Parallel Connection Research Articles

A Study on the Thermal Behavior of Series and Parallel Connection Methods in the Process of Hydrogenation of Ship-Borne Hydrogen Storage Cylinder

As a subdivision of the hydrogen energy application field, ship-borne hydrogen fuel cell systems have certain differences from vehicle or other application scenarios in terms of their structural type, safety, environmental adaptability, and test verification. The connection method of the ship-borne hydrogen storage cylinder (SHSC) is very important for the hydrogen fuel cell ship, and the structural parameters of the SHSC are particularly important in the hydrogen refueling process. To ensure the safe and reliable operation of the hydrogen-powered ship, research on the filling of the SHSC under different connection modes was carried out during refueling. In our study, a thermal flow physical model of the SHSC was established to research the hydrogen refueling process of the series and parallel SHSCs. The influence of series and parallel modes of the SHSCs on the hydrogen refueling process was explored, and the evolution law of the internal flow field, pressure, and temperature of series and parallel SHSCs under different filling parameters was analyzed by numerical simulation. Our results confirmed the superiority of the parallel modular approach in terms of thermal safety during refueling. The results can supply a technical basis for the future development of hydrogen refueling stations and ship-board hydrogenation control algorithms.

A High CMRR Differential Difference Amplifier Employing Combined Input Pairs for Neural Signal Recordings.

This article introduces a Combined .symmetrical and complementary Input Pairs (CIP) of a Differential Difference Amplifier (DDA), to boost the total Common-Mode Rejection Ratio (CMRR) for multi-channel neural signal recording. The proposed CIP-DDA employs three input pairs (transconductors). The dc-coupled input neural signal connection, via the gate terminal of the first transconductor, yields a high input impedance. The high-pass corner frequency and dc quiescent operation point are stabilized by the second transconductor. The calibration path of differential-mode gain and Common-Mode Feedback (CMFB) is provided by the proposed third transconductor. The parallel connection has no need for extra voltage headroom of input and output. The proposed CIP-DDA is targeted at integrated circuit realization and designed in a 0.18-μm CMOS technology. The proposed CIP-DDAs with system CMFB achieve an average CMRR of 103 dB, and each channel consumes circa 3.6 μW power consumption.

Performance study of an energy harvester with multiple piezoelectric disks in parallel connection for water pressure pulsation

Water hydraulic pump is a crucial component of the water hydraulic system, and it generates periodic pressure pulsation due to its inherent characteristics. To harvest the vibration energy from the pressure pulsation, an energy harvester with multiple piezoelectric disks in parallel connection is proposed. Two prototypes are fabricated to analyze the effect of the number of piezoelectric disks on the energy harvesting characteristics under different pressures and resistances. Parameter matching is also carried out to obtain high root mean square (RMS) voltage and average power. For both prototypes, the cyclical change of deformation is caused by the pressure pulsation, leading to transient variation of voltage. Moderate thickness of piezoelectric ceramic and small thickness of copper substrate are advantageous for generating higher electrical energy output. Pressure pulsation significantly affects the harvested voltage and power, with the main influencing factor being the pulsation amplitude rather than static pressure. Additionally, transient voltage and RMS voltage increase with increasing resistance, while average power first rises and then falls. Comparing the two prototypes, both voltage and optimal resistance decrease when the number of piezoelectric disks in parallel connection increases. The average power and power density with two piezoelectric disks can reach 447 μW and 4.56 mW cm−3 under 3 MPa and at a resistance of 20 KΩ. This research provides guidance for the design, optimization and application of piezoelectric energy harvesters in water hydraulic system.

Recommendation Of RLC Circuit and Its Uses in Electronic Devices

This paper introduces RLC circuit, which is a circuit with resistor, inductor, and capacitor. This paper will introduce the different types of RLC circuit and will show the uses of them in electronic devices. Equations are used to express the relationship of the different elements in the circuit, and theories are introduced to prove some equations. In addition, figures can also show the different types of connections of RLC circuit, including theoretical series and parallel connection and connection that will come in use in electronic devices. This first part of article will enable people to understand what RLC circuit is, the second part will use equations to prove certain theories, and the third part of the article will introduce how RLC circuit is used in radios, and the different ways of connection which cause the circuit to receive waves, and filter waves. The final part will conclude all the parts mentioned in the article.

Control strategy to improve the power factor with a hybrid filter

Nowadays an electrical system must provide adequate electrical power quality so that it meets the international standards. To do this, this paper develops a control strategy for an active compensator based on a hybrid filter topology. This topology is formed by an active power filter of series connection and a passive filter of parallel connection. The proposed strategy is based on minimizing the rms value of the voltage at the point of common coupling so that the source transfers the power demanded by the load. Thus, the determination of the reference signal is posed as a constrained optimization problem. The strategy was proposed for four-wire systems and it allowed the compensation of current harmonics, reactive power and neutral current. Finally, a simulation platform in Matlab-Simulink was developed. This allowed the verification of the new strategy for different types of loads.

Stability Analysis of Distributed Multi-Converter System

This paper discusses dynamic stability and performance of current control scheme for parallel connection of pulse-width modulated (PWM) voltage source converters (VSCs) fed by distributed energy recourses (DERs) across the distribution level of power grid. The controller has feedback compensation and limits the current harmonics while featuring fast regulation for multi-converter system. The controller enables islanded and grid-connected operations of DERs, dynamically. The load dynamics will be included in the stable control loop to provide perfect regulation of the voltage at the point of common coupling (PCC). The current controller is tested under the considerations of system delays. In the islanded mode, one of the controllable units provides voltage and frequency control as a master controller and the other units operate based on the grid-connected control strategy. The stability assessment of the system is presented based on a detailed simulation. The simulation results show that the controller for the islanded two-parallel controllable DER can ensure the stability of the system when converters are tied together. In the other hand, the weakness of the current control based method is drawn out while mismatch coupling condition.

An assembly accuracy analysis approach of mechanical assembly involving parallel and serial connections considering form defects and local surface deformations

Tolerance analysis including tolerance model representation and assembly deviation propagation, is a key approach for predicting and controlling the assembly accuracy of mechanical product. In the current researches, the Non-Gaussian skin model shapes (NSMS) is a valid approach to represent tolerance model of parts considering form defects. However, there is a lack of valid methods to analyze the deviation propagation of mechanical assembly involving parallel and serial connections due to without considering the effect of local surface deformations between mating surfaces (LSDMS) in assembly process, which may affect the assembly accuracy analysis. In addition, the calculation of relative positioning deviation between mating surfaces (RPDMS) of parallel connection has not been combined with practical assembly process closely, which may lead to the loss of accuracy. To address above problems, this paper proposes an assembly accuracy analysis approach of mechanical assembly involving parallel and serial connections considering form defects and LSDMS. Firstly, an integrated Jacobian-NSMS model is presented based on NSMS and Unified Jacobian-Torsor model, which combines the advantages of efficient deviation propagation analysis and high-fidelity representation of tolerance. Secondly, based on the registration method and the difference surface method for solving RPDMS of serial connections, the RPDMS of parallel connection is obtained by performing algebraic operations combining with practical assembly process, by which the assembly involving parallel and serial connections is transformed into a new serial assembly, then the assembly deviation for mechanical assembly involving parallel and serial connections considering form defects and LSDMS can be calculated with the integrated Jacobian-NSMS model. Finally, a case study is presented to verify the proposed method, the result shows that there is different effect on assembly deviation between considering and without considering form defects and LSDMS, which indicates that the form defects and LSDMS have non-ignorable effect on assembly accuracy analysis of mechanical assembly involving parallel and serial connections. In addition, the result shows there is different effect on assembly deviation between considering and without considering practical assembly process in parallel connection. It is expected that the proposed method can help improve the assembly accuracy of mechanical assembly involving parallel and serial connections.

On the Combinatorial Diameters of Parallel and Series Connections

On the Combinatorial Diameters of Parallel and Series Connections

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.

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.

A bidirectional quasi-zero stiffness metamaterial for impact attenuation

A reusable bidirectional quasi-zero stiffness metamaterial (BQZS-MM) with quasi-zero stiffness zones under compressive and tensile loads is proposed, which can be employed for bidirectional kinetic energy absorption and impact attenuation. The BQZS-MM is characterized by the parallel connection of positive stiffness components and negative stiffness components to generate the BQZS. At the unit level, the bidirectional BQZS characteristics are analyzed theoretically and validated by simulations. The research further discusses the span and amplitude of the quasi-zero stiffness zone with structural parameters and serial-parallel mechanisms. The effect of quasi-zero stiffness zone’ span and amplitude on dynamic performance is investigated. The physical prototypes are manufactured by selective laser sintering technology. The BQZS and reusability characteristics of BQZS-MM are examined by three repeated tensile and compressive tests. In comparison to existing metamaterials with bidirectional negative stiffness in one principal direction, under compressive and tensile loads, energy absorption, specific energy absorption, energy density, and crushing force efficiency of BQZS-MM have been significantly improved. During dynamic analysis, BQZS-MM attenuates bidirectional response acceleration peaks and achieves bidirectional impact attenuation. However, existing metamaterial with unidirectional quasi-zero stiffness can only achieve unidirectional impact attenuation. The BQZS-MM features novel BQZS mechanical characteristics, serving as a guide for creating brand-new buffer energy absorbers.

High-Performance 3D Stacked Micro All-Solid-State Thin-Film Lithium-Ion Batteries Based on the Stress-Compensation Effect.

A novel all-solid-state thin-film lithium-ion battery (LIB) is presented to address the trade-off issue between the specific capacity and stabilities in a conventional LIB. Different from the conventional one, this LIB device consists of two same LIB components located at the front and back surfaces of the substrate, respectively. These two LIB components form parallel connection by using the conductive through vias distributed in the substrate. Compared with the conventional one, this LIB device doubles the areal specific capacity. More importantly, due to the stress-compensation effect, this device effectively suppresses the stress induced by its volume changes resulting from the lithiation/delithiation processes and thermal expansion. Consequently, this device shows good cycling and thermal stabilities even when working at an industrial-grade high temperature of 125°C. To further improve the specific capacity without sacrificing the stabilities, a 3D stacked LIB is successfully realized by using this LIB device as the cell, in which each cell is parallelly connected by using the above-mentioned conductive through vias. This 3D stacked LIB is experimentally demonstrated to obtain high specific capacity (79.9µAhcm-2) and good stabilities (69.3% of retained capacity after 100cycles at 125°C) simultaneously.

Three-Dimensional Tolerance Analysis and Allocation for Valve Gap of Engine

The engine is a typical complex machine with many mechanisms and high precision. The tolerance of the valve gap is an accumulative result of component tolerances on the valve mechanism, which is very critical to engine performance. The current tolerance analysis is carried out using the traditional linear dimension chain, and it is difficult to consider a large number of geometric tolerances. The analysis result is not consistent with reality. Based on an innovative three-dimensional tolerance model, i.e., the unified Jacobian-Torsor model, tolerance analysis and allocation for valve gap were presented in this paper, where large geometric and partial parallel connections were taken into consideration. For the special conical structure in the valve mechanism, the expression and variation of the conical torsor were deduced. At last, a real engine was selected as an example of the analysis process. Sufficient comparison and discussion were made for the results, which demonstrated the effectiveness of the method.

Equivalent thin-layer temperature field model (ETTM) for bolted rotors to describe interface temperature jump

Improving the accuracy and efficiency of predicting the temperature field is a crucial requirement for iteratively calculating and online monitoring the temperature field, particularly for combined structures. The heat flow movement is impeded by incomplete interface contact, resulting in a temperature jump. To address this, the equivalent thin-layer temperature field model (ETTM) is proposed to replace the interface thermal contact conductance (TCC) model. Firstly, the fractal TCC model of a bolt connection is derived based on fractal geometry. Subsequently, the contact surface of the circumferential bolt connection is considered to be the parallel connection of multiple bolt thermal resistances. The TCC of the equivalent thin-layer is obtained. Building on this, the ETTM of the built-up rotor structure is developed. Finally, a temperature field model of the bolted rotor is derived. The validity of models is verified by comparing the model proposed in this paper with the previous research findings and ANSYS analysis results. Numerical simulation results reveal that TCC is influenced by several factors: contact pressure, the nominal contact area within the fractal domain, fractal dimension, fractal roughness, and the root mean square (RMS) height. Furthermore, the effects of the thickness of the thin layer model and the thermal conductivity of the material on heat transfer are examined. Ultimately, the findings indicate that heat transfer at the interface is significantly impeded by thermal contact resistance across various temperature boundary conditions. Notably, lower contact pressure intensifies this impedance.

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.

Precise Motion Control for Self-reconfiguration Wave-like Crawling Robots in Parallel Connection with Limited Resources

Precise Motion Control for Self-reconfiguration Wave-like Crawling Robots in Parallel Connection with Limited Resources

Development of a model for diagnosing rotor conditions in the parallel connection of synchronous generators with the network

This article introduces a model for diagnosing rotor angular changes in generators when integrating synchronous generators into the grid. The model addresses issues like leakage currents, reverse moments, and stator bushing short circuits caused by rotor angle changes during parallel addition of large-capacity synchronous generators. Its unique approach simplifies precise synchronization during parallel connection and enables continuous graphical monitoring of rotor angle changes through computer programs. Experimental results from 110 MW synchronous generators at "Navoi Thermal Power Plant" JSC validate the model's effectiveness. It is designed to resolve rotor angle change challenges when integrating synchronous generators of varying capacities into existing power plants, ensuring uninterrupted electricity supply and optimizing technical and economic performance. The model aims to enhance operational efficiency and reduce costs for electricity consumers.

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.