Robust DC-Link Voltage Control and Discrete-Time Sensorless Control for High-Speed Flywheel Energy Storage System

This paper proposes a DC-link voltage controller based on fast super-twisting sliding mode control (ST-SMC) algorithm with linear extended state observer (LESO) and a full-order Luenberger observer based on direct discrete PMSM model for high speed flywheel energy storage system (FESS). The mathematical model of flywheel and the dynamic equation of DC-link during discharge are described. On this basis, a DC-link controller combining fast ST-SMC and LESO is proposed. The traditional PI, fast ST-SMC and the proposed algorithm for DC-link are compared in many aspects. For the high speed sensorless control of FESS, the direct discrete complex vector PMSM model is derived firstly. Then the Luenberger observer considering the digital delay in controller is obtained. In addition, the proposed full-order Luenberger observer is compared with the traditional Luenberger based on first-order Euler. Finally, the proposed control strategies in this paper are verified by simulation results.