A coupled hydraulic-thermal dynamic model for the steam network in a heat-electricity integrated energy system

Steam is the most common heat support medium in an industrial park's heat-electricity integrated energy system (HE-IES). The steam network (SN) has excellent time delays and heat storage capacity compared to the grid. However, regarding the HE-IES scheduling, previous studies ignored the dynamic delay characteristics of the hydraulic-thermal calculation processes in the SN and the time delays between the SN and the grid when they were operated concurrently. Thus, this paper proposes an improved method of characteristics to incorporate the dynamic hydraulic-thermal processes and quantify the dynamic offsets. To solve the time asymmetry problem associated with the grid, the SN is modeled by a thermal-electrical analogy model and graph theory. The effectiveness of the proposed model was verified by actual SN operating data, and less than 9% relative error between the model outputs and actual results was obtained. The model can satisfy the HE-IES operation re-quirements with high accuracy. Moreover, in contrast to a thermodynamic process, the hydraulic process can be regarded as a transient process. A generic delay time-distance formula is fitted and applied in the expression of the thermodynamic processes to better improve the HE-IES operations.