Electromechanical modeling of advanced adiabatic compressed air energy storage system compressed charging unit: Incorporating compressor dynamical performance under variable operating conditions

Abstract

The large capacity and independence of fossil fuels make advanced-adiabatic compressed air energy storage (AA-CAES) a promising technology for supporting the integration of volatile renewable energy resources. Current AA-CAES models mainly focus on planning level problems such as efficiency improvement. The electromechanical dynamics of AA-CAES system underpin controller design and stability analysis, which is the foundation of power system operation, but received less attention, because the intricate and nonlinear interactions between the pneumatic and mechanical operations of the compressor, occurring over milliseconds to seconds, make the modeling problem highly complicated to maintain the simplicity to facilitate the design of the control system while describing complex dynamic behavior. This paper proposes an electromechanical transient model of the charging unit of AA-CAES, considering compressor dynamical performance under variable operating conditions. Based on the conservation of mass, momentum and angular momentum, the compressor dynamics are characterized by a nonlinear ordinary differential equations (ODEs), which achieve a proper balance between accuracy and complexity. The model parameters can be calibrated using measured data of real plants or the existing models in the literature. A simulation module for the charging process is developed in the Matlab/Simulink platform. The proposed transient model can capture the surge instability, which is characterized by a limit cycle at a primary frequency of 7 Hz. The model also elucidates the transient dynamics of driving torque, inlet guide vanes (IGVs) and throttle valve adjustments. By accounting for mechanical-pneumatic coupling, it demonstrates how each control action affects all state variables on a millisecond-to-second timescale.