Cost-Effective Generator & MVDC Integration for Wind Farms

风力发电已成为最成功的可再生能源，是欧洲仅次于天然气的第二大发电能力(175千兆瓦)。截至2019年底，英国风电累计装机容量为23513兆瓦，发电量超过50太瓦时[2]。风电技术的主要驱动力之一是降低项目成本(CAPEX)和运营维护成本(O&M)。风力涡轮机收集系统作为一种潜在的节省成本的基础设施正受到越来越多的关注。已经提出了不同的替代方案：直流并联[3]、直流串联[4]和低交流频率采集系统[5]。一些研究人员提出，与标准交流技术相比，风力发电场的直流采集系统可能会降低运行成本，但它高度依赖于所使用的直流变流器技术[6，7]。该博士论文旨在研究一种新的综合直流采集系统，以提高风电场的效率，降低风电场的建设和运营成本。一个潜在的解决方案是，交流收集系统被直流系统取代，在直流系统中，交流网络由多电平转换器连接，以确保在任何情况下都能确保低谐波排放和电网合规性。本博士学位论文旨在利用现有的基于永磁同步电机和两电平电压型变流器的发电机和发电机变流技术。除风力涡轮机外，还可以在集热器系统中添加不同的元件，如光伏发电系统和储能元件，从而在不影响涡轮机运行的情况下提供惯性仿真和频率支持等辅助服务。该方案还处于早期开发阶段，需要在风力涡轮机和变流器的拓扑、控制、保护和稳定性方面进行进一步的研究。目的和目标本PHD提案的目标可概括为：1)识别、评估和比较不同的风电场收集系统，包括直流和低频交流，最大限度地降低资本支出和运营成本，并最大化效率、可靠性和可用性。2)对选定的一个或多个拓扑进行详细研究，包括建模、控制、性能评估、稳定性分析和安全保护概念。预计会有一个小型的实验室设置

Wind power has become the most successful renewable energy and represents the second-largest power generation capacity (175 GW) in Europe after natural gas [1]. At the end of 2019, there was an installed accumulative wind power capacity in the UK of 23,513 MW of wind power generating more than 50 TWh of energy [2]. One of the main drivers in wind technology is the reduction of the project cost (CAPEX) and the operation of maintenance cost (O&M). The wind turbine collection system is gaining attention as a potential cost saver infrastructure. Different alternatives have been suggested: DC parallel connection [3], DC series connection [4] and low AC frequency collection systems [5]. Some researchers have suggested that DC collection systems for wind farms might present reduced running cost compared to the standard AC technology, but it is highly dependent on the used DC converter technology [6,7]. This PhD proposal aims to investigate a new integrated DC collection system that might improve the wind farm efficiency and reduce the wind farm construction and operational cost. A potential solution, the AC collection system is replaced by a DC system where the AC network is interfaced by a multilevel converter ensuring low harmonics emissions and grid compliance in any scenario. This PhD seeks to use the existing generator and generator converter technology based on a permanent magnet synchronous machine and two-level voltage source converter. Apart from the wind turbines, different elements like photovoltaic generation systems and energy storage elements can be added to the collector system enabling the provision of ancillary services such as inertia emulation [8] and frequency support, without disturbing the turbine operation. This scheme is in the early development stages and requires further research regarding the wind turbine and converter topologies, control, protection and stability perspective.Aims and ObjectivesThe goals of this PhD proposal can be summarised as:1) Identify, evaluate and compare different wind farm collection systems including DC and low-frequency AC minimising the CAPEX and OPEX and maximise the efficiency, reliability and availability.2) A detailed study of one or more of the selected topologies including modelling, control, performance evaluation, stability analysis and safety protection concept. A small lab setup is expected