分析了谐波不稳定产生的原因及条件,以某±800 kV特高压直流输电实际工程为研究对象,采用PSCAD/EMTDC搭建仿真模型,研究了由换流变压器铁芯饱和引起的谐波不稳定现象及规律.仿真结果表明,系统在单极10％额定功率下运行时.换流变压器铁芯饱和稳定因子为负.此时外界扰动导致换流变压器铁芯严重饱和,系统出现谐波不稳定现象.最后提出了抑制谐波不稳定的措施,仿真分析验证了其有效性.%The causes and conditions of UHVDC system harmonic instability are studied and the simulation model of a practical ± 800 kV UHVDC transmission system is established in PSCAD / EMTDC. The phenomenon and regularity of harmonic instability caused by the core saturation of converter transformer are analyzed. Simulative results show that,when system operates in monopole mode with 10 % rated power,its core saturation stability factor is negative,and once the transformer core is heavily saturated by the external disturbance,system harmonic instability will occur. Some countermeasures are proposed and the effectiveness is verified by simulative analysis.
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