Aiming at the difficulties in renewable energy consumption and the demand for low-carbon development in the integrated energy system, an optimal scheduling method considering the joint operation of hydrogen-doped gas-fired units with hydrogen-doped and ammonia-doped coal-fired units is proposed. Firstly, to account for the uncertainty and correlation of wind and solar power outputs, a joint wind-solar output modeling approach based on the Frank Copula function is adopted. Typical wind-solar scenarios are generated through marginal distribution fitting using kernel density estimation, Monte Carlo sampling, and K-means clustering, thereby enhancing the robustness of the scheduling model. Meanwhile, energy conversion models for power-to-hydrogen and hydrogen-to-ammonia processes are developed to enable the efficient transformation of renewable energy into hydrogen and ammonia. Secondly, the refined operation model of hydrogen-doped combustion of gas-fired units and ammonia-doped combustion of coal-fired units is constructed in response to the demand for low-carbon transformation of conventional fossil energy units, so as to optimize the synergistic utilization of hydrogen and ammonia fuels in the power generation process. Then, the optimal dispatching model is constructed by combining with the laddering-type carbon trading mechanism with the goal of minimizing the total operation cost of the system, which is to minimize the total cost of the system. Moreover, the optimal scheduling model is constructed with the objective of minimizing the total operating cost of the system in combination with the stepped carbon trading mechanism and solved by the CPLEX solver. Finally, different scenarios are set up and comparative analysis are carried out. The results indicate that, the introduction of hydrogen-to-ammonia conversion, building upon hydrogen energy utilization, significantly mitigates wind and solar power curtailment within the system. The combined operation of hydrogen-doped gas-fired unit and ammonia-doped coal-fired unit leads to concurrent reductions in both total operational costs and carbon emissions. The study provides a reference for the development of decarbonization of integrated energy systems.