城市电网建设存在的问题及其发展前景

城市电网是电力系统的重要组成部分,随着社会对城市供电要求急剧增加,城市电网的建设和改造是推动电网现代化管理,提高电网供电可靠率,切实提高电能质量,提高电网整体供电能力的一项重要任务。文章阐述了现阶段城市电网建设中存在的问题以及未来的发展趋势。提出做好电网规划,优化电网系统结构,全面推进调度管理自动化、变电站综合自动化和配电自动化已成为电力发展的需要。

System Recovery-Aware Virus Propagation Model and Its Steady-State Analysis

Network structures and human behaviors are considered as two important factors in virus defense currently. However, due to ignorance of network security, normal users usually take simple activities, such as reinstalling computer system, or using the computer recovery system to clear virus. How system recovery influences virus spreading is not taken into consideration currently. In this paper, a new virus propagation model considering the system recovery is proposed first, and then in its steady-state analysis, the virus propagation steady time and steady states are deduced. Experiment results show that models considering system recovery can effectively restrain virus propagation. Furthermore, algorithm with system recovery in BA scale-free network is proposed. Simulation result turns out that target immunization strategy with system recovery works better than traditional ones in BA network.

Stand-Alone Wind Power System Operating with Different Storage Structures

This paper deals with control method related to a wind system operating in stand-alone applications. The stand-alone wind system is composed of three energy transfer subsystems： wind generator subsystem （wind turbine and electrical generator）, energy storage subsystem, respectively, specific local network subsystem （controlled loads）. This wind power system performs in the same time the maximization of wind energy conversion and the power balance between produced and required power. Three structures of the energy storage subsystem, based on buffer battery operation and/or capacitor voltage control, are discussed. The simulation results show that the proposed stand-alone wind power system ensures a good management of the local energy request. The design of the structures is analyzed in Matlab/Simulink environment, using PowerSim toolbox.

Research on IPv6 Transition Evolvement and Security Architecture of Smart Distribution Grid Data Communication System

Smart distribution grid needs data communication systems as a support to complete their important functions. The smart distribution grid of the data and information are increasingly adopting internet protocol and Ethernet technology. The IP addresses are more and more important for the smart distribution grid equipment. The current IPv4 protocol occupies a dominant position; therefore, the challenges of the evolution to IPv6 and network security are faced by data communication systems of the smart distribution grid. The importance of data communications network and its main bearer of business were described. The data communications network from IPv4 to IPv6 evolution of the five processes and four stages of the transition were analyzed. The smart distribution grid data communications network security and types of their offensive and defensive were discussed. And the data communications network security architecture was established. It covers three dimensions, the security level, the communications network security engineering and the communications network security management. The security architecture safeguards the evolution to IPv6 for the smart distribution grid data communication systems.

Examples of Cable-Bar Modular Structures Based on the Class-Theta Tensegrity Systems

The relationship between forms and forces is one of the main topics of structural morphology. This harmonious coexisting link is very strong for systems in tensegrity state, commonly called ＂tensegrity systems＂. It is currently apparent that, among the tensegrity systems, there also exist cable-bar cells with a discontinuous network of cables. It is possible to design a separate set of cables inside the cable-bar elementary cell and to establish a self-stress state of equilibrium. In this connection, the author of this paper suggested to assume a new Class-Theta tensegrity systems. Each of the basic tensegrity systems termed Class-Theta possesses an external and internal set of tension components. The shape of Greek capital letter 69 （Theta） reflects two sets of such components （two sets of tendons, cables, etc.）. This notation corresponds to Skelton＇s Class-k tensegrity structure. As shown in this paper, the Class-Theta tensegrity cell can exemplify a geometrically and practically useful form for the lightweight and long-span modular structures, mainly but not only in view of civil engineering and architecture.

Smart Grid Concept and Developments： The Relevance to South Africa

Smart grid is a concept and not a computer system or some sort of hardware. Therefore, smart grids can have multiple shapes because there is no single unified concept of what constitutes a ＂Smart Grid＂. Smart grid is considered a core concept in sustainable electricity generation and consumption while being projected as a silver-bullet to electric power system challenges. South Africa＇s dwindling reserve margin, high CO_2 emissions and future energy mix are outstanding reasons for her smart grid deployment. Who receives the credit for smart grid neology is contentious and smart grid definition is diverse. However, there is a consensus on its attributes or benefits. The establishment of SASGI （South Africa Smart Grid Initiative） and Eskom＇s commencement of deploying a hybrid smart grid model are proofs of the country＇s commitment towards smart grid concept and developments. Having recognized the relevance of smart grid concept and its developments, South Africa is presented with the opportunity to ＂leap-frog＂ and enhance the relevant proven applicable smart grid solutions.