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This paper describes a flow control of the dye in the paper mill with the quasi-Z-source indirect matrix converter (QZSIMC) fed induction motor drive. More than a decade the voltage-source inverter (VSI) and current-source inverter (CSI) have been used to control the speed of the induction motor, which in turns controls the flow of dye. Recently, the matrix converter (MC) has been an excellent competitor for the VSI or CSI for its compactness. The voltage transfer ratio of the VSI, CSI, and MC has been limited to 0.866. Thus, the efficiency of these converters is less. To improve the voltage transfer ratio the quasi-Z-source network (QZSN) is to be used between voltage source and indirect MC (IMC). The modification in the shoot-through duty ratio of the QZSN varies the voltage transfer ratio greater than 0.866. Different voltage transfer ratios are needed for different voltage sag conditions. For a variation of the duty ratio of the QZSN, the fuzzy logic controller has been presented. To control the IMC vector control with space vector modulation has been presented. This paper proposes the implementation of QZSIMC adjustable speed drive for the flow control of dye in paper mill during different voltage sag conditions. A 4-kW prototype has been built and the effectiveness of the proposed system is verified with simulation results and experimental setup. Simulation is done in MATLAB, Simulink platform. Experimental setup is done with the aid of a TMS320F2812 (Texas Instrument) processor. The experimental results validate the maintenance of the speed of an induction motor at the set condition, thus controlling the perfect flow of dye in paper manufacturing technology. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices ($\mu $ PADs) are a clean-room free, cost-effective, and self-pumping flow-based rapid prototyping technique, which is compatible with a varying range of fluids. Until now, $\mu $ PADs have been primarily fabricated using crayons, and plotting-machine and solid-ink printers. These devices can be easily employed for various detection schemes, such as electrical, electrochemical, and optical. The presence of a capillary effect in the chromatograph paper has made $\mu $ PADs independent of a passive device, such as pumps and valves. In this paper, an alternative and a novel method is proposed to achieve the $\mu $ PADs effortlessly using a 3-D printer (3DP), which has many advantages over the existing methods. For creating hydrophobic barriers for microchannel walls, polycaprolactone (PCL) filament was used with fused-deposition modeling (FDM) 3DP. PCL filaments were deposited on the chromatography paper followed by heating for determining the overall dimension and depth of the microchannel at which PCL melts and penetrates into this paper. The $\mu $ PADs are characterized and optimized for two parameters. First, fabrication parameters, such as heating temperature and time duration, were used for the creation of the hydrophobic barrier using a hot air oven. Second, the microchannel parameters, such as microchannel width, boundary thickness, chromatography paper grade, and microchannel source shape (rectangular, triangular, and circular) were used for the fluid-flow by measuring the time taken by fluid to travel a fixed length of the microchannel. After rigorous analysis, it was found that for the creation of the hydrophobic barrier, $\mu $ PADs heated between temperature 120°C to 150°C require 30 min. Under optimized conditions for the fluid flow, the chromatography paper grade 1441 with a triangular source microchannel was found to be best. This paper provides an alternate, simple, and optimized method toward the development of the application-specific $\mu $ PADs, such as the micro-viscometer, which, in turn, can be widely used to monitor various types of fluids including human bodily fluids. [ABSTRACT FROM AUTHOR]

In this paper, we extend the interference channel with degraded message sets model by introducing multiple secondaries. The new model allows for multiple concurrent transmissions in a wireless network by employing dirty paper and superposition coding. We apply the proposed scheme to the communication between nodes in a wireless mesh network (WMN). The cases of different WMN. topologies are analyzed, and numerical results show that considerable capacity gains are achieved when using the proposed model with multiple secondaries. [ABSTRACT FROM AUTHOR]

In this paper, we characterize the capacity of a new class of discrete memoryless multicast networks having a tree topology. For achievability, a novel coding scheme is constructed where some relays employ a combination of decode-and-forward and compress-and-forward and the other relays perform a random binning such that codebook constructions and relay operations are independent for each node and do not depend on the network topology. For converse, a new technique of iteratively manipulating inequalities exploiting the tree topology is used. This class of multicast tree networks includes the class of diamond networks studied by Kang and Ulukus as a special case. [ABSTRACT FROM PUBLISHER]

Heterogeneous graph embedding aims at learning low-dimensional representations from a graph featuring nodes and edges of diverse natures, and meanwhile preserving the underlying topology. Existing approaches along this line have largely relied on meta-paths, which are by nature hand-crafted and pre-defined transition rules, so as to explore the semantics of a graph. Despite the promising results, defining meta-paths requires domain knowledge, and thus when the test distribution deviates from the priors, such methods are prone to errors. In this paper, we propose a self-learning scheme for heterogeneous graph embedding, termed as self-guided walk (SILK), that bypasses meta-paths and learns adaptive attentions for node walking. SILK assumes no prior knowledge or annotation is provided, and conducts a customized random walk to encode the contexts of the heterogeneous graph of interest. Specifically, this is achieved via maintaining a dynamically-updated guidance matrix that records the node-conditioned transition potentials. Experimental results on four real-world datasets demonstrate that SILK significantly outperforms state-of-the-art methods. [ABSTRACT FROM AUTHOR]

This paper presents a review of the literature on state estimation (SE) in power systems. While covering works related to SE in transmission systems, the main focus of this paper is distribution system SE (DSSE). The critical topics of DSSE, including mathematical problem formulation, application of pseudo-measurements, metering instrument placement, network topology issues, impacts of renewable penetration, and cyber-security are discussed. Both conventional and modern data-driven and probabilistic techniques have been reviewed. This paper can provide researchers and utility engineers with insights into the technical achievements, barriers, and future research directions of DSSE. [ABSTRACT FROM AUTHOR]

Geared devices are commonly used to match the operating speed and torque of the power source with the second mover. Such geared devices are usually mechanical gears. As counterparts of the conventional mechanical gears, magnetic gears (MGs) are becoming promising devices, mainly due to the merits of physical isolation between moving parts, no gear lubrication, no mechanical fatigue, inherent overload protection and reduced maintenance, etc. Recently, several new topologies have been proposed to achieve better performances. In this paper, a general review of MGs is presented, including a discussion of the most common and upcoming topologies and a description of the working principle. A comparison of different topologies is carried out in terms of gear ratio and torque density. The main computational techniques generally adopted for coaxial MGs are listed and described. Some key aspects concerning the design, the existed challenges, and potential applications are also discussed. This paper aims to provide a comprehensive overview of the MG for readers working in this field. [ABSTRACT FROM AUTHOR]

This paper proposes a new coupling matrix synthesis technique called the coupling matrix compression technique, which focuses on reducing the dimension of the $N+2$ coupling matrix. The presented coupling matrices can be compressed, and this technique can be used to design dual-mode resonators for high-isolation dual-band filters. One dual-mode resonator is represented as two closely coupled resonators when using this technique. The formulae for resonant frequencies and $\omega _{m}$ in dual-mode theory are also derived in this paper. A dual-mode embedded hairpin resonator is designed and analyzed using this technique, and a dual-band filter using the proposed resonators is designed and fabricated to validate the proposed technique. [ABSTRACT FROM AUTHOR]

New methods for extending the tunability range in second-order voltage-controlled oscillators (VCOs) with quadrature outputs are presented and compared in this paper. Linear dependence is the most common type of relation between frequency of oscillations (FO) and control voltage (or current) in communication subsystems (VCOs). However, there are other nonlinear types of dependencies that are advantageous (quadratic and cubic) and should be further studied. Positions of controllable blocks within the structure of the oscillator (providing parameters influencing time constants of integrators) in two scenarios are studied together. The impact of controllable parameters of these additional elements on FO as well as on produced output signal levels is evaluated. The simulation and experimental results are shown to confirm expected behavior of solutions in the case of the quadratic type of control of FO. Nowadays, standard linear control offers a tunability ratio 10:1 (for the same ratio of parameters that control the FO) only. However, in this paper, the experimental tests yield a tunability ratio 80:1 (50 kHz–4 MHz) for dc control voltage within the range 0.175–1.75 V (10:1). The presented approach is very beneficial for low supply voltage systems requiring a wide range of tunability and also for utilizing active devices having limited range of adjustability of their controllable parameters while still requiring wide tunability. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a design process for a plasmonic grating structure to induce the resonance at a target wavelength. In a specific condition, surface gratings may induce the surface plasmon propagation due to the diffraction and the resonance wavelength of the surface plasmon propagation is dependent on the grating shape. The grating configuration was designed by the topology optimization scheme based on the reaction-diffusion equation. To shift the resonance wavelength to the target wavelength, this paper maps the frequency response function to a probability distribution function (PDF). The mean value from the PDF becomes a part of the objective function and the design objective is set to minimize the distance between the present resonance wavelength and the target wavelength while keeping the energy intensity. The process of simulation and optimization was performed using the commercial package COMSOL combined with MATLAB programming. [ABSTRACT FROM AUTHOR]

This paper examines the problem of designing integrated systems of photovoltaic (PV) arrays and battery cells in a manner that achieves self-balancing by design. This paper focuses on two topologies for integrating PV and battery cells, both of which connect PV generation to each battery cell directly, either with or without dc–dc conversion. This paper proves, using Lyapunov stability methods, that both the topologies are globally, asymptotically self-balancing. This means that initial differences among battery cells in either the state of charge or other internal state variables are guaranteed to diminish asymptotically with time. This self-balancing behavior reduces the amount and hence the cost of the power electronics needed for energy storage integration into PV farms significantly compared to conventional integration topologies—an argument substantiated using a financial assessment in this paper. This paper extends previous work by the authors on self-balancing PV energy storage systems in four significant ways. First, the proof of self-balancing is provided using equivalent-circuit battery models of arbitrary order, as opposed to first-order models. Second, this proof is provided for multiple integration topologies, instead of just one. Third, we demonstrate this self-balancing behavior experimentally, using a hardware-in-the-loop setup, for the first time. Finally, we perform a cost benefit analysis of our hybrid topologies in comparison to a benchmark system in order to quantify the integration cost reduction due to self-balancing. [ABSTRACT FROM AUTHOR]

Although smart home has received wide attention in recent years, numerous scholars focus more on energy optimization strategy than energy dispatch hardware device (named energy router). Meanwhile, this energy router should have several features, i.e., high renewable energy utilization, energy multi-port and low volume. Thus, this paper designs a nine-port energy router regarding smart home and proposes a multimode hierarchical management strategy for this energy router. First, for the multi-port demand of wind, solar, storage and utilization, this paper presents a nine-port energy router to improve the renewable energy consumption and power supply flexibility. In addition, to reduce the volume of the energy router, a non-isolated AC/DC hybrid topology is constructed through embedding the integrated power electronic converters, which achieves the miniaturization of the energy router. In order to improve the renewable energy utilization rate, the decentralized module control is proposed for the components of energy router to provide the voltage and frequency support for system, and realizes the power sharing of distributed generations (DGs). Furthermore, the power exchange control with three-mode switching is proposed to guarantee the global energy flow balance under complex conditions. Eventually, the feasibility of the energy router is verified by the simulation and experiments. [ABSTRACT FROM AUTHOR]

Axial flux and radial flux cycloidal permanent magnetic gears are characterized by high gear ratios and high torque densities; however, their rotors experience large unbalanced forces, which stress the bearings used in the gear. This paper presents a new cycloidal magnetic gear topology that combines the radial and axial flux topologies. The paper analyzes the forces and torques contributed by the axial and radial magnets in this topology using 3D finite element analysis. It was found that the perpendicular force is necessary to transfer torque to the high-speed shaft and, thus, cannot be cancelled out, but the eccentric component of the magnetic forces can be largely cancelled out, potentially reducing bearing losses and increasing the lifespan of the bearings used in the gear. A proof-of-concept prototype was constructed. Experimental slip torque results matched 3D finite element analysis (FEA) simulations to within 15%, and testing showed that no-load losses were reduced and the slip torque was increased by combining both axial and radial topologies, compared to using an axial configuration alone. [ABSTRACT FROM AUTHOR]

In order to achieve the purpose of extending the speed range and reducing power electronics devices for the permanent-magnet linear motor drive system, a half-centralized open-end winding (OEW) topology is studied for rail transit applications in this paper. In this topology, compared with the traditional OEW topology, the number of voltage-source-inverters (VSIs) can be reduced from four to three to drive two OEW movers and all these VSIs share a common dc bus voltage. In order to improve the steady-state performances, a four-vector phase model predictive voltage control (FV-PMPVC) is proposed in this paper. Due to the spatial distribution of phase voltage vector (PVV), an orthometric synthesis principle (OSP) is proposed to calculated the duration time for the vector synthesis, which reduces the computation burden and enhances the robustness. Comparing the existing control method, FV-PMPVC can get similar dynamic performances but better steady-state performances. Additionally, the half-centralized topology using FV-PMPVC can have same speed range while less VSIs are required. The effectiveness of FV-PMPVC is verified by experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a reconfigurable dc–dc converter for maximum thermoelectric generator (TEG) energy harvesting in a battery-powered duty-cycling wireless sensor node. The proposed dc–dc converter adopts discontinuous energy harvesting, which operates in single-input dual-output (SIDO) boost, battery-TEG pile-up buck (BTPB), dual-phase buck–boost (DPBB), and battery supplied buck modes with a single shared inductor. Fabricated in a 65-nm CMOS process, the converter adopts an adaptive dead-time controller for zero-voltage switching (ZVS) and an adaptive switch size (ASS) with maximum power point tracking (MPPT) to maximize efficiency in a wide TEG voltage range. The SIDO boost mode achieves 88.5% and 81.1% peak end-to-end efficiency with maximum and no-load conditions (only charging the battery), respectively. The combination of BTPB and DPBB modes to maximize the TEG power extraction during the battery-powered operation results in up to 44% saving in battery power. The battery-supplied buck mode achieves 93.3% peak efficiency. [ABSTRACT FROM AUTHOR]

In 2017, three sub-synchronous resonance (SSR) events were reported in the transmission system of Electric Reliability Council of Texas (ERCOT). These three events with different consequences are due to the same cause, i.e., Type-3 wind farms radially connected to a series compensated transmission line. The objectives of this paper are: 1) to build a testbed to replicate these real-world events and investigate what causes the different consequences; 2) to find out the impact of wind penetration level and wind speed on SSR; and 3) to investigate how to mitigate SSR. The replication testbed is built in MATLAB/Simpowersystems with each wind farm represented by a single aggregated wind turbine with full dynamics. The challenge of replication is the limited information about those three events, the ERCOT system, and the wind farms. Nevertheless, relying on simplification and assumptions, we are able to replicate the three events. Our contributions include the configured testbed for Type-3 wind farm SSR studies, diagnosis of impacting factors on SSR, and the confirmation of an SSR mitigation strategy through grid-side converter ac voltage command signal modulation. [ABSTRACT FROM AUTHOR]

High specific power electric motor is a key enabling technology for electric/hybrid-electric propulsion for aircraft. High-frequency, air core machine topologies show potential for high specific power when the machines are integrated within jet engines at high speed, e.g. 15,000 rpm. In this paper, we explore how these machines scale to a boundary layer ingestion (BLI) fan application in newly proposed Single-aisle Turboelectric Aircraft with an Aft Boundary Layer Propulsor (STARC-ABL). Detailed analytical models that have been experimentally verified, and an evolutionary genetic algorithm are utilized to choose an optimized design for the BLI propulsor. Analyses show that a 2.6 MW, 11 kW/kg, 98% electric motor is achievable. [ABSTRACT FROM AUTHOR]

The number of applicable carrier-based pulsewidth modulation (PWM) patterns increases with the growth of output levels in scalable multilevel topologies, such as active-neutral-point-clamped (ANPC) converters. Therefore, it is hard to optimize PWM for such topology, especially with large output levels. In this paper, a simplified and modular carrier-based PWM design approach for multilevel ANPC converters is proposed. Inspired by the decomposition theory, the topology decomposition is introduced in this paper to decompose an N-level ANPC converter into low-level subtopologies. Then, the complete set of applicable PWM patterns is derived based on ANPC operation principles, which makes it possible to optimize the performance based on the various requirements in applications. Meanwhile, the carrier-based PWM is implemented through the utilization of subtopologies with low-level modulation schemes, such that the design process of carrier-based PWM is greatly simplified and modularly realized. Both the complete PWM patterns and PWM design examples with experimental results of several ANPC converters are provided to show the feasibility and modularity of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents study of design characteristics with wide constant power speed range (CPSR) for electric vehicle Propulsion. Through analysis of interior permanent magnet synchronous motor (IPMSM) control logic, design characteristic of extending CPSR is proposed. To achieve wide CPSR, center of voltage limit ellipse should be placed at cross point of current limit circle and d -axis. To analyze characteristic of voltage ellipse, four types of representative IPMSM rotor topologies are selected. Through rotor topology analysis, tendency of \phi _{f} and L_{\mathrm{ ds}} $ parameters which decide center of voltage limit ellipse is analyzed. This paper also considers shifting of voltage limit ellipse center according to change in motor speed. Reflecting the result, this paper focuses on center of voltage limit ellipse position at maximum speed, because central coordinates of high-speed range determine characteristics of CPSR. Through the analysis result, this paper suggests direction of IPMSM design for wide CPSR. [ABSTRACT FROM AUTHOR]

This paper is aimed to compare the performance of toroidal inductors and planar spiral inductors in multilayered technologies, in terms of achievable inductance density. The optimization of planar toroidal inductors in multilayered substrates is investigated theoretically, and closed formulae are derived for their inductances as a function of geometrical parameters. The obtained model is validated by experimental results and electromagnetic simulation. From the comparison of the inductance of toroidal inductors and compact spiral inductors, a selection rule is proposed to choose the most suitable topology that leads to the most compact design. [ABSTRACT FROM AUTHOR]

Link prediction aims at inferring missing links or predicting future ones based on the currently observed network. This topic is important for many applications such as social media, bioinformatics and recommendation systems. Most existing methods focus on homogeneous settings and consider only low-order pairwise relations while ignoring either the heterogeneity or high-order complex relations among different types of nodes, which tends to lead to a sub-optimal embedding result. This paper presents a method named Heterogeneous Hypergraph Variational Autoencoder (HeteHG-VAE) for link prediction in heterogeneous information networks (HINs). It first maps a conventional HIN to a heterogeneous hypergraph with a certain kind of semantics to capture both the high-order semantics and complex relations among nodes, while preserving the low-order pairwise topology information of the original HIN. Then, deep latent representations of nodes and hyperedges are learned by a Bayesian deep generative framework from the heterogeneous hypergraph in an unsupervised manner. Moreover, a hyperedge attention module is designed to learn the importance of different types of nodes in each hyperedge. The major merit of HeteHG-VAE lies in its ability of modeling multi-level relations in heterogeneous settings. Extensive experiments on real-world datasets demonstrate the effectiveness and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

With the proliferation of online social networks, the identification or classification of real-life relationship between users has been very useful for many applications such as financial fraud detection. In real life, usually people with different relationships would present gifts with special meanings to each other on different dates. In many Asian cultures, especially in Chinese culture, the red packet is a traditional form of monetary gift. With the rapid development of the Internet, people gradually began to give electronic red packets instead of paper ones as the means of money gifting on social network platforms. As motivated, in this paper we advocate a novel approach that exploits users’ red packet interactions for users relationship identification on WeChat, one of the largest social platforms in China. Specifically, we analyze the WeChat red packets network, identify the real-life relationship types between users through mining the semantic information of the amount and sending time of each red packet. In order to better capture the red packet gifting behaviors between users for relationship identification, on one hand, we construct an Amount-Date Graph and apply the graph embedding method to learn embeddings of the amount and sending date of each red packet. On the other hand, we propose a novel sequential model, Cross & Attention Sequence Model (CASM), which explicitly learns the interactions between the latent semantic information of each red packet’s amount and sending date in the red packets sequence between two users. To validate our approach, we conduct comprehensive experiments on a real-world WeChat Users Red Packets dataset that involves 8 kinds of real-life relationships. The experiments show that our proposed approach performs significantly better than baselines and achieves 81.70 percent prediction accuracy. [ABSTRACT FROM AUTHOR]

In renewable energy micro-source applications, a wide range of voltage conversion of the step-up converter is an essential part to equalize the typical low voltage of micro-source with DC-bus voltage of Inverter or motor drives. In order to meet this purpose, an ultra-voltage gain step-up DC-DC converter is proposed in this paper. The proposed converter has made an arrangement of the regenerative-boost fed switched inductor and capacitor configurations. Thereby, due to such an organization of structure, the proposed converter can develop an extremely high voltage-gain even at lower duty ratios. In addition, it has the advantage of lower switching stress across all power semi-conductive diodes. Furthermore, this paper describes the steady-state analysis and comparative features of the converter with existing recent literature. Finally, to validate theoretical analysis and test the feasibility and suitability of the proposed ultra-gain converter, the experimental results were observed by a 500 W fabricated prototype. [ABSTRACT FROM AUTHOR]

Conventional half bridge modular multilevel converter (MMC) system will suffer great over-current when there is a dc side fault. Therefore, topology study in sub-modules with dc side fault blocking capability have become one of the hotspots in MMC field. However, fault blocking topologies using conventional IGBT devices must employ more semiconductors than half bridge topology. The extra semiconductor devices employed in the topology will lead to the increase of cost and conduction loss. To reduce the conduction loss of the fault blocking topology, a novel sub-module topology is proposed in this paper. The proposed topology employs reverse blocking devices to form the low conduction loss path. Conduction loss analysis is conducted in this paper to show the priority of the proposed topology. Simulation and experiment results verified the dc fault blocking capability of the proposed topology. [ABSTRACT FROM AUTHOR]

DC-DC converters are needed for the future development of high voltage direct current (HVDC) grids, as they allow to interconnect lines with different voltages and topologies. The dc-dc converters can increase the grid controllability adding power flow control, voltage regulation and/or fault blocking capability. The dc modular multilevel converter (dc-MMC) is a non-isolated solution proposed to interconnect HVDC systems with the same line topology. This paper proposes a new dc-MMC with a control strategy, which allows the converter to interconnect different line topologies (e.g., rigid bipole connected to a symmetric monopole). The paper presents the different line topologies in HVDC installations. Then, a mathematical model with a variable transformation is proposed for the new dc-dc converter. A control structure is proposed and implemented in Matlab/Simulink using an average arm model and simplified dc grids. The results validate the control in normal operation, fault blocking capability and post-fault scenario (degraded mode). [ABSTRACT FROM AUTHOR]

This paper proposes a cooperative optimal power split (COPS) method for a group of intelligent electric vehicles with battery/supercapacitor hybrid energy storage systems (HESSs). To achieve good performance, the proposed COPS method is made up of the upper and lower layers: the upper layer aims at obtaining the optimal power demand sequence and sending it to the lower layer; the lower layer attempts to optimize the power split for HESS. Firstly, to ensure the performance of the proposed method in practice, the resistance of the battery and supercapacitor packs as well as the DC/DC converter efficiency are not assumed to be constants, but modeled well in the paper. Secondly, to achieve the optimal power demand sequence, an upper power demand sequence optimization problem is formulated based on distributed model predictive control (DMPC), in which energy demand is incorporated into the cost function. Thirdly, after receiving the optimal power demand sequence, a hybrid power split optimization strategy is presented to obtain the optimal power split, in which the lower HESS power split optimization problem is formulated based on DMPC to decrease battery aging process and energy consumption. Finally, an improved particle swarm optimization algorithm with multiple dynamic populations is used to solve the formulated upper and lower optimization problems. Simulation results demonstrate that, compared with the benchmark, the proposed COPS method can significantly extend battery lifespan and slightly decrease energy consumption. [ABSTRACT FROM AUTHOR]

This paper proposes a traction unit that combines an interior permanent magnet motor and a PM-assisted synchronous reluctance motor for electric vehicles to improve traction performance, enhance energy efficiency, and reduce cost. The characteristics of three traction units are analyzed and compared, including (a) rear-wheel-drive configuration using one IPM motor; (b) all-wheel-drive configuration using two interior permanent magnet motors; and (c) all-wheel-drive with a combination of one interior permanent magnet motor and one PM-assisted synchronous reluctance as proposed in this paper. The operational characteristics of each motor to achieve a wide constant power speed range are first investigated. Then, the Urban Dynamometer Driving Schedule is utilized to compare and evaluate the operational characteristics, energy consumption, and most importantly, the efficiency of the traction units. Simulation results reveal that the overall efficiency of the proposed traction unit can be improved compared to the other configurations. The advantages and drawbacks of the proposed traction unit are also investigated. Finally, experiments are conducted to validate the analysis. [ABSTRACT FROM AUTHOR]

A modular multilevel converter control system, based on converter energy storage, is proposed in this paper for two different control modes: active power and dc voltage. The proposed control system decouples the submodule (SM) capacitor voltages from the dc bus voltage. One of the practical applications is the management of active redundant SMs. A practical HVDC system with 401-level MMCs, including 10% redundancy in MMC SMs, is used for validating and demonstrating the advantages of the proposed control system. This paper also presents a novel capacitor voltage balancing control based on \max–\min functions. It is used to drastically reduce the number of switchings for each SM and enhances computational efficiency. [ABSTRACT FROM AUTHOR]

The topology and breakpoints of the grounding grid will directly affect its working performance. This paper proposed a resistivity reconstruction method based on magnetic detection electrical impedance tomography (MDEIT) to measure the topology and breakpoints of the grounding grid. First, this paper describes the forward problem of grounding grid detection in MDEIT, and calculates the magnetic-field distribution above the grounding grid. Then, the resistivity reconstruction method based on the least squares method is proposed. Finally, this paper verifies the feasibility of the proposed method by a numerical example, which shows that the proposed method can be applied to measure the topology and breakpoints of the grounding grid. [ABSTRACT FROM AUTHOR]

This paper presents a new mathematical framework for the economic impact analysis of topology data attacks in electricity markets with virtual bidding activities. The network topology information is very important for system operators to manage the grid in a secure manner. However, this network topology can be manipulated by an adversary through the change of the circuit breaker’s on/off status. This, combined with virtual bids submitted by the attackers, could lead to financial misconduct and potential profit for the attacker in the power market. This paper aims at developing an analytical framework to evaluate the economic profit of an attacker who conducts topology data attack and submits virtual bids accordingly. This framework can be used for system operators as a cybersecurity tool to quickly find the most profitable pair of virtual bidding buses and the most influential transmission line on the change in profit once topology data attack is initiated. Furthermore, the sensitivity of the adversary’s profit with respect to the change in generator’s marginal cost and susceptance for any targeted line is assessed in the proposed framework. IEEE 14-bus system is used to validate and test the proposed framework in various system operation conditions and attack scenarios. [ABSTRACT FROM PUBLISHER]

This paper investigates the robust containment control problem of multiagent systems with heterogeneous uncertainty and nonlinearity while the nonlinear parts have to satisfy the Lipschitz condition. In this paper, both input time-delay and data transmission time-delay between the agents are considered simultaneously and communication topology of the multiagent systems may switch in the steady-state condition. Under the mentioned conditions, the objective of this paper is to make all the followers’ states converge to the convex hull shaped by the leaders’ states with an expected exponential rate. To this end, an appropriate smooth protocol is proposed. Then, a Lyapunov–Krasovskii functional composed of five terms is proposed and the stability condition is denoted by two linear matrix inequalities (LMIs). In addition to the stability assurance, solving the LMIs would obtain the suitable gains for the protocol. Finally, some numerical simulations are given to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

After decades of operations, the first batches of offshore wind farms (OWF) are approaching the end of service lifetimes, while the demand for energy transformation is continuously pushing countries around the globe to construct larger OWFs. Therefore, the old OWF's repowering and scale-expansion becomes a possibly-feasible plan which deserves more researches. This paper firstly analyzes the potential benefits of combining the repowering and expansion parts in collector system topology design, which is followed by further analysis and mathematical verifications of economy and reliability advantages for applying cross-substation incorporation (CSI) to the collector system. To achieve the optimal topology design for OWF repowering and expansion, this paper also proposes a multi-layer optimization framework that consists of an offshore substation (OS) refinement layer, an OWF partition layer, and an intra-zone cable connection layer. The whole optimization concerns the wind turbine (WT) capacity deviation between the repowered part and the expanded part, and the final output is generated with the aim of achieving optimal economy and reliability. The proposed topology is tested and compared with traditional radial and ring topologies on a benchmark collector system, and the results verify the high performance in the economy (both short-term and long-term) and reliability. [ABSTRACT FROM AUTHOR]

Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles (EVs), locomotive traction, ship propulsion, “more-electric” aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various nontraditional purposes. [ABSTRACT FROM AUTHOR]

This paper presents a controlled tying approach for knots using fixtures and simple pulling motions applied to the ends of string. Each fixture is specific to a particular knot; the paper gives a design process that allows a suitable fixture to be designed for an input knot. Knot tying is separated into two phases. In the first phase, a fixture is used to loosely arrange the string around a set of rods, with the required topology of the given knot. In the second phase, the string is pulled taut around the tightening fixtures. Two tightening fixture designs are presented. The first design is a fixture with no moving parts; tilted rods whose cross-sections get closer near the tips, guiding string in a controlled fashion as string slides up the rods during tightening. The second design is a collection of straight rods that can move passively along predefined paths during tightening. Successful tying is shown for three interesting cases: a “cloverleaf knot” design, a “double coin” knot design, and the top of a shoelace knot. [ABSTRACT FROM AUTHOR]

In this paper, we apply a level-set (LS) topological optimization (TO) algorithm to the design of multi-material heatsinks suitable for electronics thermal management. This approach is intended to exploit the potential of metal powder additive manufacturing technologies, which enable the fabrication of complex designs. This paper details the state-of-the-art in TO before defining a numerical framework for optimization of two-material and three-material based heatsink designs. The modeling framework is then applied to design a pure copper and a copper–aluminum heatsink for a simplified electronics cooling scenario and the performance of these designs are compared. The benefits and drawbacks of the implemented approach are discussed, along with enhancements that could be integrated within the framework. A benchmarking study is also detailed, which compares the performance of topologically optimized heatsink against a conventional pin-fin heatsink. This is the first time that TO methods have been assessed for multi-material heatsink design where both conduction and convection are included in the analysis. Hence, the reported paper is novel in its application of a state-of-the-art LS topology optimization algorithm to design multi-material structures subject to forced convective cooling. This paper is intended to demonstrate the applicability of TO to the design of multi-material heatsinks fabricated using additive manufacturing processes and succeeds in this objective. This paper also discusses challenges, which need to be addressed in order to progress this modeling as a design approach for practical engineering situations. The presented methodology is able to design thermal management structures from a combination of aluminum and copper that perform similar to pure copper but utilizing less expensive materials, resulting in a cost-benefit for electronics manufacturers. [ABSTRACT FROM AUTHOR]

Particle swarm optimization (PSO) has two salient components: 1) a dynamical rule governing particle motion and 2) an interparticle communication topology. Recent practice has focused on the fully connected topology (Gbest) despite earlier indications on the superiority of local particle neighborhoods. This paper seeks to address the controversy with empirical trials with canonical PSO on a large benchmark of functions, categorized into 14 properties. This paper confirms the early lore that Gbest is the overall better algorithm for unimodal and separable problems and that a ring neighborhood of connectivity two (Lbest) is the preferred choice for multimodal, nonseparable and composition functions. Topologies of intermediate particle connectivity were also tested and the difference in global/local performance was found to be even more marked. A measure of significant improvement is introduced in order to distinguish major improvements from refinements. Lbest, according to the experiments on the 84 test functions and a bi-modal problem of adjustable severity, is found to have significant improvements later in the run, and to be more diverse at termination. A mobility study shows that Lbest is better able to jump between optimum basins. Indeed Gbest was unable to switch basins in the bi-modal trial. The implication is that Lbest’s larger terminal diversity, its better ability to basin hop and its later significant improvement account for the performance enhancement. In several cases where Lbest was not the better algorithm, the trials show that Lbest was not stuck but would have continued to improve with an extended evaluation budget. Canonical PSO is a baseline algorithm and the ancestor of all contemporary PSO variants. These variants build on the basic structure of baseline PSO and the broad conclusions of this paper are expected to follow through. In particular, research that fails to consider local topologies risks underplaying the success of the promoted algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes a single-phase ac–dc–ac converter composed of a transformer and two three-leg converters connected in series. The proposed converter allows to supply the load with a voltage with constant amplitude and frequency, and to operate with the grid current with low harmonic distortion and high power factor. In addition, the converter can be used to mitigate fundamental overvoltage and voltage harmonics at the grid. The system model, regions of operation, a power flow analysis, and a method to regulate the dc-link voltages using the voltage vector redundancies are given. In the first version of this paper, two pulsewidth modulation (PWM) techniques (including space vector PWM) and a control system were provided. The proposed topology is compared with two conventional systems in terms of operation range, harmonic distortions, and semiconductor losses. Simulation and experimental results are provided to validate the feasibility of the system. [ABSTRACT FROM AUTHOR]

DC microgrid has attracted more and more attention due to its unique characteristics, but the development of a dc microgrid is also facing some challenges, such as interruption and isolation of short-circuit fault currents. Therefore, the dc circuit breaker plays an important role in ensuring the normal work of a dc microgrid. In this paper, a novel bidirectional dc solid-state circuit breaker is proposed to realize the bidirectional flow of energy, which ensures the higher operating efficiency of the dc microgrid. Compared with other solid-state circuit breakers, the proposed novel topology has simpler structure, common ground, and fewer components. First, this paper makes a detailed analysis of the different working stages of the circuit when the fault occurs in combination with simulation results of the circuit topology. Then, the standard of selecting the components through the calculation and analysis of the circuit is given in this paper. Finally, the performance of the novel bidirectional solid-state circuit breaker is verified by experiments. [ABSTRACT FROM AUTHOR]

The development of the dc microgrid system on-board has promoted the development of the dc circuit breaker, but short circuit fault may cause serious damage to the system. Many problems exist in the traditional dc circuit breaker such as long periods of fault interruption, complex circuit structure, existing arc, low reliability, and low anti-interference. Aiming to solve these problems, a novel solid-state dc circuit breaker is proposed in this paper. First, this paper analyzes the working principle and process of the circuit in detail according to the results of the simulation based on Saber. Second, this paper gives the criteria on how to choose the parameters of the components correctly in the circuit. The concept of the maximum fault resistance according to the minimum fault current is also introduced. Moreover, this paper analyzes the influence of the minimum fault ramp rate on the circuit performance. Finally, experimental results verify that the performance of this novel solid-state circuit breaker agree with the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper presents a new bandwidth tuning theory for Butterworth-response resonator filters. The presented theory shows that the bandwidth of odd-order Butterworth filters can be varied by adjusting only two interresonator coupling structures while maintaining a perfect impedance matching at the center frequency. In other words, this paper presents an analytic approach to reduce the number of tunable coupling structures when designing a bandwidth-tunable resonator filter. Theories for third- and fifth-order direct-coupled filters are discussed in detail, and it is shown that only two interresonator coupling structures are required to be tunable. In addition, for verifying the new bandwidth tuning method, a fifth-order cylindrical cavity filter has been designed, fabricated, and measured. The fabricated filter has an 11:1 bandwidth tuning range. [ABSTRACT FROM AUTHOR]

Mobile, wearable, and Internet-of-Things (IOT) electronic systems are typically powered by a single-cell lithium-ion (Li-ion) battery. Increasing demand for battery life and the constraint of the overall platform size impose an emerging desire for an efficient and compact power conversion stage that can directly deliver power from the battery, which ranges from 3.2 to 4.2 V, to the supplies of application/communication processors in the range of 1 V. The switched capacitor (SC) converter, though promising in some ways for this application, is inefficient at voltage regulation and is limited in capacitor utilization. This paper presents a hybrid dc–dc converter topology that eliminates charge sharing losses with a small inductor. The necessary inductance can be realized by PCB traces, which shows the potential for a compact system-in-package (SiP) solution. The designed converter is implemented in Texas Instruments’ 0.15- $\mu \text{m}$ CMOS process with a nominal 3:1 conversion ratio. It supports a 3.2–4.2-V input voltage with a continuous output regulation of 0.8–1.5 V. The peak efficiency is 87.2% with 83.4% efficiency at a power density of 0.46 W/mm2. This paper also presents an effective methodology of developing the large-signal model and small-signal dynamics for the generalized N:1 converter topology. A tight load line-based controller is integrated into the designed chip and experimentally verified with a transient performance of 50-mV voltage overshoot/undershoot under 400-mA on-die load step. [ABSTRACT FROM AUTHOR]

Algebraic topology studies topological spaces with the help of tools from abstract algebra. The main focus of this paper is to show that many concepts from algebraic topology can be conveniently expressed in terms of (normal) factor graphs. As an application, we give an alternative proof of a classical duality result of Kramers and Wannier, which expresses the partition function of the 2-D Ising model at a low temperature in terms of the partition function of the 2-D Ising model at a high temperature. Moreover, we discuss analogous results for the 3-D Ising model and the Potts model. [ABSTRACT FROM AUTHOR]

In this paper, a novel dual-rotor axial-gap flux-switching permanent-magnet machine with dc excitation winding is proposed. First, the topology and operation principles of the proposed topology are clarified. Basic design equations and parameters are provided, and the electromagnetic analyses of the proposed flux-switching machine with 3-D FEA are performed. Parametric optimizations using 3-D FEA are completed for different dc excitations. A prototype machine is manufactured, tested, and validated. It is shown that the air-gap flux of the proposed axial-gap machine can be controlled in a wide range compared to conventional surface magnet machines. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) response predicting is important for defect estimation. This paper first proposes a concept of basic signal by discovering the combination property of the MFL response. The basic signal can be used to predict the MFL response conveniently by a basic signal combination method (BSCM), which is also innovatively put forward in this paper. In this method, the basic signal is calculated in advance, and the MFL response can be calculated by several transformation and combination operations. Both the simulation and experimental results demonstrate the feasibility of BSCM. Compared with other traditional methods (magnetic dipole method and finite-element method), BSCM shows a good performance on both the computational speed and accuracy. [ABSTRACT FROM AUTHOR]

The problem of the leader-following formation control of nonholonomic mobile robots is addressed in this paper. A distributed formation control strategy using explicitly the coordination errors among robots is proposed without assuming that each follower robot knows the full state of the leader. First, a distributed estimation law is proposed for each follower robot to estimate the states, including the position, orientation, and linear velocity of the leader. The distributed formation control law is then designed based on the estimated states of the leader, and the neighborhood formation tracking error. Under some mild assumptions on the interaction graph among the leader and the follower robots, and the velocity of the leader, asymptotic convergence of formation tracking errors to zero can be achieved. Finally, some numerical simulations and experiments on a group of nonholonomic mobile robots are presented to demonstrate the effectiveness of the proposed strategy. Note to Practitioners—The motivation of this paper is to investigate a practical control strategy for the leader-following formation of multiple autonomous mobile robots subjected to nonholonomic constraints. In most of the existing leader-following formation control schemes for nonholonomic mobile robots, having access to the full state of the leader is a requirement. However, due to limitations in communication bandwidth and range, it is reasonable to assume that the information of the leader is available only to a subset of followers. Hence, this paper suggests a new distributed leader-following formation control strategy based on the distributed estimation of the leader’s states. Moreover, the coordination error between a pair of interacting robots is explicitly used in the control design to weaken the dependence on the estimated state of the leader, and enhance the decentralized nature of the proposed control scheme. The stability and convergence of the system are analyzed mathematically and the experiment using unicycles provides promising results. In ongoing research, we are addressing the issues of collision avoidance and communication delays to provide more realistic setup for the industrial applications of multivehicle systems. [ABSTRACT FROM AUTHOR]