Gating Signals Research Articles

Overvoltage Suppression Scheme for Minimized Snubber Requirements in MVDC Solid-State Breakers With Series-Connected IGBTs

Solid-state dc breakers are the ultimate technology for protecting medium-voltage dc grids having equipment vulnerable to excessive fault-current stress, due to the very short fault-clearing times. A typical implementation of such breakers is based on insulated gate bipolar transistors (IGBTs). However, as the rated voltage of the grid increases, series connection of IGBTs is inevitable and impose challenges on transient and steady-state blocking voltage distribution. This article presents a novel voltage-balancing scheme that combines passive resistive-capacitive-diode (RCD) snubber circuits and a gate driver containing a gate-current balancing magnetic-core. The proposed concept aims at minimizing the required snubber capacitances, which may be high. The impact of the proposed configuration on the breaker design and its performance are studied under different fault scenarios. Using the proposed breaker configuration, the snubber capacitance has been reduced by up to 60%. Besides, both simulations and experimental results reveal the mitigation of high peak voltage stress across the early turned-off IGBTs under gate signal propagation delays.

Simple and Seamless PWM Scheme of Isolated Bidirectional AC–DC Converter for Reducing Voltage Spike

This article proposes an improved modulation scheme based on unipolar sinusoidal pulsewidth modulation for a single-phase single-stage isolated bidirectional ac–dc converter. A direct ac–ac conversion system connected with a high-frequency transformer typically suffers from high-voltage spikes because of the leakage inductors of the high-frequency transformer and the grid filter inductors, resulting in reduced reliability and large power losses. The proposed modulation scheme can eliminate the high-voltage spikes in bidirectional power flow without the use of additional circuits while realizing zero-voltage switching. In addition, because the proposed method does not require individual gate control of the bidirectional power switches, the generation of gate signals can be simplified using the proposed modulation scheme. A simulation model and a 1.2 kW grid-connected ac–dc converter based on silicon-carbide metal–oxide–semiconductor field-effect transistors are implemented to validate the effectiveness of the proposed modulation scheme.

A Novel Open-Circuit Fault Detection and Location for Open-End Winding PMSM Based on Differential-Mode Components

Detecting and locating the open-circuit (OC) fault of an insulated-gate bipolar transistor (IGBT) rapidly and accurately is very important to improve the security and reliability of the drive system. However, due to the symmetry of the dual-inverter topology, it is difficult to achieve fault detection for open-end winding permanent magnet synchronous motor (PMSM). Thus, this article proposes a fault diagnosis technology for open-end winding PMSM fed by a dual inverter with a common dc bus. In this method, the faulty phase and the faulty case are identified by the average value of the output of the closed-loop controller, which is used to eliminate the differential-mode current in the system. Then, the faulty phase is isolated by removing the gate signals. Finally, the faulty IGBT is located by restructuring the faulty phase and analyzing the current of the faulty phase. In this method, the OC fault can be detected and the faulty IGBT can be located accurately. Experimental results are shown to validate the proposed detection method.

Fetal Cardiovascular MRI - A Systemic Review of the Literature: Challenges, New Technical Developments, and Perspectives.

Fetal magnetic resonance imaging (MRI) has become a valuable adjunct to ultrasound in the prenatal diagnosis of congenital pathologies of the central nervous system, thorax, and abdomen. Fetal cardiovascular magnetic resonance (CMR) was limited, mainly by the lack of cardiac gating, and has only recently evolved due to technical developments. A literature search was performed on PubMed, focusing on technical advancements to perform fetal CMR. In total, 20 publications on cardiac gating techniques in the human fetus were analyzed. Fetal MRI is a safe imaging method with no developmental impairments found to be associated with in utero exposure to MRI. Fetal CMR is challenging due to general drawbacks (e. g., fetal motion) and specific limitations such as the difficulty to generate a cardiac gating signal to achieve high spatiotemporal resolution. Promising technical advancements include new methods for fetal cardiac gating, based on novel post-processing approaches and an external hardware device, as well as motion compensation and acceleration techniques. Newly developed direct and indirect gating approaches were successfully applied to achieve high-quality morphologic and functional imaging as well as quantitative assessment of fetal hemodynamics in research settings. In cases when prenatal echocardiography is limited, e. g., by an unfavorable fetal position in utero, or when its results are inconclusive, fetal CMR could potentially serve as a valuable adjunct in the prenatal assessment of congenital cardiovascular malformations. However, sufficient data on the diagnostic performance and clinical benefit of new fetal CMR techniques is still lacking. · New fetal cardiac gating methods allow high-quality fetal CMR.. · Motion compensation and acceleration techniques allow for improvement of image quality.. · Fetal CMR could potentially serve as an adjunct to fetal echocardiography in the future.. · Knapp J, Tavares de Sousa M, Schönnagel BP. Fetal Cardiovascular MRI - A Systemic Review of the Literature: Challenges, New Technical Developments, and Perspectives. Fortschr Röntgenstr 2022; 194: 841 - 851.

A Modified Seven-Level Inverter with Inverted Sine Wave Carrier for PWM Control

The conventional multilevel inverter necessitates more active switching devices and high dc-link voltages. To minimalize the employment of switching devices and dc-link voltages, a novel topology has been proposed. In this paper, a novel minimum switch multilevel inverter is established using six switches and two dc-link voltages in the proportion of 1 : 2. In addition, the proposed topology is proficient in making seven-level voltages by appropriate gate signals. The PWM signals were produced using several inverted sine carriers and a single trapezoidal reference. When compared to other existing inverters, this configuration needs fewer components, as well as fewer gate drives. Furthermore, this module can generate a negative level without the use of a supplementary circuit such as an H-Bridge. As a result, overall cost and complexity are greatly reduced. The proposed minimum switch multilevel inverter operation is validated through simulations followed by experimental results of a prototype.

A Study of Inverter Open-Circuit Fault in Grid Connected Photovoltaic Systems: Influence on Output Power and Detection Method

The paper presents an investigation of single switch open-circuit fault in the inverter of photovoltaic (PV) systems. An IGBT two-level three-phase inverter which is used to connect the photovoltaic system to the main grid is considered in this application. First, the fault is created by modifying the control gate signal sent to the inverter. Second, the operation of a PV system is simulated under various levels of the irradiation under both healthy state and the condition of single switch open-circuit fault. The output powers generated by the system are then compared to show the influence of fault occurrence. Based on the DC current of the inverter, fault detection method is recommended. Investigation results show that the fault strongly affects the output power and that can be detected by judging the amplitude of three first orders of the AC side fundamental frequency.

Implementation of SVM Based Multi-Level Inverter for Grid Connected PV System

Multilevel inverters are a novel type of dc–ac converter designed for medium and high voltage and power applications. Cascaded multilevel inverters are the most common inverters used in renewable energy applications. Despite the numerous advantages, the presence of extra circuit components in the design causes reliability concerns with these inverters. Researchers have faced a significant difficulty in constructing inverters with improved dependability by lowering total harmonic distortion (THD). This paper proposes a concept of Grid connected PV system with multilevel inverter topology. The PV system is implemented by using mathematical analysis and MPPT based dc-dc boost converter is used to improve the performance of PV system. In this paper, perturb and observe MPPT technique is implemented. For obtaining better harmonic distortions and proper synchronization with grid a multi-level inverter is implemented. This paper proposes a novel multilevel inverter topology for renewable energy operations which produces 31 and 51 level output voltages. The conventional topology is formed with 10 IGBT switches. A closed loop controller with sinusoidal pulse width modulation technique is implemented to generate gate signals required for 31-Level converter. The 51-Level converter is modelled with 8-IGBT switches and 4-diodes, also space vector and sinusoidal pulse width modulation techniques are used to generate the gate signals for switches. This proposed system is tested and verified in MATLAB and a comparative analysis made between sinusoidal and space vector modulation in 51-Level topology.

Fetal cardiovascular blood flow MRI: techniques and applications.

Fetal cardiac MRI is challenging due to fetal and maternal movements as well as the need for a reliable cardiac gating signal and high spatiotemporal resolution. Ongoing research and recent technical developments to address these challenges show the potential of MRI as an adjunct to ultrasound for the assessment of the fetal heart and great vessels. MRI measurements of blood flow have enabled the assessment of normal fetal circulation as well as conditions with disrupted circulations, such as congenital heart disease, along with associated organ underdevelopment and hemodynamic instability. This review provides details of the techniques used in fetal cardiovascular blood flow MRI, including single slice and volumetric imaging sequences, post-processing and analysis, along with a summary of applications in human studies and animal models.

Spatiotemporal reconstruction method of carotid artery ultrasound from freehand sonography.

4D reconstruction based on radiation-free ultrasound can provide valuable information about the anatomy. Current 4D US technologies are either faced with limited field-of-view (FoV), technical complications, or cumbersome setups. This paper proposes a spatiotemporal US reconstruction framework to enhance its ability to provide dynamic structure information. We propose a spatiotemporal US reconstruction framework based on freehand sonography. First, a collecting strategy is presented to acquire 2D US images in multiple spatial and temporal positions. A morphology-based phase extraction method after pose correction is presented to decouple the compounding image variations. For temporal alignment and reconstruction, a robust kernel regression model is established to reconstruct images in arbitrary phases. Finally, the spatiotemporal reconstruction is demonstrated in the form of 4D movies by integrating the US images according to the tracked poses and estimated phases. Quantitative and qualitative experiments were conducted on the carotid US to validate the feasibility of the proposed pipeline. The mean phase localization and heart rate estimation errors were 0.07 ± 0.04s and 0.83 ± 3.35bpm, respectively, compared with cardiac gating signals. The assessment of reconstruction quality showed a low RMSE (<0.06) between consecutive images. Quantitative comparisons of anatomy reconstruction from the generated US volumes and MRI showed an average surface distance of 0.39 ± 0.09mm on the common carotid artery and 0.53 ± 0.05mm with a landmark localization error of 0.60 ± 0.18mm on carotid bifurcation. A novel spatiotemporal US reconstruction framework based on freehand sonography is proposed that preserves the utility nature of conventional freehand US. Evaluations on in vivo datasets indicated that our framework could achieve acceptable reconstruction performance and show potential application value in the US examination of dynamic anatomy.

SOLAR PV SYSTEM WITH MULTI-LEVEL INVERTER USING PI AND FUZZY LOGIC CONTROLLER

This paper presents a single-phase multi-string Nine-level PV inverter topology for grid-connected photovoltaic (PV) systems with a novel PWM control and fuzzy logic scheme. The Multilevel inverters are extensively used due to their increased power rating reduced EMI, improving harmonic performance. Multilevel inverters are switched at low switching frequency when compared to two level inverters, a single-phase multi-string nine-level PV inverter topology for grid-connected photovoltaic (PV) systems using novel PWM control Technology. A photovoltaic (PV) system generates electricity by direct conversion. The PV strings are cascaded together in parallel configuration and connected to a Nine-level inverter to generate output voltage. Two reference sinusoidal signals are identical to each other with an offset equivalent to the amplitude of the triangular carrier signal were used to generate gate signals for the nine level inverter switches and it is to implement this PWM using PI current control algorithm. The proposed nine level inverter offers much less THD and can operate at near unity power factor. the frequency of it will be 50Hz and from the result we minimizes the number of components and devices as well as switching losses are reduced when compared to the conventional multilevel inverter topology and its interconnects for grid utilization. Fuzzy Logic Control (FLC), originating from control theory focused on mathematical representations of the open-loop mechanism to be controlled, is an integral aspect of fuzzy reasoning. Fuzzy Logic Control has been successfully extended to a wide range of practical issues, including warm water control, robot control, heat exchange, traffic junction control, cement kiln control, vehicle speed control, automotive engineering, and mcar parking and turning, power system and nuclear reactor, on-line shopping, washing machines, etc. The validity of the proposed inverter is verified through simulation andcompared with other technique. The output voltage will be in the form of stepped waveform. The proposed system produces less THD and reduction of steady state time KEYWORDS –Maximum Power Point Tracking(MPPT) algorithm, Boost Converter, FLC contreoller, PWM technique.

A New Analytical MPPT-Based Induction Motor Drive for Solar PV Water Pumping System With Battery Backup

In this article, an analytical method is presented to achieve maximum power point tracking (MPPT) for a solar photovoltaic (PV) array-based water pumping system comprising of an induction motor drive (IMD). The gating signals are generated using the space vector pulsewidth modulation (SVPWM) method for three-phase inverter. This analytical MPPT control (AMPPTC) scheme exhibits fast dynamic performance and minimum overshoot with the IMD-based water pumping system. Additionally, the AMPPTC scheme provides absolute steady-state robustness under variations in solar irradiance/parameters that improves the stability of the system under a wide speed range of IMD and makes the system insensitive toward parameter variations. The dc-link voltage regulation is assured by three-phase inverter, and MPPT regulation is achieved by the boost converter. This two-stage PV system, with MPPT controlled boost converter and SVPWM-based three-phase inverter operating the pump, is modeled and simulated in Simulink environment of MATLAB. The performance and robustness of the AMPPTC-based PV water pumping system are corroborated through the laboratory experimentation.

A Review of Indirect Time-of-Flight Technologies

Indirect time-of-flight (iToF) cameras operate by illuminating a scene with modulated light and inferring depth at each pixel by combining the back-reflected light with different gating signals. This article focuses on amplitude-modulated continuous-wave (AMCW) time-of-flight (ToF), which, because of its robustness and stability properties, is the most common form of iToF. The figures of merit that drive iToF performance are explained and plotted, and system parameters that drive a camera’s final performance are summarized. Different iToF pixel and chip architectures are compared and the basic phasor methods for extracting depth from the pixel output values are explained. The evolution of pixel size is discussed, showing performance improvement over time. Depth pipelines, which play a key role in filtering and enhancing data, have also greatly improved over time with sophisticated denoising methods now available. Key remaining challenges, such as ambient light resilience and multipath invariance, are explained, and state-of-the-art mitigation techniques are referenced. Finally, applications, use cases, and benefits of iToF are listed.

Duty Cycle Control Strategy for Dual-Side LCC Resonant Converter in Wireless Power Transfer Systems

The dual-side inductor–capacitor–capacitor (LCC) topology circuit has been widely adopted in wireless power transfer (WPT) systems due to its constant output current characteristic. However, most conventional control methods need specific synchronization techniques between the primary and secondary sides to avoid the oscillation in the system, which increases the cost and control complexity. To solve this issue, this article proposes a new duty cycle control (DCC) strategy for a dual-side LCC resonant converter with a semibridgeless active rectifier (SAR). With such a control strategy, gate signals of the primary- and secondary-side circuits do not need to be synchronized, which could reduce the complexity and the cost of the WPT system. Besides, the switching frequency of the secondary side can be decreased significantly. This article first presents the modal analysis of phase shift control (PSC) and DCC. Then, generalized state-space averaging (GSSA) modeling with PSC and the hybrid average modeling with DCC are performed. In addition, controllers’ design for both strategies is conducted to achieve the constant output voltage. Finally, the eigenvalues’ analysis is used to determine the stability region of the WPT system. The theoretical analysis has been validated by both simulation and experimental results.

Total Suppression of High-Frequency Transient Oscillations in Dual-Active-Bridge Series-Resonant Converter by Trajectory-Switching Modulation

Dual-active-bridge series-resonant converter (DABSRC) is increasingly used in many emerging power electronics applications requiring fast dynamic responses. However, under conventional transient phase-shift modulation strategy, DABSRC generally suffers from large-amplitude transient oscillations when its phase-shift angle is changed abruptly by a high-gain controller. These oscillations occur at the beat frequency, which results from the interaction between the switching-frequency and resonant-frequency components in the series-resonant tank during transient states. Besides incurring high voltage and current stresses on the power-stage devices, these transient oscillations also span many switching cycles between the original and new steady states and cause perturbations to the output voltage of DABSRC, thereby degrading its dynamic performance and output voltage quality. To mitigate these problems, a new transient modulation strategy, known as trajectory-switching modulation (TSM), is proposed for achieving an accurate and computationally efficient trajectory planning of the resonant voltages and currents of DABSRC during transient states, and its basic operation is to govern the transient switching patterns of the gating signals according to a simple set of closed-form equations. The proposed TSM strategy can guarantee convergence to the next new steady state within about one switching cycle and avoid needing costly sensors and complex computation for implementation, and it is inherently compatible with high-gain controllers for realizing oscillation-free fast dynamic responses.

An adaptive TS‐fuzzy model based RBF neural network learning for grid integrated photovoltaic applications

In this research work, an adaptive TS-fuzzy based RBF neural network (ATSFRBFNN) algorithm based maximum power point tracker (MPPT) is employed for grid integrated photovoltaic (PV) system. The novel learning algorithm provides accurate and rapid PV power tracking under fluctuating solar insolation. However, an improved damping circulating current limiting inverter controller is employed to generate gating signal of voltage source inverter and to deliver reduced harmonic constant, less power loss, mitigation of power quality issues regulation of Dc-link voltage utilization for grid integrated PV system under steady, and transient weather conditions. The experimental results justify the improved system performance under varying operating conditions. The behaviour of novel hybrid PV MPPT structure is compared with TS-fuzzy, RBFNN, and GA-RBF for higher tracking efficacy, least tracking deviation, accurate responses, and zero steady-state power oscillation around MPP region.

Single-Molecule Sensing of an Anticancer Therapeutic Protein-Protein Interaction Using the Chemically Modified OmpG Nanopore.

Nanopore sensors are a highly attractive platform for single-molecule sensing for sequencing, disease diagnostics, and drug screening. Outer membrane protein G (OmpG) nanopores have advantages for single-molecule sensing owing to their rigid monomeric structure, which comprises seven flexible loops, providing distinct gating patterns upon analyte binding. Blocking of the protein-protein interaction between B-cell lymphoma-extra-large (Bcl-xL) and the BH3 domain of Bcl-2 homologous antagonist/killer (Bak-BH3) has been reported as a promising strategy for anticancer therapy. Here, we characterized the interaction between Bcl-xL and Bak-BH3 as well as its inhibition by a small-molecule inhibitor using click chemistry-based Bak-BH3 peptide-conjugated OmpG nanopores. The binding of Bcl-xL to Bak-BH3 generated characteristic gating signals involving significant changes in the amplitudes of noise and gating parameters such as gating frequency, open probability, and durations of open and closed states. Notably, specific inhibition of Bcl-xL by the small-molecule antagonist, ABT-737, led to the recovery of the noise and gating parameters. Collectively, these results revealed that the chemically modified OmpG nanopore can serve as a valuable sensor platform for ultrasensitive, rapid, and single-molecule-based drug screening against protein-protein interactions, which are therapeutic targets for various diseases.

Ferroelectric ion gel-modulated long-term plasticity in organic synaptic transistors

Motivated by the massive parallelism of the human neural system, an artificial neuromorphic system may emulate neural activities. Previous research endeavors have been devoted to mimicking various biological synaptic functions using ion gel-based organic synaptic transistors (IGOSTs). The design scheme for these devices has been pivoted on strategies for evaluating various biological synaptic functions, such as short-term plasticity and pulse paired facilitation. However, the implementation of the IGOSTs for mimicking long-term plasticity (LTP) remains challenging because of expeditious ion de-doping from the semiconductor channel after turning off the stimulus gate signal. Herein, we present a novel ferroelectricity-enabled ion gel dielectric platform, which is referred to as ‘ferro-iongel,’ capable of implementing a longer retention time of the pre-synaptic signal with low power consumption in the IGOSTs. The envisioned material platform comprises a blend of ferroelectric polymer, elastomer matrix, and ionic liquid. Consequently, highly reliable LTP at different applied voltages has been accomplished with the emergence of electric double layer (EDL) and the partial polarization switching of ferroelectric dipoles. The new class of the dielectric material suggested herein is anticipated to contribute toward the practical realization of LTP in the IGOSTs for the demonstration of future human-machine interfaces.

Robust adaptive direct speed control of PMSG-based airborne wind energy system using FCS-MPC method

Electricity generation using airborne wind energy system (AWES) tends to be more efficient than that of conventional wind turbines due to their ability at extracting higher speeds from wind at higher altitudes by the tethered kite generator system (TKGS). The speed regulation of a permanent synchronous machine (PMSM) attached to a kite to maximize harvested power from wind is the topic of the present research. To track the optimal speed produced by TKGS, a finite-control-set model predictive control (FCS-MPC) with a new cost function is directly employed to generate appropriate gate signals for a 3-level neutral point clamped (3-L NPC) inverter that drives a PMSM. A novel adaptive algorithm is also provided for adjusting the weight coefficients of the cost function to improve the system’s performance across a wider range of change in the operating conditions. Moreover, a terminal sliding mode disturbance observer (TSMDO) is designed to estimate the load torque. A terminal sliding mode speed controller (TSMSC) is also used to produce the current reference for the optimizing algorithm in FCS-MPC. The proposed control scheme eliminates the need for a cascade structure while significantly reduces current deformation and torque oscillations. Additionally, the controller operates as fast as a traditional direct speed controller without the use of a cascade structure and is more robust against parameter uncertainties. To illustrate the success of the suggested controller, the results of simulations are presented in MATLAB/SIMULINK® software. The performance of the proposed technique is evaluated in three situations which simulates a grid-connected PMSM fed by a back to back 3-L NPC. In the first scenario, it is demonstrated that the suggested technique performs well when the system’s operational conditions vary. The performance of the adaptive tuning mechanism of the cost function weight factors is investigated in the second scenario, which takes into account model parameter uncertainty. The impacts of the disturbance observer (DO) on the system performance are explored in the final scenario, and it is discovered that the disturbance observer may increase the speed response and DC link voltage tracking performance. All of the simulation results show that the new technique outperformed the traditional FSC-MPC.

Isolated seven‐level inverter for grid‐connected power systems with predictive control method

AbstractA novel isolated 7‐level (7L) multi‐level inverter (MLI) topology for grid‐connected medium and high voltage power applications is presented in this paper. The topology consists of two isolated transformers with different winding ratio and four switches connected to a single‐phase grid. This topology provides a great advantage over conventional MLIs by reducing passive and active components to allowing a 7L output voltage. Moreover, model predictive control (MPC) method is implemented to 7L‐MLI to generate gate signals of switches and ensure capacitor voltage balancing and grid connection. Performance of proposed topology has been confirmed by in‐depth analysis under simulation and laboratory setup with existing studies. Experimental results of a 1.5 kW 220 Vrms prototype are presented to support the simulation results. The prototype shows that the harmonic results match the limits of the IEC 61000‐3‐2 standard and show a better performance for grid connection and capacitor voltage balancing than conventional ones.

A novel control strategy of resonant converter with modular rectifier based on SiC switching device

The resonant converter with modular rectifier (RMR) is a promising topology for DC grid applications. This paper studies the control strategy of RMR based SiC switching device including the output voltage and submodule (SM) capacitor voltage balancing control strategy. Firstly, different working modes of the RMR converter are analyzed, and the Critical Mode with the highest efficiency is introduced. A control method is proposed to guarantee the RMR operating the Critical Mode. The control parameters design is detailed. Secondly, the charging and discharging principles of SM capacitor voltages are introduced, then a balancing method is proposed: the SM capacitor voltages are sorted, then assign gate signals with smaller pulse width to SMs with lower capacitor voltages, and vice versa. The proposed control methods are verified by experimental results on a 300 V/1200 V 8 kW RMR prototype based SiC switching device. According to the experimental results, the RMR operates at the Critical Mode under different load and gain conditions. The SM capacitor voltages are well balanced. The peak efficiency is 98.2%.