适应多能源基地远距离输送电能的混合四端直流输电系统控制策略研究

Control Strategy of Hybrid Four-Terminal HVDC Transmission System Dedicated for Long-Distance Power Delivery from Multiple Energy Bases

为将大规模可再生能源远距离输送到不同的负荷中心,提出一种适用于多个能源基地远距离输电的混合四端直流输电系统。系统采用电网换相换流器(LCC)和模块化多电平换流器(MMC)作为送端,两个MMC换流站作为受端。介绍系统的拓扑结构和数学模型,设计协调控制方案,分析混合直流输电系统的启动过程。利用换流站控制与直流侧开关的配合,设计混合四端电网的直流故障无闭锁穿越策略。在PSCAD/EMTDC中搭建四端电网仿真模型,验证该系统在启动、直流故障及无闭锁穿越等工况下的运行特性。研究结果表明,该系统可为新能源的大规模送出提供一种新选择。

In order to transmit large-scale renewable energy to different load centers over long distances,this paper proposes a hybrid four-terminal DC transmission system suitable for long-distance transmission of multiple energy bases.The system adopts a line commutated converter(LCC)and a modular multilevel converter(MMC)as the sending terminals,and two MMC converters at the inverter side.The system's topology and mathematical model are introduced,a coordinated control scheme is designed,and the start-up process of the hybrid DC transmission system is analyzed.Based on the coordination between the control strategy of converter and DC side switch,a non-blocking DC fault ridethrough strategy for a hybrid four-terminal power grid is designed.A four-terminal power grid simulation model was built in PSCAD/EMTDC to verify the system's operating characteristics under start-up,DC fault,and non-blocking ride-through conditions.The research results show that the system can provide a new option for large-scale distribution of renewable energy.