Hybrid Multilevel Research Articles

Logical-probabilistic and simulation modeling as a toolkit for complex analysis and risk management of a cargo port

The paper presents a structural model of the risk of failure to achieve the strategic goal of a cargo port, supplemented by several levels of consideration. The model of scenarios of all existing significant risks is developed. The hybrid logical-probabilistic model, the cascade logicalprobabilistic model and the multi-level cascade hybrid LP-model of the risk of failure to achieve the main strategic goal of the port are proposed. The main idea is to link together the technology of formalizing risks using the constructed logical and probabilistic models and simulation modeling, the interpretation of the results of which is possible using LP-models and scenarios. The proposed models allow to carry out a comprehensive analysis of the risk of failure to achieve the strategic goal of a cargo port based on the scenario formalization of risks of various management levels, as well as to simplify the process of interpreting the results of simulation modeling taking into account external factors of influence. Complex using of all this models allows to develop timely informed management decisions.

An Original Hybrid Multilevel DC-AC Converter Using Single-Double Source Unit for Medium Voltage Applications: Hardware Implementation and Investigation

In this article, an original hybrid multilevel DC-AC converter configurations are proposed by using single-double source unit for medium voltage applications. The proposed topologies are derived by hybridization of single and double source units with polarity changer and cascaded with full-bridge converter for medium and high voltage applications. Two different hybrid topologies presented and each topology configured for both symmetric and asymmetric method. The proposed hybrid topologies compared with the conventional cascaded H-bridge converter (CHB), and the best topologies recommended for medium voltage applications. The comparison in terms of the number of switches, gate driver circuits, maximum blocking voltage by switches and total peak inverse voltages of switches presented. The proposed topologies require a small installation area and low cost. The validity of the proposed hybrid converter structures is verified by simulation using MATLAB/Simulink and hardware results. The simulation and hardware results show a good agreement with the theoretical approach.

A Multi-Cell 21-Level Hybrid Multilevel Inverter Synthesizes a Reduced Number of Components With Voltage Boosting Property

A multi-cell hybrid 21-Level multilevel inverter is proposed in this paper. The proposed topology includes two-unit; an H-bridge is cascaded with a modified K-type unit to generate an output voltage waveform with 21 levels based only on two unequal DC suppliers. The proposed topology’s advantage lies in the fine and clear output voltage waveforms with high output efficiency. Meanwhile, the high number of output voltage waveform levels generates a low level of distortion and reduces the level of an electromagnetic interface (EMI). Moreover, it reduces the voltage stress on the switching devices and gives it a long lifetime. Also, the reduction in the number of components has a noticeable role in saving size and cost. Regarding the capacitors charging, the proposed topology presents an online method for charging and balancing the capacitor’s voltage without any auxiliary circuits. The proposed topology can upgrade to a high number of output steps through the cascading connection. Undoubtedly this cascading will increase the power level to medium and high levels and reduce the harmonics content to a neglectable rate. The proposed system has been tested through the simulation results, and an experimental prototype based on the controller dSPACE (DS-1103) hardware unit used to support the simulation results.

A V2G Integrated Battery Charger Based on an Open End Winding Multilevel Configuration

A new approach to obtain an integrated battery charger is described in this paper, based on the Asymmetrical Hybrid Multilevel Converter topology. Such a particular open-end winding motor configuration, which has proved to be more efficient than conventional inverter topologies in EV motor drive applications, can be turned in an on-board battery charger only by acting on the control system. Thus, no circuit reconfiguration through electro-mechanical switches is required. Moreover, by introducing a single extra power switch, a bilateral power flow can be managed enabling vehicle to grid operations. The obtained integrated battery charger can be supplied either by a standard ac single-phase grid, either by a dc power source for direct connection to domestic energy resources. The proposed approach enables a new remarkable function to the asymmetrical hybrid multilevel converter at a marginal extra cost, thus mitigating the larger complexity and cost of such an inverter if compared with conventional topologies.

A novel evolutionary algorithm (MFO) with rate monotonic scheduling for load balancing in LTE advanced networks

In recent days, long term evolution (LTE)-advanced is the newest 4G technology. In this cellular network, the femto cells offered a viable and cost-effective method of enhancing the cellular reporting and capability for each WLAN and WiMAX. However, network allocates resource dissimilar to each and every users. To overcome this difficulty, moth flame optimisation (MFO) technique is used to provide equal resource allocation to user. Using this MFO method to balance the load for routing process. Rate-monotonic scheduling (RMS) algorithm is applied to share the load equally to available user, which increases the throughput and control the overload during communication time instance. The simulation results show that the proposed MFO technique has achieved improved network performance than existing hybrid multilevel feedback queue with round robin (HMFQ-RR) and hybrid weighted round robin with shortest job first (HWRR-SJF) in terms to reduce packet loss rate, packet delay and end to end delay.

Binary Hybrid Multilevel Inverter-Based Grid Integrated Solar Energy Conversion System With Damped SOGI Control

This paper presents a binary hybrid multilevel inverter (BHMLI) based grid-connected solar energy conversion system (SECS), controlled by damped second-order generalized integral (DSOGI). The BHMLI architect has a cascaded half-bridge array, which modifies the DC-link of the H-bridge of the voltage source inverter, and results in approximate reference waveform. It reduces the dV/dt of the H-bridge switches and improves output waveform quality. The DSOGI control damps the oscillations and overshoots and provides longer service period of low power switches at transient conditions. It is implemented in the multilevel inverter application for the first time in literature. The SECS is designed to inject active power to the grid, and also mitigates the harmonic and reactive power demands of the load. The cascading of n' half-bridges and one H-bridge generate (2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(nC1)</sup> - 1) output voltage levels. The maximum power extraction from solar photovoltaic (PV) array is achieved through incremental conductance (IC) algorithm based maximum point tracking (MPPT) operation of the DC-DC converter. An isolated single-input multiple-output single-ended primary inductance converter (SIMO-SEPIC) realizes it. SECS with 15-level BHMLI is analyzed with extensive simulation as well as with a hardware prototype. Moreover, the shunt active filter functionality of the system at various load conditions are verified and maintained the grid power quality within the IEEE-519 standard throughout the operation. The laboratory developed setup is tested for 5 kW, 400 V, three-phase system, and the experimental analysis at steady-state and dynamic variations of load-side and insolation variations validate the theoretical claims.

A novel evolutionary algorithm (MFO) with rate monotonic scheduling for load balancing in LTE advanced networks

In recent days, long term evolution (LTE)-advanced is the newest 4G technology. In this cellular network, the femto cells offered a viable and cost-effective method of enhancing the cellular reporting and capability for each WLAN and WiMAX. However, network allocates resource dissimilar to each and every users. To overcome this difficulty, moth flame optimisation (MFO) technique is used to provide equal resource allocation to user. Using this MFO method to balance the load for routing process. Rate-monotonic scheduling (RMS) algorithm is applied to share the load equally to available user, which increases the throughput and control the overload during communication time instance. The simulation results show that the proposed MFO technique has achieved improved network performance than existing hybrid multilevel feedback queue with round robin (HMFQ-RR) and hybrid weighted round robin with shortest job first (HWRR-SJF) in terms to reduce packet loss rate, packet delay and end to end delay.

A New Hybrid Multilevel Inverter with Extended Number of Voltage Steps

This paper presents and studies an improved multilevel inverter topology to produce higher voltage levels with reduced switching devices at the inverter output. The suggested topology is based on SCSS multilevel inverter. In this topology, DC sources are divided into two groups, inner group and outer group. The function of the outer dc source group is to create the square waveforms that are close in nature to the required output waveforms. However, the inner group is used to increase the number of the DC voltage levels to produce an output voltage close to the desired wave. This task is accomplished by arithmetic operation (addition or subtraction) of the value of the inner DC source with the blocks created by the outer group, respectively. A hybrid modulation scheme has been utilized to substantially reduce harmonics distortion. The performance of the proposed topology is then compared with other conventional and concurrent structures of multilevel inverter as well as evaluated by simulation results.

A hybrid approach for intrusion detection based on machine learning

With the evolution of internet, network security has emerged as one of the key areas of research. Network security is to safeguard the privacy, availability and integrity of the system. Identification of intrusion is core component to attain overall network security success. Therefore, intrusion detection (ID) is broadly explored by researchers and idea of identification of intrusion has developed into a system, known as intrusion detection system (IDS). IDS focuses on investigation of attacks and offers desirable support for defence management along with information about the intrusion. Several intrusion detection approaches are already proposed to mitigate the impact of intrusion. In this paper, these techniques are discussed to highlight the state-of-the-art and a multilevel hybrid approach based on SVM-Naïve is proposed to predict malicious traffic from the network. Here, KNN along with k-fold cross validation is used to create new high-quality training dataset that outstandingly improved performance of classifiers. Performance of proposed model is evaluated by using standard KDD 1999 Cup dataset. Comparison of proposed model is carried out with existing techniques and it is analysed that its performance is better regarding exactness (99.73%), recognition rate of attack classes (99.81%) and FPR (0.21%).

Assessment of multilevel ensemble-based data assimilation for reservoir history matching

Multilevel ensemble-based data assimilation (DA) as an alternative to standard (single-level) ensemble-based DA for reservoir history matching problems is considered. Restricted computational resources currently limit the ensemble size to about 100 for field-scale cases, resulting in large sampling errors if no measures are taken to prevent it. With multilevel methods, the computational resources are spread over models with different accuracy and computational cost, enabling a substantially increased total ensemble size. Hence, reduced numerical accuracy is partially traded for increased statistical accuracy. A novel multilevel DA method, the multilevel hybrid ensemble Kalman filter (MLHEnKF) is proposed. Both the expected and the true efficiency of a previously published multilevel method, the multilevel ensemble Kalman filter (MLEnKF), and the MLHEnKF are assessed for a toy model and two reservoir models. A multilevel sequence of approximations is introduced for all models. This is achieved via spatial grid coarsening and simple upscaling for the reservoir models, and via a designed synthetic sequence for the toy model. For all models, the finest discretization level is assumed to correspond to the exact model. The results obtained show that, despite its good theoretical properties, MLEnKF does not perform well for the reservoir history matching problems considered. We also show that this is probably caused by the assumptions underlying its theoretical properties not being fulfilled for the multilevel reservoir models considered. The performance of MLHEnKF, which is designed to handle restricted computational resources well, is quite good. Furthermore, the toy model is utilized to set up a case where the assumptions underlying the theoretical properties of MLEnKF are fulfilled. On that case, MLEnKF performs very well and clearly better than MLHEnKF.

A Multilevel Distributed Hybrid Control Scheme for Islanded DC Microgrids

This paper proposes a multilevel hybrid control scheme, including grid control and node control, for an islanded 48-V solar photovoltaic-based low voltage dc microgrid that aims to overcome the drawbacks of centralized and decentralized control schemes. The analyzed microgrid includes a 35-kW rooftop solar system as the main power source at bus-1 with battery storage, 5-kW hybrid energy storage system (Vanadium Redox flow battery with super capacitor) at bus-2, and variable loads such as electrical vehicles at bus-3. In the case of a central failure, the proposed hybrid control scheme is capable of seamlessly switching between high bandwidth communication and low bandwidth communication channels of communications to implement a distributed control scheme. The central supervisory controller is responsible for updation of grid characteristics and sending/receiving information to/from local node controllers, which are responsible for bus voltage regulation and energy management. The control hierarchy features optimized and safe operation (charge and discharge) of storage devices in dc microgrids. The paper also demonstrates the application of battery-supercapacitor systems to absorb system transients during load changes. The simulation showcases the continuous flow of information and decision processes via each level of control while simultaneously taking into consideration the constraints of each subsystem. The scheme has been simulated in MATLAB/Simulink environment for various case studies to evaluate system robustness. Further, the proposed scheme has been tested experimentally with its prototype and its results are explored.

Ab Initio Calculations for Molecule-Surface Interactions with Chemical Accuracy.

Atomistic understanding of complex surface phenomena such as heterogeneous catalysis or storage and separation of energy-relevant gases in nanoporous materials (zeolites; metal-organic frameworks, MOFs) requires knowledge about reaction energies and energy barriers for elementary steps. This is difficult to obtain from experiment since the number of possible chemical, adsorption/desorption, and diffusion steps coupled to complex reaction networks is large, and so is the number of possible surface sites. Here is an important role of quantum chemistry which can provide rate and equilibrium constants for elementary steps "ab initio." To be useful, the predictions have to reach chemical accuracy (4 kJ/mol) which is difficult to achieve because realistic models of the surface systems may comprise of the order of a thousand atoms. While density functional theory (DFT) as a rule cannot be trusted to yield results within chemical accuracy limits, methods that are accurate enough (Coupled Cluster with Single, Double, and perturbative Triple Substitution, CCSD(T)) cannot be applied because of their exponential scaling with system size. This Account presents a hybrid high-level-low-level quantum method that combines DFT with dispersion for the full periodic system with second order Møller-Plesset perturbation theory (MP2) for the reaction site within a mechanical embedding scheme. In addition, to check if MP2 is accurate enough, we calculate Coupled Cluster (CC) corrections with Single, Double, and perturbatively treated Triple substitutions (CCSD(T)) for sufficiently small models of the reaction site. This multilevel hybrid MP2:DFT-D+ΔCC method is shown to yield chemical accuracy for a set of 12 molecule-surface interaction systems for which reliable experimental data are available. For CO/MgO(001), the history of the experiment-theory comparison illustrates two problems: (i) Do experiment and theory look at the same surface site? (ii) Does theory calculate the same quantity as derived from experiment? The hybrid MP2:DFT-D+ΔCC data set generated includes the MgO(001) surface, the Mg2(dobdc) metal-organic framework, and the proton forms of the CHA and MFI zeolites interacting with the H2, N2, CO, CO2, CH4, and C2H6 molecules. It serves two purposes. First, it will be useful for testing density functionals with respect to their performance for molecule-surface interactions. Second, it establishes the hybrid MP2:DFT-D+ΔCC method as a reliable and powerful tool for ab initio predictions of adsorption and reaction energies as well as energy barriers when testing reaction mechanisms. For adsorption of small molecules in MOFs, isotherm predictions have reached a level of accuracy that deviations between theoretical predictions and experiments indicate sample imperfections. For elementary steps of the industrially important methanol-to-olefin process, our hybrid MP2:PBE+D+ΔCC calculations yield rate constants in agreement with experiment within chemical accuracy limits, finally achieving for molecule-surface reactions which was possible so hitherto only for gas phase reactions involving not more than 10 atoms.

FOSTERING COMPASSIONATE CARE FOR PERSONS WITH ALZHEIMER’S DISEASE AND RELATED DEMENTIAS

The aim of this study was to examine the impact of the implementation of a new Compassionate Care (CC) curriculum, designed by social workers, on the quality of care provided by Certified Nursing Assistants (CNAs) to residents with Alzheimer’s disease (AD). Additionally, the purpose was to create a collaborative network of CNAs that supported each other. The sample included residents and CNAs from an experimental nursing facility and a control nursing facility. At baseline and 12-weeks, data were collected on AD knowledge, self-efficacy, caregiving satisfaction, and affiliate stigma. CNA changes in terms of their knowledge of AD, self-efficacy, caregiving satisfaction and affiliate stigma were analyzed using a two-way mixed method MANOVA. The stress levels of the residents, specifically agitation and salivary cortisol levels, was examined by testing a hybrid multilevel growth model. The final models were able to show how the changes in the CNAs specifically affected these positive outcomes. CNA knowledge and self-efficacy had the most impact on changing agitation levels, and CNA knowledge and agitation levels had the most impact on salivary cortisol levels. The results of this study showed that integrating a compassionate care curriculum into the work that CNAs perform can lead to positive outcomes on knowledge, self-efficacy, caregiving satisfaction, affiliate stigma and a reduction of agitation and cortisol levels in persons with AD.

High-level number multilevel single-phase current-source inverter with reduced switching device count

This paper proposes an advanced technique in generating a pure sinusoidal output current waveform for the high number multilevel lsingle-phase current-source inverter (CSI) with reduced switching device count. Previous multilevel CSI development proposed a new technique in generating pure sinusoidal output by compensating the staircase current with a linear current. This linear current compensation intends to reduce the output filter capacitor size without sacrificing inverter efficiency. However, this hybrid multilevel CSI would give higher efficiency and performance if applie in high number of levels. Consequently, the system needs high switching device count. Too many switching devices utilization will decrease the performance and the power density of the CSI as well. Therefore, this technique is introduced and only possible to be realized if the number of levels is higher than 5-level. By applying multilayer stagemethod while managing the DC current module activation sequences, the high number of levels CSI can be constructed with only using few DC current modules. As a result, according to the computer comparison simulation, the implementation of the proposed technique delivers relatively equal results compared to the conventional one just by utilizing fewers witching devices.

Asymmetrical Multilevel Hybrid Inverter - Analysis and Experimentation

This paper describes a voltage-fed asymmetrical hybrid inverter based on a symmetrical hybrid multilevel DC-AC converter for high voltage/high power applications. The proposed inverter is controlled by two types of modulationpatterns: low frequency (single pulse) and high frequency (sinusoidal PWM), responsible for obtaining a reduced harmonic distortion in the output voltage. Furthermore, the converter is asymmetrically powered, being fed by two sources with distinct values, obtaining seven levels phase voltage output. The results are presented with two pulse width modulation strategies, aimed at reducing the harmonic distortion in the voltage output. The operation of single-phase and three-phase circuits was verified by means of simulations and results obtained with an experimental prototype operating at a frequency switching of 1.5 kHz with a fundamental frequency of 50 Hz.

PWM Technique for Single Phase Asymmetrical Hybrid Multilevel Inverter for Non-linear and Dynamic loads

A two level VSI has output voltage either equal to positive or negative source voltage. This inverter has more ripple. In order to reduce the ripple content more number of switches are needed to produce many number of stepped voltage waveform. This improves the quality of power. This switching losses depends on the frequency of operation so when a two level inverter is operated at high frequency, the switching losses are predominant. This limits the use of such inverters. Hence, being replaced by Multilevel inverters. They have attracted academician and industry personal for medium and high-power power control. Such attractive features are available in hybrid multilevel inverter. Hence, these are preferred. They provide multi-level operation by using hybrid sources. Moreover, the number of power electronics components needed are less than conventional CMI for same voltage level. Thus, such inverters have more efficiency. In the proposed techniques, an asymmetrical hybrid multilevel inverter has been simulated using MATLAB Simulink. The results obtained have been presented for three different types of load.

A hybrid adaptive finite element phase‐field method for quasi‐static and dynamic brittle fracture

SummaryThe phase‐field approach has unique advantages in describing fracture phenomena, which has received extensive attention in the past decade. Nevertheless, the phase‐field modeling of fracture is computationally demanding, due to the high temporal‐spatial resolution required for crack tracking. In this contribution, a novel hybrid adaptive finite element phase‐field method (ha‐PFM) is developed to solve brittle fracture problems under quasi‐static and dynamic loading. ha‐PFM can dynamically track the propagation of the cracks and adaptively refine the meshes based on a novel crack tip identification strategy. Afterward, the refined meshes in the noncrack progression region are reconverted into coarse meshes. This scheme prominently reduces the computational cost, eg, CPU time and memory usage. Unlike the previous adaptive phase‐field method, multilevel hybrid triangular and quadrilateral elements were developed to discretize the computational domain, which eliminates hanging nodes and ensures that the meshes in the vicinity of the crack tip are highly isotropic. Several representative benchmarks containing quasi‐static and dynamic fracture were reinvestigated with ha‐PFM, and its excellent performance is substantiated by comparison with the standard phase‐field method and literature results.

Novel Symmetric Modular Hybrid Multilevel Inverter With Reduced Number of Semiconductors and Low-Voltage Stress Across Switches

In this paper, by using a modular hybrid structure, a new topology for symmetric multilevel inverters (MLIs) with a small number of semiconductors and low voltage stress across switches is proposed. Despite many other topologies, this topology can inherently produce negative and zero levels without using the H-bridge. The voltage stress across a particular switch of the proposed MLI is inversely proportional to the switching frequency of that switch in a voltage period. The proposed structure is based on two types of modules, that is, the f-module and the e-module. The e-module uses a capacitive voltage divider to double the number of nonzero levels. The voltages of the capacitors are approximately balanced without complex control methods. The basic structure of the proposed topology is formed by connecting the f-module and the e-module in series with each other, and the cascaded topology is developed by cascading multiple f-modules with an e-module. To investigate the proposed topology and prove its practicability, simulation results obtained using MATLAB/Simulink, analysis of the capacitor voltages, and experimental results are presented. A comparative study is also performed to show the merit of the new MLI over other topologies.

A Novel Hybrid Multilevel PWM Technique for Power Rating Enhancement in Improved Hybrid Cascaded Diode Clamped Multilevel Inverter

In this article, an improved hybrid topology called cascaded diode clamped half bridge multi-level inverter is proposed upon a conventional cascaded H-bridge (CHB) multi-level inverter (MLI) which has the limitation to withhold a specific cell voltage due to the constraint on the device voltage stress. The proposed topology will ensure the enhancement of cell voltage capability double times, reduces the device stress, modularity in structure, and allows even power distribution. As a result, the user can now integrate two numbers of active dc sources to a cell. This ensures the efficiency of power enhancement in the applications like on/off grid-connected renewable energy system which require the power to be converted from dc to ac or vice versa. The proposed topology is compared extensively with the conventional CHB MLI at different loads. Hybrid pulse width modulation technique allows to operate the individual half bridge. The simulation and experimental results confirm the performance and efficiency of this proposed topology. A mathematical model of the proposed topology has been derived for the better feasibility of this topology extension to various other applications.

A Novel Switched Capacitor Boost Derived Multilevel Hybrid Converter Modeling and Analysis

A Novel Switched Capacitor Boost Derived Multilevel Hybrid Converter Modeling and Analysis