Urban Distribution Network Research Articles

Lessons learned from Milan electric power distribution networks data analysis during COVID-19 pandemic

COVID-19 pandemic has been a disruptive event from health, social, and economic points of view. Besides that, changes in people’s lifestyles, especially during the 2020 lockdowns, also affected energy networks. COVID-19 pandemic has resulted in a significant decline in electricity demand. The lockdown measures applied to handle the health crisis have caused the most relevant energy impact of the last years. In this paper, the local experiences of the distribution network of Milano, a city in northern Italy, are reported. The analysis starts with a summary of the restrictions imposed during 2020 and focuses on both active and reactive power flows, and faults. To this end, a comparison with 2019 data has been performed, highlighting the main differences with 2020. The outcome of the analysis is a valuable tool to predict urban distribution networks behavior during times of disruption, helping distribution system operators to prepare feasible short-term and long-term resilience plans.

Economic Analysis of Incremental Distribution Network Construction of Urban Industrial Park under the Background of Smart City

The distribution system of urban industrial parks involves many relevant subjects, and there is an urgent need to effectively evaluate the technical and economic methods of distribution systems of urban industrial parks. This paper gives the architecture of a smart city and analyzes the characteristics of the incremental distribution network of the urban industrial park. The life cycle cost model of distribution network equipment is established, and the method for calculating the life cycle cost of distribution network equipment under multiple strategies is studied. The application of the economic evaluation of the urban distribution network is described in detail, and its evaluation indicators under the current power grid, the single plan of the planned grid, and the multiple plans of the planned grid are introduced. The results show that the evaluation method in this paper has the advantages of good versatility and strong operability for the economic evaluation of incremental distribution network construction.

Configuration strategy and application for distribution network protection based on standalone 5G

The 5G network, with its characteristics of wide coverage, high reliability and low delay communication, has a high application value in solving the “last kilometer” problem in interconnection between the terminal equipment of a distribution network. To improve the practical level of distribution network protection based on standalone 5G, we analyze the requirements of communication resource for distribution network protection firstly. Then, given the overall structure of 5G distribution network protection, a time synchronization scheme with higher reliability is proposed by means of homologous transmission of clock signal and data signal. At the same time, differential protection and regional protection are applied in an urban distribution network. The differences between the two protection methods in overhead lines and cables are analyzed. The results show that overhead lines are recommended for regional protection, and cables can be compatible with differential protection and regional protection.

Resilience enhancement for urban distribution network via risk-based emergency response plan amendment for ice disasters

High-impact low-probability (HILP) events, such as ice disasters, result in large losses of critical loads (CLs) in the urban distribution network (UDN). Thus, emergency response plans are usually made against various HILP events to improve the UDN resilience. However, these emergency plans are usually made under incomplete and imperfect information; thus, the execution of these plans may not be effective and even risky under the real situation. Therefore, in this paper, a multi-stage UDN resilience enhancement framework is proposed for tackling this challenge. At the first stage, the distribution system operator (DSO) forms typical failure scenarios based on historical data of damage to electric components under ice disasters. Under each scenario, the DSO designs a response plan to minimize the CLs’ loss and associated costs. Thanks to the updated information on the ice disaster, at the second stage, DSO makes a risk assessment on the planned emergency response. If the risk is unacceptable for any period of the ice disaster, at the third stage, DSO amends the response plan to alleviate the “second-order” impacts on CLs, distribution lines, and distributed generations (DGs). Finally, simulations on the modified IEEE-69 system, including 10 CLs and some DGs, show that the proposed framework can effectively reduce second-order impacts due to both the ice disaster and its impact on the execution of originally planned emergency response.

Improvement of the performance of NSGA-II and MOPSO algorithms in multi-objective optimization of urban water distribution networks based on modification of decision space

Water distribution networks require huge investment for construction. Involved people, especially researchers, are always seeking to find a way for decreasing costs and achieving an efficient design. One of the main factors of the network design is the selection of proper diameters based on costs and deficit of flow pressure and velocity in the network. The reduction in construction costs is accomplished by minimizing the diameter of network pipes which leads to the pressure drop in the network. Supplying proper pressure in nodes is one of the important design principles, and low pressure will not provide a complete water supply at the consumption site. Therefore, in this research, the problem of optimization in several sample networks was defined with the objectives of cost minimization and minimization of pressure deficit in the whole network. The EPANET software was used for hydraulic analysis of sample networks, and the multi-objective optimization process was performed by coding NSGA-II and MOPSO algorithms in the MATLAB software environment and linking them to EPANET. The cost function was initially defined only by considering the relationship between cost and diameter and the length of pipes, and in the next definition, the cost resulted by violation of the allowable pressure range was added to this function In both cases, the schedule for achieving the optimal answer was executed. The results showed that these algorithms have a high ability to find optimal solutions and are able to optimize the network in terms of cost and pressure by finding the appropriate pipe diameter. The time for reaching convergence was reduced by considering the cost of violation of the allowable pressure limits significantly and the optimal answer is obtained in a small number of repetitions. In NSGA-II and MOPSO algorithms in two-looped network with 20 and 30 iterations and run time of 0.66 and 0.8 s, respectively, and in Lansey network with 150 and 250 iterations and run time of 5.7 and 9.5 s, the optimal solutions were obtained.

Fault section location in urban distribution network based on fault marking

The goal is to propose an effective method for locating a fault segment in urban power distribution networks. Urban distribution networks have multiple outgoing lines, switches with multiple connections and have variable topology characteristics. It is found that the fault location method based on matrix algorithm has low adaptive capability and fault tolerance when dealing with complex and variable topology. Therefore, this paper proposes an efficient fault segment location method based on special fault indicators, which can significantly improve the accuracy and reliability of fault location. Accordingly, to improve the accuracy and reliability of fault location, a fault segment location method based on fault marking is proposed. The approach proposed in the paper relies on the analysis of the incident matrix, which describes the relationship between nodes and branches, and allows the use of graph theory. The branch state vector is added to obtain the adjacency matrix, which allows to describe the state of change in the dynamics of the distribution network topology. In the next step, a set of nodes and branches, which reflect the incoming and outgoing interconnections of the nodes, is established based on the selected direction of the network binding. According to the direction of the node fault current, the suspicious branches are identified and labeled to indicate the fault. By cumulative calculation and analysis of the labels, the target branches are screened out and the faulty sections of the city power supply network are identified. The results of the case study conducted in the paper show that the proposed method has good adaptability to the variable topology and increases the fault tolerance and accuracy of the developed matrix algorithm. The topological operating state of the network can be changed by controlling the switches to optimize the operation and improve the reliability of the power supply. Thus, the algorithm for fast and accurate fault location is of great importance for improving the safety and quality of urban power supply.

Analysis of Fault Characteristics of Distribution Network with PST Loop Closing Device under Small Current Grounding System

With the rapid development of cities and the increasing complexity of distribution network systems, the cableization of transmission lines and the diversification of power users have brought new challenges to the supply reliability of distribution networks. Short-time outages caused by power outages and maintenance are one of the factors that affect the reliability of the power supply in the distribution network. The non-stop load transfer through a phase-shifting transformer (PST) operation can effectively improve the reliability of power supply to complex distribution systems. Considering the operation mode and structure form and fault type of the urban distribution network in China, comparing and analyzing the applicable scenarios of different neutral grounding methods, and based on the structure and zero sequence path characteristics of PST, an improved PST-based phase shifting and grounding transformer loop closing device with low power consumption is proposed. The fault characteristics of the PST-based loop closing device under the small current grounding system are also analyzed by the sequence component method, and, finally, the effectiveness of the phase-shifting and grounding transformer device is verified by simulation under PSCAD/EMTDC for fault routing and protection configuration of the urban distribution network in China.

Soft open points based load restoration for the urban integrated energy system under extreme weather events

With frequent occurrences of extreme natural disasters such as typhoons in urban integrated energy systems (UIES), it is of great significance to cope with different kinds of disturbances. This paper proposes a load restoration method under typhoon weather for urban distribution and natural gas networks based on soft open points (SOP). Firstly, the typhoon wind speed model is introduced and the line fault rates of distribution networks under typhoons are calculated. Secondly, the gas turbine and electric-driven compressor are considered as the coupling units of the integrated electric–gas energy system, and related models are constructed. The fault analysis method of the natural gas network is proposed considering the faults in the distribution network lead by typhoons. Thirdly, SOP installed in the distribution network with the V/f control mode is applied to restore electrical loads and provide voltage support for the loads on the fault side. After that, the loads of the gas network could also be restored because of the restoration of the coupling units. Optimal energy flow is applied to determine the output of the power and gas sources, coupling units and also the loads to be restored. Finally, the fault rate of each line under typhoon disaster is analysed and the correctness and effectiveness of the resilience improving method based on SOP are verified with test systems UIES E33-G14 and UIES E123-G48.

Hierarchical frequency control strategy of doubly-fed induction diesel generator under emergency condition

Natural disasters lead to the uncertain topological structure of the urban distribution network. It is difficult for the communication system to recover quickly, which brings great difficulties to restoring the power supply. Therefore, the deployment of an emergency power supply is one of the critical measures to ensure the stable operation of isolated network systems and reduce power loss. Compared with the traditional synchronous diesel generator (SDG) as an emergency power supply, a doubly-fed induction diesel generator (DFIDG) has the advantages of flexible and controllable, rapid response and high operation efficiency. This paper presents a layered frequency control strategy for a doubly-fed induction diesel generator in an emergency scenario. Firstly, the models of doubly-fed induction diesel generator and its control system, prime mover and its speed regulation system are established. Secondly, the hierarchical frequency control strategy is proposed, including primary integrated frequency control (including droop control and virtual inertia control) and secondary frequency regulation control based on translation method. The virtual inertia control can make the doubly-fed machine quickly release the rotor kinetic energy when the frequency changes rapidly, so as to improve the frequency supportability. According to the overall shortage of the system and the maximum output power of the doubly-fed induction diesel generator, the strategy calculates the secondary frequency regulation power adjustment as the DFIDG power setting value, and then can realize automatic secondary frequency regulation without a communication system. Finally, simulation results verify the effectiveness of the proposed strategy.

Coordinated Operation of Hydrogen-Integrated Urban Transportation and Power Distribution Networks Considering Fuel Cell Electric Vehicles

Under the pressure of climate change, hydrogen has been advocated as a promising energy carrier to achieve low-carbon integration of urban transportation network (UTN) and power distribution network (PDN). In this article, the control strategy based on hydrogen refueling service fee (HRSF) is proposed for the smart city department to guide hydrogen fuel cell electric vehicles (HFCEVs) in selecting the hydrogen refueling stations. Correspondingly, the HRSF-based coordinated operation model is established to minimize the total of UTN travel cost, PDN operation cost, and the environmental cost, while the nodal carbon intensity restriction, the uncertainties of renewable distributed generators output, and origin-destination traffic demand are also taken into account. Afterward, the proposed model is solved by the decentralized alternative direction method of multipliers algorithm, and verified on the hydrogen-integrated UTN and PDN in Sioux Falls. Numerical results demonstrate that popularizing HFCEVs contributes to emission reduction, and the HRSF-based coordinated operation strategy is effective in reducing the overall emissions, promoting renewable energy accommodation, and improving the holistic operation efficiency of the hydrogen-integrated UTN and PDN.

Research on Urban Distribution Optimization Under Point-based Billing on Simulated Annealing with Variable Neighborhood

In this paper, we study the optimization of urban distribution networks with leased third-party logistics fleets under point-based billing and construct a mathematical model of multi-model vehicle path optimization (MVRPTW) with time windows aiming at the lowest logistics expenditure under point-based billing mode. For the problem that the simulated annealing solution to the VRPTW problem tends to fall into slow convergence, a variable neighborhood structure and adaptive temperature control are introduced to improve the simulated annealing. Finally, using the order data of a Beijing’s third-party logistics company Z, the model is solved by first clustering the customer nodes through the K-Means algorithm to generate the initial solution and then optimizing it with the improved simulated annealing algorithm. Compared with the simulated manual empirical scheduling, algorithmic scheduling can reduce the logistics cost by 88.1%.

Research on Application of Intelligent Technology in Urban Gas Transmission and Distribution Network System

Research on Application of Intelligent Technology in Urban Gas Transmission and Distribution Network System

Power Flow Analysis in Urban Distribution Networks with Implementation of Grid-Connected Photovoltaic Systems

In the last few years, renewable energies became more socially and economically relevant, and among them, photovoltaic systems stand out. Residential self-consumption of electricity is a field with great potential, and implementation of grid-connected photovoltaic systems (GCPS) is in full rise. The installation of distributed generation systems in residential environments could alter the performance of low-voltage distribution networks, since these are designed for unidirectional power flow and adding these generators means fluctuations in power-flows. For these reasons, a study of the fundamental magnitudes of three low-voltage distribution networks located in Madrid was made for various photovoltaic penetration rates, making use of simulations via the software OpenDSS and subsequent analysis of results. The research concludes that, among other aspects, GCPS produce load flow variations that are dependent on: the penetration rates; the distance from the point of interest and the distribution transformer, increasing the voltage variation between the most productive hours and the night hours with that distance; and on the rate between consumption and generation, so that when it diminishes, the self-sufficiency of the system increases, and with it the voltage of all the buses that tend to the rated voltage. Moreover, there are wide seasonal fluctuations: specifically, in summer months, generation profiles override consumption fluctuations, while in winter months consumption guides voltage and power profiles. Both the code implemented and the results of the analysis were published in an open source website using a free software license.

A multi-product multi-layer urban freight distribution problem solved using a hybrid metaheuristic procedure

The pick-up and delivery routing problem has received special attention thanks to its application to urban freight distribution processes. However, due to the multiple levels involved in those processes, modeling and analyzing urban distribution networks in urban contexts are complex tasks. As a result, efficient and robust solution methods should be proposed according to the dynamic and uncertain conditions that characterize this type of problems. This article presents a new formulation for the pick-up and delivery problem in a logistics distribution network composed of 3 levels: n: 1: m (n suppliers, 1 urban consolidation center, and m customers). In addition, an algorithm based on GRASP heuristic and 2-opt algorithm was implemented here to find solutions to problem, which were compared with the results of the same algorithm for a two-layer vehicle routing problem in several instances. Thus, the proposed procedure achieved a 22% improvement over such algorithm.

Research on Fire Prediction Method of High-Voltage Power Cable Tunnel Based on Abnormal Characteristic Quantity Monitoring

The proportion of cable lines in the urban distribution network is increasing. The fire hazard of important cable channels is prominent, which has a serious effect on the safety and stable operation of the power system. In recent years, intelligent mobile inspection and fire extinguishing devices have been applied in tunnels. The determination of firepower and location is conducive to the rapid and effective fire suppression of intelligent devices. Therefore, this study proposes a fire early warning method of a high-voltage power cable tunnel based on abnormal characteristic quantity monitoring. Based on the modified model of complex pyrolysis and combustion chemical reaction, the fire development of different fire source powers and fire locations is simulated. The temperature distribution and characteristic gas concentration under different simulation conditions are analyzed. The results show that the monitoring data of temperature, flue gas concentration, and CO and CO2 concentration need comprehensive analysis to effectively reflect different fire conditions. The characteristic data set is selected and processed to form a total sample. The fire prediction model is trained and tested. The accuracy of the proposed prediction model is 92%.

Modeling the Mixing Phenomenon in Water Distribution Networks: A State-of-the-Art Review

This paper presents a state-of-the-art review of modeling the mixing phenomenon of junctions in water distribution systems (WDSs). Firstly, the basic concepts and governing equations of the mixing phenomenon are presented. The complete mixing simplifying assumption used in the existing tools of WDSs modeling and management (EPANET, WaterCAD) is described. The paper goes on to show that the complete mixing simplifying assumption can lead to erroneous results. Then, the most frequent incomplete mixing models are described, including AZRED, EPANET-BAM, EPANET-BAM-WRAP, and two analytical models. Also, a summary of all the existing mixing models is provided, trying to determine which mixing model is better to use for a specific urban water distribution network. Because this question can only be partially answered, the paper ends by proposing potential future developments in modeling the mixing in junctions: taking into account the effect of the chemical reaction on the mixing phenomenon in junctions, and considering real-world pipe sizes and pressure to study the mixing phenomenon.

A sustainable redesign model for the water/wastewater supply network: a water–energy nexus approach

PurposeA sustainable selection method for facility location of the water treatment is formulated by best–worst method. In addition, the model addresses the selection of appropriate technologies in the treatment plant, management of water leakage in the whole transmission network by using modernization and selection of different transmission technologies. Finally, the interaction between water and energy in this network seems to be paying particular attention.Design/methodology/approachRapid population growth and urban development, and the constraints of water supply have become one of the crucial challenges around the world in the 21st century. Hence, the use of refined urban wastewater is increasing in many countries as an alternative source of water. In this regard, the rehabilitation of urban wastewater recycling and reuse has been proposed as one of the most suitable solutions for urban water management. Hence, in this paper, a mathematical model is formulated to design the simultaneous marketing of the urban water distribution network and wastewater treatment (including).FindingsIt seeks to ensure that energy is supplied through chemical methods to ensure that the system's energy dependence is on the national electricity grid. And in order to validate the model, a case study has been studied. By analyzing the results, it can be concluded that the upgrading of sewage treatment plants to replace underground water and water from nearby dams in household, agricultural and industrial applications will have positive environmental and economic impacts. One of the notable environmental impacts is the decline in groundwater and water scarcity in the coming years.Originality/valueThe summary of contributions is presented follow as: design and planning of water and urban wastewater integrated network; sustainable selection of facility location for the water treatment; capability selecting different treatment technologies in simultaneous design water and urban sewage supply chain; managing water leak in the network; proposed a water–energy nexus model in simultaneous design water and urban sewage supply chain; studying the feasibility of construction of power plants from biogas, the resulting of anaerobic digestion in treatment centers.

МОДЕЛИРОВАНИЕ ПЕРЕХОДНОГО ПРОЦЕССА В РАСПРЕДЕЛИТЕЛЬНОЙ СЕТИ 10 КВ ПРИ ОДНОФАЗНОМ ЗАМЫКАНИИ НА ЗЕМЛЮ

Relevance At the moment, finding single-phase earth faults in networks with isolated and compensated neutral is still a problem with ambiguous solutions. Existing earth fault protection devices are relevant only in special cases. In networks with a large number of outgoing connections and an extensive circuit, these protections are not able to provide absolutely selective triggering. Therefore, this problem is especially relevant for urban electric networks, since these networks are characterized by both the mass of lines and the heterogeneous nature of the load. Also, the difficulty in detecting damage is the secrecy of the transmission lines, since in these networks they are mainly made by cables. To unambiguously determine the earth fault, in urban distribution networks, earth fault protection is most often used in conjunction with the sequential shutdown method. The use of this method greatly facilitates the determination of an earth fault, but at the same time it is destructive in relation to the power supply of consumers. Since urban distribution networks supply densely populated areas with electric energy, this disadvantage further exacerbates the existing problem. In order to limit these negative consequences, it is possible to make switches by regrouping the network into sections. Such switching will allow you to quickly identify a damaged line and eliminate short-term disconnections of consumers during the search for a ground fault. However, the application of this method is accompanied by switching in the distribution network during a single-phase earth fault. Therefore, it is necessary to study the transient process that occurs during such switching in 10 kV distribution networks in order to verify the applicability of such switching. Also, this study will set the vector for further scientific research in this area. Aim of research Simulation of the transient process that occurs when combining 10 kV networks for parallel operation during a single-phase earth fault. Research methods The methodological basis in this article is mathematical simulation modeling. Results Overvoltages arising during switching in a 10 kV network during a ground fault are considered. Their analysis and the conditions of applicability of the switches performed when determining the earth fault in distribution cable networks are carried out.

Multi-objective Dynamic Reconfiguration for Urban Distribution Network Considering Multi-level Switching Modes

The increasing integration of photovoltaic generators (PVGs) and the uneven economic development in different regions may cause the unbalanced spatial-temporal distribution of load demands in an urban distribution network (UDN). This may lead to undesired consequences, including PVG curtailment, load shedding, and equipment inefficiency, etc. Global dynamic reconfiguration provides a promising method to solve those challenges. However, the power flow transfer capabilities for different kinds of switches are diverse, and the willingness of distribution system operators (DSOs) to select them is also different. In this paper, we formulate a multi-objective dynamic reconfiguration optimization model suitable for multi-level switching modes to minimize the operation cost, load imbalance, and the PVG curtailment. The multi-level switching includes feeder-level switching, transformer-level switching, and substation-level switching. A novel load balancing index is devised to quantify the global load balancing degree at different levels. Then, a stochastic programming model based on selected scenarios is established to address the uncertainties of PVGs and loads. Afterward, the fuzzy c-means (FCMs) clustering is applied to divide the time periods of reconfiguration. Further-more, the modified binary particle swarm optimization (BPSO) and Cplex solver are combined to solve the proposed mixed-in-teger second-order cone programming (MISOCP) model. Numerical results based on the 148-node and 297-node systems are obtained to validate the effectiveness of the proposed method.

Bi-Level Decentralized Optimal Economic Dispatch for Urban Regional Integrated Energy System Under Carbon Emission Constraints

Based on the real-time environmental constraints in urban regional construction, this paper constructed a bi-level decentralized low-carbon optimal dispatching model of the urban regional integrated energy system (RIES), including the park integrated energy systems (IESs). In this model, a bi-level optimal allocation model of carbon emission constraints between the urban and the park is proposed for the first time. The upper urban will formulate the real-time carbon emission constraints based on real-time environmental monitoring, decomposing the historical carbon emissions to the lower park IESs; the lower park will meet the real-time carbon emission constraints during optimization. We through the upper urban with the lower park between the bi-level decentralized optimization to ensure that the objective function’s upper urban power, natural gas, and heat distribution network system is minimum total network loss. In addition, it is necessary to ensure the minimum operating cost of each park IESs and focus on how to meet the requirements of the overall environment of urban RIES. Furthermore, we study the influence of optimal allocation strategy of carbon emission constraints on network loss, and operating cost of urban RIES under different scenarios. Then, an improved analytical target cascading (ATC) method is applied to solve the bi-level decentralized optimal dispatching model of urban RIES. Finally, an example under three different scenarios is given to verify the superiority and effectiveness of the proposed model and the improved method.