HVDC引起次同步振荡暂态扰动风险的机理分析
Mechanism Analysis of Large Disturbance Risk of Subsynchronous Oscillation Caused by HVDC
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摘要: 该文揭示一种由高压直流输电系统(high voltage DC,HVDC)引起的次同步振荡暂态扰动风险的产生机理。首先分析逆变侧交流系统扰动时,HVDC逆变站换流阀组的电流更替规律,从而得到交流系统故障造成逆变侧换相失败时,HVDC交、直流系统的等值回路。等值回路分析表明,换相失败发生时,直流线路等效短路,同时逆变侧交流系统部分或全部等效开路,并且直流短路电流全部由整流侧交流系统经三相整流桥提供。因此,流入整流桥的交流电流远大于正常值,会造成整流站附近发电机功率和转矩的暂态冲击,激发初值较高的轴系扭振,形成次同步振荡暂态扰动风险。采用时域仿真方法验证了HVDC电流更替规律和等值回路的分析结论,并仿真再现了实际系统中发生的由HVDC引起的次同步振荡暂态扰动现象。文中的研究成果为交直流互联系统次同步振荡风险预测和分析提供了新的理论依据。Abstract: The mechanism of large disturbance risk of subsynchronous oscillation caused by HVDC was investigated. Firstly, the valve current commutation law of inverter side under AC system disturbance was studied. Then, the equivalent circuits of both the AC and the DC systems of HVDC under the condition of commutation failure caused by AC system faults were achieved. On this basis, it was revealed that the DC short circuit current was supplied totally by AC system of rectifier side, which may induce the large disturbance risk of subsynchronous oscillation of generators nearby the rectifier side. The conclusion is verified by digital simulation and the large disturbance risk of subsynchronous oscillation caused by HVDC in an actual system is duplicated.
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