A control method of fault current in MT-HVDC grid based on current limiter and circuit breaker

Abstract

In order to realize selective isolation of fault lines in multi-terminal high voltage DC (MT-HVDC) grids, it is necessary to ensure that the sound lines can still transmit power normally after the grounding fault occurs in a DC power network. If the fault line needs to be cut before the converter is blocked, a DC circuit breaker (DCCB) with large switching capacity is often required. At present, the extreme fault over-current and the high cost of DCCBs have become the prominent contradiction in MT-HVDC projects. Reducing the breaking stress of power electronic devices of the circuit breaker and controlling its cutting-off time are the major difficulties in this research field. In this paper, a topology of a hybrid DCCB with an inductive current limiting device is proposed. By analyzing its working principle, the calculation method of key parameters is given, and a four-terminal HVDC grid is built in a PSCAD/EMTDC platform for fault simulation. The results show that compared with the traditional circuit breaker, this topology can effectively limit the rising speed and maximum current of fault current when the system fails, and quickly remove the fault line, so as to meet the suppression requirement of the HVDC system for fault current.

Keywords

• bipolar short circuit
• fault current limiting
• hybrid dc circuit breaker
• ultiterminal hvdc grid