Modeling and simulation of flywheel energy storage system with IPMSM for voltage sags in distributed power network

Flywheel energy storage has fast charge and discharge speed, and it is capable of discharge huge power in a very short time. So it has become a wise choice to solve power quality problems. This paper describes a Dynamic Voltage Restorer (DVR) using flywheel energy storage (FES) to protect the critical load from voltage sags in distribution network. The flywheel unit is composed of high strength steel rotor and interior permanent magnet synchronous motor, resulting in higher energy density and lower fabrication cost. A control strategy of the DVR system is given in terms of the special features of FES, including the detection of voltage sags, charge/discharge control scheme of FES and compensation method. The charge/discharge control of FES based on vector control is discussed in detail, which realizes the energy flow among distribute network, FES and critical loads through controlling the DC bus voltage. The mathematical model of DVR is built in MATLAB/SIMULINK. Simulation results show that the control strategy of DVR with FES can accurately compensate the voltage sags with flywheel´s kinetic energy and the critical load is fully protected.