大规模新能源并网挤占常规机组开机，导致受端交流系统低惯量问题凸显。针对非同步交流电网经背靠背柔性直流互联场景，提出一种背靠背柔直双边虚拟同步构网型频率支撑控制策略，以提高互联“双高”电力系统的频率稳定性。其中，双端柔直换流站均采用虚拟同步型构网型控制方法，实现背靠背柔直对双边交流系统对称的频率主动支撑，并通过调整调频系数灵活改变背靠背柔直参与互联电网功率支援的程度，实现双端互联交流系统调频资源的动态共享。最后，基于小信号分析和PSCAD电磁仿真，研究了主要控制参数的影响效果，验证了在提高系统频率稳定特性方面的作用。

The integration of large-scale renewable energy sources displaces conventional generator commitments, leading to prominent low-inertia issues in receiving-end AC systems. To improve the frequency stability of interconnected power systems with high shares of renewables and power electronics, focusing on the back-to-back (BTB) VSC-HVDC system, this paper proposes a bilateral frequency support strategy for BTB VSC-HVDC with virtual synchronous generator-based grid-forming control. The grid-forming control method is employed in both terminals of VSC stations, enabling symmetric frequency support for two interconnected AC systems. By adjusting a specified coefficient, the degree of power support provided by BTB VSC-HVDC can be flexibly modified, achieving dynamic sharing of frequency regulation resources between interconnected AC systems. Finally, small-signal analysis and simulations in PSCAD are conducted to investigate the influence of control parameters and validate the effectiveness of the proposed strategy in enhancing system frequency stability.