Analytical Expression of Short Circuit Current for Virtual Synchronous Generator with Improved Low Voltage Ride Through Control Strategy

This paper proposes the analytical expression of short circuit current for VSG with the improve low voltage ride through (LVRT) control strategy, which considered both the power angle stabilization of system and the short circuit overcurrent limitation for VSG at the same time. First, the improved active power control is put forward to maintain the power angle stability during LVRT process. Then, the actions of freezing the reactive power loop and reducing the internal potential voltage reference value make VSG acting like the voltage source whose internal potential is lower than normal operation during LVRT process and the transient component of the short circuit current is limited by introducing the virtual impedance. Secondly, the analytical expression is deduced to calculate the short circuit current of VSG on the basis of improve LVRT. Finally, the effectiveness of the proposed improved LVRT control strategy and the accuracy of the analytical expression are verified by the simulation results.