Steady-state Security Region of Integrated Energy System Considering Thermal Dynamics

The worldwide promotion of electric heating improves the operational flexibility of the power system (PS). However, it also increases the risk of cascading failure due to the bi-directional interaction with the heating system (HS). To prevent such contingencies and facilitate prompt post-outage adjustments, the steady-state security region (SSR) of the integrated energy system (IES) will be a valuable and effective tool. This paper derives an accurate SSR model for the heat and electricity IES, composed of a novel combined heat and power (CHP) unit model, the AC power flow model, and the dynamic HS model. An equivalence-based hyperplane method (EHM) is then proposed to solve the SSR model. The EHM treats the SSR as the intersection of the time-invariant and time-varying parts, and each part is described with a set of hyperplanes. On this basis, the sequential SSR (SSSR) is defined for IES to characterize the impact of CHP and HS integration, with which the time-varying process resulting from the thermal dynamics is divided into three periods for investigation. Numerical studies verify the accuracy and efficiency of the SSSR and EHM and demonstrate the influences of the CHP, HS integration, and thermal dynamics on the secure operation of the PS.