渝鄂异步互联对华中电网运行特性的影响

Operation characteristic analysis of Central China Power Grid in unsynchronized interconnection of Chongqing and Hubei Power Grid

针对规划的渝鄂异交流同步互联通道改造为背靠背柔性直流异步互联通道后对华中电网的运行特性的影响进行计算分析。比较了异步联网前后三峡近区短路电流变化情况,分析了四川电网内部发生大扰动后对华中电网安全稳定性的影响,以及华中系统小干扰稳定特性的变化情况。计算结果表明,渝鄂背靠背投运后,三峡近区短路电流减小,华中电网振荡模式有所变化,三峡近区的暂稳特性严重恶化,同时龙泉、恩施电网存在孤网运行的风险。针对上述问题提出新建龙斗四回、宜渔双回、恩渔四回的网架补强方案,验证了该方案的有效性。研究结果对华中电网规划、运行及国内同类直流工程设计都具有一定参考价值。

The synchronous interconnection between Chongqing and Hubei power grid in China is planned to be unsynchronized by back to back VSC-HVDC. The operation characteristic of central China power grid should be realized with such un-synchronization. Short circuit computation and small signal analysis with Central China Power Grid as well as simulation of large disturbance within Sichuan power grid are undertaken to find the difference before and after unsynchronized interconnection is done. Results show that with the unsynchronized interconnection short circuit current decreased in adjacent three gorge area and low frequency oscillation modes have small variation while transient stability suffers serious deterioration. On the other hand unexpected islanding might happen near longquan substation or Enshi power grid. It is proposed to add one more line to the existing Longdou lines, Yiyu line and Enyu lines which are proofed to be effective against such stability deterioration and risk of islanding. This study could be referred to the Central China Power Grid planning, power grid operation and other similar HVDC transmission projects.