Improving the wind energy conversion system dynamics during fault ride through: UPFC versus STATCOM

There is a continuously growing demand for wind power generation capacity. This situation forces the revision of the grid codes requirements, to remain connected during grid faults, i.e., to ride through the faults, and contribute to system stability during fault condition. In a typical fault condition, the voltage at the Point of Common Coupling (PCC) drops below 80% immediately and the rotor speed of induction generators becomes unstable. In this paper, STATCOM and UPFC are used to improving the low voltage ride- through (LVRT) of wind energy conversion system (WECS) and to damp the rotor speed oscillations of induction generator under fault conditions. Furthermore, the performances of these two equipments are compared with each other. STATCOM can only recover voltage after fault clearing at the terminals of the wind energy conversion system (WECS), while controlling the UPFC as a virtual inductor can lead to increase the voltage at the WECS terminals during the fault clearing. The simulation results show that the UPFC is better than STATCOM in improving the LVRT and rotor stability of the WECS. Also, the simulation results show that UPFC can improve the voltage at the PCC in the fault period, with the voltage at the PCC easily recovering to 1pu, simultaneously. STATCOM can recover the voltage at the PCC only after the fault clearing with a high risk of decreasing the PCC voltage to zero during the fault.