Index system and methods for urban power grid operation risk assessment

With the rapid growth of urban power transmission cable scale, the harmonic pollution in the high-voltage power grid is more transmitted to other power grids of different voltage levels, which makes the harmonic transmission more complicated, increases the harmonic emission level, and makes it difficult to quantitatively analyze and study the allowable value of users’ electrical pollution emission. Therefore, in this paper, by establishing the harmonic conduction model of the urban high-voltage power grid and considering the equivalent circuit of transformer and transmission cable in the urban power grid, the parameters of transmission cable harmonic transfer coefficient and the allowable emission value of power quality pollution of the urban power grid are deduced and quantitatively analyzed. Then the harmonic transmission and mutual influence of urban power network harmonics in power transmission cable are analyzed through examples, which is helpful to determine the allowable value of harmonic pollution emission scientifically and reasonably.

Shanghai is one of China's highest levels of industrialization and most economically developed regions. In the backdrop of the development of smart grid, smart electric power industry will be to play a very important position in the Shanghai urban area's electric power industry. This paper will focus on the analysis of the present situation of Shanghai urban area's power grid, especially the basic skills and business models of the power demand side. It is researched that the blueprint of the Shanghai urban area's future power grid and achieving methods based on the related smart electricity work carried on in the current Shanghai urban area and its effectiveness, especially, the pilot project. The main work is as follows: the description of the current Shanghai urban area power grid, including the history, development and evolution, load characteristics level, reliability, power distribution automation level and so on. The presented situation of smart power, which mainly includes the information collection system pilot project, electric vehicle charging facilities pilot project, intelligent building pilot project, flexible DC power transmission pilot project, the power FTTH (Fiber to The Home) to households pilot project, especially combine with the smart grid key pilot projects, such as the smart power design and practice of Shanghai World Expo smart grid pilot projects, and point out the current shortage and inadequate of the smart grid. The blueprint and achieving methods of the smart electricity describes the design blueprint of the future smart electricity in Shanghai urban area, and the means and direction to realize, such as to adapt and promote clean energy development, realizing highly smart grid dispatching to meet the electric vehicle and other new electricity consumers of electricity service requirements, efficient use and life cycle management of grid assets, convenient interaction between power users and grid, grid management informationalization and delicacy and playing the role of value-added services potential of the grid infrastructure.

Urban grid planning needs to focus on sound investment plans to improve the safety and reliability of power system power supply to meet the growing needs of users. Does not adversely affect the environment. The contradiction in urban power grid and urban planning is an important reason that plagues the rapid development of power grid enterprises. Therefore, under the trend of urbanized dogs, urban power grid construction planning and urban overall planning are required to match. Urban planning needs to consider urban power grid planning as an important component, and match urban development to achieve simultaneous development. The integrated management and distribution system is the platform that contains all the information processing. It can share information and improve the reliability and security of the grid operation. This paper first introduces the integrated system of urban problems and its concept and architecture, focusing on the overall design form and process information management model, system function structure and several aspects of the main functions of the integrated system.

Modern power grid has a fundamental role in the operation of smart cities. However, high impact low probability extreme events bring severe challenges to the security of urban power grid. With an increasing focus on these threats, the resilience of urban power grid has become a prior topic for a modern smart city. A resilient power grid can resist, adapt to, and timely recover from disruptions. It has four characteristics, namely anticipation, absorption, adaptation, and recovery. This paper aims to systematically investigate the development of resilient power grid for smart city. Firstly, this paper makes a review on the high impact low probability extreme events categories that influence power grid, which can be divided into extreme weather and natural disaster, human-made malicious attacks, and social crisis. Then, resilience evaluation frameworks and quantification metrics are discussed. In addition, various existing resilience enhancement strategies, which are based on microgrids, active distribution networks, integrated and multi energy systems, distributed energy resources and flexible resources, cyber-physical systems, and some resilience enhancement methods, including probabilistic forecasting and analysis, artificial intelligence driven methods, and other cutting-edge technologies are summarized. Finally, this paper presents some further possible directions and developments for urban power grid resilience research, which focus on power-electronized urban distribution network, flexible distributed resource aggregation, cyber-physical-social systems, multi-energy systems, intelligent electrical transportation and artificial intelligence and Big Data technology.

Large-scale urban power grid is facing increasingly serious trend of heavy load problem. The cost of traditional solutions is usually high due to large investment and difficult implementation of urban construction. In this literature, the application of three types of power electronic technology in solving unbalanced power flow of urban power grid is considered. The technical theory of UPFC is analyzed for entry point. By comparing with flexible DC technology and SSSC which are of the same type with UPFC, the application scenarios of three types of power electronic devices are demonstrated and the feasibility of UPFC above flexible DC technology and SSSC in urban power grid are proposed. Then an actual problem of a real urban power grid and several solutions including UFPC are studied and compared, which shows the application potential of UPFC in project perspective.

This paper puts forward the planning and configuration principle of the battery energy storage station(BESS) of the urban secure power grid, and establishes the full-life cycle economic model of the BESS based on the configuration requirements in urban secure power grid for the emergency power supply. Taking the maximum annual equivalent income as the objective function, an economic allocation model of the capacity of BESS for urban secure power grid based on improved particle swarm optimization algorithm(IPSO) was established to achieve the economic optimization of the capacity arrangement of energy storage power station while meeting the important load holding of the city under the disaster scenario of reliable support. At the same time, a reliability analysis model for energy storage capacity configuration results considering the impact of disasters is established to support the reasonable selection. Finally, the scheme comparison and optimization design are carried out based on the actual scenario of an urban secure power grid.

External tie line power fluctuations smoothing strategy of new urban power grid

Towards the dual-carbon goals, the new urban power grid (NUPG) dominated by new energy has a low proportion of adjustable power generation units, resulting in insufficient scheduling flexibility. As a result, it becomes challenging to cope with the complex operating conditions of the NUPG. In this paper, after analyzing the new operational characteristics and challenges of the NUPG, a flexible load dispatching architecture and key technologies for the NUPG are proposed. These enhance the scheduling flexibility of the NUPG from the load side, which further provides support for the operation of the large power grid. Then, the types of scheduling objects, scheduling methods, scheduling tasks, and four essential dispatching technologies are introduced to provide a reference for building the NUPG flexible load dispatching system. Finally, the effectiveness of the NUPG flexible dispatching architecture and technologies is verified by simulation analysis of the IEEE39-bus system and the actual power grid in East China.

Power grids of large or mega cities are continuously upgrading to meet the growing demand for power and replace old-style local generation with power supplies from external cleaner sources. Advanced transmission technologies can effectively increase the delivery capacity, flexibility and utilization of existing infrastructure. The focus of this paper is on VSC-HVDC subtransmission technologies for urban power grid enhancement and modernization. The discussions include urban power grid expansion issues, VSC-HVDC application scenarios, advanced technical schemes of VSC-HVDC intertie in subtransmission network, and control features for grid support under emergency conditions.

Urban power grids are facing many operational and expansion challenges to meet further demand growth and increased reliability requirements. Advanced transmission technologies have been considered by the electric utilities to effectively increase the utilization of existing infrastructure and operational flexibility. The focus of this paper is on VSC-HVDC technologies for urban power grid enhancement and modernization. First, a potential technical scheme is proposed for converting an existing AC circuit to DC operation, which could boost the power transfer capability of the critical transmission corridor and increase network operational flexibility. Second, this paper proposes three operation modes for the VSC-HVDC interties in urban power grids corresponding to normal, emergency and island operating conditions, respectively. An integrated, adaptive emergency control strategy (AEC) is proposed that can enable adaptive power flow responses of the VSC-HVDC intertie under varying system operating conditions and critical contingencies. The flexibility and effectiveness of the proposed operational principles of urban VSC-HVDC intertie and the corresponding control strategies are verified in PSCAD/EMTDC using a realistic urban power grid in China.

The rapid development of urban rail transit has led to a large amount of stray current invading the urban power grid, causing DC bias in transformers, which in turn leads to problems such as vibration, noise, and heating, seriously affecting the stability and reliability of power grid operation. This paper provides experimental and simulation analysis methods for the DC bias problem of transformers caused by stray current in rail transit, offering theoretical basis and technical support for subsequent engineering applications and safety monitoring. Through in-depth analysis of the relationship between stray current, vibration, and noise, this paper provides important reference value for evaluating and mitigating the impact of stray current on the urban power grid.

Carbon emissions of urban power grid in Jing-Jin-Ji region: Characteristics and influential factors

Development of a Risk Assessment Index System of Non-Specific Neck-Shoulder Pain in Physicians and Nurses: A Delphi and Analytic Hierarchy Process Study in China.

Single phase grounding fault is the most common fault in distribution system. It mostly occurs in wet and rainy weather, which is caused by many factors, such as tree barrier, single-phase breakdown of distribution line insulator, single-phase disconnection, small animal harm and so on. Single phase grounding not only affects the normal power supply of users, but also may produce overvoltage, burn equipment, and even cause phase to phase short circuit, expanding the scope of accidents. The 10-35kV lines in China’s urban power grid are mainly neutral non effective grounding systems. After the occurrence of single-phase grounding fault, the fault characteristic signal is weak and difficult to extract, resulting in the difficulty of accurate fault diagnosis. However, due to the limitations of the traditional fault diagnosis principle relying on the zero sequence voltage and current criterion, there are serious misjudgments and omissions in the single-phase grounding fault diagnosis of distribution network. With the rapid development of distribution network in recent years, the functions of wave recording and event playback of distribution automation system and its equipment can collect online power grid operation information before and after. After the accident, a sample database of accident cases shall be formed. How to use these data to improve the

With the continuous development of power grids, power cables are widely used in urban power grids. But cables are generally laid underground, and the fault is not easy to be found and the recovery time is long, the reliability of power supply was seriously threatened. The traditional planned maintenance has not been able to solve the existing problems accurately. Therefore, it is of great significance to improve the reliability of power distribution and reduce the failure rate by assessing the operational status of power cables through the relevance analysis of massive monitoring and testing data. This paper proposes a power cable state assessment algorithm based on association rule data mining technology from the perspective of big data and information relevance. Firstly, by analyzing the online monitoring data, detection data, experimental data, and the interrelation of the state parameters of the cable and transformer fault types, the set of cable synthetic status parameters can be set up. Then, use the association rule method to calculate the weight coefficient of each state parameters; In order to effectively avoid the influence of subjective factors on the evaluation results, weighted theory of equilibrium function was used to calculate the weight coefficient of the synthetic status parameters; Finally, combined with the existing assessment process, an accurate and objective evaluation system power cable was established. The results of the example verify the validity and accuracy of the assessment method, which provides a new novel idea for cable status assessment.