Thyristor controlled phase shifting transformer(TCPST) is a new type of flexible power flow control device. To explore its internal fault current distribution characteristics under typical faults, this paper builds the TCPST electromagnetic transient simulation model and combines the circuit transient equation and electromagnetic transient simulation to analyze the fault current distribution characteristics under two typical faults. Two measures to suppress fault current, namely gear shifting and trigger pulse optimization, were proposed and verified. The results show that there is a transition and steady-state process after the fault occurs, during which overvoltage and fault current occur periodically. The fault current levels of the grid-side and valve-side windings of the series transformer under the internal grounding fault were 17.46 times and 2.99 times the corresponding rated values respectively, and the fault current levels of the grid-side and valve-side windings under the external grounding fault averaged 10.49 times. For the parallel transformer, the fault current level of the valve-side winding was 2.99 times the rated value in case of an internal ground fault and 4.32 times the rated value in case of an external ground fault.