Dynamic modeling and efficiency analysis of the scroll expander generator system for compressed air energy storage

Reliable and accurate models are urgently needed for research on the control strategies to promote the energy conversion efficiency in compress air energy storage (CAES) system. This paper mainly studies expansion and power generation, which is called the scroll expander generator system with the permanent magnet synchronous generator (PMSG) using the rectifier and buck circuit. Considering influence of air leakage, the scroll expander model is established based on the change of chambers volume, air mass and pressure. A steady model of generator is described with the duty ratio of buck chopper and speed. The control strategies including valve and Buck chopper controller are adopted to quickly track the optimized speed and keep the load voltage constant. The experiment and simulation study validated the model and proved that the proposed control strategies can operate effectively on the variable working conditions. Experiment results point out that the optimized working speed is corresponding with the minimum air consumed power, instead of the maximum efficiency of scroll expander.