阐述了电流开关函数的详细推导过程，简要介绍了变压器铁心饱和不稳定的产生机理，首次把调制理论应用于解决换流变压器铁心饱和不稳定问题，并提出了一种判断此种谐波不稳定的新方法，然后基于南方电网2010年数据，采用PSCAD/EMTDC建立了云广±800 kV直流输电系统详细电磁暂态的仿真模型，对三相接地故障激发的铁心饱和不稳定现象进行了仿真试验，验证了该新方法的正确性。

Due to its intuition, clear physical conception and convenient to use, in the calculation of harmonics of power system more and more attentions are paid to modulation theory. In this paper the detailed derivation of current switching function is expounded, and the mechanism causing transformer core saturation instability is presented briefly. It is the first time to apply modulation theory to solve converter transformer core saturation instability and a new method to judge such a harmonic instability is proposed; then based on the data of China Southern Power Grid in 2010 and by use of PSCAD/EMTDC, a simulation model for detailed electromagnetic transient of ±800 kV DC power transmission system from Yunnan to Guangdong is built, and using the built model the simulation research on core saturation instability caused by three-phase grounding fault is performed. Simulation results verify the correctness of the proposed method.

国家重点基础研究专项经费项目(2004CB217901);“十一五”国家科技支撑计划重点项目(2008BAA13B01)

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