Voltage Slope Research Articles

Predictive Current Control for Switched Reluctance Motor Based on Local Linear Phase Voltage Model

In this paper, a predictive phase current control (PCC) scheme based on a local linear phase voltage model for a switched reluctance motor is proposed. The current is controlled by regulating the average voltage through PWM, ensuring a fixed switching frequency. A linear model is proposed to approximate the relationship between the voltage and the current slope in a short period. By using the voltage and current slope information in the previous control cycle, the intercept and slope of the model can be identified online. In the previous control cycle, the phase voltage changes from zero to positive or negative DC-link voltage, and then the identified model is used to predict the average voltage required in the next PWM cycle for the actual current so as to accurately track its reference. The effectiveness of the proposed PCC was verified experimentally. The results demonstrate that the proposed control scheme can significantly reduce the current and torque ripples compared to hysteresis control with the same sampling rate. The proposed PCC is easy to implement, does not need to obtain the motor characteristics in advance and is not sensitive to the changes in characteristic parameters caused by motor aging, etc. It is relatively suitable for applications that need to accurately track the given current curve.

Negative Differential Resistance Behavior in n‐Channel Organic Thin‐Film Transistors Based on C60and PTCDI‐C8: Electrical Characterization and Parameter Extraction

Organic thin‐film transistors (OTFTs), based on two n‐type structures of fullerene (C60) andN,N′‐dioctyl‐3,4,9,10‐perylenedicarboximide (PTCDI‐C8), are investigated. The two OTFT devices reveal a negative differential resistance (NDR) behavior in the saturation region of the output curves. The OTFT based on C60shows a more pronounced NDR than that based on PTCDI‐C8. The main origin of the NDR is ascribed to the trapping states. In addition, the contact resistance (Rc) of the two devices, extracted using the developed voltage transition method (Vtrmethod), as well as the obtained values ofRc, are in fair agreement with the experimental values extracted using the total resistance. The device based on C60exhibits a higherRcthan that based on PTCDI‐C8. OTFT parameters, such as transconductance (gm), mobility (μmax), threshold voltage (Vth,), turn‐on voltage (Von), ratio currentIon/Ioff, and subthreshold slope (SS), are obtained in the linear and saturation regimes. The extracted value of SS for the OTFT based on C60is very small compared with that of the device based on PTCDI‐C8, which indicates an increase in the density of trapping states in the C60film.

Small-Signal Stability Modeling for MMC-Based DC Grids With Voltage Slope Control and Influence Analysis of Parameters

In the flexible DC grids, selections of slope coefficients in system level controls and designs of smoothing reactors have a crucial influence on the system stability. In order to obtain their optimal values, a comprehensive small-signal stability model with the DC voltage slope control and smoothing reactors is proposed in this paper. Firstly, the linear state-space model of the entire system based on the small-signal method is deduced according to the coupling equations between the inputs, the outputs, and state variables related to converter stations and the AC sides, controllers, and the DC grid with smoothing reactors. Meanwhile, the influences of the MMC bridge arm circulating current and the capacitor voltage fluctuation of the sub-module are considered in this model. Secondly, the impacts of control parameters, smoothing reactor parameters, and bridge arm inductances are analyzed on the system stability through the Lyapunov stability theory. Finally, the simulation of Zhangbei four-terminal DC grid project in China is established to testify the correctness of the presented small-signal model and the conclusions about the impact of parameters on the system stability. The proposed method will provide some theoretical guidance for the system design and the parameter selection in DC grid applications.

Comparison of Two Control Strategies for VSC-MTDC with Wind Farm

: Two VSC-MTDC control strategies with different combinations of controllers are proposed to eliminate transient fluctuations in the DC voltage stability, resulting from a power imbalance in a VSC-MTDC connected to wind farms. First, an analysis is performed of a topological model of a VSC converter station and a VSC-MTDC, as well as of a mathematical model of a wind turbine. Then, the principles and characteristics of DC voltage slope control, constant active power control, and inner loop current control used in the VSC-MTDC are introduced. Finally, the PSCAD/EMTDC platform is used to establish an electromagnetic transient model of a wind farm connected to a parallel three-terminal VSC-HVDC. An analysis is performed for three cases of single- phase grounding faults on the rectifier and inverter sides of a converter station and of the withdrawal of the converter station on the rectifier side. Next, the fault response characteristics of VSCMTDC are compared and analyzed. The simulation results verify the effectiveness of the two control strategies, both of which enable the system to maintain DC voltage stability and active power balance in the event of a fault. Background: The use of a VSC-MTDC to connect wind power to the grid has attracted considerable attention in recent years. A suitable VSC-MTDC control method can enable the stable operation of a power grid. Objective: The study aims to eliminate transient fluctuations in the DC voltage stability resulting from a power imbalance in a VSC-MTDC connected to a wind farm. Methods: First, the topological structure and a model of a three-terminal VSC-HVDC system connected to wind farms are studied. Second, an analysis is performed of the outer loop DC voltage slope control, constant active power control and inner loop current control of the converter station of a VSC-MTDC. Two different control strategies are proposed for the parallel three-terminal VSCHVDC system: the first is DC voltage slope control for the rectifier station and constant active power control for the inverter station, and the second is DC voltage slope control for the inverter station and constant active power for the rectifier station. Finally, a parallel three-terminal VSC-HVDC model is built based on the PSCAD/EMTDC platform and used to verify the accuracy and effectiveness of the proposed control strategy. Results: The results of simulation analysis of the faults on the rectifier and inverter sides of the system show that both strategies can restore the system to the stable operation. The effectiveness of the proposed control strategy is thus verified. Conclusion: The control strategy proposed in this paper provides a technical reference for designing a VSC-MTDC system for wind farms.

The [Formula: see text]-Wave of the Electroretinogram and Iron-Induced Oxidative Stress: A Model.

In photoreceptors of a dark adapted eye, the inward flux of sodium and calcium ions in the outer segment is balanced by the outward flux of potassium ions. But in the presence of light the creation of cyclic guanosine monophosphate in the outer segment decreases. Due to low concentration of cG (cyclic GMP) the channels in the outer segment open relatively less and thus the influx of calcium ion decreases, leading finally to hyperpolarization of the photoreceptors. We have analyzed theoretically the effect of oxidizing iron ions on the photoreceptors. In order to explain the effects of iron-induced oxidative stress, the different molecules and ions involved in phototransduction are quantified leading to a differential equation for calculating the electroretinogram a-wave voltage. The theoretical results are compared with published experimental data. In the presence of light, the iron ions could push outward the similarly charged calcium ions resulting in a small increase in the amount of inward calcium flux. Again, the presence of iron ions generates Reactive Oxygen Species, and ROS could attract the calcium ions which also increases the calcium flux. This will result in a reduction in the amplitude and slope of the a-wave voltage in the electroretinogram. These results are parametrized in terms of calcium ion concentrations. As the amplitude of the a-wave shows how much electrical signal is produced, its reduction indicates reduction in the visual signal. Thus, the increase in iron ions could explain the reduction in the electrical signal due to iron-induced oxidative stress.

Condition Monitoring of Photovoltaic Cables Based Cross-Linked Polyolefin Insulation Under Combined Accelerated Aging Stresses: Electrical and Mechanical Assessment

The degradation of insulating materials has been recognized as a prime cause of the precocious failure of cable systems. In this research, the role of simultaneous thermal and mechanical stresses on the insulation integrity of cross-linked polyolefin insulation based low voltage photovoltaic cables was studied. The cable samples were subjected to combined thermal–mechanical aging at 120 °C for 120, 189, 258, 396, 636, 876, 1000, and 1120 h aging cycles. The effect of the accelerated aging tests on the insulation integrity of the cross-linked polyolefin was explored by electrical and mechanical techniques. The electrical assessment was based on the measurement of the complex permittivity with frequency variation between 100 mHz to 500 kHz and the measurement of the decay and return voltage slopes. The Shore D hardness as a mechanical testing technique has been carried out. Surprisingly, after 1120 aging hours, the real part of permittivity was almost the same as the pristine case. Also, the imaginary part of permittivity retarded below the pristine case. That was more dominant at frequencies higher than 10 Hz. A good agreement was found between the decay voltage slope and the imaginary permittivity at 1 Hz. Also, between the return voltage slope and the real permittivity. The cable hardness showed anomalous behavior with aging. This shows the ability of the cross-linked polyolefin to recover its mechanical properties when subjected to elevated temperature.

Influence of GaN/ZrO2 interfacial layer defects on 8-nm GaN-SOI-FinFET for reliable RFIC design

This work presents, the reliability of GaN/ZrO2 (Gallium Nitride/Zirconium dioxide) interfacial layer defects on 8-nm Gallium Nitride (GaN) Silicon-on-Insulator (SOI) FinFET (GaN-SOI-FinFET). Positive, negative, and neutral interface trap charges are considered in all the results and simultaneously compared with SOI-FinFET with an 8-nm gate length for the evaluation of device reliability. It is found that the proposed device is more immune to interfacial trap defects and reflected in terms of drain current (Id), device efficiency (gm/Id), transconductance (gm), subthreshold slope (SS), electric field, surface potential, and threshold voltage at an ultra-low voltage (VDS = 0.1 V). Further, the performance degradation of GaN-SOI-FinFET is calculated by various linearity figures of merits (FOMs) such as higher-order transconductance coefficients (gm2 and gm3), voltage, and current intercept points (VIP2, VIP3, and IIP3). Moreover, device reliability is also performed by evaluating intermodulation and harmonic distortions (IMD3, HD2, and HD3). The proposed device shows better reliability in the presence of interfacial traps and paves the way for high-performance low power, high linearity, and lesser harmonic distortions performance for RFIC design.

Negative Capacitance Dual Electrode Junctionless TFET Based on Si Doped HfO 2 Ferroelectric Layer: Proposal and Optimization

This work reports negative capacitance dual electrode junctionless tunnel field effect transistor (NC-DE-JLTFET) based on Si doped HfO 2 ferroelectric (FE) layer as gate-stack. This FE layer is sandwiched between conventional gate dielectric layer and gate metal electrode. As the domains of FE get aligned due to polarization in the applied electric field directions it realizes intrinsic voltage amplification. This facilitates the smaller voltage swing in the gate voltage resulting in a larger swing in drive current. This enhances gate controlability, improves scalability, lowers threshold voltage and steepers sub-threshold slope (SS). However the most crucial designing aspect of negative capacitance (NC) based device is stabilizing the net capacitance of the structure otherwise it can cause system instability due to the NC behavior. In order to stabilize this NC effect here optimization of FE layer thickness has been carried out by parametric sweep optimization. The study reported minimum SS as 20 mV/dec with FE thickness of 2.5 nm. As JLTFET is a dopingless structure, source and drain side dielectric oxide thicknesses dictate the source and drain side induced doping, respectively. Hence the device performance estimation in terms of these thickness variations is also presented here in detail.

GaN-Based Full-Bridge Converter With Digitally Adjustable Voltage Slopes for Characterization of Interwinding Insulation Properties of Magnetic High-Frequency Power Components

GaN-Based Full-Bridge Converter With Digitally Adjustable Voltage Slopes for Characterization of Interwinding Insulation Properties of Magnetic High-Frequency Power Components

Lifetime of Catalyst under Voltage Cycling in Polymer Electrolyte Fuel Cell Due to Platinum Oxidation and Dissolution

The durability of a platinum catalyst in a polymer electrolyte membrane fuel cell is studied at various operating conditions with respect to the different electric potential difference (called voltage) applied in accelerated stress tests. The electrochemical reactions of Pt ion dissolution and Pt oxide coverage of the catalyst lead to the degradation of platinum described by a one-dimensional Holby–Morgan model. The theoretical study of the underlying reaction–diffusion system with the nonlinear reactions is presented by numerical simulations which allow to predict a lifetime of the catalyst under applied voltage cycling. The computer simulation investigates how the Pt mass loss depends on the voltage slope and the upper potential level in cycles.

Ultra Sensitive Label-Free Detection of Biomolecules Using Vertically Extended Drain Double Gate Si₀.₅Ge₀.₅ Source Tunnel FET

This work reports a vertically extended drain double gate Si0.5Ge0.5 source tunnel FET for the biomolecules detection using its electrical properties modulation in presence of biomolecules like cell, DNA, protein, etc. The reported biosensor has a dual source of Si0.5Ge0.5 and two cavities above each source-channel interface for the immobilization of biomolecules. This immobilization modulates the screening/tunneling length and energy range available for tunneling due to the dielectric constant and charge density variations of the biomolecules. The dual cavity structure increases the control of biomolecules on the source to channel tunneling probability and thus realizes an increased control on electrical performance parameters of the biosensor enabling it to have a higher sensitivity towards the biomolecules. Further, the cavity length of the reported biosensor is kept as 45 nm making it suitable for large sized biomolecules and polymers detection also. Our study demonstrates that the reported biosensor structure is resilient towards the process variations and temperature effects. Moreover, the effect of dielectric modulation and charge density modulation has also been analyzed in terms of the variation in the drive current, ON state current, threshold voltage, transconductance, and sub-threshold slope (SS). The sensitivity of the reported biosensor is also compared with the existing biosensors and it is found to be highly sensitive.

A Supply Voltage Noise Immunity Enhancement Design for High-Voltage Gate Driver IC Based on Bootstrap Circuit

One important design aspect of a high-voltage gate driver integrated circuit (HVIC) is safety because the failure operation such as latch-on failure may cause severe damage to the system and may pose physical harm to the user. In the HVIC, a noise on the high-side supply voltage was considered as the main source of failure operation, however, a low-side supply voltage noise also can cause latch-on failure to the high-side circuitry. In this brief, the failure caused by the high-side as well as low-side supply voltage noise is analyzed, and a supply voltage noise immunity enhancement design for HVIC is described. The HVIC has been implemented in a 1.2 μm 600 V BCDMOS process. The proposed design shows a latch-on free operation from the various slope of the supply voltage drops while the conventional design shows shoot-through failure by latch-on failure. The approach is well suited for the harsh supply voltage environment such as the automotive application.

Dielectric Modulated Junctionless Biotube FET (DM-JL-BT-FET) Bio-Sensor

In this manuscript, an analytical model has been demonstrated for Dielectric Modulated Junctionless Biotube FET (DM-JL-BT-FET) as a sensor. The Junctionless Biotube FET based sensor has been compared with Nanowire FET under similar bio-molecule conditions. It has been demonstrated that Dielectric Modulated Junctionless Biotube FET shows much higher efficiency in Bio-sensing and poses superior device performance characteristic in terms of higher sensitivity, higher drift in drain current, transconductance, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> ratio, Subthreshold Slope and Threshold voltage. The hole concentrations have also been investigated under different biomolecule conditions. Two different biomolecule conditions have been considered in our analysis viz., firstly, varying the biomolecule concentrations and secondly, inserting different biomolecules namely DNA, Biotin and Hydroprotein. Improved bio sensing is observed in Junctionless Biotube FET because of superlative gate control over the channel, owing to architecture of Biotube FET. The analytical results have also been modelled for DM-JL-BT-FET by finding a solution to the 2-D Poisson equation in accordance with the boundary conditions. The analytical results are much in coherence with the results obtained from the simulator.

한류기 보호 MTDC시스템에 과전류 계전기적용을 위한 전압기울기 방향 보정 연구

In the DC system, the fault current is quite fast and rises significantly due to capacitor discharge. Due to this, DC fault conditions must be cut off more quickly and accurately than AC. However, DCCB is more complicated to operate and more expensive than AC system circuit breaker. Therefore, it is necessary to introduce a superconducting fault current limiter, and the trip delay may occur in the overcurrent relay due to the introduction of the superconducting fault current limiter. To prevent this, a correction algorithm is needed. In this paper, an algorithm that considers the voltage slope and the direction of the current is applied to effectively limit the fault current through a superconducting fault current limiter, and a method to prevent the malfunction of the circuit breaker.

A Sustainable Energy Distribution Configuration for Microgrids Integrated to the National Grid Using Back-to-Back Converters in a Renewable Power System

A desire to produce power in microgrids has grown as the demand for electricity has expanded and the cost of installing modern transmission lines over long distances has become infeasible. As such, microgrids pose DC/AC harmonic distortion losses to the voltage supply that eventually fluctuate the output voltage. The key takeaways that this study presents are: (a) a configuration for microgrids integrated to the national grid using back-to-back converters in a renewable power system is achieved; (b) different scenarios of various schemes of sustainability of the power management in microgrids are analyzed; and (c) the reliable and stable network output power distribution is achieved. In this, the proposed control configuration provides space for construction and stability of the power system with sustainability of the power management. The results show that this current configuration works and stabilizes the network in the shortest time possible, and that the DC connection voltage is regulated and maintains reliable network output despite declining slope controllers, DC power and voltage, and power electronic back-to-back converters. Overall, the simulation results show that the proposed system shows acceptable performance under different scenarios. The accuracy of the results is validated with mathematical formulation simulation using MATLAB software. This system can be utilized in distant regions where there is no power grid or in areas where, despite having a power infrastructure, renewable energies are used to supply the output load for the majority of the day and night.

A Novel DSP-Based MPPT Control Design for Photovoltaic Systems Using Neural Network Compensator

In this study, based on the slope of power versus voltage, a novel maximum-power-point tracking algorithm using a neural network compensator was proposed and implemented on a TI TMS320F28335 digital signal processing chip, which can easily process the input signals conversion and the complex floating-point computation on the neural network of the proposed control scheme. Because the output power of the photovoltaic system is a function of the solar irradiation, cell temperature, and characteristics of the photovoltaic array, the analytic solution for obtaining the maximum power is difficult to obtain due to its complexity, nonlinearity, and uncertainties of parameters. The innovation of this work is to obtain the maximum power of the photovoltaic system using a neural network with the idea of transferring the maximum-power-point tracking problem into a proportional-integral current control problem despite the variation in solar irradiation, cell temperature, and the electrical load characteristics. The current controller parameters are determined via a genetic algorithm for finding the controller parameters by the minimization of a complicatedly nonlinear performance index function. The experimental result shows the output power of the photovoltaic system, which consists of the series connection of two 155-W TYN-155S5 modules, is 267.42 W at certain solar irradiation and ambient temperature. From the simulation and experimental results, the validity of the proposed controller was verified.

제안한 Half Bridge Sub-module을 통한 Modular Multilevel HVDC 시스템의 DC 고장 사고에 대한 차단

In power transmission of multi-system systems based on renewable energy today, high voltage DC transmission based on modular multi-level converter has many advantages in terms of high power quality and cost. Here, protection against external factors such as faults and rapid system recovery are very important issues for stable power transmission. In this paper, a method for system protection from the line to line DC faults on the grid is poposed. The proposed method is a method of suppressing the fault current by forming an inverse voltage slope through the fault ride through (FRT) method in the AC link and converter system according to a command operated in the event of a fault in the path of the fault current formed. The proposed method can be composed of semiconductor devices that are reduced compared to the existing sub-module models. For the verification of the paper, simulation through PSIM was used.

Investigation of Effects of Short-term Thermal Stress on PVC Insulated Low Voltage Distribution Cables

The main aim of this study is to investigate the ageing process of Low Voltage cables in smart grid. In addition, the behavior of ageing phenomenon has also been investigated. The Low Voltage cable networks were developed decades ago and it is of utmost importance to make comprehensive study over the health of existing Low Voltage cable networks so as to avoid any unprecedented damage. Incessantly increasing energy demand and distributed generation makes it among top priorities to investigate the ageing process of Low Voltage cables.The effect of thermal stress over dielectrics was investigated as a part of research. To be able to determine these effects the measurements were done on PVC insulated (both cores and jacket) cable by measuring tanδ (dissipation factor), capacitance, return voltage of cable and hardness of insulations. In order to determine thermal effects on dielectric, the measurements were done in different ageing temperature ranges i.e. at 110 °C, 125 °C and 140 °C.The results of this study support the expectations. The mechanical and the electrical parameters of cable insulation are affected by thermal stress. The dissipation factor and the hardness are increased while the decay voltage slope ( Sd ) is decreased by ageing.

Parameterization of Debye Model for Dielectrics Using Voltage Response Measurements and a Benchmark Problem

The Voltage Response measurement since its introduction in the 1960s has been used successfully for the diagnostics of electrical insulation. The method is based on two quantities of decay and return voltage slopes and can be used to study the conduction and polarization processes inside the insulation. Extended Voltage Response method, being an advanced version of the Voltage Response measurement helps in further studying the polarization process by using a large polarization spectrum and hence dielectric relaxation processes. These dielectric relaxation processes can be modeled by the Debye model. Since as most of the techniques used for diagnostic purpose does not give the information about the conduction and polarization processes separately, it is difficult to determine the R-C parameters of the Debye model. The Voltage Response technique is very useful in this regard because of the two voltage slopes. The paper shows a novel experimental benchmark for testing the function fitting methodologies of the Voltage Response methodologies, which helps in determining the R-C parameters. Moreover, the problem can be used for testing the novel genetic, evolutionary algorithms, where benchmarking is an actual challenge. The proposed nonlinear function fitting method uses the genetic algorithms via the Ārtap framework, which lets it possible to select the most accurate optimization algorithm from the provided list of the algorithms and achieve better fitting precision, faster calculation time or more powerful processing ability.

Directional Correction of Over-Current Relay Using Voltage Slope in Multi Terminal DC System With SFCL

In the DC system, a larger fault current flows due to capacitor discharging than in an AC system. In the event of a fault in the MTDC (multi-terminal DC), although the magnitude of the current flowing through each DCCB (DC circuit breaker) varies depending on the fault location, all capacitors in MTDC may discharge and all DCCB may interrupt. In this paper, the trigger type SFCL (superconducting fault current limiter) were constructed to limit large fault current, and DC OCR (overcurrent relay) was designed to prevent interrupting malfunction according to the impact of SFCL. When the fault current was small by operation of SFCL, the DCCB did not interrupt or trip time is delayed. These problems cause malfunction even when DC OCR is applied. Therefore, DC OCR requires an additional correction method. In this paper, a new correction method was proposed in consideration of the current direction and voltage slope. The simulation was conducted according to four cases, and the proposed OCR correction was verified to eliminate malfunctions through case studies.