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The challenges of conventional semiconducting electronics, such as dark silicon, memory wall, and stagnant clock frequency motivate the search for alternative computing technologies. Superconductive electronics (SCE) represents one of the most advanced beyond-CMOS technologies, with the potential of revolutionizing high-performance computing. In this review, the advancements of SCE over the past 25 years are presented. Novel logic families, circuit design techniques, and electronic design automation tools for SCE circuits are described. Eventually, future advancements in SCE are discussed from circuit and system design perspective. [ABSTRACT FROM AUTHOR]

This paper presents a novel survey of high level synthesis (HLS) based hardware security approaches for reusable intellectual property (IP) cores used in consumer electronics and computing systems. A succinct review of all major HLS based hardware security approaches applied on reusable IP cores, along with their design flow and security analysis, is provided. The paper presents a detailed design flow of hardware integrated circuits (ICs) along with vulnerability points where potential attacks/threats are possible. Trustworthy and untrustworthy regimes in the design flow have also been highlighted in the discussion. Further, a discussion of detective and preventive control-based HLS hardware security approaches used for hardware IP cores has also been presented, including an analysis of prominent structural obfuscation, logic locking (logic encryption), and IP core protection (IPP) techniques. Each approach has been lucidly explained in terms of its threat model, algorithm, and security analysis. Finally, a security comparison of hardware IP obfuscation approaches in terms of strength of obfuscation security metric as well as a security comparison of IPP approaches in terms of probability of coincidence security metric, have also been introduced. [ABSTRACT FROM AUTHOR]

In this article, an L-shaped double gate bipolar impact ionization MOSFET (L-DG BIMOS) is proposed and demonstrated as an ultra-low energy artificial leaky integrate and fire (LIF) neuron for spiking neural network. The L-shaped double gate structure offers a higher rate of impact ionization (II) essential for triggering LIF action and hence can efficiently be applicable to mimic a biological neuron. Using a well-calibrated 2D TCAD tool, the functioning of the proposed device as an LIF neuron is manifested by exhibiting a low threshold voltage of 0.2 V to fire a spike, reduced breakdown voltage of 0.68 V and 0.1050 pJ of energy per spike, making the device more energy efficient as compared to conventional neurons. In addition, the spiking frequency of L-DG BIMOS is calculated to be in the gigahertz (Gz) range when the drain is biased at 1.5 V, which is much higher than biological neurons. [ABSTRACT FROM AUTHOR]

Cryogenic semiconductor device models are essential in designing control systems for quantum devices and in benchmarking the benefits of cryogenic cooling for high-performance computing. In particular, the saturation of subthreshold swing due to band tails is an important phenomenon to include in low-temperature analytical MOSFET models as it predicts theoretical lower bounds on the leakage power and supply voltage in tailored cryogenic CMOS technologies with tuned threshold voltages. Previous physics-based modeling required to evaluate functions with no closed-form solutions, defeating the purpose of fast and efficient model evaluation. Thus far, only the empirically proposed expressions are in closed form. This article bridges this gap by deriving a physics-based and closed-form model for the full saturating trend of the subthreshold swing from room down to low temperature. The proposed model is compared against experimental data taken on some long and short devices from a commercial 28-nm bulk CMOS technology down to 4.2 K. [ABSTRACT FROM AUTHOR]

The potential for nanoscale devices to serve as a platform for the detection of biomolecules is immense. Several challenges have been faced in the device fabrication process. To address these issues, the uniformly doped concept was introduced. This study suggests the use of a vertical tunnel field-effect (VTFET) transistor with a pH base and a gate overlap dielectric modulation for label-free electrical recognition of biomolecules such as cells, deoxyribonucleic acids, proteins, enzymes, and others. In the present article, two simple approaches of sensitivity analysis are compared, the first one is the dielectric modulated analysis and the second one is the electrolytic-based pH sensing of vertical TFET biosensor. The proposed model incorporates the effects of pH and the dielectric constant to provide a generalised solution applicable to neutral biomolecules. To test the effectiveness of the proposed sensors, a thorough simulation is run using an ATLAS device simulator. The effects of pH changes on device characteristics like the device current (IDS) and surface potential sensitivity are investigated. Additionally, pH sensors measure changes in hydrogen ion concentration in aqueous solutions and shifts in drain current caused by changes in the dielectric constant that have been used to analyse the sensitivity of dielectric modulated biosensors. The drain current sensitivity of the pH-hetero-VTFET biosensor is estimated as 8.8 × 105 which is higher than the sensitivity (9.1 × 104) of DM-hetero-VTFET at the cavity length of 30 nm. Since it has been found that the proposed sensor exhibits significant variations in its surface potential and drain current (ION), so this device is preferable as an appropriate sensing transducer. [ABSTRACT FROM AUTHOR]

In this work, for the first time, we have investigated an analytical model for β-MIS-(AlGa)2O3/Ga2O3 ion-sensitive FET by using commercial Silvaco and MATLAB tools for non-ideality behavior around the isoelectric point. Gouy-Chapman-Stern theory is used to analyze the electrical double layer with the electrolyte. Al2O3 is used as a dielectric between (AlGa)2O3 and electrolyte. The pH sensor detects the variation in hydrogen ion concentration in the aqueous solution. Different electrolyte concentrations (1 mM, 0.01 M, 0.1 M) are used in aqueous solution to find sensitive parameters such as surface potential, charge density, Alpha, βint, Cdiff and CDL for different pH values. Changes in surface potential and other sensitive parameters affect the intensity of 2DEG at the interface of (AlGa)2O3 and Ga2O3 in β-MIS-(AlGa)2O3/Ga2O3 HEMT. The behavior of pH- sensitive parameters are also discussed before and after the isoelectric point. Variation in electrolyte concentration shows that lower electrolyte concentration has high sensitivity. Effects of variation of pH on potential, H+ and OH− concentration with bulk distance have also been discussed. Transfer characteristics, threshold voltage, ION/IOFF of β-MIS-(AlGa)2O3/Ga2O3 HEMT have been investigated for different pH values. Threshold voltage increases with pH when pH moves from acidic to basic medium. [ABSTRACT FROM AUTHOR]

We present a resistance switching device that exhibits analogue potentiation and depression of conductance under the same voltage polarity. This contrasts with previously studied devices that potentiate and depress under opposite polarities. We refer to this mode of operation as the subthreshold regime due to it occurring at voltage or current biases that are insufficient to produce discrete or non-volatile switching. This behaviour has the potential to reduce the complexity of neuronal and synaptic circuitry in neuromorphic computing by removing the need for voltage pulses of both positive and negative polarities. The characteristically long timescales may also help replicate bio-realistic timings. In this article, we detail how to induce this unique behaviour, how to tune its properties to a desired response, and finally, we demonstrate one potential application. [ABSTRACT FROM AUTHOR]

The electrostatics of two-dimensional (2D) lateral pn homojunctions considering the impact of electrostatic doping by means of two split bottom-gates are studied here. Analytical expressions are obtained from the solution of the 2D Poisson equation considering a depletion approximation. Straightforward analytical models for the electrostatic potential and the depletion width within both the dielectric and the 2D semiconductor are obtained for both the symmetrical and asymmetrical cases. In contrast to the case of devices with chemical doping, the obtained depletion width model of devices with electrostatic doping do not depend on the dielectric constant but only on the electrostatic potential and oxide thickness. The models describe the electrostatics of gate-tunable 2D pn junctions at arbitrary bias. A benchmark against numerical device simulations of MoS $_{2}$ -based pn junctions validate the analytical models. [ABSTRACT FROM AUTHOR]

In this study, an enzymatic ascorbate oxidase/(AO) ruthenium dioxide (RuO2) ascorbic acid (AA) biosensor was realized by a radio frequency (RF) sputtering system. The characteristics of the RuO2 sensing membrane were analyzed by field-emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Moreover, electrochemical impedance spectroscopy (EIS) was performed to show that a higher concentration of AA caused a larger capacitance of the RuO2 membrane. Therefore, more charges can be accumulated on the sensing membrane. To read out the AA sensing signals, an instrumentation amplifier (IA) integrated with an analog-to-digital converter (ADC) was utilized to substitute the traditional data acquisition (DAQ) device. Then, the analog signals were converted into binary codes and transmitted to the computer, and the binary codes were multiplied by the weighting and converted to decimal codes. Hence, the average sensitivity and the linearity were obtained which were 58.22 mV/decade and 0.991, respectively. The hysteresis effects of the AO/RuO2 AA biosensor were also discussed. The hysteresis voltages in forward and reverse cycles were 3.77 mV and 4.59 mV, respectively. [ABSTRACT FROM AUTHOR]

Capacitor voltage balancing is a critical issue for neutral-point-clamped-based converters, including the two/three-level dual-active-bridge dc–dc converters. The unbalanced capacitor voltage will increase the voltage stress on power devices and negatively affect the reliability of the converters. Two typical problems during the capacitor voltage balancing process should be solved, i.e., power fluctuation minimization and determination of the transformer current polarity. Accordingly, this article proposes a balancing control scheme based on the complementary switching-state (CSS) method. In the CSS method, the switching states, which are identified to be adverse for balancing, will be replaced by their corresponding CSSs to control the neutral-point current while keeping the voltage and current waveforms unchanged. By doing so, the power fluctuation and current overshoot during the balancing process can be significantly reduced. Moreover, since the dynamic voltage and current waveforms are identical to the steady-state waveforms, the transformer current polarity during the balancing process can be identified based on the steady-state power and current models. Therefore, the determination of the transformer current polarity can be simplified compared to the traditional balancing control scheme. Finally, experimental results are carried out to verify the performance of the proposed balancing control scheme. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) has achieved its popularity in wide range of voltage applications over other multilevel topologies due to its modularity, scalability, and ease of design. A typical MMC is composed of many capacitors and the voltages across them are required to be measured for the control of system variables like the circulating current and for capacitor voltage balancing. The number of capacitors and their associated measurement devices increase with higher voltage levels. Hence, to reduce the economical and design burden, several techniques for the observation of capacitor voltages have been presented till date. In this article, capacitor voltages of the submodules are observed using a simple Lyapunov-based observer (LBO) and the convergence proof of the observation error is established mathematically. The performance of the proposed LBO is studied in simulation using MATLAB/Simulink and also experimentally validated. The proposed observer is also compared in simulation with two other existing observation techniques from literature. [ABSTRACT FROM AUTHOR]

Low-speed drive is one of the challenges for modular multilevel converters (MMCs) due to large capacitor voltage fluctuation. In this article, a cascaded MMC and cycloconverter (CCV) based machine drive system is proposed to ensure stable operation of medium-voltage and low-speed machine. The MMC provides medium-frequency ac voltage for the CCV, and the CCV converts the medium-frequency ac input to low-frequency ac output required by the machine. Detailed analysis about MMC's operation frequency, device current stress, and submodule (SM) capacitance are given in this article. Proposed drive system can operate at zero/low frequency under rated load torque, while the SM capacitance is much smaller than that in existing methods. Simulation and experimental studies are conducted, and the results verify the effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

The switched-capacitor of boost seven-level active neutral-point-clamped inverter has the large voltage ripple due to its inherent long discharging interval. Aiming at reducing the switched-capacitor voltage ripple and subsequently the capacitance, this article proposes a flexible third harmonic voltage modulation method. In specific, the long discharging interval can be divided into short intervals or even avoided by flexibly regulating the amplitude and phase-angle of third harmonic voltage based on various modulation indexes and power factors. An offline particle swarm optimization algorithm is employed to find the corresponding optimal amplitude and phase-angle of third harmonic voltage, which will further be put into the online look-up table to simplify the real time implementation. Experimental results verified the performance of the proposed modulation method. [ABSTRACT FROM AUTHOR]

Online aging monitoring is the basis for high reliability operation of Insulated gate bipolar transistors (IGBTs). Most monitoring methods focus on the package-related aging. Leakage current (Ileak) has been proposed as a potential chip-related aging (CRA) indicator for IGBTs. However, this method has not been implemented online due to the difficulty in accurate online leakage current measurement. An effective online CRA monitoring method is still required for IGBTs. A novel online CRA monitoring method based on Ileak for IGBTs is proposed in this article. First, an online Ileak measurement circuit is proposed. Second, based on this circuit, an aging monitoring strategy is presented. Finally, accelerating aging tests validate the effectiveness of the proposed method. The on-state voltage drop is selected as an aging indicator for comparison. The proposed method has three advantages. The online CRA monitoring is achieved. It can be used in slight aging situation with high sensitivity because Ileak is linear to the CRA levels. The measurement circuit required by this method is simple and low-cost. [ABSTRACT FROM AUTHOR]

Unbalanced ac voltages drastically deteriorate the performance of five-level flying capacitor (FC) rectifiers. Without introducing an extra buffering circuit to absorb the second-order oscillating power, it is an incompatible contradiction for realizing both negative-sequence current reduction and second-order voltage ripple suppression. In this article, based on the idea of using FCs in the rectifier to absorb the oscillating power, a second-order voltage ripple suppression strategy for unbalanced ac voltage conditions is proposed. Reducing the negative-sequence currents and suppressing the dc voltage ripples can be simultaneously realized. Simulations and experimental results verified the effectiveness and performance of the proposed scheme well. [ABSTRACT FROM AUTHOR]

Inspired by an electromagnetic generator containing multi-pole radial ring magnets, we designed a bipolar electret rotatory power generator (e-RPG) with a multi-phase core-shell structure to boost output performance and achieve high-precision self-sensing capabilities. A selectively localized rotary corona discharging method is invented to uniformly inject both positive and negative charges into a single electret’s curved surface. The experimental results show that the output power of the bipolar-charged e-RPG is increased to 384% compared with those of positive or negative charging alone, which is consistent with the results obtained from the theoretical model. By introducing the core-shell-structured multi-phase electrode design, both the rotation direction and speed can be precisely detected. The frequency sensitivity and linearity $\text{R}^{2}$ (coefficient of determination) are up to 3.0 rpm/Hz and 99.9%, respectively. The proposed e-RPG has potential applications in the Internet of Things, self-powered sensing and self-sensing of rotational motions. [ABSTRACT FROM AUTHOR]

Phase sequence exchange (PSE) is a recently developed emergency control technology in which power electronic devices are used to switch the three-phase sequence, thereby reducing the power angle of the generator by 120° and preventing the system from losing stability. This article proposes the installation of the PSE device in the fragile cut-set line of the power grid, and to use the local measurement information for control. This method can restore the stability of the system when the power grid oscillates, thereby avoiding the collapse of the island power grid after splitting due to oscillation. First, an improved real-time power angle calculation method is proposed. When a system loses synchronization and the power angle of a line reaches the threshold, the PSE device on the same cut-set line acts simultaneously to prevent the system from falling out-of-step and “splitting” from the cut set. A PSE prototype is used for experimental verification on the real-time digital simulator platform. The results demonstrate that the proposed power angle calculation method greatly reduces the error, and the proposed PSE control method can achieve online monitoring and real-time control, which achieves better control effects than conventional methods. [ABSTRACT FROM AUTHOR]

In this article, an enhanced short-horizon integration actual voltage reconstruction method based on nonlinear error inverse-compensation (NEIC-SHIVR) is proposed for voltage source inverters. The NEIC-SHIVR method takes into account not only the influence of nonlinear errors in modulation such as dead time addition and narrow pulses elimination on voltage reconstruction but also considers the influence of nonlinear errors in PWM transfer links such as power switch delay and switch voltage drop on voltage reconstruction. First, the real-state driving signal is computed by the output driving signal and the power switch delay time. The auxiliary driving signal is reconstructed to get the auxiliary switching state according to the phase current direction. Second, referring to the auxiliary switching states and the phase-current directions, the instantaneous equivalent bus voltage within each clock pulse is computed by the dc-bus voltage and the switch voltage drop. Finally, the output voltage within each switching period is integrated by the reconstructed instantaneous equivalent bus voltage in each clock pulse. Compared with SHIVR, NEIC-SHIVR provides a more accurate reconstructed voltage. Compared with other methods, NEIC-SHIVR inherits many advantages of SHIVR. For example, it can apply to any PWM method and does not use high-cost high-frequency voltage sensors, which improves system reliability and reduces system complexity. Simulations and experiments verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Multiobjective model predictive control (Mo-MPC), owing to its simplicity and adaptability to comply with diverse constraints, has gained popularity in the control of direct matrix converters (DMCs). However, the MPC strategy makes the converter operate at an uncontrolled and variable switching frequency, which may inhibit high power density applications due to increased power losses. This article proposes a method for controlling the switching frequency of the converter and simultaneously regulating the common mode voltage in the DMC fed system while maintaining sinusoidal load and source currents at near unity input power factor. Furthermore, in order to streamline the control while simultaneously dealing with these objectives, a suitable normalization technique is implemented for scaling the errors in each objective. This method is validated through simulation and experimental results. [ABSTRACT FROM AUTHOR]

Electrical equipment of the floating nuclear power plant operates in a long-term vibration environment. Ground faults occur frequently and are often accompanied by arc, a reliable arc suppression algorithm for the generator stator winding is necessary. In this paper, an active arc suppression method is proposed by connecting a controllable voltage source to the generator neutral point. Through regulating the neutral point voltage to be equal in amplitude and opposite in phase to the fault potential, the fault point voltage can be clamped to a low level to achieve arc suppression. Since the generator's phase potential contains certain harmonic components, the controllable voltage source includes fundamental and third-order harmonic components. To accurately calculate the output voltage, online calculation methods for the fault location, fault potential and grounding capacitance are proposed. The accuracy of the fault location method is verified by simulation and dynamic test. And simulation results based on PSCAD/EMTDC software show that the proposed method can achieve effective arc suppression at different ground fault conditions. [ABSTRACT FROM AUTHOR]

Direct lightning poses a serious threat to the safety of power systems. In recent years, the lightning fractal model, which can reflect the fractal characteristics and randomness of lightning leaders, has been gradually applied to direct lightning protection for substations, transmission lines, etc. However, since few studies have linked simulations with experiments, the reliability of the lightning fractal model in terms of attachment probability prediction lacks experimental verification. In this paper, a series of attachment tests are carried out under a rod-rod gap. The equivalence between simulation tests and natural lightning is discussed, and the influencing factors of the attachment results are investigated. The attachment probability is simulated and compared to the test value under each test configuration. The test results show that the fractal dimension of discharge channel is consistent with the observation results of natural lightning. Under different configurations, the test value of attachment probability basically conforms to the simulation value. In general, the dispersion of the test results is slightly greater than the simulation results, but the average probability differences are all within 10%. The test results strongly indicate that the lightning fractal model is of good reliability in the prediction of strike probability. [ABSTRACT FROM AUTHOR]

A new electromagnetic time-domain model dedicated to calculating the lightning response of electric systems and their components is presented. It is formulated taking as reference the main features of the frequency-domain Hybrid Electromagnetic Model. A differential aspect of this model is the capability to efficiently address problems involving nonlinear effects, such as soil ionization around grounding electrodes, the surge-arresters operation and the Corona Effect in applications related to the lightning performance of transmission lines. In addition, it is able to consider frequency-dependent effects, for instance that of soil resistivity, with an accuracy compatible with engineering applications. The basic formulation of the model is shown along with the validation of the results it yields by comparison with reliable references, including experimental results. [ABSTRACT FROM AUTHOR]

Negative-sequence current is required to be intentionally injected to support the power grid or compensate the imbalanced load in asymmetrical faults utilizing STATCOM. However, the extreme compensation range of negative-sequence current injection becomes complicated when grid voltage becomes asymmetrical. This article presents a novel off-line strategy for negative-sequence current compensation under two typical kinds of asymmetrical grid faults — single-phase voltage drop and double-phase voltage drop, with the following two benefits simultaneously: maximizing negative current compensation capacity; avoiding iterations and reducing computation burdens. In this paper, the mechanism of DC voltage balancing among three phases in STATCOM is analyzed and a new identification method of negative-sequence current compensation range is explored out. To simplify the calculation, this paper takes the ratio of negative-sequence reactive (Iq-) and active (Id-) current as a variable (s). In this way, the relationship between the extreme compensation range, asymmetrical voltage sag depth of power grid h is drawn with MATLAB. Different from the previous iterative method, the off-line identification method is applied to avoid huge iterations. By fitting the curve, the precise ranges of negative-sequence current compensation under different asymmetrical grid faults are approximated as simple polynomials, thus significantly reducing the computation burdens. Simulation and experimental results verify the practicability of the proposed compensation method. [ABSTRACT FROM AUTHOR]

Phase–locked loop (PLL) is commonly used for the grid-connected voltage-source converter (VSC) to synchronize with the grid. Under weak grid conditions, it has been found that the frequency-dependent characteristic of the network impedance inherently introduces a positive feedback loop into PLL. Previous studies focused on the PLL analysis intuitively believe that the positive feedback loop will deteriorate the dynamic performance of the PLL. However, this conclusion is not rigorous since only the dynamic of the PLL is considered and the theoretical analysis is insufficiency to reveal the influence of the positive feedback loop on system stability. In this paper, the impact of the frequency-dependent network on VSC stability is quantified in terms of the overall system based on the damping torque analysis. It is found that the influence of the positive feedback loop on stability depends on the parameters of the PLL and the damping of the dominant eigenvalues. Besides, an angular frequency feedback scheme is proposed to eliminate the adverse effect of the frequency-dependent network and enhance the stability of the VSC under weak grid conditions. Time-domain numerical simulations and reduced-scale experiments are performed to validate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Owing to the phase delay and resonance oscillations introduced by the LC filter connected in-between the voltage-source inverter (VSI) and the induction motor (IM), the “L” and “C” design methodology is critical. Also, the closed-loop control and the speed sensorless operation of such drives are complex without stator voltage sensors. This article addresses these issues by proposing a simple filter inductor ($L_{f}$) selection criterion for an LC filter equipped IM drive, which allows retaining the designed dc-bus capacitor, heat-sink, and power devices of VSI upon LC filter insertion in-between the VSI and IM. Furthermore, an existing filter capacitor selection criterion is improved adhering to the constraint on voltage drop ($V_{f}$) across $L_{f}$. In addition, this article also examines the existing active damping (AD) techniques to perform the speed sensorless operation on the IM + LC (IMLC) filter drive without stator voltage sensors and improves one of them to achieve the same. Summarily, through the filter selection criteria and improved active damping technique, this article proposes to retrofit the LC filter into the IM drive and performs speed and voltage-sensorless operation. The simulation and experimental results obtained from a 5-hp IM drive are presented to validate the proposed work. [ABSTRACT FROM AUTHOR]

Capacitor voltage balancing is one of the most important issues for the safe, reliable, and economical operation of the modular multilevel converter (MMC). This article proposes a modified individual capacitor voltage balancing method for MMCs with phase-shifted carrier pulsewidth modulation (PWM) (CPS-PWM) to solve the problem of the poor dynamic performance that the conventional individual voltage balancing methods suffer at low output power. In the proposed method, the information of arm current is incorporated into the balancing algorithm to cancel out the coupling effect of the output power on balancing control. Compared with conventional balancing methods, the proposed method shows better robustness against varying output power and maintains a good dynamic performance in a wider power range. The complete modeling process and parameter design are presented and considered for system stability. The effectiveness of the proposed method is verified with both MATLAB/Simulink simulation and experimental results. [ABSTRACT FROM AUTHOR]

Nowadays, the three-level T-type inverters (3LT2Is) are widely employed in applications with high-performance requirements. The 3LT2Is commonly suffer from neutral point voltage (NPV) unbalance and common-mode voltage (CMV) variation. The medium vector pulse width modulation (MVPWM), which generates the reference voltage using medium and V0[OOO] zero voltage vectors, eliminates the CMV variation in 3LT2Is. However, it cannot keep the NPV balance, negatively affecting power quality. This article proposes a hybrid method to simultaneously eliminate CMV variation and guarantee the NPV balance without topological change or extra hardware. The proposed method uses MVPWM when NPV is balanced, eliminating CMV variation. If NPV goes unbalanced, it utilizes novel high/low triangle PWM (H/LPWM) and MVPWM in a hybrid manner to balance the NPV. The H/LPWM, similar to MVPWM, synthesizes voltage using medium and V0[OOO] voltage vectors to maintain the CMV elimination advantage during the NPV balancing process. However, the difference between H/LPWMs and MVPWM switching patterns adjusts the average neutral point current to balance the NPV. Noteworthy that the proposed method provides NPV balancing ability for the entire power factor range. As a result, it is usable for various applications of 3LT2I, such as photovoltaic inverters and motor drives. The proposed method is carrier-based, which reduces the execution time and simplifies the practical implementation. The simulation study and experimental evaluation have been accomplished, and their results demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMC) are increasingly gaining its importance in HVDC, drive applications due to several attributes such as modularity, scalability, low device stress, excellent output voltage waveform. For MMC operations, it is important to accurately measure the voltages across the individual capacitors of submodules (SMs). These voltage sensors, while upgrading for high voltage applications, may cause a few concerns in terms of cost, complexity, and data acquisition system. To avoid all these, a discrete time adaptive observer (DTAO) is proposed in this article to observe the voltages across the capacitors of the SMs and use the observed values for closed-loop operation of the MMC. The proposed observer is designed by considering the parametric uncertainty in the MMC and its convergence is proved mathematically. Moreover, the DTAO is compared with existing observation techniques for MMC SM capacitor voltages. The efficacy of the proposed observer is shown through simulation and validated using an experimental setup. [ABSTRACT FROM AUTHOR]

The dc transformer based on CLLC resonant converter is widely researched in the dc microgrid due to its excellent bidirectional power transfer capacity. Many resonant network design methods assume that the resonant current is constant during the deadtime. It may lead to hard switching or large conduction loss. Besides, the effects of deadtime on soft switching have not been closely analyzed. This article proposes an optimized design method to minimize conduction losses while achieving zero voltage switching, and it can easily obtain the optimal region and deadtime selection range. Parametric design and deadtime selection principles are derived based on the time-domain models, and then the design method and corresponding procedure are developed. Finally, a 4-kW 500-kHz CLLC resonant converter prototype is built to verify the feasibility of the proposed optimal design method. [ABSTRACT FROM AUTHOR]

An overmodulation method is proposed for an in-wheel system where two motors are coupled to a sum gear. In the dual-motor dual-inverter single shaft systems, the output voltage magnitudes of two inverters are not the same in the overmodulation range due to the angle offset between two motors. In this article, to maintain torque balance in the overmodulation region, holding vectors are defined between adjacent vertices of two voltage hexagons. Around these vectors, the holding region is also defined by the holding angle. If a reference voltage vector is in the holding region, it is modulated to the holding vector; otherwise, it is modulated to the vector on the arc of inscribed circle. For a given the modulation index (MI), the holding angle is obtained based on the Fourier series expansion. The proposed method keeps the output voltages of two inverters the same even if two motors have the angle offset. Further, it has the characteristic of maintaining the linearity between the reference and output MI to the maximum MI. The proposed overmodulation method is demonstrated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

A synchronous condenser (SC) can provide the dynamic reactive power for the ultra-high-voltage direct current converter station during the system voltage drop caused by the single-phase short-circuit fault, which is one of the prevalent faults. However, the single-phase short-circuit fault can also result in the increase of the rotor loss and temperature and thus restrict the transient operating ability of the SC. A key factor that affects the rotor loss and temperature rise is the material of the rotor slot wedges. For a 300-MVar SC with the rotor slot wedges made of the aluminum, beryllium bronze, and stainless steel, the rotor loss and temperature distribution under the single-phase short-circuit are calculated by coupling the electromagnetic and temperature field models of the SC with the models of the power grid. The variations of the rotor losses along with the rotor slot wedge conductivity are revealed. The rotor regions, where the highest temperature rise appears, are obtained. According to the maximum permissible temperature of the rotor material, the transient operating ability of the SC withstanding the single-phase short-circuit fault is obtained. This article can provide the theoretic basis for improving the transient operating ability of the SC. [ABSTRACT FROM AUTHOR]

Superconductor–semiconductor hybrid circuits can combine the benefits of the high-speed and low-power operation of single-flux quantum circuits and high integration densities of CMOS technology such as memory. The Suzuki stack, a type of Josephson latching driver/amplifier, is a widely used interface circuit in Josephson–CMOS hybrid memories. Due to the limited cooling power at cryogenic temperatures, the power dissipation is becoming an important concern, especially in large-scale systems. An optimization technique to significantly reduce the power dissipation of Suzuki stack circuits is proposed in this article. The proposed design can reduce the power dissipation by 30–70% while causing a voltage drop of 2–9% in the output voltage depending on the circuit parameter configuration. The tradeoffs between the power dissipation and output voltage characteristics are discussed. The proposed design can operate correctly within at least $\pm$ 20% of process parameter variations as demonstrated with extensive simulations. [ABSTRACT FROM AUTHOR]

FinFETs have a bright future for advanced analog/RF and digital circuit design in 5G/6G technology. As the integration density increases, the self-heating effect (SHE) becomes more severe, and the hot carrier injection (HCI) reliability of FinFETs further deteriorates since it is highly dependent on temperature. In this article, an artificial neural network (ANN) model for HCI prediction is proposed for 14-nm FinFET with consideration of SHE under various voltage stresses and environment temperature. The HCI numerical simulation can be mainly divided into two parts: 1) the temperature responses for the device under different stresses are obtained by numerically solving time-dependent thermal conduction equation with heat generation in the nanoscale FinFET and 2) based on the transient temperature response to different stress voltages, HCI-induced threshold voltage shift (TVS) as a function of time is captured numerically. Our HCI-induced TVS simulation results agree well with others’ experiment results, which verifies the simulation methods. An ANN model is then developed to predict the TVS induced by HCI with the training data obtained from numerical simulations. The ANN model has good accuracy with an average relative error of 0.36% in predicting TVS and greatly reduces simulation cost once the ANN model is built for the HCI prediction of FinFETs, which has great potential for reliability design in circuits and systems. [ABSTRACT FROM AUTHOR]

A recently proposed theoretical methodology for the assessment of the electromigration (EM) induced IR-drop degradation in on-chip power/ground grids has been validated by means of measurements performed on real silicon. A voltage tapping technique was employed for the direct measurement of voltage variations at 162 nodes of the power net, stressed with 10 mA constant source current at an elevated temperature of 350 °C. A voltage drop between cathode and anode pads exceeding a specified threshold was considered as a failure. Times-to-failure (TTF) was measured on 19 packaged test grids and used for computing the mean TTF (MTTF). The EM-induced voltage degradation in this grid was also analyzed with an assessment methodology based on a simulation of stress evolution everywhere in the grid, resulting in a voiding in some of grid branches and corresponding resistance increase. A set of voiding compact models for different grid segments was developed and used in the simulations. The stochastic nature of the EM phenomenon was captured by introducing random distributions of atomic diffusivities and critical stresses across the grid and iterating them with Monte Carlo loops. A good fit between the measured voltage evolution kinetics at different grid nodes and that predicted by simulation, and the good agreement between measured and simulated failure distributions can be considered as the ever first experimental validation of this EM assessment methodology for on-chip power/ground (p/g) grids. [ABSTRACT FROM AUTHOR]

In this article, a hybrid capacitor voltage balancing control based on selective harmonic elimination pulsewidth modulation (SHE-PWM) is proposed for four-level hybrid-clamped (4L-HC) converters that operates at very low switching frequency. In low and medium modulation index (ma) range, a novel SHE formulation is introduced, where the objective function for natural capacitor balancing is added into the nonlinear SHE equations. With the optimal SHE patterns and switching angles obtained from this formulation, all capacitors can be balanced naturally without additional switching actions for swapping the redundant states to regulate the capacitor voltages, which greatly reduces the switching frequency compared with other active capacitor voltage balancing methods and modulations. In high ma range, SHE model predictive control (SHE-MPC) is adopted, where the output voltages follow SHE-PWM patterns but with MPC used for capacitor balancing and switching frequency regulations. Simulation and experimental results, as well as detailed numerical analysis and comparisons with other PWM and capacitor voltage balancing methods for 4L-HC converters are provided to demonstrate the good voltage regulation performance and superiorities of the proposed method. [ABSTRACT FROM AUTHOR]

Droop control strategy is widely used to control parallel inverters in a microgrid. However, due to the mismatched line impedance, the traditional droop control strategy is difficult to evenly share the reactive power and restrain the circulating current among multiple parallel inverters. In this article, an adaptive virtual impedance-based droop control strategy without communications is proposed to solve the reactive power sharing problem caused by the difference of line impedance. The reactive power output and voltage of each distribution generator are introduced into the adaptive virtual impedance controller to achieve a tradeoff between reactive power sharing accuracy and voltage drop. Small-signal stability analysis of the inverters equipped with the proposed controller is conducted to determine the optimal control parameters. Simulation and experimental results demonstrate the effectiveness of the proposed droop control strategy. [ABSTRACT FROM AUTHOR]

This article proposes a space vector pulsewidth modulation using space voltage vector mapping and the midpoint-voltage self-balancing strategy to overcome the shortcomings of the existing active neutral-point-clamped five-level inverter modulation. Through multispace mapping, the five-level topology is converted into multiple two-level topologies for calculation. It greatly simplifies the computational burden. By adopting the midpoint-voltage self-balancing strategy, the midpoint-voltage self-balance is achieved, since the switching sequence of different sectors compensates each other for balancing the midpoint voltage. Therefore, this algorithm realizes that there is no or only a minimum number of switch tube actions when the reference voltage vector swaps different sectors. It reduces the switching loss and effectively avoids equipment damage caused by the simultaneous switching of multiphase switches. In addition, it also realizes the floating-capacitor voltage control by reasonably distributing the redundant switch states. Simulations and experiments verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This article presents an efficient and fast echelon battery equalization method based on wide voltage range bidirectional converter combined with DBSCAN (density-based spatial clustering of applications with noise) clustering control strategy. Thanks to the wide voltage range and bidirectional buck-boost characteristics of the four-switch bidirectional converter, the battery energy can be reasonably redistributed between the battery and the super capacitor. The converter operating in synchronous rectification mode can not only achieve bidirectional energy flow in a wide voltage range, but also has a high energy conversion efficiency. The DBSCAN clustering algorithm is used to divide all battery cells into groups, and each group may contain one or more adjacent and nonadjacent battery cells. First, the nonadjacent single cells are balanced and integrated into adjacent group with the closest voltage. Then, the groups with different voltages are balanced by group-to-group, thereby realizing rapid balance of the entire battery pack. In order to verify the effectiveness of the proposed method, simulations and experimental verification were carried out. The experimental results show that, comparing with traditional battery balancing methods, the proposed method achieves shorter balancing time and higher balancing efficiency. [ABSTRACT FROM AUTHOR]

The dependence of overall traveling-wave tube (TWT) efficiency on the collector efficiency is of paramount importance. The objective of achieving high overall efficiency drives us to design a multi-stage depressed collector (MDC) with the theoretically highest possible efficiency with appropriate depressed potentials. Various design parameters, namely electrode geometry, depressed potentials, material parameters, etc., can be optimized to attain the desired theoretical maximum collector efficiency. But in a practical situation, the measured MDC efficiency is relatively less than the designed efficiency, which may be attributed to approximations involved in the nonlinear interaction of the electron beam and RF wave, fabrication inaccuracies, process limitations, simulation approximations, etc. This inexplicable practical decrease in MDC efficiency is typically accompanied by an increase in the backstreaming of electrons into the interaction structure. To compensate for this decrease, a permanent magnet has been suitably positioned on the base plate of the MDC, which results in an increase in collector efficiency. Simulation studies have been carried out to optimize the parameters of the magnet in terms of the geometrical dimensions, position, and magnetic field value, and has been validated experimentally. This technique of collector efficiency enhancement using an external magnet has proven to be very effective, contributing to a significant collector efficiency enhancement of > 5% from ~78% to ~83%, which in turn corresponds to an overall tube efficiency improvement of ~5.8% from 50.5% to 56.3%. [ABSTRACT FROM AUTHOR]

In this letter, we present an extensive analysis on the role of both switching frequency (ranging from 100 kHz to 1 MHz) and duty cycle (from 10% to 90%) on the time-dependent gate breakdown of high electron mobility transistors (HEMTs) with Schottky metal to p-GaN gate. More specifically, results show how the gate lifetime of GaN HEMTs increases by reducing the frequency and the duty cycle of the stressing gate signal (VG). Such behavior is ascribed to the OFF-time, which is responsible to alter the electrostatic potential in the p-GaN layer during the rising phases of VG (from OFF- to ON-state). Findings of this analysis are useful both for further technology improvement and for GaN-based power circuit designers. [ABSTRACT FROM AUTHOR]

The estimation of pH is vital to assess the biochemical and biological processes in a wide variety of applications ranging from water to soil, health, and environment monitoring. This work reports a screen-printed flexible and disposable pH sensor using the impedimetric method. The pH sensor was fabricated by screen printing graphene-carbon (G-C) modified zinc oxide (ZnO)-based active layer on a paper substrate and shows nearly three orders of change in impedance magnitude in the pH range of 2–9. The sensor was carefully designed using COMSOL Multiphysics software to understand the influence of electrode geometry and the electrical potential developed across the structure. The developed sensor was used for pH monitoring of soil and exhibited high sensitivity of 5.27 $\text{k}\Omega $ /pH 2–8 with a correlation coefficient (${R}^{{2}}$) of 0.99. Finally, an IoT-enabled smart pH detection system was implemented for continuous pH monitoring for potential application in digital agriculture. The outcome demonstrates that the presented flexible and disposable pH sensor could open new opportunities for monitoring of water, product process, human health, and chemical (or bio) reactions even by using small volumes of samples. [ABSTRACT FROM AUTHOR]

As one type of associative memory, content-addressable memory (CAM) has become a critical component in several applications, including caches, routers, and pattern matching. Compared with the conventional CAM that could only deliver a “matched or not-matched” result, emerging multilevel CAM (ML-CAM) is capable of delivering “the degree of match” with multilevel distance calculation. This feature has been desired in applications that need beyond-Boolean matching results. However, existing ML-CAM designs are limited by the bit-cell device discharging current mismatch and vulnerability to the timing of sensing operations for distance calculation. This inherent constraint makes it difficult to further improve the accuracy and scalability toward higher accuracy and higher dimension matching. In this work, we propose CapCAM, a multilevel Capacitive Content Addressable Memory. It could be implemented based on either static random-access memory (SRAM) or emerging technologies, e.g., the ferroelectric field-effect transistor (FeFET). CapCAM could provide linear and stable voltage drop scaled by the match degree and need no strict timing for result sensing, which embraces the high-accuracy and high-scalability search. The inherent enabler of CapCAM is the charge-domain computing mechanism. This article will present the basic concept, operating mechanisms, detailed circuit designs, and circuit-level simulations of CapCAM. Besides, we apply CapCAM to few-shot learning applications and compare CapCAM with the current-domain TCAM designs. Results show 99.2% accuracy for a five-way five-shot classification task with our proposed CapCAM design while considering 1-fF capacitors, 20-domain FeFETs, and 256 columns. In contrast, the prior work based on discharging dynamics requires strict timing controls and suffers from accuracy degradation under the same configuration, which demonstrates CapCAM’s capability of low-power, accurate, and scalable multilevel CAM (ML-CAM) computing. [ABSTRACT FROM AUTHOR]

The active and dynamic controls of the terahertz (THz) waves are highly demanded due to the rapid development of wireless communication systems. Recently, reconfigurable intelligent surface (RIS) has gained significant attention due to their tremendous potential in controlling electromagnetic (EM) waves. Particularly, RIS-based wireless communications are promising for improving the system’s performance by properly designing the reflection coefficient of the unit cell. In this work, we investigate a graphene-based RIS for active and dynamic controls of THz waves. The RIS design consists of a rectangular graphene meta-atoms periodic array placed over a metallic grounded silicon substrate. An equivalent circuit modeling of the RIS design and its solution is provided. The RIS performance is numerically analyzed. The graphene-based RIS achieves nearly 100% reflection in the operational frequency ranging from 0.1 to 4 THz. The perfect reflection is insensitive to the polarization and the incident angles. Moreover, 100% absorption in the graphene-based RIS is achieved by electrically reconfiguring the meta-atom response via the chemical potential of the graphene. The graphene RIS also achieves the anomalous reflection performance by controlling the number of unit cells and phase gradient of RIS. In view of the effective THz wireless communication environment, this article finally presents a simple RIS-aided communication model to study the impact of the proposed graphene-based RIS on the signal-to-noise ratio (SNR). The results reveal that the proposed THz RIS with graphene meta-atoms is promising for efficient and intelligent THz wireless communications. [ABSTRACT FROM AUTHOR]

Live-line maintenance is an effective means to ensure the reliability of the power system. When linemen float between the high-voltage conductors and the ground potential towers, the discharge characteristics of air gaps are significantly affected. In this article, simplified experiments are carried out to simulate the linemen by a floating conductor. The discharge characteristics of air gaps when the floating conductor is in different positions are studied. An experimental platform with a long air gap containing a floating conductor is used to obtain the breakdown voltage and the discharge path of air gaps under a positive switching impulse. The experimental results show that the existence of a floating electrode affects the air gap breakdown voltage and the discharge path. When the transverse displacement is 80 cm, almost all the discharge paths directly connect the high voltage electrode and plane electrode. Furthermore, the influencing factors of discharge path and breakdown voltage are analyzed, and the fitting equations of breakdown voltage and discharge path probability considering spatial position coordinates are established. Finally, the easy breakdown region considering discharge path is proposed, which provides a theoretical reference for quantitative analysis of the path of linemen entering high potential safely, and to improve the working efficiency of live-line maintenance. [ABSTRACT FROM AUTHOR]

A voltage drop normally occurs when a power source runs for a load system through long-distance cables. To compensate for such voltage drops, it is necessary to provide remote detecting and controlling of the load-side voltage and boost to the required voltage. In this article, a novel impedance detection method providing more reliable and accurate resistance and inductance measured results for remote cables is presented. Meanwhile, a digital–analog hybrid control strategy based on the impedance detection method is presented to compensate for the voltage drop and delayed response caused by cable intrinsic impedance. Compared with traditional methods, the proposed strategy performs detection and compensation at the source of the cable, and can be integrated into power source devices without imposing extra burden to the load system, which is more attractive and promising in engineering application. Finally, a prototype is built for experimental verification, and a systematic and intuitive comparison is conducted with existing voltage-drop compensation methods. The experimental and comparative results indicate that the problems of voltage drop and delayed response caused by long-distance cables are solved, and the accurate and rapid regulation of the remote voltage is achieved. [ABSTRACT FROM AUTHOR]

High step-up dc–dc converters are widely used in new energy applications such as photovoltaic cell, fuel cell, dc microgrid, etc. Active switched-inductor (ASL) converter has simple operation and low stress on switches. To further increase the voltage gain, some SC (switched-capacitor)/ASL step-up converters have been proposed recently. However, these SC/ASL step-up converters have voltage oscillation on switches, which leads to the voltage stress on switches is higher than the theoretical value. In this article, a novel high step-up SC/ASL converter is proposed. Compared with other SC/ASL step-up converters, the proposed converter has lower voltage stress on the switches, output diodes, and output filter capacitors, and the efficiency is higher. In addition, the proposed converter can achieve self-voltage balancing on switches. This article analyzes the proposed converter from operation principle, continuous conduction mode (CCM) analysis, CCM operation with unbalanced inductors, input current ripple analysis, discontinuous conduction mode and boundary conduction mode analysis, switches self-voltage balancing characteristic, voltage stress, current stress, comparison analysis, and design considerations. Finally, a 200 W, 25–45 V/380 V, 50 kHz experimental prototype has been established in the laboratory to evaluate the proposed converter, which reached a peak efficiency of 97.3%. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC), owing to the presence of a large number of submodules (SMs) and energy storing elements, requires a large footprint and initial investment. To address these issues, this paper proposes the switched modular multilevel converter (SMMC). It consists of two major elements; the chain-links (CLs), consisting of cascade connection of SMs as in MMC, and the single-pole-triple-throw (SPTT) switches, which can be realized using either the T-type or NPC-type switch strings. The SMMC works on the principle of connecting all the phase-legs in series and their respective positions are mutually interchanged. It offers a compact structure as the SMs count is reduced to 33% of MMC, which results in a much lower energy storage requirement. Furthermore, it does not have inter-phase circulating current problem and hence the CL inductors can also be avoided. The SMMC structure, operating principles, control, and modulation schemes are explained in detail. A detailed comparison of SMMC with the other major existing converters is carried out to highlight the important features of SMMC. The efficacy of SMMC is validated using PSCAD simulation studies with a 19-level grid-connected SMMC model. A 3-phase 19-level SMMC laboratory prototype is developed to further validate its feasibility. [ABSTRACT FROM AUTHOR]

High junction temperature is usually the main factor leading to device failures in high-power working conditions, such as surges or avalanches. It is of great significance to obtain the junction temperature quickly and accurately. Direct measurement of junction temperature is inconvenient, and usually indirect electrical measurement combined with model calculation is used. An electrothermal coupling junction temperature calculation model with distributed heat sources is proposed in this article. This model can accurately and quickly predict the device behavior during the surge process, as well as the voltage drop and temperature changes of each part of the device, without actually performing surge tests. This article describes the theoretical basis and calculation principles of the model. By taking a commercial SiC merged PiN Schottky diode as an example, this article also explains the details of the establishment of the electrical and thermal characteristic models of the device, as well as the calculation steps of the junction temperature by the thermal coupling model. The calculated device voltage drop curve of the device is in good agreement with the measured ones, and the calculated junction temperature curve is more consistent with the device failure mechanism than the one by the traditional RC thermal circuit model. [ABSTRACT FROM AUTHOR]

Metal oxide varistors (MOVs) with steady decrease and continuous increase in power loss are generally distinguished as stable and instable, respectively. In this article, the power loss of modern stable MOVs were found to anomalously increase, when the aging voltage was even lowered. In other words, those MOVs were superficially stable in harsh conditions but instable in mild conditions, which was against common sense. In addition, a crossover phenomenon and an overall deterioration in the current–voltage characteristics were observed in the forward and reverse directions, respectively. The unique aging results were in well consistency with the numerical simulation, where redistribution of ions in depletion layers was involved. For modern stable MOVs with adamant interface states, the formation of “U”-shaped ion distribution in depletion layers resulted in increased barrier height at high voltages but decreased height at low voltages. For an arbitrary MOV, the evolution of power loss during aging was a result of competition between consumption of interface states and re-distribution of ions in depletion layers. Therefore, the power loss might not be sufficient to represent the degradation of MOVs. Quantitative studies deep into the dynamics of point defects of Schottky barriers of MOVs are urgent. [ABSTRACT FROM AUTHOR]

The lightning impulse breakdown strength of natural ester is lower than that of mineral oil. This article focuses on a discharge mechanism difference analysis of natural ester and mineral oil under a strong impulse electric field (EF). Based on density functional theory (DFT), the ionization energy, electron affinity (EA), and excitation energy of natural ester and mineral oil were calculated under different EF strengths. The microparameters related to the discharge of natural ester and mineral oil were compared, showing that the former has a lower ionization energy and a larger dipole moment. This quality makes natural ester more likely to ionize and produce electrons, which more easily promotes the formation of electron avalanches and streamer. Meanwhile, natural ester molecules are more prone to transition from the ground state to the excited state than mineral oil molecules, exacerbating the photon release and formation of discharges in natural ester. The greater conductivity of natural ester leads to its dispersion and the rapid development of discharge streamers. In addition, an electrostatic potential (ESP) analysis on molecular surfaces was used to predict the active sites of the oil molecular structure. This article provides help for understanding the relationship between the micromolecular structure and the macroscopic discharge characteristics for different types of oil molecules. [ABSTRACT FROM AUTHOR]