Dynamic resonance sensitivity analysis in wind farms

Unlike conventional power systems, where resonance frequencies are mainly determined by passive impedances, wind farms present a more complex situation, where the control systems of the power electronic converters introduce also active impedances. This paper presents an approach to find the resonance frequencies of wind farms by considering both active and passive impedances and to identify which bus of the wind farm has more contribution to resonance frequencies. In the approach, a wind farm is introduced as a Multi-Input Multi-Output (MIMO) dynamic system and the bus Participation Factors (PFs) are calculated by critical eigenvalue sensitivity analysis versus the entries of the MIMO matrix. The PF analysis locates the most exciting bus of the resonances, where can be the best location to install the passive or active filters to reduce the harmonic resonance problems. Time-domain simulation results in PSCAD software for a 400-MW wind farm shows that the presented analytical approach is able to find the critical bus for electrical resonance problems.