Open-Loop Modal Resonance to Cause Sub/Super-synchronous Oscillations in a Power System with Grid-Connected Wind Farms

In this chapter, the open-loop modal resonance to cause the sub/super-synchronous oscillation in a power system without the series-compensated transmission line is introduced. Firstly, the open-loop modal resonance between two DFIGs and between a DFIG and the torsional dynamics of a SG is demonstrated in a power system without the series-compensated transmission line. The analysis of open-loop modal resonance is based on a one-input two-output closed-loop interconnected model. The theory of open-loop modal resonance introduced in the previous chapter is applied for the analysis. Secondly, the open-loop modal resonance of a grid-connected wind farm with multiple PMSGs is studied. For the study, a two-input two-output (TITO) closed-loop interconnected model is established. The theory of open-loop modal resonance based on the TITO closed-loop interconnected model is introduced. Finally, the open-loop modal resonance in a power system with multiple grid-connected wind farms is introduced. The analysis of open-loop modal resonance is based on a multi-input multi-output (MIMO) closed-loop interconnected model. Thus, the theory of open-loop modal resonance is established for this general case and can be applied to any complex power system with multiple grid-connected wind farms.