The integration of renewable energy via flexible DC transmission systems has become an important development direction for enabling large-scale renewable energy grid connection. The power supply characteristics of dual-end weak-feed AC systems differ significantly from those of traditional synchronous generator-based systems. Moreover, the converter stations operate in rectifier and inverter modes, leading to uncertainty in the direction of fault currents. This poses adaptability challenges for conventional model identification-based pilot protection schemes. To address these issues, a model identification pilot protection scheme for dual-end weak-feed AC systems based on active detection is proposed. First, the applicability of conventional model identification-based pilot protection in such systems is studied. On this basis, considering the concept of coordinated control and protection, and leveraging the high controllability of converter stations, a control strategy is proposed in which a characteristic frequency signal is superimposed and injected into the differential-mode component. The phase difference characteristics of the line model under the injection characteristic frequency signal are then analyzed. Finally, by combining a fault detection initiation criterion and a main fault identification criterion, a model identification pilot protection scheme that is independent of operating modes is constructed. Simulation results verify the effectiveness of the proposed scheme. The results show that the thresholds of the proposed protection scheme do not require simulation-based tuning and are not dependent on the accuracy of parameter calculation. The scheme can reliably identify internal and external faults, withstand transition resistances up to 300 Ω and noise interference of 25 dB, and is suitable for double-ended weak-feed AC systems.