Load Margin Assessment of Electricity-heat System Based on the Improved CPF

Energy supply security is the basis to ensure a stable operation of integrated energy system (IES). The selection of appropriate indicators and calculation methods play a pivotal role in the field of security assessment. Considering the strong coupling of multi-energy flows, large system scale and complex structure, the traditional methods which only consider single energy flow and a fixed load mode are not accurate enough to evaluate the energy supply security. To solve the above problems, a load margin assessment method based on the improved continuation power flow (CPF) is proposed in this study. Firstly, according to the steady state of electricity-heat system, a general mechanism-based model related to load increase is developed as the basic algorithm for the CPF process. Next, the CPF method is extended to the IES, where the directions of the load increase are set by the first-order difference to describe the states of the system in real-time. Considering that the load increase should be restricted in a practical range for real-world application, this paper proposes a non-negative lower load limit setting method based on empirical probability distribution. Finally, experiments on both a typical IES and an IES of an industrial park in China are performed, which validates the effectiveness and practicability of the proposed method for quantitative security assessment of electricity-heat system.