Pulse-by-Pulse Predictive Current Limiter

The liquid metal current limiter (LMCL) is regarded as a viable solution for reducing the fault current in a power grid. But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall, and reducing the erosion of the LMCL are challenging, not only theoretically, but also practically. In this work, a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity. Specifically, a novel fault current limiter (FCL) topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor. Further, the liquid metal self-pinch effect is modeled mathematically in three dimensions, and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation. The simulation results indicate that with the increase of current, the time for the liquid metal-free surface to begin depressing is reduced, and the position of the depression also changes. Different kinds of bubbles formed by the depressions gradually extend, squeeze, and break. With the increase of current, the liquid metal takes less time to break, but breaks still occur at the edge of the channel, forming arc plasma. Finally, relevant experiments are conducted for the novel FCL topology. The arcing process and current transfer process are analyzed in particular. Comparisons of the peak arc voltage, arcing time, current limiting efficiency, and electrode erosion are presented. The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5 times and the arcing time is reduced by more than 12%. The erosions of the liquid metal and electrodes are reduced. Moreover, the current limiting efficiency of the novel FCL topology is improved by 1%‒5%. This work lays a foundation for the topology and optimal design of the LMCL.

The design circuits of an electromagnetic short-circuit current limiter of inductive type with movable armature and moving core are considered. A comparative analysis of the design features of the electromagnetic current limiter with copper or superconducting winding is carried out. The operation principle of the electromagnetic short-circuit current limiter of inductive type with copper or superconducting winding is considered. The peculiarities of operation modes of the electromagnetic short-circuit current limiter of inductive type with copper or superconducting winding are analyzed. Using results of the mathematical modeling of the magnetic system of the electromagnetic short-circuit current limiter by the Finite Element Method in the FEMM software environment, the character of the distribution of the magnetic flux density in the nominal mode and in the current limiting mode is determined, which allows to determine the parameters of the current limiter and design features. In accordance with the design features of the electromagnetic short-circuit current limiter of inductive type, the sequence of calculation of the basic parameters of the magnetic system, taking into account the voltage drop factor, is given. The basic equations of the electric equilibrium of the voltage drop of the electromagnetic short-circuit current limiter of inductive type for nominal mode and short-circuit conditions are given. The use of the design circuit of the electromagnetic short-circuit current limiter with superconducting winding can provide energy-saving in nominal mode. The use of high-temperature superconducting wire due to increased critical parameters will ensure preservation of the superconducting state of the winding in short-circuit mode.

With the development of software technology in the automotive industry, open-source components are increasingly penetrating into the automotive systems. Researching the security of open-source software is an important topic in automotive software security. In this paper, the OTA update package of In-Vehicle Infotainment components in intelligent cockpits is analyzed to obtain the internal file system and summarize the general structure of the automotive IVI component file system and the functionality corresponding to common file paths. By analyzing the linking information of executable files in the firmware package, the dynamic linking library information of the executable files is collected to expand the coverage of components and prevent the omission of third-party components. Subsequently, the Software Composition Analysis technique is used to identify the most frequently used third-party components in the sample firmware. The results are validated by comparing the function call relationships between the sample files and the source code of the third-party components through reverse engineering analysis. Static analysis methods and patch comparison techniques are combined to verify the presence of Common Vulnerabilities and Exposures vulnerabilities in the identified third-party components. Finally, based on the experimental results, relevant recommendations are provided for the security of intelligent cockpit software.

With the development of high voltage direct current (HVDC) power transmission system, it is imperative to develop a practical current limiting device which can effectively protect the converter from the influence of fault current. Based on the topology of current limiter proposed in previous papers, considering the requirements of practical application conditions, an optimized topology is proposed, which consists of snubber circuit and arrester, both in simulation and experiment. In addition, the RC buffering circuit is added and the parameters are optimized to reduce the voltage impulse that the IGBT of fault current limiter would else bear. Simulation and experiment are carried out in DC system. Both simulation and experiment results can prove the effectiveness of the optimized current limiter circuit.

This paper is devoted to the experimental investigation of GaInSn current limiter based on a novel principle, which mainly takes advantage of the gas pressure in the liquid metal when arcing. According to this principle, an U-shape sliding part is designed and pushed upward under the gas pressure, which subsequently squeezes the arc into a narrow slot. Firstly, a specially designed setup is employed to observe the moving process of the sliding part along with the arc behavior. The whole process can be classified into three dynamic stages according to the frames obtained by a high-speed camera. Furthermore, the current-limiting property is verified additionally by comparing the two experimental results with and without the U-shape sliding part. Finally, the influences on the current-limiting property in different prospective current are also investigated in a complete setup. It demonstrates that this novel method can enhance the current-limiting efficiency to some extent.

In recent years, there is an increasing demand for various types of storage battery systems, such as home battery systems, V2H(Vehicle-to-Home)/V2G(Vehicle-to-Grid) systems, and UPS systems. Performance requirements for the power conversion system within these storage battery systems are small size, light weight and high efficiency. We propose a new power conversion system so called the GAP-D3 converter that is a bi-directional power control system, comprising of a bi-directional switch circuit topology with natural commutation switching mode. This paper describes the features of GAP-D3 converter including this new current compensation control with simulation and experimental results.

Current seismic design practice related to integral bridge girder-to-cap beam connections allows little or no lateral seismic load to be distributed beyond the girders immediately adjacent to the column. However, distribution results from several large-scale tests have shown that the distribution of column seismic moment typically engages all the girders. An approach utilizing simple stiffness models to predict distribution in integral bridge structures is presented in detail; distribution predictions based on grillage analyses also are compared. The experimental results and the analytical results from the stiffness and grillage models show that current design methods related to vertical load distribution are sufficiently accurate. However, when applied to the distribution of lateral load, similarly obtained results reveal that current design practice does not appropriately account for the amount of load that is distributed beyond the girders adjacent to the column to the nonadjacent girders. The current practice leads to excessive girder-to-cap connection reinforcement, increased girder depth, unnecessarily high seismic mass, and increased construction cost. Finally, this paper makes recommendations for more appropriate distribution of seismic lateral load in integral bridge superstructures.

High temperature superconducting fault current limiter (SFCL) is widely considered as an effective protection for power system when the short-circuit fault currents occur. This paper proposes a novel design of a hybrid SFCL with biased magnetic field which has two-stage current limiting characteristics. This kind of SFCL limits the short current using non-inductive superconducting coil at the first stage, and then by the double-split reactor at the second stage, usually 10 ms later. The advantage of this type of SFCL is saving the amount of superconducting tapes, and it is especially attractive in large current and high voltage occasions. A prototype hybrid SFCL with biased magnetic field is designed and constructed in China Electric Power Research Institute (CEPRI) using YBCO coated conductor. A high speed Data Acquisition (DAQ) System based on LABVIEW is established to monitor and control the SFCL. The current limiting ratios for this prototype SFCL have been investigated experimentally under the operating temperature of 77 K. The experimental results show that the current limiting ratio reaches to 89.66% which validates the design and proves the potential application of this hybrid SFCL.

Automotive system is the safety-critical and cost-critical heterogeneous distributed embedded system. Task assignment based on replication fault-tolerance strategy is commonly used to satisfy the reliability requirement of directed acyclic graph (DAG)-based parallel automotive application. However, automotive system development is redundancy constrained due to the limited hardwares and resources. Finding optimal redundancy under the reliability requirement saves the hardware and resource costs, and ensures the driving safety for the automotive industry, but the process is time-consuming by using traditional exhaustive method. In this paper, we propose the fast task assignment for optimal redundancy (FTAOR) algorithm to find minimum redundancy of DAG-based parallel automotive application under the established reliability requirement. Unlike exhaustive method, the verification time is reduced by using the FTAOR algorithm, which predicts and eliminates most meaningless computations effectively. Experimental results on parallel automotive applications at different heterogeneity show that the proposed FTAOR algorithm generates lower redundancy compared with the state-of-the-art heuristic algorithms and increases the task size to 150 with a shorter computation time compared with exhaustive method.

Critical power as a measure of physical work capacity and anaerobic threshold.

In this paper, the authors propose a novel application for a three-phase, solid-state, fault current limiter (FCL), consisting of a three-phase full-bridge rectifier and a DC reactor (DCR). Its configuration, operating principle, and a simple design method of the DCR, are presented. The proposed method is a combination of the FCL and a synchronous generator, and the FCL is connected to the neutral-point of the synchronous generator. As a result, an indispensable transformer in the conventional FCL can be removed, and a feature that maintains the current-limiting effect at a one-line ground fault is also obtained. To construct a guideline for creating the optimum DCR design, the current-limiting performance of the proposed method is theoretically analyzed, and the relationship between the fault current to be limited and the required DCR-inductance is derived. The experimental results obtained on a laboratory model demonstrate the effectiveness of the proposed method and validate the theoretical analysis.

SUMMARYIn recent years, various storage battery systems, such as home battery system, V2H/V2G system, and UPS system, have spread rapidly all over the world. We propose a new power conversion system for use in the previously‐stated storage battery systems. This paper describes operation analysis of this system for bi‐directional power conversion with fundamental grid‐interconnection. Good output follow‐up controllability characteristics of the proposed system are shown through experimental results.

This paper proposes a bidirectional undersea capacitive wireless power transfer system (BD-UCWPT) for the autonomous underwater vehicles (AUVs). The two H-Bridge circuits are adapted in the proposed BD-UCWPT system to achieve the bidirectional power flow. The H-Bridge circuit is built based on the GaN devices. As a result, the high switching frequency, and low power loss could be reached. The two LCLC compensation networks are respectively used in the transmitter side and receiver side. The simulation work is conducted with the Ansys Maxwell, PSIM and MATLAB. In the experiments, two seawater bags are added in the middle of two metal plates of C_S1 and C_S2 to model the seawater condition, respectively. In order to verify the theory analysis, a 100W experimental BD-UCWPT system is constructed. The experiments have been conducted in air and in seawater, respectively. The simulated and experimental results are compared with each other. It shows that, with this BD-UCWPT system, the power of AUVs could flow bidirectionally. The stable operation and high efficiency of BD-UCWPT system is verified. The research work in this paper could facilitate the application of wireless power transfer (WPT) system for AUVs and other undersea devices.

Recent studies have shown that the self-coherent systems, including the bi-directional, the Stokes-vector-modulation direct-detection (SVM-DD), and the Kramers-Kronig (KK) schemes, have the potential to reduce the cost of short-reach networks. One of the most attractive features of the self-coherent systems is that they may eliminate the necessity of a narrow-linewidth laser, which is mandatory in the conventional full coherent systems employing high-order quadrature-amplitude-modulation (QAM) formats. On the other hand, it is also recognized that the laser phase noise may have a significant impact on the system performance if there exists a large length mismatch between the signal and the CW tone in the transmission paths. In this paper, we analyze the impact of laser phase noise on the self-coherent systems numerically and experimentally by considering the bi-directional system as an example case. As a result, we show that the performance of the self-coherent system can be described efficiently by using a limited number of normalized parameters. We then reveal the existence of a distinctive threshold on the path length mismatch that influences the bit-error-rate (BER) performance; the penalty increases in a stepwise manner as the length mismatch exceeds the threshold and converges to a constant value. Based on the results, we suggest the feasibility of employing high-order QAM formats to transmit >800 Gb/s signals per polarization using a 10-MHz-linewidth laser. Finally, proof-of-concept experimental results are presented to verify the theoretical and numerical analyses.

This paper presents a simulation method of the Switched Reluctance Motors (SRM) with different number of phases, and different configurations of the stator / rotor, using the software complex Elcut and MatlabSimulink. Program Elcut used to calculate the electromagnetic field in SRM by finite element method. After performing the successive calculations of the magnetic field using a visual tool LabelMover , the result of calculation in the program Elcut is dependence of the torque and the magnetic flux of the motor from rotation angle of the rotor relative to the stator and current of the stator winding. As an example we consider the mathematical model two-package six-phase SRM power 4,5 kW with the configuration of the stator/rotor-12/8, to which can be applied different variants of motor control, including control of the input voltage, current limits and switching angles. The model is suitable for modeling switched reluctance drive (SRD) in the generator mode. The adequacy of the considered models was confirmed by experimental results.