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

全球电网最近正在大规模整合可再生能源，主要是光伏和风能。这种转变是由减少二氧化碳排放的需求驱动的，以限制温室效应，缓解全球变暖，同时提高供应的安全性。大型煤电厂是二氧化碳排放的主要来源，电力需求不断增长，特别是在大城市/工业区。在这种情况下，可再生能源是减少电力系统对环境影响和碳足迹的唯一可行选择。可再生能源的主要缺点是，它们的生产地点通常远离能源的消费地点。英国的典型例子是海上风力发电场，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获得更高的风速，并将对环境的影响降到最低，但可能导致发电机和用户之间相隔数百公里。当距离增加时，传统的、成熟的交流传输技术由于能量损失大而变得不可持续。高压直流（HVDC）是一种能够实现长距离大容量电力传输的技术（架空电缆600公里，海底电缆40公里），由于其效率更高，成本更低。与交流输电相比，直流输电更为复杂，需要依靠电力换流站在风电场侧将交流电转换成直流电，并在向大陆供电时再转换成交流电。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。最基本的问题是，如果采用传统技术，这些转换器可以像一座中型工业建筑那么大，对于一个典型的1GW装置来说，它们可以重达1万吨。这对高压直流输电线路的两端提出了两个主要挑战：1。海上挑战：在海上安装大型和批量转换器增加了平台的成本，降低了海上风电的竞争力。此外，转换器的建造、调试和维护既复杂又昂贵。陆上挑战：陆上转换器通常位于人口稠密的地区，这些地区需要能源，但土地昂贵且有限。此外，环境和视觉景观的影响也是一个问题。该项目将为海上和城市站提出紧凑的电力转换拓扑结构，在保持足够性能的同时减少尺寸、重量、成本和环境影响。此外，调试阶段将考虑到探索的拓扑结构，以增加系统级的模块化并减少施工工作量。这些拓扑将与主要的行业利益相关者进行讨论，并与最先进的标准解决方案进行比较，以确定最具吸引力的选择，这种权衡的结果将提供给三个工作包：拟议转换器的设计、计算机模拟和实验室演示器的构建，以证明拟议技术的可行性和功能。

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.