±320 kV厦门双极柔性直流输电工程系统设计

为了避免采用对称单极接线柔性直流工程在可靠性、绝缘水平以及大容量换流变压器运输制造上的缺点,±320kV/1 000 MW厦门柔性直流输电工程是世界范围内第一个采用双极接线的柔性直流工程。文中以厦门工程为背景对双极高压大容量柔性直流工程的系统设计展开研究。首先,通过主接线优化设计使得采用双极接线的柔性直流工程具备3种运行方式,提高了系统的可靠性。其次,高压大容量柔性直流工程中设备裕度通常较小,通过对主回路参数开展精确计算从而实现小容量可关断器件支撑工程大功率传输。最后,对比了采用对称单极接线和双极接线柔性直流工程的暂态特性,即采用双极接线的工程暂态过电压较低但暂态电流恶化。提出通过暂态电流精确解析计算方法以及优化布置等方法,确保工程可关断器件的安全性。实践表明所提设计方法是可行和有效的。

System Design of Xiamen Bipolar VSC-HCDC Transmission Project

In order to overcome shortages of low reliability, high insulation level and difficulties in design and transportation for large capacity transformers, bipolar connection are adopted in voltage source converter based high voltage direct current(VSC-HVDC)projects, which is firstly introduced in ±320 kV/1 000 MW Xiamen VSC-HVDC project. Taking Xiamen project as an example, the study on system design for large-capacity VSC-HVDC project with bipolar connection is presented. Firstly, the single line diagram is optimized for multiple operation modes, in order to improve system reliability. Secondly, as the margin for main equipment is generally small in large capacity VSC-HVDC project, main circuit parameters are calculated accurately so that small-capacity insulated gate bipolar transistor(IGBT)can support large-capacity power transfer. Finally, the transient characteristics of VSC-HVDC systems with both kinds of connections are compared. The conclusion is that the transient overvoltage decreases while the transient current increases. The safety of IGBT under overcurrent is guaranteed by adopting the accurate analytical transient current calculation method and the optimized layout design. The practical work is done to show the feasibility and effectivity of the proposed design method.