基于控保协同的柔性低频输电系统电流差动保护性能提升方案  

Improvement of Current Differential Protection Performance of Flexible Low-Frequency Transmission System Based on Control and Protection Cooperation

作　　者：郑涛 康恒 Zheng Tao;Kang Heng(State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,North China Electric Power University,Beijing,102206,China)

机构地区：[1]新能源电力系统国家重点实验室(华北电力大学),北京102206

出　　处：《电工技术学报》2025年第7期2162-2177,共16页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金联合基金资助项目(U2166205)。

摘　　要：低频输电是一种兼具传统交直流输电技术优势的新型输电技术,在海上风电送出、城市电网柔性互联等场景具有良好的应用前景。当柔性低频输电系统低频线路不对称故障时,模块化多电平矩阵变换器(M3C)通常采用故障控制策略实现相应的控制目标,使得故障电流的特征受到影响,进而影响线路保护的性能。该文首先分析了M3C电容电压不均衡原因,针对电容电压均衡控制限制M3C负序电流自由度问题,采用一种基于环流控制的电容电压均衡策略,实现了M3C电容电压均衡控制与负序电流控制相互解耦;其次,基于电流差动保护动作特性,提出一种基于控保协同的柔性低频输电系统保护性能提升方案。该方案以提升电流差动保护的性能为目标,综合M3C故障控制策略确定负序电流控制方案,并结合M3C桥臂过电流问题选取负序电流参考值;最后,在PSCAD/EMTDC中搭建了相应的柔性低频输电系统仿真模型,通过大量的仿真实验,验证了所提方案的可行性和有效性。Low frequency transmission technology enhances the transmission distance and capacity by reducing the transmission frequency,which is a new type of transmission technology taking into account the advantages of traditional AC and DC transmission,and has a good application prospect in the scenarios of medium and distant sea wind power transmission,new energy pooling and urban flexible interconnection.Flexible low frequency transmission system is double-ended power electronics systems,when the low frequency transmission line occurs asymmetrical faults,M3C(modular multilevel matrix converter)will use the fault control strategy to achieve the corresponding control objectives,and the characteristics of the fault current will be affected by the control strategy,which in turn affects the performance of the traditional line protection.For this reason,this paper proposes a current differential protection performance improvement scheme for flexible low frequency transmission system based on control and protection synergy,which improves the action performance of current differential protection by actively regulating the magnitude of negative sequence current in the line through the M3C.First,according to the power relationship during the asymmetrical fault on the low frequency side,the bridge arm active power imbalance component is theoretically deduced,the reasons for the M3C capacitor voltage imbalance are analysed,and for the problem that capacitor voltage balance through negative sequence current control limits the degree of freedom of the M3C negative sequence currents,a capacitor voltage balance strategy based on the M3C circulating current control is adopted,which realises the M3C capacitor voltage balance control with the mutual decoupling of negative sequence current control.Secondly,based on the action characteristics of the current differential protection,the influence of negative sequence current on the action performance of the current differential protection is analysed,and it is pointed out that the action per

关 键 词：柔性低频输电系统 模块化多电平矩阵变换器 负序电流控制 电容电压均衡 电流差动保护 

分 类 号：TM77[电气工程—电力系统及自动化]