A comparative study of three different sensorless vector control strategies for a Flywheel Energy Storage System

The aim of this paper is to ensure the sensorless control of an inertial storage system associated to an isolated Hybrid Energy Production Unit (HEPU). The Flywheel Energy Storage System (FESS) is used as energy buffers in order to store or retrieve energy into a stand-alone load. A comparative study of three different techniques based on a sensorless vector-controlled induction motor (IM) driving a flywheel are presented. First, a speed estimation algorithm based on model reference adaptive system (MRAS) theory is proposed. Then, a model reference adaptive speed observers is introduced in this paper with an accurate stability study. This observer strategy is then ameliorated with a new reduced adaptive speed observer. The observer parameters are adapted during flux weakening in order to obtain close tracking of the flywheel speed. The accuracy of the presented models is confirmed by simulation results.