EPSRC 1st Grant: "Compact Modular Multilevel Converters for Offshore Wind Integration"

全球电网最近经历了可再生能源的大规模整合，主要是光伏和风能。这种转变是由减少二氧化碳排放、限制温室效应和缓解全球变暖同时改善供应安全的需要推动的。大型燃煤电厂是二氧化碳排放的主要贡献者，电力需求不断增长，特别是在大型城市/工业区。在这种情况下，可再生能源是减少对环境的影响和减少电力系统碳足迹的唯一可行的替代方案。可再生能源的主要缺点是，它们通常在远离能源消耗地的地方生产。英国的典型例子是海上风电场，它们在北海收集能源，并将其输送到大陆。在海上安装风力发电场可以提高风速，并将对环境的影响降至最低，但可能会导致发电机和用户之间相隔数百公里。随着距离的增加，传统和成熟的交流输电技术由于其高能量损耗而变得不可持续。高压直流(HVDC)是一种能够实现长距离大规模电力传输的技术(架空电缆为600公里，海底电缆为40公里)，这要归功于它更高的效率和更低的成本。与交流输电相比，直流输电更复杂，依靠换流站在风电场一侧从交流输电到直流输电，然后在电力输送到大陆时再回到交流输电。高压直流换流站设计的主要问题是尺寸、重量、成本、效率和制造/维护。基本的问题是，这些基于传统技术的变流器，可以像一座中型工业建筑一样大，对于一个典型的1GW安装来说，可以像10000吨那么重。这在高压直流输电线路的两端带来了两个主要挑战：1.离岸挑战：在离岸安装大型和散装换流器增加了平台的成本，并降低了离岸风能的竞争力。此外，转炉的建造、调试和维护既复杂又昂贵。2.陆上挑战：陆上转炉通常位于人口稠密的地区，需要能源，但土地昂贵且有限。此外，环境和视觉景观的影响也是一个令人担忧的问题。该项目将为海上和城市电站提出紧凑型电力转换拓扑结构，在保持适当性能的同时，降低尺寸、重量、成本和对环境的影响。此外，将在所探索的拓扑中考虑调试阶段，以增加系统一级的模块化并减少施工工作量。将与关键的行业利益相关者讨论这些拓扑，并将其与标准的最先进解决方案进行比较，以确定最具吸引力的选项，这种权衡的结果将提供给三个工作包：拟议的转换器的设计、计算机模拟和建造实验室演示器，以证明拟议的技术的可行性和功能性。

The global electricity network has recently been experiencing a large scale integration of renewable energy sources, mainly photovoltaic and wind. This transformation is driven by the need for a reduction of carbon dioxide emissions, to limit greenhouse effect and mitigate global warming at the same time improving security of the supply. Large coal power plants are the main contributors of CO2 emissions, and electricity demand is constantly growing, especially in large urban/industrial areas. In this scenario, renewable energies are the only viable alternative to reduced environmental impact and carbon footprint of the electrical system. The main drawback of renewable energies is that they are usually generated far from where the energy is consumed. Typical examples in the UK are offshore wind farms, harvesting energy in the North Sea and delivering it to the mainland. Installing wind farms offshore gives higher wind speed and minimises the environmental impact, but might result in hundreds of kilometres separating the generator and the users. When distance increases, traditional and well-established AC transmission technology becomes unsustainable for its high energy loss.High Voltage DC (HVDC) is the technology enabling bulk power transmission over long distances (>600km for overhead cables, >40km for submarine cables), thanks to its higher efficiency and lower cost. Compared to AC power transmission, DC transmission is more complex, relying on Power Converter stations to transform from AC to DC at the wind farm side and back to AC when power is delivered to the mainland. Major issues in the design of converter stations for HVDC are size, weight, cost, efficiency, and manufacturing/maintenance. The basic problem is that these converters, when based on conventional technology, can be as large as a medium-sized industrial building and as heavy as 10000 tons for a typical 1GW installation. This poses two main challenges, at both ends of the HVDC link:1.Offshore challenge: installing large and bulk converters offshore increases the cost of the platform, and reduces competitiveness of offshore wind. In addition, construction, commissioning and maintenance of the converter are both complex and expensive.2.Onshore challenge: the converter onshore is often located in densely populated areas where energy is needed but land is expensive and limited. Also, environmental and visual landscape impact are a concern. This project will propose compact power conversion topologies for offshore and urban stations that have reduced size, weight, cost and environmental impact while maintaining adequate performances. In addition, the commissioning phase will be taken into account in the explored topologies, in order to increase modularity at system level and reduce construction efforts. The topologies will be discussed with key industry stakeholders and compared to standard state of art solutions, to identify the most attractive option, and the result of this trade off will feed into three work packages: design of the proposed converter, computer simulation and construction of a laboratory demonstrator to prove the feasibility and functionality of the proposed technology.