Basic Topology Research Articles

Basic Topology, Modeling and Evaluation of a T-Type Hybrid DC Breaker for HVDC Grid

Hybrid circuit breaker (HCB) has shown good performance for interrupting dc fault current. However, a massive number of IGBTs in series is needed. These will lead to high costs and significant difficulty in balancing IGBT dynamic voltage. This paper proposes a bidirectional hybrid circuit breaker based on a cascaded half-bridge submodule structure to reduce the overall costs and implementation difficulty of HCB. The number of IGBTs is reduced by 50%, and the operating speed is fast enough. A model of a four-terminal modular multilevel converter (MMC) system with a proposed hybrid circuit breaker in different stages is developed to describe the fault blocking process more clearly. The performance of the proposed HCB is validated and compared with other HCB structure through both theoretical derivation and time-domain simulation.

Micromechanical Landscape of Three-Dimensional Disordered Graphene Networks

Disordered carbons can be considered under the modeling framework of disordered graphene networks (DGNs) due to the continuous three-dimensional connectivity and high graphitization. Correlating microstructures and mechanical behaviors of DGNs to their topology is pivotal to revealing more intrinsic features hidden by disorder. Herein, starting from basic deformations and topology, we investigate DGNs with various densities to explore their micromechanical landscape. Both the tension and shear of DGNs exhibit prolonged plastic platforms through local tearing of microstructures. However, compression displays special plastic damages of forming kinklike puckers and sp3-bonded carbon, resulting in a tension-compression asymmetry of DGNs. Out-of-plane topological defects contribute to the main negative-curvature topology in deformed DGNs. Moreover, there are novel scaling laws where both the Young's modulus and strength (logarithms) follow an inversely proportional scaling with respect to average angular defects. Ashby charts demonstrate that the mechanical properties of DGNs can reach the theoretical limit region, surpassing those of most conventional materials.

A new switched-capacitor multilevel inverter with soft start and quasi resonant charging capabilities

Switched-capacitor multilevel inverters (SCMLIs) are gaining widespread attention in recent decades due to their simple design, voltage boosting capability, and inherent capacitor voltage balancing feature. However, the advantages offered by SCMLIs come at the cost of employing a higher number of active and passive components and capacitor voltage balancing issues with an inrush current profile. This paper introduces a novel configuration of SCMLIs with a lower number of power components with inherent voltage boost. The basic 5-level topology consists of a single capacitor, an inductor, a diode, and seven active switching elements. To improve the transient response and the inrush current profile of the converter, a soft start and quasi-resonant charging capability has been explored and implemented. Considering the inherent capacitor voltage balancing of the proposed SCMLI, a new finite control set-model predictive control (FCS-MPC) method with a single objective and a less computational burden is also developed, which contributes to injecting a fully controlled current for the grid-connected applications. The proposed topology is compared with other existing five-level inverter topologies to show its superior capabilities/advantages. And finally, the performance of the proposed topology and its associated FCS-MPC mechanism are validated by the measurement results.

Robustness Analysis of Air Route Network Based on Topology Potential and Relative Entropy Methods

Air route network (ARN) is the important carrier of air transport, and its robustness has important influence on the safety and stability of air transport. To analyze the robustness of ARN, in this paper, a topology potential relative entropy (TPRE) model is proposed, based on topology potential (TP) and relative entropy (RE) methods. Firstly, the TPRE model is established as the theoretical basis for the research. Secondly, an air route reduction network (ARRN) model is constructed according to real Chinese ARN. Besides, the basic topology features of ARRN are given by complex network theory. To prove the applicability, objectivity, and accuracy of the proposed method, attack strategies including random, degree, betweenness, closeness, eigenvector, and Bonacich are used to attack ARRN. Eventually, the performance of ARRN robustness is analyzed by network efficiency, size of giant component, and the proposed TPRE model. This conclusion has practical significance for optimizing ARN structure and improving airspace efficiency.

New Soft Structure: Infra Soft Topological Spaces

It is always convenient to find the weakest conditions that preserve some topologically inspired properties. To this end, we introduce the concept of an infra soft topology which is a collection of subsets that extend the concept of soft topology by dispensing with the postulate that the collection is closed under arbitrary unions. We study the basic concepts of infra soft topological spaces such as infra soft open and infra soft closed sets, infra soft interior and infra soft closure operators, and infra soft limit and infra soft boundary points of a soft set. We reveal the main properties of these concepts with the help of some elucidative examples. Then, we present some methods to generate infra soft topologies such as infra soft neighbourhood systems, basis of infra soft topology, and infra soft relative topology. We also investigate how we initiate an infra soft topology from crisp infra topologies. In the end, we explore the concept of continuity between infra soft topological spaces and determine the conditions under which the continuity is preserved between infra soft topological space and its parametric infra topological spaces.

Design Engineering of Tri‐Band Ulu‐Shape NGD Circuit

AbstractThis paper investigates a negative group delay (NGD) design of Ulu geometrical shape circuit. The NGD basic topology is constituted by a coupled line coupler with two‐port terminated by open‐ended stub. The S‐matrix model of the topology is presented. The design equations allowing to determine the NGD circuit parameters in function of the NGD function specifications, NGD center frequency, NGD values and insertion loss are presented. As proof of concept, a microstrip circuit is designed and fabricated. As expected, the tested results confirm that the circuit behaves as bandpass NGD function. The modeled, simulated and measured results are in good correlation. The POC operates with tri‐band NGD behavior with center frequencies around 0.645, 1.285, and 1.87 GHz with NGD values of about −3.5, −2, and −1 ns, respectively.

Conference key agreement based on continuous-variable quantum key distribution

We propose a conference key agreement protocol that satisfies future demands for secure communication, which requires that all participants contribute to the generation of the shared key and that any nontrivial subset of participants cannot determine the shared key alone. We construct a basic network topology which supports three participants communication by connecting to a distrusted intermediate station via insecure links. The participants independently decide whether to send a quantum signal pulse or a local oscillator pulse to the intermediate station at any time window i. We derive the secret key rate from our protocol, and a novel encoded strategy is adopted. The protocol is a promising step towards conference key agreement.

Transfer network of high-speed rail and aviation: Structure and critical components

In this paper, we utilize network theory to model and study the coupled high-speed rail–aviation network (HSR–AN) in China. The HSR–AN depicting the transport services is modelled as a transfer network in P-space (TNP) in this research. The basic topology properties of the TNP and the corresponding critical components (e.g., nodes and areas) are analysed. As one type of spatial networks coupled two transportation networks, TNP of HSR–AN, counterintuitively, exhibits small-world properties which can be attributed by offering service connecting long-distance cities without transfer and complementary relationship between two transport modes. Additionally, an analysis of vital node (area) in vulnerability environment indicates that the importance of network components critically depends on the economic development level, population density, and geographical features in the corresponding city. Besides, the failure of high-speed rail station generates worse effect than that on airport in HSR–ANs. The findings are beneficial for enhancing the efficiency of HSR–ANs and developing emergency response plans for transport managers.

Coloring Invariant for Topological Circuits in Folded Linear Chains

Circuit topology is a mathematical approach that categorizes the arrangement of contacts within a folded linear chain, such as a protein molecule or the genome. Theses linear biomolecular chains often fold into complex 3D architectures with critical entanglements and local or global structural symmetries stabilised by formation of intrachain contacts. Here, we adapt and apply the algebraic structure of quandles to classify and distinguish chain topologies within the framework of circuit topology. We systematically study the basic circuit topology motifs and define quandle/bondle coloring for them. Next, we explore the implications of circuit topology operations that enable building complex topologies from basic motifs for the quandle coloring approach.

Characterization and comparison of gene-centered human interactomes.

The complex web of macromolecular interactions occurring within cells—the interactome—is the backbone of an increasing number of studies, but a clear consensus on the exact structure of this network is still lacking. Different genome-scale maps of human interactome have been obtained through several experimental techniques and functional analyses. Moreover, these maps can be enriched through literature-mining approaches, and different combinations of various ‘source’ databases have been used in the literature. It is therefore unclear to which extent the various interactomes yield similar results when used in the context of interactome-based approaches in network biology. We compared a comprehensive list of human interactomes on the basis of topology, protein complexes, molecular pathways, pathway cross-talk and disease gene prediction. In a general context of relevant heterogeneity, our study provides a series of qualitative and quantitative parameters that describe the state of the art of human interactomes and guidelines for selecting interactomes in future applications.

A Topology Analysis-Based MMC-HVDC Grid Transmission Capacity Calculation Method

Modular multilevel converter-based high voltage direct current (MMC-HVDC) has a broad application prospect in renewable energy transmission. With the development of converter capacity, the transmission capacity calculation for MMC-HVDC grids becomes important for power dispatching. The existing method depends on manual work and is suitable for a simple grid. However, as the grid structure and operation modes become more and more complex, it becomes difficult to calculate the transmission capacity of different operation modes for an MMC-HVDC grid. This paper analyzed and simplified affecting factors and basic topologies. On this basis, a topology-based MMC-HVDC grid transmission capacity calculation method is proposed. First, an MMC-HVDC grid is divided into sending end grid, transmission section lines, and receiving end grid. Then the power limits of these three parts are calculated. Finally, the transmission capacity is determined by analyzing the connection mode of these three parts. This method can be adapted to any kind of MMC-HVDC grid and can be easily programmed.

Non-Isolated High Step Up in Voltage DC–DC Converter Topology for Renewable Applications

In the class of the boost converters, the conventional DC–DC boost converters are in common practice but their limited boost capabilities at higher duty ratios are one of the concerns. The isolated and non-isolated step-up DC–DC converters are one of the remedies of the above issue. The presence of switched inductor and switched capacitors in the circuit of non-isolated configuration can provide considerable step-up in voltage at the output, and also facilitate lower voltage stress on components. In this paper, work has been done to propose three non-isolated high-voltage gain DC–DC boost converter topologies. Along with the high voltage gain, the topologies also have lesser voltage stress across the active power switches and diodes used in topologies. The proposed topologies are suitable for low dc input levels like renewable sources, microgrid and grid-connected applications. A Matlab/Simulink 2017a environment is utilized to derive, design and simulate the proposed topologies for a 100-W load operation. The basic topology is also realized in hardware as a prototype circuit with 100-W resistive load, operated at 50[Formula: see text]kHz switching frequency.

A boost type switched‐capacitor multi‐level inverter for renewable energy sources with Self‐Voltage balancing of capacitors

This article proposes a single-phase double-source 27-level basic inverter structure based on Switched-Capacitors (SCs) circuit for renewable energy sources. The extendibility, low Blocking Voltage (BV) on semiconductors, step-up capability, and self-voltage balancing of capacitors are the main advantages of the suggested basic structure. Using double H-bridges to generate bi-polar voltage waveform, the blocking voltage on the semiconductors limit to only 0.692 Vo,max. The Average of Normalized Blocking Voltage (ANBV) on semiconductors of basic topology is only about 33.52%. Two extended structures have been presented with higher output voltage steps and boosting factors. The first extended topology composed of two (right and left) Generalized Switched Capacitor based Modules (GSCMs), results in reduced sources (only 2), increased steps, low BV on semiconductors, and boosting factor of 2n (n: number of SC Cells). The second extended topology can be realized by applying more cascaded Switched-Capacitor Modules (SCMs), which benefits from quadruple-gain and increased levels (9m, m: number of cascaded modules). The suggested topologies properly supply the zero or low power-factor load types. The superiority of proposed configurations over recently presented similar structures has been compared and verified. The experimental outcomes of the basic topology have also been provided to validate its correct operation.

Model Predictive Control for Connected Vehicle Platoon Under Switching Communication Topology

Vehicular platoon control can effectively achieve group consensus, improve vehicular running safety and increase road capacity. However, some constraints exist in practical situations due to the limitations of traffic environment in time-varying metrics (time-delay, packet-dropout or interruption) in wireless communication systems. In this work, a distributed model predictive control (MPC) algorithm is proposed for connected vehicle platoon with a focus on switching communication topologies and control strategy under abnormal communications. Firstly, the predecessor-leader following is selected as the basic communication topology, by which the switching communication topology and the desired vehicle spacing policy are established. Secondly, the platoon control algorithm of connected vehicles is established and a set of constraints is analyzed. Thirdly, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathcal{ L}}_{2} $ </tex-math></inline-formula> -norm string stability criterion and the asymptotic stability criterion are considered within the proposed MPC. Finally, a co-simulation platform for connected vehicle platoon is developed based on Prescan/Matlab/V2X communication simulator. In addition, the platoon control algorithm is tested in three traffic scenarios including normal communication, leading vehicle with abnormal communication and following vehicle with abnormal communication. The experiments demonstrate that the communication topologies in different communication environments can be switched well in real time through the proposed platoon control algorithm. In addition, the string stability, the consistency of vehicle spacing, speed and acceleration are proven to be guaranteed simultaneously.

Topology of non-inductive DC/DC converters with galvanic isolated circuits

Non-inductive (throttle-free) DC/DC converters are used in low-power and highly integrated electronic systems. A circuit analysis of the basic topologies of non-inductive DC/DC charge-pumped converters which perform typical DC-voltage conversions, i.e., lowering, raising and inverting, was carried out. The galvanic isolation between the input and output circuits of the converter was achieved even in the integrated version due to forming a time delay of the switches (Dead Time, DT), commuting a “flying” capacitor, which is transferring the charge to the storage capacitor and the load. A circuit of the DT driver was developed and its parameters, at which the through-current flow in the switch is prevented and the conditions of galvanic isolation of the input and output circuits are satisfied, were studied. The simulation was built with a popular Electronics Workbench software, widely used in training of specialists in radio electronics at higher educational institutions. The results of the study of the basic power characteristics of DC/DC conversion, such as output current and voltage, voltage transfer coefficient, efficiency, output equivalent resistance, were presented. The efficiency of conversion was estimated by varying the capacities of the “flying” and storage capacitors, the resistance of the switches in the closed state, and the frequency of switching. It is proved that the charge pumping method is simple and effective at low load currents (mA units), when both the voltage transfer coefficient from input to output and efficiency are high, and are approaching to “one”. However, with the increase of the load current, the voltage transfer coefficient and efficiency decrease, the output voltage ripples increase.

A linear-elastic heuristic-molecular modelling for plane isotropic micropolar and auxetic materials

A discrete Lagrangian approach is the basis for modelling the macroscale elastic response of a solid material, which can be homogeneous as well as a periodic composite. The basic topology is a square “heuristic molecule” that is an assemblage of four rigid bodies with a definite shape bonded by elastic springs. This is the minimum unit cell, UC, that contains all the macroscopic mechanical properties of the solid material, object of study. The paper presents 4 unit cells, in progression from a basic molecule bonded by 2 types of central forces, to a refined “Cosserat-auxetic” molecule that is connected by 4 types of shear and central bond-springs. The emphasis is given to the isotropic response in relation to the value of the macroscopic Poisson ratio, and the four examples of UC topologies are presented showing their relationship to different materials at the macro-scale: from a “rari-constant” continuum, through a standard isotropic Cauchy continuum, up to an isotropic centre-symmetric auxetic Cosserat solid.

Evolution of novel motor controller with direct current excitation capability

<p indent="0mm">The use of an inverter with fully controlled power electronic devices is the primary method of modern alternating current (AC) motor control. In recent years, a series of new reluctance motors with direct current (DC)-bias sinusoidal current have been proposed. Unlike the motor controller based on the traditional half-bridge topology inverter, the power electronic converter driving and controlling this type of reluctance motor must have stator DC excitation capability. This paper introduces the basic control principle and topology of a new motor controller with integrated DC excitation capability. Accordingly, through the introduction of four improvement schemes, an improvement roadmap of the new motor controller is shown. This paper proposes improvements in terms of power device capacity and control freedom, which can effectively reduce the cost, volume, and power loss of the new motor controller. Furthermore, through in-depth discussion, a comparison of the basic topology, and the three improved topologies proposed by the authors, it is concluded that the series-end winding topology represents a new motor controller with both the best hardware and control performance. Compared with the traditional half-bridge topology, the proposed topology can achieve nearly double the modulation ratio and speed range under the condition of only adding one bridge. This is not only suitable for special reluctance motors but also the control of various AC motors and can be further extended to multiphase systems. All of the five new motor controllers have prototypes and experimental results, the latter indicating that the series of new motor controllers based on the requirement of injecting DC into the stator winding yielded gradual improvements in performance.

Generalized diamond‐type single DC‐source switched‐capacitor based multilevel inverter with step‐up and natural voltage balancing capabilities

This paper proposes a diamond-shaped high step-up switched-capacitor based basic multilevel inverter topology. The basic switched-capacitor (SC) stage consists of 2 active switches, 2 diodes, and 2 capacitors. Using a single DC source with the unfolding circuit (10 switches, 5 capacitors, and 5 diodes) results in the production of 17 voltage-steps at the output with the gain of up to 8 times of the input voltage. By extending the diamond-shaped switched-capacitor stages, higher voltage levels and voltage gains can be possible. The suggested topology employs two half-bridges (instead of a full-bridge) to produce positive, zero, and negative steps, which reduces the Voltage Stress (VS) on two output switches and consequently reduces Total Voltage Stress (TVS). In addition, the natural voltage balancing of capacitors eliminates the need to an additional control circuitry and consequently reduces the total converter size, complexity, and cost. In addition, modularity, scalability, low voltage ripple on capacitors, low total voltage stress, high power quality, and capability of supplying low/medium power factor (R-L) loads are some of the merits of the proposed topology. The low Cost Function (CF) obtained in the comparison section as well as experimental results verifies the advantages of the proposed topology.

A Yokeless Axial Flux Induction Motor for Electric Vehicles Based on Grain-oriented Silicon Steel

A novel axial flux induction motor is proposed as the driving machine for electric vehicle, the motor consists of two rotors and one yokeless stator. Benefit from this structure, grain-oriented silicon steel can be used to reduce the weight and improve efficiency. The present paper provides the basic topology of the motor, discussing the design method and analyzing the performance. A prototype is designed, considering the 3D finite element method is time-consuming and inefficient, analytical calculation method is deduced to calculate the performance of the prototype, the results agree with those obtained by finite element calculation, that verifies the effectiveness of this method.

Theoretical Optimization of the Si GSS-DMM Device in the BaSIC Topology for SiC Power MOSFET Short-Circuit Capability Improvement

The BaSIC(DMM) topology has been experimentally demonstrated to improve the short-circuit time for a 1.2 kV SiC power MOSFET product from 4.8 μs to 7.9 μs with a 17% increase in on-state resistance by utilizing a commercially available 100 V rated Gate-Source-Shorted (GSS) Si Depletion-Mode power MOSFET (DMM). The optimization of the Si GSS-DMM is discussed in this paper to achieve even superior performance, namely larger short-circuit time with less increase in on-resistance. It is theoretically demonstrated for the first time that a highly desirable short-circuit time of 10 μs, similar to Si IGBTs, can be achieved for two SiC power MOSFET products with less than 3% increase in on-resistance. This was accomplished by reducing the breakdown voltage rating of the Si GSS-DMM from 100 V to 30 V, altering the cell design parameters, and utilizing the trench-gate design. The theoretical analysis provided in this paper provides valuable design guidelines for manufacturers of Si GSS-DMM devices to achieve optimum performance for use in the BaSIC(DMM) topology.