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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]

This paper presents an online method to monitor the conditions of the substation grounding grid. The proposed method utilizes phase-to-ground faults occurring in downstream feeders as test current sources and the neutral of a specially selected feeder as the electrode for GPR (ground potential rise) measurement. The measured fault currents and GPRs are then used to estimate substation grounding grid impedance. The method, once established, can monitor the grounding grid impedance continuously and automatically, and the trend of the impedance change can be observed. As a result, the proposed method can yield much more reliable information on the substation grounding conditions. The method also overcomes many disadvantages of the offline methods. The proposed idea, algorithm, and hardware setup are described in the paper. Factors contributing to measurement errors are investigated in detail. [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 work we describe the Square Wave Anodic Stripping Voltammetry (SWASV) electrochemical technique for the determination of lead (Pb2+) and cadmium (Cd2+) metal ions at concentration of sub-part per billion (ppb) in aqueous solution. Moreover, simple and low-cost procedures for the fabrication of high performance working nano-electrode are reported. The electrode structure consists of a graphene paper (GP) $240~\mu \text{m}$ thick with the function of electrical conductor and substrate, a layer of nafion 0.5- $0.7~\mu \text{m}$ thick onto the graphene paper and bismuth nanoparticles embedded in the nafion thin layer. The bismuth nanoparticles were fabricated by electrodeposition starting from Bi(III) ions, employing a key step of hydrogen ions of nafion $\text{H}^{\mathbf {+}}$ exchange with bismuth ions Bi(III). This procedure is aimed to improve the bismuth nanoparticles concentration. The SWASV applied to the low-cost nanoelectrode allows detecting Pb2+ and Cd2+ at concentration as low as 0.1 ppb. [ABSTRACT FROM AUTHOR]

The surface voltage of an insulator assumes importance for understanding tracking and flashover characteristics. Until now, determination of surface voltage of insulating surfaces is left to simulation software and such simulations are left unverified experimentally, leading to uncertainty of the results, which may sometimes be erratic with improper choice of boundary or initial conditions or inaccurate material properties, nonlinearities etc. The paper presents a novel method, using which the surface voltage of any insulating surface such as insulator strings or transformer bushings can be measured. Unlike a conducting surface, the measurement of insulating surface voltage using voltage dividers would be erratic as the measuring arrangement itself will vary the voltage division due to the local unknown impedance between the insulated surface and hv conductor. Recently a method for measurement of surface voltage of an insulated conductor using cylindrical strips was reported. In this paper, based on analytical derivations, a more generalized method of measurement, applicable to any point on an insulating surface of arbitrary geometry is proposed using circular-disc strips. The proposed experimental method is applied to insulator strings and transformer bushings and validated by simulation of the entire systems. The simulation and experimental results are in excellent agreement. [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]

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]

This paper focuses on the issue of network connectedness (NC) in security-constrained optimal transmission switching problems, which is complicated by branch contingencies and corrective line switching. Two criteria are firstly proposed with the principle of preserving NC as much as possible within reasonable limits. By extending the electrical flow based NC constraints, a proposition is derived to associate different cases of NC with the optimum of a linear program, yielding the mathematical formulation of the NC criteria. By Karush-Kuhn-Tucker conditions, this formulation is further transformed into a tractable version which can be incorporated with existing SCOTS models without affecting the applicability of original solution approaches. Finally, case studies on various networks and SCOTS models demonstrate the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a novel hierarchical cooperative control strategy to solve the problems of unbalanced State of Charge (SoC), unreasonable load current sharing, and unstable bus voltage for battery storage system (BSS) in islanded DC microgrid. In the communication layer, a neighbor-to-neighbor communication network architecture is constructed in which each battery storage unit (BSU) only communicates information with neighboring nodes, and a multi-agent consensus algorithm is used to iteratively estimate the relevant average global variables. In the main control layer, the droop coefficient is dynamically adjusted by constructing a fast SoC convergence function to ensure that the load current is reasonably distributed based on the rated capacity of each BSU. In the secondary control layer, a virtual voltage drop equalization controller and an average bus voltage compensation controller are designed to eliminate the impact of line impedance mismatch and compensate the average bus voltage. Furthermore, an optimized factor is designed to accelerate the later stage of SoC convergence. Finally, a DC microgrid experimental platform based on StarSim HIL is built, and the results demonstrate that the proposed strategy can achieve the control objectives of fast SoC balance, proportional load current sharing, and bus voltage stability. [ABSTRACT FROM AUTHOR]

This paper proposes a time-domain method of characteristics to simulate the impulse corona with background space charge, and derives the ordinary differential equations of the space charge generated by the impulse corona along the electric field line. The corresponding boundary conditions, the selection of time step and space step, and the update strategy of space charge are given. The calculation result of the impulse corona onset voltage is consistent with the test result, proving that the background space charge has almost no effect on the impulse corona onset electric field which is obtained by Kaptzov's assumption. The q-u curve obtained by simulation is compared with the test results to verify the effectiveness of the simulation method. The simulation method is used to obtain the development process of space charge during the application of the opposite polarity impulse voltage. By analyzing the space charge distribution during the process of impulse corona, and the corresponding microscopic charge distribution and macroscopic charge amount at different corona states, the characteristics of impulse corona are explained. [ABSTRACT FROM AUTHOR]

Electrochemical Impedance Spectroscopy (EIS) is an analytical technique widely used in electrochemistry. EIS is being commonly used by researchers in biosensor development, corrosion study, battery, solar cell and fuel cell performance measurement etc. Due to the availability of high precision analog-to-digital and digital-to-analog converters available on microcontroller chips at low costs, EIS based purpose-built consumer electronic devices becoming more commonplace now. This tutorial paper presents the essential theoretical knowledge to understand the EIS and how the practical parameters are selected for an EIS measurement for a novice. The theoretical explanation of EIS is followed by a section with examples of the use of EIS in electrochemical biosensor development and performance measurement of batteries. This paper finally concludes on the advantages of the use of EIS as an analytical technique. [ABSTRACT FROM AUTHOR]

This paper presents Space Vector Modulation (SVM) sequences that reduce Common Mode Voltage (CMV) in Dual Three-phase Asymmetrical Induction Motor (DTAIM). At first, two existing SVM techniques such as Reference SVM (RSVM) and CMV1 are studied. Additionally, three new switching sequences are developed as CMV2, CMV3 and DCMV3, which reduce peak magnitude of CMV by 66.8% in comparison with RSVM technique. In SVM techniques, to obtain least CMV, zero vectors are usually replaced by two opposite large Active voltage Vectors (AV) with equal time duration. In such topologies like CMV1, total six AVs are utilized to synthesize the reference vector. The proposed SVM technique CMV2 utilizes only five large AVs to synthesize the reference vector and reduces CMV. Selection of five neighbouring AVs is reflected in reduction of harmonic flux trajectories and stator current ripple in proposed techniques. Additionally, two more switching sequences (CMV3 and DCMV3) are developed related to utilization of specific zero voltage vectors in all sectors (7 and 56) that produce zero CMV. These two switching sequences also provide easy implementation feature during the development of c-code program. In this study, CMV and stator current ripple are considered as performance parameters for different SVM techniques. All SVM techniques are analysed by analytical results, computer simulations, and using prototype test setup of DTAIM fed by Dual Three-phase Voltage Source Inverters (DTVSIs). [ABSTRACT FROM AUTHOR]

This paper proposes a novel layout for a grid-connected DC wind farm (DCWF) and investigates the performance under continuous operation and direct lightning strikes particularly for high soil resistivity. The DCWF employs internal dc grid that supplies generated power to the host AC utility through high voltage direct current (HVDC) transmission link. The proposed layout ensures sustainability of power supply against potential interruptions of DCWFs either during normal conditions or lightning incidents to comply with grid codes regulations. During continuous operation, the proposed layout safeguards the entire DCWF cables against flow of return currents to avert derating of conductor ampacity. Besides, protects WT nacelle switchgear and entire interface converters against hazards of surge currents. Furthermore, an effective grounding system design is proposed to introduce a low impedance path for system return currents, minimize voltage drop across grounding impedance and thus maximize DCWF delivered power to the grid. A detailed system that sufficiently represents models of system cables, grounding network and interface converters is built to verify the proposed scheme significance. The obtained results assure the capability of proposed layout to cease return currents via cable sheath during continuous operation and provide superior mitigation of lightning-associated transient voltages and currents. [ABSTRACT FROM AUTHOR]

An electric potential appears at floating wires located within a strong electric field. This phenomenon can be used to supply small isolated communities situated close to Extra-High Voltage transmission lines. This non-conventional distributed generation system has been studied for the last years. However, to improve the power generation system the optimal position of the floating wires, number of wires used, bundle radius, and type of wires must be properly identified. This paper presents a mathematical model solved with genetic algorithm to design a collector system with optimized induced voltage and minimized project cost, identifying the optimal reactor used for voltage regulation. The algorithm was applied to design a collector system that can tap-off 100 kW from a 230 kV transmission line. The trade-off between objectives and the Pareto optimal solutions were evidenced via several simulations using the weighting sum approach. These results allowed to identify a final geometry according to a-posteriori designer preferences. [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]

The need for innovation in medical device technology is immense; especially to replace dialysis techniques the necessity is extremely high. Available techniques that promised to replace dialysis have not yet geared up to the marketization level. The utilization of live kidney cells makes these devices costly, delicate, and unreliable. This paper aims to design a bioreactor to mimic the reabsorption function of the kidney that is fully artificial and highly controllable, which can be one step forward to the emerging Kidney-on-Chip (KOC) technology. The additional benefit of the proposed design is that it utilizes size-dependent reabsorption along with charge-dependent reabsorption phenomena to make it more compatible with human kidney function. The electrophoresis (EP), and di-electrophoresis (DEP) techniques are utilized to mimic the reabsorption function in this report. The structure utilized in the present design exactly replicates the proximal convoluted tubule (PCT) dimensions and functions as well. The whole setup is implemented in the COMSOL Multiphysics FEM benchmark tool for simulation, and analysis with appropriate boundary conditions. The device when excited by an electric field, Electrophoresis has produced a maximum velocity of 1.07 m/s for DC excitation and di-electrophoresis has produced a maximum flow velocity of 1.23 m/s, where both the offset voltages are the same (0.7 V). The flow velocity obtained utilizing both EP and DEP produced a reabsorption rate of 50-58% depending on the voltage applied and dimensions considered which is close to 60% reabsorption rate of the normal human kidney PCT. In accordance with the outcomes produced, the di-electrophoresis technique proved to be more efficient in realizing bioreactor as compared to electrophoresis. The novelty of the present work lies in the creation of a simulation environment, rigorous analysis, and optimization of the bioreactor supported by compact mathematical model. [ABSTRACT FROM AUTHOR]

For biomedical imaging in mini-scale, the inverse problem of electrical impedance tomography (EIT) is severely ill-conditioned due to the number of electrodes is very limited. In this paper, a novel difference imaging algorithm for 2D-EIT using measurement estimation of virtual electrodes is proposed. The proposed reconstruction algorithm breaks though the limitation of micro EIT sensor’s structure and tackles the problem of low spatial resolution in mini-scale by introducing virtual electrodes. The inverse problem of EIT is decomposed into two separately tasks: estimation potentials of virtual electrodes with proper priors, determination of the conductivity distribution using both virtual and real electrodes. It is formulated as a possibility model using virtual electrodes’ potentials as latent variables. Real electrodes’ potentials are regarded as the observable variables. Conductivity distribution is predicted by a maximum likelihood of the possibility model by using EM algorithm. The proposed algorithm is verified by both simulation and experiment. In experiment, medaka fish embryo which is about 1mm in diameter is reconstructed. Comparing with Tikhonov and NOSER regularization method, average ICC is improved 11.54% from 0.7620 to 0.8499 in simulation and improved 5.79% from 0.6978 to 0.7382 in experiment. The algorithm not only performs well in conductivity reconstruction, but also in shape reconstruction. Average position error is decreased 47.57%, average shape error is decreased 24.44% in experiment. It is very suitable for image reconstruction in mini-scale. [ABSTRACT FROM AUTHOR]

Correct detection of peaks in electroencephalogram (EEG) signals is of essence due to the significant correlation of those potentials with cognitive performance and disorders. This paper proposes a novel and non-parametric approach to detect prediction error negativity (PEN) in cognitive conflict processing. The PEN candidates are first located from the input signal via an adaptation of a recent effective method for local maxima extraction, processed in a multi-scale manner. The found candidates are then fused and ranked based on their shape and location-based features. False positives caused by candidates’ magnitude are eliminated by rotating the sorted candidate list where the one with the second-best ranking score will be identified as PEN. The EEG data collected from a 3D object selection task have been used to verify the efficacy of the proposed approach. Compared with the state-of-the-art peak detection techniques, the proposed method shows an improvement of at least 2.67% in accuracy and 6.27% in sensitivity while requires only about 4 ms to process an epoch. The accuracy and computational efficiency of the proposed technique in the detection of PEN in cognitive conflict processing would lead to promising applications in performance improvement of brain-computer interfaces (BCIs). [ABSTRACT FROM AUTHOR]

Electroencephalogram (EEG) electrodes are critical devices for brain-computer interface and neurofeedback. A pre-gelled (PreG) electrode was developed in this paper for EEG signal acquisition with a short installation time and good comfort. A hydrogel probe was placed in advance on the Ag/AgCl electrode before wearing the EEG headband instead of a time-consuming gel injection after wearing the headband. The impedance characteristics were compared between the PreG electrode and the wet electrode. The PreG electrode and the wet electrode performed the Brain-Computer Interface (BCI) application experiment to evaluate their performance. The average impedance of the PreG electrode can be decreased to 43 $\text{k}\Omega $ or even lower, which is higher than the wet electrode with an impedance of 8 $\text{k}\Omega $. However, there is no significant difference in classification accuracy and information transmission rate (ITR) between the PreG electrode and the wet electrode in a 40 target BCI system based on Steady State Visually Evoked Potential (SSVEP). This study validated the efficiency of the proposed PreG electrode in the SSVEP-based BCI. The proposed PreG electrode will be an excellent substitute for wet electrodes in an actual application with convenience and good comfort. [ABSTRACT FROM AUTHOR]

Electrical impedance tomography (EIT) has attracted research interests in imaging of brain function, detection of breast cancer, monitoring of lung function and other medical fields. For EIT, its image reconstruction is largely affected by variation of electrode placement arranged around the detected object. Note that electrode offset is unavoidable in some medical applications, leading to low-quality reconstructed images or even failure of reconstruction. In this paper, a novel method is proposed to improve reconstruction quality in case of electrode offset. By identifying which electrode moves, mismatched boundary voltage caused by movement of electrode is corrected. After mismatch correction, image reconstruction is conducted with total generalized variation regularization method. To demonstrate performance of the proposed method in suppressing impact of electrode offset on reconstruction, extensive work is carried out. Mismatch corrections for four models under a series of counterclockwise or clockwise movements of a certain electrode are studied. The reconstruction results show that the proposed method can effectively improve the image quality under electrode offset. Even in presence of larger electrode offset and noise, reconstructed images have been greatly improved. Quantitative evaluation is also conducted by calculating relative blur radius (RBR). It is shown that RBR values are much closer to 1 compared with results under mismatch conditions. Image reconstruction when two electrodes move is also investigated which further validate the performance of the proposed method. This method is potential for mismatch correction in some medical applications. [ABSTRACT FROM AUTHOR]

The impulse grounding performance of distribution lines tower is the key factor to lightning protection. Few field high-current impulse test researches are conducted on distribution line tower. In this paper, we used a mobile high-current impulse generator to conduct test on a 10 kV distribution line tower. The peak value of the current injection is 6 kA to 16 kA. The impulse impedance and the surface potential distribution are measured and analyzed. Based on the CDEGS software, an equivalent modeling of the experiment was carried out. The influence of soil ionization was taken into account by the method of changing the conductor radius through two rounds of calculation. The simulation and measured results were basically consistent. Experiments have shown that the soil ionization effect has an important impact on lightning performance of distribution line tower. The graphite earthing modules (GEMs) and pulling wires can significantly reduce the impulse impedance of the tower. The potential rise of the earth surface at a distance of 30 m from the tower can reach 1 kV at peak, under an injection of 7.15 kA. [ABSTRACT FROM AUTHOR]

Electrochemical sensor is a promising platform in diagnosing the disorders of nervous and metabolic systems for its feasibility of detecting dopamine (DA) and uric acid (UA). Nevertheless, the reported electrochemical sensors still suffer from unfavorable selectivity and the high limit of detection (LOD). To address these problems, this paper introduced a heterogeneous electrode interface to improve the sensor’s selectivity with differently charged regions. The electrode was prepared on a flexible polyolefin substrate and modified with negatively charged graphene (GP) and electroneutral gold nanoparticles (Au NPs). Experimental results show that the optimal electrode with five layers GP and Au NPs (GP5AuNPs5) was capable of detecting DA and UA in the ascorbic acid (AA)-coexisted solution with minimum interference. The GP5AuNPs5 sensor manifests low LODs ($3 {\sigma } /\text{S}$) of 10 nM and $1.47 {\mu } \text{M}$ for DA and UA, respectively, confirming its feasibility to detect the lowest concentration of the human body. Moreover, the introduction of the Au NPs makes a better separation for current peaks, which might be from the existence of a concentration gradient by electrostatic force difference and an enhanced diffusion from Au NPs. The high-performance sensor with well-separated current peaks is meaningful for detecting DA and UA electrochemically. [ABSTRACT FROM AUTHOR]

In order to meet safety and stability grid-connected requirementsof high-power offshore wind turbines, the 10 MW wind power generation system composed of medium voltage six phase permanent magnet synchronous generator (MVSPMSG) and distributed neutral point clamped (NPC) converter is adopted. On the basis, a maximum power point tracking control (MPPT) method of 10 MW MVSPMSG based on neutral point potential balance is studied in the paper.Firstly, the optimal reference torque of MVSPMSG is calculated according to speed feedback, and the double d-q current control loop of stator is designed based on the doubly fed decoupling. The MPPT of MVSPMSG is realized by the closed-loop combination of torque loop and double d-q current loop. Secondly, in order to suppress the fluctuation of DC neutral point potential, a midpoint potential balance coordinated control method based on modulation coefficients and vector group selection is proposed. The mid-point potential fluctuations is suppressed by adjusting the magnitude of the modulation coefficient in the normal range. The vector group selection method is collaboratively added to the midpoint potential balance control based on small vectors when the modulation coefficient exceeds the limit. Finally, the effectiveness of the proposed MPPT control strategy and midpoint potential balance strategy are verified, which provides a theoretical reference for the control of high-power permanent magnet wind turbine. [ABSTRACT FROM AUTHOR]

High-frequency overvoltages are most dangerous for the insulation of transformer coils. It is because high-frequency pulse voltage creates an uneven distribution of voltage across the windings. The coil's first turns receive a disproportionately high voltage drop, leading to the inter-turn circuit. The paper analyzes the types of lightning pulses and proposes a new suppression method based on the anomalous skin effect in a multilayer material and the design in the form of a coil. The developed device is simulated, and the results of overvoltage monitoring at the substation with the installed high-frequency overvoltage suppression device are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, a simple procedure has been developed to fabricate sensor based on Ni nanoparticles and poly-4-nitroaniline (P4NA) modified glassy carbon electrode (GCE) for simultaneous detection of catechol and hydroquinone. The formed composite film was characterized by scanning electron microscopy (SEM), UV-visible spectroscopy, electrochemical impedance spectroscopy (EIS) and DPV measurements. The modified electrode showed high sensitivity and selectivity towards catechol (CC) and hydroquinone (HQ). Under optimized conditions, the modified GCE showed two sharp redox peaks for CC and HQ in differential pulse voltammetry (DPV) voltammograms with a peak potential separation of 112 mV in pH 7.0 phosphate buffer solution (PBS). The detection limits for HQ and CC were calculated to be 2.3 and $3.9~\mu \text{M}$ , respectively. Good linearity was observed for a concentration range from 10−9–10−4 M and 10−3–10−4 M for CC and HQ respectively. Furthermore, the newly made electrode was successfully evaluated in the detection of both analytes CC and HQ in seawater as a real sample. [ABSTRACT FROM AUTHOR]

China’s railway is experiencing a restructuring from taking fossil fuels as leading resources to electrical energy with renewable energy sources (RESs). As a major consumer of energy, the railway system with RESs integration in China is discussed in this paper, and the relevant applications have been summarized and analyzed. At the same time, the development situations have not yet reached the expected target at present, and China is selecting the route for technical, investment, managerial, market and incentive policy approaches to exploit RESs potential for intelligent railway applications. Furthermore, the next-generation intelligent electrified railway with RESs is proposed and investigated, and the relevant core technologies, systems and incentive policies are summarized and elaborated. Referring to advanced experiences from other countries, the characteristics and objectives of railway energy management system based RESs are also obtained. Based on high-proportion of RESs integration, a win-win situation for railway system and RESs is expected in both economy and environment in China in the future. [ABSTRACT FROM AUTHOR]

In this paper, a molecular imprinted poly $\beta $ cyclodextrin embedded graphite (MIP- $\beta $ -CD@G) electrode is reported, which has been developed for electrochemical determination of capsaicin (CP). MIP- $\beta $ -CD@G has been synthesized by copolymerization of $\beta $ -cyclodextrin ($\beta $ -CD), ethylene glycol dimethacrylate (EGDMA) along with graphite powder and CP molecule in presence of benzoyl peroxide (BP). In the ultra violet – visible (UV-Vis.) spectrum, the disappearance of absorption peak of CP confirms the successful leaching out of the target molecule upon its extraction during the formation of MIP. Cyclic voltammetry (CV) responses revealed that MIP- $\beta $ -CD@G electrode showed remarkable increase in peak current towards electro-oxidation of CP as compared to non-imprinted polymer (NIP) electrode. Under optimized experimental condition, MIP- $\beta $ -CD@G maintained linear relationship between concentration of CP vs. peak current in the range of $0.1~\mu \text{M} - 1.0~\mu \text{M}$ and $1.0~\mu \text{M} - 180~\mu \text{M}$ for the $\beta $ cyclodextrin embedded graphite electrode. The lower limit of detection (LOD) towards CP was found to be $0.007~\mu \text{M}$ (S/N = 3) with the fabricated electrode. The practical applicability of MIP- $\beta $ -CD@G electrode was tested with green chili pepper extracts which yielded satisfactory results. [ABSTRACT FROM AUTHOR]

The years 2020 and 2021 were characterized by a pandemic that made explicit the human fragility and the great value of solidarity during difficult times. Provided this context, during 2021 the journal aligned its scope to be focused on scientific or technical results in agreement with the sustainable goals of the United Nations for Latin America, lying in the areas of electrical energy, computing, and electronics. Additionally, now the journal is focused not only on the exchange of academic ideas involving research papers but also the exchange of computational code, databases, and other tools that may enrich the transfer of knowledge to society. To improve the dissemination of our authors' work, articles completely written in English can now be submitted, and the editorial committee was strengthened to ensure adequate follow-up to these articles. In order to increase the quality of our articles, in 2022, our editorial organization was modified according to the main areas of the Journal: computing, electronics, and electrical energy. Now, every area constitutes a section with its own section editor and its own editorial committee. These sections are intended to apply differentiated requirements on the quality of the articles' content to select those with a higher level of innovation and higher scientific and technical content. [ABSTRACT FROM AUTHOR]

This article proposes a novel flux weakening scheme for five-phase PMSM with active harmonic currents injection. The conventional flux weakening control schemes applied in the five-phase PMSM do not consider the voltage limit drop in the fundamental subspace due to the harmonic current controller. Thus, the derivation between the reference current trajectory and actual current trajectory would cause the current distortion when applying deadbeat current controller (DBCC). This article analyses the precise voltage limit circles considering the voltage drop caused by the resistance and harmonic currents control at first. Then, a feed-forward flux weakening control algorithm is designed to optimize the current trajectory online. The gradient descent method is used to ensure the converge speed and stability of the optimized current trajectory. Thirdly, the peak value of phase currents would be clipped by the harmonic currents to prevent the inverter current limit, where a new non-linear harmonic current controller is designed to precisely control the harmonic currents. Finally, the DBCC and modified SVPWM technology are utilized to generate the duty cycle. The proposed improved flux weakening control strategy is successfully implemented in an interior five-phase PMSM, and the performance demonstrate the effectiveness of this strategy. [ABSTRACT FROM AUTHOR]

Thermal stress of the power semiconductor is one of the most important indicators for the reliability assessment of power electronics-based power systems. The mapping of the Insulated-Gate Bipolar Transistor (IGBT) junction temperature is usually required to analyze the thermal stress and loss dissipation. However, it is difficult to identify inherent mechanisms of the bond-wire and solder layer failure modes in IGBT power modules. In order to solve the problem, an online method to identify inherent mechanisms of the bond-wire and solder layer failure modes in IGBT power modules is proposed. This method can separate the root causes of the bond-wire lift-off and solder layer fatigue by measuring the on-state voltage drop through a sinusoidal loading current based on an H-bridge circuit, together with its corresponding control and measurement. By comparing the on-state voltage drop at the intersection current and the peak current of the converter, the wear-out conditions of the IGBT power modules can be monitored in real-time with the determination of different failure modes. Finally, experimental results are presented in order to verify the effectiveness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Applying 0.3–1.25 kV/cm electric potential gradients to cooled water vapor triggers the copious formation of electrified ice needles, as long as 36 mm. This is completely different from the meager ice formation in the same setup but in the absence of the external field. Needle excess electric charge is evidenced by its attraction toward the electrodes and by its shape change, when the field is withdrawn. These observations are explained considering the effect of the electric potential on ice surface tension, thus decreasing or eliminating the energy barrier to ice nucleation; and the elongated ice habit that allows the accumulation of charge sufficient to create fields higher than those initially applied. Applying this information to other crystallization phenomena in various systems can contribute to improve industrial processes while preventing the consequences of undesired electrification, in industrial plants and products. [ABSTRACT FROM AUTHOR]

Electrical power connectors are critical points of electrical networks. Failure in high-voltage connectors may result in major power outages, safety risks and important economic consequences. Therefore, there is an imperious need to tackle such issue by developing suitable on-line condition monitoring strategies to minimize the aforementioned problems and to ease the application of predictive maintenance tasks. This work develops an on-line condition monitoring method to predict early failures in power connectors from data acquired on-line (electric current and voltage drop across the connector, and temperature) to determine the instantaneous value of the connector resistance, since it is used as a signature or indicator of its health condition. The proposed approach combines a parametric degradation model of the resistance of the connector, whose parameters are identified by means of the Markov chain Monte Carlo stochastic method, which also provides the confidence intervals of the electrical resistance. This fast approach allows an on-line diagnosis of the health condition of the connector, anticipating its failure and thus, easing the application of predictive maintenance plans. Laboratory results emulating the ageing conditions of the connectors prove the suitability and feasibility of the proposed approach, which could be applied to other power products and apparatus. [ABSTRACT FROM AUTHOR]

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]

Voltage drop developed between the grounding electrode under lightning current and distant neutral ground determines the protection efficiency. The peak value of such voltage can be computed from known impulse impedance and current peak value. For the first time, in this letter, general formulas are derived for impulse impedance of horizontal and vertical electrodes valid for any length up to 100 m, soil's resistivity of 30 to 1000 Ωm, and current impulse front time of 0.2 to 10 μs. Waveforms of typical lightning impulses given in IEC standards are used, but it is shown that results are also relevant for other impulse waveforms. Soil ionization effects are taken into account, and the accuracy of the formulas is investigated. New formulas enable an estimate of lightning protection grounding's surge efficiency in a wide range of practical situations. [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]

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]

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]

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]

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]