Small‐disturbance stability of a weakly grid‐connected wind farm with multiple PMSGs dominated by the DC‐link voltage dynamics

Abstract

This study investigates the model-free assessment of small-disturbance stability determined by the DC-link voltage dynamics in a weakly grid-connected wind farm with M permanent magnet synchronous generators (PMSGs). A reduced-order model of the PMSG wind farm is established, which is the approximate representation of the wind farm dominated by the DC-link voltage dynamics. Based on the reduced-order model, limit of small-disturbance stability of the PMSG wind farm determined by the DC-link voltage dynamics is derived. Calculation of derived stability limit does not need to have the parametric model and can be used to approximately assess the small-disturbance stability of the PMSG wind farm. Hence, the assessment made by using the derived stability limit is model-free and useful in practice when it is usually difficult to establish the parametric model of the wind farm. In addition, the derived stability limit clearly indicates and explains that when the grid connection weakens or/and the number of PMSGs increases, the DC-link voltage dynamics are more likely to cause the instability of the PMSG wind farm. In the study, an example AC grid with a grid-connected PMSG wind farm is presented to demonstrate and evaluate the model-free assessment of small-disturbance stability of the wind farm.