光网络发展展望

光网络的具体含义到底是什么，这是一个仁者见仁，智者见智的问题。但有一点是取得了共识的，即未来的光网络应该是一个应用灵活、可靠、性能稳定的网络。它应该满足传输各种信号，如SDH、ATM、IP等的所有基本要求（即灵活性、可升级性和系统生存性应能独立于比特率和协议）。这样一个网络应该能够对各种信号进行有效的传输、调度、保护和管理。因此，如果我们希望能对光网络今后的发展做一点预测的话，必须综合考虑传输技术、光网络产品、光网络设计以及光标准研究等方面的发展情况，才能尽量避免偏颇。     

蓬勃发展中的中国卫星通信事业

从70年代初期开始,我国利用国际卫星组织(INTELSAT)的卫星建立了国际卫星通信。国内卫星通信是从1985年开始的。当时按照国家确定的“租星过渡,C频段起步”的正确方针,建立了国内卫星通信网。经过20多年的努力,我国已建立了一个应用广泛、技术先进、业务较为齐全、具有一定规模的卫星通信网。与此同时,我国卫星通信的科研、工业也取得了巨大发展。     

A Consortium Blockchain-Enabled Double Auction Mechanism for Peer-to-Peer Energy Trading among Prosumers

This paper investigates a double auction-based peer-to-peer (P2P) energy trading market for a community of renewable prosumers with private information on reservation price and quantity of energy to be traded. A novel competition padding auction (CPA) mechanism for P2P energy trading is proposed to address the budget deficit problem while holding the advantages of the widely-used Vickrey-Clarke-Groves mechanism. To illustrate the theoretical properties of the CPA mechanism, the sufficient conditions are identified for a truth-telling equilibrium with a budget surplus to exist, while further proving its asymptotical economic efficiency. In addition, the CPA mechanism is implemented through consortium blockchain smart contracts to create safer, faster, and larger P2P energy trading markets. The proposed mechanism is embedded into blockchain consensus protocols for high consensus efficiency, and the budget surplus of the CPA mechanism motivates the prosumers to manage the blockchain. Case studies are carried out to show the effectiveness of the proposed method.     

Multi-Timescale Modeling and Dynamic Stability Analysis for Sustainable Microgrids: State-of-the-Art and Perspectives

The increasing trend for integrating renewable energy sources into the grid to achieve a cleaner energy system is one of the main reasons for the development of sustainable microgrid (MG) technologies. As typical power-electronized power systems, MGs make extensive use of power electronics converters, which are highly controllable and flexible but lead to a profound impact on the dynamic performance of the whole system. Compared with traditional large-capacity power systems, MGs are less resistant to perturbations, and various dynamic variables are coupled with each other on multiple timescales, resulting in a more complex system in-stability mechanism. To meet the technical and economic challenges, such as active and reactive power-sharing, volt-age, and frequency deviations, and imbalances between power supply and demand, the concept of hierarchical control has been introduced into MGs, allowing systems to control and manage the high capacity of renewable energy sources and loads. However, as the capacity and scale of the MG system increase, along with a multi-timescale control loop design, the multi-timescale interactions in the system may become more significant, posing a serious threat to its safe and stable operation. To investigate the multi-timescale behaviors and instability mechanisms under dynamic inter-actions for AC MGs, existing coordinated control strategies are discussed, and the dynamic stability of the system is defined and classified in this paper. Then, the modeling and assessment methods for the stability analysis of multi-timescale systems are also summarized. Finally, an outlook and discussion of future research directions for AC MGs are also presented.     

Modelling and Coordinated Control of Grid Connected Photovoltaic, Wind Turbine Driven PMSG, and Energy Storage Device for a Hybrid DC/AC Microgrid

In a DC/AC microgrid system, the issues of DC bus voltage regulation and power sharing have been the subject of a significant amount of research. Integration of renewable energy into the grid involves multiple converters and these are vulnerable to perturbations caused by transient events. To enhance the flexibility and controllability of the grid connected converter (GCC), this paper proposes a common DC bus voltage maintenance and power sharing control strategy of a GCC for a DC/AC microgrid. A maximum power point tracking algorithm is employed to enhance the power delivered by the wind turbine and photovoltaic module. The proposed control strategy consists of primary and secondary aspects. In the primary layer control, the DC bus voltage is regulated by the GCC. In the secondary layer, the DC bus voltage is maintained by the energy storage device. This ensures reliable power for local loads during grid failures, while power injection to the grid is controlled by an energy management algorithm followed by reference generation of inductor current in the GCC. The proposed control strategy operates in different modes of DC voltage regulation, power injection to the grid and a hybrid operating mode. It provides wide flexible control and ensures the reliable operation of the microgrid. The proposed and conventional techniques are compared for a 15.8 kW DC/AC microgrid system using the MATLAB/Simulink environment. The simulation results demonstrate the transient behaviour of the system in different operating conditions. The proposed control technique is twice as fast in its transient response and produces less oscillation than the conventional system.     

云冈石窟博物馆

项目位于大同市云冈石窟景区.景区内有世界闻名的始开凿于北魏的巨大石窟艺术群,为了既不影响自然和人文景观,同时又使陈列馆建筑与历史文化、宗教艺术互动和对话,建筑的主要功能都建在地下,只有屋顶和南立面露出地面,主入口北立面通过下沉广场与紧邻的石窟联系起来.鉴于游人在室外参观最后几窟的位置已经比陈列馆高出20多米,站在高处远眺能看见陈列馆的屋顶,因此屋顶成为本建筑最重要的第五立面,设计立意来自佛海茫茫的浩瀚意境的形式物化,呈波浪状像从地面自然生长出来的无限延伸;细部设计源自昙曜五窟大佛身上飘逸的衣纹;屋顶天窗的处理犹如神秘的佛眼,带着迷人的微笑回望着千年的宗教石窟艺术遗存,同时也为地下室空间带去一丝光明.