Flexible power reversal strategy for LUXI back-to-back HVDC project to address minimum power constraints

In the LUXI back-to-back (B2B) HVDC project, traditional power reversal strategies typically require the synchronized operation of two line-commutated converter-based high-voltage direct current (LCC-HVDC) units, namely LCC-HVDC-U1 and LCC-HVDC-U2, each constrained by an approximately 10% minimum power limit. This constraint significantly restricts operational flexibility, especially during power reversal and low-load operation. To address this issue, this paper proposes a flexible power reversal strategy for the LUXI B2B project that enables decoupled operation of LCC-HVDC-U1 and LCC-HVDC-U2 and achieves bidirectional power dispatch while mitigating the minimum power constraint. The proposed strategy dynamically shapes the power reversal trajectory by coordinating transitions among dual-unit mode, single-unit mode, and round power mode. In addition, the constraints encountered during the power reversal process, together with its practical application scenarios, are systematically analyzed. Simulation results based on a detailed electromagnetic transient (EMT) model of the LUXI B2B project demonstrate that the proposed strategy significantly enhances operational flexibility and maintains robust adaptability under scenarios with high renewable energy penetration.