±800kV云广特高压直流控制方式的动态特性分析

Analysis on Dynamic Characteristic of Control Mode for ±800 kV Yun-Guang UHVDC

云广±800 kV特高压直流输电系统建成之后,将形成远距离和大容量交、直流输电并列运行的电网格局,特高压直流的控制方式对电网的稳定性有重要影响。为此在电磁暂态仿真软件EMTDC中对±800 kV云广直流双极运行下,整流侧分别采用定电流和定功率控制时,交流系统整流侧与逆变侧故障对直流系统的影响,直流控制系统与交流系统的响应过程进行了详细的计算分析,对两种控制方式下系统的动态特性进行了对比分析。结果表明,与整流侧采用定电流控制相比,定功率控制时,交流系统故障期间系统各电气量的变化较缓慢,故障清除后系统恢复过程中,直流电流的突增会导致短时换相失败,且故障后直流系统的恢复时间较长。

When Yun-Guang 5：800 kV ultra high voltage direct current （UHVDC） project is completed, a parallel AC/DC power system with long distance and heavy capacity will come out. And the UHVDC control mode has important influence on the power system stability. Consequently, Yun-Guang ±800 kV UHVDC bipolar model was established in EMTDC. The effect of AC system faults on the UHVDC transmission system in both constant current and constant power control modes and the response of UHVDC control system were computed and analyzed, respectively. Moreover, the dynamic characteristic of the AC/DC system in two control strategies was comparatively analyzed. The results show that, compared with the constant current mode, all the electrical variables change more slowly than in constant power mode during the power system fault. After the fault is cleared, a sudden increase of DC current may cause short time commutation failure. And the system needs more time to come back to normal operation.