Enhanced dynamic support strategies of grid-forming-PMSG based on DC-voltagesynchronization: Frequency and Q support perspective

• The enhanced dynamic support strategies of grid-forming PMSG are suggested from perspective: frequency and reactive power. • The inertia synchronization and autonomous voltage support mechanism of grid-forming PMSG are analyzed. • The frequency and voltage support abilities of grid-forming PMSG to power grid are verified. The DC-Voltage Synchronization based Grid-Forming PMSG has voltage source characteristics, e.g. frequency and reactive power support function, however, the support capability is limited, and the regulation potential is not fully utilized. This paper suggests the enhanced dynamic support strategies of DC-voltage synchronization-based grid-forming PMSG from perspective: frequency and reactive power support. To this end, firstly, the inertia synchronization and autonomous voltage support mechanism of grid-forming wind turbine (WT) with DC capacitor voltage synchronization are analyzed. Secondly, the fast frequency support (FFS) and voltage support method for DC-voltage synchronization-based grid-forming PMSG are proposed with additional control loops. With the help of rotor motion equation and power flow equation, the influence characteristics of FFS of DC-voltage synchronization-based grid-forming PMSG on frequency stability and reactive power regulation strategy on transient voltage stability are revealed. Then, the small signal model of MSC and GSC is constructed, and the change trend of root trajectory is observed with the help of state space model, and the boundary of the proposed strategy parameters is determined. Finally, based on PSCAD/EMTDC, the frequency and voltage support abilities of DC-voltage synchronization-based grid-forming PMSG to power grid are verified. Simulations indicate that the suggested additional frequency support loop and voltage support loop could effectively increase dynamic performance of DC-voltage synchronization-based grid-forming PMSG.