Large-Signal Instability Mechanism and Stability Enhancement of the Submarine DC Power System

Due to extreme operational conditions, submarine DC power systems are prone to large-signal instability. Therefore, it’s essential to investigate the underlying physical mechanisms and develop effective stabilization strategies. This paper first establishes a large-signal model of the submarine DC power system. Incorporating the physical characteristics and control dynamics in the system, the large-signal stability boundary is defined by using the mixed potential function method, and key factors influencing the stability boundary are identified. Subsequently, the instability mechanisms, along with the effect mechanisms of these key factors’ variations on large-signal stability, are further analyzed based on the model of source-side and load-side power interactions. The analysis indicates that suppressing the transient reduction in the voltage conversion ratio of the submarine converter is critical to maintaining stability. Motivated by this insight, a switching frequency compensation strategy is proposed, and it demonstrates improved disturbance-rejection performance compared with conventional approaches. Finally, simulations and hardware-in-the-loop experiments are conducted to validate the stability analysis results and the effectiveness of the stability enhancement strategy under large disturbances.