Series Connection of Power Devices for Modular Multilevel Converter based High Voltage Direct Current Transmissions

随着用电量的持续增长，长距离大容量输电的需求大幅增加。与传统的交流输电方案相比，高压直流输电具有效率高、成本低、体积小等优点。高压直流输电技术经历了几代人的发展，加上电力设备的发展，形成了换流站的主干。最新一代基于完全可控的硅器件实现的电压型转换器，提供了极大的灵活性。然而，这些设备的可用电压容量极大地限制了系统电压水平，从而限制了传输容量和效率。为了解决这些问题，本项目将开发一种具有几乎零损耗和简单的自平衡和同步算法的串联机制，并将其在基于模块化多电平换流器的高压直流输电系统中实现。所开发的技术可能会改变许多其他高功率电子应用，如医疗设备的电源、工业电机驱动和聚变动力反应堆的脉冲电源。这些应用将对社会各方面产生影响，促进清洁绿色能源的使用。拟议的项目本质上是综合性的，涉及电力工程的不同方面，从器件、电路到系统级研究，将为下一代学生和工程师提供独特和高质量的培训。拟议的教育活动还将扩大妇女和其他代表不足的群体的参与。该项目的目标是开发一种新的串联功率设备连接技术，并探索其在模块化多电平变流器中的应用，以及在高压直流输电中的应用。它采用简单可靠的拓扑结构和电压自平衡算法，解决了串联电源设备中最具挑战性的问题。拟议项目的面向应用的研究将产生关于部件大小、权衡和优化研究以及系统级实施的关键知识。此外，还将对碳化硅器件的串联进行评估。待开发的多个原型将为实际实施、理论分析的验证提供工程经验和指导方针，并可用作电路和系统级原型的构建块。功率器件的串联将推动模块化多电平变流器技术的发展，提高额定电压，减少子模块数量，减小无源元件的尺寸。该项目将改变基于模块化多电平变流器的高压直流输电的实现。

As the electricity consumption continues to grow, the need for long distance bulk power transmission has increased significantly. Compared to traditional ac solutions, high voltage dc transmissions offer a number of advantages such as higher efficiency, lower cost, and smaller size. The high voltage dc transmission technologies have experienced a number of generations coupled with the development of power devices which form the backbone of the converter stations. The latest generation is based on voltage source converters enabled by fully controllable silicon devices that offer tremendous flexibility. However, the available voltage capacity of these devices has greatly limited the system voltage levels, which then limits the transmission capacity and efficiency. To address these issues, this project will develop a series connection mechanism featured by almost zero loss and simple self-balancing and synchronization algorithm, as well as its implementation in modular multilevel converter based high voltage dc transmission systems. The developed techniques can potentially transform many other high power electronics applications such as power supplies for medical equipment, industrial motor drives, and pulsed power supplies for fusion power reactors. These applications will impact various aspects of the society and promote the usage of clean and green energy. The proposed project is intrinsically comprehensive involving different facets of power engineering ranging from device, circuit, to system level research, which will provide unique and high quality training for the next generation students and engineers. The proposed educational activities will also broaden the participation of women and other under-represented groups.The objectives of this project are to develop a novel series power device connection technique and explore its implementation in modular multilevel converter with applications in high voltage dc transmissions. It addresses the most challenging issues in connecting power devices in series with a simple and reliable topology and voltage self-balancing algorithm. The application oriented study of the proposed project will generate critical knowledge regarding component sizing, trade-off and optimization study, and system level implementation. Moreover, series connection of silicon carbide devices will be evaluated. The multiple prototypes to be developed will provide engineering experience and guidelines for real implementation, verification of the theoretical analysis, and can be used as building blocks for circuit and system level prototypes. The series connection of power devices will advance the modular multilevel converter technology with increased voltage rating, reduced sub-module count, and reduced size of passive components. This project will transform the realization of modular multilevel converter based high voltage dc transmissions.