摘要
混合直流异步联网系统结合了常规直流和柔性直流各自的优势,提供了一种更为灵活的电网互联方式。本文首先对常规直流单元和柔性直流单元主回路与控制系统进行分析。继而基于PSCAD/EMTDC仿真平台,搭建混合直流异步联网仿真系统,研究混合直流异步联网系统的稳态、动态及暂态特性,分析混合直流异步联网系统故障恢复特性。最后根据研究结果提出改善常规直流单元电压稳定性及故障恢复特性的措施。研究结果表明:混合直流异步联网系统不仅具有良好的稳态及动态响应,而且可以利用柔性直流单元优越的控制性能,增强受端电网的电压支撑能力,更为重要的是能够减小常规直流单元换相失败的概率并改善交直流系统故障恢复特性,提高常规直流输电运行的可靠性。
Hybrid DC asynchronous interconnection system combines the advantages of LCC-HVDC and VSC-HVDC to provide a more flexible power grid interconnection mode. Firstly, this paper analyzes the circuit and control system of the LCC-HVDC and VSC-HVDC units. Then based on PSCAD/EMTDC simulation platform, a hybrid DC asynchronous interconnection simulation system is built to study the steady, dynamic, transient and fault recovery characteristics of hybrid DC asynchronous inter-connection system. Finally, according to the research results, a measure to improve the voltage sta-bility and fault recovery characteristics of LCC-HVDC system is proposed. The results show that hy-brid DC asynchronous interconnection system has good steady-state and dynamic response. At the same time, hybrid DC asynchronous interconnection system can effectively improve the voltage support capability of the receiving grid by the excellent control characteristic of MMC-HVDC. More importantly, it can restrain the commutation failure of the LCC-HVDC station, improve the fault re-covery characteristics of the AC/DC system and increase the reliability of the LCC-HVDC system.
