伴随着城市电网规模的扩大，以及用户对供电质量和可靠性要求的不断提高，城市核心区供电正面临诸多问题。基于电压源型换流器的柔性直流以其独特的技术优势成为解决此类问题的有效手段之一。同交流电网发展类似，为提高运行可靠性和调度灵活性，城市电网中的双端或多端柔性直流将逐步互联为多电压等级的直流网络。城市直流网络在结构和控制上具有“分级分层”的特点，其结构的多元性以及协调控制的复杂性对未来城市电网的安全稳定运行提出新的挑战。本项目拟在研究城市多端柔性直流协调控制与优化运行的基础上，通过分析城市直流应用特点，构建城市直流网络，研究其运行模式及控制策略。据此，提出考虑交流电网运行需求及安全稳定要求的城市直流网络控制策略，实现城市直流网络的协调控制及优化运行。精确合理的直流场景模型是基础，控制策略是主体，仿真验证是手段，把握整体、理顺层次、逐次推进。

With the enlargement of urban power grid (UPG), as well as the increasing requirements on the quality and reliability of power supply, the power supply of urban core area is facing a lot of problems. High voltage direct current based on voltage source converter (VSC-HVDC) is a good choice to solve those problems for its technical advantages. In the future, the existing two-terminal or multi-terminal direct current (MTDC) system, similar to the AC grid, will turn into multi-voltage-level DC network. The urban DC network is multi-level in voltage and hierarchical in control, and it’s a new challenge for future UPG to keep safe and stable, due to the pluralistic structure of urban DC network and complexity of coordinated control system. A structure of urban DC network, which is adapted to the development of UPG, is proposed in this project. The characteristics of the urban DC network are analyzed based on the coordinated control and optimal operation technology of urban VSC-MTDC. Meanwhile, the operation mode and control strategy of urban DC network is studied. According to the above, the control strategy of urban DC network is established considering the demands of AC grid to be operated in safety and stability. Furthermore, the coordinated control strategy and optimal operation method is accomplished. Accurate DC scene modeling is the basis; Control strategy is the body; Simulation is the tool. Grasp the whole; Classify the levels; Push the sequences.