Speed Strategy on High-Pressure Compressor for the Charging Process of Advanced Adiabatic Compressed Air Energy Storage During Dynamic Shutdown

Advanced adiabatic compressed air energy storage (AA-CAES) starts and shuts down frequently. The default operation of the high-pressure compressor (HP) connected to the cavern is to reduce the speed of the inverter motor during shutdown. Whether or not the default speed strategy is safe has yet to be focused on. To this end, a detailed charging process comprising three series of centrifugal compressors with intercoolers was constructed within the framework of unisimdesign. The safety measures were meticulously considered by integrating antisurge circuits, vent valves, and check valves. Proportional–integral (PI) controllers were allocated to the primary component to govern the shutdown procedure. The speed strategy of the HP inverter motor during the load shedding stage is the focus of research. Six speed strategies, including decreasing speed, constant speed, and increasing speed, were discussed, respectively. The discussion focused on changes made to air injection, inlet mass flow of the HP, inlet and outlet pressure of both the middle-pressure compressor (MP) and HP, and energy efficiency. The study found that implementing the minimum allowable speed for the inverter motor speed (IMS) and increasing speed during the load shedding stage can cause fluctuations in the air injection. As IMS increases at the end of the load shedding stage, the pressure anomalies at the MP outlet and the HP inlet weaken, and the shutdown process's energy efficiency improves. The HP inlet flow fluctuations caused by various strategies were within an acceptable range. This study reveals that there is a mutual influence between components in the charging process of AA-CAES. An appropriate speed strategy for the HP inverter motor can mitigate the operational hazards. The results of this study can provide guidance for similar AA-CAES shutdowns.