Impact of converter control parameters on the high-frequency resonance stability of a wind-farm connected to an ac grid

Paper in proceeding, 2019

The transient stability of a wind-farm connected to an ac grid depends on the control settings of the involved converters, the grid resonances and the system's operating conditions. This paper focuses on investigating the impact of converter control algorithms on possible high-frequency resonance interactions that could endanger the overall stability of these kinds of systems. Mainly, two control strategies namely the conventional cascade control structure, consisting of an inner current-control loop and various outer-loop controls, and the immediate voltage control structure, which does not include a current-control loop, are compared. The impact of control parameters for both methods will be investigated as well. For this purpose, the ac-side input admittance of a wind-turbine converter is derived for the two control strategies and passivity-based frequency-domain analysis is used to assess their impact on system stability. Finally, the analytical findings are verified through detailed time-domain simulations and recommendations to increase system stability are given accordingly.