Characteristics Of Power Grid Research Articles

Short-term hydro generation operation of cascade hydropower stations in Han River, China

Hydropower is a natural renewable energy with outstanding technological superiority in short-term operation. Short-term hydro generation operation (SHGO) requires not only lord dispatch in single station, but also the coordination of hydraulic and electric connection for different stations. In this paper, a coordinated peak shaving operation method of cascade hydropower stations is proposed. Firstly, regular pattern of peak load regulation is analyzed using the load characteristics of power grid. The daily power output of cascade hydropower stations should meet the needs of typical load pattern. In order to satisfy comprehensive utilizations of water resources, the outflow of each reservoir should be no less than the demand of water supply or irrigation. To verify the feasibility and effectiveness of the proposed method, an application of Pankou and Xiaoxuan cascade hydropower stations, located in Hanjiang River in China, is presented in this paper. Simulation results indicate that the proposed method can obtain the maximum peak shaving amplitudes and suggested peak shaving amplitudes at the same time, which satisfies different operation demands of cascade hydropower stations.

Study on power grid characteristics in summer based on Linear regression analysis

The correlation analysis of power load and temperature is the precondition and foundation for accurate load prediction, and a great deal of research has been made. This paper constructed the linear correlation model between temperature and power load, then the correlation of fault maintenance work orders with the power load is researched. Data details of Jiangxi province in 2017 summer such as temperature, power load, fault maintenance work orders were adopted in this paper to develop data analysis and mining. Linear regression models established in this paper will promote electricity load growth forecast, fault repair work order review, distribution network operation weakness analysis and other work to further deepen the refinement.

Effect of Wind Farm Based on Doubly-fed Induction Generator on Transient Out-of-step of Power Grid

To research the influence of wind farm based on doubly-fed induction generator on transient out-of-step characteristics of power grid. The single-machine infinite-bus model of wind-thermal-bundled system and a dynamic model of doubly fed wind farm are built by PSD-BPA software. The influence of proportion of wind connected, reactive power compensation, integration position and different fault point on transient out-of-step of power grid as well as the variations of thermal power angle and the action time of splitting device are investigated and compared. The conclusion is as follows: the proportion of wind connected and converters capacity are larger, wind farms have reactive power compensation, the better the transient out-of-step for wind-thermal-bundled sending system is restrained when the integration position of wind farms are in sending system.

Multi‐attribute node importance evaluation method based on Gini‐coefficient in complex power grids

Node importance evaluation contributes to the targeted protection of important nodes, which can enhance the invulnerability of complex power grids against cascading failures. Since the evaluation simply from the perspective of pure topology statistics fails to capture the electrical characteristics of power systems, the authors propose a multi-attribute node importance evaluation method based on Gini-coefficient in this study. This method considers not only the electrical characteristics of power grids when evaluation indices are built, but also the impact of the index weight method on the evaluation results. The simulations on the IEEE-39 system and the 500 kV Center China power system show that the proposed method is suitable to evaluate the node importance in power transmission grids, and can also improve the accuracy of the node importance evaluation.

Research on CDN network architecture design and safety protection for power grid

Based on a large amount of investigation, analysis and research of the application system status and network status of the power grid, the paper introduces a novel CDN network architecture for power grid, which has the power grid characteristics and meets the power grid requirements. In order to ensure the efficiency and stability of CDN system, the CDN network architecture key technologies include virtual CDN technology, software defined CDN technology, network measurement technology based on data analysis, database for CDN network, CDN management platform and load balance. Also, there are four aspects to ensure the security of CDN system, as network security, safety management system, CDN equipment safety and anti-leech mechanism which can be a reference for the construction of CDN network in power grid and other industries.

A Method for Sizing Energy Storage System to Increase Wind Penetration as Limited by Grid Frequency Deviations

Frequency deviation of power systems caused by grid-connected wind power fluctuations is one of the key factors limiting the level of wind penetration. Applying an energy storage system (ESS) to overcome the constraint of frequency deviation can increase the level of permitted wind penetration. This paper proposes a method to evaluate the wind penetration as limited by grid frequency deviation and to size the ESS to increase the permitted wind penetration to an expected level. The proposed method treats wind power fluctuations as a stochastic process rather than deterministic signal and takes the frequency response characteristics of power grid into full consideration. Application of the proposed method is based on theoretical derivations and does not require conducting dynamic simulation. It can catch the stochastic characteristic of wind power fluctuations.

Flexible distributed control and protection system for industrial objects – Consumers of electric power

Problems of efficient use of electric power and energy saving remain to be outstanding in our country. Implementation of smart systems for accounting and control of energy resources becomes the efficient solution of these problems. The problem of control and forecasting consumption of energy by the facility to cover internal needs represents an independent task. In general, systems are suggested which pertain to the control and accounting of energy resources supplied to the consumer of electric power. Approach to the development of system on the basis of concept of smart grids using dedicated complex of technical and software products allowing optimizing electric power expenditures, re-distributing electric power and promptly adjusting electric power grid characteristics is addressed in the present paper. Electric power supply control and monitoring devices receiving and transferring information to the server are installed in the places of connection of consumers to electric power supply grids. Server collects, accumulates and stores the information and is equipped with dedicated software allowing optimizing the load, preventing overloading and development of emergency situations within the electric power supply system. Such systems are suggested to be implemented by the facilities of nuclear industry.

Strategies for Success with Synchrophasors: Poised to Shine in the Eastern Region of the United States

Of the many electric power grid characteristics that contribute to its strength and effectiveness, there are two attributes that truly illustrate the nature of the grid, its fibrousness and its scale. Continental interconnectivity allows for fast, affordable, and reliable energy delivery but comes at the cost of complexity. In this way, the properties of the grid that embody its magnitude also contribute to the challenge of monitoring, operation, and control.

Context-independent centrality measures underestimate the vulnerability of power grids

Power grids vulnerability is a key issue in society. A component failure may trigger cascades of failures across the grid and lead to a large blackout. Within complex network analysis, structural vulnerabilities of power grids have been studied mostly using purely topological approaches, which assumes that flow of power is dictated by shortest paths. However, this fails to capture the real flow characteristics of power grids. We have proposed a flow redistribution mechanism that closely mimics the flow in power grids using the power transfer distribution factor (PTDF). We apply the model to the European high-voltage grid to carry out a comparative study for a number of centrality measures. 'Centrality' gives an indication of the criticality of network components. We also show a brief comparison of the end results with other power grid systems to generalise the result.

Method for evaluating the importance of power grid nodes based on PageRank algorithm

Cascading failures can easily occur and cause a major blackout in power grid when an important node breaks down. It is an essential problem to evaluate the importance of nodes in power system planning and operation. In this study, a method for evaluating the importance of power grid nodes based on PageRank (PR) algorithm is proposed. First, according to the comparison of the internet and power grid topology, a directed graph is established. Second, based on the directed graph, an index is proposed to estimate the importance of power grid nodes based on PR algorithm. Then, according to the characteristics of power grid, a modified algorithm, which takes the importance of nodal load, nodal load capacity and network topology into account, is proposed. Finally, case study shows the necessity of considering the factors to evaluate the importance of power grid nodes and the effective of index and algorithm to identify critical nodes in this study.

Automatic identification of transmission sections based on complex network theory

Taking transmission sections as the monitoring objects of power system security and stability level can largely improve the efficiency of analysis and control in power system operation. However, existing approaches for identifying transmission sections mainly depend on years of experience, which is not suitable for complicated and variable power systems with large scales. Thus, a novel method for automatic identification of transmission sections using complex network theory is proposed. The proposed method presents the fundamental conditions of transmission sections and identifies them from three levels: transmission lines, key transmission links and partition sections. First, based on the small-world characteristics of power grid, the index of transmission betweenness is presented to identify key transmission links from transmission lines. Then clustering algorithm of complex network is used to divide the power grid and to obtain partition sections from the key transmission links. Finally, the combinations of partition sections are selected and ranked as the transmission sections. Numerical results with CEPRI-36 system and a provincial system are provided to demonstrate the effectiveness and adaptability of the proposed method.

Probe on Questions and Mode of Renewable Resource Development and Utilization on Small Islands

Aiming at small islands location limits and the established power grid characteristics, the paper analyses some practical problems to be dealt with when renewable resource is utilized. Combined with the characteristics of small islands, the paper puts forward the new mode without energy storage devices, and designs a renewable resource application system driven directly by photovoltaic devices, emphatically analyses the key technology of no energy storage mode. The new mode effectively resolves the battle neck problem of traditional off-net mode.

Research on the Structural Characteristics of Transmission Grid Based on Complex Network Theory

Reasonable and strong structure is an important foundation for the smart transmission grid. For vigorously promoting construction of the smart grid, it is of great significance to have a thorough understanding of the complex structural characteristics of the power grid. The structural characteristics of several actual large-scale power grids of China are studied in this paper based on the complex network theory. Firstly, the topology-based network model of power grid is recalled for analyzing the statistical characteristic parameters. The result demonstrated that although some statistical characteristic parameters could reflect the topological characteristics of power grid from different ways, they have certain limitation in representing the electrical characteristics of power grid. Subsequently, the network model based on the electrical distance is established considering the limitation of topology-based model, which reflects that current and voltage distribution in the power grid are subject to Ohm's Law and Kirchhoff's Law. Comparing with the topology-based model, the electrical distance-based model performs better in reflecting the natural electrical characteristic structure of power grid, especially intuitive and effective in analyzing clustering characteristics and agglomeration characteristics of power grid. These two models could complement each other.

Development of Detection Platform for Grid-Connected Photovoltaic Inverters

To ensure both performance and security of grid-connected photovoltaic inverters(PVI), a detection platform for grid-connected PVI is researched. The testing method and procedures of grid-connected PVI are analyzed and the development course of this detection platform is described in detail. The detection platform consists of control computer, data acquisition system, RS 485 and GPIB system. In this platform, the solar-cell panel is simulated by programmable DC source, the power grid characteristics of power grid by programmable DC source and the load characteristic by programmable controlled RLC load. The whole detection system is controlled by LabVIEW software interface. The proposed detection platform can be used in the testing of electric performance, protection function, EMC and so on. Practical application shows that the configuration of this detection platform is rational and reliable，and its detection results are accurate.

Extended Topological Metrics for the Analysis of Power Grid Vulnerability

Vulnerability analysis in power systems is a key issue in modern society and many efforts have contributed to the analysis. Recently, complex networks metrics, applied to assess the topological vulnerability of networked systems, have been used in power grids, such as the betweenness centrality. These metrics may be useful for analyzing the topological vulnerability of power systems because of a close link between their topological structure and physical behavior. However, a pure topological approach fails to capture the electrical specificity of power grids. For this reason, an extended topological method has been proposed by incorporating several electrical features, such as electrical distance, power transfer distribution, and line flow limits, into the pure topological metrics. Starting from the purely topological concept of complex networks, this paper defines an extended betweenness centrality which considers the characteristics of power grids and can measure the local importance of the elements in power grids. The line extended betweenness is compared with the topological betweenness and with the averaged power flow on each line over various operational states in the Italian power grid. The results show that the extended betweenness is superior to topological betweenness in the identification of critical components in power grids and at the same time could be a complementary tool to efficiently enhance vulnerability analysis based on electrical engineering methods.

A novel local-world evolving network model for power grid

Many systems in the real world can be described by evolving models of complex network, one of which is power system. Classical network models show great inconsistence with practical power grids. Based on the essential evolution characteristics of power grid, we propose a new local-world evolving network model for complex power grid, which exists in many physical complex networks. The statistical properties and dynamics of the proposed model are analytically studied. It is found that the degree distribution of this new model has a power-law tail, and its scaling exponent is between 3 and ∞. Numerical simulations for West American power grid and North China power grid and their comparison with random network and scale-free network indicate that the new evolving network model captures the essential features of real-world power grid. Furthermore, it is proved that power grid is neither a random network nor a scale-free network.