Improvement of transient stability in inverter-based AC microgrid via adaptive virtual inertia

Unlike centralized synchronous generator (SG) in conventional power system, distributed micro-sources are parallel connected to neighbors by inverters, which are less-inertia. To improve the transient stability, inverter-based distributed generators (DG) can draw an analogy between the storage and rotor rotational kinetic energy of SG in inertia function. Instead of emulating a fixed virtual inertia, this study proposes adaptive virtual inertia to alleviate the frequency response. In the transient process, a large inertia is implemented when the frequency will deviate from the normal value, and a low inertia is adopted when it's necessary to recover the frequency. The proposed method can enhance the anti-interference and over-load capacity, so that frequency stability is strengthened. Lyapunov stability analysis is utilized to prove the convergence. Simulation results are presented to verify the effectiveness of the method.