Urban Power Supply System Research Articles

Универсальная централизованная защита от однофазных замыканий на землю в кабельных сетях напряжением 6–10 кВ

Selective protection against single phase earth faults in distribution 6–10 kV cable networks can be performed both with the use of individual (per connection) and centralized devices covering all connections of the protected object. The advantages of centralized devices are reduction of specific (per connection) costs of protection, simplification of its operation and design. Well-known technical solutions in terms of centralized protection devices against this type of damage do not always provide versatility (the possibility to use neutral cables of 6–10 kV in various grounding modes) and high technical perfection (selectivity and stability of operation). Thus, it is relevant to develop a universal centralized protection against single-phase earth faults, ensuring high technical perfection for all types of earth faults in 6–10 kV cable networks with different neutral grounding modes. The authors have used a comprehensive simulation model "cable network – protection device" to study the selectivity and stability of the developed principles of implementation and algorithms for centralized protection against earth faults. The model is designed in SimPowerSystems and Simulink software. The configuration and parameters of the cable network model have been selected considering the key features of 6–10 kV distribution cable networks of industrial and urban power supply systems. A universal centralized protection against all types of earth faults in 6–10 kV cable networks with various neutral grounding modes has been developed. The results of functional tests on the simulation model have confirmed the effectiveness of the developed algorithms of the developed centralized protection for all types of earth faults both in uncompensated and compensated cable networks of 6–10 kV. The proposed technical solution implements a multifunctional multiparametric centralized protection against earth faults. It has such properties as versatility, selectivity, and high stability of operation for all types of earth faults, recognition of types of single-phase earth faults, continuity of action in stable and most dangerous arc intermittent earth faults.

An online energy optimization method for urban rail flexible traction power supply system based on spatiotemporal matching of train power

An online energy optimization method for urban rail flexible traction power supply system based on spatiotemporal matching of train power

A Power Flow Dynamic Deduction Method for Urban Rail Traction Power Supply System Considering the Fluctuation of Train Passenger Load

A Power Flow Dynamic Deduction Method for Urban Rail Traction Power Supply System Considering the Fluctuation of Train Passenger Load

ОБРАТИМЫЙ ПРЕОБРАЗОВАТЕЛЬ ЭНЕРГИИ С МАХОВИЧНЫМ НАКОПИТЕЛЕМ В СИСТЕМАХ ЭЛЕКТРОСНАБЖЕНИЯ

The problem of voltage unbalance and the need to power factor correction remain a relevant objective for electric power engineering. A variable load profile reduces the operating efficiency of electric power plants and leads to an overestimation of the power of transformer substations and the wire size of supply lines. Thus residential buildings power equipment remains underloaded for a significant part of the time. The decrease of power-frequency characteristic is becoming increasingly noticeable. This situation is not a problem yet, but in the future it may complicate the task of frequency stabilization. Finding solutions to existing and predicted problems is an important topic of research. To solve the problems posed, the work proposes the concept of a reversible energy converter, that is an electrotechnical complex with a flywheel energy storage and a two-section frequency converter based on two reversible voltage converters (active front end). The planning area of application of a reversible energy converter is transformer substations of residential and public buildings of urban power supply systems. The reversible energy converter is designed to solve such problems as load leveling, reactive power compensation (power factor correction), balancing voltages and power-frequency characteristic control. The work presents a connection scheme a reversible energy converter to the supply system and provides an expression for the phase load voltage.

Multi time scale management and coordination strategy for stationary super capacitor energy storage in urban rail transit power supply system

The application of stationary super capacitor energy storage systems (SCESS) is an effective way to recover the regenerative braking energy of urban rail transit vehicles. The benefits of these systems’ application largely depend on the design of the energy management strategy (EMS). In this paper, the EMS core demand of SCESS is analyzed and divided into different levels based on the considered time scale. On this basis, control objectives and mathematical models were analyzed considering different time scales. Then, an EMS based on a genetic and fuzzy algorithm was presented. The feasibility and effectiveness of the proposed EMS were verified through the simulation of actual line parameters. The results indicated that the EMS can satisfy the control requirements of multiple time scales of SCESS. It is capable of effectively achieving energy management and coordinated control of multiple SCESS. As a result, it also for energy savings in the urban rail transit power supply system.

Hierarchical Operation Optimization for Regenerative Braking Energy Utilizing in Urban Rail Traction Power Supply System

The energy feedback system (EFS) is widely accepted to utilize the regenerative braking energy (RBE) in an urban rail traction power supply system (TPSS). However, the sharing relationship of RBE between EFS, traction trains and on-board braking resistors is not clear. In addition, the impact of EFS operation on the sharing of RBE has been rarely studied. This paper proposed a hierarchical operation optimization method for improving the utilization of shared RBE in TPSS through the EFS. An optimizing model for the dynamic start-up voltage threshold of EFS is established, with the objective of minimizing TPSS power consumption. A fast prediction model of train operation information is developed to analyze the steady-state power flow in advance. The optimal solution is searched using a salp swarm algorithm (SSA) on a per second basis. A microsystem of three traction stations and two trains is analyzed. Compared to the conventional constant voltage operation scheme, the optimal solution achieves a maximum additional energy-saving efficiency improvement of 2.44%. Efficient sharing of RBE is identified as the key to achieving energy savings. Regarding the local control part, system stability analysis is verified. Real-time simulation results indicate that the dynamic operating mode of EFS efficiently distributes RBE.

A Real-Time Adaptive Energy Optimization Method for Urban Rail Flexible Traction Power Supply System

In urban rail traction power supply systems, the optimal power flow method is mostly utilized for energy optimization. Conventional power flow optimization adopts offline calculation methods to obtain the optimal strategy under given scenarios. However, this method cannot continuously realize the ideal optimization effect for the time-varying flexible traction power supply system. For this reason, this paper proposes a real-time adaptive energy optimization method to solve the problem above. Firstly, the control objective of the optimal power flow is determined based on analyzing the system power flow. Secondly, a hierarchical control system is designed to achieve adaptive optimal control for the flexible traction power supply system. Moreover, a swarm intelligence optimization algorithm-based optimal power flow calculation method is employed to realize the real-time optimal power flow. Finally, some simulations are performed to verify the effectiveness and accuracy of the proposed real-time optimal power flow. It is demonstrated that the real-time optimal power flow method makes it possible to consider the low delay and high accuracy of control commands at the same time. Compared with the conventional offline method, the proposed real-time method can reduce the input electricity consumption by 1.47%, which is valuable in practical applications.

Research on the Control Strategy of Urban Integrated Energy Systems Containing the Fuel Cell

As a new type of energy with the advantages of high efficiency, clean and pollution-free, fuel cells have attracted the attention of many experts and scholars. The efficient utilization of fuel cells will certainly become the mainstay of energy transformation and environmental protection. However, fuel cells have low power density, soft electrical output characteristics, and significantly delayed response to sudden load changes. When fuel cells are used as power supply energy alone, the output voltage fluctuates greatly, and the power supply reliability could be higher. To increase the fuel cell’s service life in real world applications, a DC converter and an appropriate auxiliary energy storage power supply are combined to form a fuel cell hybrid power supply system that makes efficient use of the auxiliary energy storage system’s availability, enhances the power supply system’s adaptability through dynamic reconfiguration, and provides better flexibility overall. This work proposes a method for managing the energy produced by an urban integrated power supply system that includes fuel cells, supercapacitors, and solar cells. Applying the IF-THEN rule of load power and the state of charge of the supercapacitors, the power balance is adjusted between the su-percapacitors, photovoltaic cells, and fuel cells according to the defined fuzzy logic control. The intermittent nature of solar power production and the erratic nature of fuel cell output may both be mitigated using this technique, allowing the load power to operate more reliably. The simulation results show that the control strategy adopted in this paper is able to not only meet the load requirements but also reasonably allocate the functional requirements and improve the working efficiency of the system, resulting in a clear optimization effect on the system’s control. In this paper, we focus on the fuel cell hybrid power supply system design, and then we use the idea of fuzzy logic control energy management to build the structure of the fuzzy logic control system, design the fuzzy controller, determine the functions, and verify the solutions through simulation and experimentation.

Development of the theory of complexly closed city electrical networks

The article discusses the issues of optimization and selection of the most rational scheme of a complex electrical network for the power supply of a microdistrict. And this requires the development of a more accurate definition of the calculated electrical loads of consumers, as well as the total loads of TP, RP, GRP, standard daily schedules, specific standards for calculating electrical loads, new building codes and regulations to replace the old KMK 2.04.17-98, determination of the most advantageous power and number of transformer substations, calculation of systems of complex power supply circuits using various methods, new technologies and digital automatic relay protection of urban power supply systems, use of reverse power automatic machines, contactless elements in power supply systems.

Reactive power compensation for sustainable development of power grids in cities of Uzbekistan

The article deals with relevant and much needed at this stage problems of reconstruction and modernization of urban power supply systems and issues of energy saving in urban power grids. For the first time, it is proposed to carry out energy saving in the residential and public sectors of the residential zone of cities on the basis of reactive power compensation. There are given an analysis of experimental studies and measurements of power consumption and based on them recommendations and ways of energy saving in urban power grids.

Analysis of the Minimum Electrical Load of Residential Apartment Buildings in Urban Power Supply Systems

At present, a significant part of the studies of a residential apartment building electrical load concerns only the analysis of the maximum load at the residential building power supply input and on the buses of the transformer substation supplying power to residential buildings. However, for a complete analysis of the residential apartment building power consumption, it is necessary to evaluate not only the maximum input power, but also the minimum load. The article presents the results from an analysis of electricity consumption in residential apartment buildings with electric stoves (taking the city of Moscow as an example). The power consumption in eight residential apartment buildings recorded by electric meters in the input switchgears of these buildings at 30-min intervals for several years was used as input data for the analysis. The dynamics of minimum electrical load variation during a year is considered; the dependence of the minimum power on the outdoor temperature is estimated, and the time of the day, day of the week, and month in which the residential building minimum electrical load is observed are determined. The distribution law of a random variable represented by the time in which the absolute annual minimum of the residential building electrical load is observed and its characteristics: mathematical expectation and standard deviation are determined. The results of a comparative analysis of the absolute annual minimum and maximum (design) load at the input of residential apartment buildings are presented.

Design and Implementation of a vibration monitor protecting the cable from external destruction

Underground cable is one of the main components of urban power supply systems. However, it is often damaged by large machinery in the process of urban road construction. To protect the underground cable, this paper proposes a novel design of a smart vibration device based on a complex embedded system, including the STM32 control chip, vibration sensors, NB-IoT communication module, and charging module. Through vibration signal detection of the excavator and other large-scale mechanical behavior, the vibration device can indicate the direction where the damage is occurring, and send out a warning message to the operation center. Finally, some experiments for vibration monitoring devices are conducted to verify their effectiveness and future application potential prospects.

Intelligent Application and Exploration of Urban Rail Transit Power Supply System

Intelligent Application and Exploration of Urban Rail Transit Power Supply System

Modified AC/DC Unified Power Flow and Energy-Saving Evaluation for Urban Rail Power Supply System With Energy Feedback Systems

Energy feedback systems (EFSs) have been widely applied in urban rail transit, and a power flow algorithm and energy-saving evaluation of urban rail power supply systems with EFSs are studied in this paper. First, trains, the reflux system, and traction substations with EFSs are modeled, and the multimode transitions are analyzed, including the maximum power state of the EFS. Then, a modified AC/DC unified power flow algorithm for the DC power supply system, which simplified the DC reflux system is proposed, and a field case study based on a multiple train scenario is presented to validate the algorithm. Furthermore, system-level energy-saving evaluation indexes are applied according to system power flow analysis. When the headway time decreases, the proposed indexes decrease in general mainly as there is more regenerative braking energy absorbed by adjacent trains. The higher the load rates of the step-down substations are, the more daily feedback energy is utilized. When the start voltage of the EFS ranges from 1650 V to 1770 V, the maximum energy-saving rate reaches 11.9%, which occurs when the start voltage is 1670 V. When the no-load voltage is relatively high, the start voltage should not be higher than 1750 V to keep the system running in high efficiency. These results can provide advice for the design and operation of traction power supply systems with EFSs.

Актуализация нормативных значений удельной электрической нагрузки многоквартирных домов в Республике Татарстан

The Code of Practices SP256.1325800.2016 and regional standards for urban planning design are the main regulatory and technical documents regulating the design analysis of residential building electrical loads. The relevant standard values of specific electric power, which serve as the basis for designing urban power supply systems, have not been revised for more than 40 years. A study of 10/0.4 kV urban transformer substations in different regions of the Russian Federation has shown that 70 to 80% of transformers are loaded by less than 30% of their rated capacity during the year, and half of them operate with a maximum load of less than 15%. The actual daily profiles of apartment building electrical loads for the period 2016-2018 were studied, and data on power consumption were statistically processed. The results obtained allowed us to justify the possibility of reducing the design electrical load in designing apartment buildings and to develop new regional standards for specific design loads. The updated standard values of specific electrical loads are applicable to an apartment building as a whole and take into account both the electrical load of individual apartments and the general household electricity consumption. The economic efficiency of applying the new standard values in performing design calculation of electrical loads and selecting the electrical equipment is shown taking the Salavat Kupere residential complex as an example.

Analysis of the electric loads of residential and public buildings in urban power supply systems

Accurate determination of the calculated electric loads is a basis for power supply systems design. Values of the calculated loads influence parameters of the electrical grid. That is why the values of the calculated loads should not be exceeded in operation. Calculated electric loads also influence investments in the designed grid. For the most effective usage of the investments, the values of the calculated loads should not be overstated or understated. This article is about the applicability of the problem of the elaboration existing databases used in governing documents. Based on the obtained data, the analysis of the calculated electric loads of public buildings is carried out. Typical daily load graphs at the input of the apartment houses with electric stoves are given. Accurate load graphs at the input of the apartment houses are received, according to the results of measurements for various days of the week. The received load graphs are compared with given graphs from technical literature. We have found that the configuration of the up-dated load graphs of residential buildings significantly differs from the given graphs.

Analysis of the influence of the installation of a dishwashing machine on household energy sources consumption in urban power supply systems

The subject of the research is the interconnection between the installation of a dishwashing machine in a household and the change in consumption of such primary resources as electric energy, cold and hot water. Applicability of this research is defined by the high growth of various electric appliances in the households, and the dishwashing machine has one of the highest tempos of the increase over the last decade. The results of this research allow esteeming the future change in the structure of consumption of energy sources by the households in terms of mass implantation of dishwashing machines in our daily life. Several methods of estimation have been reviewed of how the installation of the dishwashing machine impacts on energy sources consumption in the household. Mathematical descriptions and the rationale for the statistical data analysis methods of household energy sources consumption, which were used are explained. Based on the analysis of statistical data over 5 years before the installation of the dishwashing machine, the consumption of the sources is forecasted for the sixth year upon condition that there is still no dishwasher. At the beginning of the sixth year, the dishwashing machine was installed in the observed household. Forecasted values of household sources consumption for the sixth year have been compared with actual values which were obtained after installation of the dishwasher in the household.

Overview of urban rail transit energy feedback traction power supply system

The power feedback traction power supply device is composed of rectifier unit and four - quadrant converter device. The four-quadrant converter device can work either in the rectifier state which can provide energy to the dc catenary or in the inverter state which can feed excess regenerative braking energy back to the ac power grid. At the same time, it can make reactive power compensation for ac medium voltage network and improve the power factor of the system. This paper mainly introduces the research technology of urban rail transit energy - fed traction power supply system.

Research on the Planning Strategy and Layout Pattern of Electricity Grids in Megacities from the Perspective of Urban Planning

In light of the advancement of urbanization and the development of digital and intelligent technologies, urban power consumption has shown a continuous and rapidly increasing trend, which makes power supply and its protection key issues in terms of further urban development. Given this context, the electric power system per se has likewise been undergoing continuous improvement and change, with many efforts directed toward AC-to-DC conversion for electricity transmission. As such, the new measures applied in urban areas inevitably face the challenge with regard to coexisting with the existing urban systems. On the one hand, electricity grids, as important infrastructure of urban power supply systems, play a key role in supporting modern urban life. On the other hand, the traditional planning methods, solely relying on electricity load forecasting and load nodes, results in a certain degree of inconsistency and conflict between the electricity grid planning and the Master Urban Plan, thereby leading to serious negative impacts of the electricity grid layout on urban space quality. Given this context, this article reflected on the limitations of the traditional electricity grid layout and planning methods by analyzing the current situation and the needs of urban space development. Subsequently, relevant planning theories were combined to explore strategies and models for the planning and layout of electricity grids and related facilities in megacities based on comprehensive consideration of power security, power safety, not-in-my-backyard mentality, urban development needs, and urban space quality, in order to achieve harmonious coexistence of electricity grid construction with urban-rural space.

Application of passive energy-saving technology for building planning in urban power supply system

Application of passive energy-saving technology for building planning in urban power supply system