基于多直流功率支援的直流偏磁治理策略

Suppression Method of DC Magnetic Bias Based on Multi-DC Power Support

现有的直流偏磁治理均是从抑制设备的研发层面着手,无法实现从根源上治理直流偏磁。该文提出了一种基于多直流功率支援的直流偏磁抑制方法。首先在PSCAD/EMTDC平台上搭建了宜昌电网变压器中性点直流电流分布仿真模型,根据同一输电断面内多条直流输电线路可进行功率支援的特点,提出主动降低处于单极-大地运行方式的直流线路的输送功率,由同一输电断面中其他直流线路承担相应输送功率缺额,主动制造反向不平衡入地电流以中和单极-大地回线中的直流电流,以此降低交流电网中变压器中性点直流电流的幅值。最后,采用遗传算法对送端机组出力进行优化,并借助PSASP平台对功率转移后送端电网的静态稳定性及暂态稳定性进行了校验。

The conventional research of suppressing DC magnetic bias mainly focus on the development of DC magnetic bias blocking device, which cannot solve the DC magnetic bias fundamentally. This paper proposes a suppression method of DC magnetic bias based on multi-DC power support. Firstly, based on PSCAD/EMTDC, we establish a DC current distribution simulation model of transformer neutral point in Yichang power grid. Secondly, from the perspective of coordination running and power support between DC lines in the same transmission section, the transmission power of HVDC is reducd, which is operating in monopole-ground return mode, and the reduction of transmission power will be transferred by other HVDC projects in the same transmission section, to actively generate reverse unbalanced grounding current to neutralize the DC current in monopole-ground return line, which can reduce the amplitude of DC current at transformer neutral point in AC grid. Finally, the generation output of sending-end unit is optimized by genetic algorithm and then the static and transient stability of the sending-end grid after power transfer are verified based on PSASP simulation system.