Algorithm for Virtual Synchronous Machine Phase Resynchronization

In this paper, the idea of operating parallel inverters to mimic the dynamic stability of a synchronous generator (SG) is investigated when the inertia and damping constants are differed. These inverters are virtual synchronous machines (VSM) due to the replication of the inertial dynamics inherent to the SGs. Instead of using a conventional Phase-Lock Loop (PLL) in order to synchronize distributed generation (DG) to the grid frequency, the swing equation inherent to SG dynamics implemented. Parallel VSM controlled inverters can have behaviors based on the constants of their individual swing equation. This can cause the phase angles to differ beyond IEEE synchronization limits. The proposed algorithm is implemented to correct the phase angle and return parallel VSMs to acceptable operating ranges. Simulation results are performed in PSCAD-EMTDC simulation environment.