Dynamic Modeling and Analysis for Electricity-Gas Systems With Electric-Driven Compressors

The dynamic gas flow model with static electric-driven compressor (EDC) model has been widely studied in coordinated analysis of integrated electricity-gas system (IEGS). However, as a crucial coupling unit, the boost characteristics of the EDC change dynamically with gas state, which may lead to unstable operation mode and then affect safe operating of IEGS. Meanwhile, its nonlinear model greatly increases the difficulty of analysis. This paper proposes a reduced-order transfer function model that considers EDCs for an accurate and efficient dynamic analysis of the IEGS. Firstly, a general two-port model in the Laplace-domain is derived to jointly analyze the pipeline and EDCs dynamic characteristics. The model based on transfer function, explicitly gives the relation between the pressures and flows state at ports. On this basis, to concisely analyze state variations of crucial nodes, the multiple cascaded pipelines and compressors are aggregated and to form an equivalent model. Meanwhile, to reduce the computational burden of the high-order Laplacian "s" in the aggregated process, a reduced-order method is developed based on Jordan continued-fraction expansion by preserving the main gas dynamic feature. Then the analytical expression of state fluctuation can be conveniently derived to analyze the underlying impact and interaction between power system and gas system. Finally, case studies are conducted to prove the effectiveness of proposed model and reduction method.