exists where ionizing damage to the coverglass is shown to offset displacement damage effects in the MJ stack and thereby act to maintain the current-limiting characteristics to the top cell which can result in an overprediction of mission degradation predictions.

Effect of current limitation on the adaptive behavior of memristive nanostructures

Adaptive behavior of resistive state in response to electrical stimulation has been studied for the silicon oxide based memristive nanostructures subjected to electroforming in the conditions of current compliance. The limitation of current and temperature during electroforming affects the parameters of growing conductive filaments and reduction-oxidation reactions resulting in a higher dynamic range of gradual resistance change important for neuromorphic applications.

Application of a Novel Superconducting Fault Current Limiter in a VSC-HVDC System

Compared with the traditional high-voltage direct-current based on line commutated converter (LCC-HVDC), the voltage source converter-based HVDC (VSC-HVDC) system has several advantages. However, VSCs are vulnerable to the dc short-circuit faults because of the large discharge current of the dc-link capacitor. This paper presents a novel superconducting fault current limiter (SFCL), which can effectively limit the amplitude of short-circuit current of the VSC-HVDC system. The SFCL utilizes both superconducting coils (SCs) and resistance to limit the rapidly growing current. First, the working principle and operating characteristics of the SFCL are studied. Second, the rules of parameters coordination are analyzed in order to obtain the best current limiting effect of the SFCL. Third, the electromagnetic design of SCs is done to prove the feasibility of the scheme. Finally, a simulation model is established, and the current-limiting effect of both the limiters and the parameters coordination is verified.