Zhou Linyuan

Low voltage ride-through of wind farms using STATCOM combined with series dynamic breaking resistor

Wind farms are confronted with increasing demands for power quality and fail-safe operation at grid fault. State-of-art techniques applied to meet low voltage ride-through (LVRT) requirements for fix speed wind farms are blade pitching and dynamic reactive power compensation. Besides, breaking resistor and energy storage unit is also helpful to LVRT performance. However, these approaches have their own limitations. A hybrid of STATCOM and series dynamic breaking resistor (SDBR) to realize LVRT performance is proposed in this paper. Utilization of STATCOM overcomes the drawback of SDBR while the SDBR greatly reduces STATCOM rating. Comparisons of the proposed system and some other systems were presented and validated by SABER with a representative model. Simulation results indicate that good LVRT performance can be achieved with low rating of STATCOM. It is also shown that the combination shares the electrical stress of the three phases during unbalance fault.

Improved DC-link voltage control of PMSG WECS based on feedback linearization under grid faults

This paper proposes a DC-link voltage control method for the permanent magnet synchronous generator (PMSG) wind power system with a full-rated back-to-back converter, to improve the dc-link voltage dynamic response under normal operation and grid faults conditions. The dc-link voltage is controlled by the motor-side converter, while the grid-side converter is responsible for the maximum power point tracking. Considering the system nonlinear characteristic, a dc-link voltage controller is designed based on the feedback linearization theory. With this control scheme, the dc-link voltage responses much faster than other control structures. It can suppress the dc-link voltage fluctuation with the wind speed varying and prevent the voltage from rising too high under grid faults. The validity of the control algorithm has been verified by simulation with Matlab/Simulink, and the results show a better dc-link dynamic response with the proposed control scheme.