In the synchronous firing control system of the line commutated converter (LCC) HVDC project

the Area-Minimum (AMIN) control is responsible for the real-time calculation of the commutation margin of each converter valve. Assume the AMIN control identifies a converter valve's commutation margin falling below the minimum threshold under AC fault conditions. In that case

the converter valve will be fired immediately to prevent commutation failure. However

the existing AMIN control faces several issues such as slow response time

inaccurate calculations

and a negative impedance characteristic that can negatively impact the steady operation of the HVDC project. Therefore

this paper proposes an improved AMIN control using zero-sequence components and a current deviation term that provides quick and accurate calculations of the commutation margin by utilizing the zero-sequence component of three-phase voltages and considering the DC current changes during commutation. Additionally

employing the current deviation term helps to enhance the performance of the LCC-HVDC's control system. Our simulations show that the proposed improved AMIN control significantly enhances the first commutation failure immunity and lowers the probability of subsequent commutation failures

thereby facilitating the restoration of the LCC-HVDC project.