特高压换流站三柱四绕组结构换流变压器谐波抑制研究

Harmonic Elimination for Three-limb Four-winding Converter Transformer in UHVDC Converter Station

换流变压器是特高压直流输电系统换流站的重要组成部分,是承担交直流转换的核心设备之一。考虑到换流变易受由阀侧导通引起的谐波电流和无功缺额的影响而产生绕组故障和铁心震动等问题,提出一种新的适用于特高压直流输电系统的空间棱柱结构三柱四绕组式换流变压器模型。基于统一磁等值电路理论,给出了该模型的电磁耦合电路,通过附加绕组等值负磁通来实现谐波滤除功能。利用电磁耦合电路等效电路,依据附加绕组对谐波的分流作用,削弱阀侧谐波电流向网侧传递的影响。在PSCAD/EMTDC中搭建特高压直流输电系统与三柱四绕组式换流变模型,通过仿真计算,验证了所提出换流变电磁耦合模型的正确性。仿真结果表明,依据该电磁耦合模型设计的等效电路能在不影响原有系统正常换流的前提下有效提升换流变网侧电压电流波形质量。

Converter transformer is one of the core unit of converter station in UHVDC system.A three-limb four-winding converter transformer model on the basis of the UMEC method is designed,suited for the UHVDC system,to reduce the vulnerability to both winding faults and core vibrations caused by the harmonics and the reactive power deficiency.An electro-magnetic coupling circuit is designed to produce negative equivalent magnetic flux as the current and voltage filtering approaches with extra winding weakening the impact of harmonic propagating between the two original windings.A simulation model is finally developed with a UHVDC system and a designed converter transformer.The harmonic filtering function of the model were tested and validated with excellent performances as theoretical expectation.The results also demonstrate that the electro-magnetic coupling circuit can effectively improve the waveform quality without affecting normal operation of the UHVDC system,which is more convenient for practical engineering applications.