渝鄂背靠背柔性直流工程交流侧单相重合闸问题分析

Analysis of AC side single-phase reclosing problem of Chongqing-Hubei back to back MMC-HVDC project

当柔性直流输电工程接入弱交流系统时,如何与交流系统保护的重合闸策略配合需要深入研究。以渝鄂背靠背柔性直流输电工程为例,研究了交流线路重合闸期间系统电压和电流的变化规律。并结合柔性直流的故障穿越的控制逻辑,分析了断线故障下原有的控制策略的可行性。分析结果表明,断线故障之后,柔直的正序控制器和负序控制器不能完全解耦,造成控制系统不稳定。并且可能造成故障相过电压,在故障恢复时候可能使桥臂过流。因此,如果单根线路带柔性直流输电系统运行,发生接地故障时,应该在故障时间内尽量减少柔直的功率传输,或者不启用交流进线的重合闸功能。

The problems of the coordination strategy of MMC-HVDC transmission system connecting with weak AC system and AC side reclosing deserves further study. The voltage and current variation characteristic during AC line reclosing is studied in this paper, with Chongqing-Hubei back to back MMC-HVDC project as an example. Combined with the fault ride through control logic, the feasibility of the control strategy after the line disconnection is analyzed. The analysis results show that after the line disconnection, the positive sequence controller and the negative sequence controller cannot be completely decoupled, which causes the control system to be unstable. The disconnected line may overvoltage and when the fault is recovered, the overcurrent may occur in bridge arm. Therefore, when single line with MMC-HVDC operates and the break fault occurs, the power transmission of the straight line should be minimized during the fault time, or the reclosing function of the AC line should not be enabled.