特高压多端混合直流输电系统启动与故障穿越研究

Research on Start and Fault Ride-through Strategy for Ultra-high Voltage Multi-terminal Hybrid DC Transmission System

采用常规直流与柔性直流混合的特高压多端直流输电系统是昆柳龙直流工程技术方案之一,对采用全桥和半桥混合拓扑的特高压柔性直流输电换流器充电时的均压问题进行分析,提出了两种不同的充电策略。研究了混合三端直流系统的启停顺控流程和直流线路瞬时故障穿越、重启策略。在RT-LAB中搭建三端混合直流输电系统,连接外部阀控装置进行实时仿真实验,实验结果验证了提出的充电策略的正确性,表明所提出的直流线路故障穿越和重启策略可以很好地实现系统穿越故障,使系统重新进入稳态。此外,在±10.5 k V/60 MW柔性直流背靠背样机上进行了充电策略验证和直流双极短路故障穿越后重启策略验证,充分验证了采用全半桥混合拓扑柔直系统的故障穿越能力。

This paper discussed one of the schemes for Kunliulong project, an ultra-high voltage three-terminal DC transmission system with hybrid VSC topology. The hybrid topology consisted of full-bridge sub-module and half-bridge sub-module brings in unbalanced capacitor voltages during charging process. Two charging strategies were proposed to deal with the problem. Besides, the charging and start-up process were researched with corresponding control strategies. The fault ride-through and restart strategy for DC fault was also proposed. A three-terminal hybrid DC system was then modeled in RT-LAB and connected with physical valve controller, based on which, a series of HIL tests were carried out to validate the effectiveness of the proposed charging strategies. Finally, a 10.5 kV/60 MW back to back VSC prototype applying 4500 V/3000 A IGBT was built to test the proposed DC fault ride-through and charging strategy. The experiment results illustrated the validity of the proposed strategy.