多馈入系统直流间耦合程度量化表征方法

目前多回超/特高压直流馈入华东电网，交直流系统之间交互作用及耦合复杂。为了量化表征多馈入直流间耦合程度，提出了多馈入直流系统的交流电压畸变耦合系数。通过计算一回直流内部故障引起其余直流逆变站换流母线交流电压的畸变程度，得到多直流间耦合系数。该耦合系数包含了直流输送容量对交流系统的影响、不同技术路线直流控制系统内部控制环节响应特性差异以及直流逆变站之间交流电网的阻抗特性等因素的综合评估。利用耦合系数提出耦合区域的概念，可用于评估多回直流同时换相失败的风险。以华东电网多馈入系统为例进行了仿真验证，结果表明所提出的耦合系数以及耦合区域表征形态与实际运行中的情况基本相符，该系数能为直流的规划和运行提供重要的技术参考。

A Characterization Method for Coupling Relation in Multi-Infeed HVDC System

At present, many HVDC/UHVDC projects are feeding into the East China Power Grid, and the interaction and coupling between AC and DC systems are complex. In order to characterize the coupling relation of multiple DC systems, an AC voltage distortion coupling coefficient of multi-infeed HVDC (ACDCC)is proposed. By calculating the bus AC voltage distortion of one inverter station caused by other HVDC system’s internal fault, the coupling coefficient of multiple DC systems is obtained, which covers an integrated assessment of such factors as the influence of DC transmission capacity on the AC system, the different response characteristics of HVDC control and protection system with different technical routes, and the AC system impedance characteristics between inverter stations. The concept of coupling area is put forward using coupling coefficient, which can be used to evaluate the simultaneous commutation failure risk of multi-infeed HVDC systems. A simulation verification is carried out on the multi-infeed system of East China Power Grid, and the results show that the proposed coupling coefficient and the characterization of coupling areas are basically consistent with the actual power system conditions. Therefore, the coupling coefficient can provide an important technical reference for the planning and operation of DC systems.