Series Connection Research Articles

Rapid assessment of substation earthquake risk based on minimal cut sets

Electrical substation systems have been severely damaged in previous earthquakes. It is important to realize the rapid seismic risk assessment of substation systems before an earthquake occurs. This paper proposes a rapid seismic risk assessment framework based on seismic hazards and a functional network model. According to the structural connectivity of the substation, the series and parallel connections of equipment were clarified. Considering the power load capacity of equipment and the power transmission requirements of systems, a dual-functional network model combining structure and electricity was built. On the premise of ensuring earthquake risk probability information, the hierarchical simulation of the fault tree model was carried out. Also, the minimum cut set algorithm was used to rapidly evaluate the seismic risk of the substation system. Aiming at reducing the risk of substation function failure, two risk reduction strategies of seismic retrofitting and additional redundant equipment were put forward. After the seismic analysis of a typical 220 kV substation, key equipment of the substation and the optimal risk reduction strategies were obtained.

Improved Topology and Control Strategies for DC Converters in Wind Power Full DC Systems

This study presents an enhanced composite modular DC/DC converter topology designed to address critical technical requirements in wind power full DC systems, including high capacity, high conversion ratio, and fault isolation. The proposed topology combines MMC circuits and module combination circuits, allowing for exceptional modularity and configurability. Through the serial and parallel connection of multiple modules, the voltage or current levels can be further enhanced. Regarding the control strategy, the paper adopts SOGI phase-locked and coordinate transformation technology to precisely measure and control the differential and common-mode voltages within the MMC modules. A mathematical model is established, providing a theoretical foundation for experimental analysis. The research emphasizes the implementation of key strategies such as circulating current suppression, nearest level approximation, and capacitor voltage sorting. To validate the practicality and effectiveness of the proposed converter topology and control strategy, an experiment is conducted using a ±30 kV/±300 kV, 300 MW model constructed within the MATLAB/Simulink simulation environment.

Magnetic Field Density Analysis in Switchgears

For many years the evaluation of the electromagnetic field (EMF) generated by transformer substations (TS) and switchgear assemblies has been an extremely cumbersome and expensive process. Manufacturers and users of TS and switchgear lacked a broadly-accepted assessment procedure specified in an international reference standard. The publication of the new Technical Report IEC/TR 62271-208 solves this situation since it describes a technique for the evaluation of the EMF generated by switchgear assemblies and TS and opens the possibility of employing simulation tools for this purpose. In this paper, preliminary stage of process for validation of simulation tests in order to substitute laboratory tests according to IEC/TR 62271-208, is described. With this purpose, magnetic field emission analysis is carried out using finite elements (FE) method, for a set of 5 identical switchgears (manufactured by Ormazabal), in series connection. Results obtained through simulation are compared to those measured in laboratory tests. Evaluation results are also compared with applicable limits (100 µT and 500 µT at 50 Hz, according to most human exposure regulations: ICNIRP Guidelines, EU Council Recommendation, Spanish Royal Decree 1066/2001, etc).

MULTI-OBJECTIVE OPTIMIZATION AND PERFORMANCE ANALYSIS OF BIMORPH MAGNETO-ELECTRO-ELASTIC ENERGY HARVESTERS

This study thoroughly investigates the multi-objective optimization of a magneto-electro-elastic (MEE) harvester in bimorph configurations and by the new method of Harris Hawk’s optimization (HHO). The harvesters are configured in both series and parallel connections and under harmonic excitation to explore the effects of various parameters on the performance of the harvesting system. The primary objective is to maximize the total harvested power. Optimization involves various parameters, including dimensions, relative displacement changes, voltage, and current values. The Pareto fronts from the HHO method reveal optimal points in different configurations and scenarios. Notably, the optimal points are selected based on the criterion of maximum total power. The results reveal distinct optimal points for each objective function, demonstrating trade-offs between performance metrics. These findings provide valuable insights into the design and operation of efficient energy harvesters in MEE systems. The parallel configuration outperforms the series connection in terms of the current generation. Moreover, the evaluation of the overall performance of the energy harvesters in terms of total harvested power indicated that both series and parallel connections could lead to promising outcomes. However, the series connection exhibited a more dominant effect on maximizing the total harvested power, proving its relevance in pursuing the highest possible power output.

CellSegUNet: an improved deep segmentation model for the cell segmentation based on UNet++ and residual UNet models

Cell nucleus segmentation is an important method that is widely used in the diagnosis and treatment of many diseases, as well as counting and identifying the cell nucleus. The main challenges when using this method are heterogeneous image intensities in the image, overlapping of cell nuclei, and noise. In order to overcome these difficulties, a hybrid segmentation model with attention block, CellSegUNet, is proposed, inspired by the advantageous points of UNet++ and Residual UNet models. With the proposed attention mechanism, semantic gaps that may occur are prevented by evaluating both horizontal and vertical features together. The serial and parallel connection of the convolutional blocks in the residual modules in the CellSegUNet model prevents data loss. Thus, features with stronger representation ability were obtained. The output layer, which is, especially proposed for the CellSegUNet model, calculated the differences between the data in each layer and the data in the input layer. The output value obtained from the layer level where the lowest value comes from constitutes the output of the whole system. At the same depth level, CellSegUNet versus UNet++ and ResUNet models were compared on Data Science Bowl (DSB), Sartorius Cell Instance Segmentation (SCIS), and Blood Cell Segmentation (BCS) datasets. With the CellSegUNet model, accuracy, dice, and jaccard metrics were obtained as 0.980, 0.970, 0.959 for the DSB dataset, 0.931, 0.957, 0.829 for the SCIS dataset and 0.976, 0.971, 0.927 for the BCS dataset, respectively. As a result, it is predicted that the proposed model can provide solutions to different segmentation problems.

Comparisons and optimization of two absorption chiller types by considering heat transfer area, exergy and economy as single-objective functions

Abstract Absorption cooling technology is an environmentally friendly method to generate continuous chilled water making use of multiple thermal sources, such as waste heat and renewable thermal energy. In this study, two absorption chillers (nominal capacity of 400 kW) with series and parallel connections are evaluated. To research the ideal configuration of chillers after thermodynamic analysis, the structures of the chillers are optimized using the particle swarm optimization algorithm by considering the heat transfer area (HTA), exergy efficiency and total annual cost as single-objective functions. The impact of temperature differences between external and internal flows, heat exchanger efficiencies and the solution allocation ratio is estimated. The optimized HTA, coefficient of performance, exergy efficiency and total annual cost are 149.0 m2, 1.56, 29.44% and $229 119 for the series-connected chiller, and 146.7 m2, 1.59, 31.45% and $234 562 for the parallel-connected type, respectively. Under the lowest HTA condition, compared with the reference simulation results, the energy and exergy performances are improved, while the annual total cost is higher. The annual total cost is highest when maximizing the exergy efficiency, which is attributed to the increase in the HTA. The operating cost accounts for 27.42% (series type) and 26.54% (parallel type) when the annual cost is the lowest.

MetaCAE: Causal autoencoder with meta-knowledge transfer for brain effective connectivity estimation

Using machine learning methods to estimate brain effective connectivity networks from functional magnetic resonance imaging (fMRI) data has gradually become one of the hot subjects in the fields of neuroscience. In particular, the encoder–decoder based methods can effectively extract the connections in fMRI time series, which have achieved promising performance. However, these methods generally use Granger causality model, which may identify false directions due to the non-stationary characteristic of fMRI data. Additionally, fMRI datasets have limited sample sizes, which significantly constrains the development of these methods. In this paper, we propose a novel brain effective connectivity estimation method based on causal autoencoder with meta-knowledge transfer, called MetaCAE. The proposed approach employs a causal autoencoder (CAE) to extract causal dependencies from non-stationary fMRI time series, and leverages meta-knowledge transfer to improve the estimation accuracy on small-sample data. More specifically, MetaCAE first employs a temporal convolutional encoder to extract non-stationary temporal information from fMRI time series. Then it uses a structural equation model-based decoder to decode causal relationships between brain regions. Finally, it utilizes a model-agnostic meta-learning method to learn the meta-knowledge of the shared brain effective connectivity among different subjects, and transfers the meta-knowledge to the CAE to enhance its estimation ability on small-sample fMRI data. Comprehensive experiments on both simulated and real-world data demonstrate the efficacy of MetaCAE in estimating brain effective connectivity.

A comprehensive formulation for determining static characteristics of mosaic multi-stable composite laminates under large deformation and large rotation

Multi-stable composite laminates are composite materials that exhibit multi-stable states, making them highly suitable for use in morphing structures. These materials are capable of maintaining each stable state without expending any energy. As a result, they are used extensively in numerous applications and garnered the interest of scholars and aerospace organizations. In the context of practical applications, such as morphing structures, it is insufficient for designers to rely solely on common bi-stable composite laminates that exhibit large deformations and medium rotations to achieve their desired objectives. Consequently, based on the objectives of the design, there are two potential resolutions to address this limitation. A designer may utilize mosaic multi-stable composite laminates to achieve a morphing structure that exhibits high flexibility, significant deformation, and substantial rotation. The utilization of a series connection between a bi-stable composite laminate and a symmetric composite laminate results in the formation of a mosaic bi-stable composite laminate with variable stiffness. Furthermore, the amalgamation of two asymmetric composite laminates with inverted orientations engenders a mosaic tri-stable composite laminate. The present research examines the static characteristics of mosaic bi-stable and tri-stable composite laminates. It also seeks to analyze the factors affecting the behavior of these types of laminates. A geometrically exact model was formulated for this objective. Apart from the geometrically exact model, a widely used and uncomplicated model relying on the conventional Classical Laminated-Plate Theory (CLPT) and Von-Karman nonlinear strains was employed. The proposed models were validated through finite element simulations. The system's static equations were derived using the virtual work principle and the Rayleigh-Ritz method. The present study examines and explores quasi-static snap-through behavior between stable states through the application of concentrated forces. The findings indicate a high level of concurrence between the outcomes derived from the geometrically exact model and the finite element analyses, particularly in composite laminates exhibiting significant deformations and rotations.

Stable and high voltage and power output of CEA-MFCs internally connected in series (iCiS-MFC)

The voltage output of a single MFC is normally less than 0.8 V, often less than 0.3 V at maximum power output, which greatly limits the application of MFCs. When MFCs are scaled up, however, increasing reactor size has typically resulted in decreased power density. In this study, we developed a novel MFC configuration that contains multiple cloth electrode assemblies in which the MFCs were internally connected in series (iCiS-MFC). The iCiS-MFC, equivalent to 3 CEA-MFCs, produced a high voltage output over 1.8 V and a maximum power density of 3.5 W m-2 using carbon cloth cathodes containing activated carbon as the catalyst. This power density is 6% higher than that reported for a similar smaller CEA-MFC, indicating that power can be maintained during scale-up with a greater than 33-fold increase in total cathode surface area and greater than 20-fold increase in reactor volume. High stability was also demonstrated based on the performance of the iCiS-MFC over a period of one year of operation. The high power and stability is likely due, in part, to a more efficient means of current collection through the internal series connection, which also avoids the use of expensive current collectors. These results clearly demonstrate the great potential of this MFC design for further scaling-up.

INCREASING Q-FACTOR OF THE DIGITAL SENSOR SIGNALS PROCESSING PATH IN AUTONOMOUS MOBILE ROBOTIC PLATFORMS WITH LIMITED COMPUTING RESOURCES

Abstract. The paper is considered the problem of constructing autonomous mobile robotic platform with the possibility of rearranging their characteristics depending on the operating conditions. A new approach is proposed for calculating the parameters of a new connection with a series connection of low-order components of the same type. The resulting ratio allows you to accurately calculate the frequencies of the n-th connection of the same type components. Such a connection allows increasing the quality factor characteristic of the amplitude frequency characteristic and reducing the bandwidth by 3 times with eight connected filters of the same type. Bandpass filters and notch Butterworth filters are considered. Behavior of the AFC for serial connection is described. Key words: amplitude frequency characteristic, phase frequency characteristic, Industry 4.0-6.0, digital filter, bandpass filter, notch filter, quality factor characteristics, frequency dependent component, notch filter based on bandpass filer, serial connection.

Efficiency Evaluation of Series Connected DC/DC Converters in On-Grid Solar PV System

The grid-connected photovoltaic (PV) system is an important technology for renewable energy applications. It usually consists of three main stages: a PV module, a DC/DC converter and a DC/AC inverter. In these PV systems, Power Conditioning System should have high efficiency and low cost. In this paper, a classification of possible power converter topologies for PV panel integration is introduced. Out of different topologies of DC/DC converter, series connection of boost converters is more suitable converter for PV applications. In order to simulate the steady state efficiencies of the series connection of boost converters and the inverter non-ideal averaged model of these power converters is developed. Then the different elements and control of the (PV) system are implemented in Matlab/Simulink. Using loss analysis, the benefits and drawbacks of series connection of boost converters are shown. This analysis allowed the conception of an optimized architecture constituted by serialized power converters.

Analysis and assessment of the reliability of rail elements

The article conducts a study and calculation of reliability indicators of rail elements of various types, taking into account structural diagrams that include series and parallel connection of elements. Taking into account the climatic characteristics of the Republic of Uzbekistan and taking into account the impact on various areas of the region, the article conducted a study of fastenings for various disturbing factors and ensuring trouble-free operation of system components. The goal of the work was to develop an algorithm for determining optimal parameters. As a result, an assessment of the distribution parameters was proposed taking into account the durability of the elements of the fastening unit. Analytical expressions were developed and a graph was presented.

Математическая модель трехфазно-многофазного трансформаторного преобразователя числа фаз с последовательным соединением катушек каждой фазы вторичной обмотки

The article considers a three-phase-multiphase transformer converter of the number of phases with a serial connection of coils of each phase of the secondary winding, its substitution scheme and a linear mathematical model are given. As an example, the analysis of the operation of a manufactured three-phase-seven-phase transformer converter of the number of phases is performed. As a result of electromagnetic tests of the prototype, the parameters of the replacement circuit of the device are determined. Using a mathematical model, the operating characteristics are calculated and constructed. The results of theoretical calculations and experimental measurements are compared. The largest errors obtained when comparing the calculated and experimental values of efficiency and power factor are 3,5 % and 2,2 %, respectively.

STUDY OF THE REGULARITY CONDITIONS AT SERIAL CONNECTION OF TWO-PORTS

The possibility of preserving the regularity condition for composite two-ports formed by serial connection of the original ones is studied. Numerous textbooks, reference books, collections of problems on the theoretical foundations of electrical engineering provide a rule for determining generalized parameters at the series connection of two-ports by adding the matrices of coefficients Z' and Z'' of the original ones. These sources note that this rule is true only in cases when the regularity condition is met, i.e. pairwise equality of currents at the input and output of each of the two-ports is maintained in any mode of operation of the electrical circuit. When two-ports are connected in series, a new electrical circuit is obtained in which maintaining pairwise equality of currents in two pairs of selected branches can only be a private mode. That is why, it is doubtful that when connecting two-ports in series, the application of the known rule will take place. All possible options for the serial connection of two different two-ports presented by an equivalent T-shaped circuit are considered. To solve the problem, the loop current method is used and a condition is determined under which the pairwise equality of currents at the input and output of each of the two-ports in the load mode is maintained. As a result, it turns out that when connecting two-ports in series, the condition of regularity of the connection is not satisfied. In two of considered cases, the two-ports are converted, and in the third case, the composite two-port is converted into one pass-through two-port. This statement is also confirmed by determining the Z parameters of a composite two-ports by adding the matrices of coefficients Z' and Z'' of the original ones, which is satisfied only in the third of the considered variants.

Sigma-Delta-Over-Fiber With WDM Serial Connection for Distributed MIMO

Sigma-Delta-Over-Fiber With WDM Serial Connection for Distributed MIMO

ВМИКАННЯ ШЕСТИФАЗНОЇ ОБМОТКИ В ТРИФАЗНУ МЕРЕЖУ

Abstract. Recently, many publications have appeared on the Internet about a “combined” winding for a three-phase motor with 24 stator slots. The winding design is two-layer or single-layer. It is proposed to connect two star and delta circuits in one winding. Connected windings with parallel and series connection of phases were considered. Keywords: number of stator slots, winding diagram, parallel branches, number of phases.

Active Voltage Balancing with Seamless Integration into Dual Gate Driver for Series Connection of SiC MOSFETs

Active Voltage Balancing with Seamless Integration into Dual Gate Driver for Series Connection of SiC MOSFETs

Interoperability Study of Wireless Charging System Based on Generalized DD Coil

In recent years, with the popularization of intelligent auxiliary driving technology, wireless charging technology has garnered widespread attention due to its advantages in automation. However, there are still many issues to be resolved before the widespread adoption of wireless charging technology, with a key issue being the interoperability of coupling structures. To achieve adaptive interoperability, this paper proposes a wireless charging system based on dual generalized double-D (DD) coils. The system introduces a receiving structure composed of two generalized DD coils, which can naturally decouple the two coils. At the same time, the system topology employs a series connection of half-bridge rectifiers to enhance the system’s equivalent mutual inductance. Mathematical models and simulation verifications are provided. The proposed approach has been validated through simulations, showing that the system can automatically achieve interoperability with unipolar coils, DD coils, and quadrupolar coils.

Thermal Control of Quasi-2-Level Super-Switch by Power Routing

The requirement of power converters for Medium Voltage (MV) and High Voltage (HV) applications accelerates faster than the development of semiconductor switches capable of handling such voltage levels. For that reason, it is common to use the series connection of semiconductors with auxiliary snubbers. In contrast, an increased number of semiconductors is more likely to cause reliability problems due to increased redundancy, unequal thermal conditions, or different remaining lifetime. On the other hand, the quasi-2-level super-switch (Q2L SS) yields increased flexibility, enabling precise readjustments of the voltage and switching losses of individual devices of the converter due to the utilization of small capacitors. The power routing capability of the Q2L SS to redistribute the switching losses from the overheated semiconductors is presented in this paper. The influence of power routing on performance of Q2L SS is investigated with the Double Fourier analysis and experimental results.

Multiresolution Models of DC Traction Power Supply Systems With Reversible Substations

Reversible substations (RSs) permitting bidirectional power flows can recover the regenerative braking energy of trains in DC traction power supply systems (TPSSs), increasing the energy efficiency of railway systems. To predict their effects on system dynamics and energy savings, the paper develops multiresolution models (MRMs) to simulate the RS roles with different fidelities. A high‐resolution model for the transient simulation replicates a particular topology where a three‐level voltage source inverter is connected to the secondary winding of an existing 12‐pulse rectifier transformer and regulated to keep a constant DC voltage in the inverting mode. Furthermore, it can model the transient effects of pantograph‐to‐line arcing by inserting arc voltage profiles at the train’s input stage. To increase the computation speed in the long‐term energy flow simulation, a low‐resolution model simplifies the rectifiers into a series connection of a diode and a controlled voltage source depicting their nonlinear output characteristics and then places a DC voltage source in parallel to form a reverse path for braking power recovery. In addition, nonlinear conversion efficiencies are introduced to calculate energy flows across substations. The MRMs are tested based on a 1.5 kV DC TPSS and discussed alongside system dynamics under normal operation or pantograph arcing and the consistencies between different models. The RS using bidirectional voltage source converters only is additionally modelled to compare the technical performance of the two topologies in terms of system dynamics and energy efficiencies.