Active Power Control of Grid-connected Permanent Magnet Synchronous Generator-based Wind Turbines in the Presence of Voltage Sags

This paper deals with the issue of active power control of power electronic converters and permanent magnet synchronous generator (PMSG)-based wind turbine (WT) during both balanced and unbalanced voltage sags. The paper first analyzes the adverse effects of voltage sags on WT systems and then proposes a new control strategy. The strategy consists of (i) a vector current control, which utilizes the feed-forward of the negative-sequence voltage (VCCF) to eliminate the effect of negative-sequence components during unbalanced voltage sags; and (ii) a power compensation factor control for the VCCF to maintain the balanced power flow from the WT to the grid irrespective of voltage sag. The latter also maintains the WT system's output currents within their safe limits to avoid potential damage to electronic components in the inverter. Unlike conventional control strategies, the proposed scheme allows the WT system to use optimally sized converters without the need of large DC link capacitors and crowbars. The effectiveness of the control strategy has been validated experimentally on a physical WT testing platform.