A Novel Application of Flywheel System to Enhance Fault-Ride-Through of the Microgrids

Abstract:
This paper proposes a new control method for Flywheel Energy Storage System (FESS) to guarantee a Fault-Ride-Through (FRT) capability of the sensitive microgrids like big data centres. The proposed method has been developed towards a twofold aim: regulating constant common DC-bus voltage, during serious voltage dips caused by the grid-side electrical faults and also keeping a constant charge current during normal operation of the grid. The proposed FESS is coupled with Permanent Magnet Synchronous Machine (PMSM). The speed sensorless Direct Torque Control (DTC) technique has been developed for PMSM control and the Extended Kalman Filter (EKF) is used to estimate the rotor position and consequently the rotor speed. The main contributions of the overall control method are: (i) the decoupled disturbance control at discharge mode copes with sudden load change disturbances; (ii) the DTC provides fast and precise torque response; (iii) the real time speed estimation by the EKF increases the speed and the accuracy of the overall control system; (iv) the proposed FESS can be easily replaced by the Battery Energy Storage System (BESS). The proposed system and the corresponding control method are verified in MATLAB/Simulink environment. The simulation results confirm the effectiveness of the proposed control method.