基于电压源型换流器的多端直流（VSC-MTDC）输电系统是构建智能电网的重要组成部分。直流电压控制是VSC-MTDC系统的关键，需从本地乃至上层控制探索系统协调和优化策略，其相关理论和方法亟待完善。本项目在对VSC-MTDC系统电磁暂态建模的基础上，改进基于直流电压-有功功率调节特性的多点直流电压控制策略，探讨不同输电场合和运行工况下控制策略的设计方法；结合直流网络潮流计算和换流站运行特性，探索基于上层控制和N-1准则的换流站协调控制策略，提出无解情况下系统的最优化方法；结合数值仿真验证相关理论的有效性和准确性。

Voltage source converter based multi-terminal direct current (VSC-MTDC) transmission system is an important part of smart grid. Dc voltage control is the key of VSC-MTDC control system, which needs study coordination and optimization strategies in the local and upper level, therefore its related theories and methods are urgent to be perfected. On the basis of electromagnetic transient modeling, this project improves a multipoint dc voltage control strategy with dc voltage-active power characteristic and explores a design method of control strategy under different transmission occasions and operation conditions. Combined with dc network power flow calculation and converter operating characteristics, some research focus on N-1 principle based converter stations coordination control strategy and an optimization method when no solution is put forward. Finally, the validity and accuracy of related theory is checked by numerical simulation.