Detecting safe operational regimes of synchronous motor-generator pair for wind integration: A non-linear perspective

In this article, the stability of a synchronous motor generator pair (SMGP) used for improving the inertia of grid-connected renewable energy systems is investigated. The useful operational regime for different sets of system parameters is identified, such as electromagnetic torque, damping co-efficient, and inertia by employing bifurcation analysis to detect stability boundaries. For the first time, the existence of bi-stable regimes for the SMGP with non-linear stability analysis is revealed. The authors' analysis unravels the possibility of the system getting transited to unsafe operation even when the system is in the linearly stable region. The existence of the bistable regime indicates the possibility of the system becoming unstable even when the eigenvalues are in the left half plane. The authors also identify globally stable and globally unstable regimes in the parameter space. The safe operating range of inertia and damping co-efficient values helps in the design of a suitable MGP set that is robust to frequency deviations, even with a low inertia source. With the recommended values of electromagnetic torque, the authors' analysis provides a safe operational regime for power generation from renewable energy sources.