•A constraint equivalent model for heat networks is proposed. In this model, the operational constraints of heat networks are mapped to the feasible region of CHP units, which protects the privacy of heat networks.•A boundary point search method is further developed to efficiently solve the constraint equivalent model and construct a high-accuracy approximation of actual feasible region.•A cooperation method with the rolling horizon strategy is proposed considering the uncertainties of heat and power loads. In the proposed cooperation method, the feasible region of CHP units is provided to the power system only once, which alleviates the communication burden.•Compared with other cooperation methods, simulation results show the advantages of the proposed cooperation method in balancing privacy protection and the quality of the solution.•The impact of heat storage tanks and uncertainties of heat loads on the boundaries of the feasible region is further analyzed. The cooperation of combined heat and power (CHP) systems can improve efficiency in energy utilization by fully utilizing the complementarity between heat and power. However, heat and power systems are operated by different companies where data sharing is restricted for privacy reasons, thus posing significant obstacles to collaboration. This paper proposes a coordinated operation method for CHP systems based on the constraint equivalent model. To preserve the operational constraints of heat networks and protect data privacy, a boundary point search method is firstly developed, where the operational constraints of heat networks are mapped to the feasible region of CHP units. Then, a multi-period cooperation model considering uncertainties of both networks is established based on the proposed constraint equivalent model and the rolling horizon strategy. Moreover, the impact of heat storage tanks and uncertainties of heat loads on the boundaries of the feasible region for heat networks is further analyzed. Simulation results demonstrate the effectiveness of the proposed constraint equivalent model and the cooperation method.