Dynamic and partial reconfiguration are key differentiating capabilities of field programmable gate arrays (FPGAs). While they have been studied extensively in academic literature, they find limited ...use in deployed systems. We review FPGA reconfiguration, looking at architectures built for the purpose, and the properties of modern commercial architectures. We then investigate design flows and identify the key challenges in making reconfigurable FPGA systems easier to design. Finally, we look at applications where reconfiguration has found use, as well as proposing new areas where this capability places FPGAs in a unique position for adoption.
Partial shading is a serious obstacle to effective utilization of photovoltaic (PV) systems since it result in significant output power reduction. PV array reconfiguration strategy is one of the most ...efficient used solutions to overcome negative effect caused by the partial shading in PV systems. This paper presents a comprehensive review of the major existing PV array reconfigurations approaches which are used to overcome the problem of partial shading.
The different approaches are evaluated and compared according to their techniques, advantages and drawbacks.
This work represents an interesting reference for researchers working in the field and a simple guide that serves as help for beginners on PV array reconfiguration.
With the evolution of smart grids, penetration of distributed energy resources (DERs) in the distribution networks has become ever-increasing problem. To improve network reliability, the complexity ...of the two important aspects of adequacy and security must be well assessed. There is a trade-off between adequacy of DERs, and the distribution network security, i.e. improving the adequacy can reduce the security. In this study, enhancement of the distribution network adequacy and security is proposed. In this regard, capacity of simultaneous reconfiguration and DERs sizing are utilised to improve the adequacy and security of an active distribution network. In the reconfiguration process, graph theory concept is adopted to implement a fast reconfiguration method. Since DERs are active, a combined bus and line security index is used to overcome security concerns of their existence. The IEEE 33-bus distribution network as a widely used standard test system in reconfiguration studies, and a practical 83-bus distribution network of Taiwan Power Company (TPC) which is a part of a real distribution network, are used to test the performance of the proposed method. The simulation results demonstrate the performance of the proposed framework.
A multiperiod network reconfiguration to meet the requirement of hourly hosting capacity under a minimal required number of switching operations, taking into consideration the uncertainty of ...renewable generation, is formulated as a nonlinear, nondifferentiable integer optimization problem with nonlinear equality and inequality constraints. A four-stage solution methodology, including an assessment stage, a time-partitioning stage, an optimization stage, and an evaluation stage, is developed to solve the constrained large-scale nonlinear integer optimization problem. A fuzzy C-means clustering algorithm is applied to partition the time period to facilitate the design of a minimum-number switching solution. A hybrid particle swarm optimization algorithm is developed to find an optimal network topology for each partitioned time period. The IEEE 123-bus case and a 1001-node system, three-phase and unbalanced, are used to evaluate the proposed method with promising results.
This paper presents a comprehensive approach to improve the daily performance of an active distribution network (ADN), which includes renewable resources and responsive loads (RLs), using ...distribution network reconfiguration (DNR). The optimization objectives considered in this work can be described as (i) reducing active losses, (ii) improving the voltage profile, (iii) improving the network reliability, and (iv) minimizing the operation costs. The proposed approach also accounts for the probability of renewable resource failure given the information collected from their initial state at the beginning of each day. Furthermore, solar radiation variations are estimated based on past historical data, and the impact of the performance of renewable resources such as photovoltaics (PVs) is determined hourly based on a Markov model. Since the number of reconfiguration scenarios is very large, stochastic DNR (SDNR) based on the probability distance method is employed to shrink the scenarios set, before a self-adaptive modified crow search algorithm (SAMCSA) is introduced to find an optimal scenario. Finally, the IEEE 33-bus radial distribution system and the 86-bus Taiwan Power Company (TPC) system are investigated as two case studies to verify the effectiveness of the proposed method.
Dynamic reconfiguration is an adaptive resilience mechanism that can help address several system design problems. Adaptation through dynamic reconfiguration can improve quality of service, increase ...fault-tolerance, help recover from failures, and prevent and recover from cyber attacks. This mechanism acts primarily by reconfiguring one or more of a system’s resources. While system reconfiguration is advantageous, it may bring disadvantages such as performance and availability degradation during reconfiguration intervals. In this work, we quantify the effectiveness of dynamic reconfiguration as a system resilience mechanism and its impact on performance. We define a failure function that captures the effect of dynamic reconfigurations on a system’s resilience to failures and develop metrics that capture the impact of reconfigurations on a system’s execution time and probability of failure. We also derive analytic models that predict the effectiveness of dynamic reconfigurations on execution time and resilience to failures. Several theorems regarding the tradeoff between resilience to failures and performance and availability are presented. Finally, we define an optimization problem, formalized with the help of these theorems, to determine the optimal reconfiguration frequency to meet performance-resilience tradeoffs.
•An analysis of dynamic reconfiguration of systems for increasing resilience to failures.•A closed-form analytic model for resilience-performance tradeoff of systems adopting dynamic reconfiguration.•An optimization model for a system’s reconfiguration rate under resilience-performance tradeoffs.
Cable-driven parallel robots (CDPRs) have attracted much attention due to their advantages, such as large workspace and excellent load capacity. However, their adaptability to different tasks has ...been limited because of fixed configurations. To improve this, a novel 3-DOF point-mass reconfigurable CDPR (RCDPR) has been designed, and its configuration can be changed by adjusting the positions of multiple cable anchors. Since wrench feasible workspace (WFW) is an essential criterion that describes the configuration characteristics, an optimal reconfiguration planning method is proposed to schedule the sequence and number of all movable cable anchors for adjusting the WFW range. Based on a two-level optimization process, the method can realize static reconfiguration (SR) or dynamic reconfiguration (DR) of the RCDPR. If SR cannot provide the required WFW by finding a static optimal configuration, the WFW range will be dynamically adjusted by DR. Besides, the number of movable cable anchors is minimized in DR by applying L 1 -norm optimization to the anchor velocity sequences. Simulations and experiments are implemented, and the results show that the proposed method can automatically determine when, which, and how the cable anchors move under physical constraints, and reducing the number of movable cable anchors can indeed save actuator energy effectively.
FDI flows to Africa reached $83 billion a record level in 2021, from $39 billion in 2020, due to a large corporate reconfiguration in South Africa. Global FDI flows in 2021 were $1.58 trillion, up 64 ...per cent from the level during the first year of the COVID-19 pandemic of less than $1 trillion. During 1994-2020, Africa, FDI growth was registered about 1.64 per cent per annum and significant at 1 per cent level. In Africa, all the regions having positive growth rate and statistically significant at 5 per cent level. In this paper, employ Johansen co-integration as well as Granger Causality test’ for FDI and GDP during 1994- 2020, before examining these two tests we used Augmented Dickey-Fuller (ADF) test for the stationarity. From the ADF test, the tests were carried out for the series LnFDI and LnGDP. The results shows that LnFDI, and LnGDP are non-stationary at level, but the first difference appropriate significant level. Johansen Co-integration test results reveals; FDI and GDP have long run Co-integration in the entire Africa continent, Central and North Africa regions, remaining, there is no co-integration is accepted. From the Granger causality test results indicates Africa and Southern Africa region, LNGDP is LNFDI granger reason, and also LNFDI is LNGDP granger reason, which indicates that there is direct Granger causality relationship between total Africa continent FDI & GDP and also GDP & FDI. In western Africa region, there is direct Granger causality relationship between GDP and FDI, but there is no Direct Granger causality relationship between FDI and GDP
•A novel Modified Harries Hawk photovoltaic reconfiguration approach is proposed.•Several shade patterns are considered with different array sizes.•Modified Harries Hawk based arrangements enhance ...the power versus the counterparts.•Modified Harries Hawk based reconfigurations provide smooth array characteristics.•Modified Harries Hawk Optimizer proves its superiority in execution time.
Mismatch power loss is the unfortunate problem created as a result of the partial shading phenomenon. To relieve the entire photovoltaic system from this issue, reconfiguring the photovoltaic modules of the considered photovoltaic array is proposed as a favorable solution to disperse the shadow regularly. Therefore, in the current work, a novel developed optimization algorithm named modified harris hawks optimizer is introduced aiming to provide the optimal reconfiguration pattern of the switching matrix to maximize the generated power from the array. The basic version of the harris hawks optimizer is implemented for the same problem over several stages of the analysis, as well. Rearrangements of four patterns of shadow (short broad, long broad, short narrow, and long narrow patterns) are implemented on 9 × 9 photovoltaic array. Moreover, the algorithm is also validated on another two shade patterns with 6 × 4 and 6 × 20 photovoltaic arrays are reported in the simulation part. The results of the proposed techniques are compared to those obtained by a total-cross-tied, competence square, particle swarm optimizer, and genetic-based reconfiguration techniques based on several metrics. The utilized measures are mismatch power, fill factor, percentage power loss, as well as percentage power enhancement. The analysis reveals that the introduced approach enhances the produced power by 33.274%, 27.79%, 6.99%, 7.197% over the first four shaded patterns, respectively and increases the generated power by 20%for the other shade patters. Further, the modified harris hawks optimizer proves its excellency in providing the optimal photovoltaic array configuration in less than 1 s. For intensive justification, the modified harris hawks optimizer reconfiguration approach is validated based on an experimental work for 9 × 9 photovoltaic array with twelve shade patterns during a day from 8 ante meridiem to 7 post meridiem with one hour step. Comparing the produced power based on the modified harris hawks optimizer arrangements to those of total-cross-tied and harris hawks optimizer schemes over the daily hours proves the superiority of the modified harris hawks optimizer interconnected system in generating the highest values of power with a uniform dispersion for the shadow and smooth characteristics with saving the energy by 12.569% compared with that produced by total-cross-tied across the day hours.
In this study, a comprehensive review of achievements in the self‐reconfigurable modular robotics field and future directions are given. Self‐reconfigurable modular robots (SRMRs) are known as ...autonomous kinematic machines that can change their shape by rearranging the connectivity of their modules to perform new tasks, adapt to changing circumstances, and recover from damage. Versatility, reliability, and low‐cost are the fundamental promises of SRMRs when compared with conventional robots. This study emphasized the achievements in the field considering the promises and identified the gaps to be filled in the future. The main distinguishing feature of an SRMR is the capability of configuring its shape during operation. Flexibility in shape supported by appropriate controller strategies brings flexibility in task assignment. Classification of SRMRs is enriched by adding a new section based on assigned tasks to the robot. In addition, the classification based on mechanical and controller design aspects is thoroughly inspected in our study. A new subsection of material selection is introduced in the mechanical design aspects section. Adding these sections to the classification is the main difference between our study and the previous review studies. It is expected that the SRMRs field will have more interactions with materials science in the future. The study is concluded by emphasizing the promises of SRMRs and giving a future vision of the field.
PDF
