Abstract: If the inverter station of a flexible HVDC transmission system suddenly loses its AC load during operation, the AC and DC voltages will abruptly and abnormally rise, posing significant harm to the primary equipment. To mitigate this issue, it is necessary to implement a last breaker function to prevent such occurrences as much as possible. In response to the aforementioned problem, this paper, considering the common AC yard topology of flexible HVDC projects, proposes an control strategy based on visual programming at the AC station control level. This strategy enables the AC station control program to preemptively identify when the system is operating with only the last breaker in service and to lock out the interlocking conditions for remote opening of this last breaker, thereby reducing the possibility of inadvertent opening of the last breaker.