Abstract: The low charging efficiency and short available mileage problems have seriously hindered the further development of electric vehicles (EVs). Due to the low output voltage of the preceding EV, it is necessary to use a portable high-gain DC-DC converter to realize fast charging and energy interaction between two EVs. Thus, a nonlinear disturbance observer (NDO) based on the backstepping algorithm is proposed for the interleaved dual boost converter (IDBC) to improve the power converter's ability on rejecting internal and external disturbances. The NDOs not only estimate the parasitic parameters of the system to improve the robustness of the system against internal parameter disturbances but also estimate output current and input voltage in real-time without additional sensors, thus reducing the system's cost. Using the estimations of NDOs, backstepping controllers are further developed to strictly guarantee the output voltage stability in the sense of a large signal. In addition, the phase current balance compensator (PCBC) is proposed to solve the current sharing problem among six paralleled channels, which can reduce the heat loss and improve the service life of the device. Finally, simulation and experimental results verify the effectiveness of the proposed controller.