中文摘要：

结合中国高压直流输电现状和直流电网技术的发展，提出了利用面对面式DC／DC变换器互联不同电压等级的基于电网换相换流器（LCC）的高压直流（LCC—HVDC）系统的方案，总结了互联系统的优势并提出了一种依赖通信的适用于互联系统的控制器。基于两条实际LCC—HVDC线路背景，在PSCAD／EMTDC中搭建了利用±500kV／±800kV，1000MW面对面式DC／DC互联一条±500kV，3000MW线路和一条±800kV，7200MW线路的仿真模型。仿真结果说明，常规LCC控制不适用于互联系统，且验证了提出的控制器的有效性。所述控制器可在对原有LCC换流站控制改动最小的前提下实现互联系统的稳定运行。

英文摘要：

Based on the development of high voltage direct current （HVDC） and DC grid in China, a scheme of interconnecting two line commutated converter based HVDC （LCC-HVDC） links with different voltage levels through front-to-front type DC/ DC converter is proposed. The benefits of the interconnecting scheme are summarized and a communication-dependent controller suitable for interconnected system is proposed. Based on two practical LCC-HVDC links, a simulation case of interconnecting a ±500 kV, 3 000 MW LCC-HVDC and a ±800 kV, 7 200 MW LCC-HVDC through a ±500 kV/±800 kV, 1000 MW front-to-front type DC/DC converter is built. Simulation results show that the conventional LCC-HVDC controller is not suitable for the interconnected system and the efficacy of the proposed control is verified. The proposed controller enables the system to operate stably with minor modifications of the existing LCC converter control.