Meshed Multi-Terminal Direct Current (MMTDC) Grid Protection and Control

近几十年来，全球对气候变化的关注日益增加。为了实现能源部门的脱碳和更可持续的能源系统，应增加可再生资源在整体能源结构中的份额。风能是一种低成本的清洁能源替代品，可以对冲高碳燃料的成本。最近，在风力发电项目上进行了大量投资。2014年，加拿大安大略省、魁北克省、阿尔伯塔省、新斯科舍省和爱德华王子岛省共安装了37个风电项目，总发电量为1871兆瓦。今年在安大略省安装了270兆瓦的风力发电项目，加拿大的风力发电装机容量最近已超过10吉瓦。可再生能源的大规模整合，特别是风能，对电力系统的运行提出了各种挑战，并推动了对改变现有输电基础设施的研究。***电力传输主要依靠交流电技术。在远距离上，交流线路的输电能力大大降低。高压交流技术的替代方案是高压直流（HVDC）技术。HVDC是一种环保的低损耗长距离输电技术，具有较低的成本和视觉冲击，并且需要较少的塔和输电线路空间（与交流相比）。除了加拿大现有的高压直流输电线路，如魁北克-新英格兰、纳尔逊河和温哥华岛，还有几条线路正在建设中，包括：阿尔伯塔西部和东部（预计2016年）、拉布拉多岛（预计2017年）和海事（预计2017年）。随着高压直流线路数量的增加，从长远来看，可以设想建立一个网状的多端直流电网，覆盖交流输电系统。该电网将使交流和高压直流输电系统能够吸收和经济地将可再生能源发电的新能源转移到偏远的负荷中心。*** MMTDC电网尚未建成。为了实现MMTDC电网，制造商和系统运营商正在努力克服一些技术限制。保护、控制和互操作性是最具挑战性的问题。拟议的研究将克服这些挑战，并为未来实现MMTDC电网及其将给社会带来的所有好处铺平道路，包括：提高电力系统可靠性，降低转换器额定和成本，降低备用容量，减少弃风和增加邻国之间的电力交易。此外，通过这项研究计划，一些研究生和本科生将在专业技能和追捧技能方面得到培训。**************************

In recent decades, there has been a worldwide growing attention towards climate change. To move towards the decarbonisation of the energy sector and a more sustainable energy system, the share of renewable resources in the overall energy mix should be increased. Wind energy is one of the low-cost alternatives for generating clean energy and provides a hedge against higher carbon fuel costs. Recently, significant investments have been made in wind generation projects. In 2014, 37 wind power projects, totaling a production of 1871 MegaWatts (MWs), were installed in the Canadian provinces of Ontario, Quebec, Alberta, Nova Scotia and Prince Edward Island. With this year's installation of the 270 MWs wind project in Ontario, Canada's installed wind generation has recently surpassed 10 GigaWatts. The large integration of renewable resources, in particular wind energy, poses various challenges to the operation of the electrical power system, and is driving research into changing the existing transmission infrastructure.***Transmission of electrical power primarily relies on alternating current (AC) technology. Over long distances, the power transmission capacity of AC lines is drastically reduced. The alternative to high voltage AC technology is high voltage direct current (HVDC). HVDC is an environment-friendly low loss power transmission technology and over long distances, offers lower costs and visual impact and requires less space for towers and transmission lines (compared to AC). Besides the existing HVDC lines in Canada such as Quebec-New England, Nelson River and Vancouver Island, several more lines are under construction, including: Western and Eastern Alberta (expected in 2016), Labrador-Island (expected in 2017) and Maritime (expected in 2017). With the increase in the number of HVDC lines, it is envisioned that, in the long run, a meshed multi-terminal DC (MMTDC) grid will be built and overlay the AC transmission system. This grid will allow the combined AC and HVDC transmission system to absorb and economically transfer new sources of energy generation from renewable resources to remote load centres. ***An MMTDC grid has not been built in practice yet. There are several technical limitations that manufacturers and system operators are trying to overcome to facilitate the realization of an MMTDC grid. Protection, control and interoperability are among the most challenging questions. The proposed research will overcome these challenges and will pave the road for future realization of an MMTDC grid and all the benefits that it will bring to the society, including: improved electric system reliability, reduced converter ratings and costs, lower reserve capacity, reduced wind curtailment and increased power trading among neighboring countries. Furthermore, through this research program, several graduate and undergraduate students will be trained in specialized and sought after skills.**************************