State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (North China Electric Power University), Beijing 102206, China

The cost and bulk of DC circuit breaker (DCCB) are closely related to its breaking current. From the aspect of reducing the breaking current of DCCB, an adaptive controller is designed for fault current limiting of half-bridge modular multilevel converter (MMC). By adjusting the reference value of the DC voltage and the capacitor voltage of the sub-modules in MMC under DC fault condition, the development speed of fault current can be limited automatically and quickly. The current limiting principle of the adaptive controller is analyzed by mathematical analysis. A four-terminal DC grid is simulated in the PSCAD/EMTDC environment to verify the effectiveness of the adaptive controller. The simulation results show that, compared with the control scheme without current limiting control, the proposed adaptive controller can not only reduce the breaking current of the DCCBs and energy absorbed by the arresters, but also speed up the recovery of the system after fault.