柔性直流输电系统的谐振问题及主动抑制方法

发布时间：2018-12-26 14:24

【摘要】：电网不对称故障会产生电压负序和零序分量,并激发换流变压器注入更大的低次谐波,增大功率器件承受的电气应力,且基于电压源换流器高压直流输电(voltage source converter based high voltage direct current,VSC-HVDC)系统的交流阻抗在变压器特征谐波频段大部分呈容性,使系统在该频段易发生谐振,导致换流站热过载和波形质量问题凸显。因此,讨论换流站交、直流侧谐波相互作用的机理,建立从交流侧看入换流站的正负序交流低频阻抗模型,提出等效增大换流站输出阻抗支路谐波电阻的方法,全面扼制换流站输出阻抗支路谐波电流,且不影响系统基波电阻。利用电力系统仿真软件EMTDC建立了VSC-HVDC模型,对柔性直流输电系统中的谐振问题以及主动抑制方法进行仿真研究。仿真结果表明,所提出控制策略能有效抑制谐振过电压,因此,提高了柔性直流输电系统不对称故障下运行的安全性。
[Abstract]:Asymmetrical fault of power network will produce negative voltage sequence and zero sequence component, and stimulate converter transformer to inject larger lower harmonic, increase the electrical stress of power device, and based on voltage source converter, high voltage direct current transmission (voltage source converter based high voltage direct current,) The AC impedance of VSC-HVDC) system is capacitive in the characteristic harmonic frequency band of transformer, which makes the system easy to resonate in this frequency band, resulting in the problems of thermal overload and waveform quality of converter station. Therefore, the mechanism of harmonic interaction between AC and DC side of converter station is discussed, the low frequency impedance model of positive and negative sequence AC in converter station is established, and the method of increasing the harmonic resistance of output impedance branch of converter station is put forward. The output impedance branch harmonic current of the converter station is completely choked, and the fundamental resistance of the system is not affected. The VSC-HVDC model is established by using the power system simulation software EMTDC. The resonance problem and active suppression method in the flexible direct current transmission system are simulated and studied. The simulation results show that the proposed control strategy can effectively suppress the resonant overvoltage, so the security of the flexible HVDC system under asymmetric faults is improved.
【作者单位】：长沙理工大学电气与信息工程学院;
【基金】：国家自然科学基金项目(51277013,51277014) 湖南省研究生创新项目(CX2013B373)~~
【分类号】：TM721.1

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