Twin-Screw Expander – Asynchronous Generator System for Compressed Air Energy Storage

The paper presents the automation control system of an expander – generator system intended for a compressed air energy storage installation, whose purpose is to generate electric power and supply it into the grid. The twin-screw compressor and expander, driven by and respectively driving asynchronous machines are a well-established solution, with certain advantages, but not lacking drawbacks. The asynchronous induction machines are a robust, efficient and reliable solution, especially for the expander-generator system. The electric machine is started up as a motor, subsequently driven above its synchronous speed of 1500 rpm by the expander, into which air is being released from a reservoir. The paper addresses the tests carried out 5 years after the first commissioning, marking the end of warranty and maturity period. The article provides the operation sequences, as well as useful insights for improving the solution.