  Due to the nature of distributed secondary control paradigm, DC microgrids
are prone to malicious cyber-physical attacks, which could be unbounded to
maximize their damage. Existing resilient secondary control methods addressing
unbounded attacks require that the first time derivatives of cyber-physical
attack signals be bounded. The secondary defense strategy presented in this
letter relax such a strict constraint by addressing more generally unbounded
attack signals and hence, enhance the resilience of DC microgrids in
adversarial environments. Rigorous proofs, based on Lyapunov techniques, show
that the proposed method guarantees the uniformly ultimately bounded
convergence for both voltage regulation and proportional load sharing under
generally unbounded attacks. Comparative case studies further validate the
enhanced resilience of the proposed attack-resilient control strategy.
