Numerical investigation of dynamic characteristics for expansion power generation system of liquefied air energy storage. (1st July 2021)

• Record Type: Journal Article
• Authors: Cui, Shuangshuang; Lu, Chang; Shi, Xingping; Du, Dongmei; He, Qing; Liu, Wenyi
• Is Part Of: Energy. Volume 226(2021)
• Publication Date: 2021-07-01
• Subjects: Liquefied air energy storage -- Expansion power generation system -- Operating conditions -- Dynamic characteristics -- Primary frequency regulation; Power resources -- Periodicals; Power (Mechanics) -- Periodicals; Energy consumption -- Periodicals; 333.7905
• DOI: 10.1016/j.energy.2021.120372
• Languages: English
• ISSNs: 0360-5442

Abstract

Abstract: Liquefied air energy storage (LAES), as a type of compressed air energy storage, has comprehensive advantages. It is suitable for various situations regarding electric energy storage, such as generation, transmission, and user-side applications. It is necessary to learn the operating characteristics of LAES for safe, stable, and controllable operations. In this study, a dynamic model of a 12.5 MW LAES system is established and used to simulate various operating conditions in the expansion phase. The results show that the startup period and rotating speed overshoot of the expander affect each other during the startup process. This can be balanced using a segmented startup scheme, so that the rotating speed overshoot can be controlled within a permissible safe range while shortening the startup period as much as possible. When the segmented startup scheme is "9000 rpm/min–3000 rpm/min, " the startup time is shortest, at 145 s. A ±0.03 Hz dead zone for frequency regulation is considered in the application of the LAES system to the primary frequency regulation of power grid to avoid frequent regulation of the control system, and the primary frequency regulation process is controlled to be within 20 s, meeting the requirements of the power grid. As the action of the emergency closing valve of the protection system in the process of power generation is triggered by the off-grid of the expansion generator owing to an unexpected event, the delay time of the valve action must be controlled to remain within the permissible safe range. This ensures that the expansion generator is safe, and avoids the rotor over-speed caused by the delay of the valve action. The dynamic model and its simulation results can be used to support operation control strategies for LAES systems for primary frequency regulation. Highlights: The dynamic model of expansion power generation system was established. The dynamic characteristics in expansion phase under typical operating conditions were obtained. The influence regular pattern of the speed disturbance on the stabilization time were obtained. The effects of starting mode and valve delay time on dynamic characteristics were discussed.