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由于在建设新的直流输电系统时缺乏足够的输电走廊，越来越多的高压直流线路架设在已有的交流线路输电走廊上。这种做法会使得临近的交流线路在直流线路中感应出基波电压并由此产生环流。电网换相换流器–模块化多电平型电压源换流器(line-commutated converter-modular multi- level converter，LCC-MMC)混合直流输电非常适用于远距离大容量的电力传输，是一种具有广阔应用前景的技术，相比于传统的 LCC-HVDC 拓扑具有明显的优势。因此，在LCC-MMC混合直流输电系统的规划阶段，有必要在临近交流线路对直流线路的耦合效应这一问题上进行综合的研究分析。该文首先对直流线路上的基波环流在MMC中产生的直流偏置进行理论研究；然后基于 LCC-MMC 混合系统的等效模型以及快速有效的计算方法，对影响耦合效应的一系列因素进行研究，包括平行架设长度、交直流线路的接近距离、换流器的参数、交流系统的零序电流分量以及故障情况等；最后形成具有一定工程意义的参数对应曲线。“,”Due to the lack of sufficient right-of-way in constructing a new transmission system, more and more high voltage direct current (HVDC) circuits are built onto the existing corridor, alongside the high voltage alternating current (HVAC) transmission lines. One problem of such an application is steady state induction of fundamental frequency voltages and consequent circulating currents into the DC circuit. The line-commutated converter-modular multi-level converter (LCC-MMC) hybrid transmission system is a promising way to transmit bulk power over long distance with overhead lines, which has many advantages over the conventional HVDC topology. In the stage of planning a new hybrid system, comprehensive studies need to be carried out on the possible coupling effect from the nearby AC lines. In this paper, the theoretical formula of MMC DC bias under fundamental frequency circulating current was first analyzed, which shows refined consistency to the simulation result. The parameters of the coupled system on DC Bias were then studied, leading to a discussion about the compromise between the separation distance and parallel distance. A suggestive relationship between separation distance and parallel distance was put forward to instruct the future engineering projects.