The share of power generated from solar photovoltaic (SPV) is increasing drastically worldwide to meet the ever increasing energy demands. The power generated from the solar PV is mainly connected to ...low voltage (LV) distribution systems. However, the power generated from solar PV is intermittent in nature as a results it creates a problem in grid stability and reliability. The technical impacts of high PV penetration into distribution systems are mainly on the current and voltage profiles, quality of power, power balancing, protection, losses in system, power factor, etc. To address aforesaid issues lot of research is required, therefore an extensive literature review is performed considering the current status, impacts and various technical challenges due to high PV contribution. In addition, the proposed study also provides the insights to the possible solutions for voltage rise problem due to high PV penetration in LV distribution system.
The integration of distributed generation (DG) units into distribution networks has challenged the operating principles of traditional AC distribution systems, and also motivated the development of ...emerging DC systems. Of particular concern are the challenges associated with the operation of conventional protection schemes and/or devices. This paper first analyses the fault current characteristics in AC and DC distribution systems; it then presents a comprehensive review of the latest protection methods proposed for distribution systems embedding DGs. In addition, the advantages and disadvantages of each method are outlined and compared. The differences between the protection algorithms employed in/proposed for AC and DC systems are also discussed. Finally, this study identifies the future trends and provides recommendation for researches in the field of protections of DC distribution networks.
This paper aims to solve three issues frequently present in the optimal placement of water quality sensors for protecting water distribution systems (WDSs) from both accidental and intentional ...contamination, namely i) computational intractability of the optimization problem as the size of the WDS increases, ii) unrealistic assumption that sensors are positioned at nodes, rather than on system pipes, and iii) neglecting site-specific practical conditions impacting on sensor installation. The three drawbacks were tackled by i) restraining the optimization to the hydraulic/topological-wise most important pipes, ii) introducing dummy nodes in the middle of these pipes as potential sensor locations, iii) applying a multi-criteria decision-making tool incorporating urbanistic and economic factors for selecting the most effective sensor locations. The method is tested on the WDS of the town of Parete (Italy), showing the manyfold benefits of the solution obtained.
•Water quality sensors are located on pipes of water distribution system, as is in reality.•Weighted topology is used for reducing the computational burden of optimization phase.•Potential sensor locations are defined on the hydraulic/topological-wise most central pipes.•Detection performance, economic and logistic criteria are used to select the best solution.•A weighted multi-parametric Decision Support System for selecting the monitoring layout is proposed.
The rapid development of photovoltaic (PV) systems in electrical grids brings new challenges in the control and operation of power systems. A considerable share of already installed PV units is ...small-scale units, usually connected to low-voltage (LV) distribution systems that were not designed to handle a high share of PV power. This study provides an in-depth review of methods and strategies proposed to prevent overvoltage in LV grids with PV and discusses the effectiveness, advantages, and disadvantages of them in detail. On the basis of the mathematical framework presented in this study, the overvoltage caused by high PV penetration is described, solutions to facilitate higher PV penetration are classified, and their effectiveness, advantages, and disadvantages are illustrated. The investigated solutions include the grid reinforcement, electrical energy storage application, reactive power absorption by PV inverters, application of active medium-voltage to LV transformers, active power curtailment, and demand response. Coordination between voltage control units by localised, distributed, and centralised voltage control methods is compared using the voltage sensitivity analysis. On the basis of the analysis, a combination of overvoltage prevention methods and coordination between voltage control units can provide an efficient solution to increase the PV hosting capacity of LV grids.
The biogeography of eukaryotes in drinking water systems is poorly understood relative to that of prokaryotes or viruses, limiting the understanding of their role and management. A challenge with ...studying complex eukaryotic communities is that metagenomic analysis workflows are currently not as mature as those that focus on prokaryotes or viruses. In this study, we benchmarked different strategies to recover eukaryotic sequences and genomes from metagenomic data and applied the best-performing workflow to explore the factors affecting the relative abundance and diversity of eukaryotic communities in drinking water distribution systems (DWDSs). We developed an ensemble approach exploiting k-mer- and reference-based strategies to improve eukaryotic sequence identification and identified MetaBAT2 as the best-performing binning approach for their clustering. Applying this workflow to the DWDS metagenomes showed that eukaryotic sequences typically constituted small proportions (i.e., <1%) of the overall metagenomic data with higher relative abundances in surface water-fed or chlorinated systems with high residuals. The α and β diversities of eukaryotes were correlated with those of prokaryotic and viral communities, highlighting the common role of environmental/management factors. Finally, a co-occurrence analysis highlighted clusters of eukaryotes whose members’ presence and abundance in DWDSs were affected by disinfection strategies, climate conditions, and source water types.
DC-DC converters are major components of the dc distribution systems. The converters interface with external power inputs, internal dc buses, and loadings of subsystems. The interfacing dc-dc ...converters should be stable locally and globally under mutual interactions through a dc bus within the system. Current research efforts have focused on the analysis of the stability of the dc distribution system subject to small-signal disturbance. However, in practice, the system routinely operates under large-signal disturbances, such as when an additional subsystem is turned on after being connected to the dc bus. In this scenario, the small-signal model may fail to fully describe the dynamics of the system. In this article, we identify and analyze the bifurcation process when the system undergoes abrupt load changes. According to the nonlinear operation of the interconnected system, a large-signal stability criterion is derived. This criterion is simple and can be easily extended to multiple connected converter systems. The criterion is also consistent with the result from bifurcation analysis. Finally, the validity of the proposed criterion is verified by the full-circuit simulations and the experimental works.
AbstractHydraulic models have been widely used to facilitate the design, management, and operation of water distribution systems (WDS). However, model parameters including pipe roughness coefficients ...(PRCs) and nodal demands (NDs) must be calibrated before practical applications, and the calibration accuracy and efficiency is important to enable their wide uptake in practice. This therefore motivates intensive studies to develop approaches for model calibration focusing on either optimization algorithms or numeric methods. Although these previous studies have advanced this research area, the calibration efficiency and effectiveness need to be further improved, especially when dealing with real-world problems. To attain this objective, this paper proposes an efficient numerical approach to simultaneously calibrate PRCs and NDs for WDS. Within this method, the calibration objective function is formulated as a least-square equation, followed by the derivation of iterative formulas according to a local sensitivity analysis. These formulas allow PRCs and NDs to be iteratively updated in an efficient manner until the given convergence criteria are met. To further improve the efficiency, the pipes and nodes are grouped according to their physical properties, which allows the calibration dimensions to be significantly reduced. Additionally, within the calibration process, values of PRCs and NDs are restricted into specified ranges to ensure the calibrated results are practically meaningful. Two case studies are used to demonstrate the utility of the proposed method, and results show that this approach is able to simultaneously calibrate PRCs and NDs efficiently, with the modeled hydraulic parameter values (pipe flows and nodal pressures) matching well with observations.
Parabens are emerging contaminants that have been detected in drinking water. Their presence in DW distribution systems (DWDS) can alter bacterial behaviour, characteristics, and structure, which may ...compromise DW disinfection. This work provides insights into the impact of methylparaben (MP) on the tolerance to chlorine disinfection and antibiotics from dual-species biofilms formed by Acinetobacter calcoaceticus and Stenotrophomonas maltophilia isolated from DW and grown on high-density polyethylene (HDPE) and polypropylene (PPL). Results showed that dual-species biofilms grown on PPL were more tolerant to chlorine disinfection, expressing a decrease of over 50 % in logarithmic reduction values of culturable cells in relation to non-exposed biofilms. However, bacterial tolerance to antibiotics was not affected by MP presence. Although MP-exposed dual-species biofilms grown on HDPE and PPL were metabolically more active than non-exposed counterparts, HDPE seems to be the material with lower impact on DW risk management and disinfection, if MP is present. Overall, results suggest that MP presence in DW may compromise chlorine disinfection, and consequently affect DW quality and stability, raising potential public health issues.
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•Methylparaben (MP) compromises drinking water (DW) chlorination.•MP-exposed biofilms grown in PPL seem to be more tolerant to chlorine disinfection.•HDPE is the best choice for DW plumbing material in the presence of MP.•MP-exposed biofilms are metabolically more active than non-exposed counterparts.•Bacteria treated with chlorine in MP presence are more tolerant to disinfection.
•A coordinated preparation and recovery model is proposed for multi-energy distribution systems under disasters.•Detailed power and thermal network modeling is conducted.•The resilient restoration is ...facilitated via mutual multi-energy support.•Thermal inertia as pipe storage and demand response of the smart buildings are utilized.•A two-stage risk-averse stochastic programming method is used to deal with uncertainties.
Low-probability but high-impact extreme events, such as floods, earthquakes, hurricanes, etc., could threaten the security of a multi-energy system, especially on the distribution level, and cause severe energy supply outages. In this paper, a coordinated restoration method is presented for the renewable energy-integrated multi-energy distribution system (MDS) with several coupling points to coordinate the preparation and load recovery stages after the extreme event. First, the MDS restoration is comprehensively modeled with coupled power and thermal network constraints. Especially, the thermal inertia, which is in the form of pipe storage and thermal demand response of smart buildings to serve as a buffer when the source fails, is fully utilized to reduce the energy supply cost after disasters. Secondly, both preparation and load recovery stage measures are employed to facilitate efficient and reliable system restoration. Furthermore, multiple uncertainties from the renewable generation and power demands in the MDS restoration are dealt with via a risk-averse two-stage stochastic programming approach. Finally, simulation results validate the effectiveness of our method and its superiority over the traditional restoration methods.
This paper develops a novel graph convolutional network (GCN) framework for fault location in power distribution networks. The proposed approach integrates multiple measurements at different buses ...while taking system topology into account. The effectiveness of the GCN model is corroborated by the IEEE 123 bus benchmark system. Simulation results show that the GCN model significantly outperforms other widely-used machine learning schemes with very high fault location accuracy. In addition, the proposed approach is robust to measurement noise and data loss errors. Data visualization results of two competing neural networks are presented to explore the mechanism of GCNs superior performance. A data augmentation procedure is proposed to increase the robustness of the model under various levels of noise and data loss errors. Further experiments show that the model can adapt to topology changes of distribution networks and perform well with a limited number of measured buses.
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