交直流微电网群的多端直流互联与潮流优化技术研究

By interconnecting the microgrids, a larger scale of aggregated cluster i.e. multi-microgrids can be formed. With the microgrids supporting each other, the reliability of the system is enhanced. Meanwhile, the overall performance of the multi-microgrids can be improved by further optimization of power flow via the interconnection system. This project first studies the interconnection scheme and its interconnection characteristics of multi-microgrids based on the multi-terminal DC system, in which way different types of microgrids can be interconnected compliantly. The integrated control schemes of the converters in the multi-terminal DC system with adaptive impedance droop control and global voltage information based autonomous control are designed to achieve the stable operation of multi-microgrids. On this basis, a novel topology of interline DC power flow controller based on modular multilevel converter is proposed. Furthermore, the method of its realizing well-allocated power flow control in multi-terminal DC system is studied. The dynamic and stochastic characteristics of the sub-microgrids in the multi-microgrids are analyzed. A multi-objective dynamic stochastic optimal power flow problem concerning economic and safe operation, efficient using of new energy and suppressing power fluctuations is studied, and a comprehensive solution of optimal power flow in multi-microgrids is derived. Finally, the research content of this project is formed into a theoretical system, which provides theoretical reference and technical support for organizing economical, reliable and flexible multi-microgrids.

将微电网进行互联，使之形成更大规模的聚合群体，微电网之间相互支撑，系统的可靠性得以增强。同时，可通过互连线对微电网间的能量流动做进一步优化，实现微电网群综合性能的提升。本项目首先研究基于多端直流系统的微电网群互联方案及其互联特性，实现不同类型微电网间的高兼容互联；设计带有自适应阻抗式下垂控制与全局电压信息自主控制的多端直流系统换流器综合控制方案，解决微电网群的稳定运行问题。以此为基础，提出基于模块化多电平换流器的新型线间直流潮流控制器，研究其应用在多端直流系统中实现高调配度潮流控制的方法措施；分析微电网群中子微电网的动态和随机特性，研究涵盖经济安全运行、新能源高效利用与功率波动抑制的微电网群多目标动态随机潮流优化方法，给出微电网群潮流优化综合解决方案。最后，将本项目的研究内容形成理论体系，为组建经济、可靠、灵活的微电网群提供理论借鉴与技术支持。

与单个微电网相比，微电网互联聚合后将更加可靠和高效，本项目首先研究了微电网群多端直流互联的方案设计，设计了基于交错并联型三端口变换器和输出串联三端口变换器的微电网群互联架构，达到了适配不同电压类型直流微电网的目的，分析了所提互联方案变换器拓扑结构、工作状态与功率传输特性等。进一步研究了互联变换器的协调运行方法与实时优化运行控制策略，解决了微电网群的稳定运行问题。提出了基于CET (capacitive energy transfer)的新型线间直流潮流控制器拓扑，结合直流互联系统各端换流器，实现了微电网群内部潮流的高灵活度控制。研究了基于非合作博弈论的微电网群潮流优化方法，通过多目标优化算法进行求解，在经济安全运行的基础上，进一步减少了微电网中“弃光”、“弃风”现象，削弱了微电网产生的并网波动，降低其对配电网侧的影响，实现了微电网群互联后可靠性、经济性的有效提升。对相关变换器、潮流控制器和控制优化算法进行了对应的仿真、实验验证与案例分析，仿真实验结果验证了所提方案的有效性。本项目的研究成果指导建成了哈尔滨工业大学校园微电网，并获中国自动化学会自然科学二等奖，可为组建经济、可靠、灵活的微电网群提供有效的理论指导与技术支持。