Tightly regulated power electronic loads are penetrating in DC microgrid. They tend to draw constant power and thus, introduce negative incremental impedance destabilizing effect to DC microgrid. In practice, the stability condition of DC microgrid can be further exacerbated when large signal load changes occur. To ensure the large signal stability of DC microgrid with such loads, this paper proposes a new stabilizing control algorithm using nonlinear disturbance observer. The proposed method is applied to regulate the interleaved floating dual boost converter (IFDBC), which is widely recommended to feed DC microgrid by interfacing solar photovoltaic (PV) and energy storage systems. It has the merits of large voltage gain, high current-carrying capacity and low current ripples. Simulation and experimental results are provided to verify the efficacy of the proposed method.