Fault current analysis of MMC based HVDC system under DC pole-to-pole fault condition

The need of transmitting large-scale renewable power over long distance has promoted the development of Modular Multilevel Converter based High Voltage Direct Current (MMC-HVDC) technology. Most of the existing research effort relies on the numerical simulation to study the fault characteristics of MMC-HVDC, which doesn´t get the analytic solutions of the fault current during dc pole to pole fault condition. This paper mainly focuses on studying the fault characteristics and analyzing the mathematical model of the fault current of the MMC-HVDC system via dc-link pole to pole short circuit before blocking the sub modules. An improved analytic approach of calculating the fault current of MMC-HVDC based on derived equivalent circuit models is proposed in the paper. The calculated fault currents based on the proposed methods are compared with the simulation results from PSCAD/EMTDC.