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容量（175吉瓦）。截至二零一九年底，英国累计风力发电装机容量为23，513兆瓦，发电量超过50太瓦时[2]。风能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成本节约基础设施正在受到关注。已经提出了不同的替代方案：直流并联[3]，直流串联[4]和低交流频率收集系统[5]。一些研究人员认为，与标准AC技术相比，风电场的DC收集系统可能会降低运行成本，但它高度依赖于所使用的DC转换器技术[6，7]。本博士论文旨在研究一种新的集成直流收集系统，该系统可能会提高风电场的效率并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，其中交流网络通过多级转换器连接，确保在任何情况下都能实现低谐波排放和电网合规性。本博士旨在利用现有的发电机和发电机变流器技术的基础上，永磁同步电机和两级电压源变流器。除了风力涡轮机，不同的元件，如光伏发电系统和能量存储元件可以添加到收集器系统，从而能够提供辅助服务，如惯性仿真[8]和频率支持，而不会干扰涡轮机的运行。该方案处于早期开发阶段，需要对风力涡轮机和转换器拓扑结构、控制、保护和稳定性进行进一步研究。目的和目标本博士论文的目标可以概括为：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，最大限度地减少CAPEX和OPEX，并最大限度地提高效率、可靠性和可用性。2）对一个或多个选定的拓扑结构进行详细研究，包括建模、控制、性能评估、稳定性分析和安全防护概念。一个小的实验室设置预计

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