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

1 000 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. This work is supported by National Basic Research Program of China(973 Program)(No. 2014CB247400)and Post-doctoral Science Foundation of China(No. 2016T90690).