<p>Commutation failure (CF) during the fault recovery stage of line-commutated converter-based high-voltage direct current (LCC-HVDC) systems remains a critical issue under both rectifier-side and inverter-side AC faults. Although previous studies have examined CF mechanisms during fault recovery at the sending or receiving ends AC faults conditions, these scenarios have typically been treated as independent problems, lacking a unified suppression strategy. In this paper, based on simulation results of LCC-HVDC systems under sending-end and receiving-end AC faults, the mechanisms of CF during fault recovery are systematically analyzed. It is revealed that improper control mode switching of the inverter and the rapid advancement of the inverter-side commutation bus voltage phase angle are the primary causes of CF in both cases. To address this, a unified CF mitigation method based on adaptive extinction angle control and DC current control is proposed. By compensating for the advancement of the inverter-side commutation voltage phase and moderating the recovery speed of the DC current, the proposed method effectively suppresses CF during fault recovery at both the sending and receiving ends. Real-time digital simulation (RTDS) results confirm the effectiveness of the proposed approach in mitigating CF during fault recovery in LCC-HVDC systems. Compared with the benchmark control in the CIGRE benchmark HVDC system, the proposed method achieves reductions of over 90% and 66% in the CFFR rate under sending-end and receiving-end faults, respectively, as demonstrated in the simulation tests conducted in this paper.</p>