Capacity Margin Research Articles

Autonomous construction of lunar infrastructure with in-situ boulders

Significant infrastructure is required to establish a long-term presence of humans on the lunar surface. In-situ resource utilization (ISRU) is a fundamental approach to ensure the viability of such construction. Here, we investigate the feasibility of constructing blast shields as one example of lunar infrastructure using unprocessed lunar boulders and an autonomous robotic excavator. First, we estimate the volume of unprocessed material required for the construction of blast shield segments. Secondly, we quantify the amount of available boulders in two exploration zones (located at the Shackleton-Henson Connecting Ridge and the Aristarchus Plateau pyroclastic deposit) using LRO NAC images and boulder size-frequency distribution laws. In addition, we showcase an alternative approach that relies on Diviner rock abundance data. Thirdly, we use a path planning algorithm to derive the distance, energy, and time required to collect local material and construct blast shield elements. Our results show that our construction method requires two orders of magnitudes less energy than alternative ISRU construction methods, while maintaining realistic mission time and payload capacity margins.

Photovoltaic Hosting Capacity Margin due to State Estimation Error

Photovoltaic Hosting Capacity Margin due to State Estimation Error

Urban distribution network planning and zoning design based on improved K-means clustering in low carbon background

Abstract Aiming at the problem that the traditional algorithm is difficult to adapt to the chaotic planning of urban distribution network and the uneven distribution of load points, an improved K-means clustering algorithm based zoning planning method of urban distribution network is proposed. Firstly, considering the effect of the capacity margin on the partition, the weighted factor is introduced to improve the Euclidean distance. Secondly, considering the selection of power supply units according to the distribution characteristics of the substation, the distance between the cluster center and the substation is calculated. Finally, a distribution network zoning planning model with the maximum number of inter-station power supply units and the minimum total Euclidean distance of power distribution as the objective function is constructed. Finally, taking the transformation of a distribution network in Fujian Province as a practical engineering example, the results show that the average difference of load partition obtained by the improved K-means clustering algorithm is reduced by 34.35% compared with the traditional method.

Capital market liberalization and firm export performance: evidence from China’s Shanghai-Hong Kong and Shenzhen-Hong Kong Stock Connect programmes

ABSTRACT Using a quasi-natural experiment method, this study examines the effects of the Shanghai-Hong Kong and Shenzhen-Hong Kong Stock Connect (SHKS) programmes on Chinese listed firms’ export performance. We find that the SHKS positively correlates with firms’ export performance, enhances export capacity, and affects export binary margins. The SHKS influences export capacity and binary margins by improving production efficiency, promoting R&D, and easing financing constraints. Finally, the positive effects of the SHKS are particularly pronounced for state-owned enterprises (SOEs), manufacturing firms, and highly financialised firms. These findings contribute to a deeper understanding of the impact of China’s ongoing capital market liberalization on listed firms’ export performance, providing valuable insights for policymakers.

Margin of bearing capacity of one-way straight mortise-tenon joints based on inspection of apparent damage and rotation angle

In essence, safety evaluation of damaged mortise-tenon joints (MJs) involves checking whether the joints have sufficient residual bearing capacity. However, the load, which is necessary in the calculation process, is difficult to observe in practice, resulting in insufficient reliability of the evaluation results. Thus, this study proposes the concept of a margin of bearing capacity (MBC) of an MJ and presents a calculation method for assessing the safety of one-way straight mortise-tenon joints (OSMJs). In the calculating process, the load was replaced with the observed apparent damage and rotation angle. First, the MBC includes the influence of joint damage and rotation angle on the residual moment bearing capacity of the joint. Second, the apparent damage to an OSMJ is simplified to average section loss rates in the height and width directions, which reduces the amount and difficulty of data acquisition. Third, the damage model of an OSMJ included in the proposed calculation method establishes the transforming relationship between the measured average section loss rate and the damage setting on the model, and avoids the influence of uneven distribution of the actual size reduction on the calculation of the residual moment bearing capacity. The results of unidirectional pushover tests of several damaged and intact OSMJ models showed that most absolute errors between the calculated and measured MBCs were less than 0.04, indicating the accuracy of the proposed method for practical safety assessment of damaged OSMJs.

Moderate mass loss enhances flight performance via alteration of flight kinematics and postures in a passerine bird.

Many birds experience fluctuations in body mass throughout the annual life cycle. The flight efficiency hypothesis posits that adaptive mass loss can enhance avian flight ability. However, whether birds can increase additional wing loading following mass loss and how birds adjust flight kinematics and postures remain largely unexplored. We investigated physiological changes in body condition in breeding female Eurasian tree sparrows (Passer montanus) through a dietary restriction experiment and determined the changes in flight kinematics and postures. Body mass decreased significantly, but the external maximum load and mass-corrected total load increased significantly after 3days of dietary restriction. After 6days of dietary restriction (DR6), hematocrit, pectoralis and hepatic fat content, take-off speed, theoretical maximum range speed and maximum power speed declined significantly. Notably, the load capacity and power margin remained unchanged relative to the control group. The wing stroke amplitude and relative downstroke duration were not affected by the interaction between diet restriction and extra load. Wing stroke amplitude significantly increased after DR6 treatment, while the relative downstroke duration significantly decreased. The stroke plane angle significantly increased after DR6 treatment only in the load-free condition. In addition, the sparrows adjusted their body angle and stroke plane angle in response to the extra load, but stroke amplitude and wingbeat frequency remained unchanged. Therefore, birds can maintain and even enhance their flight performance by adjusting flight kinematics and postures after a short-term mass loss.

Seismic assessment and qualification of acceleration-sensitive nonstructural elements through shake table testing: Reliability of testing protocols and reliability-targeted safety factors

Shake table testing represents the best option for assessing and qualifying acceleration-sensitive nonstructural elements (NEs). Several testing protocols are defined in regulations and codes and implemented in the literature, but no commentaries or literature studies provide information regarding the expected reliability or recommend applicative safety factors. The study investigates the seismic reliability of shake table testing protocols for seismic assessment and qualification of acceleration-sensitive NEs. Numerical analyses are carried out considering an incremental procedure and modeling NEs as inelastic single degree of freedom (SDOF) systems, over a wide range of frequencies of interest and NE structural properties. Real floor motions recorded in instrumented reinforced concrete (RC) buildings are considered as a reference. The reliability is estimated considering several damage states and various floor motion sets. In particular, the seismic capacities associated with the real (shake table protocol) floor motions are considered as actual-demand (nominal-capacity) measures, and the demand to capacity margin is meant as the protocol overestimation of the NE capacity. In the light of the estimated protocol reliability, reliabiliy-targeted capacity safety factors are assessed, and applicative factor abaci and closed-form criteria are proposed.

Configuration Optimization and Distributed Formation Control for Tethered Multirotor UAS

This article improves the robustness of tethered multirotor unmanned aircraft systems (UASs) through configuration optimization and controller design. Capacity margin and stiffness matrix are defined to measure the robustness of the system. The relationship between capacity margin and system configuration is analyzed based on a new optimization method. Moreover, the mathematical expression of system stiffness matrix argument with configuration is derived. Based on these two relations, the optimal configuration is determined to strengthen the robustness of the system. Under composite disturbances, it is not trivial to maintain the designed optimal configuration. Thus, a disturbance observer (DO) is developed to eliminate the disturbance generated by the tension force, which is a constant or harmonic signal. In addition, a fixed-time extended state observer (FTESO) is designed to mitigate the external aerodynamic force acting on the UAS. Accordingly, a distributed formation control algorithm based on the designed DO and FTESO is constructed for formation tracking control. Finally, the indoor experiments are demonstrated to validate the proposed strategy.

Dispatch of highly renewable energy power system considering its utilization via a data-driven Bayesian assisted optimization algorithm

In recent years, renewable energy (RE) has been widely deployed, and the power system with high penetration RE is gradually formed. However, the high proportion of RE may threaten transmission security of power systems, which in turn limits its utilization. What is more, the interaction between RE penetration and power system transmission security has not been comprehensively investigated so far. To this end, we develop a bi-objective stochastic dispatch model to investigate the relationship between RE utilization and transmission security. It aims to solve the optimal power system dispatch (OPSD) problem with high penetration RE, in which the RE curtailment and the capacity margin of transmission lines are considered as two objectives of the dispatch problem and formulated in the probabilistic forms. With this, the proposed model is a complicated bi-objective stochastic optimization problem, which is difficult to be solved for traditional optimization algorithms. Therefore, we propose a data-driven Bayesian assisted optimization (DBAO) algorithm, based on Bayesian evolutionary optimization and estimation of distribution algorithm to improve the searching efficiency for the proposed model. Case studies on a modified Midwestern US power system verify the effectiveness of our proposed dispatch model and the optimization algorithm of DBAO.

Optimal Allocation of Primary Frequency Modulation Capacity of Battery Energy Storage Based on Antlion Algorithm

Currently, the integration of new energy sources into the power system poses a significant challenge to frequency stability. To address the issue of capacity sizing when utilizing storage battery systems to assist the power grid in frequency control, a capacity optimal allocation model is proposed for the primary frequency regulation of energy storage. Due to the requirement of a large number of actual parameters for the optimal allocation model, a simulation model of energy storage capacity is constructed based on the characteristics of primary frequency control to provide the necessary parameters. Subsequently, the primary frequency modulation output model of energy storage is established by considering the basic action output, the action in the frequency modulation dead zone, and a certain capacity margin. The antlion algorithm is employed to solve the capacity optimal allocation model. Finally, three groups of experiments are designed and compared to demonstrate the effectiveness of the proposed method in setting the capacity margin, which can increase profit to a certain extent.

Algorithmic Study for Power Restoration in Electrical Distribution Networks

We study the automated power restoration in electrical distribution networks, from the algorithmic viewpoint. During power outages, blackout sections without faults may be able to be recovered early using the capacity margins of surrounding supply sources. However, remote supply sources must be utilized in cases where the capacity margins of the neighboring supply sources are insufficient for the scale of the power outage, which is called multi-stage power restoration. In multi-stage power restoration, the distribution network subject to control becomes broader, and in addition, even healthy sections are subjected to control. In this study, we give an efficient algorithm which determines whether multi-stage power restoration is needed for power restoration, and in either case, the algorithm calculates the switching procedure which recovers power with the minimum number of switch operations. Our algorithm employs a novel algorithmic technique of combinatorial reconfiguration, which enables to maintain power supply to the healthy sections.

Seismic capacity and performance of code-conforming single-story RC precast buildings considering multiple limit states and damage criteria

The seismic capacity and performance of code-conforming precast buildings is assessed in the study. The case study consists in single-story precast buildings designed according to Italian building code considering low to high seismicity sites and varying both geometry layout and soil conditions. The seismic behavior of the buildings is assessed through multiple-stripe analyses performed through nonlinear three-dimensional modeling. Fragility of the buildings is computed by considering several methods, and performance evaluation is based on capacity margin ratios, failure probabilities, and reliability indexes. Damage limitation, life safety prevention, and near collapse prevention performance levels are considered by accounting for multiple damage criteria and damage states, including both local and global approaches and both ductile and brittle failure of beam-to-column connections.The paper provides guidance for implementation of seismic capacity and performance evaluation of precast buildings according to latest advances, considering both European and US approaches. The study proves that the current code prescriptions might not supply adequate seismic performance, especially in the case of more critical soil conditions (i.e., C soil type compared to A soil type). A relatively critical performance was observed for damage limitation and life safety prevention performance levels, whereas collapse performance of the buildings was adequate. The extremely critical condition associated with brittle failure of the beam-to-column connection was also confirmed. The study stresses the need for an enhancement of current design requirements and highlights the need for further investigation into the adequacy of seismic performance of precast buildings and reliability of related code-conforming design.

LOLE Calculation and Capacity Margin Probabilities Neuro-Fuzzy Model Development

LOLE Calculation and Capacity Margin Probabilities Neuro-Fuzzy Model Development

Static Analysis of Wooden Beams Strengthened with FRCM-PBO Composite in Bending

The article presents an analysis of the static work of bent solid-wood beams reinforced with FRCM-PBO (fiber-reinforced cementitious matrix-p-phenylene benzobis oxazole) composite. In order to ensure better adhesion of the FRCM-PBO composite to the wooden beam, a layer of mineral resin and quartz sand was applied between the composite and the wooden beam. Ten wooden pine beams with dimensions of 80 × 80 × 1600 mm were used for the tests. Five wooden beams, unreinforced, were used as referenced elements and another five were reinforced with FRCM-PBO composite. The tested samples were subjected to a four-point bending test in which the static scheme of a simply supported beam subjected to two symmetrical concentrated forces was used. The main purpose of the experiment was to estimate the load capacity, the flexural modulus and the maximum bending stress. The time needed to destroy the element and the deflection were also measured. The tests were carried out based on the PN-EN 408: 2010 + A1 standard. The material used for the study was also characterized. The methodology and assumptions adopted in the study were presented. The tests confirmed a significant increase in destructive force by 141.46%, maximum bending stress by 118.9%, modulus of elasticity by 18.32%, time needed to destroy the sample by 106.56% and deflection by 115.58% compared to the reference beams. The unusual method of wood reinforcement presented in the article can be considered as innovative, characterized not only by a significant load capacity margin exceeding 141%, but also by simplicity of application.

Effect investigation of single-slotted and double-slotted configurations on the corner separation and aerodynamic performance in a high-load compressor cascade

Controlling the corner separation through blade-end slotting has been widely proven advantageous in compressors. This study proposed a new double-slotted configuration and deeply revealed its benefits and flow control mechanisms by compared with the single-slotted configuration. Based on a high-load compressor cascade, the Slotted_A scheme with a single blade-end slot1 and the Slotted_B scheme with a smaller slot2 behind the slot1 were established and detailedly evaluated. The results showed that, since the slot jet with high momentum has efficacious re-energizing effects for the local low-energy fluid, both the two slotted schemes can prevent the original cascade from entering the corner stall condition. But the slot2 jet can further control the end-wall secondary flow developing and separating behind the slot1 in the Slotted_A cascade. Therefore, the Slotted_B scheme behaves better in controlling the corner separation than the Slotted_A scheme, resulting in larger turning angles, smaller vortex structures, and weaker flow blockage. As a whole, the Slotted_A scheme and Slotted_B scheme can respectively increase the turning angle by an average of 0.93° and 1.53°, improve the static pressure coefficient by 18.2% and 21.7% on average, and achieve an average reduction of 38.3% and 43.7% in the total pressure loss. In contrast, the Slotted_B scheme is more advantageous in improving the pressure diffusion capacity and stability margin for the high-load compressor blade.

Collaborative optimization of logistics and electricity for the mobile charging service system

Mobile charging is proposed as a brand-new charging solution in response to the relatively slow construction of charging facilities. Operating a mobile charging service system involves scheduling mobile charging vehicles (MCVs) and batteries owned by the mobile charging service operator (MCSO), which is important to improve its economic efficiency and has a nonnegligible impact on the power system. In this paper, a bilevel optimization framework for logistics and electricity is developed for MCSOs to achieve joint optimization of planning and operation of the mobile charging service system. For transportation logistics, the upper level plans the size of the MCV fleet and routes MCVs in the dynamic traffic network, which can accommodate dynamic changes in the traffic network and make a reasonable route arrangement. For battery energy management, the lower level plans the battery number and optimizes battery charging and discharging at energy service stations, which can track the electric quantity and the state of each battery during the whole process and accurately describe the matching relationship between batteries in a battery swapping scenario. The upper and lower levels are coupled through the battery swapping behavior between MCVs and energy service stations. Through the iteration and adjustment of the two levels, the results optimize the MCSO’s total net profit as much as possible and provide assistance to the power system using service capacity margins. Numerical experiments of a certain scale are used to verify the validity of the proposed framework.

Optimized operation of distributed energy resources: The opportunities of value stacking for Power-to-Gas aggregated with PV

This analysis investigates the business case of a virtually aggregated unit with PV and Power-to-Gas, outlining the added value of enhanced operation modes for the deepened market integration of distributed energy resources in an aggregated form. Based on empirical generation and market data, the presented analysis outlines the added benefit of the so-called value stacking that considers the exploitation of short-term arbitrage opportunities, the provision of secondary and tertiary frequency reserve, and active imbalance management to balance forecast errors. A multi-stage and multi-period optimization approach is presented to generate an aggregated bidding strategy on multiple energy and ancillary service markets. On a case study basis with hourly resolution, annual energy flows and financial outcomes are derived for the modelled plant. Overall, nine different operating modes with different levels of market integration of the aggregated unit are analysed. While static baseline operation results barely profitable, proper integration into energy markets raises the annual cash flow from operating activities to around 60 k€ per aggregated MW. This six-fold increase is accompanied by a much more price-specific dispatch with the equivalent full-load hours of controllable output effectively dropping to about one-third. Integrating the aggregated unit further into balancing markets and performing active imbalance management leverages the freed-up capacity margin and further increases the operational results up to 150 k€ per MW. The provided empirical insights from the case study are beneficial for both practitioners in the energy sector that want to evaluate the potential value of virtual aggregation with enhanced operation and policymakers that consider further regulatory amendments to open markets and enable further integration of new energy sources.

Study on optimization of heat-resistant conductor in line capacity expansion

Due to the low transmission capacity margin of overhead conductors of ACSR type in the existing grid structure, the large-scale grid connection of new energy is greatly limited. However, 60% of IACS heat-resistant conductors have low conductivity and high power loss in the transmission process. Therefore, 61.5% of IACS heat-resistant aluminum alloy conductors with high conductivity are developed for line capacity expansion and reconstruction. The feasibility of 61.5% IACS high conductivity heat-resistant aluminum alloy stranded conductor is analyzed in combination with the example of urban power line capacity expansion and transformation. Under the condition that the call height margin of the original line tower is sufficient, the use of this type of conductor can achieve obvious energy saving effect and effectively improve the transmission capacity and energy utilization rate of the line have been increased. Under the condition that the sag of the conductor and the bearing capacity of the tower do not increase compared with the original line, the capacity of the original line can be increased by at least 1.4 times by using this type of conductor. At the same time, because the conductor uses aluminum clad steel core as the reinforcing core, the corrosion resistance of the conductor is effectively improved to ensure the overhead transmission in coastal areas or heavily polluted areas safe operation reliability of electric lines.

PROBABILISTIC MODELS FOR RELIABILITY ASSESSMENT OF PIPELINE SYSTEMS

The issues of functional reliability assessment within the framework of the pipeline system reliability diagnostics subsystem are considered. The basis for the development of the functional reliability diagnostics subsystem is the breakdown of the pipeline system into emergency repair zones, as well as the replacement of the structure with the macro structure of emergency repair zones, which completely inherits the functional reliability of the system. A mathematical model is formed for each consumer Oi of the pipeline system, where and is the total number of consumers. If several consumers receive the target product from only one zone, then the corresponding mathematical models of functional reliability coincide. The following initial data are used to form a mathematical model of functional reliability in relation to the consumer Oi: calculation model of functional reliability in relation to all consumers. On the basis of emergency repair zones probabilistic models for calculating the functional reliability of pipeline systems have been developed, which are used in the algorithm for calculating the reliability of the entire system. The reliability of pipeline systems at the operational stage is supported by timely prevention and elimination of failures. A probabilistic model has been developed that makes it possible to assess the characteristics of the process of prevention and elimination of failures, to select the optimal parameters. Corresponding numerical calculations have been carried out. From the standpoint of a specialized organization that serves pipeline system, you need to minimize costs, while adhering to certain restrictions, namely: the deviation of the actual time of repair from the normative should not exceed the value, and all requests to eliminate accidents must be fulfilled. This means that the organization has a certain margin of capacity to service emergency calls. Minimize costs within the developed model can be solely due to the number of teams nmin, aiming at their maximum loading. So, we got the mathematical programming problem, which is: to find nmin, which maximizes the load function when the relevant restrictions are met. Keywords: model, subsystem, diagnostics, reliability, pipeline system.

Planning the Development of Electricity Generating Capacity in a One-Zone Electric Power System with a High Share of Renewable Energy Sources

The article addresses matters concerned with planning the generating capacity in an electric power system with a high share of renewable energy sources. A stochastic nature of renewable energy sources (RES) makes them very different from conventional power plants. The RES power output depends on weather conditions, due to which some power system operators do not include them in the power balance. This leads to an excess of installed generating capacity in the electric power system and growth of electricity tariffs for consumers. Probabilistic assessments of system adequacy have shown that RES affect the power balance in the power system and do not require to be fully backed up by conventional generation. The article presents the results of calculating the system adequacy for a test IEEE scheme with different share and structure of renewable energy sources. It is shown that the effect of RES on the power balance is governed not only by the annual electricity output, but by the correlation between the RES power output and load curves. A large share of RES in a power system, entails the need to alter the requirements not only for the conventional generating capacities, but also for their structure. The article presents the results of optimizing the composition of generating equipment for different shares of RES in a power system. It has been shown that, if there are no RES in the power system, preference is given to less maneuverable, but cheaper generation units. With increasing the share of RES in the power system, so does the share of more expensive highly maneuverable units. A method of planning the generation capacity development for a single-zone power system is proposed. The value of the generation capacity margin has been determined based on the system adequacy calculation, and the mix of generating capacities is refined proceeding from optimization of the generating units loading.