Load Sharing Research Articles

Simulating Load Sharing for Resource Constrained Devices

Simulating Load Sharing for Resource Constrained Devices

Distributed Robust Secondary Controller for Voltage Balancing and Proportional Load Sharing in Uncertain DC Microgrids

Distributed Robust Secondary Controller for Voltage Balancing and Proportional Load Sharing in Uncertain DC Microgrids

Load Sharing Between Shaft and Tip of Pile Group in Saturated and Unsaturated Soil

Load Sharing Between Shaft and Tip of Pile Group in Saturated and Unsaturated Soil

Assessment of offshore wind-solar energy potentials and spatial layout optimization in mainland China

Developing offshore wind and solar energy presents a promising solution to reduce carbon emissions. Yet, there has been little focus on the co-location of offshore wind and solar energy, and an absence of methods for optimizing their spatial layout for regional integration. To this end, this study introduces a framework to assess both the technical and economic potential using geographic information system technology, and to seek the optimal spatial layout by combining electricity dispatch simulation and multi-objective optimization. Our results reveal that China's offshore wind-solar generation potential amounts to ∼15.7 × 103 TWh/year, half of which is accessible at a cost of less than €86/MWh. This potential could satisfy 100% of the coastal electricity demands, but the proportion of offshore generation delivered to the grid and the share of load addressed are contingent on specific constraints. We demonstrate that co-located wind-solar farms diminish generation variability and that energy storage markedly reduces PV curtailment during dispatch. Our study underscores the importance of site selection in distant offshore and decentralized placement among locations with varying characteristics. Our study serves as a foundation for offshore wind-solar energy endeavors and offer crucial considerations for the spatial layout optimization of ocean renewable energy utilization.

Investigation on Tuning Power–Frequency Droop for Improved Grid–Forming Inverter and Synchronous Generator Transient Load Sharing

Poor transient load sharing has been observed during the parallel operation of synchronous generators (SGs) and droop-controlled grid-forming (GFM) inverter-based resources (IBRs) in islanded microgrids. This can result in overcurrent protections, causing the inverters to trip, which leads to the collapse of voltage and frequency. In this article, small-signal analysis supported by electromagnetic transients (EMTs) simulation is performed on a detailed model of a microgrid containing IBRs and an SG to identify underdamped modes and their sensitivities to the power–frequency (P-F) droop parameter. Further EMT simulation of a more complex microgrid model with multiple GFM IBRs and SGs is performed to determine whether trends identified from the modal analysis extend to cases where the number of SGs in operation may vary. The objective is to investigate the effectiveness of tuning this parameter to reduce the likelihood of overcurrents in response to load and generation disturbances. The work uncovers both fast and slow modes of concern. Primarily, the findings show that increasing the P-F droop value improves the damping of the slower mode while degrading the damping of the faster mode, leading to an upper limit on the damping improvement of the GFM IBR output current. In EMT simulations of the more complex microgrid, the greatest damping improvement still exhibits significant maximum overshoot. Furthermore, the optimal value of the P-F droop parameter is sensitive to the number of SGs in operation. The conclusion is that tuning the P-F droop parameter is not an effective means to avoid the overcurrent tripping of GFM IBRs during response to large load or generation disturbances when operating in parallel to SGs in islanded microgrids.

A neural network regression model for estimating the lifespan of a Fibre Bundle

Fibre Bundle Models (FBMs) use generalized distributions like the Weibull distribution to study the failure mechanics of disordered material under different load-sharing schemes. Here we attempt to use a simple neural network regression model to estimate the lifespan of Fibre Bundles for axial loading under the Global Load Sharing (GLS) scheme. We find that using neural networks can give a reliable estimate (within ∼2%) of the lifespan for different initial conditions. We also develop a semi-analytical expression for the lifespan of a bundle of fibres. The aim is to establish an empirical relationship using a neural network regression (NNR) method that helps us estimate the ultimate tensile strength. The expressions and methods developed here can be a precursor to future investigation under those cited in the following section(s).

Analysis of factors associated with the failure of treatment in thoracolumbar burst fractures treated with short-segment posterior spinal fixation

BackgroundThe treatment of thoracolumbar burst fractures continues to pose challenges. Although short-segment posterior spinal fixation (SSPSF) has shown satisfactory clinical outcomes, it is accompanied by a relatively high rate of treatment failure. This study aimed to assess factors associated with treatment failure in thoracolumbar burst fractures treated with SSPSF.MethodsThe clinical data of 241 consecutive patients with a traumatic thoracolumbar burst fracture who underwent SSPSF at our center between Apr 2016 and Apr 2021 were retrospectively reviewed. Patients were divided into two groups (failure of the treatment group and non-failure of the treatment group). We compared potential risk factors for the failure of treatment including age, gender, body mass index, smoking, diabetes, vertebral body compression rate, use of crosslinks, percentage of anterior height compression, presence of index level instrumentation, Cobb angle, interpedicular distance (IPD), canal compromise, Load Sharing Classification (LSC) score, use of posterolateral fusion, and pain intensity between the two groups.ResultsA sum of 137 (56.8%) males and 104 (43.2%) females were enrolled where the mean age and follow-up of the participants were 48.34 ± 10.23 years and 18.67 ± 5.23 months, respectively. Treatment failure was observed in 34 cases (14.1%). The results of the binary logistic regression analysis revealed that the lack of index level instrumentation (OR 2.21; 95% CI 1.78–3.04; P = 0.014), LSC score (odds ratio [OR] 2.64; 95% confidence interval [95% CI], 1.34–3.77; P = 0.007), and IPD (OR 1.77; 95% CI 1.51–2.67; P = 0.023) were independently associated with a higher rate of failure of treatment.ConclusionsThe findings of this study revealed that increased rates of treatment failure in thoracolumbar burst fractures treated with SSPSF were associated with factors such as the absence of index level instrumentation, higher LSC scores, and larger IPD. These findings could be helpful in the proper management of patients with unstable thoracolumbar burst fractures.

До питання розвитку транспортних перевезень у регіональному аспекті

Today, globalization trends are becoming evident both in Ukraine and in the world. This approach is aimed at increasing urbanization and the development of agglomerations. Therefore, the issues of development of the transport industry of Ukraine in the regional aspect remain relevant. At the same time, it should be noted that modern multimodal transport networks have their own specific structure. A typical multimodal transport network includes modern components of such elements of the network of such types of transport as road, rail, air, river, sea. The authors identified multimodal transport hubs in the structure of the transport system of Ukraine, analyzed their efficiency in terms of freight and passenger transport. It has been established that the existing distribution of cargo and passenger transportation by modes of transport indicates a certain priority of the use of road transport for all types of communication. At the same time, it should be noted that the automobile mode of transport today in Ukraine and the world is not an example of efficient and economical use of energy resources, has a significant share of the environmental load among other modes of transport, and is not always the objectively optimal option for transporting goods and passengers according to the criteria of reliability, economy and delivery terms. Thus, given that the transport industry of any region, country and at the global level is an important component of the economy, attracts a large number of specialists and affects the pace of development of other sectors of the economy, it is necessary to carefully study the development of this industry at all levels of operation and constantly to direct its development along vectors that constantly change over time. The transport industry at the regional level should also be noted as the basis for building a developed and efficient transport industry in the country. The modern development of the international transport system shows that the gateway or hub can perform the functions of modal and intermodal convergence. Especially if it is a combination of two or more operating modes of different systems. At the same time, the currently operating structures of regional multimodal networks unite the main gateways (hubs), which ensures connection to the international transport system through the sea-land-air interface.

Visual Observation and Analytical Study of the Heat Load Sharing Mode in Multi-Evaporator Loop Heat Pipe

Abstract In this paper, the operating characteristics of the heat load sharing mode of multiple-evaporator loop heat pipe (MLHP) were elucidated based on a visual observation test. The heat load sharing mode is a function of MLHPs that can share the heat between the evaporators through the vapor without electronic power for the heat storage utilization. A visualized MLHP with two evaporators and one condenser was designed and fabricated. To simulate the heat load sharing mode in the MLHP, one evaporator was heated in the range of 40–280 W and the other evaporator was cooled using a water jacket in the range of 10–80 °C. Under the heat load sharing mode, the flow behaviors in the evaporator cores and the compensation chambers were visually observed using borescope cameras, respectively. Moreover, two operating modes (defined as Mode A and Mode B) that affect the maximum heat sharing capability were identified. In Mode A, the heat sharing rate was proportional to the heat dissipation at the cooled side of evaporator, where the capillary force at the wick significantly affected the operation mode. By contrast, in Mode B, the heat sharing rate reached the upper limit and then was constant regardless of the heat dissipation. Furthermore, the proposed concept model can predict the transition of the operation mode from Mode A to Mode B.

Stabilization and Gap Formation of Adjustable Versus Fixed Primary ACL Repair With Internal Brace: An in Vitro Full-Construct Biomechanical Cadaveric Study.

A knotless, tensionable primary anterior cruciate ligament (ACL) repair system preloaded with an internal brace has been released. Currently, there is no biomechanical data on the stabilization and gap formation behavior of the adjustable system when compared with fixed repairs in human ACL tissue. That knotless adjustable suture repair with an internal brace would provide overall higher construct stability and greater load share on the ACL with less gap formation compared with fixed repair. Controlled laboratory study. Human cadaveric knees were utilized for internal braced ACL repair constructs (each group n = 16). Two fixed groups consisting of a single-cinch loop (SCL), cortical button (SCL group), and knotless suture-anchor (anchor group) were compared with an SCL-adjustable loop device (SCL-ALD) group. Testing was performed at 4 different peak loads (50, 150, 250, 350 N) over 4000 cycles at 0.75 Hz including suture repair preconditioning (10 cycles at 0.5 Hz) for SCL-ALD. Specimens were ultimately pulled to failure with a cut internal brace. The final loading situation of the construct and ACL repair with gap formation and ultimate strength were evaluated. Peak elongation at various peak loads showed a significantly higher (P < .001) stabilization of SCL-ALD when compared with both fixed groups. There was a significantly higher (P < .001) load share of SCL-ALD, especially at lower loads (48% of 50 N), and the gap formation remained restricted up to 250 N. With only a little load share on the fixed constructs (<6%) at lower loads (50, 150 N), gap formation in these groups started at a load of 150 N, leading to significantly higher gaps (P < .001). The ultimate failure load for SCL-ALD and anchor groups was significantly increased (P < .001) as compared with SCL. The stiffness of SCL-ALD (62.9 ± 10.6 N/mm) was significantly increased (P < .001). Internal braced knotless adjustable fixation for ACL repair with preconditioning of the suture repaired ligament increased the overall stabilization with higher load share on the ACL and restricted gap formation (<0.5 mm up to 350 N) compared with fixed suture repair. All internal braced repairs restored stability according to native ACL function. Adjustable ACL repair improved the mechanical characteristics and reduced gap formation, but the overall clinical significance on healing remains unclear.

HIGHLY SECURED TRANSFORMER LOAD SHARING SYSTEM USING MICROCONTROLLER

Abstract-The transformer is a static device, which converts power from one level to another level. The aim of the paper is to protect the transformer under overload condition by load sharing. Due to overload on transformer, the efficiency drops and windings get overheated and may get burnt. Thus by sharing load on transformer, the transformer is protected. This will be done by connecting another transformer in parallel through a micro-controller. The microcontroller compares the load on the first transformer with a reference value. When the load exceeds the reference value, the second transformer will share the extra load. Therefore, the two transformer work efficiently and damage is prevented. In this project three modules are used to control the load currents. The first module is a sensing unit, which is used to sense the current of the load and the second module is a control unit. The last module is microcontroller unit and it will read the analogue signal and perform some calculation and finally gives control signal to a relay. A GSM modem is also used to inform the control station about switching. The advantages of the paper are transformer protection, uninterrupted power supply, and short circuit protection. When designing low-voltage power system to the supply large load currents, paralleled lower-current modules are often preferred over a single, large power converter for several reasons. These include the efficiency of designing and manufacturing standard modular converters which can be combined in any number necessary to meet a given load requirement and the enhanced reliability gained through redundancy. Key Word: Transformer, Load Sharing, Microcontroller, Relay Driver

Deep Reinforcement Learning for Dynamic Opportunistic Maintenance of Multi-Component Systems With Load Sharing

Opportunistic maintenance (OM), which shows its superiority on complex multi-component systems by integrating the maintenance activities of multiple components to reduce the maintenance cost, has been widely studied over the past decade. To our knowledge, most of the existing OM works are developed based on fixed maintenance thresholds without fully utilizing the health state of the multi-component system. This article presents an OM optimization problem of multi-component systems with load sharing, solved by a modified proximal policy optimization approach based on deep reinforcement learning algorithm. The load sharing effect is reflected in the hazard rate function, which further changes the failure probability of the components. Meanwhile, the health states can be recovered by executing imperfect maintenance and corrective maintenance. The optimization problem is formulated as an infinite-horizon MDP with mixed discrete and continuous state and action space to maximize the total discounted reward, taking into account the system reliability and the maintenance cost. The difficulty caused by the mixed action space is solved by designing a parameterized action space structure and multi-task reinforcement learning framework. The effectiveness of the proposed algorithm is tested on a four-component system and a real-world scenario configured with the high-pressure feedwater heater system in the nuclear power plant. The results show that the performance of the algorithm is stable when facing large-scale problems. The algorithm proposed in this study also contributes to the imperfect maintenance optimization with state-of-the-art optimization techniques.

Optimal Load Sharing between Lithium-Ion Battery and Supercapacitor for Electric Vehicle Applications

There has been a suggestion for the best energy management method for an electric vehicle with a hybrid power system. The objective is to supply the electric vehicle with high-quality electricity. The hybrid power system comprises a supercapacitor (SC) bank and a lithium-ion battery. The recommended energy management plan attempts to maintain the bus voltage while providing the load demand with high-quality power under various circumstances. The management controller is built on a metaheuristic optimization technique that enhances the flatness theory-based controller’s trajectory generation parameters. The SC units control the DC bus while the battery balances the power on the common line. This study demonstrates the expected contribution using particle swarm optimization and performance are assessed under various optimization parameters, including population size and maximum iterations. Their effects on controller performance are examined in the study. The outcomes demonstrate that the number of iterations significantly influences the algorithm’s ability to determine the best controller parameters. The results imply that combining metaheuristic optimization techniques with flatness theory can enhance power quality. The suggested management algorithm ensures power is shared efficiently, protecting power sources and providing good power quality.

A numerical study on the impact of lubricant rheology and surface topography on heavily loaded non-conformal contacts

The increasing requirement of high-power density (power throughput/ weight) in modern day machines lead to thin film lubrication condition in various machine components (rolling element bearings, gears, cams, etc,) due to severe loading conditions. Surface roughness features and lubricant rheology plays a vital role in thin film lubrication, and significantly affects the lubrication performance and lifetime of machine components. The present work demonstrates surface topography and lubricant rheology effects on the traction coefficient for heavily loaded non-conformal contacts. The load-sharing concept considering elastic-plastic deformation of asperities, and Carreau shear-thinning rheological model is employed to describe the dry rough contacts and non-Newtonian behavior of lubricant. An influence of surface topography parameters such as roughness, skewness, kurtosis, and pattern ratio on the traction coefficient is discussed. From results, it is found that among different surface topographies, negatively skewed surfaces having isotropic surface pattern exhibit minimum traction coefficient. The load share function and the critical rolling speed are determined for various surface topographies which provides further insights into the surface topography effect on traction coefficient. The findings of present study are noteworthy as they provide a theoretical basis for an assessment of the lubrication performance of heavily loaded non-conformal contacts.

Supply-demand side management of a building energy system driven by solar and biomass in Stockholm: A smart integration with minimal cost and emission

As part of the transition to a sustainable future, energy-efficient buildings are needed to secure users' comfort and lower the built environment's energy footprint and associated emissions. This article presents a novel, realistic and affordable solution to minimize the footprint of smart building energy systems and enable higher renewable energy use in the building sector. For this, an intelligent system is being developed using a rule-based automation approach that considers thermal comfort, energy prices, meteorological data, and primary energy use. In order to lower the installation cost and part of the environmental footprint, batteries are not used, and the heat pump's size is decreased via component integration. Also, different renewable resources are effectively hybridized using photovoltaic thermal panels and an innovative biomass heater to increase the share of renewable energy, enhance reliability, and shave peak load. In order to secure feasibility, the suggested framework is assessed from the techno-economic and environmental standpoints for 100 residential apartments in Stockholm, Sweden. Our results show that 70.8 MWh of renewable electricity is transferred to the local grid, and the remaining 111.5 MWh is used to supply the building's needs and power the electrically-driven components. The biomass heater meets more than 65% of the space heating demand, mainly at low solar power and high electricity prices, illustrating the value of integration strategies to reduce the system's dependability on the local grid. The results further reveal that most energy purchases during the cloudy days and nights are repaid through the sale of excess renewable production during the warmer hours, with a bidirectional connection with the grid. The monthly energy cost is less than 140 $/MWh for most of the years. The cost can be held low due to the exclusion of batteries and minimizing the heat pump size. The proposed system has a low emission index of 11.9 kgCO2/MWh and can reduce carbon dioxide emissions by 70 TCO2/year compared to using the supply from the Swedish energy mix.

Impacts of Kuwait’s proposed renewable energy goals on grid operations

ABSTRACT Kuwait’s policy of achieving 15% renewable energy by 2030, announced in 2012, has been diverted from its original intent. Today, Kuwait’s renewable energy goal is to meet 15% of its projected peak load by 2030. To examine the actual outcomes, a comparison is offered between the original policy: annual energy share, the current policy: peak capacity share, and two other policies: installed capacity share and peak load share. The results demonstrate how these policies lead to drastically different outcomes. The total installed renewable energy capacity ranges from 4 GW to 27 GW; the total produced energy from renewables ranges from 8 TWh to 44 TWh; and the flexibility requirements ranges from 1.6 GW to 20 GW per hour.

INFLUENCE OF MANUFACTURING ERRORS ON THE BEHAVIOUR OF A TWO-STAGE PLANETARY GEAR TRAIN

Planetary gear train is widely used in large heavy-duty machineries such as helicopters and ships due to its large transmission ratio, strong bearing capacity, and small size. In this paper, and the load sharing ratio (LSR) and overall transmission error (TE) of a two-stage double-helical planetary gear train are studied. Firstly, the static balance equations of the double-helical planetary gear train are established. Then, the LSR under different mesh phasing and the overall TE are obtained by solving the equations. Finally, different errors such as pinhole position and eccentricity error are taken into consideration and the influence of errors on load sharing ratio and transmission error are analyzed. The results show that the excitation frequency of transmission error is related to the number of planet gears and mesh phasing and the LSR is related to the mesh phasing, especially to the sequentially phased transmission. It is also concluded that the excitation frequency of the output element of the two stages can be seen as the superposition of the mesh frequencies of each stage and that the studied errors have a significant impact on the LSR and the TE. Keywords: Double-helical planetary gear; Meshing phase; Load Sharing Ratio, Transmission Error.

Optimal Generation Capacity Allocation and Droop Control Design for Current Sharing in DC Microgrids

Considering the increasing amounts of renewable energy generation and energy storage required to meet ambitious environmental goals, it is clear that the next generation of power grids will be dominated by converter-connected devices. In addition, the increasing share of loads connected via power electronics and the general transition to non-synchronous grids with distributed generators make dc microgrids an attractive future alternative. However, achieving optimal utilization of distributed generators in such cases is a complex task, as the performance depends on both the grid and control design. In this paper, we consider such a case where the optimal utilization of distributed generators is achieved by optimal power sharing while taking into account the grid topology, the available generators, and the way they are controlled. For the latter, we consider a droop-based decentralized control scheme whose primary objective is to achieve voltage regulation in the allowable operating range. A novel mixed-integer optimization approach is proposed to identify the optimal converter size and location in the network so that the microgrid can operate safely and with optimal use of the available resources. Time-domain simulations are used to validate the proposed approach and demonstrate its robustness to uncertainty in generator availability.

Inter network roaming between independently managed satellite networks

With the recent wide-spread adoption of internet connectivity to consumers on airplanes, ships, and other mobile platforms offered by various service providers and via multiple satellite systems, there is a need to integrate these independently owned and managed systems with their individual coverage limitations into a combined broad footprint and coverage area with seamless roaming and handovers. This paper describes a method of configuration and service provisioning of satellite terminals on mobile platforms, that allows seamless roaming between networks, that uses advanced security necessary between independently managed satellite networks to effectively allow global coverage for mobility terminals. Partner Roaming Agreements can be created between networks where network operator define Service Plan Equivalence Mapping in visitor network based on terminals&apos; home network service plans. Inter satellite network roaming can also be utilized to load share in case of overlapping coverages. Secure communication mechanisms between the various network management systems are described which are needed between partner networks to provide for encrypted and authenticated communication with the roaming terminals.

Tribological Aspects Affecting Surface durability of Tooth-Sum Altered Spur Gears: A Load Sharing Approach

The performance of tooth-sum altered (ATS) gears is determined by the factors influenced by their profile geometry. This study aims to explore the influence of gear geometry modification on tribological aspects that affect surface wear in ATS spur gears. A computer code is developed to simulate surface wear numerically, using Archard's wear model, Greenwood-Williamson micro-asperity contact model, and Johnson’s load-sharing approach. The outcomes of the study indicate that the low contact ratio ATS gears promote the formation of thick oil film owing to reduced specific sliding and increased speed. However, high contact ratio ATS gears create unfavorable operating conditions resulting in extreme boundary lubrication. The effectiveness of lubricant oil film in reducing wear in ATS gears is associated with its modified profile, sliding velocities, load bearing, operating temperature, and oil viscosity.