Search

In this paper, we present a two-stage model of zonal electricity markets with day-ahead market clearing, and real-time re-dispatch and balancing that accounts for transmission line switching at both stages. We show how the day-ahead problem with switching can be formulated as an adaptive robust optimization problem with mixed integer recourse, and present a new algorithm for solving the adversarial max-min problem that obeys the structure of an interdiction game. We apply the model on a realistic instance of the Central Western European system, and comment on the impacts of both proactive, and reactive transmission switching on the operating costs of the system. Part I presents day-ahead models of a short-term zonal electricity market with switching, and describes our algorithmic approach for solving these models efficiently. Part II describes variants of the real-time model, and presents the results of our case study on the Central Western European market. [ABSTRACT FROM AUTHOR]

This paper is the first to investigate both communication and control in traffic channel (TCH) and control channel (CCH) respectively when considering leader-follower formation keeping in UAV communication networks. In this paper, we analyze the relationship between the mutual interference and information exchange cost, and then formulate the joint channel and link selection problem as a two-way consensus game between CCH and TCH. To characterize the two-way choice of link selection, we creatively propose the generalized two-way consensus equilibrium (GTCE) to capture the stable state. Then, we prove that the formulated game has at least one pure-strategy GTCE which can maximize the UAV communication network utility. A distributed better reply based joint channel and link selection (BRJCLS) algorithm as well as two-dimensional minimum spanning tree (MST) based initialization (TMSTI) algorithm is proposed to achieve the GTCE. Simulation results are presented to show the convergence and effectiveness of the formulated two-way consensus game and proposed algorithms. [ABSTRACT FROM AUTHOR]

Most microgrid protection schemes found in published literature suffer from a lack of generality in that they work well for the assumed topology, including type and placement of sources. Other generic protection schemes tend to be too complicated, too expensive, or both. To overcome these drawbacks, a topology-agnostic, scalable, and cost-aware protection based on fundamental principles that work in the presence of high penetration of inverter-based resources (IBRs) is developed and tested in this paper. The protection system also implements stable automatic reconfiguration of the healthy sections of the system after clearance of fault, thus increasing resilience by self-healing. To achieve this ambitious goal, stable inverter models are developed that operate in unbalanced networks in grid-connected and islanded modes, even with 100% IBRs, share power without conflicting controls, and can ride through faults while limiting fault currents. The scheme is tested for primary and backup protection and reconfiguration on the IEEE 123-node feeder in grid-connected and islanded modes with 15 IBRs connected to the system. [ABSTRACT FROM AUTHOR]

Voltage source converters (VSCs) have been extensively used in power systems for interfacing renewable energies and other modern loads. Because of their nonlinear nature, a proper harmonic model of VSC devices must be established when conducting harmonic analyses in power systems. This is especially true for low-order harmonics, which are routinely encountered in present power systems. To this end, an analytical harmonic model that represents the low-order harmonic characteristics of VSCs is developed in this paper. The new model takes both the control loop and power loop (i.e., DC-link capacitor) of the VSC into account through rigorous mathematical derivations. The final result has shown that the VSC can be represented by a harmonically coupled impedance matrix at harmonic frequencies, which can be easily used for harmonic analyses of large-scale power systems. It also shows that the DC-link capacitor has a more noticeable impact on the harmonic impedance of VSCs with a smaller DC-link capacitance and low-order harmonics. The appropriateness of the new model was verified using EMT simulations and lab experiments. A complete procedure to construct the proposed VSC model is also established based on the research findings. [ABSTRACT FROM AUTHOR]

This paper proposes a sound separation methodology based on deep learning neural network (DLNN) to extract useful diagnostic material in non-invasive audio-based On-Load Tap Changer (OLTC) diagnostics. The proposed methodology has been experimentally verified on both artificial mixtures (created by reproducing the targeted data by the speakers placed next to the active transformers) and actual mixtures (recorded by the microphone during OLTC live operation in the field). The results show that the method produces high-quality estimates (correlation to referent fingerprints $\rho > 0.9$) compared to other sound separation methods, e.g. Independent Component Analysis (ICA). The proposed framework can also perform source separation from a monaural mixture (mixture recorded with a single microphone only), which is impossible for ICA methods. Moreover, the results show that DLNN trained with healthy OLTC data produces diagnostically valuable estimates even when fed with a faulty OLTC audio mixture. For that reason, once trained, the DLNN can produce the diagnostic signal estimates from monaural mixtures that can be used with existing vibration-based diagnostic methods. [ABSTRACT FROM AUTHOR]

Line-commutated converters are extensively used as the interface between ac grids and classic HVDC systems. At the inverter side, commutation failure of switches is one of the most common faults that can pose threats to the system operation. Practical and reliable study of such phenomena relies on accurate and efficient converter models for simulations. Recently, a parametric average-value model (PAVM) has been presented for ac–dc rectifiers, which considers the internal faults of the converter. In this paper, the PAVM methodology is extended to the dc–ac inverter systems, including the commutation failure of switches. The proposed PAVM also augments an automatic fault detection technique to determine the faulty switches. Using comprehensive simulation studies, the developed model is verified to accurately predict the commutation failure of switches and reconstruct the waveforms consistent with the detailed switching models of inverters while being computationally more efficient. The proposed PAVM is envisioned to be an efficient and accurate asset for simulation of HVDC systems and inevitable when faults of switches need to be considered. [ABSTRACT FROM AUTHOR]

This paper studies congestion-aware route-planning policies for intermodal Autonomous Mobility-on-Demand (AMoD) systems, whereby a fleet of autonomous vehicles provides on-demand mobility jointly with public transit under mixed traffic conditions (consisting of AMoD and private vehicles). First, we devise a network flow model to jointly optimize the AMoD routing and rebalancing strategies in a congestion-aware fashion by accounting for the endogenous impact of AMoD flows on travel time. Second, we capture the effect of exogenous traffic stemming from private vehicles adapting to the AMoD flows in a user-centric fashion by leveraging a sequential approach. Since our results are in terms of link flows, we then provide algorithms to retrieve the explicit recommended routes to users. Finally, we showcase our framework with two case-studies considering the transportation sub-networks in Eastern Massachusetts and New York City, respectively. Our results suggest that for high levels of demand, pure AMoD travel can be detrimental due to the additional traffic stemming from its rebalancing flows. However, blending AMoD with public transit, walking and micromobility options can significantly improve the overall system performance by leveraging the high-throughput of public transit combined with the flexibility of walking and micromobility. [ABSTRACT FROM AUTHOR]

This paper provides an adaptive hybrid robust filter (AHRF) for multi-sensor relative navigation systems that can be used to support cooperative intelligent transport systems. It is known that Huber’s M-estimation based robust filter and the fault detection and exclusion (FDE) based RAIM filter each has its own drawbacks, depending on the nature of the observation error biases. Based on the interactive multiple model (IMM) framework, our proposed AHRF in this paper can take advantage of both filters in a complementary sense. A new adaptive IMM (AIMM) algorithm with Markov transition probability prediction is proposed to allow AHRF to switch efficiently between the two filters. We consider the relative navigation system with Global Navigation Satellite System (GNSS) and ultra-wideband (UWB) as observations to verify AHRF in three cases of possible failure modes and multipath-induced errors. Our results show that AHRF outperforms both the FDE and robust filter in all cases. AHRF framework can be further adapted to include many other fault-tolerant filters to improve the robustness of multi-sensor relative navigation system even further. [ABSTRACT FROM AUTHOR]

This paper investigates a platooning problem of connected vehicles subject to communication interruptions and latency. For a heterogeneous platoon of vehicles, a hybrid reference model with cooperative adaptive cruise control (CACC) and adaptive cruise control (ACC) is established. Then a novel CACC-ACC switching control method is suggested, which activates either a CACC scheme or an augmented ACC strategy depending on the status of communications. By introducing a platoon state tracking error system, a control algorithm is derived using finite-time sliding-mode control theory, which can robustly guarantee string stability and zero steady-state spacing error of the vehicular platoon. Simulations have shown the effectiveness and superiority of the method. [ABSTRACT FROM AUTHOR]

Renewable energy is an advisable choice to reduce fuel consumption and $\rm CO_{2}$ emission. Therein, wind energy and solar energy are the most promising contributors to reach this goal. Although the hybrid wind/solar system has been widely studied, the real-time current sharing based on their maximum capacities is rarely achieved in terms of seconds. Based on this, this paper proposes an accurate current sharing and voltage regulation approach in hybrid wind/solar systems, which is based on distributed adaptive dynamic programming approach. Firstly, the equivalent wind/solar model is built, which is an indispensable preprocessing to achieve the complementary between wind energy and solar energy. Therein, the wind energy and solar energy can output relative current according to their respective capacity ratio, which ensure the maximum utilization ratio of renewable energy source. Furthermore, current sharing and voltage regulation problem is switched into optimal control problem. Under this effect, each source agent aims to obtain the optimal control variable and achieve accurate current sharing/voltage regulation. Moreover, an adaptive dynamic programming approach based on Bellman principle is proposed. It can achieve accurate current sharing and voltage regulation. Finally, the simulation results are provided to illustrate the performance of the proposed adaptive dynamic programming approach. [ABSTRACT FROM AUTHOR]

Nature's remarkable and merciful gift to the planet Earth is sunlight which may be highly lucrative if harvested and harnessed properly. Photovoltaic (PV) panels are used to convert the solar energy to electrical energy which are currently used to feed AC loads/grid. In this paper, modelling, performance and power flow studies of grid connected single phase inverter fed from PV array under steady state as well as transient conditions are considered. This paper focuses on the study and development of analytical model of micro-grid integrated single phase five level cascaded H-bridge inverter (MGISPFLCHBPVI) powered by a PV panel. A simple power control strategy for MGISPFLCHBPVI is also considered. The simulations are completely carried out using MATLAB software for power-flow studies. The performance characteristics of the inverter are studied from the analytical model developed. The validation of the analytical model is carried out by comparing the results of simulation in Simulink/Matlab. In order to reduce the time to reach steady state taken by the system, a simple PQ control strategy for insolation is introduced in this paper. The proposed method is evaluated based on performance parameters such as settling time and rising time of the system compared with the results available in the literature. [ABSTRACT FROM AUTHOR]

Miniaturization and low cost contribute to the development and popularization of wireless power transfer (WPT). Reducing the number of power conversion stages can reduce the volume and cost of the WPT converter, and even make it possible to improve the efficiency. A single-stage WPT converter with constant current (CC) and constant voltage (CV) output and its asymmetric modulation method are proposed in this paper. A direct AC-AC converter is applied to the primary side of the WPT converter to directly convert line-frequency AC to high-frequency AC. The applied direct AC-AC converter that can replace the commonly used multi-stage primary converter reduces the number of circuit devices, thereby reducing the volume and cost of primary converter. The proposed WPT converter can realize zero voltage switching (ZVS) and power factor correction (PFC). In order to achieve CC and CV output, a switchable hybrid compensation topology is applied to the proposed WPT converter. A 720-W experimental prototype was manufactured to verify the rationality of the proposed WPT converter and the correctness of the theoretical analysis. [ABSTRACT FROM AUTHOR]

Mixed-criticality (MC) scheduling becomes popular in real-time systems as it supports different criticality levels in a resource-efficient manner. Although it has been well established (i) how to guarantee MC schedulability offline, existing studies have paid less attention to achieve (ii) how to minimize deadline misses of low-criticality tasks at runtime; in addition, it has not matured yet how to address (ii) without compromising (i). In this paper, we propose $\mathsf{MC{-}FLEX}$ MC - FLEX , which employs a task-level mode transition mechanism (as opposed to system-level one). $\mathsf{MC{-}FLEX}$ MC - FLEX not only determines time instants at which each high-criticality task enters and exits the critical mode in a task level, but also selects time instants and target low-criticality task(s) to be dropped and resumed for each task-level mode switch of individual high-criticality tasks, yielding the achievement of both (i) and (ii). Via simulation results, we demonstrate that the proposed framework reduces the job deadline miss ratio of low-criticality tasks at runtime (by over 54.8% compared to the existing work), without compromising offline MC schedulability. [ABSTRACT FROM AUTHOR]

Erasure coding becomes increasingly popular in distributed storage systems (DSSes) for providing high reliability with low storage overhead. However, traditional random data placement induces massive cross-rack traffic and severely imbalanced load during failure recovery, which degrades the recovery performance significantly. In addition, various erasure codes coexisting in a DSS exacerbates the above problems. In this paper, we propose PDL, a PBD-based Data Layout, to optimize failure recovery performance in DSSes. PDL is constructed based on Pairwise Balanced Design, a combinatorial design scheme with uniform mathematical properties, and thus presents a uniform data layout for mixed erasure codes. Then we propose rPDL, a failure recovery scheme based on PDL. rPDL reduces cross-rack traffic effectively and provides nearly balanced cross-rack traffic distribution by uniformly choosing replacement nodes and retrieving determined available blocks to recover the lost blocks. We implemented PDL and rPDL in Hadoop 3.1.1. Compared with the existing data layout and recovery scheme in HDFS, experimental results show that rPDL achieves much higher recovery throughput, $6.27\times$ 6. 27 × on average for single-node failures, $5.14\times$ 5. 14 × for multi-node failures and $1.48\times$ 1. 48 × for single-rack failures, respectively. It also reduces degraded read latency by an average of 62.83 percent, and provides better support to front-end applications in case of component failures. [ABSTRACT FROM AUTHOR]

The rapid development of 6G can help to bring autonomous driving closed to the reality. Drivers and passengers will have more time for work and leisure spending in the vehicles, further generating a lot of data requirements. However, edge resources from small base stations are insufficient to match the wide variety of services of the future vehicular networks. Besides, due to the high-speed nature of the vehicles, users have to switch the connections among different base stations, whereas such way will cause external latency during the data request. Therefore, it is vital to enable the local cache of vehicle users to realize the reliable autonomous driving. In this paper, we consider caching the contents in the local cache, small base station, and edge server. In practice, the request preference of some single users may be different from a whole region. To maximize the efficiency of content cache, we design a strategy that uses reinforcement learning algorithm to optimize cache schemes on different devices. The experimental results demonstrate that our strategy can enhance the cache hit ratio by 10%-20% compared with the well-known counterparts. [ABSTRACT FROM AUTHOR]

This paper proposes a novel data driven framework for detecting topology transitions in a distribution network. The framework analyzes data from phasor measurement units (PMUs) and relies on the fact that changes in network topology results in changes in the structure and admittance of the network. Using voltage and current phasors recorded by PMUs, the proposed method approximates network parameters using an ensemble-based deep learning model and thus, it does not require any knowledge of network parameters and load models. Using the prediction error of the proposed model, a connectivity matrix which shows the status of switches is constructed. In contrast to other methods, this proposed framework does not require a library of voltage and current transients associated with possible network transitions. It can also detect simultaneous switching actions and is robust to noise and load variations. The model yields a lower error detection rate, and its performance is validated using a modified version of the IEEE 33 bus network and a real feeder located in Queensland, Australia, under full and partial observability conditions. The proposed model has also been compared with another data driven method in terms of inference time and error detection rates. [ABSTRACT FROM AUTHOR]

This paper is concerned with the distributed state estimation problem for a class of interconnected dynamic systems, where several binary sensors are deployed to observe each subsystem. The judgement of switching instant for binary sensor is based on the certain estimates and sensed variables. In this case, two innovation sequences which combine thresholds and state estimates are given to extract valid information from binary measurement. Then, a distributed recursive estimator is given on the basis of weighting fusion criteria and bounded recursive optimization. The interconnected gains of state estimator are designed by minimizing the impacts of neighboring terms, while the optimal local gains and weighting fusion matrices are designed by constructing convex optimization problems. Moreover, the asymptotic stability of squared estimation error is proved by means of sequential analysis. Finally, two illustrative examples are employed to show the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

The limitation of theDC protection device confines the development of MV/LVDC grids. This paper presents a DC dynamic voltage restorer to exploit DC custom power devices for DC distribution networks in principle. It is based on an improved AC/DC dual active bridge and battery energy storage to maintain the voltage profile of sensitive loads in DC networks. The principle of the improved DC-DVR has been analyzed from the perspectives of the range of compensated voltage, current characteristics, and control strategy. Compared with other existing methods, the proposed DC-DVR features a simple structure, an easy control strategy, and the ability to mitigate both voltage sag and swell by injecting forward or reverse voltage. Experiment results demonstrate the correctness of the theoretical analysis and the feasibility of the proposed structure. A case study of DC doubly-fed induction generator (DFIG) interfaced with power grid is carried out, integrated with the proposed DC-DVR to verify the operation principle of the proposed scheme. [ABSTRACT FROM AUTHOR]

Fluid antenna system represents an emerging technology that enables an antenna to switch its physical location in a predefined space. This paper explores the potential of using a single fluid antenna at each mobile user for multiple access, which we refer to it as fluid antenna multiple access (FAMA). FAMA exploits spatial moments of deep fade suffered by the interference to achieve a favourable channel condition for the desired signal, without requiring sophisticated signal processing. We analyze the FAMA network by first deriving the outage probability of the signal-to-interference ratio (SIR) in a double integral form. We then obtain an outage probability upper bound in closed form and an average outage rate lower bound for the FAMA system, with an arbitrary number of interferers, from which the multiplexing gain of FAMA is characterized. We also estimate how large the number of locations is required to achieve a given multiplexing gain using fluid antennas with a given size. Results show that it is possible for FAMA to support hundreds of users using only one fluid antenna of a few wavelengths of space at each user, giving rise to significant gain in the average network outage rate. [ABSTRACT FROM AUTHOR]

This paper describes new, simple, recursive methods of construction for orientable sequences, i.e. periodic binary sequences in which any $n$ -tuple occurs at most once in a period in either direction. As has been previously described, such sequences have potential applications in automatic position-location systems, where the sequence is encoded onto a surface and a reader needs only examine $n$ consecutive encoded bits to determine its location and orientation on the surface. The only previously described method of construction (due to Dai et al.) is somewhat complex, whereas the new techniques are simple to both describe and implement. The methods of construction cover both the standard ‘infinite periodic’ case, and also the aperiodic, finite sequence, case. Both the new methods build on the Lempel homomorphism, first introduced as a means of recursively generating de Bruijn sequences. [ABSTRACT FROM AUTHOR]

This paper investigates event-triggered control for saturated switched systems with switching signals subject to dual-terminal denial-of-service (DoS) attacks. The original switching signals are sampled and transmitted to sub-system and sub-controller through networks, respectively. However, the openness of network may cause switching signal transmission to be affected by possible DoS attacks. Moreover, the existing dual-terminal mismatched network delays and attacks could lead to asynchronous phenomenon. Considering the impacts of the attacked switching signals and delays, a time-delay closed-loop switched system is developed. Subsequently, by utilizing piecewise Lyapunov functional technique, various cases caused by DoS attacks and different delays are analyzed. Then, novel conditions are derived to ensure the stability of closed-loop switched system, and sufficient conditions for the desired controller gains and event-triggering parameters are presented. Finally, simulation examples are given to verify the effectiveness of the proposed method. The simulation results show that in the case of single-terminal and dual-terminal attacks, switched systems both have good anti-attack characteristics. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate biocompatible micromachined buckled membranes for the operation in liquids. The membranes feature diameters between 600 and 800 $\mu \text{m}$ as well as integrated piezoelectric thin film actuators, thus enabling switching between the bistable states. The membrane material is known to be not biocompatible, hence a hydrogenated amorphous silicon carbide (a-SiC:H) layer is deposited on the surface. For demonstration purposes, a 70 nm ±3 nm thin a-SiC:H coating with a specific silicon to carbon ratio was chosen, with a negligible impact on the overall switching performance of the bistable membranes. Furthermore, a relation between the membrane center velocity at the first characteristic resonance frequency and the switching ability of a membrane in different viscous fluids is shown. Based on a small signal analysis the switching behavior can be predicted. The membranes were successfully switched in liquids with a dynamic viscosity up to 286 mPa $\cdot \text{s}$. The biocompatibility of the membranes was examined by growing Caco-2 cells, a human carcinoma cell line, on a-SiC:H thin films, featuring different carbon contents and organic surface treatments. The proliferation and adhesion of the cells on the substrates are examined in an empirical cell growth and removal study. Only a-SiC:H surfaces pre-treated with an O2-plasma and coated with Collagen Type I indicated to provide an environment of improved cell adhesiveness compared to other surface treatments. The biological investigations resulted in good cell proliferation, that also depends on the altered hydrophilicity of the surface, as well as on the carbon content of the a-SiC:H thin films. This study reveals that a broad range of biocompatible a-SiC:H surfaces can be prepared, whereby the cell growth can be tailored in terms of proliferation and adhesion for different biomedical application scenarios. Finally, this paper reports on the mechanical features of bistable, buckled membranes and their suitability as a growth substrate for human cell cultures, due to the good biocompatibility of a-SiC:H thin films. We therefore suggest that it will be feasible to grow cells on bistable MEMS membranes, enabling cell experiments in liquid medical environments, with both mechanically excitable and biocompatible surfaces. [2022-0006] [ABSTRACT FROM AUTHOR]

The conventional model predictive power control suffers from heavy computational burden and large power ripple. To address the problem, this paper proposes a simplified three-vector-based model predictive direct power control, which can greatly optimize the control set. Firstly, a switching table is designed to exclude the redundant virtual voltage vectors (VVs). Only half of the candidate VVs are retained. Then, the effect of each VV on power is analyzed in detail. The deviation of reactive power is used as the evidence to further simplify the control set. In this way, the prediction behavior is reduced from 12 to 2, which effectively reduces the computational burden. In addition, the concept of power deadbeat is employed to determine the duty cycles of the two virtual VVs and one zero VV. Thus, the power ripples and current harmonics can be considerably suppressed. With this proposed method, the calculation complexity is reduced, and the steady-state performance is improved. The simulation and experimental results are given to verify the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a finite-control-set model predictive direct torque control (FCS-MPDTC) method is proposed to reduce the torque ripple of a segmented switched reluctance motor (SSRM) at the low-speed stage. Firstly, the prediction dynamic model is established, and the phase torque can be predicted by detecting phase current and rotor position signals. Then, the principle of power converter and selection of voltage vectors are introduced and presented. Considering torque ripple reduction, flux tracking performance and copper losses reduction, the cost function with phase torque, the amplitude of flux linkage and phase current, is established to select optimal voltage vector to control the power converter. In addition, the torque sharing function (TSF) is employed to distribute total torque to phase torque for further torque ripple reduction. Finally, the direct torque control (DTC) is selected as the comparison method, performance of MPDTC is verified by simulation and experiment results. It can be found that the proposed MPDTC can achieve lower torque ripple and copper losses, and high robustness. [ABSTRACT FROM AUTHOR]

In this paper, a circulating-current-excited switched reluctance generator system with the diode rectifier is comparatively studied with a field-current-separated switched reluctance generator. By using a DC power source connected in series with the winding to provide the circulating current, a controllable excitation field is established in the proposed generator. To highlight the influence of this DC voltage source, the injected field current of the field-current-separated generator is kept the same as the circulating current of the circulating-current-excited generator. Then, both advantages and disadvantages of the generators are summarized. The circulating-current-excited switched reluctance generator system inherits both the advantages of good reliability of the separated-winding generator by using the diode rectifier and low copper loss of the integrated-winding machine by combining the AC and DC current in one set of windings. Furthermore, two more practically conventional field-current-separated generators are also compared with the proposed generator in terms of the external characteristics. These two conventional generators have different winding configurations. At last, the analysis is verified by experiments. [ABSTRACT FROM AUTHOR]

The effect of reduction in the terminal voltage of a grid-tied inverter together with minimization in total harmonic distortion (THD) of terminal voltage and current, in the presence of dead-band in the switching remains always challenging for the researchers. With high switching frequency, this issue increases by many folds. The grid-tied inverter used for harmonic compensation acts as a shunt active power filter (SAPF). The implementation of the dead-band elimination technique is based on output current polarity detection, suffers from multiple zero-crossing due to the generation of high frequency switching harmonics during SAPF operation. This paper deals with a dead band elimination methodology together with harmonic compensation using SAPF under non-linear and unbalanced loading conditions. Here, SAPF uses a dual fundamental component extraction (DFCE) scheme with modified complex coefficient filter (MCCF) to extract fundamental components for reference current generation to implement an indirect current control PWM scheme. MCCF extracts fundamental components even in the presence of dc offset and unbalancing at the input. For incorporating dead-band elimination in control, exact polarity detection is done separately through SAPF output current estimation using sensed load current, and modified CCF computed reference source current. Since the estimated SAPF output current contains no high-frequency switching harmonics, the dead-band elimination technique can be correctly implemented. To synchronize the zero-crossing of the estimated and actual SAPF current, an adaptive delay control is used. The proposed MCCF based control logic’s performance together with the dead-band elimination technique is validated for SAPF operating under non-linear, unbalance, and dynamic load conditions. The proposed dead-band elimination scheme based SAPF model is developed and simulated using MATLAB/ SIMULINK. The simulation results show a significant reduction in source current harmonics due to the elimination of odd harmonic injection into the system by incorporating dead-band elimination in SAPF operation. The real-time simulation of the proposed method is also validated using OPAL-RT OP4510 real-time platform. [ABSTRACT FROM AUTHOR]

The missing capability of DC fault current limitation is an inherent disadvantage in the typical half-bridge modular multilevel converter (MMC), which restricts its application in long-distance high voltage direct current (HVDC) systems. The full-bridge submodule (FBSM) and clamped double submodule (CDSM) topologies allow for fault current self-clearing, but also suffer from additional hardware cost and power losses. In this paper, an improved submodule topology utilizing the new reverse-blocking insulated gate bipolar transistor (RB-IGBT) is proposed to improve system economy without compromising its performance. The operating principles and DC fault characteristics of the proposed topology are analyzed in details, including comparison with various topologies in terms of cost, losses, fault current clearing speed and thermal. Compared with the traditional CDSM topology, the proposed RBSM can clear DC faults faster with reduced cost of switching devices. A DC fault protection strategy for MMC-HVDC system is also presented. Simulation results under normal operating, permanent and transient fault conditions are carried out to verify the effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

Malware developers continually attempt to modify the execution pattern of malicious code hiding it inside apparent normal applications, which makes its detection and classification challenging. This article proposes an ensemble detector, which exploits the capabilities of the main analysis algorithms proposed in the literature designed to offer greater resilience to specific evasion techniques. In particular, the article presents different methods to optimally combine both generic and specialized detectors during the analysis process, which can be used to increase the unpredictability of the detection strategy, as well as improve the detection rate in presence of unknown malware families and provide better detection performance in the absence of a constant re-training of detector needed to cope with the evolution of malware. The paper also presents an alpha-count mechanism that explores how the length of the observation time window can affect the detection accuracy and speed of different combinations of detectors during the malware analysis. An extended experimental campaign has been conducted on both an open-source sandbox and an Android smartphone with different malware datasets. A trade-off among performance, training time, and mean-time-to-detect is presented. Finally, a comparison with other ensemble detectors is also presented. [ABSTRACT FROM AUTHOR]

Software-defined networking (SDN) makes network management easier by using a controller to govern all switches, but the controller may become a performance bottleneck. Distributed SDN control is a promising solution, which lets multiple controllers divide the work, where each controller manages a part of the network. Switch migration is one common means to the load balance of controllers, which transfers some switches to different subnets based on the workloads of their controllers. The paper proposes a time-sharing switch migration (TSSM) scheme to provide more refined load sharing for controllers, which allows two controllers to share a switch’s load sequentially in the same period. When a controller is overloaded, TSSM finds assistant controllers to share its workload by selecting proper switches for migration and also deciding the time to perform migration. In this way, the workload of each controller can be kept below a given threshold. We implement the TSSM scheme on the open network operating system (ONOS) to attest to its feasibility. Experimental results show that TSSM can reduce 98% of the occurrences of overload for controllers as compared with the original OpenFlow method. Moreover, TSSM can save about 78% of the migration cost than the churn-triggered migration method. [ABSTRACT FROM AUTHOR]

In modern datacenters, huge energy consumption is a significant problem that remains to be solved. Previous works reduce the system energy consumption by switching the idle servers to a low-power state. However, the workload demands on servers change dynamically and mainly depend on the real-time workload status. To maintain the system energy efficiency, when providing servers with some servers reserved, the status of workloads should be carefully considered. Generally, the status of workloads is characterized by some key factors sampled from the workloads. However, under dynamic workload demands, the accuracy of these sampled values varies. To accurately assess the status of server workloads, in this paper, we propose a Dynamic Time Scale based server Provision (DTSP) method, which takes the variability of workloads into consideration when providing servers for workload demands. To obtain accurate factor values indicating real-time workload, DTSP samples several key workload factors, including the coefficient of variation of arrival intervals, the request arrival rates of current workload and previous workload, and the mean service time of current requests, with a dynamic compatible rate. With these sampled factors, DTSP can accurately estimate the demands of workloads on servers and provide appropriate numbers of servers for the dynamic workloads. Extensive experiments demonstrate that taking the workload variability into consideration, DTSP can significantly promote the energy efficiency of a datacenter. [ABSTRACT FROM AUTHOR]

Aging of power system assets challenges utilities to maintain reliable service while minimizing their maintenance costs. Although malfunction of devices in the transmission or distribution networks can have catastrophic consequences, their failure is seldom unforeseen. Typically, the device aging occurs gradually over time until its health condition reaches a point of complete breakdown. The overall objective of this paper is to devise a non-invasive, online condition monitoring technique of circuit switchers for shunt capacitor banks. It aims to detect abnormal operation of these devices based on features derived from raw voltage and current waveforms, such that a predictive maintenance strategy may be employed before a complete failure occurs. The data analyzed in this paper are collected at a transmission capacitor bus, where the banks are equipped with pre-insertion impedance. Through a baseline range of values for selected parameters, the proposed technique is able to detect missing pre-insertion impedance during the capacitor energizing and failure of pre-insertion impedance switch out a few cycles after the energizing operation. [ABSTRACT FROM AUTHOR]

Ferroelectric (FE) materials are being studied for a variety of applications in memory, logic, and neuromorphic computing, for which predictive models of FE polarization are essential. In this paper, we present a Monte Carlo simulation framework capable of predicting the dynamic, history-dependent response of an FE under arbitrary input waveforms. The simulation is developed by generalizing the physics-based nucleation-limited switching model for polarization reversal in a polycrystalline FE. Measured polarization reversal data from fabricated FE Hf0.5Zr0.5O2 capacitors are used to extract the statistical distribution of FE grains. After parameter extraction, the model is able to predict the dynamics of the FE capacitor without further calibration. Finally, the model is applied to characterize the dynamic response of FE–dielectric bilayer structures and quantify the reduction in memory window due to device variability. [ABSTRACT FROM AUTHOR]

In this paper, an indirect herding problem is considered for a single herder that is outnumbered by multiple target agents. Indirect herding is a problem that involves a network of one or more controllable herding agents and indirectly controlled target agents (i.e., the target agents can only be controlled through the herder by exploiting herder–target interactions), where the goal is to achieve a network-wide objective. This paper investigates the unique problem where a single herder is required to regulate all the target agents to some desired formation. The problem is further complicated by the fact that the target agents have uncertain nonlinear dynamics, including uncertainties in the herder–target interaction. Neural network function approximation methods are used along with switched systems methods to ensure uniformly ultimately bounded convergence of the agent trajectories provided the developed sufficient dwell-time conditions are satisfied. Simulation and experimental results that involve one herding agent and multiple target agents demonstrate the validity of the designed controller and function approximation scheme for multiple herding objectives. [ABSTRACT FROM AUTHOR]

This paper describes Ka-band inductor-shared RF switches and their applications to a 35.2-ps 6-bit true-time-delay (TTD) switched-line (SL) phase shifter (PS). The inductor-shared RF switches share an inductor to match the input and output (I/O) ports of different states, which are realized with a switched inductor for SP ${n}\text{T}$ case and with a shared matching network for DP ${n}\text{T}$ case. The switches are applied to controlling most significant 3 bits of the proposed TTD SL PS. The delay lines and reference lines of the PS are implemented with microstrip lines and inverted microstrip lines in the same space, respectively. The dual-side microstrip lines allow it to have not only a small size but also compensation of the loss difference between the signal lines with different lengths. The least significant 3 bits are implemented with the modified structure of the SL PS, which reduces the size further by replacing a reference line by a series switch. The test chip is fabricated in a 65-nm CMOS process. It operates in the range of 20–30 GHz occupying a 0.18 mm2 core size. Its measured insertion loss and IP1dB are 11 dB and 6.5 dBm at 28 GHz, respectively. The measured gain error and rms delay error are less than 2 dB and 0.7 ps at operation frequencies. [ABSTRACT FROM AUTHOR]

With the reduction of wafer batch size on account of the diversification and individuation of consumption demands, increasing importance has been attached to the schedulability and controllability of the cluster tools with multiple wafer types being concurrently processed, while the corresponding research is seldom and still open. This paper is devoted to addressing the steady-state scheduling of single-arm cluster tools with multiple wafer types and residency time constraints. Inspired by the definition of wafer flow pattern for the single wafer type, a novel description for the multiple wafer types is introduced. For the sake of efficiency and simplicity, the multiplex backward sequence is proposed. To balance the workload of process steps, a virtual module technology with a two-tiered architecture is implemented. Furthermore, several sufficient and necessary conditions are derived to verify the schedulability of the system. Finally, an efficient algorithm is presented to find the periodic steady-state schedule, and its practicability and availability are validated by the given illustrative examples. Note to Practitioners—Cluster tools are a kind of highly automated, flexible, and integrated equipment applied widely in diversified semiconductor fabrication processes. Due to the strictness of processing constraints and unavailability of in-built buffers, it is challenging to effectively operate cluster tools. For a higher utilization of processing modules, fabs tend to concurrently process several kinds of wafers with dissimilar recipes in a cluster tool. However, the related scheduling and control problems remain open. With residency time constraints, this paper addresses the scheduling problems of single-arm cluster tools with multiple wafer types. By dissecting the mechanism of mixed-processing of multiple wafer types, several formal conditions are obtained to test the schedulability. Based on the multiplex backward sequence, a cyclic scheduling approach to single-arm cluster tools with multiple wafer types is presented. With the proposed method, schedulability conditions can be readily checked and a periodic schedule can be found easily. Thus, it can be applied to solve practical application problems. [ABSTRACT FROM AUTHOR]

Battery systems are inherently networked systems, in which battery cells or packs are grouped by serial and parallel connections to meet power and capacity specifications. In real-time operation, battery packs must be controlled collaboratively so that their capacities can be fully utilized. By employing both analog charge/discharge currents and discrete-event bypass switches in networked battery systems, this paper develops a new hybrid control methodology to control the states of charge (SOCs) and optimize performance. The paper first establishes necessary and sufficient conditions for controllability under hybrid control mechanism. These conditions are then used to derive control strategies to achieve coordinated SOC control, state consensus, and performance optimization. Control algorithms are developed, their convergence properties proved, and optimality established. Simulation examples are used to demonstrate the methods and their performances using a production battery system. [ABSTRACT FROM AUTHOR]

This paper presents two high-voltage direct-current circuit breakers that have the capability of interrupting a short-circuit current within several milliseconds. They consist of a current-limit inductor, a current-control inductor, one or two mechanical switches, and a multilevel converter with phase-shifted-carrier pulsewidth modulation. The two breakers can commutate an almost zero current from the main branch to the auxiliary branch. This paper proposes an original breaker with low-voltage and high-voltage mechanical switches connected in series, followed by a simplified breaker with a single high-voltage mechanical switch. Finally, this paper includes experimental verification by two slightly different downscaled breakers rated at 300 Vdc and 150 Adc, as well as confirmation of an actual original breaker by circuit simulation using the “PSCAD/EMTDC” software package. [ABSTRACT FROM AUTHOR]

In this paper, an improved 4H-SiC U-shaped trench-gate metal–oxide–semiconductor field-effect transistors (UMOSFETs) structure with low ON-resistance (${R}_{ \mathrm{\scriptscriptstyle ON}}$) and switching energy loss is proposed. The novel structure features an added n-type region, which reduces ON-resistance of the device significantly while maintaining the breakdown voltage (${V}_{\textsf {BR}}$). In addition, the gate of the improved structure is designed as a p-n junction to reduce the switching energy loss. Simulations by Sentaurus TCAD are carried out to reveal the working mechanism of this improved structure. For the static performance, the ON-resistance and the figure of merit (FOM $= {V}_{\textsf {BR}}^{\textsf {2}}/{R}_{ \mathrm{\scriptscriptstyle ON}}$) of the optimized structure are improved by 40% and 44%, respectively, as compared to a conventional trench MOSFET without the added n-type region and modified gate. For the dynamic performance, the turn-on time (${T}_{ \mathrm{\scriptscriptstyle ON}}$) and turn-off time (${T}_{ \mathrm{\scriptscriptstyle OFF}}$) of the proposed structure are both shorter than that of the conventional structure, bringing a 43% and 30% reduction in turn-on energy loss and total switching energy loss (${E}_{\mathbf {SW}}$). [ABSTRACT FROM AUTHOR]

The instability of the switching frequency in an inverter with hysteresis current results in a high failure rate of the power switching components of the inverter. To address this hurdle, a low-cost fault-tolerant control strategy is proposed in this paper to effectively correct the faults. [ABSTRACT FROM AUTHOR]

In this paper, a modular topology is presented for generating high-voltage pulsed power. The proposed structure consists of Marx-type modules, which are based on the switched-capacitor (SC) concept. This module receives an input voltage and, depending on the requirement of the user, produces an output voltage either equal to the input or twice as much as the input voltage, which shows the flexibility of our model. The capability of the module to produce a doubled output makes it appropriate for applications with low input voltage sources. Also, the topology has the capability of generating combined wide and narrow pulses. The topology was simulated in MATLAB Simulink and a laboratory setup was built to test its operation. The results validate the theoretical basis of the structure. [ABSTRACT FROM AUTHOR]

This paper analyzes the effects of shunt capacitors installed on the low voltage sides of 10/0.4 kV distribution transformers on the operation of these transformers. Using the results of an extensive measurement campaign, this paper compares: real and reactive power losses, secondary-side current, and primary-side apparent power before and after the installation of transformer capacitors. The following four cases of reactive power compensation are considered and discussed: adequate, conditionally adequate, and total compensation, as well as overcompensation. The presented analysis helps to identify transformer substations where the initial compensation should be changed or adjusted, in order to improve transformers’ operational performance. Voltage dependencies of real and reactive power demands of the transformer-supplied loads are taken into account, based on the previously identified load characteristics in the considered networks as well as voltage dependence of reactive power of shunt capacitors. The result with and without including these voltage dependencies in the analysis is compared and discussed. [ABSTRACT FROM AUTHOR]

Ferroelectric and negative-capacitance field-effect transistors (FeFETs and NCFETs) have recently garnered great attention as devices for applications in memory and low-power logic, respectively. As these technologies are pursued, it is critical to have a variety of measurement approaches, including methods familiar to the electron-device and microwave communities that can aid in fully understanding the behavior of ferroelectrics in FeFETs and NCFETs. In this paper, we propose and show the viability of using frequency-domain electrical measurement techniques employing the well-known microwave S-parameters, and their large-signal generalization and X-parameters. Our methods provide the means to trace the intrinsic polarization versus electric-field curve of the ferroelectric, i.e., with the parasitics de-embedded, thereby showing the innate ferroelectric response, which cannot be done using conventional techniques. These methods also enable extraction of all the parameters of the Landau–Khalatnikov equation, which is commonly used to model ferroelectric behavior in FeFETs and NCFETs. This paper hence takes a useful step toward methods familiar to the electron-device community that can help to better understand and optimize FeFET and NCFET technologies. [ABSTRACT FROM AUTHOR]

This paper investigates the integral sliding mode control problem of T–S fuzzy interconnected descriptor system based on a reduced-order compensator. A canonical equivalent form for T–S fuzzy interconnected descriptor system is first introduced to facilitate the reduced-order compensator design. In terms of the measurable output variables of the T–S fuzzy interconnected descriptor system and the state variables of the proposed reduced-order compensator, an integral sliding mode control scheme is then developed for the T–S fuzzy interconnected descriptor system. The sliding motion is defined in the augmented space formed by the state variables of the original T–S fuzzy interconnected descriptor system and the resulting error system. It is shown that the designing parameters in the switching function can be simultaneously solved and the original T–S fuzzy interconnected descriptor system has no requirement to be relative degree one. Since the estimate error is bounded by an auxiliary dynamical system, when ideal sliding mode occurs, the resulting closed-loop system is asymptotically stable rather than uniformly ultimately bounded. Finally, a double-inverted pendulum system and a ball and beam system are numerically simulated to demonstrate the effectiveness and merits of the method proposed. [ABSTRACT FROM AUTHOR]

The planned China fusion engineering test reactor (CFETR) needs one or more negative-ion-based neutral beam injectors (N-NBIs) with a beam energy of 500 or even 1000 keV. In order to prepare for CFETR, a prototype of CFETR N-NBI is being designed. The prototype needs an acceleration grid power supply (AGPS) rated at 200 kV/25 A with a maximum pulselength reaches to 3600 s. The AGPS adopted a single-stage inverter-type high-voltage power supply (HVPS). The output voltage ripple is an important specification of the AGPS, which can affect the efficiency and stability of N-NBI system by influencing the beam divergence. However, the conventional methods cannot be used to limit the output voltage ripple of the inverter-type HVPS used as AGPS of CFETR N-NBI prototype. This paper simplified the AGPS to an insulated three-phase three-level (TPTL) dc–dc converter connected with a dual dc link. The working process of the TPTL dc–dc converter with duty-cycle modulation has been analyzed, and two main continuous conduction modes are described. The influence of key parameters such as duty cycle of inverter, leakage inductance of transformer, and output current on output voltage ripple is analyzed. Based on the analysis results, a so-called combined control strategy was proposed to keep the output voltage ripple at a level. The proposed strategy is suitable for the cases where the object output voltage is below 175 kV. Some simulations were carried out by using MATLAB/Simulink. The results showed that the analysis in this paper is reliable and the proposed control strategy has a good performance. [ABSTRACT FROM AUTHOR]

Small-cell architecture is widely adopted by cellular network operators to increase spectral spatial efficiency. However, this approach suffers from low spectrum temporal efficiency. When a cell becomes smaller and covers fewer users, its total traffic fluctuates significantly due to insufficient traffic aggregation and exhibits a large “peak-to-mean” ratio. As operators customarily provision spectrum for peak traffic, large traffic temporal fluctuation inevitably leads to low spectrum temporal efficiency. To address this issue, in this paper, we advocate device-to-device (D2D) load-balancing as a useful mechanism. The idea is to shift traffic from a congested cell to its adjacent under-utilized cells by leveraging inter-cell D2D communication, so that the traffic can be served without using extra spectrum, effectively improving the spectrum temporal efficiency. We provide theoretical modeling and analysis to characterize the benefit of D2D load balancing, in terms of total spectrum requirements and the corresponding cost, in terms of incurred D2D traffic overhead. We carry out empirical evaluations based on real-world 4G data traces and show that D2D load balancing can reduce the spectrum requirement by 25% as compared to the standard scenario without D2D load balancing, at the expense of negligible 0.7% D2D traffic overhead. [ABSTRACT FROM AUTHOR]

This paper investigates the issues of oxygen accumulation and variation in the high-resistance state of HfO2-based resistive random access memory (RRAM), with improvement attained by inserting a thin oxygen-vacancy-rich layer of indium-tin-oxide (ITO) film. By acting as the oxygen ion reservoir, this ITO thin film on the TiN electrode can further stabilize resistance switching (RS) characteristics. In terms of reliability, ac endurance, and retention tests confirm stable RS characteristics for the Pt/HfO2/ITO/TiN device. Finally, a conducting model was proposed to explain the influence of the ITO thin layer and clarify the physical mechanism of electrical improvements. [ABSTRACT FROM AUTHOR]

This paper presents a Li-ion-compatible fully integrated hybrid dc–dc converter implemented in 28-nm FDSOI. A modified four-level converter is proposed to achieve high efficiency while operating from the 2.8–4.2-V Li-ion battery range by using stacked 1.5-V transistors. In this paper, the proposed driver architecture exploits the internal nodes of the power stage as power/GND rails for drivers, eliminating the need for dedicated power rails, level shifters, or stacked drivers. The proposed converter operates in the discontinuous conduction mode (DCM) and regulates the output with constant ON-time pulse-frequency modulation (PFM), to achieve high efficiency across low load range suitable for wearable/Internet of Things (IoT) applications. The fabricated chip regulates a 0.6–1.2-V output from a 2.8–4.2-V input voltage over an output power range from $10~\mu \textrm {W}$ to 40 mW with 78% peak efficiency, and switching frequency up to 200 MHz. The converter occupies $1.5~\textrm {mm}^{2}$ of on-die area including a pair of 5-nF flying capacitors and a 3-nH inductor. [ABSTRACT FROM AUTHOR]

The abnormal rise in contact temperature in switchgear may lead to overheating or even explosion. It is necessary to monitor the rise in real contact temperature to ensure the safety and stability of switchgear. The accurate measurement of real contact temperature is still a problem, and the continuous state of switchgear cannot be assessed accurately by the temperature monitor. In this paper, a particular installation scheme of temperature sensor is put forward and a calculation algorithm for temperature rise of tulip contacts by the measured temperature of bus bar in real time based on artificial neural network (ANN) is established. An electromagnetic-thermal-fluid coupled simulation model for 10-kV/4000-A switchgears was built, and the thermal characteristic was studied taking the influential factors such as load current, ambient temperature, and contact resistance into consideration. The effectiveness of simulation model is discussed by the comparison to temperature rise experiment. Then, an ANN with three layers of structure is established to calculate the temperature of tulip contacts. The sensitivity and accuracy of network are calculated and verified. The results of this paper may provide a novel method for the monitor of switchgear temperature and assess continuous condition of high-current switchgear. [ABSTRACT FROM AUTHOR]

Robust optimization over time is a new way to tackle dynamic optimization problems where the goal is to find solutions that remain acceptable over an extended period of time. The state-of-the-art methods in this domain try to identify robust solutions based on their future predicted fitness values. However, predicting future fitness values is difficult and error prone. In this paper, we propose a new framework based on a multipopulation method in which subpopulations are responsible for tracking peaks and also gathering characteristic information about them. When the quality of the current robust solution falls below the acceptance threshold, the algorithm chooses the next robust solution based on the collected information. We propose four different strategies to select the next solution. The experimental results on benchmark problems show that our newly proposed methods perform significantly better than existing algorithms. [ABSTRACT FROM AUTHOR]

This paper introduces an averaging control strategy of the phase-unit losses of modular multilevel converters (MMCs). The quantitative analysis of the MMC phase-unit loss distribution under unbalanced ac conditions is carried out by investigating the individual component of the MMC arm currents. It shows that the unbalanced arm currents will result in unbalanced phase-unit losses. To address this issue, this paper proposes a predictive closed-loop-control-based zero-sequence voltage injection method that results in much averaged loss distribution under unbalanced ac conditions. The essence of the new method is that it adjusts the three-phase sinusoidal references so that the unbalanced arm currents are fully utilized to average phase-unit losses. This paper shows the effectiveness of the new approach by electromagnetic transient simulations on PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]