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

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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.