Control and sizing of a hybrid battery and compressed air energy storage system

Abstract

—This paper discusses the sizing and control of a hybrid energy storage system comprising a battery and a compressed air energy storage (CAES) system. The CAES system is connected to the load through a boost converter that controls the air motor’s speed to achieve maximum power point tracking (MPPT). A bidirectional converter is used to connect a battery to the load and maintain the output voltage constant. The air motor and battery sizes are estimated for a typical house in the Southern region of the UK. The battery is sized to buffer load fluctuations. All system models have been simulated using MATLAB/Simulink. Two scenarios are considered: a CAES only system controlled in constant voltage mode and a hybrid system comprising CAES with an MPPT controller and a battery with a voltage controller. The results demonstrate that the power rate of air motor is estimated properly by considering the difference between the generated power and demand power. The power difference called energy deficit is used to size the battery. The performance of CAES system is improved by hybridizing with a battery; the system maintains constant voltage when the CAES operates at maximum power point (MPP). The air motor in hybrid system controlled in MPPT mode has approximately 47% greater efficiency than that of air motor controlled in voltage mode.

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