Coordinated Control of LCC-MMC Cascaded Hybrid HVDC for Receiving-End Fault Overcurrent Limiting

Receiving-end short circuit fault will lead to the DC voltage reduction in the LCC-MMC cascaded hybrid HVDC system. It can cause the active power surplus of the renewable energy and reactive power changes of the sending-end LCC, which both contribute to overcurrent of the sending-end MMC. To address this issue, a coordinated control consisting an active power control and an improved voltage dependent current order limit (VDCOL) is firstly proposed. The former control aims to achieve DC current regulation and active power balance between AC/DC sides of the sending-end MMC. Based on the reactive power variation characteristics analysis during the DC voltage recovery, the latter control is proposed to prevent overcurrent of sending-end MMC via defining the operation region. Finally, the effectiveness of the coordinated fault current limiting control is validated by simulation in MATLAB/Simulink.