Symmetric Cascade Research Articles

A Novel Multilevel Inverter for Renewable Energy Applications with Optimized Controller and Reduced Switches

Multilevel converters have the capability of handling high power as well as deliver output with reduced harmonics. So they can be implemented with renewable energy sources to produce multilayer output with symmetric cascade arrangement with reduced switches. Here the control technique is developed in such a way to reduce the harmonics in the grid integrated PV system. The paper proposes optimized Fractional Order Proportional Integral Derivative (FOPID) controller for a seven level reduced switch multilevel inverter. The War Strategy Optimization Algorithm (WSOA) which utilizes optimizing the strategic movements of armed forces (assault and defend) towards the final optimal value is used to optimize the FOPID controller. This WSOA algorithm is used to adjust the gain parameters of the FOPID controller there by improving the system performance. The characteristics of grid connected PV system are regulated by implementing this suggested technique. The projected approach is incorporated using MATLAB / Simulink and the performances are evaluated and compared with the conventional techniques like GA – PID and WSOA – PID controllers.

Design and analysis of single-phase five-level inverter based on integrated energy system

New energy power generation, mainly photovoltaic power generation and wind power generation, is one of the key research topics today. It is found that the grid-connected phase of power transmission is very important in the transmission process after power generation through these two ways. This paper introduces in detail the various stages of power transmission under the background of integrated energy system, mainly photovoltaic power generation and wind power generation as the research object. This paper presents a new grid-connected symmetrical cascade half-bridge multilevel inverter (SCHB) under the background of comprehensive energy and presents a Pulse Width Modulation (PWM) control scheme which can make the inverter output stable multilevel voltage. By this scheme, the voltage of the shunt capacitor is basically unchanged and the multistage voltage output of SCHB inverter is guaranteed. The advantages of the designed inverter are that the whole inverter can be powered by a single power supply and a single inductance, and the number of voltage levels can be controlled because of the use of a small amount of reactive power components. This paper describes the topological results of the inverter and the PWM control scheme of stable output multistage voltage.

Progressive Adjacent-Layer coordination symmetric cascade network for semantic segmentation of Multimodal remote sensing images

Semantic segmentation of remote sensing images is a fundamental task in computer vision, with significant applications in forest and farmland cover surveys, geological disaster monitoring, and other related fields. The inclusion of digital surface models can enhance the segmentation performance compared to using unimodal imaging alone. However, most existing methods simply combine the features from both modalities without considering their differences and complementarity, leading to a loss of spatial details. In order to address this issue and improve segmentation accuracy, we propose a novel network called Progressive Adjacent-Layer Coordination Symmetric Cascade Network (PACSCNet). This network employs a two-stage fusion symmetric cascade encoder to leverage the similarities and differences between adjacent features for cross-layer fusion, thereby preserving spatial details. Additionally, our network includes a new dual-pyramid symmetric cascade decoder that extracts similarities in multimodal and cross-layer fusion features for merging. Furthermore, a pyramid residual integration module progressively integrates features at four scales to mitigate noise interference during large-scale fusion. Extensive experimental evaluations on the Vaihingen and Potsdam datasets demonstrate that PACSCNet achieves strong semantic segmentation performance, comparable to state-of-the-art approaches, in terms of accuracy and intersection-over-union. The source code and results of our proposed PACSCNet are publicly available at https://github.com/F8AoMn/PACSCNet.

A high-precision interface for tunneling magnetoresistance sensors with 0.15 nT/√Hz resolution

The tunneling magnetoresistance (TMR) with high-resolution digital output is widely used in military and civil fields. In this work we proposed a low-noise read-out circuit and a four-order fully differential sigma-delta modulator for TMR sensors. In the read-out circuit, we used symmetrical cascade for good matching. We used correlated double sampling (CDS) technique to improve the conversion accuracy of the modulator. In switched capacitor circuits we used time-division multiplexing to suppress charge injection and clock feedthrough. The high-precision application specific integrated circuit (ASIC) chip was fabricated by a 0.35 [Formula: see text]m CMOS process from Shanghai Huahong foundry. The TMR sensor was placed in an environment of three-layer magnetic shielding for test. The active area of the ASIC is only about [Formula: see text]. At a sampling frequency of 20 kHz, the TMR magnetometer consumes 77 mW from a single 5 V supply; the sigma-delta modulator for TMR can achieve an average noise floor of −141 dBV. The magnetometer works at a full scale (FS) of [Formula: see text], it can achieve a nonlinearity of 0.2% FS and a resolution of 0.15 nT/Hz[Formula: see text] over a signal bandwidth.

BSCN: bidirectional symmetric cascade network for retinal vessel segmentation

BackgroundRetinal blood vessel segmentation has an important guiding significance for the analysis and diagnosis of cardiovascular diseases such as hypertension and diabetes. But the traditional manual method of retinal blood vessel segmentation is not only time-consuming and laborious but also cannot guarantee the accuracy and efficiency of diagnosis. Therefore, it is especially significant to create a computer-aided method of automatic and accurate retinal vessel segmentation.MethodsIn order to extract the blood vessels’ contours of different diameters to realize fine segmentation of retinal vessels, we propose a Bidirectional Symmetric Cascade Network (BSCN) where each layer is supervised by vessel contour labels of specific diameter scale instead of using one general ground truth to train different network layers. In addition, to increase the multi-scale feature representation of retinal blood vessels, we propose the Dense Dilated Convolution Module (DDCM), which extracts retinal vessel features of different diameters by adjusting the dilation rate in the dilated convolution branches and generates two blood vessel contour prediction results by two directions respectively. All dense dilated convolution module outputs are fused to obtain the final vessel segmentation results.ResultsWe experimented the three datasets of DRIVE, STARE, HRF and CHASE_DB1, and the proposed method reaches accuracy of 0.9846/0.9872/0.9856/0.9889 and AUC of 0.9874/0.9941/0.9882/0.9874 on DRIVE, STARE, HRF and CHASE_DB1.ConclusionsThe experimental results show that compared with the state-of-art methods, the proposed method has strong robustness, it not only avoids the adverse interference of the lesion background but also detects the tiny blood vessels at the intersection accurately.

Five-Level T-type Cascade Converter for Rooftop Grid-Connected Photovoltaic Systems

Multilevel converters are widely considered to be the most suitable configurations for renewable energy sources. Their high-power quality, efficiency and performance make them interesting for PV applications. In low-power applications such as rooftop grid-connected PV systems, power converters with high efficiency and reliability are required. For this reason, multilevel converters based on parallel and cascaded configurations have been proposed and commercialized in the industry. Motivated by the features of multilevel converters based on cascaded configurations, this work presents the modulation and control of a rooftop single-phase grid-connected photovoltaic multilevel system. The configuration has a symmetrical cascade connection of two three-level T-type neutral point clamped power legs, which creates a five-level converter with two independent string connections. The proposed topology merges the benefits of multi-string PV and symmetrical cascade multilevel inverters. The switching operation principle, modulation technique and control scheme under an unbalanced power operation among the cell are addressed. Simulation and experimental validation results in a reduced-scale power single-phase converter prototype under variable conditions at different set points for both PV strings are presented. Finally, a comparative numerical analysis between other T-type configurations to highlight the advantages of the studied configuration is included.

Design of a Low Profile Flexible Tri-Band Frequency Surface Applied in X-Band, K-Band and Millimeter-Band

A low profile flexible miniaturized tri-band frequency surface is proposed by cascading three layers of periodic arrays. The top and bottom layers have the same square patch structure embedded in the bending gap, whereas the middle layer has an interlaced metal grid structure. The medium between each layer is made of flexible polyimide material with a thickness of only about 0.2mm. The coupling of the three metal layers gives rise to a first X-band passband, with a central frequency of 10.6 GHz. The interlaced metal grid structure generates a second K-band passband, with a central frequency of 24.1GHz. The two-layer symmetrical planar cascade structure produces double-peak resonances at 39.4 GHz and 46.2 GHz, forming a third millimeter-wave passband. Compared with the traditional tri-band FSSs, due to the combination of bending technology and multi-screen cascade technology, the reported structure generates the first and second passbands with miniaturization and good angle stability, and the third passband with rectangular filtering characteristics. Besides fabrication and tests, the corresponding equivalent circuit model is also established in order to analyze the transmission characteristics. The test results are well compatible with the simulation results.

A New Single-phase Symmetrical Cascade Multilevel Inverter with Low Number of Power Switches

In this paper a new 5-level single phase symmetrical cascade multi-level inverter is proposed. The proposed topology contains combination of unidirectional and bidirectional power switches based on output voltage level number. The number of power switches and withstanding voltage of powers witches were reduced related to the other topologies. This configuration can be extended to the n-level inverter. In symmetrical case of proposed inverter the 5th harmonic output voltage will be eliminated. The performance analysis of the proposed inverter using suitable switching algorithm for producing the 5-level output voltage was confirmed by simulation and experimental results.

Возможности применения мощных симметричных многоуровневых каскадных инверторов в электроприводе вентиляторами главного проветривания

Возможности применения мощных симметричных многоуровневых каскадных инверторов в электроприводе вентиляторами главного проветривания

A Novel Symmetrical Cascade H-Bridge Multi-Level Inverter Topology with Reduced Switching Devices

A Novel Symmetrical Cascade H-Bridge Multi-Level Inverter Topology with Reduced Switching Devices

Multistream Cascades for Separation of Multicomponent Isotopic Mixtures

A method of calculating and optimizing a counterflow symmetric cascade with an arbitrary number of feed streams and additional product streams was developed. A computational experiment on the separation of a tungsten hexafluoride mixture was performed. It was shown that additional product streams are expedient for obtaining a high concentration of intermediate-mass components. The most effective cascade is a combined R cascade, whose depletion and enrichment parts are reckoned according to different pairs of key components.

The Low Reduced Frequency Limit of Vibrating Airfoils—Part I: Theoretical Analysis

This paper studies the unsteady aerodynamics of vibrating airfoils in the low reduced frequency regime with special emphasis on its impact on the scaling of the work-per-cycle curves, using an asymptotic approach. A perturbation analysis of the linearized Navier–Stokes equations for real modes at low reduced frequency is presented and some conclusions are drawn. The first important result is that the loading of the airfoil plays an essential role in the trends of the phase and modulus of the unsteady pressure caused by the vibration of the airfoil. For lightly loaded airfoils, the unsteady pressure and the influence coefficients (ICs) scale linearly with the reduced frequency whereas the phase departs from π/2 and changes linearly with the reduced frequency. As a consequence, the work-per-cycle scales linearly with the reduced frequency for any interblade phase angle (IBPA), and it is independent of its sign. For highly loaded airfoils, the unsteady pressure modulus is fairly constant exhibiting only a small correction with the reduced frequency, while the phase departs from zero and varies linearly with it. In this case, only the mean value of the work-per-cycle scales linearly with the reduced frequency. This behavior is independent of the geometry of the airfoil and the mode shape in first-order approximation in the reduced frequency. For symmetric cascades, the work-per-cycle scales linearly with the reduced frequency irrespective of whether the airfoil is loaded or not. These conclusions have been numerically confirmed in Part II of the paper.

Extremely high chromatic-stability white organic light-emitting device with symmetrical cascade emissive layer

We have employed four adequate complementary phosphor emitters (blue, green, yellow, and red) and two host and transport materials (CBP: 4,4′-bis(carbazol-9-yl)biphenyl; TPBi: 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) to configure a symmetrical cascade emissive layer white organic light-emitting device (WOLED), in which four emitters are in turn incorporated in CBP and TPBi from high to low energy level from CBP/TPBi interface. The symmetrical cascade emissive layer WOLED shows extremely high chromatic-stability with a slight CIE coordinates shift at wide range of driving voltage. As the voltage increases from 5V to 9V, the symmetrical cascade emissive layer WOLED maintains CIE coordinates of (0.384, 0.467)–(0.387, 0.469) and high color rendering index (CRI) of 85–86 with ideal correlated color temperature (CCT) of 4407–4292K. Furthermore, this WOLED also exhibits a peak current efficiency of 43.6cd/A and a maximum power efficiency of 31.1lm/W, which are much higher (by 1.43 and 1.50 times) than those of the reference device with four emitters only being doped in single CBP host. The improvement of color stability is due to the fact that symmetrical cascade emissive layer suppresses the shift of carrier recombination zone as the voltage increases; the improvement of efficiency is attributed to the effective utilization of excitons.

Novel multilevel inverter topologies for medium and high‐voltage applications with lower values of blocked voltage by switches

In this study, novel multilevel inverter structures for medium and high-voltage applications are proposed. The proposed topologies can generate a great number of output voltage levels with more advantages. Firstly, a new symmetric cascade topology is presented which can be used in medium voltage applications. Then, based on the proposed symmetric structure, a new hybrid structure is recommended. The proposed hybrid structure can be used in high-voltage applications. The comparison between the proposed symmetric topology with conventional symmetric cascade topology and other non-conventional symmetric topologies are presented in terms of the number of insulated gate bipolar transistors (IGBTs), anti- parallel diodes, gate drivers and blocked voltage by switches. Moreover, the proposed topologies can be used in bidirectional power flow applications. The validity of the proposed multilevel inverter structures are verified with experimental and simulation results.

Voltage Balancing and Commutation Suppression in Symmetrical Cascade Multilevel Converters for Power Quality Applications

This paper presents a modulation strategy for symmetrical cascaded multilevel converters that simultaneously balances the individual DC voltages and reduces switching losses by eliminating redundant or unnecessary commutations. The voltage regulation is based on a 1-bit digital signal indicating whether the DC link voltage of each H-bridge is above or below the set point. The system command identifies commutations that can be suppressed without causing output voltage distortion, thus reducing converter losses. The voltage balancing is reached by postponing each switching commutation for a short lapse of time. Simulation and experimental results for an active filter application validate the proposed methods.

New multilevel inverter with reduction of switches and gate driver

This paper presents a novel topology for symmetrical cascade multilevel converter. The proposed circuit consists of series connected sub multilevel converters units and it can generate DC voltage levels similar to other topologies. The proposed topology results in reduction of switches number, losses, installation area and converter cost. This converter has been used in a Dynamic Voltage Restorer (DVR). Simulation results carried out by MATLAB/SIMULINK show the voltage injection capability of converter and the efficiency of its controller in compensating voltage sag and swell.

Symmetry-induced perfect transmission and inverse magnetoresistance in cascade junctions of ferromagnet and semiconductor

Within the Landauer framework of ballistic transport, we theoretically investigate spin-dependent resonant transmission and magnetoresistance in symmetric cascade junctions of ferromagnetic metal (FM) and semiconductor (SC). It is shown that spin-up and spin-down electrons possess different bandgap structures against the Rashba spin-orbit wave vector. Due to the mirror symmetry, multiple spin-dependent perfect transmissions of electrons can be obtained within the bandgap, thereafter, spin polarization has multiple reversals. Around each resonant wave vector, high spin polarization is achieved and the electrical conductance comes from one kind of spin electrons. The resonant transmissions originate from the spin-dependent quasi-bound states at energies above the potential barriers, which are demonstrated by the electronic charge distributions in the system. Furthermore, if we change the magnetization of FM in the centre of the junctions, inverse magnetoresistance can be observed. The investigations may have potential applications in spin filters and spin switches.

Comment on P. K. Clark's Distribution of Lognormal-Normal Increments and the Lognormal Cascade Distribution

To illustrate that the mathematical form of P. K. Clark's distribution of lognormal-normal increments, with a minor bug fix, is the same as the symmetric lognormal cascade distribution that I studied in 2008-9, although the two were derived from very different stochastic assumptions.

Variation in entropy in the course of combination of fractions in units of a separating cascade and losses of accomplished work

The summary variation in entropy in the course of combining the fractions in units of a symmetrical cascade is calculated. The thermodynamic interpretation of the difference between the work of separation, determined using the separating potential, and the thermodynamically evaluated work of isobaric-isothermal process of mixing is given.

Precision determination of invisible-particle masses at the CERN LHC. II.

We further develop the constrained mass variable techniques to determine the mass scale of invisible particles pair-produced at hadron colliders. We introduce the constrained mass variable ${M}_{3C}$ which provides an event-by-event lower bound and upper bound to the mass scale given the two mass differences between the lightest three new particle states. This variable is most appropriate for short symmetric cascade decays involving two-body decays and on-shell intermediate states which end in standard-model particles and two dark-matter particles. An important feature of the constrained mass variables is that they do not rely simply on the position of the end point but use the additional information contained in events which lie far from the end point. To demonstrate our method we study the supersymmetric model SPS 1a. We select cuts to study events with two ${\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{2}^{o}$ each of which decays to ${\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{o}$, and two opposite-sign same-flavor charged leptons through an intermediate on-shell slepton. We find that with $300\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity the invisible-particle mass can be measured to ${M}_{{\stackrel{\texttildelow{}}{\ensuremath{\chi}}}_{1}^{o}}=96.4\ifmmode\pm\else\textpm\fi{}2.4\text{ }\text{ }\mathrm{GeV}$. Combining fits to the shape of the ${M}_{3C}$ constrained mass variable distribution with the $\mathrm{max}{m}_{ll}$ edge fixes the mass differences to $\ifmmode\pm\else\textpm\fi{}0.2\text{ }\text{ }\mathrm{GeV}$.